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 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 downregulation of the large tumor suppressor homolog2 and the programmed cell death protein 4, 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. Stem Cells 2014;32:983–997

The role of NF-κB in the expression of inflammatory genes and its participation in the overall inflammatory process of chronic diseases and acute tissue injury are well established. We and others have demonstrated a critical involvement of poly(ADP-ribose) polymerase (PARP)-1 during inflammation, in part, through its relationship with NF-κB. However, the mechanism by which PARP-1 affects NF-κB activation has been elusive. In this study, we show that PARP-1 inhibition by gene knockout, knockdown, or pharmacologic blockade prevented p65 NF-κB nuclear translocation in smooth muscle cells upon TLR4 stimulation, NF-κB DNA-binding activity, and subsequent inducible NO synthase and ICAM-1 expression. Such defects were reversed by reconstitution of PARP-1 expression. PARP-1 was dispensable for LPS-induced IκBα phosphorylation and subsequent degradation but was required for p65 NF-κB phosphorylation. A perinuclear p65 NF-κB localization in LPS-treated PARP-1^−/− cells was associated with an export rather an import defect. Indeed, whereas PARP-1 deficiency did not alter expression of importin α3 and importin α4 and their cytosolic localization, the cytosolic levels of exportin (Crm)-1 were increased. Crm1 inhibition promoted p65 NF-κB nuclear accumulation as well as reversed LPS-induced p65 NF-κB phosphorylation and inducible NO synthase and ICAM-1 expression. Interestingly, p65 NF-κB poly(ADP-ribosyl)ation decreased its interaction with Crm1 in vitro. Pharmacologic inhibition of PARP-1 increased p65 NF-κB–Crm1 interaction in LPS-treated smooth muscle cells. These results suggest that p65 NF-κB poly(ADP-ribosyl)ation may be a critical determinant for the interaction with Crm1 and its nuclear retention upon TLR4 stimulation. These results provide novel insights into the mechanism by which PARP-1 promotes NF-κB nuclear retention, which ultimately can influence NF-κB–dependent gene regulation.

Membrane vesicles released by neoplastic cells into extracellular medium contain potential of carrying arrays of oncogenic molecules including proteins and microRNAs (miRNA). Extracellular (exosome-like) vesicles play a major role in cell-to-cell communication. Thus, the characterization of proteins and miRNAs of exosome-like vesicles is imperative in clarifying intercellular signaling as well as identifying disease markers.

African American men in the United States have higher mortality due to prostate cancer (PCa) compared to other races. One reason for this disparity is the lack of in-depth understanding of the PCa biology in African Americans. For example, hypoxia in prostate tumor microenvironment is associated with adverse prognosis; still, no hypoxia-related studies have been reported in African Americans. Here, we compared African-American and Caucasian PCa cells for exosome secretion under normoxic (21% O₂) and hypoxic (1% O₂) conditions. All cell lines showed higher exosome secretion under hypoxia but it was clearly more prominent in African-American PCa cells. Further, under hypoxia, Rab5 (a biomarker for early endosome) was clustered in perinuclear region; and CD63 (a biomarker for exosomes and multivesicular endosomes) showed greater co-localization with actin cytoskeleton especially in African American PCa cells. Importantly, exosome biogenesis inhibitors GW4869 (10–20 µM) or DMA (10–20 µg/ml) significantly decreased cell viability and clonogenicity in PCa cells. Interestingly, we also observed higher level of lactic acid loaded in exosomes secreted under hypoxia. Overall, under chronic hypoxia, PCa cells secrete more exosomes as a survival mechanism to remove metabolic waste.

Background ­— The present study was conducted to investigate the chemopreventive effects of garlic extract and silymarin on N-nitrosodiethylamine (NDEA) and carbon tetrachloride (CCl₄)-induced hepatotoxicity in male albino rats. Methods and Results — Animals were pretreated with garlic, silymarin or both for one week prior to the injection of NDEA. Then animals received a single injection of NDEA followed by weekly subcutaneous injections of CCl₄ for 6 weeks. Oral administration was then continued along with the injection of CCl₄ for the duration of the experiment. Serum aspartate transaminase (AST), alanine transaminase (ALT), alkaline phosphatase (ALP), hepatic lipid peroxidation (LPO), superoxide dismutase (SOD), reduced glutathione (GSH), glutathione-S-transferase (GST) and glutathione reductase (GSR) were measured. Injection of NDEA induced a significant elevation in serum AST, ALT and ALP. In the liver, NDEA increased oxidative stress through the increase in LPO and decrease in SOD, and GSH-dependent enzymes. Although administration of garlic or silymarin significantly reduced the liver toxicity, combined administration was more effective in preventing the development of hepatotoxicity. Conclusion — These novel findings suggest that silymarin and garlic have a synergistic effect, and could be used as hepatoprotective agents against hepatotoxicity.