IL21 and melanoma: Moreover, overexpression of 6 kDa early secreted antigenic target (ESAT-6), a glycosylphosphatidylinositol (GPI)-anchored form and secreted interleukin (IL)-21 in B16F10 CD133+CD44+ CSCs leads to activation of anti-ESAT-6 and interferon (IFN)-γ correlates with enhanced anti-melanoma efficacy and prolonged survival of melanoma bearing mice [53].