Comparative analysis of DNA damage and repair capacity in dogs to improve cancer risk prediction

Project Summary/Abstract Dogs have a higher incidence of cancer than humans (8041 versus 457.52 per 100,000 dog- or person-years), and accumulate somatic mutations much more quickly than humans do (as somatic mutation rates scale with lifespan)3. The mechanism(s) of this higher cancer predisposition and faster rate of somatic mutation are not yet known. Dogs are an important biomedical model for human cancers, and are leveraged in precision oncology studies, preclinical drug development, and as environmental sentinels of genotoxic exposures. Elucidation of the mechanism of increased somatic mutation will improve the utility of the dog as a cancer model and environmental sentinel, and help to lay the foundation for leveraging canine cancers to develop precision cancer risk prediction in people and understanding factors that modulate cancer risk. This study explores the hypothesis that the increased rate of somatic mutation arises via contributions from: (1) increased exposure to endogenous or exogenous genotoxins causing DNA damage; (2) deficiencies in DNA damage repair capacity (DCR); or (3) failure of cells with somatic mutations to undergo apoptosis. To distinguish among these possibilities, I will test normal primary T-lymphocytes isolated from both healthy dogs and dogs with T-cell lymphoma. Cells will be placed in primary culture and T-lymphocytes stimulated using established protocols in routine use in my mentors’ labs. In each of the analyses described below, I will compare findings between dogs with and without lymphoma, quantify variation between and within individuals and breeds, and compare findings to published human data. This study also provides a comprehensive training plan allowing me to: gain expertise in functional DNA damage assays including CometChip and FM-HCR; become proficient in cell isolation and cell culture techniques; learn to sort and analyze cells via flow cytometry; extend my genomics expertise to include somatic variant detection in normal tissues, gain expertise in DNA damage repair mechanisms and environmental health; and broaden my experience as mentor and teacher. By elucidating the mechanisms behind increased somatic mutation in dogs, as well as characterizing DNA damage repair kinetics and the somatic mutational landscape of normal canine cells, this work will make crucial contributions to our understanding and leveraging of dogs as a model for human cancers. In addition, the proposed training program, under the supervision of a team of outstanding mentors, will enable me to augment my computational genomics skills with powerful wet lab and novel sequencing techniques, positioning me for a successful career as an independent biomedical scientist.