TGM2 and melanoma: A number of extranuclear and intranuclear factors have been identified to influence the radiation responsiveness of melanoma cells, including breast cancer 1, early onset (BRCA1), excision repair cross-complementing rodent repair deficiency, complementation group 1 (ERCC1), poly(ADP-ribose) polymerase (PARP), transglutaminase 2 (TGM2) and SLUG, as well as chromosomal characteristics, such as telomere length (8,9).