Dr. Sellers is a genetic epidemiologist with a primary interest in cancer of the ovaries, breast and lung and  of mammographic density, an image-based biomarker of breast cancer risk. This work has involved studies of extended families, siblings, and with advances in technology, the role of common genetic variation among unrelated individuals. Early work provided some of the first evidence that body fat distribution, rather than just obesity, was a risk factor for cancer. He has been the Principal or Co-Principal investigator on more than $100M in peer-reviewed grants, which have contributed to over 400 publications that have been cited over 46,000 times.

Prior to joining OHSU and the Knight Cancer Institute, Sellers was a professor at the Mayo Clinic College of Medicine, Associate Director, and then Deputy Director of the Mayo Clinic Comprehensive Cancer Center. He served as an Executive Vice President at the Moffitt Cancer Center, the Director of the Moffitt Research Institute, and Director of the NCI-Designated Comprehensive Cancer Center. Sellers was a member of NCI subcommittee A and has served on the External Advisory Boards of 25 Cancer Centers.

Sellers has provided extensive professional service, including the American Association for Cancer Research Board of Directors, the Association of American Cancer Institutes Board of Directors, the Cancer Prevention Research Institute of Texas, and the NCI Board of Scientific Counselors.