CD28 and neoplasm: VDR → restoration of exhausted CTLs phenotype, ↓expression of immune checkpoint inhibitors (PD-1, TIGIT, Tim-3) and ↑co-stimulatory molecule CD28 on CD8+ T cells → ↑cytokine production/anti-tumor immunityVDR-mediated Ca2+ influx → TCR activation → ↑Th1 cytokinesD-VDR signaling → ↑NK cytotoxic activityVDR → ↓Wnt-beta catenin signaling pathway → ↑tumor antigen release, antigen presentation, CD4+ T cell activation and priming, CTL and NK infiltration and tumor cell killing