MBTPS1 and prostate cancer: To extend our in vitro findings, and because the anti-S1P mAb we used is under clinical development, the antibody's ability to inhibit HIF-1α accumulation and transcriptional activity in vivo was tested in an orthotopic model of prostate cancer using the PC-3 cell line, because hypoxic response is largely dependent on the vascular microenvironment and very poorly replicated in subcutaneous models [55].