RPS6KB1 and osteosarcoma: We hence performed Western Blot (WB) analysis to determine the phosphorylation level of the established mTORC1 substrate p70S6 kinase (p70-S6K), following exposure of human osteosarcoma U2OS cells, breast cancer MCF-7 cells as well as cervical cancer HeLa cells to siramesine and sunitinib.