PDCD1 and nasopharyngeal carcinoma: In an MC38-derived murine tumor mass, CD8+ T cells expressing PD-1 have reduced Drp1 activities and longer mitochondria compared to their PD-1-negative counterparts, which may explain their reduced motility and proliferation.262 In hypoxic nasopharyngeal carcinoma microenvironments, mitochondrial fusion protein MFN1/2 expression is decreased, leading to small and fragmented mitochondria in TILs.263 It is affected due to increased expression of exosomal miR-24 in response to hypoxia, which inhibits its target gene Myc.