Identifying genomic alterations driving breast cancer is complicated by tumor diversity and genetic heterogeneity. Relevant mouse models are powerful for untangling this problem because such heterogeneity can be controlled. Inbred Chaos3 mice exhibit high levels of genomic instability leading to mammary tumors that have tumor gene expression profiles closely resembling mature human mammary luminal cell signatures. We genomically characterized mammary adenocarcinomas from these mice to identify cancer-causing genomic events that overlap common alterations in human breast cancer. Chaos3 tumors underwent recurrent copy number alterations (CNAs), particularly deletion of the RAS inhibitor Neurofibromin 1 (Nf1) in nearly all cases. These overlap with human CNAs including NF1, which is deleted or mutated in 27.7% of all breast carcinomas. Chaos3 mammary tumor cells exhibit RAS hyperactivation and increased sensitivity to RAS pathway inhibitors. These results indicate that spontaneous NF1 loss can drive breast cancer. This should be informative for treatment of the significant fraction of patients whose tumors bear NF1 mutations.
"NF1 is located on the pericentromeric region of the long arm of chromosome 17 (which interestingly also houses the BRCA1 gene), and regulates the conversion of the active Ras-GTP to inactive Ras-GDP (Figure 4) . About 28% of sporadic breast cancers in humans are missing at least one copy of NF1 gene, either due to deletion or mutation . "
[Show abstract][Hide abstract] ABSTRACT: The association of neurofibromatosis type I with invasive male breast cancer is a rare clinical entity with only one case in literature reported in 1953. Women with NF1 are at risk of developing breast cancer and men also may be at risk but there is scarce data on the risk and association of NF1 with male breast cancer due to its rarity. Established clinical trials in male breast cancer patients are lacking and the results are extrapolated from female breast cancer patients. The treatment of male breast cancer is followed as per the guidelines of premenopausal female breast cancer and tamoxifen is the hormone treatment in them. Mendes et al suggests that silencing of NF1 gene confers resistance to tamoxifen. Our conclusions are that since NF1 is mutated or deleted in one third of sporadic breast cancers, its role as a molecular driver for treatment has to be further explored.
Hereditary Cancer in Clinical Practice 02/2014; 12(1):5. DOI:10.1186/1897-4287-12-5 · 1.47 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The identification of cancer drivers is a major goal of current cancer research. Finding driver genes within large chromosomal events is especially challenging because such alterations encompass many genes. Previously, we demonstrated that zebrafish malignant peripheral nerve sheath tumors (MPNSTs) are highly aneuploid, much like human tumors. In this study, we examined 147 zebrafish MPNSTs by massively parallel sequencing and identified both large and focal copy number alterations (CNAs). Given the low degree of conserved synteny between fish and mammals, we reasoned that comparative analyses of CNAs from fish versus human MPNSTs would enable elimination of a large proportion of passenger mutations, especially on large CNAs. We established a list of orthologous genes between human and zebrafish, which includes approximately two-thirds of human protein-coding genes. For the subset of these genes found in human MPNST CNAs, only one quarter of their orthologues were co-gained or co-lost in zebrafish, dramatically narrowing the list of candidate cancer drivers for both focal and large CNAs. We conclude that zebrafish-human comparative analysis represents a powerful, and broadly applicable, tool to enrich for evolutionarily conserved cancer drivers.
[Show abstract][Hide abstract] ABSTRACT: Defective DNA replication can result in genomic instability, cancer and developmental defects. To understand the roles of DNA damage response (DDR) genes on carcinogenesis in mutants defective for core DNA replication components, we utilized the Mcm4(Chaos3/Chaos3) ('Chaos3') mouse model that, by virtue of an amino-acid alteration in MCM4 that destabilizes the MCM2-7 DNA replicative helicase, has fewer dormant replication origins and an increased number of stalled replication forks. This leads to genomic instability and cancer in most Chaos3 mice. We found that animals doubly mutant for Chaos3 and components of the ataxia telangiectasia-mutated (ATM) double-strand break response pathway (Atm, p21/Cdkn1a and Chk2/Chek2) had decreased tumor latency and/or increased tumor susceptibility. Tumor latency and susceptibility differed between genetic backgrounds and genders, with females demonstrating an overall greater cancer susceptibility to Atm and p21 deficiency than males. Atm deficiency was semilethal in the Chaos3 background and impaired embryonic fibroblast proliferation, suggesting that ATM drug inhibitors might be useful against tumors with DNA replication defects. Hypomorphism for the 9-1-1 component Hus1 did not affect tumor latency or susceptibility in Chaos3 animals, and tumors in these mice did not exhibit impaired ATR pathway signaling. These and other data indicate that under conditions of systemic replication stress, the ATM pathway is particularly important both for cancer suppression and viability during development.Oncogene advance online publication, 26 August 2013; doi:10.1038/onc.2013.339.
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