Time to Think Outside the (Genetic) Box

Abstract

Many patients develop cancers that have clinical features of inherited syndromes (e.g., young age of onset and unique pathology) but lack mutations in the genes characteristic of the disease. In this issue of the journal, Wong et al. report that somatic epigenetic inactivation could explain some such cases in the setting of BRCA1-associated breast cancer. Here, we discuss the implications of this work in terms of the etiology, risk, and potential prevention of cancer. Cancer Prev Res; 4(1); 6-8. Ó2011 AACR.Identification of high-risk populations is a research priority in cancer prevention. Genetic predisposition to cancer development is an obvious marker for risk, and several interventions have been shown to reduce cancer mortality in this group of patients. It remains puzzling, however, that despite more than 2 decades of research into mutations in the genes most commonly responsible for inherited cancer, such mutations are not found in a large number of cases that share clinical criteria for having inherited cancer (young age at onset, specific pathology, etc.; ref. 1). For many years, this absence of mutations was easy to explain away-our knowledge of cancer genetics was thought to be fragmentary, and these puzzling cases were assumed to carry mutations in genes yet to be identified. However, large-scale sequencing efforts in major human malignancies such as colorectal cancer (2) have not uncovered previously unknown high-frequency mutations. We are left, therefore, with the somewhat unsatisfying hypothesis that rare mutations in multiple genes or a combination of alterations in several genes that act collectively underlie the many cases of inherited cancer with no known cancerassociated mutation.In this issue of the journal, Wong et al. (3) present data supporting an alternative concept: that is, constitutional epigenetic defects can account for a significant proportion of cancers with the clinical/pathologic features but not the characteristic mutations of inherited cancers. This study was conducted in 255 female breast cancer patients without an identified germline BRCA1 (or BRCA2) mutation and 169 age-matched female controls. The breast cancers in the cases were required to share certain features of inherited BRCA1-associated disease [onset at a young patient age (<40 years), and aggressive pathology). The patients were assessed for 9 tumor pathology features deemed to be characteristic of cancers in BRCA1 mutation carriers and then were divided into 3 groups, as follows: 5 or more characteristic features (group 1), 4 features (group 2), and 3 or fewer features (group 3). Thirty-one percent of the patients with the most BRCA1-like tumors (group 1) had detectable BRCA1 methylation in peripheral bloodderived DNA, and the cancers themselves had high levels of BRCA1 methylation. The frequency of peripheral blood BRCA1 methylation was much lower (5%) in patients whose cancers had fewer BRCA1 features (group 3), and the non-BRCA1-like cancers themselves had low levels of BRCA1 methylation. There was an ...

Genome-wide profiles of CtBP link metabolism with genome stability and epithelial reprogramming in breast cancer

“…It is striking that, of the known and newly identified breast cancer predisposing genetic mutations, a substantial number are targeted for repression by CtBP, including PALB2 , BRIP1 , RAD51C and BRCA1 16 . Thus the observation that many patients develop breast cancers with features of inherited disease without demonstrating mutation in genes characteristic of the disease 51 , is consistent with a role played by CtBP-regulated pathways in such tumors. Notably, decreased expression specifically of DNA repair proteins is associated with shortened time to recurrence in triple-negative breast cancer 52 .…”

Peripheral blood DNA methylation profiles are indicative of head and neck squamous cell carcinoma: An epigenome-wide association study

“…It is possible that certain of these may predispose individuals to HNSCC. 38,39 While it is known that some epimutations are high-penetrance and have a very dramatic phenotype, 39,40 it is also common for them to exhibit mosaicism and have a phenotype that is more complex. Going forward, the most important test of this hypothesis could come from prospective studies that can assess whether these profiles are present at times that predate disease diagnosis.…”

Perspective: The big C — for Chemoprevention

“…We need further studies on the importance of epigenetics 10 and the tumour microenvironment 8 to develop chemopreventive drugs. The tumour microenvironment, with all of its stromal and inflammatory cells, is an essential part of a carcinoma.…”

“…The tumour microenvironment, with all of its stromal and inflammatory cells, is an essential part of a carcinoma. Major advances over the past decade in these areas are leading to the development of important new drugs for cancer prevention 8,10 .…”