rhSTIP1 induced SAMD1/5 pathway

Stress-induced phosphoprotein 1 (STIP1), a co-chaperone that organizes other chaperones- heat shock proteins (HSP), was recently shown to be secreted by human ovarian cancer cells to induce cell proliferation. In neuronal tissues, binding to prion protein was required for STIP1 to activate the ERK (extracellular regulated MAP kinase) signaling pathways. However, in this study, we found that STIP1 stimulated cell proliferation of ovarian cancer via a bone morphogenetic protein (BMP) signaling pathway, not through the prion-ERK pathway. The STIP1 binding to a BMP receptor, ALK2 (activin A receptor, type II-like kinase 2), was necessary and sufficient to stimulate cancer cell proliferation. The binding of STIP1 to ALK2 activated the SMAD signaling pathway, leading to transcriptional activation of ID3 (inhibitor of DNA binding 3) that promotes cell proliferation. In conclusion, ovarian cancer tissues secrete STIP1 into the local environment and eventually into blood circulation of patients. In an autocrine and/or paracrine fashion, secreted STIP1 stimulates cancer cell proliferation by binding to ALK2 and activating the SMAD-ID3 signaling pathways. Elucidation of the mechanism by which STIP1 stimulates cancer cell proliferation may pave the way for developing novel therapeutic strategies for treatment of ovarian cancer. SKOV3 cell,treated without rhSTIP1 SKOV3 cell,treated with rhSTIP1 SKOV3 cell,treated without rhSTIP1-2 SKOV3 cell,treated with rhSTIP1-2