Norman “Ned” Sharpless, M.D., former director of the University of North Carolina (UNC) Lineberger Comprehensive Cancer Center in Chapel Hill, was sworn in Oct. 17 as the new director of the National Cancer Institute (NCI) at the National Institutes of Health (NIH).
NIH Director Francis Collins, M.D., Ph.D., announced the appointment of Sharpless. “His insight, influence, and partnership will be critical for advancing cancer research at a time of unprecedented rapid progress,” Collins said. As NCI director, Sharpless will oversee the full range of the institute’s programs.
On Aug. 7, before his final appointment, Sharpless delivered a talk at NIEHS on interactions between cancer and aging. Scientists at NIEHS who conduct or fund studies of cancer and potential environmental contributors attended, including NIEHS and National Toxicology Program Director Linda Birnbaum, Ph.D., who was the host.
Accumulation of cells that do not divide
Chemotherapy cures some cancers, Sharpless noted, but one side effect in certain people is that it also may accelerate aging. One way is through the accumulation of senescent cells. These cells have lost the ability to divide and no longer function properly.
Senescent cells, which naturally accumulate as we age, have some benefits — like tumor suppression and wound healing. But they also add to aging by not replicating, clogging up normal processes, and promoting inflammation. Sharpless suggested that although chemotherapy generally increases the burden of senescent cells, levels may vary among individuals.
Researchers are pursuing a reliable way to measure senescence as a marker of aging. One promising approach is to measure expression of a gene called p16, which codes for a protein that cells make only when damaged. They are also testing whether senolysis, or removing senescent cells, may benefit health, especially after chemotherapy.
Loss of functional stem cells
The second way chemotherapy may induce aging, according to Sharpless, is by hampering the normal function of cells that produce new red and white blood cells to carry oxygen and fight infection, respectively.
Forced regeneration of these cells through multiple rounds of chemotherapy causes stem cell exhaustion. Over time, stem cell exhaustion produces a state similar to normal aging. Research is underway on new treatments that would selectively promote production of the most needed blood cells, while minimizing excessive regeneration.
(Virginia Guidry, Ph.D., is a technical writer and public information specialist in the NIEHS Office of Communications and Public Liaison and a regular contributor to the Environmental Factor.)