Showing papers on "Tyrosine-kinase inhibitor published in 2004"
TL;DR: It is reported that mutant EGFRs selectively transduce survival signals on which NSCLCs become dependent; inhibition of those signals by gefitinib may contribute to the drug's efficacy.
Abstract: Gefitinib (Iressa, Astra Zeneca Pharmaceuticals) is a tyrosine kinase inhibitor that targets the epidermal growth factor receptor (EGFR) and induces dramatic clinical responses in nonsmall cell lung cancers (NSCLCs) with activating mutations within the EGFR kinase domain. We report that these mutant EGFRs selectively activate Akt and signal transduction and activator of transcription (STAT) signaling pathways, which promote cell survival, but have no effect on extracellular signal-regulated kinase signaling, which induces proliferation. NSCLC cells expressing mutant EGFRs underwent extensive apoptosis after small interfering RNA-mediated knockdown of the mutant EGFR or treatment with pharmacological inhibitors of Akt and STAT signaling and were relatively resistant to apoptosis induced by conventional chemotherapeutic drugs. Thus, mutant EGFRs selectively transduce survival signals on which NSCLCs become dependent; inhibition of those signals by gefitinib may contribute to the drug's efficacy.
1,640 citations
TL;DR: The slow off-rate ofGW572016 correlates with a prolonged down-regulation of receptor tyrosine phosphorylation in tumor cells and the differences in the off-rates of these drugs and the ability of GW572016 to inhibit ErbB-2 can be explained by the enzyme-inhibitor structures.
Abstract: GW572016 (Lapatinib) is a tyrosine kinase inhibitor in clinical development for cancer that is a potent dual inhibitor of epidermal growth factor receptor (EGFR, ErbB-1) and ErbB-2. We determined the crystal structure of EGFR bound to GW572016. The compound is bound to an inactive-like conformation of EGFR that is very different from the active-like structure bound by the selective EGFR inhibitor OSI-774 (Tarceva) described previously. Surprisingly, we found that GW572016 has a very slow off-rate from the purified intracellular domains of EGFR and ErbB-2 compared with OSI-774 and another EGFR selective inhibitor, ZD-1839 (Iressa). Treatment of tumor cells with these inhibitors results in down-regulation of receptor tyrosine phosphorylation. We evaluated the duration of the drug effect after washing away free compound and found that the rate of recovery of receptor phosphorylation in the tumor cells reflected the inhibitor off-rate from the purified intracellular domain. The slow off-rate of GW572016 correlates with a prolonged down-regulation of receptor tyrosine phosphorylation in tumor cells. The differences in the off-rates of these drugs and the ability of GW572016 to inhibit ErbB-2 can be explained by the enzyme-inhibitor structures.
1,062 citations
TL;DR: Differential expression of influx (hOCT1) and efflux (MDR1) transporters may be a critical determinant of intracellular drug levels and, hence, resistance to imatinib.
640 citations
TL;DR: This work provides the first evidence that imatinib is a substrate for BCRP, that it competes with mitoxantrone for drug export, and that B CRP-mediated efflux can be reversed by the fumitremorgin C analog Ko-143.
423 citations
TL;DR: The extrachromosomal (episomal) amplification of ABL1 in 5 of 90 individuals with T-ALL, an aberration that is not detectable by conventional cytogenetics, is described and a previously undescribed mechanism for activation of tyrosine kinases in cancer: the formation of episomes resulting in a fusion between NUP214 and A BL1 is identified.
Abstract: In T-cell acute lymphoblastic leukemia (T-ALL), transcription factors are known to be deregulated by chromosomal translocations, but mutations in protein tyrosine kinases have only rarely been identified. Here we describe the extrachromosomal (episomal) amplification of ABL1 in 5 of 90 (5.6%) individuals with T-ALL, an aberration that is not detectable by conventional cytogenetics. Molecular analyses delineated the amplicon as a 500-kb region from chromosome band 9q34, containing the oncogenes ABL1 and NUP214 (refs. 5,6). We identified a previously undescribed mechanism for activation of tyrosine kinases in cancer: the formation of episomes resulting in a fusion between NUP214 and ABL1. We detected the NUP214-ABL1 transcript in five individuals with the ABL1 amplification, in 5 of 85 (5.8%) additional individuals with T-ALL and in 3 of 22 T-ALL cell lines. The constitutively phosphorylated tyrosine kinase NUP214-ABL1 is sensitive to the tyrosine kinase inhibitor imatinib. The recurrent cryptic NUP214-ABL1 rearrangement is associated with increased HOX expression and deletion of CDKN2A, consistent with a multistep pathogenesis of T-ALL. NUP214-ABL1 expression defines a new subgroup of individuals with T-ALL who could benefit from treatment with imatinib.
423 citations
TL;DR: Combined treatment with distinct EGFR inhibitory agents can augment the potency of EGFR signaling inhibition and this approach suggests potential new strategies to maximize effective target inhibition, which may improve the therapeutic ratio for anti-EGFR-targeted therapies in developing clinical trials.
Abstract: Molecular inhibition of epidermal growth factor receptor (EGFR/HER1) signaling is under active investigation as a promising cancer treatment strategy. We examined the potency of EGFR inhibition achieved by combining anti-EGFR monoclonal antibody and tyrosine kinase inhibitor, which target extracellular and intracellular domains of the receptor, respectively. We specifically studied the combination of cetuximab (Erbitux, C225; ImClone Systems, New York, NY) with either gefitinib (Iressa, ZD1839; AstraZeneca, Macclesfield, UK) or erlotinib (Tarceva, OSI-774; Genentech, South San Francisco, CA) across a variety of human cancer cells. The combination of cetuximab plus gefitinib or erlotinib enhanced growth inhibition over that observed with either agent alone. As measured by immunostaining, inhibition of EGFR phosphorylation with the combination of cetuximab plus gefitinib or erlotinib was augmented over that obtained with single-agent therapy in head and neck (H&N) cancer cell lines. Phosphorylation inhibition of downstream effector molecules [mitogen-activated protein kinase (MAPK) and AKT] also was enhanced in tumor cells treated with the combination of cetuximab plus gefitinib or erlotinib. Flow cytometry and immunoblot analysis demonstrated that treatment of H&N tumor cells with cetuximab in combination with either gefitinib or erlotinib amplified the induction of apoptosis. Following establishment of cetuximab-resistant cell lines, we observed that gefitinib or erlotinib retained the capacity to inhibit growth of lung and H&N tumor cells that were highly resistant to cetuximab. Treatment with gefitinib or erlotinib, but not cetuximab, also could further inhibit the activation of downstream effectors of EGFR signaling in cetuximab-resistant cells, including MAPK and AKT. These data suggest that tyrosine kinase inhibitors may further modulate intracellular signaling that is not fully blocked by extracellular anti-EGFR antibody treatment. Finally, animal studies confirmed that single EGFR inhibitor treatment resulted in partial and transient tumor regression in human lung cancer xenografts. In contrast, more profound tumor regression and regrowth delay were observed in mice treated with the combination of cetuximab and gefitinib or erlotinib. Immunohistochemical staining, which demonstrated significant reduction of the proliferative marker proliferating cell nuclear antigen in mice treated with dual EGFR inhibitors, further supported this in vivo observation. Together, these data suggest that combined treatment with distinct EGFR inhibitory agents can augment the potency of EGFR signaling inhibition. This approach suggests potential new strategies to maximize effective target inhibition, which may improve the therapeutic ratio for anti-EGFR-targeted therapies in developing clinical trials.
402 citations
TL;DR: A phase 2 trial of the FLT3-selective tyrosine kinase inhibitor lestaurtinib (CEP701) used as monotherapy in untreated older patients with acute myeloid leukemia (AML) was conducted in this article.
400 citations
TL;DR: Patients with P-Akt-positive tumors who received gefitinib had a better response rate, disease control rate, and time to progression than patients withP-AKT-negative tumors, suggesting that gefithinib may be most effective in patients with basal Akt activation.
Abstract: Background: Gefitinib, a specific epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor, has activity against approximately 10% of unselected non-small-cell lung cancer (NSCLC) patients. Phosphatidylinositol 3'-kinase (PI3K)/Akt and Ras/Raf/mitogen-activated protein kinase (MAPK), the two main EGFR-signaling pathways, mediate EGFR effects on proliferation and survival. Because activation of these pathways is dependent on the phosphorylation status of the components, we evaluated the association between phosphorylation status of Akt (P-Akt) and MAPK (P-MAPK) and gefitinib activity in patients with advanced NSCLC. Methods: Consecutive patients (n = 106) with NSCLC who had progressed or relapsed on standard therapy received gefitinib (250 mg/day) until disease progression, unacceptable toxicity, or patient refusal. P-Akt and P-MAPK positivity was determined with immunohistochemistry using tumor tissues obtained before any anticancer treatment. Association of P-Akt and time to progression was determined by univariable and multivariable analyses. All statistical tests were two-sided. Results: Of the 103 evaluable patients, 51 (49.5%) had tumors that were positive for P-Akt, and 23 (22.3%) had tumors that were positive for P-MAPK. P-Akt-positivity status was statistically significantly associated with being female (P<.001), with never-smoking history (P =.004), and with bronchioloalveolar carcinoma histology (P =.034). Compared with patients whose tumors were negative for P-Akt, patients whose tumors were positive for P-Akt had a better response rate (26.1% versus 3.9%; P =.003), disease control rate (60.9% versus 23.5%; P<.001), and time to progression (5.5 versus 2.8 months; P =.004). Response rate, disease control rate, and time to progression did not differ according to P-MAPK status. The multivariable analysis showed that P-Akt positivity was associated with a reduced risk of disease progression (hazard ratio = 0.58, 95% confidence interval = 0.35 to 0.94). Conclusions: Patients with P-Akt-positive tumors who received gefitinib had a better response rate, disease control rate, and time to progression than patients with P-Akt-negative tumors, suggesting that gefitinib may be most effective in patients with basal Akt activation.
372 citations
TL;DR: Data indicate that AEE788 has potential as an anticancer agent targeting deregulated tumor cell proliferation as well as angiogenic parameters, and is currently in Phase I clinical trials in oncology.
Abstract: Aberrant epidermal growth factor receptor (EGFR) and ErbB2 expression are associated with advanced disease and poor patient prognosis in many tumor types (breast, lung, ovarian, prostate, glioma, gastric, and squamous carcinoma of head and neck). In addition, a constitutively active EGFR type III deletion mutant has been identified in non-small cell lung cancer, glioblastomas, and breast tumors. Hence, members of the EGFR family are viewed as promising therapeutic targets in the fight against cancer. In a similar vein, vascular endothelial growth factor (VEGF) receptor kinases are also promising targets in terms of an antiangiogenic treatment strategy. AEE788, obtained by optimization of the 7H-pyrrolo[2,3-d]pyrimidine lead scaffold, is a potent combined inhibitor of both epidermal growth factor (EGF) and VEGF receptor tyrosine kinase family members on the isolated enzyme level and in cellular systems. At the enzyme level, AEE788 inhibited EGFR and VEGF receptor tyrosine kinases in the nm range (IC(50)s: EGFR 2 nm, ErbB2 6 nm, KDR 77 nm, and Flt-1 59 nm). In cells, growth factor-induced EGFR and ErbB2 phosphorylation was also efficiently inhibited (IC(50)s: 11 and 220 nm, respectively). AEE788 demonstrated antiproliferative activity against a range of EGFR and ErbB2-overexpressing cell lines (including EGFRvIII-dependent lines) and inhibited the proliferation of epidermal growth factor- and VEGF-stimulated human umbilical vein endothelial cells. These properties, combined with a favorable pharmacokinetic profile, were associated with a potent antitumor activity in a number of animal models of cancer, including tumors that overexpress EGFR and or ErbB2. Oral administration of AEE788 to tumor-bearing mice resulted in high and persistent compound levels in tumor tissue. Moreover, AEE788 efficiently inhibited growth factor-induced EGFR and ErbB2 phosphorylation in tumors for >72 h, a phenomenon correlating with the antitumor efficacy of intermittent treatment schedules. Strikingly, AEE788 also inhibited VEGF-induced angiogenesis in a murine implant model. Antiangiogenic activity was also apparent by measurement of tumor vascular permeability and interstitial leakage space using dynamic contrast enhanced magnetic resonance imaging methodology. Taken together, these data indicate that AEE788 has potential as an anticancer agent targeting deregulated tumor cell proliferation as well as angiogenic parameters. Consequently, AEE788 is currently in Phase I clinical trials in oncology.
343 citations
TL;DR: Functional analyses showed that KIT/T670I is insensitive toImatinib and that T670I mutation, introduced in a receptor responding to imatinib, subverted its sensitivity to the drug.
332 citations
TL;DR: Allelic-specific sequencing data show that this new mutation occurs in the allele that harbors original activation mutation of KIT, which has never been reported before, and is strongly correlated with imatinib resistance.
Abstract: KIT gain of function mutations play an important role in the pathogenesis of gastrointestinal stromal tumors (GISTs). Imatinib is a selective tyrosine kinase inhibitor of ABL, platelet-derived growth factor receptor (PDGFR), and KIT and represents a new paradigm of targeted therapy against GISTs. Here we report for the first time that, after imatinib treatment, an additional specific and novel KIT mutation occurs in GISTs as they develop resistance to the drug. We studied 12 GIST patients with initial near-complete response to imatinib. Seven harbored mutations in KIT exon 11, and 5 harbored mutations in exon 9. Within 31 months, six imatinib-resistant rapidly progressive peritoneal implants (metastatic foci) developed in five patients. Quiescent residual GISTs persisted in seven patients. All six rapidly progressive imatinib-resistant implants from five patients show an identical novel KIT missense mutation, 1982T→C, that resulted in Val654Ala in KIT tyrosine kinase domain 1. This novel mutation has never been reported before, is not present in pre-imatinib or post-imatinib residual quiescent GISTs, and is strongly correlated with imatinib resistance. Allelic-specific sequencing data show that this new mutation occurs in the allele that harbors original activation mutation of KIT .
TL;DR: Long-term treatment of GEO xenografts with selective EGFR inhibitors results in the development of EGFR inhibitor-resistant cancer cells, indicating that inhibition of VEGF signaling has potential as an anticancer strategy, even in tumors that are resistant to EGF inhibitors.
Abstract: Purpose: The epidermal growth factor receptor (EGFR) autocrine signaling pathway is involved in cancer development and progression. EGFR inhibitors such as C225 (cetuximab), a chimeric human-mouse anti-EGFR monoclonal antibody, and ZD1839 (gefitinib), a small molecule EGFR-selective tyrosine kinase inhibitor, are in advanced clinical development. The potential emergence of cancer cell resistance in EGFR-expressing cancers treated with EGFR inhibitors could determine lack of activity of these drugs in some cancer patients. Vascular endothelial growth factor (VEGF) is secreted by cancer cells and plays a key role in the regulation of tumor-induced endothelial cell proliferation and permeability. ZD6474 is a small molecule VEGF flk-1/KDR (VEGFR-2) tyrosine kinase inhibitor that also demonstrates inhibitory activity against EGFR tyrosine kinase. Experimental Design: The antitumor activity of ZD1839, C225, and ZD6474 was tested in athymic mice bearing human GEO colon cancer xenografts. GEO cell lines resistant to EGFR inhibitors were established from GEO xenografts growing in mice treated chronically with ZD1839 or C225. Expression of EGFR was evaluated by flow cytometry. Expression of various proteins involved in intracellular cell signaling was assessed by Western blotting. Tumor growth data were evaluated for statistical significance using the Student’s t test. All P s were two-sided. Results: Although chronic administration of optimal doses of C225 or ZD1839 efficiently blocked GEO tumor growth in the majority of mice, tumors slowly started to grow within 80–90 days, despite continuous treatment. In contrast, continuous treatment of mice bearing established GEO xenografts with ZD6474 resulted in efficient tumor growth inhibition for the entire duration of dosing (up to 150 days). ZD6474 activity was also determined in mice pretreated with ZD1839 or C225. When GEO growth was apparent after 4 weeks of treatment with EGFR inhibitors, mice were either re-treated with EGFR inhibitors or treated with ZD6474. GEO tumor growth was blocked only in mice treated with ZD6474, whereas tumor progression was observed in mice re-treated with C225 or ZD1839. GEO tumors growing during treatment with C225 or with ZD1839 were established as cell lines (GEO-C225-RES and GEO-ZD1839-RES, respectively). Cell membrane-associated EGFR expression was only slightly reduced in these cell lines compared with parental GEO cells. Western blotting revealed no major change in the expression of the EGFR ligand transforming growth factor α of bcl-2, bcl-xL, p53, p27, MDM-2, akt, activated phospho-akt, or mitogen-activated protein kinase. However, both GEO-C225-RES and GEO-ZD1839-RES cells exhibited a 5–10-fold increase in activated phospho-mitogen-activated protein kinase and in the expression of cyclooxygenase-2 and of VEGF compared with GEO cells. GEO-C225-RES and GEO-ZD1839-RES growth as xenografts in nude mice was not significantly affected by treatment with either C225 or ZD1839 but was efficiently inhibited by ZD6474. Conclusions: Long-term treatment of GEO xenografts with selective EGFR inhibitors results in the development of EGFR inhibitor-resistant cancer cells. Growth of EGFR inhibitor-resistant tumors can be inhibited by ZD6474. These data indicate that inhibition of VEGF signaling has potential as an anticancer strategy, even in tumors that are resistant to EGF inhibitors.
TL;DR: Mutational analysis of the c-kit gene in a patient with a previously undescribed variant of mast cell disease revealed a germline mutation within the transmembrane portion of the Kit receptor protein that caused ligand-independent autophosphorylation of Kit, which was inhibited by the tyrosine kinase inhibitor imatinib mesylate.
TL;DR: In primary myeloma cells from t(4;14) patients, CHIR-258 inhibited downstream extracellular signal-regulated kinase (ERK) 1/2 phosphorylation with an associated cytotoxic response, supporting the clinical evaluation of CHir-258 in MM and encouraging the clinical development of FGFR3 inhibitors.
TL;DR: Both shared and complementary mechanisms of action with gefitinib and cetuximab are suggested and support combined EGFR targeting as a clinically exploitable strategy.
Abstract: Purpose: The epidermal growth factor receptor (EGFR) is abnormally activated in cancer and two classes of anti-EGFR agents, monoclonal antibodies and low-molecular-weight tyrosine kinase inhibitors, have shown antitumor activity in patients. Because these two classes of antireceptor agents target the EGFR at different sites, we decided to explore whether the combined administration of gefitinib, a tyrosine kinase inhibitor, and cetuximab, a monoclonal antibody, had superior antitumor activity than either agent given alone. Experimental Design: We studied the effects of the combination of gefitinib and cetuximab in a panel of human cancer cell lines and in an EGFR-dependent human tumor xenograft model (A431). The effects of these two agents on EGFR signaling, proliferation, apoptosis, and vascularization were evaluated. In addition, we analyzed, with cDNA arrays, changes in gene expression profiles induced by both agents. Results: The combined treatment with gefitinib and cetuximab resulted in a synergistic effect on cell proliferation and in superior inhibition of EGFR-dependent signaling and induction of apoptosis. In a series of in vivo experiments, single-agent gefitinib or cetuximab resulted in transient complete tumor remission only at the highest doses. In contrast, suboptimal doses of gefitinib and cetuximab given together resulted in a complete and permanent regression of large tumors. In the combination-treated tumors, there was a superior inhibition of EGFR, mitogen-activated protein kinase, and Akt phosphorylation, as well as greater inhibition of cell proliferation and vascularization and enhanced apoptosis. Using cDNA arrays, we found 59 genes that were coregulated and 45 genes differentially regulated, including genes related to cell proliferation and differentiation, transcription, DNA synthesis and repair, angiogenesis, signaling molecules, cytoskeleton organization, and tumor invasion and metastasis. Conclusions: Our findings suggest both shared and complementary mechanisms of action with gefitinib and cetuximab and support combined EGFR targeting as a clinically exploitable strategy.
Journal Article•
TL;DR: This study is the first to demonstrate that sensitivity to growth inhibition by gefitinib in NSCLC cell lines under basal growth condition is associated with dependence on Akt and ERK1/2 activation in response to EGFR signaling for survival and proliferation and also that drug sensitivity may be related to the extent of EGF-induced down-regulation of cell surface EGFR.
Abstract: Gefitinib (Iressa, ZD1839), a quinazoline tyrosine kinase inhibitor that targets the epidermal growth factor receptor (EGFR), is approved for patients with advanced non-small cell lung cancer (NSCLC) in several countries including Japan. However, the mechanism of drug sensitivity to gefitinib is not fully understood. In this study, we examined the molecular basis of sensitivity to gefitinib using nine human lung cancer cell lines derived from NSCLC. PC9 was the most sensitive to gefitinib of the nine NSCLC cell lines when assayed either by colony formation or MTS assays. The various cell lines expressed different levels of EGFR, HER2, HER3, and HER4, but there was no correlation between levels of EGFR and/or HER2 expression and drug sensitivity. Phosphorylation of EGFR, protein kinase B/AKT (Akt), and extracellular signal-regulated kinase (ERK) 1/2 was inhibited by much lower concentration of gefitinib in PC9 cells than in the other eight cell lines under exponential growing conditions. About 80% of cell surface EGFR in PC-9 was internalized within 10 min, whereas only about 30-50% of the cell surface EGFR was internalized in more drug-resistant cell lines in 15-60 min. The present study is the first to demonstrate that sensitivity to growth inhibition by gefitinib in NSCLC cell lines under basal growth condition is associated with dependence on Akt and ERK1/2 activation in response to EGFR signaling for survival and proliferation and also that drug sensitivity may be related to the extent of EGF-induced down-regulation of cell surface EGFR.
TL;DR: It is concluded that in breast and prostate cancer cells acquired resistance to gefitinib is associated with increased signalling via the IGF-1R pathway, which also plays a role in the invasive capacity of the gefitsinib-resistant phenotype.
Abstract: De novo and acquired resistance to the anti-tumour drug gefitinib (ZD1839; Iressa), a specific epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI) has been reported. We have determined whether signalling through the IGF-I receptor (IGF-1R) pathway plays a role in the gefitinib-acquired resistance phenotype. Continuous exposure of EGFR-positive MCF-7-derived tamoxifen resistant breast cancer cells (TAM-R) to 1 μM gefitinib resulted in a sustained growth inhibition (90%) for 4 months before the surviving cells resumed proliferation. A stable gefitinib-resistant subline (TAM/TKI-R) was established after a further 2 months and this showed no detectable basal phosphorylated EGFR activity. Compared with the parental TAM-R cells, the TAM/ TKI-R cells demonstrated (a) elevated levels of activated IGF-1R, AKT and protein kinase C (PKC)δ, (b) an increased sensitivity to growth inhibition by the IGF-1R TKI AG1024 and (c) an increased migratory capacity that was reduced by AG1024 treatment. Similarly, the EGFR-positive androgen-independent human prostate cancer cell line DU145 was also continuously challenged with 1 μM gefitinib and, although substantial growth inhibition (60%) was seen initially, a gefitinib-resistant variant (DU145/TKI-R) developed after 3 months. Like their breast cancer counterparts, the DU145/TKI-R cells showed increases in the levels of components of the IGF-1R signalling pathway and an elevated sensitivity to growth inhibition by AG1024 compared with the parent DU145 cell line. Additionally, DU145/TKI-R cell migration was also decreased by this inhibitor. We have therefore concluded that in breast and prostate cancer cells acquired resistance to gefitinib is associated with increased signalling via the IGF-1R pathway, which also plays a role in the invasive capacity of the gefitinib-resistant phenotype.
TL;DR: Assessment of biologic correlates in patients with metastatic breast cancer indicates that increased tumor cell apoptosis on the terminal deoxynucleotide transferase-mediated dUTP nick-end labeling assay correlates with clinical response; lapatinib currently is being evaluated in phase II and phase III trials.
Abstract: Dual inhibition of ErbB-1 (EGFR) and ErbB-2 (HER-2) tyrosine kinases has been found to exert greater biologic effects in the inhibition of signaling pathways promoting cancer cell proliferation and survival than inhibition of either receptor alone. The novel dual EGFR/ErbB-2 tyrosine kinase inhibitor lapatinib (GlaxoSmithKline; Research Triangle Park, NC) has been shown to inhibit tumor cell growth in vitro and in xenograft models for a variety of human tumors. Preliminary findings in a phase I study of lapatinib in patients with solid tumors indicate doses up to 1,800 mg per day are well tolerated. No grade 4 toxicities were observed and only two of 43 patients had grade 3 toxicity (diarrhea). Clinical activity of lapatinib was observed in these patients; nine patients with a variety of tumors remained on study for > or =4 months, one with a complete response (head and neck cancer). In a phase IB study in pretreated metastatic cancer patients with disease that could be biopsied, grade 1 or 2 diarrhea and rash were the most common adverse events. Three patients with breast cancer refractory to trastuzumab (Herceptin; Genentech, Inc.; South San Francisco, CA) had partial responses and 12 patients with a variety of tumors had stable disease. Assessment of biologic correlates in these patients indicates that increased tumor cell apoptosis on the terminal deoxynucleotide transferase-mediated dUTP nick-end labeling assay correlates with clinical response. Lapatinib currently is being evaluated in phase II and phase III trials in patients with metastatic breast cancer.
TL;DR: A critical analysis of the current data on tyrosine kinase inhibitors is provided and issues with regards to the design of clinical trials with such agents are discussed.
TL;DR: This work will contrast lessons derived from the development of inhibitors of Abl, c-Kit, HER2/neu (erbB2), and EGFR, highlight successes and limitations in the field, and propose new approaches for clinical development of tyrosine kinase inhibitor therapy.
TL;DR: The data show that, although angiogenesis can be effectively blocked by ZD6474, in vessel-dense organs this may result in sustained tumor progression via co-option, rather than in tumor dormancy, leading to erroneous conclusions about therapeutic efficacy during magnetic resonance imaging follow-up.
Abstract: Purpose: In the brain, tumors may grow without inducing angiogenesis, via co-option of the dense pre-existent capillary bed. The purpose of this study was to investigate how this phenomenon influences the outcome of antiangiogenic therapy. Experimental Design: Mice carrying brain metastases of the human, highly angiogenic melanoma cell line Mel57-VEGF-A were either or not treated with different dosages of ZD6474, a vascular endothelial growth factor (VEGF) receptor 2 tyrosine kinase inhibitor with additional activity against epidermal growth factor receptor. Effect of treatment was evaluated using contrast-enhanced magnetic resonance imaging (CE- MRI) and (immuno)morphologic analysis. Results: Placebo-treated Mel57-VEGF-A brain metastases evoked an angiogenic response and were highlighted in CE-MRI. After treatment with ZD6474 (100 mg/kg), CE-MRI failed to detect tumors in either prevention or therapeutic treatment regimens. However, (immuno)histologic analysis revealed the presence of numerous, small, nonangiogenic lesions. Treatment with 25 mg/kg ZD6474 also resulted in efficient blockade of vessel formation, but it did not fully inhibit vascular leakage, thereby still allowing visualization in CE-MRI scans. Conclusions: Our data show that, although angiogenesis can be effectively blocked by ZD6474, in vessel-dense organs this may result in sustained tumor progression via co-option, rather than in tumor dormancy. Importantly, blocking VEGF-A may result in undetectability of tumors in CE-MRI scans, leading to erroneous conclusions about therapeutic efficacy during magnetic resonance imaging follow-up. The maintenance of VEGF-A-induced vessel leakage in the absence of neovascularization at lower ZD6474 doses may be exploited to improve delivery of chemotherapeutic agents in combined treatment regimens of antiangiogenic and chemotherapeutic compounds.
TL;DR: Elevated VEGF expression contributes to the ability of breast cancer cells to form brain metastases, and targeting endothelial cells with a V EGF-receptor specific tyrosine kinase inhibitor reduced angiogenesis and restricted the growth of the brain metastase.
Abstract: Patients with breast cancer brain metastases cannot be cured and have a poor prognosis, with a median survival time of six months after diagnosis, despite developments in diagnostic and therapeutic modalities. In large part the progress in understanding the biology of breast cancer brain metastasis has been limited by the lack of suitable cell lines and experimental models. The objective of this study was to develop a reliable experimental model to study the pathogenesis of breast cancer brain metastases, using intra-internal carotid artery injection of breast cancer cells into nude mice. Brain metastasis-selected variant cells were recovered after three cycles of injection into the internal carotid artery of nude mice and harvest of brain metastases, resulting in variants termed MDA-231 BR1, -BR2 and -BR3. The metastasis-selected cells had increased potential for experimental brain metastasis and mice injected with these cells had significantly shorter mean survival than mice injected with the original cell line. Brain metastatic lesions of the selected variants contained significantly more CD31-positive blood vessels than metastases of the non-selected cell line. The variants selected from brain metastases released significantly more VEGF-A and IL-8 into culture supernatants than the original cell line, and more VEGF-A RNA when cultured in normoxic conditions. Mice injected with MDA-231 BR3 into the carotid artery were treated with the VEGF-receptor tyrosine kinase inhibitor PTK787/Z 222584. Oral administration of the inhibitor resulted in a significant decrease in brain tumor burden, reduced CD31-positive vessels in the brain lesions and incidence of PCNA positive tumor cells, and increased apoptosis in the tumor, as measured by TUNEL labeling. We conclude that elevated VEGF expression contributes to the ability of breast cancer cells to form brain metastases. Targeting endothelial cells with a VEGF-receptor specific tyrosine kinase inhibitor reduced angiogenesis and restricted the growth of the brain metastases.
TL;DR: Increased Src tyrosine kinase activity represents a potential chemoresistance mechanism and a promising therapeutic target warranting further investigation in gemcitabine-resistant pancreatic adenocarcinoma.
Abstract: Purpose: We tested the hypotheses that Src tyrosine kinase overactivity represents a chemoresistance mechanism and that Src inhibition may enhance gemcitabine cytotoxicity in pancreatic adenocarcinoma cells. Experimental Design: Pancreatic adenocarcinoma cells PANC1, MiaPaCa2, Capan2, BxPC3, and PANC1 GemRes , a stably gemcitabine-resistant subline of PANC1, were exposed to combinations of gemcitabine and Src tyrosine kinase inhibitor 4-amino-5-(4-chlorophenyl)-7-( t -butyl)pyrazolo[3,4- d ]pyrimidine (PP2). Src expression, phosphorylation (Tyr-416), and activity were analyzed by immunoblotting and in vitro kinase assay. Expression of the M2 subunit of ribonucleotide reductase (RRM2), a putative chemoresistance enzyme, was quantified by Northern and Western blot. Cellular proliferation was quantified by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Apoptosis was characterized by YO-PRO-1/propidium iodide staining, fluorometric caspase profiling, and caspase inhibition (Z-Val-Ala-Asp-fluoromethyl ketone). The effects of constitutively active and dominant negative Src were determined. The therapeutic efficacy of PP2 in combination with gemcitabine was tested in nude mice orthotopically xenografted with PANC1 GemRes . Results: Greater gemcitabine resistance was associated with higher Src phosphorylation and activity, both of which were higher in PANC1 GemRes , relative to PANC1; total Src levels were alike. PANC1 GemRes overexpressed RRM2. PP2 enhanced inherent gemcitabine chemosensitivity and attenuated gemcitabine resistance in PANC1 GemRes . Constitutively active Src increased gemcitabine chemoresistance; dominant negative Src impaired gemcitabine chemoresistance. PP2 augmented gemcitabine-induced caspase-mediated apoptosis, suppressed RRM2 expression, and decreased activity of the RRM2-regulating transcription factor E2F1 in PANC1 GemRes . PP2 and gemcitabine in combination substantially decreased tumor growth and inhibited metastasis in vivo . Conclusions: Increased Src tyrosine kinase activity represents a potential chemoresistance mechanism and a promising therapeutic target warranting further investigation in gemcitabine-resistant pancreatic adenocarcinoma.
TL;DR: It is concluded that inhibition of BCR/ABL kinase activity in CML progenitors by imatinib results in a growth factor-dependent compensatory increase in MAPK activity and in only partial inhibition of PI-3 Kinase activity.
TL;DR: It is demonstrated that in vitro exposure of mobilized human CD34+ progenitors to therapeutic concentrations of imatinib mesylate inhibits their differentiation into dendritic cells (DCs) and inhibits the differentiation and function of DCs, which is in part mediated via the nuclear factor kappaB signal transduction pathway.
TL;DR: The results suggest that Src family kinases contribute to GRP-mediated EGFR growth and invasion pathways by facilitating cleavage and release of TGF-α and amphiregulin in HNSCC.
Abstract: Head and neck squamous cell carcinomas (HNSCCs) are characterized by up-regulation of the epidermal growth factor receptor (EGFR). We previously reported that a gastrin-releasing peptide/gastrin-releasing peptide receptor (GRP/GRPR) autocrine growth pathway is activated early in HNSCC carcinogenesis. GRP can induce rapid phosphorylation of EGFR and p42/44 mitogen-activated protein kinase (MAPK) activation in part via extracellular release of transforming growth factor alpha (TGF-alpha) by matrix metalloproteinases (MMPs). It has been reported that Src family kinases are activated by G-protein-coupled receptors (GPCRs), followed by downstream EGFR and MAPK activation. To further elucidate the mechanism of activation of EGFR by GRP in HNSCC, we investigated the role of Src family kinases. Blockade of Src family kinases using an Src-specific tyrosine kinase inhibitor A-419259 decreased GRP-induced EGFR phosphorylation and MAPK activation. GRP also failed to induce MAPK activation in dominant-negative c-Src-transfected HNSCC cells. Invasion and growth assays showed that c-Src was required for GRP-induced proliferation or invasion of HNSCC cells. In addition to TGF-alpha release, GRP induced amphiregulin, but not EGF, secretion into HNSCC cell culture medium, an effect that was blocked by the MMP inhibitor marimastat. TGF-alpha and amphiregulin secretion by GRP stimulation also was inhibited by blockade of Src family kinases. These results suggest that Src family kinases contribute to GRP-mediated EGFR growth and invasion pathways by facilitating cleavage and release of TGF-alpha and amphiregulin in HNSCC.
TL;DR: A small-molecule tyrosine kinase inhibitor, PKC412 was administered to a patient with t(8;13)(p11;q12) and was efficacious in treatment of progressive myeloproliferative disorder with organomegaly and resulted in statistically significant prolongation of survival in the murine model of ZNF198-FGFR1-induced MPD.
Abstract: Human stem cell leukemia-lymphoma syndrome usually presents itself as a myeloproliferative disorder (MPD) that evolves to acute myeloid leukemia and/or lymphoma. The syndrome associated with t(8;13)(p11;q12) results in expression of the ZNF198-fibroblast growth factor receptor (FGFR) 1 fusion tyrosine kinase. Current empirically derived cytotoxic chemotherapy is inadequate for treatment of this disease. We hypothesized that small-molecule inhibitors of the ZNF198-FGFR1 fusion would have therapeutic efficacy. We characterized the transforming activity of ZNF198-FGFR1 in hematopoietic cells in vitro and in vivo. Expression of ZNF198-FGFR1 in primary murine hematopoietic cells caused a myeloproliferative syndrome in mice that recapitulated the human MPD phenotype. Transformation in these assays, and activation of the downstream effector molecules PLC-γ, STAT5, and phosphatidylinositol 3-kinase/AKT, required the proline-rich domains, but not the ZNF domains, of ZNF198. A small-molecule tyrosine kinase inhibitor, PKC412 (N-benzoyl-staurosporine) effectively inhibited ZNF198-FGFR1 tyrosine kinase activity and activation of downstream effector pathways, and inhibited proliferation of ZNF198-FGFR1 transformed Ba/F3 cells. Furthermore, treatment with PKC412 resulted in statistically significant prolongation of survival in the murine model of ZNF198-FGFR1-induced MPD. Based in part on these data, PKC412 was administered to a patient with t(8;13)(p11;q12) and was efficacious in treatment of progressive myeloproliferative disorder with organomegaly. Therefore, PKC412 may be a useful therapy for treatment of human stem cell leukemia-lymphoma syndrome.
TL;DR: Results show that in NSCLC xenograft tumors with similar levels of EGFR expression, the antitumor activity of erlotinib is robust both as monotherapy and in combination with chemotherapies.
Abstract: Our objective was the preclinical assessment of the pharmacokinetics, monotherapy and combined antitumor activity of the epidermal growth factor receptor (HER1/EGFR) tyrosine kinase inhibitor erlotinib in athymic nude mice bearing non-small cell lung cancer (NSCLC) xenograft models. Immunohistochemi
TL;DR: Tyrosine kinase inhibition with imatinib appears to be a novel therapeutic option to retard the development of atherosclerosis, specifically in the context of diabetes.
Abstract: Objective— Diabetes is associated with accelerated atherosclerosis, the major factor contributing to increased mortality and morbidity in the diabetic population. The molecular mechanisms by which diabetes promotes atherosclerosis are not fully understood. Platelet-derived growth factor has been shown to play a major role in the pathology of vascular diseases, but whether it plays a role in atherosclerosis associated with diabetes remains unknown. The aims of this study were to assess whether platelet-derived growth factor–dependent pathways are involved in the development of diabetes-induced atherosclerosis and to determine the effects of platelet-derived growth factor receptor antagonism on this disorder. Methods and Results— Diabetes was induced by injection of streptozotocin in 6-week-old apolipoprotein E knockout mice. Diabetic animals received treatment with a tyrosine kinase inhibitor that inhibits platelet-derived growth factor action, imatinib (STI-571, 10 mg/kg per day), or no treatment for 20 w...
TL;DR: ZD6474 may be a successful adjuvant to clinical radiotherapy, and scheduling of the treatments could be important to ensure optimal efficacy.
Abstract: Purpose: Vascular endothelial growth factor (VEGF) plays a key role in tumor angiogenesis and acts as a radiation survival factor for endothelial cells. ZD6474 ( N -(4-bromo-2-fluorophenyl)-6-methoxy-7-[(1-methylpiperidin-4-yl)methoxy]quinazolin-4-amine) is a potent VEGF receptor 2 (KDR) tyrosine kinase inhibitor (TKI) that has additional activity versus the epidermal growth factor receptor. This study was designed to determine the efficacy of combining ZD6474 and radiotherapy in vivo . Experimental Design: The Calu-6 (non–small-cell lung cancer) tumor model was selected because it was found to be unresponsive to treatment with a selective epidermal growth factor receptor TKI but responds significantly to treatment with selective VEGF receptor TKIs. Tumor-bearing mice received either vehicle or ZD6474 (50 mg/kg, by mouth, once daily) for the duration of the experiment, with or without radiotherapy (3 × 2 Gy, days 1–3). Two combination schedules were examined: ( a ) ZD6474 given before each dose of radiation (concurrent schedule); and ( b ) ZD6474 given 30 minutes after the last dose of radiotherapy (sequential schedule). Results: The growth delay induced using the concurrent schedule was greater than that induced by ZD6474 or radiation treatment alone (22 ± 1 versus 9 ± 1 and 17 ± 2 days, respectively; P = 0.03 versus radiation alone). When administered sequentially, the growth delay was markedly enhanced (36 ± 1 days; P versus radiation alone or the concurrent schedule). Intravenous administration of Hoechst 33342 showed a trend toward reduced tumor perfusion after ZD6474 treatment, and a pairwise comparison ( versus control) was significant after three doses of ZD6474 ( P = 0.05 by one-tailed t test). Thus, impaired reoxygenation between fractions in the concurrent protocol may be the causal basis for the schedule dependency of the radiopotentiation observed. Conclusions: ZD6474 may be a successful adjuvant to clinical radiotherapy, and scheduling of the treatments could be important to ensure optimal efficacy.