Tumorigenesis is a clonal evolution process that is initiated from single cells within otherwise histologically normal tissue. It is unclear how single, sporadic mutant cells that have sustained oncogenic alterations evolve within a tightly regulated tissue environment. Here we investigated the effects of inducing oncogene expression in single cells in organotypic mammary acini as a model to elucidate the processes by which oncogenic alterations initiate clonal progression from organized epithelial environments. Sporadic cells induced to overexpress oncogenes that specifically perturb cell-cycle checkpoints (for example, E7 from human papilloma virus 16, and cyclin D1), deregulate Myc transcription or activate AKT signalling remained quiescent within growth-arrested acini. By contrast, single cells that overexpress ERBB2 initiated a cellular cascade involving cell translocation from the epithelial layer, as well as luminal outgrowth that is characteristic of neoplastic progression in early-stage epithelial tumours. In addition, ERBB2-mediated cell translocation to the lumen was found to depend on extracellular-regulated kinase and matrix metalloproteinase activities, and genetic alterations that perturb local cell-matrix adhesion drove cell translocation. We also provide evidence that luminal cell translocation may drive clonal selection by promoting either the death or the expansion of quiescent oncogene-expressing cells, depending on whether the pre-existing alterations allow anchorage-independent survival and growth. Our data show that the initial outgrowth of single oncogene-expressing cells from organized epithelial structures is a highly regulated process, and we propose that a cell translocation mechanism allows sporadic mutant cells to evade suppressive micro-environments and elicits clonal selection for survival and proliferative expansion outside the native niches of these cells.
HER2 is an oncogene, expression of which leads to poor prognosis in 30% of breast cancer patients. Although trastuzumab is apparently an effective therapy against HER2-positive tumors, its systemic toxicity and resistance in the majority of patients restricts its applicability. In this study we evaluated the effects of phenethyl isothiocyanate (PEITC) in HER2-positive breast cancer cells.
The most aggressive of four medulloblastoma (MB) subgroups are cMyc-driven group 3 (G3) tumors, some of which overexpress EZH2, the histone H3K27 mono-, di-, and trimethylase of polycomb-repressive complex 2. Ezh2 has a context-dependent role in different cancers as an oncogene or tumor suppressor and retards tumor progression in a mouse model of G3 MB. Engineered deletions of Ezh2 in G3 MBs by gene editing nucleases accelerated tumorigenesis, whereas Ezh2 re-expression reversed attendant histone modifications and slowed tumor progression. Candidate oncogenic drivers suppressed by Ezh2 included Gfi1, a proto-oncogene frequently activated in human G3 MBs. Gfi1 disruption antagonized the tumor-promoting effects of Ezh2 loss; conversely, Gfi1 overexpression collaborated with Myc to bypass effects of Trp53 inactivation in driving MB progression in primary cerebellar neuronal progenitors. Although negative regulation of Gfi1 by Ezh2 may restrain MB development, Gfi1 activation can bypass these effects.
We conducted the largest investigation of predisposition variants in cancer to date, discovering 853 pathogenic or likely pathogenic variants in 8% of 10,389 cases from 33 cancer types. Twenty-one genes showed single or cross-cancer associations, including novel associations of SDHA in melanoma and PALB2 in stomach adenocarcinoma. The 659 predisposition variants and 18 additional large deletions in tumor suppressors, including ATM, BRCA1, and NF1, showed low gene expression and frequent (43%) loss of heterozygosity or biallelic two-hit events. We also discovered 33 such variants in oncogenes, including missenses in MET, RET, and PTPN11 associated with high gene expression. We nominated 47 additional predisposition variants from prioritized VUSs supported by multiple evidences involving case-control frequency, loss of heterozygosity, expression effect, and co-localization with mutations and modified residues. Our integrative approach links rare predisposition variants to functional consequences, informing future guidelines of variant classification and germline genetic testing in cancer.
Autism spectrum disorder (ASD) is one phenotypic aspect of many monogenic, hereditary cancer syndromes. Pleiotropic effects of cancer genes on the autism phenotype could lead to repurposing of oncology medications to treat this increasingly prevalent neurodevelopmental condition for which there is currently no treatment. To explore this hypothesis we sought to discover whether autistic patients more often have rare coding, single-nucleotide variants within tumor suppressor and oncogenes and whether autistic patients are more often diagnosed with neoplasms. Exome-sequencing data from the ARRA Autism Sequencing Collaboration was compared to that of a control cohort from the Exome Variant Server database revealing that rare, coding variants within oncogenes were enriched for in the ARRA ASD cohort (p<1.0x10-8). In contrast, variants were not significantly enriched in tumor suppressor genes. Phenotypically, children and adults with ASD exhibited a protective effect against cancer, with a frequency of 1.3% vs. 3.9% (p<0.001), but the protective effect decreased with age. The odds ratio of neoplasm for those with ASD relative to controls was 0.06 (95% CI: 0.02, 0.19; p<0.0001) in the 0 to 14 age group; 0.35 (95% CI: 0.14, 0.87; p = 0.024) in the 15 to 29 age group; 0.41 (95% CI: 0.15, 1.17; p = 0.095) in the 30 to 54 age group; and 0.49 (95% CI: 0.14, 1.74; p = 0.267) in those 55 and older. Both males and females demonstrated the protective effect. These findings suggest that defects in cellular proliferation, and potentially senescence, might influence both autism and neoplasm, and already approved drugs targeting oncogenic pathways might also have therapeutic value for treating autism.
To review and discuss the available international literature regarding the indirect and direct biochemical mechanisms that occur after exercise, which could positively, or negatively, influence oncogenic pathways.
Human papillomavirus (HPV) initiates cervical cancer, and continuous expression of HPV oncogenes E6 and E7 is thought to be necessary to maintain malignant growth. Current therapies target proliferating cells, rather than specific pathways, and most experimental therapies specifically target E6/E7. We investigated the presence and expression of HPV in cervical cancer, to correlate HPV oncogene expression with clinical and molecular features of these tumors that may be relevant to new targeted therapies.
Gene fusions represent an important class of somatic alterations in cancer. We systematically investigated fusions in 9,624 tumors across 33 cancer types using multiple fusion calling tools. We identified a total of 25,664 fusions, with a 63% validation rate. Integration of gene expression, copy number, and fusion annotation data revealed that fusions involving oncogenes tend to exhibit increased expression, whereas fusions involving tumor suppressors have the opposite effect. For fusions involving kinases, we found 1,275 with an intact kinase domain, the proportion of which varied significantly across cancer types. Our study suggests that fusions drive the development of 16.5% of cancer cases and function as the sole driver in more than 1% of them. Finally, we identified druggable fusions involving genes such as TMPRSS2, RET, FGFR3, ALK, and ESR1 in 6.0% of cases, and we predicted immunogenic peptides, suggesting that fusions may provide leads for targeted drug and immune therapy.
The gene desert upstream of the MYC oncogene on chromosome 8q24 contains susceptibility loci for several major forms of human cancer. The region shows high conservation between human and mouse and contains multiple MYC enhancers that are activated in tumor cells. However, the role of this region in normal development has not been addressed. Here we show that a 538 kb deletion of the entire MYC upstream super-enhancer region in mice results in 50% to 80% decrease in Myc expression in multiple tissues. The mice are viable and show no overt phenotype. However, they are resistant to tumorigenesis, and most normal cells isolated from them grow slowly in culture. These results reveal that only cells whose MYC activity is increased by serum or oncogenic driver mutations depend on the 8q24 super-enhancer region, and indicate that targeting the activity of this element is a promising strategy of cancer chemoprevention and therapy.
The identification of driver oncogenes has provided important targets for drugs that can change the landscape of cancer therapies. One such example is the BRAF oncogene, which is found in about half of all melanomas as well as several other cancers. As a druggable kinase, oncogenic BRAF has become a crucial target of small-molecule drug discovery efforts. Following a rapid clinical development path, vemurafenib (Zelboraf; Plexxikon/Roche) was approved for the treatment of BRAF-mutated metastatic melanoma in the United States in August 2011 and the European Union in February 2012. This Review describes the underlying biology of BRAF, the technology used to identify vemurafenib and its clinical development milestones, along with future prospects based on lessons learned during its development.