Showing papers on "Carcinogenesis published in 2012"
Bankstown Lidcombe Hospital1, Garvan Institute of Medical Research2, University of New South Wales3, University of Queensland4, Baylor College of Medicine5, Ontario Institute for Cancer Research6, University of Newcastle7, Royal North Shore Hospital8, University of Sydney9, Life Technologies10, St. Vincent's Health System11, Royal Prince Alfred Hospital12, Fremantle Hospital13, Royal Adelaide Hospital14, University of Western Australia15, University of California, Los Angeles16, University Health Network17, Mayo Clinic18, University of Toronto19, Johns Hopkins University20, University of Verona21, University of California, San Francisco22, Houston Methodist Hospital23, Cancer Research UK24, Wellcome Trust Sanger Institute25, University of Minnesota26, Netherlands Cancer Institute27
TL;DR: It is found that frequent and diverse somatic aberrations in genes described traditionally as embryonic regulators of axon guidance, particularly SLIT/ROBO signalling, are also evident in murine Sleeping Beauty transposon-mediated somatic mutagenesis models of pancreatic cancer, providing further supportive evidence for the potential involvement ofAxon guidance genes in pancreatic carcinogenesis.
Abstract: Pancreatic cancer is a highly lethal malignancy with few effective therapies. We performed exome sequencing and copy number analysis to define genomic aberrations in a prospectively accrued clinical cohort (n = 142) of early (stage I and II) sporadic pancreatic ductal adenocarcinoma. Detailed analysis of 99 informative tumours identified substantial heterogeneity with 2,016 non-silent mutations and 1,628 copy-number variations. We define 16 significantly mutated genes, reaffirming known mutations (KRAS, TP53, CDKN2A, SMAD4, MLL3, TGFBR2, ARID1A and SF3B1), and uncover novel mutated genes including additional genes involved in chromatin modification (EPC1 and ARID2), DNA damage repair (ATM) and other mechanisms (ZIM2, MAP2K4, NALCN, SLC16A4 and MAGEA6). Integrative analysis with in vitro functional data and animal models provided supportive evidence for potential roles for these genetic aberrations in carcinogenesis. Pathway-based analysis of recurrently mutated genes recapitulated clustering in core signalling pathways in pancreatic ductal adenocarcinoma, and identified new mutated genes in each pathway. We also identified frequent and diverse somatic aberrations in genes described traditionally as embryonic regulators of axon guidance, particularly SLIT/ROBO signalling, which was also evident in murine Sleeping Beauty transposon-mediated somatic mutagenesis models of pancreatic cancer, providing further supportive evidence for the potential involvement of axon guidance genes in pancreatic carcinogenesis.
1,752 citations
TL;DR: High-throughput sequencing revealed that inflammation modifies gut microbial composition in colitis-susceptible interleukin-10–deficient (Il10−/−) mice, suggesting that in mice, colitis can promote tumorigenesis by altering microbial composition and inducing the expansion of microorganisms with genotoxic capabilities.
Abstract: Inflammation alters host physiology to promote cancer, as seen in colitis-associated colorectal cancer (CRC). Here, we identify the intestinal microbiota as a target of inflammation that affects the progression of CRC. High-throughput sequencing revealed that inflammation modifies gut microbial composition in colitis-susceptible interleukin-10-deficient (Il10(-/-)) mice. Monocolonization with the commensal Escherichia coli NC101 promoted invasive carcinoma in azoxymethane (AOM)-treated Il10(-/-) mice. Deletion of the polyketide synthase (pks) genotoxic island from E. coli NC101 decreased tumor multiplicity and invasion in AOM/Il10(-/-) mice, without altering intestinal inflammation. Mucosa-associated pks(+) E. coli were found in a significantly high percentage of inflammatory bowel disease and CRC patients. This suggests that in mice, colitis can promote tumorigenesis by altering microbial composition and inducing the expansion of microorganisms with genotoxic capabilities.
1,720 citations
Wellcome Trust Sanger Institute1, Wellcome Trust2, Katholieke Universiteit Leuven3, University of East Anglia4, Guy's and St Thomas' NHS Foundation Trust5, Academia Sinica6, Singapore General Hospital7, Netherlands Cancer Institute8, University of Queensland9, University of British Columbia10, Erasmus University Rotterdam11, Harvard University12, University of Cambridge13, Claude Bernard University Lyon 114, Curie Institute15, Royal Brisbane and Women's Hospital16, University of Amsterdam17, Université libre de Bruxelles18, The Breast Cancer Research Foundation19, Cambridge University Hospitals NHS Foundation Trust20, Oslo University Hospital21
TL;DR: Strong correlations between mutation number, age at which cancer was diagnosed and cancer histological grade are found, and multiple mutational signatures are observed, including one present in about ten per cent of tumours characterized by numerous mutations of cytosine at TpC dinucleotides.
Abstract: All cancers carry somatic mutations in their genomes. A subset, known as driver mutations, confer clonal selective advantage on cancer cells and are causally implicated in oncogenesis, and the remainder are passenger mutations. The driver mutations and mutational processes operative in breast cancer have not yet been comprehensively explored. Here we examine the genomes of 100 tumours for somatic copy number changes and mutations in the coding exons of protein-coding genes. The number of somatic mutations varied markedly between individual tumours. We found strong correlations between mutation number, age at which cancer was diagnosed and cancer histological grade, and observed multiple mutational signatures, including one present in about ten per cent of tumours characterized by numerous mutations of cytosine at TpC dinucleotides. Driver mutations were identified in several new cancer genes including AKT2, ARID1B, CASP8, CDKN1B, MAP3K1, MAP3K13, NCOR1, SMARCD1 and TBX3. Among the 100 tumours, we found driver mutations in at least 40 cancer genes and 73 different combinations of mutated cancer genes. The results highlight the substantial genetic diversity underlying this common disease.
1,606 citations
TL;DR: Examining the mutational spectra of Ras isoforms curated from large-scale tumor profiling found that each isoform exhibits surprisingly distinctive codon mutation and amino-acid substitution biases, which were unexpected given that these mutations occur in regions that share 100% amino- acid sequence identity among the 3 isoforms.
Abstract: All mammalian cells express three closely related Ras proteins: H-Ras, K-Ras and N-Ras that promote oncogenesis when mutationally activated at codons 12, 13 or 61. Despite a high degree of similarity between the isoforms, K-Ras mutations are far more frequently observed in cancer and each isoform displays preferential coupling to particular cancer types. We have examined the mutation spectra of Ras isoforms curated from large-scale tumour profiling and found that each isoform exhibits surprisingly distinctive codon mutation and amino acid substitution biases. These were unexpected given that these mutations occur in regions that share 100% amino acid sequence identity between the three isoforms. Importantly, many of the mutational biases were not due to differences in exposure to mutagens because the patterns were still evident when compared within specific cancer types. We discuss potential genetic and epigenetic mechanisms together with isoform-specific differences in protein structure and signalling that may promote these distinct mutation patterns and differential coupling to specific cancers.
1,598 citations
TL;DR: The composition of the microbiota in colorectal carcinoma is characterized using whole genome sequences from nine tumor/normal pairs and Fusobacterium sequences were enriched in carcinomas, confirmed by quantitative PCR and 16S rDNA sequence analysis of 95 carcinoma/normal DNA pairs.
Abstract: The tumor microenvironment of colorectal carcinoma is a complex community of genomically altered cancer cells, nonneoplastic cells, and a diverse collection of microorganisms. Each of these components may contribute to carcinogenesis; however, the role of the microbiota is the least well understood. We have characterized the composition of the microbiota in colorectal carcinoma using whole genome sequences from nine tumor/normal pairs. Fusobacterium sequences were enriched in carcinomas, confirmed by quantitative PCR and 16S rDNA sequence analysis of 95 carcinoma/normal DNA pairs, while the Bacteroidetes and Firmicutes phyla were depleted in tumors. Fusobacteria were also visualized within colorectal tumors using FISH. These findings reveal alterations in the colorectal cancer microbiota; however, the precise role of Fusobacteria in colorectal carcinoma pathogenesis requires further investigation.
1,527 citations
TL;DR: GSK126, a potent, highly selective, S-adenosyl-methionine-competitive, small-molecule inhibitor of EZH2 methyltransferase activity, decreases global H3K27me3 levels and reactivates silenced PRC2 target genes and markedly inhibits the growth of EzH2 mutant DLBCL xenografts in mice are demonstrated.
Abstract: EZH2, the catalytic subunit of the polycomb repressive complex 2 (PRC2), is involved in repressing gene expression through methylation of histone H3 on lysine 27 (H3K27). Overexpression of EZH2 is implicated in tumorigenesis, and mutations within its catalytic domain occur in lymphoma. Here, Caretha Creasy and colleagues describe a potent small-molecule inhibitor of EZH2 methyltransferase activity that decreases levels of methylated H3K27 and reactivates silenced PRC2 target genes. It also inhibits the proliferation of EZH2 mutant cell lines and the growth of EZH2 mutant xenografts in mice. Pharmacological inhibition of EZH2 activity may therefore be a viable strategy for treating EZH2 mutant lymphoma.
1,514 citations
TL;DR: SPOP mutations may define a new molecular subtype of prostate cancer, with mutations involving the SPOP substrate-binding cleft in 6–15% of tumors across multiple independent cohorts.
Abstract: Prostate cancer is the second most common cancer in men worldwide and causes over 250,000 deaths each year. Overtreatment of indolent disease also results in significant morbidity. Common genetic alterations in prostate cancer include losses of NKX3.1 (8p21) and PTEN (10q23), gains of AR (the androgen receptor gene) and fusion of ETS family transcription factor genes with androgen-responsive promoters. Recurrent somatic base-pair substitutions are believed to be less contributory in prostate tumorigenesis but have not been systematically analyzed in large cohorts. Here, we sequenced the exomes of 112 prostate tumor and normal tissue pairs. New recurrent mutations were identified in multiple genes, including MED12 and FOXA1. SPOP was the most frequently mutated gene, with mutations involving the SPOP substrate-binding cleft in 6-15% of tumors across multiple independent cohorts. Prostate cancers with mutant SPOP lacked ETS family gene rearrangements and showed a distinct pattern of genomic alterations. Thus, SPOP mutations may define a new molecular subtype of prostate cancer.
1,370 citations
University of California, San Diego1, Hong Kong University of Science and Technology2, Rockefeller University3, National Institutes of Health4, Keio University5, University of Vienna6, Tufts University7, University of Michigan8, Boston Children's Hospital9, Ohio State University10, University of Texas Southwestern Medical Center11, La Jolla Institute for Allergy and Immunology12
TL;DR: It is proposed that barrier deterioration induced by colorectal-cancer-initiating genetic lesions results in adenoma invasion by microbial products that trigger tumour-elicited inflammation, which in turn drives tumour growth.
Abstract: Approximately 2% of colorectal cancer is linked to pre-existing inflammation known as colitis-associated cancer, but most develops in patients without underlying inflammatory bowel disease. Colorectal cancer often follows a genetic pathway whereby loss of the adenomatous polyposis coli (APC) tumour suppressor and activation of β-catenin are followed by mutations in K-Ras, PIK3CA and TP53, as the tumour emerges and progresses. Curiously, however, 'inflammatory signature' genes characteristic of colitis-associated cancer are also upregulated in colorectal cancer. Further, like most solid tumours, colorectal cancer exhibits immune/inflammatory infiltrates, referred to as 'tumour-elicited inflammation'. Although infiltrating CD4(+) T(H)1 cells and CD8(+) cytotoxic T cells constitute a positive prognostic sign in colorectal cancer, myeloid cells and T-helper interleukin (IL)-17-producing (T(H)17) cells promote tumorigenesis, and a 'T(H)17 expression signature' in stage I/II colorectal cancer is associated with a drastic decrease in disease-free survival. Despite its pathogenic importance, the mechanisms responsible for the appearance of tumour-elicited inflammation are poorly understood. Many epithelial cancers develop proximally to microbial communities, which are physically separated from immune cells by an epithelial barrier. We investigated mechanisms responsible for tumour-elicited inflammation in a mouse model of colorectal tumorigenesis, which, like human colorectal cancer, exhibits upregulation of IL-23 and IL-17. Here we show that IL-23 signalling promotes tumour growth and progression, and development of a tumoural IL-17 response. IL-23 is mainly produced by tumour-associated myeloid cells that are likely to be activated by microbial products, which penetrate the tumours but not adjacent tissue. Both early and late colorectal neoplasms exhibit defective expression of several barrier proteins. We propose that barrier deterioration induced by colorectal-cancer-initiating genetic lesions results in adenoma invasion by microbial products that trigger tumour-elicited inflammation, which in turn drives tumour growth.
1,069 citations
TL;DR: The discovery of microRNAs almost two decades ago established a new paradigm of gene regulation, and during the past ten years these tiny non-coding RNAs have been linked to virtually all known physiological and pathological processes, including cancer.
Abstract: MicroRNAs (miRNAs) are small, evolutionarily conserved, non-coding RNAs of 18–25 nucleotides in length that have an important function in gene regulation. Mature miRNA products are generated from a longer primary miRNA (pri-miRNA) transcript through sequential processing by the ribonucleases Drosha and Dicer1 (ref. 1). The first description of miRNAs was made in 1993 in Caenorhabditis elegans as regulators of developmental timing 2,3 . Later, miRNAs were shown to inhibit their target genes through sequences that are complementary to the target messenger RNA, leading to decreased expression of the target protein 1 (Box 1). This discovery resulted in a pattern shift in our understanding of gene regulation because miRNAs are now known to repress thousands of target genes and coordinate normal processes, including cellular proliferation, differentiation and apoptosis. The aberrant expression or alteration of miRNAs also contributes to a range of human pathologies, including cancer. The control of gene expression by miRNAs is a process seen in virtually all cancer cells. These cells show alterations in their miRNA expression profiles, and emerging data indicate that these patterns could be useful in improving the classification of cancers and predicting their behaviour. In addition, miRNAs have now been shown to behave as cancer ‘drivers’ in the same way as protein-coding genes whose alterations actively and profoundly contribute to malignant transformation and cancer progression. Owing to the capacity of miRNAs to modulate tens to hundreds of target genes, they are emerging as important factors in the control of the ‘hallmarks’ of cancer 4 . In this Review, we summarize the findings that provide evidence for the central role of miRNAs in controlling cellular transformation and tumour progression. We also highlight the potential uses of miRNAs and miRNA-based drugs in cancer therapy and discuss the obstacles that will need to be overcome. miRNAs are cancer genes In 2002, Croce and colleagues first demonstrated that an miRNA cluster was frequently deleted or downregulated in chronic lymphocytic leukaemia 5 . This discovery suggested that non-coding genes were contributing to the development of cancer, and paved the way for the closer investigation of miRNA loss or amplification in tumours. Subsequently, miRNAs were shown to be differentially expressed in cancer cells, in which they formed distinct and unique miRNA expression patterns 6 , and whole classes of miRNAs could be controlled directly by key oncogenic transcription factors 7 . In parallel, studies with mouse models established that miRNAs were actively involved in tumorigenesis
992 citations
TL;DR: A recent outcome of whole exome sequencing of thousands of human cancers has been the unexpected discovery of many inactivating mutations in genes that control the epigenome, which contributes to cancer.
983 citations
Hoffmann-La Roche1, Autonomous University of Barcelona2, Plexxikon3, University of California, Los Angeles4, Harvard University5, Memorial Sloan Kettering Cancer Center6, Peter MacCallum Cancer Centre7, Medical College of Wisconsin8, University of Colorado Denver9, Baylor University Medical Center10, Vanderbilt University11
TL;DR: In this article, the authors performed a molecular analysis to identify oncogenic mutations (HRAS, KRAS, NRAS, CDKN2A, and TP53) in the lesions from patients treated with the BRAF inhibitor vemurafenib.
Abstract: Background Cutaneous squamous-cell carcinomas and keratoacanthomas are common findings in patients treated with BRAF inhibitors. Methods We performed a molecular analysis to identify oncogenic mutations (HRAS, KRAS, NRAS, CDKN2A, and TP53) in the lesions from patients treated with the BRAF inhibitor vemurafenib. An analysis of an independent validation set and functional studies with BRAF inhibitors in the presence of the prevalent RAS mutation was also performed. Results Among 21 tumor samples, 13 had RAS mutations (12 in HRAS). In a validation set of 14 samples, 8 had RAS mutations (4 in HRAS). Thus, 60% (21 of 35) of the specimens harbored RAS mutations, the most prevalent being HRAS Q61L. Increased proliferation of HRAS Q61L–mutant cell lines exposed to vemurafenib was associated with mitogen-activated protein kinase (MAPK)–pathway signaling and activation of ERK-mediated transcription. In a mouse model of HRAS Q61L–mediated skin carcinogenesis, the vemurafenib analogue PLX4720 was not an initiator or...
TL;DR: The R-spondin gene fusions, several new recurrent mutations in the Wnt pathway gene TCF7L2, chromatin-remodelling genes such as TET2 and TET3 and receptor tyrosine kinases including ERBB3 are identified and shown to be capable of potentiating Wnt signalling.
Abstract: Identifying and understanding changes in cancer genomes is essential for the development of targeted therapeutics1. Here we analyse systematically more than 70 pairs of primary human colon tumours by applying next-generation sequencing to characterize their exomes, transcriptomes and copy-number alterations. We have identified 36,303 protein-altering somatic changes that include several new recurrent mutations in the Wnt pathway gene TCF7L2, chromatin-remodelling genes such as TET2 and TET3 and receptor tyrosine kinases including ERBB3. Our analysis for significantly mutated cancer genes identified 23 candidates, including the cell cycle checkpoint kinase ATM. Copy-number and RNA-seq data analysis identified amplifications and corresponding overexpression of IGF2 in a subset of colon tumours. Furthermore, using RNA-seq data we identified multiple fusion transcripts including recurrent gene fusions involving R-spondin family members RSPO2 and RSPO3 that together occur in 10% of colon tumours. The RSPO fusions were mutually exclusive with APC mutations, indicating that they probably have a role in the activation of Wnt signalling and tumorigenesis. Consistent with this we show that the RSPO fusion proteins were capable of potentiating Wnt signalling. The R-spondin gene fusions and several other gene mutations identified in this study provide new potential opportunities for therapeutic intervention in colon cancer.
TL;DR: The findings underscore the crucial role of acetylation in differentially modulating p53 responses and suggest that unconventional activities of p53, such as metabolic regulation and antioxidant function, are critical for suppression of early-onset spontaneous tumorigenesis.
TL;DR: Modelling of mutations in mouse lower rhombic lip progenitors that generate WNT-subgroup tumours identified genes that maintain this cell lineage (DDX3X), as well as mutated genes that initiate (CDH1) or cooperate (PIK3CA) in tumorigenesis.
Abstract: Medulloblastoma is a malignant childhood brain tumour comprising four discrete subgroups. Here, to identify mutations that drive medulloblastoma, we sequenced the entire genomes of 37 tumours and matched normal blood. One-hundred and thirty-six genes harbouring somatic mutations in this discovery set were sequenced in an additional 56 medulloblastomas. Recurrent mutations were detected in 41 genes not yet implicated in medulloblastoma; several target distinct components of the epigenetic machinery in different disease subgroups, such as regulators of H3K27 and H3K4 trimethylation in subgroups 3 and 4 (for example, KDM6A and ZMYM3), and CTNNB1-associated chromatin re-modellers in WNT-subgroup tumours (for example, SMARCA4 and CREBBP). Modelling of mutations in mouse lower rhombic lip progenitors that generate WNT-subgroup tumours identified genes that maintain this cell lineage (DDX3X), as well as mutated genes that initiate (CDH1) or cooperate (PIK3CA) in tumorigenesis. These data provide important new insights into the pathogenesis of medulloblastoma subgroups and highlight targets for therapeutic development.
TL;DR: It is found that mutant p53 depletion is sufficient to phenotypically revert breast cancer cells to a more acinar-like morphology, which implicate the mevalonate pathway as a therapeutic target for tumors bearing mutations in p53.
TL;DR: The findings provide a comprehensive picture of the mutanome of B16F10 melanoma and offer insight into the extent of the immunogenicity of nonsynonymous base substitution mutations, and argue that the use of deep sequencing to systematically analyze immunogenic mutations may pave the way for individualized immunotherapy of cancer patients.
Abstract: Multiple genetic events and subsequent clonal evolution drive carcinogenesis, making disease elimination with single-targeted drugs difficult. The multiplicity of gene mutations derived from clonal heterogeneity therefore represents an ideal setting for multiepitope tumor vaccination. Here, we used next generation sequencing exome resequencing to identify 962 nonsynonymous somatic point mutations in B16F10 murine melanoma cells, with 563 of those mutations in expressed genes. Potential driver mutations occurred in classical tumor suppressor genes and genes involved in proto-oncogenic signaling pathways that control cell proliferation, adhesion, migration, and apoptosis. Aim1 and Trrap mutations known to be altered in human melanoma were included among those found. The immunogenicity and specificity of 50 validated mutations was determined by immunizing mice with long peptides encoding the mutated epitopes. One-third of these peptides were found to be immunogenic, with 60% in this group eliciting immune responses directed preferentially against the mutated sequence as compared with the wild-type sequence. In tumor transplant models, peptide immunization conferred in vivo tumor control in protective and therapeutic settings, thereby qualifying mutated epitopes that include single amino acid substitutions as effective vaccines. Together, our findings provide a comprehensive picture of the mutanome of B16F10 melanoma which is used widely in immunotherapy studies. In addition, they offer insight into the extent of the immunogenicity of nonsynonymous base substitution mutations. Lastly, they argue that the use of deep sequencing to systematically analyze immunogenicity mutations may pave the way for individualized immunotherapy of cancer patients.
TL;DR: It is demonstrated that deletion of mouse Mir122 resulted in hepatosteatosis, hepatitis, and the development of tumors resembling HCC, demonstrating critical functions for miR-122 in the maintenance of liver homeostasis and have important therapeutic implications, including the potential utility of mi R-122 delivery for selected patients with HCC and the need for careful monitoring of patients receiving miR -122 inhibition therapy for HCV.
Abstract: miR-122, an abundant liver-specific microRNA (miRNA), regulates cholesterol metabolism and promotes hepatitis C virus (HCV) replication. Reduced miR-122 expression in hepatocellular carcinoma (HCC) correlates with metastasis and poor prognosis. Nevertheless, the consequences of sustained loss of function of miR-122 in vivo have not been determined. Here, we demonstrate that deletion of mouse Mir122 resulted in hepatosteatosis, hepatitis, and the development of tumors resembling HCC. These pathologic manifestations were associated with hyperactivity of oncogenic pathways and hepatic infiltration of inflammatory cells that produce pro-tumorigenic cytokines, including IL-6 and TNF. Moreover, delivery of miR-122 to a MYC-driven mouse model of HCC strongly inhibited tumorigenesis, further supporting the tumor suppressor activity of this miRNA. These findings reveal critical functions for miR-122 in the maintenance of liver homeostasis and have important therapeutic implications, including the potential utility of miR-122 delivery for selected patients with HCC and the need for careful monitoring of patients receiving miR-122 inhibition therapy for HCV.
TL;DR: Analyzing five cancer types occurring among several individuals found that three types of epithelial tumors exhibited high rates of element movement relative to brain and blood cancers, and Whole-genome sequencing provides evidence for somatic insertions in colorectal, prostate, and ovarian cancers.
Abstract: Transposable elements (TEs) are abundant in the human genome, and some are capable of generating new insertions through RNA intermediates. In cancer, the disruption of cellular mechanisms that normally suppress TE activity may facilitate mutagenic retrotranspositions. We performed single-nucleotide resolution analysis of TE insertions in 43 high-coverage whole-genome sequencing data sets from five cancer types. We identified 194 high-confidence somatic TE insertions, as well as thousands of polymorphic TE insertions in matched normal genomes. Somatic insertions were present in epithelial tumors but not in blood or brain cancers. Somatic L1 insertions tend to occur in genes that are commonly mutated in cancer, disrupt the expression of the target genes, and are biased toward regions of cancer-specific DNA hypomethylation, highlighting their potential impact in tumorigenesis.
TL;DR: It is found that β-catenin active cancers are dependent on a signaling pathway involving the transcriptional regulator YAP1 and the transcription factor TBX5, and this complex is essential to the transformation and survival of β- catenin-driven cancers.
TL;DR: It is demonstrated that metabolic transformation plays an important role in the development of cancer cells and that butyrate stimulated the proliferation of normal colonocytes and cancerous colonocytes when the Warburg effect was prevented from occurring.
TL;DR: It is established that epithelial KrasG12D influences multiple cell types to drive pancreatic tumorigenesis and is essential for tumor maintenance, and strongly support the notion that inhibiting Krasg12D, or its downstream effectors, could provide a new approach for the treatment of pancreatic cancer.
Abstract: Pancreatic cancer is almost invariably associated with mutations in the KRAS gene, most commonly KRASG12D, that result in a dominant-active form of the KRAS GTPase However, how KRAS mutations promote pancreatic carcinogenesis is not fully understood, and whether oncogenic KRAS is required for the maintenance of pancreatic cancer has not been established To address these questions, we generated two mouse models of pancreatic tumorigenesis: mice transgenic for inducible KrasG12D, which allows for inducible, pancreas-specific, and reversible expression of the oncogenic KrasG12D, with or without inactivation of one allele of the tumor suppressor gene p53 Here, we report that, early in tumorigenesis, induction of oncogenic KrasG12D reversibly altered normal epithelial differentiation following tissue damage, leading to precancerous lesions Inactivation of KrasG12D in established precursor lesions and during progression to cancer led to regression of the lesions, indicating that KrasG12D was required for tumor cell survival Strikingly, during all stages of carcinogenesis, KrasG12D upregulated Hedgehog signaling, inflammatory pathways, and several pathways known to mediate paracrine interactions between epithelial cells and their surrounding microenvironment, thus promoting formation and maintenance of the fibroinflammatory stroma that plays a pivotal role in pancreatic cancer Our data establish that epithelial KrasG12D influences multiple cell types to drive pancreatic tumorigenesis and is essential for tumor maintenance They also strongly support the notion that inhibiting KrasG12D, or its downstream effectors, could provide a new approach for the treatment of pancreatic cancer
TL;DR: It is described that IL-22BP has a crucial role in controlling tumorigenesis and epithelial cell proliferation in the colon in steady-state conditions and the IL- 22–IL-22 BP axis critically regulates intestinal tissue repair and tumorsigenesis in the Colon.
Abstract: Chronic mucosal inflammation and tissue damage predisposes patients to the development of colorectal cancer. This association could be explained by the hypothesis that the same factors and pathways important for wound healing also promote tumorigenesis. A sensor of tissue damage should induce these factors to promote tissue repair and regulate their action to prevent development of cancer. Interleukin 22 (IL-22), a cytokine of the IL-10 superfamily, has an important role in colonic epithelial cell repair, and its levels are increased in the blood and intestine of inflammatory bowel disease patients. This cytokine can be neutralized by the soluble IL-22 receptor, known as the IL-22 binding protein (IL-22BP, also known as IL22RA2); however, the significance of endogenous IL-22BP in vivo and the pathways that regulate this receptor are unknown. Here we describe that IL-22BP has a crucial role in controlling tumorigenesis and epithelial cell proliferation in the colon. IL-22BP is highly expressed by dendritic cells in the colon in steady-state conditions. Sensing of intestinal tissue damage via the NLRP3 or NLRP6 inflammasomes led to an IL-18-dependent downregulation of IL-22BP, thereby increasing the ratio of IL-22/IL-22BP. IL-22, which is induced during intestinal tissue damage, exerted protective properties during the peak of damage, but promoted tumour development if uncontrolled during the recovery phase. Thus, the IL-22-IL-22BP axis critically regulates intestinal tissue repair and tumorigenesis in the colon.
TL;DR: Recent advances in the studies of the relation between oxidative stress, lipid peroxidation products, and cancer progression are focused on, with particular attention to the pro-oxidant anticancer agents and the drug-resistant mechanisms, which could be modulated to obtain a better response to cancer therapy.
Abstract: The generation of reactive oxygen species (ROS) and an altered redox status are common biochemical aspects in cancer cells. ROS can react with the polyunsaturated fatty acids of lipid membranes and induce lipid peroxidation. The end products of lipid peroxidation, 4-hydroxynonenal (HNE), have been considered to be a second messenger of oxidative stress. Beyond ROS involvement in carcinogenesis, increased ROS level can inhibit tumor cell growth. Indeed, in tumors in advanced stages, a further increase of oxidative stress, such as that occurs when using several anticancer drugs and radiation therapy, can overcome the antioxidant defenses of cancer cells and drive them to apoptosis. High concentrations of HNE can also induce apoptosis in cancer cells. However, some cells escape the apoptosis induced by chemical or radiation therapy through the adaptation to intrinsic oxidative stress which confers drug resistance. This paper is focused on recent advances in the studies of the relation between oxidative stress, lipid peroxidation products, and cancer progression with particular attention to the pro-oxidant anticancer agents and the drug-resistant mechanisms, which could be modulated to obtain a better response to cancer therapy.
TL;DR: It is proposed that widespread DNA methylation changes in cancer are linked to silencing programs orchestrated by the three-dimensional organization of chromatin within the nucleus.
Abstract: Extensive changes in DNA methylation are common in cancer and may contribute to oncogenesis through transcriptional silencing of tumor-suppressor genes1. Genome-scale studies have yielded important insights into these changes2, 3, 4, 5 but have focused on CpG islands or gene promoters. We used whole-genome bisulfite sequencing (bisulfite-seq) to comprehensively profile a primary human colorectal tumor and adjacent normal colon tissue at single-basepair resolution. Regions of focal hypermethylation in the tumor were located primarily at CpG islands and were concentrated within regions of long-range (>100 kb) hypomethylation. These hypomethylated domains covered nearly half of the genome and coincided with late replication and attachment to the nuclear lamina in human cell lines. We confirmed the confluence of hypermethylation and hypomethylation within these domains in 25 diverse colorectal tumors and matched adjacent tissue. We propose that widespread DNA methylation changes in cancer are linked to silencing programs orchestrated by the three-dimensional organization of chromatin within the nucleus.
TL;DR: In this paper, the authors identify an HSF1-regulated transcriptional program specific to highly malignant cells and distinct from heat shock, which supports oncogenic processes: cell-cycle regulation, signaling, metabolism, adhesion and translation.
TL;DR: ROS act as a double-edged sword, similar to tumor necrosis factor-α, inflammation, and NF-κB, which provides a great challenge for researchers whose aim is to exploit ROS stress for the development of cancer therapies.
Abstract: Significance: Extensive research during the last quarter century has revealed that reactive oxygen species (ROS) produced in the body, primarily by the mitochondria, play a major role in various cell-signaling pathways. Most risk factors associated with chronic diseases (e.g., cancer), such as stress, tobacco, environmental pollutants, radiation, viral infection, diet, and bacterial infection, interact with cells through the generation of ROS. Recent Advances: ROS, in turn, activate various transcription factors (e.g., nuclear factor kappa-light-chain-enhancer of activated B cells [NF-κB], activator protein-1, hypoxia-inducible factor-1α, and signal transducer and activator of transcription 3), resulting in the expression of proteins that control inflammation, cellular transformation, tumor cell survival, tumor cell proliferation and invasion, angiogenesis, and metastasis. Paradoxically, ROS also control the expression of various tumor suppressor genes (p53, Rb, and PTEN). Similarly, γ-radiation and various chemotherapeutic agents used to treat cancer mediate their effects through the production of ROS. Interestingly, ROS have also been implicated in the chemopreventive and anti-tumor action of nutraceuticals derived from fruits, vegetables, spices, and other natural products used in traditional medicine. Critical Issues: These statements suggest both “upside” (cancer-suppressing) and “downside” (cancer-promoting) actions of the ROS. Thus, similar to tumor necrosis factor-α, inflammation, and NF-κB, ROS act as a double-edged sword. This paradox provides a great challenge for researchers whose aim is to exploit ROS stress for the development of cancer therapies. Future Directions: The various mechanisms by which ROS mediate paradoxical effects are discussed in this article. The outstanding questions and future directions raised by our current understanding are discussed. Antioxid. Redox Signal. 16, 1295–1322.
TL;DR: SIRT6 is identified as a tumor suppressor that regulates aerobic glycolysis in cancer cells and functions as a regulator of ribosome metabolism by corepressing MYC transcriptional activity, highlighting SIRT6 as a critical modulator of cancer metabolism.
TL;DR: Overexpression of GLDC and other glycine/serine enzymes, but not catalytically inactive GLDC, promotes cellular transformation and tumorigenesis, leading to changes in pyrimidine metabolism to regulate cancer cell proliferation.
TL;DR: The inhibition of inflammasomes or neutralization of their products, mainly interleukin 1β (IL-1β) and IL-18, has profound effects on carcinogenesis and tumor progression and is promising therapeutic targets in cancer-related clinical conditions.
Abstract: In the complex interplay between malignant cells and their microenvironment, caspase-1 activation complexes (inflammasomes) have contrasting roles. Inflammasomes may operate at the cell-autonomous level to eliminate malignant precursors through programmed cell death or, conversely, may stimulate the production of trophic factors for cancer cells and their stroma. In inflammatory cells, caspase-1 activation can fuel a cycle that leads to sterile inflammation and carcinogenesis, whereas in antigen-presenting cells, inflammasomes can stimulate anticancer immune responses. The inhibition of inflammasomes or neutralization of their products, mainly interleukin 1β (IL-1β) and IL-18, has profound effects on carcinogenesis and tumor progression. Thus, inflammasomes are promising therapeutic targets in cancer-related clinical conditions. Here we discuss present and future indications for the clinical use of inflammasome inhibitors.
01 Dec 2012
TL;DR: In this paper, the authors identify SIRT6 as a tumor suppressor that regulates aerobic glycolysis in cancer cells, and they show that deletion of SIRT 6 allele increases the number, size, and aggressiveness of tumors.
Abstract: Reprogramming of cellular metabolism is a key event during tumorigenesis. Despite being known for decades (Warburg effect), the molecular mechanisms regulating this switch remained unexplored. Here, we identify SIRT6 as a tumor suppressor that regulates aerobic glycolysis in cancer cells. Importantly, loss of SIRT6 leads to tumor formation without activation of known oncogenes, whereas transformed SIRT6-deficient cells display increased glycolysis and tumor growth, suggesting that SIRT6 plays a role in both establishment and maintenance of cancer. By using a conditional SIRT6 allele, we show that SIRT6 deletion in vivo increases the number, size, and aggressiveness of tumors. SIRT6 also functions as a regulator of ribosome metabolism by corepressing MYC transcriptional activity. Lastly, Sirt6 is selectively downregulated in several human cancers, and expression levels of SIRT6 predict prognosis and tumor-free survival rates, highlighting SIRT6 as a critical modulator of cancer metabolism. Our studies reveal SIRT6 to be a potent tumor suppressor acting to suppress cancer metabolism.