CXCR4 and sarcoma: Moreover, BM stromal cells produce numerous cytokines including CXCL12/CXCR4 (C-X-C motif chemokine 12/C-X-C chemokine receptor type 4) signaling, RAS (Rat sarcoma) kinases, and PI3K/AKT/ mTOR (mammalian target of rapamycin) that seem to play a major role providing the activation of survival pathways that bypass FLT3 receptor [32].