PTH1R and prostate neoplasm: We have previously demonstrated that prostate tumor-derived parathyroid hormone-related peptide (PTHrP) correlates with MDSC accumulation in prostate tumor tissues, a process that involves activation of the PTHrP receptor, PTH1R, in osteoblasts.19 Briefly, prostate tumor-derived PTHrP activates osteoblasts, the main cell type expressing PTH1R in the bone microenvironment, leading to the expression of vascular endothelial growth factor (VEGF)-A and IL6.