Fig. 1

MSC and tumour cell interaction in cancer progression. MSCs have been shown to interact with tumour cells at the primary site and during metastatic colonisation in a manner that promotes cancer progression. MSCs have been shown to promote EMT in tumour cells through direct cell-cell contact, which could in part be due to TGFβ secretion [38, 82]. Additionally, tumour cell secretion of osteopontin (OPN) was found to induce MSC secretion of chemokine (C-C motif) ligand 5 (CCL5) stimulating breast cancer cell metastasis through interaction with the C-C chemokine receptor type 5 (CCR5) receptor [84]. Tumour cell migration towards and entry into the bone marrow metastatic site was shown to be mediated by stromal cell-derived factor 1 (SDF-1α) – a factor secreted by bone marrow MSCs – interaction with the C-X-C chemokine receptor type 4 (CXCR4) receptor expressed on breast and prostate tumour cells [33, 102, 103]