BIRC5 and squamous cell carcinoma: The findings indicate that calcitriol and its derivative 22-oxa-1,25(OH)2D3 suppress cell proliferation, induce apoptosis, and arrest the cell cycle; they also increase the sensitivity of chemotherapeutics and downregulate several angiogenesis factors and pro-apoptotic survivin in KB cell lines of oral floor squamous cell carcinoma.