Showing papers in "Cancer Research in 2005"
TL;DR: It is shown that, compared with normal breast tissue, miRNAs are also aberrantly expressed in human breast cancer, and the overall miRNA expression could clearly separate normal versus cancer tissues, with the most significantly deregulated mi RNAs being mir-125b, mir-145, mir -21, and mir-155.
Abstract: MicroRNAs (miRNAs) are a class of small noncoding RNAs that control gene expression by targeting mRNAs and triggering either translation repression or RNA degradation Their aberrant expression may be involved in human diseases, including cancer Indeed, miRNA aberrant expression has been previously found in human chronic lymphocytic leukemias, where miRNA signatures were associated with specific clinicobiological features Here, we show that, compared with normal breast tissue, miRNAs are also aberrantly expressed in human breast cancer The overall miRNA expression could clearly separate normal versus cancer tissues, with the most significantly deregulated miRNAs being mir-125b, mir-145, mir-21, and mir-155 Results were confirmed by microarray and Northern blot analyses We could identify miRNAs whose expression was correlated with specific breast cancer biopathologic features, such as estrogen and progesterone receptor expression, tumor stage, vascular invasion, or proliferation index
4,076 citations
TL;DR: The identification and characterization of a cancer stem cell population from human prostate tumors, which possess a significant capacity for self-renewal and are able to regenerate the phenotypically mixed populations of nonclonogenic cells, which express differentiated cell products.
Abstract: Existing therapies for prostate cancer eradicates the bulk of cells within a tumor. However, most patients go on to develop androgen-independent disease that remains incurable by current treatment strategies. There is now increasing evidence in some malignancies that the tumor cells are organized as a hierarchy originating from rare stem cells that are responsible for maintaining the tumor. We report here the identification and characterization of a cancer stem cell population from human prostate tumors, which possess a significant capacity for self-renewal. These cells are also able to regenerate the phenotypically mixed populations of nonclonogenic cells, which express differentiated cell products, such as androgen receptor and prostatic acid phosphatase. The cancer stem cells have a CD44+/α2β1hi/CD133+ phenotype, and we have exploited these markers to isolate cells from a series of prostate tumors with differing Gleason grade and metastatic states. Approximately 0.1% of cells in any tumor expressed this phenotype, and there was no correlation between the number of CD44+/α2β1hi/CD133+ cells and tumor grade. The identification of a prostate cancer stem cell provides a powerful tool to investigate the tumorigenic process and to develop therapies targeted to the stem cell.
2,825 citations
TL;DR: It is shown that the highly malignant human brain tumor, glioblastoma, strongly over-expresses a specific miRNA, miR-21, which may contribute to the malignant phenotype by blocking expression of critical apoptosis-related genes.
Abstract: MicroRNAs (miRNAs) are small noncoding RNA molecules that regulate protein expression by targeting the mRNA of protein-coding genes for either cleavage or repression of translation. The roles of miRNAs in lineage determination and proliferation as well as the location of several miRNA genes at sites of translocation breakpoints or deletions has led to the speculation that miRNAs could be important factors in the development or maintenance of the neoplastic state. Here we show that the highly malignant human brain tumor, glioblastoma, strongly overexpresses a specific miRNA, miR-21. Our studies show markedly elevated miR-21 levels in human glioblastoma tumor tissues, early-passage glioblastoma cultures, and in six established glioblastoma cell lines (A172, U87, U373, LN229, LN428, and LN308) compared with nonneoplastic fetal and adult brain tissues and compared with cultured nonneoplastic glial cells. Knockdown of miR-21 in cultured glioblastoma cells triggers activation of caspases and leads to increased apoptotic cell death. Our data suggest that aberrantly expressed miR-21 may contribute to the malignant phenotype by blocking expression of critical apoptosis-related genes.
2,588 citations
TL;DR: Long-term cultures of breast tumorigenic cells with stem/progenitor cell properties represent a suitable in vitro model to study breast cancer-initiating cells and to develop therapeutic strategies aimed at eradicating the tumorigenics subpopulation within breast cancer.
Abstract: Breast cancer-initiating cells have been recently identified in breast carcinoma as CD44+/CD24(-/low) cells, which exclusively retain tumorigenic activity and display stem cell-like properties. However, at present, direct evidence that breast cancer-initiating cells can be propagated in vitro is still lacking. We report here the isolation and in vitro propagation of breast cancer-initiating cells from three breast cancer lesions and from an established breast carcinoma cell line. Our breast carcinoma-derived cultures encompassed undifferentiated cells capable of self-renewal, extensive proliferation as clonal nonadherent spherical clusters, and differentiation along different mammary epithelial lineages (ductal and myoepithelial). Interestingly, cultured cells were CD44+/CD24- and Cx43-, overexpressed neoangiogenic and cytoprotective factors, expressed the putative stem cell marker Oct-4, and gave rise to new tumors when as few as 10(3) cells were injected into the mammary fat pad of SCID mice. Long-term cultures of breast tumorigenic cells with stem/progenitor cell properties represent a suitable in vitro model to study breast cancer-initiating cells and to develop therapeutic strategies aimed at eradicating the tumorigenic subpopulation within breast cancer.
1,807 citations
TL;DR: Findings clearly suggest that marked overexpression of the miR-17-92 cluster with occasional gene amplification may play a role in the development of lung cancers, especially in their most aggressive form, small-cell lung cancer, and that the C13orf25 gene may well be serving as a vehicle in this regard.
Abstract: MicroRNAs (miRNAs) are small noncoding RNAs, thought to be involved in physiologic and developmental processes by negatively regulating expression of target genes. We have previously reported frequent down-regulation of the let-7 miRNA family in lung cancers and, in the present study, assessed alteration in a panel of 19 lung cancer cell lines. As a result, we found for the first time that the miR-17-92 cluster, which comprises seven miRNAs and resides in intron 3 of the C13orf25 gene at 13q31.3, is markedly overexpressed in lung cancers, especially with small-cell lung cancer histology. Southern blot analysis revealed the presence of increased gene copy numbers of the miRNA cluster in a fraction of lung cancer cell lines with overexpression. In addition, we were able to show predominant localization of C13orf25 transcripts within the nucleus and introduction of the expression construct of the miR-17-92 cluster, but not the putative open reading frame of C13orf25, enhancing lung cancer cell growth. These findings clearly suggest that marked overexpression of the miR-17-92 cluster with occasional gene amplification may play a role in the development of lung cancers, especially in their most aggressive form, small-cell lung cancer, and that the C13orf25 gene may well be serving as a vehicle in this regard.
1,607 citations
TL;DR: It is proposed that melanomas can contain a subpopulation of stem cells that contribute to heterogeneity and tumorigenesis, and targeting this population may lead to effective treatments for melanomas.
Abstract: Recent studies suggest that cancer can arise from a cancer stem cell (CSC), a tumor-initiating cell that has properties similar to those of stem cells. CSCs have been identified in several malignancies, including those of blood, brain, and breast. Here, we test whether stem cell-like populations exist in human melanomas. In approximately 20% of the metastatic melanomas cultured in growth medium suitable for human embryonic stem cells, we found a subpopulation of cells propagating as nonadherent spheres, whereas in standard medium, adherent monolayer cultures were established. Individual cells from melanoma spheres (melanoma spheroid cells) could differentiate under appropriate conditions into multiple cell lineages, such as melanocytic, adipocytic, osteocytic, and chondrocytic lineages, which recapitulates the plasticity of neural crest stem cells. Multipotent melanoma spheroid cells persisted after serial cloning in vitro and transplantation in vivo, indicating their ability to self-renew. Furthermore, they were more tumorigenic than adherent cells when grafted to mice. We identified similar multipotent spheroid cells in melanoma cell lines and found that the stem cell population was enriched in a CD20+ fraction of melanoma cells. Based on these findings, we propose that melanomas can contain a subpopulation of stem cells that contribute to heterogeneity and tumorigenesis. Targeting this population may lead to effective treatments for melanomas.
1,270 citations
TL;DR: It is reported that AMN107 and BMS-354825 are 20-fold and 325-fold more potent than imatinib against cells expressing wild-type Bcr-Abl and that similar improvements are maintained for allImatinib-resistant mutants tested, with the exception of T315I.
Abstract: Imatinib, a Bcr-Abl tyrosine kinase inhibitor, is a highly effective therapy for patients with chronic myelogenous leukemia (CML). Despite durable responses in most chronic phase patients, relapses have been observed and are much more prevalent in patients with advanced disease. The most common mechanism of acquired imatinib resistance has been traced to Bcr-Abl kinase domain mutations with decreased imatinib sensitivity. Thus, alternate Bcr-Abl kinase inhibitors that have activity against imatinib-resistant mutants would be useful for patients who relapse on imatinib therapy. Two such Bcr-Abl inhibitors are currently being evaluated in clinical trials: the improved potency, selective Abl inhibitor AMN107 and the highly potent dual Src/Abl inhibitor BMS-354825. In the current article, we compared imatinib, AMN107, and BMS-354825 in cellular and biochemical assays against a panel of 16 kinase domain mutants representing >90% of clinical isolates. We report that AMN107 and BMS-354825 are 20-fold and 325-fold more potent than imatinib against cells expressing wild-type Bcr-Abl and that similar improvements are maintained for all imatinib-resistant mutants tested, with the exception of T315I. Thus, both inhibitors hold promise for treating imatinib-refractory CML.
1,068 citations
Journal Article•
TL;DR: It is reported here that constitutive or inducible expression of B7-H1, a B7 family molecule widely expressed by cancers, confers resistance to therapeutic anti-CD137 antibody in mice with established tumors and implicate new approaches for immunotherapy of human cancers.
Abstract: Contemporary approaches for vaccination and immunotherapy are often capable of eliciting strong T-cell responses against tumor antigens. However, such responses are not parallel to clinical tumor regression. The development of evasion mechanisms within tumor microenvironment may be responsible for poor therapeutic responses. We report here that constitutive or inducible expression of B7-H1, a B7 family molecule widely expressed by cancers, confers resistance to therapeutic anti-CD137 antibody in mice with established tumors. The resistance is accompanied with failure of antigen-specific CD8+ CTLs to destroy tumor cells without impairment of CTL function. Blockade of B7-H1 or PD-1 by specific monoclonal antibodies could reverse this resistance and profoundly enhance therapeutic efficacy. Our findings support that B7-H1/PD-1 forms a molecular shield to prevent destruction by CTLs and implicate new approaches for immunotherapy of human cancers.
1,044 citations
TL;DR: This is the first report of spontaneous transformation of human adult stem cells, supporting the hypothesis of cancer stem cell origin, and indicates the importance of biosafety studies of mesenchymal stem cell biology to efficiently exploit their full clinical therapeutic potential.
Abstract: Human adult stem cells are being evaluated widely for various therapeutic approaches. Several recent clinical trials have reported their safety, showing them to be highly resistant to transformation. The clear similarities between stem cell and cancer stem cell genetic programs are nonetheless the basis of a recent proposal that some cancer stem cells could derive from human adult stem cells. Here we show that although they can be managed safely during the standard ex vivo expansion period (6-8 weeks), human mesenchymal stem cells can undergo spontaneous transformation following long-term in vitro culture (4-5 months). This is the first report of spontaneous transformation of human adult stem cells, supporting the hypothesis of cancer stem cell origin. Our findings indicate the importance of biosafety studies of mesenchymal stem cell biology to efficiently exploit their full clinical therapeutic potential.
1,039 citations
TL;DR: It is concluded that hMSCs can integrate into human gliomas after intravascular or local delivery, that this engraftment may be mediated by growth factors, and that this tropism of hMSC for human gl iomas can be exploited to therapeutic advantage.
Abstract: The poor survival of patients with human malignant gliomas relates partly to the inability to deliver therapeutic agents to the tumor. Because it has been suggested that circulating bone marrow-derived stem cells can be recruited into solid organs in response to tissue stresses, we hypothesized that human bone marrow-derived mesenchymal stem cells (hMSC) may have a tropism for brain tumors and thus could be used as delivery vehicles for glioma therapy. To test this, we isolated hMSCs from bone marrow of normal volunteers, fluorescently labeled the cells, and injected them into the carotid artery of mice bearing human glioma intracranial xenografts (U87, U251, and LN229). hMSCs were seen exclusively within the brain tumors regardless of whether the cells were injected into the ipsilateral or contralateral carotid artery. In contrast, intracarotid injections of fibroblasts or U87 glioma cells resulted in widespread distribution of delivered cells without tumor specificity. To assess the potential of hMSCs to track human gliomas, we injected hMSCs directly into the cerebral hemisphere opposite an established human glioma and showed that the hMSCs were capable of migrating into the xenograft in vivo. Likewise, in vitro Matrigel invasion assays showed that conditioned medium from gliomas, but not from fibroblasts or astrocytes, supported the migration of hMSCs and that platelet-derived growth factor, epidermal growth factor, or stromal cell-derived factor-1alpha, but not basic fibroblast growth factor or vascular endothelial growth factor, enhanced hMSC migration. To test the potential of hMSCs to deliver a therapeutic agent, hMSCs were engineered to release IFN-beta (hMSC-IFN-beta). In vitro coculture and Transwell experiments showed the efficacy of hMSC-IFN-beta against human gliomas. In vivo experiments showed that treatment of human U87 intracranial glioma xenografts with hMSC-IFN-beta significantly increase animal survival compared with controls (P < 0.05). We conclude that hMSCs can integrate into human gliomas after intravascular or local delivery, that this engraftment may be mediated by growth factors, and that this tropism of hMSCs for human gliomas can be exploited to therapeutic advantage.
1,032 citations
TL;DR: The results suggest that the side population is enriched with tumorigenic stem-like cancer cells,ABCG2 expression identifies mainly fast-cycling tumor progenitors, and the ABCG2- population contains primitive stem- like cancer cells.
Abstract: Recently, several human cancers including leukemia and breast and brain tumors were found to contain stem-like cancer cells called cancer stem cells (CSC). Most of these CSCs were identified using markers that identify putative normal stem cells. In some cases, stem-like cancer cells were identified using the flow cytometry-based side population technique. In this study, we first show that approximately 30% of cultured human cancer cells and xenograft tumors examined ( approximately 30 in total) possess a detectable side population. Purified side population cells from two cell lines (U373 glioma and MCF7 breast cancer) and a xenograft prostate tumor (LAPC-9) are more tumorigenic than the corresponding non-side population cells. These side population cells also possess some intrinsic stem cell properties as they generate non-side population cells in vivo, can be further transplanted, and preferentially express some "stemness" genes, including Notch-1 and beta-catenin. Because the side population phenotype is mainly mediated by ABCG2, an ATP-binding cassette half-transporter associated with multidrug resistance, we subsequently studied ABCG2+ and ABCG2- cancer cells with respect to their tumorigenicity in vivo. Although side population cells show increased ABCG2 mRNA expression relative to the non-side population cells and all cancer cells and xenograft tumors examined express ABCG2 in a small fraction (0.5-3%) of the cells, highly purified ABCG2+ cancer cells, surprisingly, have very similar tumorigenicity to the ABCG2- cancer cells. Mechanistic studies indicate that ABCG2 expression is associated with proliferation and ABCG2+ cancer cells can generate ABCG2- cells. However, ABCG2- cancer cells can also generate ABCG2+ cells. Furthermore, the ABCG2- cancer cells form more and larger clones in the long-term clonal analyses and the ABCG2- population preferentially expresses several "stemness" genes. Taken together, our results suggest that (a) the side population is enriched with tumorigenic stem-like cancer cells, (b) ABCG2 expression identifies mainly fast-cycling tumor progenitors, and (c) the ABCG2- population contains primitive stem-like cancer cells.
TL;DR: Targeting methotrexate increased its antitumor activity and markedly decreased its toxicity, allowing therapeutic responses not possible with a free drug, and modified PAMAM dendritic polymers were employed as carriers.
Abstract: Prior studies suggested that nanoparticle drug delivery might improve the therapeutic response to anticancer drugs and allow the simultaneous monitoring of drug uptake by tumors. We employed modified PAMAM dendritic polymers <5 nm in diameter as carriers. Acetylated dendrimers were conjugated to folic acid as a targeting agent and then coupled to either methotrexate or tritium and either fluorescein or 6-carboxytetramethylrhodamine. These conjugates were injected i.v. into immunodeficient mice bearing human KB tumors that overexpress the folic acid receptor. In contrast to nontargeted polymer, folate-conjugated nanoparticles concentrated in the tumor and liver tissue over 4 days after administration. The tumor tissue localization of the folate-targeted polymer could be attenuated by prior i.v. injection of free folic acid. Confocal microscopy confirmed the internalization of the drug conjugates into the tumor cells. Targeting methotrexate increased its antitumor activity and markedly decreased its toxicity, allowing therapeutic responses not possible with a free drug.
TL;DR: Mutation of PIK3CA is frequent, occurs early in carcinoma development, and has prognostic and therapeutic implications and the association between ERBB2 overexpression and Pik3CA mutation implies that more than one input activating the PI3K/AKT pathway may be required to overcome intact PTEN.
Abstract: Deregulation of the phosphatidylinositol 3-kinase (PI3K) pathway either through loss of PTEN or mutation of the catalytic subunit alpha of PI3K (PIK3CA) occurs frequently in human cancer. We identified PIK3CA mutations in 26% of 342 human breast tumor samples and cell lines at about equal frequency in tumor stages I to IV. To investigate the relationship between PTEN and PIK3CA, we generated a cohort of tumors that had lost PTEN expression and compared it with a matched control set that had retained PTEN. A highly significant association between PIK3CA mutations and retention of PTEN protein expression was observed. In addition, PIK3CA mutations were associated with expression of estrogen and progesterone receptors (ER/PR), lymph node metastasis, and ERBB2 overexpression. The fact that PIK3CA mutations and PTEN loss are nearly mutually exclusive implies that deregulated phosphatidylinositol-3,4,5-triphosphate (PIP(3)) is critical for tumorigenesis in a significant fraction of breast cancers and that loss of PIP(3) homeostasis by abrogation of either PIK3CA or PTEN relieves selective pressure for targeting of the other gene. The correlation of PIK3CA mutation to ER/PR-positive tumors and PTEN loss to ER/PR-negative tumors argues for disparate branches of tumor evolution. Furthermore, the association between ERBB2 overexpression and PIK3CA mutation implies that more than one input activating the PI3K/AKT pathway may be required to overcome intact PTEN. Thus, mutation of PIK3CA is frequent, occurs early in carcinoma development, and has prognostic and therapeutic implications.
TL;DR: Results showed, for the first time, the existence of suppressor myeloid cells producing arginase in human cancer patients, and supports the concept that blocking arginases may be an important step in the success of immunotherapy.
Abstract: Myeloid suppressor cells with high arginase activity are found in tumors and spleen of mice with colon and lung cancer. These cells, described as macrophages or immature dendritic cells, deplete arginine and impair T cell proliferation and cytokine production. Although arginase activity has been described in cancer patients, it is thought to originate from tumor cells metabolizing arginine to ornithine needed to sustain rapid cell proliferation. The goal of this study was to determine whether myeloid suppressor cells producing high arginase existed in renal cell carcinoma patients. Peripheral blood mononuclear cells from 123 patients with metastatic renal cell carcinoma, prior to treatment, were found to have a significantly increased arginase activity. These patients had a markedly decreased cytokine production and expressed low levels of T cell receptor CD3zeta chain. Cell separation studies showed that the increased arginase activity was limited to a specific subset of CD11b+, CD14-, CD15+ cells with a polymorphonuclear granulocyte morphology and markers, instead of macrophages or dendritic cells described in mouse models. Furthermore, these patients had low levels of arginine and high levels of ornithine in plasma. Depletion of the CD11b+, CD14- myeloid suppressor cells reestablished T cell proliferation and CD3zeta chain expression. These results showed, for the first time, the existence of suppressor myeloid cells producing arginase in human cancer patients. In addition, it supports the concept that blocking arginase may be an important step in the success of immunotherapy.
TL;DR: This review focuses on transcriptional repression of p21 by cellular and viral factors, and delve in detail into its possible biological implications and its role in cancer.
Abstract: The cyclin-dependent kinase inhibitor p21WAF1/CIP1 is a major player in cell cycle control and it is mainly regulated at the transcriptional level. Whereas induction of p21 predominantly leads to cell cycle arrest, repression of p21 may have a variety of outcomes depending on the context. In this review, we concentrate on transcriptional repression of p21 by cellular and viral factors, and delve in detail into its possible biological implications and its role in cancer. It seems that the major mode of p21 transcriptional repression by negative regulators is the interference with positive transcription factors without direct binding to the p21 promoter. Specifically, the negative factors may either inhibit binding of positive regulators to the promoter or hinder their transcriptional activity. The ability of p21 to inhibit proliferation may contribute to its tumor suppressor function. Because of this, it is not surprising that a number of oncogenes repress p21 to promote cell growth and tumorigenesis. However, p21 is also an inhibitor of apoptosis and p21 repression may also have an anticancer effect. For example, c-Myc and chemical p21 inhibitors, which repress p21, sensitize tumor cells to apoptosis by anticancer drugs. Further identification of factors that repress p21 is likely to contribute to the better understanding of its role in cancer.
Journal Article•
TL;DR: This study reports that inhibition of glycolysis severely depletes ATP in cancer cells, especially in clones of cancer cells with mitochondrial respiration defects, and leads to rapid dephosphorylation of the gly colysis-apoptosis integrating molecule BAD at Ser(112), relocalization of BAX to mitochondria, and massive cell death.
Abstract: Cancer cells generally exhibit increased glycolysis for ATP generation (the Warburg effect) due in part to mitochondrial respiration injury and hypoxia, which are frequently associated with resistance to therapeutic agents. Here, we report that inhibition of glycolysis severely depletes ATP in cancer cells, especially in clones of cancer cells with mitochondrial respiration defects, and leads to rapid dephosphorylation of the glycolysis-apoptosis integrating molecule BAD at Ser 112 , relocalization of BAX to mitochondria, and massive cell death. Importantly, inhibition of glycolysis effectively kills colon cancer cells and lymphoma cells in a hypoxic environment in which the cancer cells exhibit high glycolytic activity and decreased sensitivity to common anticancer agents. Depletion of ATP by glycolytic inhibition also potently induced apoptosis in multidrug-resistant cells, suggesting that deprivation of cellular energy supply may be an effective way to overcome multidrug resistance. Our study shows a promising therapeutic strategy to effectively kill cancer cells and overcome drug resistance. Because the Warburg effect and hypoxia are frequently seen in human cancers, these findings may have broad clinical implications. (Cancer Res 2005; 65(2): 613-21)
TL;DR: This study provides a mechanistic basis for enhancing mTOR-targeted cancer therapy by combining an mTOR inhibitor with a PI3K or Akt inhibitor and shows that rapamycin combined with LY294002 exhibited enhanced inhibitory effects on the growth and colony formation of cancer cells.
Abstract: The mammalian target of rapamycin (mTOR) has emerged as an important cancer therapeutic target. Rapamycin and its derivatives that specifically inhibit mTOR are now being actively evaluated in clinical trials. Recently, the inhibition of mTOR has been shown to reverse Akt-dependent prostate intraepithelial neoplasia. However, many cancer cells are resistant to rapamycin and its derivatives. The mechanism of this resistance remains a subject of major therapeutic significance. Here we report that the inhibition of mTOR by rapamycin triggers the activation of two survival signaling pathways that may contribute to drug resistance. Treatment of human lung cancer cells with rapamycin suppressed the phosphorylation of p70S6 kinase and 4E-BP1, indicating an inhibition of mTOR signaling. Paradoxically, rapamycin also concurrently increased the phosphorylation of both Akt and eIF4E. The rapamycin-induced phosphorylation of Akt and eIF4E was suppressed by the phosphatidylinositol-3 kinase (PI3K) inhibitor LY294002, suggesting the requirement of PI3K in this process. The activated Akt and eIF4E seem to attenuate rapamycin's growth-inhibitory effects, serving as a negative feedback mechanism. In support of this model, rapamycin combined with LY294002 exhibited enhanced inhibitory effects on the growth and colony formation of cancer cells. Thus, our study provides a mechanistic basis for enhancing mTOR-targeted cancer therapy by combining an mTOR inhibitor with a PI3K or Akt inhibitor.
TL;DR: The data identify novel prognostic markers for breast cancer, suggest a mechanism whereby Notch is activated in aggressive breast tumors, and suggest a signaling pathway activated in poor prognosis breast cancer which can be therapeutically targeted.
Abstract: Aberrant activation of Notch receptors has been shown to cause mammary tumors in mice. We therefore used in situ hybridization to analyze expression of Notch ligands and receptors in human breast cancer. High levels of JAG1 and NOTCH1 were noted in a subset of tumors with poor prognosis pathologic features (P < 0.05). We therefore used tissue microarrays to analyze the expression of these genes in a collection of breast cancers from patients representing a wide spectrum of clinical stages, and from whom associated follow-up survival data was available (n = 184). Patients with tumors expressing high levels of JAG1 or NOTCH1 had a significantly poorer overall survival compared with patients expressing low levels of these genes [5-year survival rate of 42% versus 65% and median survival of 50 versus 83 months, respectively, for JAG1(Hi vs. Lo) (P = 0.01); 49% versus 64% and 53 versus 91 months, respectively, for NOTCH1(Hi vs. Lo) (P = 0.02)]. Moreover, a synergistic effect of high-level JAG1 and high-level NOTCH1 coexpression on overall survival was observed (5-year survival rate of 32% and median survival of 40 months; P = 0.003). These data (a) identify novel prognostic markers for breast cancer, (b) suggest a mechanism whereby Notch is activated in aggressive breast tumors, and (c) may identify a signaling pathway activated in poor prognosis breast cancer which can be therapeutically targeted.
TL;DR: It is shown that macrophages and tumor cells are necessary and sufficient for comigration and invasion into collagen I and that this process involves a paracrine loop.
Abstract: Previous studies have shown that macrophages and tumor cells are comigratory in mammary tumors and that these cell types are mutually dependent for invasion. Here we show that macrophages and tumor cells are necessary and sufficient for comigration and invasion into collagen I and that this process involves a paracrine loop. Macrophages express epidermal growth factor (EGF), which promotes the formation of elongated protrusions and cell invasion by carcinoma cells. Colony stimulating factor 1 (CSF-1) produced by carcinoma cells promotes the expression of EGF by macrophages. In addition, EGF promotes the expression of CSF-1 by carcinoma cells thereby generating a positive feedback loop. Disruption of this loop by blockade of either EGF receptor or CSF-1 receptor signaling is sufficient to inhibit both macrophage and tumor cell migration and invasion.
TL;DR: It is concluded that the BRAF V600E mutation in microsatellite-stable colon cancer is associated with a significantly poorer survival in stages 2 to 4 colon cancer but has no effect on the excellent prognosis of micros satellite-unstable tumors.
Abstract: The BRAF V600E mutation has been associated with microsatellite instability and the CpG island methylator phenotype (CIMP) in colon cancer. We evaluated a large population-based sample of individuals with colon cancer to determine its relationship to survival and other clinicopathologic variables. The V600E BRAF mutation was seen in 5% (40 of 803) of microsatellite-stable tumors and 51.8% (43 of 83) of microsatellite-unstable tumors. In microsatellite-stable tumors, this mutation was related to poor survival, CIMP high, advanced American Joint Committee on Cancer (AJCC) stage, and family history of colorectal cancer [odds ratio, 4.23; 95% confidence interval (95% CI), 1.65-10.84]. The poor survival was observed in a univariate analysis of 5-year survival (16.7% versus 60.0%; P < 0.01); in an analysis adjusted for age, stage, and tumor site [hazard rate ratio (HRR), 2.97; 95% CI, 2.05-4.32]; in stage-specific, age-adjusted analyses for AJCC stages 2 to 4 (HRR, 4.88, 3.60, and 2.04, respectively); and in Kaplan-Meier survival estimates for AJCC stages 2 to 4 (P < 0.01 for all three stages). Microsatellite-unstable tumors were associated with an excellent 5-year survival whether the V600E mutation was present or absent (76.2% and 75.0%, respectively). We conclude that the BRAF V600E mutation in microsatellite-stable colon cancer is associated with a significantly poorer survival in stages 2 to 4 colon cancer but has no effect on the excellent prognosis of microsatellite-unstable tumors.
TL;DR: It is suggested that stem cell transformation can be the underlying cause of ovarian cancer and continuing stochastic events of stem and progenitor cell transformation define the increasing aggression that is characteristically associated with the disease.
Abstract: The cellular mechanisms underlying the increasing aggressiveness associated with ovarian cancer progression are poorly understood. Coupled with a lack of identification of specific markers that could aid early diagnoses, the disease becomes a major cause of cancer-related mortality in women. Here we present direct evidence that the aggressiveness of human ovarian cancer may be a result of transformation and dysfunction of stem cells in the ovary. A single tumorigenic clone was isolated among a mixed population of cells derived from the ascites of a patient with advanced ovarian cancer. During the course of the study, yet another clone underwent spontaneous transformation in culture, providing a model of disease progression. Both the transformed clones possess stem cell-like characteristics and differentiate to grow in an anchorage-independent manner in vitro as spheroids, although further maturation and tissue-specific differentiation was arrested. Significantly, tumors established from these clones in animal models are similar to those in the human disease in their histopathology and cell architecture. Furthermore, the tumorigenic clones, even on serial transplantation continue to establish tumors, thereby confirming their identity as tumor stem cells. These findings suggest that: (a) stem cell transformation can be the underlying cause of ovarian cancer and (b) continuing stochastic events of stem and progenitor cell transformation define the increasing aggression that is characteristically associated with the disease.
TL;DR: It is shown that HER-2 interacts with insulin-like growth factor-I receptor (IGF-IR) uniquely in these resistant cells and not in the parental trastuzumab-sensitive cells, suggesting that the IGF-IR/HER-2 heterodimer contributes to trastzumab resistance and justify the need for further studies examining this complex as a potential therapeutic target in breast cancers that have progressed while on trastudumab.
Abstract: The majority of breast cancer patients who achieve an initial therapeutic response to the human epidermal growth factor receptor 2 (HER-2)-targeted antibody trastuzumab will show disease progression within 1 year. We previously reported the characterization of SKBR3-derived trastuzumab-resistant pools. In the current study, we show that HER-2 interacts with insulin-like growth factor-I receptor (IGF-IR) uniquely in these resistant cells and not in the parental trastuzumab-sensitive cells. The occurrence of cross talk between IGF-IR and HER-2 exclusively in resistant cells is evidenced by the IGF-I stimulation resulting in increased phosphorylation of HER-2 in resistant cells, but not in parental cells, and by the inhibition of IGF-IR tyrosine kinase activity leading to decreased HER-2 phosphorylation only in resistant cells. In addition, inhibition of IGF-IR tyrosine kinase activity by I-OMe-AG538 increased sensitivity of resistant cells to trastuzumab. HER-2/IGF-IR interaction was disrupted on exposure of resistant cells to the anti-IGF-IR antibody alpha-IR3 and, to a lesser extent, when exposed to the anti-HER-2 antibody pertuzumab. Heterodimer disruption by alpha-IR3 dramatically restored sensitivity to trastuzumab and resistant cells showed a slightly increased sensitivity to pertuzumab versus parental cells. Neither alpha-IR3 nor pertuzumab decreased HER-2 phosphorylation, suggesting that additional sources of phosphorylation other than IGF-IR exist when HER-2 and IGF-IR are not physically bound. Our data support a unique interaction between HER-2 and IGF-IR in trastuzumab-resistant cells such that cross talk occurs between IGF-IR and HER-2. These data suggest that the IGF-IR/HER-2 heterodimer contributes to trastuzumab resistance and justify the need for further studies examining this complex as a potential therapeutic target in breast cancers that have progressed while on trastuzumab.
TL;DR: Improvements in signal-to-noise ratios and the use of an optimized reference make CNAG a useful tool for high-resolution detection of copy number alterations which can help in the understanding of the pathogenesis of cancers and other diseases as well as in exploring the complexities of the human genome.
Abstract: We have developed a robust algorithm for copy number analysis of the human genome using high-density oligonucleotide microarrays containing 116,204 single-nucleotide polymorphisms. The advantages of this algorithm include the improvement of signal-to-noise (S/N) ratios and the use of an optimized reference. The raw S/N ratios were improved by accounting for the length and GC content of the PCR products using quadratic regressions. The use of constitutional DNA, when available, gives the lowest SD values (0.16 ± 0.03) and also enables allele-based copy number detection in cancer genomes, which can unmask otherwise concealed allelic imbalances. In the absence of constitutional DNA, optimized selection of multiple normal references with the highest S/N ratios, in combination with the data regressions, dramatically improves SD values from 0.67 ± 0.12 to 0.18 ± 0.03. These improvements allow for highly reliable comparison of data across different experimental conditions, detection of allele-based copy number changes, and more accurate estimations of the range and magnitude of copy number aberrations. This algorithm has been implemented in a software package called Copy Number Analyzer for Affymetrix GeneChip Mapping 100K arrays (CNAG). Overall, these enhancements make CNAG a useful tool for high-resolution detection of copy number alterations which can help in the understanding of the pathogenesis of cancers and other diseases as well as in exploring the complexities of the human genome.
TL;DR: The data obtained with AZD2171 are consistent with potent inhibition of VEGF signaling, angiogenesis, neovascular survival, and tumor growth.
Abstract: Inhibition of vascular endothelial growth factor-A (VEGF) signaling is a promising therapeutic approach that aims to stabilize the progression of solid malignancies by abrogating tumor-induced angiogenesis. This may be accomplished by inhibiting the kinase activity of VEGF receptor-2 (KDR), which has a key role in mediating VEGF-induced responses. The novel indole-ether quinazoline AZD2171 is a highly potent (IC50
TL;DR: The feasibility of siRNA incorporated into the neutral liposome 1,2-dioleoyl-sn-glycero-3-phosphatidylcholine (DOPC) for efficient in vivo siRNA delivery and DOPC-encapsulated siRNA targeting the oncoprotein EphA2 was highly effective in reducing in vivo Eph a2 expression 48 hours after a single dose are shown.
Abstract: Inducing destruction of specific mRNA using small interfering RNA (siRNA) is a powerful tool in analysis of protein function, but its use as a therapeutic modality has been limited by inefficient or impractical delivery systems. We have used siRNA incorporated into the neutral liposome 1,2-dioleoyl-sn-glycero-3-phosphatidylcholine (DOPC) for efficient in vivo siRNA delivery. In nude mice bearing i.p. ovarian tumors, nonsilencing siRNA tagged with the fluorochrome Alexa 555 was encapsulated into DOPC liposomes and shown to be taken up by the tumor as well as many major organs. Furthermore, DOPC-encapsulated siRNA targeting the oncoprotein EphA2 was highly effective in reducing in vivo EphA2 expression 48 hours after a single dose as measured by both Western blot and immunohistochemistry. Therapy experiments in an orthotopic mouse model of ovarian cancer were initiated 1 week after injection of either HeyA8 or SKOV3ip1 cell lines. Three weeks of treatment with EphA2-targeting siRNA-DOPC (150 microg/kg twice weekly) reduced tumor growth when compared with a nonsilencing siRNA (SKOV3ip1: 0.35 versus 0.70 g; P = 0.020; HeyA8: 0.98 versus 1.51 g; P = 0.16). When EphA2-targeting siRNA-DOPC was combined with paclitaxel, tumor growth was dramatically reduced compared with treatment with paclitaxel and a nonsilencing siRNA (SKOV3ip1: 0.04 versus 0.22 g; P < 0.001; HeyA8: 0.21 versus 0.84 g; P = 0.0027). These studies show the feasibility of siRNA as a clinically applicable therapeutic modality.
TL;DR: A multisubunit protein complex termed Microprocessor is identified that is necessary and sufficient for processing miRNA precursor RNAs and considers recent findings that link miRNA perturbation to cancer.
Abstract: MicroRNAs (miRNA) are a recently discovered family of short non-protein-coding RNAs that negatively regulate gene expression. Recent studies of miRNAs highlight a requirement for cell viability. Posttranscriptional silencing of target genes by miRNAs occurs either by targeting specific cleavage of homologous mRNAs, or by targeting specific inhibition of protein synthesis. We recently identified a multisubunit protein complex termed Microprocessor that is necessary and sufficient for processing miRNA precursor RNAs. Microprocessor contains Drosha, an RNase III endonuclease, and DGCR8, a gene deleted in DiGeorge syndrome. We consider recent findings that link miRNA perturbation to cancer.
TL;DR: A key clinical turning point in carcinoma progression is the establishment by emigrant cells of secondary growth sites (i.e., metastasis) as discussed by the authors, which leads to dysregulation of the normal control of cell number.
Abstract: Carcinogenesis involves the accretion of unprogrammed genetic and epigenetic changes, which lead to dysregulation of the normal control of cell number. But a key clinical turning point in carcinoma progression is the establishment by emigrant cells of secondary growth sites (i.e., metastasis). The
TL;DR: The remarkable similarities of mutations in EGFR and HER2 genes involving tumor type and subtype, mutation type, gene location, and specific patient subpopulations targeted are unprecedented and suggest similar etiologic factors.
Abstract: Mutations in the epidermal growth factor receptor gene (EGFR) in lung cancers predict for sensitivity to EGFR kinase inhibitors. HER2 (also known as NEU, EGFR2, or ERBB2) is a member of the EGFR family of receptor tyrosine kinases and plays important roles in the pathogenesis of certain human cancers, and mutations have recently been reported in lung cancers. We sequenced the tyrosine kinase domain of HER2 in 671 primary non-small cell lung cancers (NSCLC), 80 NSCLC cell lines, and 55 SCLCs and other neuroendocrine lung tumors as well as 85 other epithelial cancers (breast, bladder, prostate, and colorectal cancers) and compared the mutational status with clinicopathologic features and the presence of EGFR or KRAS mutations. HER2 mutations were present in 1.6% (11 of 671) of NSCLC and were absent in other types of cancers. Only one adenocarcinoma cell line (NCI-H1781) had a mutation. All HER2 mutations were in-frame insertions in exon 20 and target the identical corresponding region as did EGFR insertions. HER2 mutations were significantly more frequent in never smokers (3.2%, 8 of 248; P=0.02) and adenocarcinoma histology (2.8%, 11 of 394; P=0.003). In 394 adenocarcinoma cases, HER2 mutations preferentially targeted Oriental ethnicity (3.9%) compared with other ethnicities (0.7%), female gender (3.6%) compared with male gender (1.9%) and never smokers (4.1%) compared with smokers (1.4%). Mutations in EGFR, HER2, and KRAS genes were never present together in individual tumors and cell lines. The remarkable similarities of mutations in EGFR and HER2 genes involving tumor type and subtype, mutation type, gene location, and specific patient subpopulations targeted are unprecedented and suggest similar etiologic factors. EGFR, HER2, and KRAS mutations are mutually exclusive, suggesting different pathways to lung cancer in smokers and never smokers.
TL;DR: It is shown that wild-type EGFR-containing human NSCLC lines show a range of sensitivities to EGFR inhibition dependent on the degree to which they have undergone an epithelial to mesenchymal transition (EMT), suggesting that EMT may be a general biological switch rendering non-small cell lung tumors sensitive or insensitive to EG FR inhibition.
Abstract: Treatment of second- and third-line patients with non–small-cell lung carcinoma (NSCLC) with the epidermal growth factor receptor (EGFR) kinase inhibitor erlotinib significantly increased survival relative to placebo. Whereas patient tumors with EGFR mutations have shown responses to EGFR inhibitors, an exclusive role for mutations in patient survival benefit from EGFR inhibition is unclear. Here we show that wild-type EGFR–containing human NSCLC lines grown both in culture and as xenografts show a range of sensitivities to EGFR inhibition dependent on the degree to which they have undergone an epithelial to mesenchymal transition (EMT). NSCLC lines which express the epithelial cell junction protein E-cadherin showed greater sensitivity to EGFR inhibition in vitro and in xenografts. In contrast, NSCLC lines having undergone EMT, expressing vimentin and/or fibronectin, were insensitive to the growth inhibitory effects of EGFR kinase inhibition in vitro and in xenografts. The differential sensitivity of NSCLC cells with epithelial or mesenchymal phenotypes to EGFR inhibition did not correlate with cell cycle status in vitro or with xenograft growth rates in vivo , or with total EGFR protein levels. Cells sensitive to EGFR inhibition, with an epithelial cell phenotype, did exhibit increased phosphorylation of EGFR and ErbB3 and a marked increase in total ErbB3. The loss of E-cadherin and deregulation of β-catenin associated with EMT have been shown to correlate with poor prognosis in multiple solid tumor types. These data suggest that EMT may be a general biological switch rendering non–small cell lung tumors sensitive or insensitive to EGFR inhibition.
Journal Article•
TL;DR: Safety pharmacology studies with bevacizumab in cynomolgus monkeys showed that this agent is generally well tolerated with no unexpected adverse events, implying that the most effective use of anti-VEGF therapy is in combination with chemotherapy.
Abstract: Preclinical models have examined the pharmacologic and pharmacodynamic activities of an anti-vascular endothelial growth factor (VEGF) humanized, monoclonal antibody, bevacizumab, and/or its murine equivalent A4.6.1. These studies found that single-agent therapy with bevacizumab/A4.6.1 resulted in tumor growth inhibition of 20 different human tumor cell lines (13 tumor types) implanted into nude mice irrespective of the route of administration or tumor location. Several of these studies also observed significant inhibition of tumor metastases. Various studies have examined the feasibility of combining anti-VEGF therapy with cytotoxic or biological agents. Combining bevacizumab/A4.6.1 with doxorubicin, topotecan, paclitaxel, docetaxel, or radiotherapy resulted in additive or synergistic tumor growth inhibition. Changes in vascular functions were frequently reported, including decreased vessel diameter, density, and permeability in response to treatment. A reduction in interstitial fluid pressure was also observed. In some studies, these improvements resulted in an increase in intratumoral uptake of chemotherapy, implying that the most effective use of anti-VEGF therapy is in combination with chemotherapy. Alternatively, combination treatment with radiation increased tumor oxygenation and tumor growth inhibition. Interestingly, anti-VEGF therapy has also been reported to reduce the development of ascites in ovarian mouse models. Finally, safety pharmacology studies with bevacizumab in cynomolgus monkeys showed that this agent is generally well tolerated with no unexpected adverse events.