IL6 and plasma cell myeloma: Besides direct cell-cell interactions, BMSCs and endothelial cells produce and secrete a variety of soluble factors such as interleukin 6 (IL-6), insulin-like growth factor-1 (IGF-1), vascular endothelial growth factor (VEGF) and fibroblast growth factor (FGF) that are all reportedly linked to myeloma progression and cancer cell dissemination.