p21 Regulates LC Radiation Resistance

Treatment with ionizing irradiation (IR) may lead to accumulation of tumor-infiltrating T regulatory (Treg) cells and subsequent tumor resistance to radiotherapy. Here we focused on the contribution of Langerhans cells (LCs) to this phenomenon because of their unique ability to resist depletion by high-dose IR. We found that LCs resisted apoptosis and rapidly repaired DNA damage post-IR. Particularly, we found that p21 was overexpressed in LCs, and that p21-deficient LCs underwent apoptosis and accumulated DNA damage following IR treatment. Wild-type, but not p21-deficient, LCs upregulated major histocompatibility complex class II molecules, migrated to the draining lymph nodes and increased Treg cell numbers upon exposure to IR. These findings suggest a means for manipulating LC IR-resistance to increase cutaneous tumor response to radiotherapy. See above Cells were purified by flow cytometry and pooled until >10,000 cells/sample. At least 2 replicates of each sample were submitted.