The scientists began thinking in a new direction. Possibly rapamycin has the potential to protect HNSCC patients treated with radiation from developing the painful side effect of oral mucositis. The condition occurs because oral mucosal cells near the tumor absorb energy from the radiation beam and die. Among the collateral damage are the stem cells that naturally repopulate damaged tissue with healthy new cells. Without functioning stem cells, the wounds can be extremely slow to heal, and patients are at great risk of developing secondary infections and often have difficulty chewing and swallowing.
Follow-up animal studies confirmed their cell-culture surprise, including the survival of the stem cells. The researchers also drilled down deeper into the cell biology, finding that rapamycin likely protects against oxidative damage (which can cause cell senescence and death) via increased expression of the protein manganese superoxide dismutase, a mitochondrial enzyme that has been linked to radiation resistance.
(Source: NIDCR, Science News in Brief, January 16, 2013)