Emerging evidence suggests that mesenchymal stem cells (MSCs) are often recruited to tumor sites but their functional significance in tumor growth and disease progression remains elusive. Herein we report that prostate cancer (PC) cell microenvironment subverts PC patient adipose-derived stem cells (pASCs) to undergo neoplastic transformation. Unlike normal ASCs, the pASCs primed with PC cell conditioned media (CM) formed prostate-like neoplastic lesions in vivo and reproduced aggressive tumors in secondary recipients. The pASC tumors acquired cytogenetic aberrations and mesenchymal-to-epithelial transition (MET) and expressed epithelial, neoplastic, and vasculogenic markers reminiscent of molecular features of PC tumor xenografts. Our mechanistic studies revealed that PC cell-derived exosomes are sufficient to recapitulate formation of prostate tumorigenic mimicry generated by CM-primed pASCs in vivo. In addition to down-regulation of the large tumor suppressor homolog2 (Lats2) and the programmed cell death protein 4 (PDCD4), a neoplastic transformation inhibitor, the tumorigenic reprogramming of pASCs was associated with trafficking by PC cell-derived exosomes of oncogenic factors, including H-ras and K-ras transcripts, oncomiRNAs miR-125b, miR-130b, and miR-155 as well as the Ras superfamily of GTPases Rab1a, Rab1b, and Rab11a. Our findings implicate a new role for PC cell-derived exosomes in clonal expansion of tumors through neoplastic reprogramming of tumor tropic ASCs in cancer patients.

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Purpose: The causes of disproportionate incidence and mortality of prostate cancer among African Americans (AA) remain elusive. The purpose of this study was to investigate the mechanistic role and assess clinical utility of the splicing factor heterogeneous nuclear ribonucleoprotein H1 (hnRNP H1) in prostate cancer progression among AA men.Experimental Design: We employed an unbiased functional genomics approach coupled with suppressive subtractive hybridization (SSH) and custom cDNA microarrays to identify differentially expressed genes in microdissected tumors procured from age-and tumor grade-matched AA and Caucasian American (CA) men. Validation analysis was performed in independent cohorts and tissue microarrays. The underlying mechanisms of hnRNPH1 regulation and its impact on androgen receptor (AR) expression and tumor progression were explored.Results: Aberrant coexpression of AR and hnRNPH1 and downregulation of miR-212 were detected in prostate tumors and correlate with disease progression in AA men compared with CA men. Ectopic expression of miR-212 mimics downregulated hnRNPH1 transcripts, which in turn reduced expression of AR and its splice variant AR-V7 (or AR3) in prostate cancer cells. hnRNPH1 physically interacts with AR and steroid receptor coactivator-3 (SRC-3) and primes activation of androgen-regulated genes in a ligand-dependent and independent manner. siRNA silencing of hnRNPH1 sensitized prostate cancer cells to bicalutamide and inhibited prostate tumorigenesis in vivo.Conclusions: Our findings define novel roles for hnRNPH1 as a putative oncogene, splicing factor, and an auxiliary AR coregulator. Targeted disruption of the hnRNPH1-AR axis may have therapeutic implications to improve clinical outcomes in patients with advanced prostate cancer, especially among AA men.