Showing papers on "Carcinogenesis published in 2017"
TL;DR: The emerging functions and association of lncRNAs in different types of cancer and their potential implications in cancer diagnosis and therapy are reviewed.
Abstract: In addition to mutations or aberrant expression in the protein-coding genes, mutations and misregulation of noncoding RNAs, in particular long noncoding RNAs (lncRNA), appear to play major roles in cancer. Genome-wide association studies of tumor samples have identified a large number of lncRNAs associated with various types of cancer. Alterations in lncRNA expression and their mutations promote tumorigenesis and metastasis. LncRNAs may exhibit tumor-suppressive and -promoting (oncogenic) functions. Because of their genome-wide expression patterns in a variety of tissues and their tissue-specific expression characteristics, lncRNAs hold strong promise as novel biomarkers and therapeutic targets for cancer. In this article, we have reviewed the emerging functions and association of lncRNAs in different types of cancer and discussed their potential implications in cancer diagnosis and therapy. Cancer Res; 77(15); 3965-81. ©2017 AACR.
1,800 citations
TL;DR: This Review focuses on the main chemokines that are found in the human tumour microenvironment, and elaborate on their patterns of expression, their regulation and their roles in immune cell recruitment and in cancer and stromal cell biology.
Abstract: The tumour microenvironment is the primary location in which tumour cells and the host immune system interact. Different immune cell subsets are recruited into the tumour microenvironment via interactions between chemokines and chemokine receptors, and these populations have distinct effects on tumour progression and therapeutic outcomes. In this Review, we focus on the main chemokines that are found in the human tumour microenvironment; we elaborate on their patterns of expression, their regulation and their roles in immune cell recruitment and in cancer and stromal cell biology, and we consider how they affect cancer immunity and tumorigenesis. We also discuss the potential of targeting chemokine networks, in combination with other immunotherapies, for the treatment of cancer.
1,271 citations
TL;DR: The relationships between SCNA levels, tumor mutations, and cancer hallmarks are examined to find that two hallmarks of cancer, cell proliferation and immune evasion, are predicted by distinct types of aneuploidy that likely act through distinct mechanisms.
Abstract: INTRODUCTION Aneuploidy, also known as somatic copy number alterations (SCNAs), is widespread in human cancers and has been proposed to drive tumorigenesis. The relationship between SCNAs and the characteristic functional features or “hallmarks” of cancer is not well understood. Among these cancer hallmarks is immune evasion, which is accomplished by neoantigen editing, defects in antigen presentation and inhibition of tumor infiltration, and/or cytotoxic activities of immune cells. Whether and how tumor SCNA levels influence immune evasion is of particular interest as this information could potentially be used to improve the efficacy of immune checkpoint blockade, a therapy that has produced durable responses in a subset of cancer patients. RATIONALE Understanding how SCNAs and mutation load affect tumor evolution, and through what mechanisms, is a key objective in cancer research. To explore the relationships between SCNA levels, tumor mutations, and cancer hallmarks, we examined data from 5255 tumor/normal samples representing 12 cancer types from The Cancer Genome Atlas project. We assigned each tumor an SCNA score and looked for correlations with the number and types of tumor mutations. We also compared the gene expression profiles of tumors with high versus low SCNA levels to identify differences in cellular signaling pathways. RESULTS First, we found that, for most tumors, there was a positive correlation between SCNA levels and the total number of mutations. Second, tumors harboring activating oncogenic mutations in the receptor tyrosine kinase–RAS–phosphatidylinositol 3-kinase pathway showed fewer SCNAs, a finding at odds with the hypothesis of oncogene-driven genomic instability. Third, we found that tumors with high levels of SCNAs showed elevated expression of cell cycle and cell proliferation markers (cell cycle signature) and reduced expression of markers for cytotoxic immune cell infiltrates (immune signature). The increased expression level of the cell cycle signature was primarily predicted by focal SCNAs, with a lesser contribution of arm and whole-chromosome SCNAs. In contrast, the lower expression level of the immune signature was primarily predicted by high levels of arm and whole-chromosome SCNAs. SCNA levels were a stronger predictor of markers of cytotoxic immune cell infiltration than tumor mutational load. Finally, through analysis of data from two published clinical trials of immunotherapy in melanoma patients, we found that high SCNA levels in tumors correlated with poorer survival of patients. The combination of the tumor SCNA score and the tumor mutational load was a better predictor of survival after immunotherapy than either biomarker alone. CONCLUSION We found that two hallmarks of cancer, cell proliferation and immune evasion, are predicted by distinct types of aneuploidy that likely act through distinct mechanisms. Proliferation markers mainly correlated with focal SCNAs, implying a mechanism related to the action of specific genes targeted by these SCNAs. Immune evasion markers mainly correlated with arm- and chromosome-level SCNAs, consistent with a mechanism related to general gene dosage imbalance rather than the action of specific genes. A retrospective analysis of melanoma patients treated with immune checkpoint blockade anti–CTLA-4 (cytotoxic T lymphocyte–associated protein 4) therapy revealed that high SCNA levels were associated with a poorer response, suggesting that tumor aneuploidy might be a useful biomarker for predicting which patients are most likely to benefit from this therapy.
918 citations
TL;DR: It is proposed that chromatin and epigenetic aberrations have the potential to confer on cells the full range of oncogenic properties represented in the classic “hallmarks” depiction of cancer, and it is suggested that genetic, environmental, and metabolic factors can make chromatin aberrantly permissive or restrictive.
Abstract: BACKGROUND Chromatin is the essential medium through which transcription factors, signaling pathways, and other cues alter gene activity and cellular phenotypes. It assumes distinct conformations that reinforce regulatory activity or repression at a given locus, and reorganizes in response to appropriate intrinsic and extrinsic signals. The biologist Conrad Waddington famously conceptualized developmental specification as an epigenetic landscape in which differentiating cells proceed downhill along branching canals separated by walls that restrict cell identity. By restricting lineage-specific gene expression and phenotypes, chromatin affects the height of the walls between the canals in this epigenetic landscape. Genetic, metabolic, and environmental stimuli that disrupt chromatin alter cellular states and responses, thereby predisposing individuals to a range of common diseases. Although cancer is typically considered a genetic disease, chromatin and epigenetic aberrations play important roles in tumor potentiation, initiation, and progression. ADVANCES We discuss how the stability of chromatin, or its “resistance” to change, is precisely titrated during normal development, and we propose that deviation from this norm is a major factor in tumorigenesis. We review genetic, environmental, and metabolic stimuli that disrupt the homeostatic balance of chromatin, causing it to become aberrantly restrictive or permissive. Stimuli that increase chromatin resistance may result in a restrictive state that blocks differentiation programs. Stimuli that decrease chromatin resistance may result in a permissive state, which we refer to as epigenetic plasticity. We propose that plasticity allows premalignant or malignant cells to stochastically activate alternate gene regulatory programs and/or undergo nonphysiologic cell fate transitions. Some stochastic changes will be inconsequential “passengers”; others will confer fitness and be selected as “drivers.” As cancer cells divide, acquired epigenetic states may be maintained through cell division by DNA methylation, repressive chromatin, or gene regulatory circuits, giving rise to adaptive epiclones that fuel malignant progression. We highlight specific chromatin aberrations that confer epigenetic restriction or plasticity, and ultimately drive tumor progression via oncogene activation, tumor suppressor silencing, or adaptive cell fate transitions. Aberrations initiated by defined genetic stimuli, such as chromatin regulator gene mutations, are particularly informative regarding mechanism. Examples include gain-of-function mutations of the Polycomb repressor EZH2 that promote chromatin restriction and hinder differentiation, and metabolic enzyme mutations that disrupt the balance of DNA methylation. Changes in DNA methylation resulting from the latter have been tied to tumor suppressor silencing but may also result in stochastic insulator disruption and oncogene activation. We also carefully consider metabolic and environmental stimuli that disrupt chromatin homeostasis in the absence of genetic changes. Examples include links between folate metabolism and methylase activity, environmental factors that promote DNA hypermethylation in gastrointestinal tissues, and potential effects of microenvironmental stress on chromatin regulator expression. Purely epigenetic mechanisms may explain tumors that arise with few or no recurrent mutations, as well as heterogeneous functional phenotypes within tumors that lack genetic explanation. We conclude that chromatin and epigenetic aberrations can confer wide-ranging oncogenic properties and may fulfill all of cancer’s hallmarks. OUTLOOK Initial successes with epigenetic therapies suggest the potential of cancer epigenetics for major clinical impact. Yet realizing this promise will require a clearer understanding of epigenetic mechanisms of tumorigenesis. The identification of increasing numbers of oncogenic epigenetic lesions provides an opportunity to develop and test conceptual and mechanistic models of their functions. Progress will require new technologies for probing chromatin and epigenetic alterations with single-cell precision, as well as experimental models that faithfully recapitulate epigenetic states in tumors. We are optimistic that an improved understanding of epigenetic plasticity and restriction could advance diagnostic strategies for evaluating tumor stage and heterogeneity, and yield new therapeutic strategies for correcting epigenetic lesions or exploiting vulnerabilities of epigenetically altered cells.
856 citations
TL;DR: Different classes of HDAC inhibitors, mechanisms of their actions and novel results of preclinical and clinical studies are summarized, including the combination with other therapeutic modalities are discussed.
Abstract: Carcinogenesis cannot be explained only by genetic alterations, but also involves epigenetic processes. Modification of histones by acetylation plays a key role in epigenetic regulation of gene expression and is controlled by the balance between histone deacetylases (HDAC) and histone acetyltransferases (HAT). HDAC inhibitors induce cancer cell cycle arrest, differentiation and cell death, reduce angiogenesis and modulate immune response. Mechanisms of anticancer effects of HDAC inhibitors are not uniform; they may be different and depend on the cancer type, HDAC inhibitors, doses, etc. HDAC inhibitors seem to be promising anti-cancer drugs particularly in the combination with other anti-cancer drugs and/or radiotherapy. HDAC inhibitors vorinostat, romidepsin and belinostat have been approved for some T-cell lymphoma and panobinostat for multiple myeloma. Other HDAC inhibitors are in clinical trials for the treatment of hematological and solid malignancies. The results of such studies are promising but further larger studies are needed. Because of the reversibility of epigenetic changes during cancer development, the potency of epigenetic therapies seems to be of great importance. Here, we summarize the data on different classes of HDAC inhibitors, mechanisms of their actions and discuss novel results of preclinical and clinical studies, including the combination with other therapeutic modalities.
815 citations
TL;DR: The choice of first-line treatment in CRC follows a multimodal approach based on tumour-related characteristics and usually comprises surgical resection followed by chemotherapy combined with monoclonal antibodies or proteins against vascular endothelial growth factor (VEGF) and epidermal growth receptor (EGFR).
Abstract: Colorectal cancer (CRC) is the third most common cancer and the fourth most common cause of cancer-related death. Most cases of CRC are detected in Western countries, with its incidence increasing year by year. The probability of suffering from colorectal cancer is about 4%–5% and the risk for developing CRC is associated with personal features or habits such as age, chronic disease history and lifestyle. In this context, the gut microbiota has a relevant role, and dysbiosis situations can induce colonic carcinogenesis through a chronic inflammation mechanism. Some of the bacteria responsible for this multiphase process include Fusobacterium spp, Bacteroides fragilis and enteropathogenic Escherichia coli. CRC is caused by mutations that target oncogenes, tumour suppressor genes and genes related to DNA repair mechanisms. Depending on the origin of the mutation, colorectal carcinomas can be classified as sporadic (70%); inherited (5%) and familial (25%). The pathogenic mechanisms leading to this situation can be included in three types, namely chromosomal instability (CIN), microsatellite instability (MSI) and CpG island methylator phenotype (CIMP). Within these types of CRC, common mutations, chromosomal changes and translocations have been reported to affect important pathways (WNT, MAPK/PI3K, TGF-β, TP53), and mutations; in particular, genes such as c-MYC, KRAS, BRAF, PIK3CA, PTEN, SMAD2 and SMAD4 can be used as predictive markers for patient outcome. In addition to gene mutations, alterations in ncRNAs, such as lncRNA or miRNA, can also contribute to different steps of the carcinogenesis process and have a predictive value when used as biomarkers. In consequence, different panels of genes and mRNA are being developed to improve prognosis and treatment selection. The choice of first-line treatment in CRC follows a multimodal approach based on tumour-related characteristics and usually comprises surgical resection followed by chemotherapy combined with monoclonal antibodies or proteins against vascular endothelial growth factor (VEGF) and epidermal growth receptor (EGFR). Besides traditional chemotherapy, alternative therapies (such as agarose tumour macrobeads, anti-inflammatory drugs, probiotics, and gold-based drugs) are currently being studied to increase treatment effectiveness and reduce side effects.
762 citations
TL;DR: Proposals of the cell of origin of liver tumorigenesis are reviewed and the classes of liver cancer based on molecular features are clarified and how they affect patient prognosis are clarified.
687 citations
TL;DR: The rationale for targeting TGF-β signaling in cancer is reviewed, the clinical status of pharmacological inhibitors are summarized, and the direct effects of TGF -β signaling blockade on tumor and stromal cells are discussed.
Abstract: The transforming growth factor (TGF)-β signaling pathway is deregulated in many diseases, including cancer. In healthy cells and early-stage cancer cells, this pathway has tumor-suppressor functions, including cell-cycle arrest and apoptosis. However, its activation in late-stage cancer can promote tumorigenesis, including metastasis and chemoresistance. The dual function and pleiotropic nature of TGF-β signaling make it a challenging target and imply the need for careful therapeutic dosing of TGF-β drugs and patient selection. We review here the rationale for targeting TGF-β signaling in cancer and summarize the clinical status of pharmacological inhibitors. We discuss the direct effects of TGF-β signaling blockade on tumor and stromal cells, as well as biomarkers that can predict the efficacy of TGF-β inhibitors in cancer patients.
671 citations
TL;DR: This review focuses on the current understanding of the tumor promoting and the tumor suppressive functions of ROS, and highlights the potential mechanism(s) involved, and sheds light on a very novel and an actively growing field of ROS‐dependent cell death mechanism referred to as ferroptosis.
666 citations
TL;DR: Fusobacterium nucleatum increased proliferation and invasive activities of CRC cell lines compared with control cells and levels of F nucleatum DNA and miR21 were increased in tumor tissues compared with non-tumor colon tissues from patients.
555 citations
TL;DR: The role of β-catenin in cancer initiation, progression, dormancy, immunity and cancer stem cell maintenance is focused on, and the recent progress in the development of agents for the pharmacological modulation ofβ-Catenin activity in cancer therapy is summarized.
Abstract: // Shuang Shang 1,* , Fang Hua 1,* and Zhuo-Wei Hu 1 1 Immunology and Cancer Pharmacology Group, State Key Laboratory of Bioactive Substance and Function of Natural Medicines, Institute of Materia Medica; Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing, P.R. China * These authors have contributed equally to this work Correspondence to: Zhuo-Wei Hu, email: // Keywords : Wnt signaling, protein stability, subcellular localization, transcriptional regulation, cancer therapy Received : December 20, 2016 Accepted : February 15, 2017 Published : February 25, 2017 Abstract Wnt/β-catenin signaling is an evolutionarily conserved and versatile pathway that is known to be involved in embryonic development, tissue homeostasis and a wide variety of human diseases. Aberrant activation of this pathway gives rise to the accumulation of β-catenin in the nucleus and promotes the transcription of many oncogenes such as c-Myc and CyclinD-1 . As a result, it contributes to carcinogenesis and tumor progression of several cancers, including colon cancer, hepatocellular carcinoma, pancreatic cancer, lung cancer and ovarian cancer. β-Catenin is a pivotal component of the Wnt signaling pathway and it is tightly regulated at three hierarchical levels: protein stability, subcellular localization and transcriptional activity. Uncovering the regulatory mechanisms of β-catenin will provide new insights into the pathogenesis of cancer and other diseases, as well as new therapeutic strategies against these diseases. In this review we dissect the concrete regulatory mechanisms of β-catenin from three aspects mentioned above. Then we focus on the role of β-catenin in cancer initiation, progression, dormancy, immunity and cancer stem cell maintenance. At last, we summarize the recent progress in the development of agents for the pharmacological modulation of β-catenin activity in cancer therapy.
TL;DR: In this article, a combination of CRISPR-Cas9-based genetic screening and metabolomic analyses was used to identify mutations in the KEAP1 gene encoding Kelch-like ECH-associated protein 1 (KEAP1), a negative regulator of nuclear factor erythroid 2-like 2 (NFE2L2), which is the master transcriptional regulator of the endogenous antioxidant response.
Abstract: Treating KRAS-mutant lung adenocarcinoma (LUAD) remains a major challenge in cancer treatment given the difficulties associated with directly inhibiting the KRAS oncoprotein. One approach to addressing this challenge is to define mutations that frequently co-occur with those in KRAS, which themselves may lead to therapeutic vulnerabilities in tumors. Approximately 20% of KRAS-mutant LUAD tumors carry loss-of-function mutations in the KEAP1 gene encoding Kelch-like ECH-associated protein 1 (refs. 2, 3, 4), a negative regulator of nuclear factor erythroid 2-like 2 (NFE2L2; hereafter NRF2), which is the master transcriptional regulator of the endogenous antioxidant response. The high frequency of mutations in KEAP1 suggests an important role for the oxidative stress response in lung tumorigenesis. Using a CRISPR-Cas9-based approach in a mouse model of KRAS-driven LUAD, we examined the effects of Keap1 loss in lung cancer progression. We show that loss of Keap1 hyperactivates NRF2 and promotes KRAS-driven LUAD in mice. Through a combination of CRISPR-Cas9-based genetic screening and metabolomic analyses, we show that Keap1- or Nrf2-mutant cancers are dependent on increased glutaminolysis, and this property can be therapeutically exploited through the pharmacological inhibition of glutaminase. Finally, we provide a rationale for stratification of human patients with lung cancer harboring KRAS/KEAP1- or KRAS/NRF2-mutant lung tumors as likely to respond to glutaminase inhibition.
TL;DR: It is shown that increased lipid unsaturation is a metabolic marker for ovarian CSCs and a target for CSC-specific therapy and Mechanistically, it is demonstrated that nuclear factor κB (NF-κB) directly regulates the expression levels of lipid desaturases, and inhibition of desaturase blocks NF-κBs signaling.
14 Aug 2017
TL;DR: It is shown that patients with primary malignant brain tumors have a devastating outcome and overall reduced survival when Nrf2 levels are upregulated and NRF2 presents the Achilles’ heel of cancer cells and thus provides a valid therapeutic target for sensitizing cancer for chemotherapeutics.
Abstract: Cancer cells are hallmarked by high proliferation and imbalanced redox consumption and signaling. Various oncogenic pathways such as proliferation and evading cell death converge on redox-dependent signaling processes. Nrf2 is a key regulator in these redox-dependent events and operates in cytoprotection, drug metabolism and malignant progression in cancer cells. Here, we show that patients with primary malignant brain tumors (glioblastomas, WHO °IV gliomas, GBM) have a devastating outcome and overall reduced survival when Nrf2 levels are upregulated. Nrf2 overexpression or Keap1 knockdown in glioma cells accelerate proliferation and oncogenic transformation. Further, activation of the Nrf2-Keap1 signaling upregulates xCT (aka SLC7A11 or system Xc−) and amplifies glutamate secretion thereby impacting on the tumor microenvironment. Moreover, both fostered Nrf2 expression and conversely Keap1 inhibition promote resistance to ferroptosis. Altogether, the Nrf2-Keap1 pathway operates as a switch for malignancy in gliomas promoting cell proliferation and resistance to cell death processes such as ferroptosis. Our data demonstrate that the Nrf2-Keap1 pathway is critical for cancer cell growth and operates on xCT. Nrf2 presents the Achilles’ heel of cancer cells and thus provides a valid therapeutic target for sensitizing cancer for chemotherapeutics.
06 Mar 2017
TL;DR: The two faces of ROS in cancer, the potential mechanisms underlying ROS signaling, and the opposing cancer therapeutic approaches to targeting ROS are discussed.
Abstract: Reactive oxygen species (ROS), now appreciated for their cellular signaling capabilities, have a dual role in cancer. On the one hand, ROS can promote protumorigenic signaling, facilitating cancer cell proliferation, survival, and adaptation to hypoxia. On the other hand, ROS can promote antitumorigenic signaling and trigger oxidative stress–induced cancer cell death. To hyperactivate the cell signaling pathways necessary for cellular transformation and tumorigenesis, cancer cells increase their rate of ROS production compared with normal cells. Concomitantly, in order to maintain ROS homeostasis and evade cell death, cancer cells increase their antioxidant capacity. Compared with normal cells, this altered redox environment of cancer cells may increase their susceptibility to ROS-manipulation therapies. In this review, we discuss the two faces of ROS in cancer, the potential mechanisms underlying ROS signaling, and the opposing cancer therapeutic approaches to targeting ROS.
TL;DR: CircRNA, together with its gene silencing ability, also shows its potential in RNA interference (RNAi) therapy by binding to target RNAs, which provides a novel perspective in cancer treatment.
Abstract: Circular RNAs (circRNAs) are long, non-coding RNAs that result from the non-canonical splicing of linear pre-mRNAs. However, the characteristics and the critical role of circRNA in co-/post-transcr...
TL;DR: Recent research regarding miR-30a is summarized, including its biological function, expression and regulation, especially focusing on its role in cancer development and progression, which may serve as a potential target in the diagnosis and therapy of human cancer.
Abstract: MicroRNAs (miRNAs) are a group of noncoding RNA molecules of 20-23 nucleotides length that negatively regulate gene expressions in numerous cellular processes. Through complementary paring with target mRNAs, miRNAs have frequently emerged as dual regulators of cancer development by acting on multiple signaling pathways, thereby act as novel biomarkers for cancer diagnosis, prognosis, and prediction of response to treatment. As one of them, miR-30a has been found to act as an onco-suppressor of tumorigenesis pathways through inhibition of cellular proliferation, migration and invasion. Simultaneously, miR-30a plays a progressing role in several types of cancer, determined by relevant target genes as well. In the present review, we summarize recent research regarding miR-30a, including its biological function, expression and regulation, especially focusing on its role in cancer development and progression. Clinically, miR-30a may serve as a potential target in the diagnosis and therapy of human cancer.
TL;DR: It is found that co-activation of Myc drives the immediate transition to highly proliferative and invasive adenocarcinomas marked by highly inflammatory, angiogenic, and immune-suppressed stroma, and that Myc extensively programs an immune suppressive stroma that is obligatory for tumor progression.
TL;DR: NRF2 inducers may be useful for cancer chemotherapy in combination with conventional anticancer agents or even NRF2 inhibitors, and diagnosis of NRf2 activation could facilitate the use of NRF 2 inhibitors for the treatment of patients with NRF1-addicted cancers.
Abstract: Cancer cells first adapt to the microenvironment and then propagate. Mutations in tumor suppressor genes or oncogenes are frequently found in cancer cells. Comprehensive genomic analyses have identified somatic mutations and other alterations in the KEAP1 or NRF2 genes and in well-known tumor suppressor genes or oncogenes, such as TP53, CDKN2A, PTEN, and PIK3CA, in various types of cancer. Aberrant NRF2 activation in cancer cells occurs through somatic mutations in the KEAP1 or NRF2 gene as well as through other mechanisms that disrupt the binding of KEAP1 to NRF2. Unregulated NRF2 confers on cancer cells high-level resistance to anti-cancer drugs and reactive oxygen species (ROS) and directs cancer cells toward metabolic reprogramming. Therefore, NRF2 has been studied as a therapeutic target molecule in cancer. Two strategies have been used to target NRF2 via therapeutic drugs: inhibition of NRF2 and induction of NRF2. NRF2 inhibitors may be effective against NRF2-addicted cancer cells in which NRF2 is aberrantly activated. These inhibitors have not yet been established as NRF2-targeted anti-cancer drugs for the treatment of human cancers. Diagnosis of NRF2 activation could facilitate the use of NRF2 inhibitors for the treatment of patients with NRF2-addicted cancers. Conversely, NRF2 inducers have been used or are being developed for non-cancer diseases. In addition, NRF2 inducers may be useful for cancer chemotherapy in combination with conventional anti-cancer agents or even NRF2 inhibitors.
TL;DR: The LIN28/let-7 pathway is discussed, emphasizing its role in tumorigenesis, cancer stem cell biology, metabolomics, metastasis, and resistance to ionizing radiation and several chemotherapies, and emerging evidence is presented suggesting that molecular targeting of this pathway may provide therapeutic benefit in cancer.
Abstract: Among all tumor suppressor microRNAs, reduced let-7 expression occurs most frequently in cancer and typically correlates with poor prognosis. Activation of either LIN28A or LIN28B, two highly related RNA binding proteins (RBPs) and proto-oncogenes, is responsible for the global post-transcriptional downregulation of the let-7 microRNA family observed in many cancers. Specifically, LIN28A binds the terminal loop of precursor let-7 and recruits the Terminal Uridylyl Transferase (TUTase) ZCCHC11 that polyuridylates pre-let-7, thereby blocking microRNA biogenesis and tumor suppressor function. For LIN28B, the precise mechanism responsible for let-7 inhibition remains controversial. Functionally, the decrease in let-7 microRNAs leads to overexpression of their oncogenic targets such as MYC, RAS, HMGA2, BLIMP1, among others. Furthermore, mouse models demonstrate that ectopic LIN28 expression is sufficient to drive and/or accelerate tumorigenesis via a let-7 dependent mechanism. In this review, the LIN28/let-7 pathway is discussed, emphasizing its role in tumorigenesis, cancer stem cell biology, metabolomics, metastasis, and resistance to ionizing radiation and several chemotherapies. Also, emerging evidence will be presented suggesting that molecular targeting of this pathway may provide therapeutic benefit in cancer.
TL;DR: The aim of this study was to review molecular aspects of cancer, and to improve understanding of the role of genetic disorders in cancer formation.
TL;DR: The biogenesis of miRNAs is discussed, focusing on the mechanisms by which they regulate protein synthesis, and their role in cancer is debated, highlighting their potential to become therapeutic targets.
Abstract: MicroRNAs (miRNAs) are pervasively expressed and regulate most biological functions. They function by modulating transcriptional and translational programs and therefore they orchestrate both physiological and pathological processes, such as development, cell differentiation, proliferation, apoptosis and tumor growth. miRNAs work as small guide molecules in RNA silencing, by negatively regulating the expression of several genes both at mRNA and protein level, by degrading their mRNA target and/or by silencing translation. One of the most recent advances in the field is the comprehension of their role in oncogenesis. The number of miRNA genes is increasing and an alteration in the level of miRNAs is involved in the initiation, progression and metastases formation of several tumors. Some tumor types show a distinct miRNA signature that distinguishes them from normal tissues and from other cancer types. Genetic and biochemical evidence supports the essential role of miRNAs in tumor development. Although the abnormal expression of miRNAs in cancer cells is a widely accepted phenomenon, the cause of this dysregulation is still unknown. Here, we discuss the biogenesis of miRNAs, focusing on the mechanisms by which they regulate protein synthesis. In addition we debate on their role in cancer, highlighting their potential to become therapeutic targets.
01 Oct 2017
TL;DR: It is shown that Keap1- or Nrf2-mutant cancers are dependent on increased glutaminolysis, and this property can be therapeutically exploited through the pharmacological inhibition of glutaminase.
Abstract: Treating KRAS-mutant lung adenocarcinoma (LUAD) remains a major challenge in cancer treatment given the difficulties associated with directly inhibiting the KRAS oncoprotein. One approach to addressing this challenge is to define mutations that frequently co-occur with those in KRAS, which themselves may lead to therapeutic vulnerabilities in tumors. Approximately 20% of KRAS-mutant LUAD tumors carry loss-of-function mutations in the KEAP1 gene encoding Kelch-like ECH-associated protein 1 (refs. 2, 3, 4), a negative regulator of nuclear factor erythroid 2-like 2 (NFE2L2; hereafter NRF2), which is the master transcriptional regulator of the endogenous antioxidant response. The high frequency of mutations in KEAP1 suggests an important role for the oxidative stress response in lung tumorigenesis. Using a CRISPR-Cas9-based approach in a mouse model of KRAS-driven LUAD, we examined the effects of Keap1 loss in lung cancer progression. We show that loss of Keap1 hyperactivates NRF2 and promotes KRAS-driven LUAD in mice. Through a combination of CRISPR-Cas9-based genetic screening and metabolomic analyses, we show that Keap1- or Nrf2-mutant cancers are dependent on increased glutaminolysis, and this property can be therapeutically exploited through the pharmacological inhibition of glutaminase. Finally, we provide a rationale for stratification of human patients with lung cancer harboring KRAS/KEAP1- or KRAS/NRF2-mutant lung tumors as likely to respond to glutaminase inhibition.
TL;DR: Data demonstrate that the HIF-1α/VEGF-A axis is an essential aspect of tumor immunity and inverse correlations between VEGF-A expression and CD8+ T cell infiltration, and a link between T Cell infiltration and vascularization.
TL;DR: Both high CD44/CD24 ratio and ALDH1+ were conserved during metastasis, suggesting the significant value of these CSC markers in assisting cancer detection, prognostic evaluation, and even cancer therapeutics.
Abstract: CD44/CD24 and ALDH1 are widely used cancer stem cell (CSC) markers in breast cancer. However, their expression is not always consistent even in the same subtype of breast cancer. Systematic comparison of their functions is still lacking. We investigated the expression of CD44, CD24 and ALDH1 in different subtypes of breast cancer cells, and explored their relationship with cancer progression. We defined a parameter CD44/CD24 ratio to present the expression level of CD44 and CD24 and found that high CD44/CD24 ratio and ALDH1+ are both indicators for cancer malignancy, but play different functions during tumor progression. High CD44/CD24 ratio is more related to cell proliferation and tumorigenesis, which is confirmed by mammosphere formation and tumorigenesis in xenotransplanted mice. ALDH1+ is a stronger indicator for cell migration and tumor metastasis. Suppression of CD44 and ALDH1 by siRNA led to decreased tumorigenicity and cell migration capacity. The combination of high CD44/CD24 ratio and ALDH1+ would be a more reliable way to characterize CSCs. Moreover, both high CD44/CD24 ratio and ALDH1+ were conserved during metastasis, from the primary tumors to the circulating tumor cells (CTCs) and the distant metastases, suggesting the significant value of these CSC markers in assisting cancer detection, prognostic evaluation, and even cancer therapeutics.
TL;DR: This work discovers that BAP1 localizes at the endoplasmic reticulum, and binds, deubiquitylates, and stabilizes type 3 inositol-1,4,5-trisphosphate receptor (IP3R3), modulating calcium release into the cytosol and mitochondria, promoting apoptosis.
Abstract: BRCA1-associated protein 1 (BAP1) is a potent tumour suppressor gene that modulates environmental carcinogenesis. All carriers of inherited heterozygous germline BAP1-inactivating mutations (BAP1+/-) developed one and often several BAP1-/- malignancies in their lifetime, mostly malignant mesothelioma, uveal melanoma, and so on. Moreover, BAP1-acquired biallelic mutations are frequent in human cancers. BAP1 tumour suppressor activity has been attributed to its nuclear localization, where it helps to maintain genome integrity. The possible activity of BAP1 in the cytoplasm is unknown. Cells with reduced levels of BAP1 exhibit chromosomal abnormalities and decreased DNA repair by homologous recombination, indicating that BAP1 dosage is critical. Cells with extensive DNA damage should die and not grow into malignancies. Here we discover that BAP1 localizes at the endoplasmic reticulum. Here, it binds, deubiquitylates, and stabilizes type 3 inositol-1,4,5-trisphosphate receptor (IP3R3), modulating calcium (Ca2+) release from the endoplasmic reticulum into the cytosol and mitochondria, promoting apoptosis. Reduced levels of BAP1 in BAP1+/- carriers cause reduction both of IP3R3 levels and of Ca2+ flux, preventing BAP1+/- cells that accumulate DNA damage from executing apoptosis. A higher fraction of cells exposed to either ionizing or ultraviolet radiation, or to asbestos, survive genotoxic stress, resulting in a higher rate of cellular transformation. We propose that the high incidence of cancers in BAP1+/- carriers results from the combined reduced nuclear and cytoplasmic activities of BAP1. Our data provide a mechanistic rationale for the powerful ability of BAP1 to regulate gene-environment interaction in human carcinogenesis.
European Bioinformatics Institute1, Francis Crick Institute2, Broad Institute3, Wellcome Trust Sanger Institute4, University of Toronto5, Oregon Health & Science University6, University of Texas MD Anderson Cancer Center7, German Cancer Research Center8, NorthShore University HealthSystem9, University of Cambridge10, Simon Fraser University11, University of Melbourne12, Cornell University13, University of California, Santa Cruz14, Peter MacCallum Cancer Centre15, Indiana University16, University of Cologne17, University of Helsinki18, University of Glasgow19, University of Oxford20
TL;DR: Whole-genome sequencing of 2,778 tumour samples from 2,658 donors is used to reconstruct the life history, evolution of mutational processes, and driver mutation sequences of 39 cancer types, suggesting a window of opportunity for early cancer detection.
Abstract: Cancer develops through a process of somatic evolution. Here, we reconstruct the evolutionary history of 2,778 tumour samples from 2,658 donors spanning 39 cancer types. Characteristic copy number gains, such as trisomy 7 in glioblastoma or isochromosome 17q in medulloblastoma, are found amongst the earliest events in tumour evolution. The early phases of oncogenesis are driven by point mutations in a restricted set of cancer genes, often including biallelic inactivation of tumour suppressors. By contrast, increased genomic instability, a more than three-fold diversification of driver genes, and an acceleration of mutational processes are features of later stages. Clock-like mutations yield estimates for whole genome duplications and subclonal diversification in chronological time. Our results suggest that driver mutations often precede diagnosis by many years, and in some cases decades. Taken together, these data reveal common and divergent trajectories of cancer evolution, pivotal for understanding tumour biology and guiding early cancer detection.
Journal Article•
TL;DR: Results identified a new functional circ-ABCB10 in breast cancer tumorigenesis, and reveal the important regulatory role of circ- ABCB10 through sponging miR-1271, providing a novel insight for breast cancer pathogenesis.
Abstract: Circular RNA (circRNA) is a key regulator in the development and progression of human cancers, however its role in breast cancer tumorigenesis is not well understood. The present study aims to investigate the expression profiles and potential modulation of circRNA on breast cancer carcinogenesis. Human circRNA microarray was performed to screen for abnormally expressed circRNA in breast cancer tissue. Results found circ-ABCB10, was significantly up-regulated in breast cancer tissue. And results were replicated in a larger sample size. In vitro, loss-of-function experiments showed circ-ABCB10 knockdown suppressed the proliferation and increased apoptosis of breast cancer cells. Bioinformatics prediction program predicted the complementary sequence within circ-ABCB10 and miR-1271, which was validated by luciferase reporter assay. Finally, miR-1271 rescued the function of circ-ABCB10 on breast cancer cells, confirming the sponge effect of circ-ABCB10 on miR-1271. Overall, results identified a new functional circ-ABCB10 in breast cancer tumorigenesis, and reveal the important regulatory role of circ-ABCB10 through sponging miR-1271, providing a novel insight for breast cancer pathogenesis.
TL;DR: The crossroads between inflammasomes and the development of various tumors are explored and possible therapeutic values in targeting theinflammasome for the prevention and treatment of cancer are discussed.
Abstract: Inflammation affects all stages of tumorigenesis. A key signaling pathway leading to acute and chronic inflammation is through activation of the caspase-1 inflammasome. Inflammasome complexes are assembled on activation of certain nucleotide-binding domain, leucine-rich repeat-containing proteins (NLR), AIM2-like receptors, or pyrin. Of these, NLRP1, NLRP3, NLRC4, NLRP6, and AIM2 influence the pathogenesis of cancer by modulating innate and adaptive immune responses, cell death, proliferation, and/or the gut microbiota. Activation of the inflammasome and IL18 signaling pathways is largely protective in colitis-associated colorectal cancer, whereas excessive inflammation driven by the inflammasome or the IL1 signaling pathways promotes breast cancer, fibrosarcoma, gastric carcinoma, and lung metastasis in a context-dependent manner. The clinical relevance of inflammasomes in multiple forms of cancer highlights their therapeutic promise as molecular targets. In this review, we explore the crossroads between inflammasomes and the development of various tumors and discuss possible therapeutic values in targeting the inflammasome for the prevention and treatment of cancer. Cancer Immunol Res; 5(2); 94-99. ©2017 AACR.
TL;DR: This review presents a discussion of how deregulation of various epigenetic pathways can contribute to cancer initiation and tumorigenesis, particularly with respect to maintenance and survival of cancer stem cells.
Abstract: Compelling evidence have demonstrated that bulk tumors can arise from a unique subset of cells commonly termed “cancer stem cells” that has been proposed to be a strong driving force of tumorigenesis and a key mechanism of therapeutic resistance. Recent advances in epigenomics have illuminated key mechanisms by which epigenetic regulation contribute to cancer progression. In this review, we present a discussion of how deregulation of various epigenetic pathways can contribute to cancer initiation and tumorigenesis, particularly with respect to maintenance and survival of cancer stem cells. This information, together with several promising clinical and preclinical trials of epigenetic modulating drugs, offer new possibilities for targeting cancer stem cells as well as improving cancer therapy overall.