GAS6 and neoplasm: Previous reports demonstrated a role for NF-kB in the regulation of MICA expression in different types of cells (e.g. T lymphocytes, endothelial cells and MM cells) (37, 38) NF-kB proteins are constitutively active in MM cells but BMSCs produce many soluble factors, including GAS6, which further trigger this signaling pathway in these tumor cells (16, 20, 39, 40).