IL6 and neoplasm: One plausible host stromal candidate could include mast cell-derived interleukin-6, which we have previously implicated in a positive feedback cycle between tumor cells and host myofibroblasts in MDA-MB-468 xenografts [100], although other soluble factors, microRNAs, and exosomes have been found to be released from tumor-activated stromal cells to promote EMT (reviewed in [101]).