MTOR and neoplasm: Although it may be considered a contradiction to accept that promoting cell survival in tumor cells would be warranted, studies in HL60 myeloid leukemia cells and in MCF-7 breast cancer cell lines indicate that activating autophagy pathways by the hormone, vitamin D, is important in exciting signaling pathways mediating the tumor-suppressive role of vitamin D. Vitamin D treatment of tumor cells seems to mediate upregulation of a protein known as beclin-1, which interacts with PI3 kinase (PI3K), which, in turn, inhibits mTOR, responsible for promoting tumor growth and progression.