Somatic Mutation Rate, Genomic Instability, and Clonal Evolution in BRCA1/2 Carriers Undergoing Prophylactic Risk-Reducing Surgery to Establish Serous Tubular Intraepithelial Lesions (STILs) as Cancer

Our proposed research will address the priority of the Department of Defense Ovarian Cancer Research Program to 'Understand the precursor lesion/stem cell, microenvironment, and pathogenesis/progression of all types of ovarian cancer, including rare subtypes.' The ultimate goal of our study is to determine the sequence of changes in the DNA of precancer cells that leads to ovarian cancer in women with Breast Cancer gene 1 and 2 (BRCA1/2) mutations, the most commonly inherited genetic disorders that lead to ovarian cancer. The results of the project will answer critical questions of how these mutations modulate ovarian cancer risk. Cancers usually begin as individual cells that grow and divide in an uncontrolled fashion to produce tumors. Up until the past few years, it was unclear where in the pelvic area ovarian cancers originated. Recent evidence suggests that most ovarian cancers develop in the fallopian tube rather than the ovary, contrary to what was previously assumed. Our study aims to demonstrate that ovarian cancer begins with small groups of cells called serous tubular intraepithelial lesions (STILs) at the end of the fallopian tube that grow into early microscopic tumors called serous tubular intraepithelial carcinomas (STICs). The mechanism by which these transformed cells produce ovarian tumors remains unknown, but one possibility is that the ends of the fallopian tubes (fimbriae), which help guide the egg through the fallopian tube, can deposit these transformed cells on the ovaries due to the close proximity of these two structures. While some genetic research supports the argument that STICs are precursors to ovarian cancer, the details of the transformation from precancerous STILs to ovarian tumors are unknown. Likewise, the genes responsible for this process and how they become damaged in premalignant cells remains unknown. This represents a huge gap of knowledge in carcinogenesis theory that precludes development of early intervention strategies that are available for other cancer types such as colon cancer. A major limitation in addressing this knowledge gap is that methods normally used to study the cancer cell genome cannot be applied to study premalignant cells. This is because, unlike tumors, where most cells carry the same mutation (which makes them easier to identify), pre-tumor cells contain unique genomic changes that can only be studied only in individual, single cells using new technologies. Dr. Cristina Montagna and her collaborators at the Albert Einstein College of Medicine and Montefiore Medical Center have recently developed novel single-cell genomic analysis techniques, and here they propose to make use of these methods to study genomic changes in STILs and STICs and how these genomic changes result in progression to ovarian cancer. To carry out this study, we will study cells from STILs and STICs of women with mutations in BRCA1/2. Over time, DNA in human cells is exposed to toxins, causing damage in the genome called mutations. While these mutations are usually repaired by proteins that fix damaged DNA, women with BRCA1/2 mutations are fully or partially unable to repair DNA. Over time, genomic mutations in these women may accumulate in a process termed 'genomic instability.' Although there is some evidence that STILs and STICs have increased genomic instability, this theory has not been proven at the molecular level due to a lack of sufficient technology. We now have the necessary technology to determine if an increase in the degree of genomic instability (and thus in the degree of mutations) occurs between normal fallopian tubes, STILs, STICs, and ultimately cancer. Using the novel technologies we have developed, we will clarify the sequence of events that ultimately may lead to cancer in women with BRCA1/2 mutations. The findings of our work will help improve care for women with BRCA1/2 mutations, as there are currently no good ways to prevent ovarian c