PTHLH and Familial prostate cancer: We have previously demonstrated that prostate cancer-derived PTHrP induces activating phosphorylation of Src family kinase (SFK) at tyrosine residue 419 (Y419) in MDSCs via vascular endothelial growth factor (VEGF)-A and interleukin (IL)-6 expressed by osteoblasts, leading to increased proangiogenic and protumorigenic functions of MDSCs.19 We subsequently tested whether SFK activation also plays a role in M-MDSC mobilization.