Incidence of skeletal metastases and death from prostate cancer greatly increases with age and obesity, conditions which increase marrow adiposity. Bone marrow adipocytes are metabolically active components of bone metastatic niche that modulate the function of neighboring cells; yet the mechanisms of their involvement in tumor behavior in bone have not been explored. In this study, using experimental models of intraosseous tumor growth and diet-induced obesity, we demonstrate the promoting effects of marrow fat on growth and progression of skeletal prostate tumors. We reveal that exposure to lipids supplied by marrow adipocytes induces expression of lipid chaperone FABP4, pro-inflammatory interleukin IL-1β, and oxidative stress protein HMOX-1 in metastatic tumor cells and stimulates their growth and invasiveness. We show that FABP4 is highly overexpressed in prostate skeletal tumors from obese mice and in bone metastasis samples from prostate cancer patients. In addition, we provide results suggestive of bi-directional interaction between FABP4 and PPARγ pathways that may be driving aggressive tumor cell behavior in bone. Together, our data provide evidence for functional relationship between bone marrow adiposity and metastatic prostate cancers and unravel the FABP4/IL-1β axis as a potential therapeutic target for this presently incurable disease.

TMPRSS2-Ets gene fusions were identified in prostate cancers where the promoter of transmembrane protease, serine 2 (TMPRSS2) fused with coding sequence of the erythroblastosis virus E26 (Ets) gene family members. TMPRSS2 is an androgen responsive transmembrane serine protease. Ets family members are oncogenic transcription factors that contain a highly conserved Ets DNA binding domain and an N-terminal regulatory domain. Fusion of these gene results in androgen dependent transcription of Ets factor in prostate tumor cells. The ERG is the most common fusion partner with TMPRSS2 promoter in prostate cancer patients. The high prevalence of these gene fusions, in particular TMPRSS2-ERG, makes them attractive as potential diagnostic and prognostic indicators, as well as making them a potential target for tailored therapies. This review focuses on the clinical and biological significance of TMPRSS2-ERG fusions and their role in PC development and progression.

Purpose Intratumoral androgen synthesis in prostate cancer (PCa) contributes to the development of castration-resistant prostate cancer (CRPC). Several enzymes responsible for androgen biosynthesis have been shown to be overexpressed in CRPC, thus contributing to CRPC in a castrated environment. The TMPRSS2-ERG transcription factor has been shown to be present in primary PCa tumors as well as CRPC tumors. We hypothesize that TMPRSS2-ERG fusions regulate androgen biosynthetic enzyme (ABE) gene expression and the production of androgens, which contributes to the development of CRPC. Experimental design We used a panel of assays including lentivirus transduction, gene expression, chromatin immunoprecipitation and sequencing, Liquid chromatography-Mass spectrometric quantitation, immunocytochemistry, immunohistochemistry and bio-informatics analysis of gene microarray data bases to determine ERG regulation of androgen synthesis. Results We found that ERG regulated the expression of the ABE AKR1C3 in PCa cells via direct binding to the AKR1C3 gene. Knockdown of ERG resulted in reduced AKR1C3 expression, which caused a reduction in both DHT synthesis and PSA expression in VCaP PCa cells treated with 5α-androstanedione, a DHT precursor metabolite. Immunohistochemical staining revealed that ERG was co-expressed with AKR1C3 in PCa tissue samples. Conclusions These data suggest that AKR1C3 catalyzes the biochemical reduction of 5α-Androstanedione to DHT in PCa cells, and that ERG regulates this step through upregulation of AKR1C3 expression. Elucidation of ERG regulation of ABEs in CRPC may help to stratify TMPRSS2-ERG fusion-positive PCa patients in the clinic for anti-AR driven therapies; and AKR1C3 may serve as a valuable therapeutic target in the treatment of CRPC.

Gene-targeted deletion of the predominant Shaker potassium channel, Kv1.3, in the mitral cells of the olfactory bulb, decreases the number of presynaptic, odorant receptor (OR)-identified olfactory sensory neurons (OSNs) in the main olfactory epithelium (MOE) and alters the nature of their postsynaptic connections to mitral cell targets. The current study examined whether OSN density was state-dependent by examining the impact of 1) odor enrichment, 2) sensory deprivation, and 3) aging upon the number of P2- or M72-expressing neurons. Histological approaches were used to quantify the number of OSNs across entire epithelia for wildtype (WT) vs. Kv1.3-null (KO) mice bred onto an ORtauLacZ reporter background. Following either odor-enrichment or early unilateral naris-occlusion, the number of M72-expressing OSNs was significantly decreased in WT mice, but was unchanged in KO animals. Following naris-occlusion, the number of P2-expressing OSNs was decreased regardless of genotype. Animals that were reared to 2 years of age demonstrated loss of both P2- and M72-expressing OSNs in WT mice and a concomitant loss of only M72-expressing neurons in KO mice. These findings suggest that voltage-gated activity of the mitral cells is important for OSN plasticity, and can prevent neuronal loss via sensory- and OR-dependent mechanisms.

CXCR4 is a chemokine receptor that mediates invasion and metastasis. CXCR4 expression is transcriptionally regulated in cancer cells and is associated with aggressive phenotypes of prostate cancer. Previously, we and others have shown that the ERG transcription factor regulates CXCR4 expression in prostate cancer cells. We further showed that androgens regulate CXCR4 expression via increasing ERG transcription factor expression. Herein, we investigated molecular mechanisms of ERG-mediated CXCR4 promoter activation, phosphorylation of ERG by intracellular kinases and subsequent CXCR4 expression, as well as expression of ERG and CXCR4 in human prostate tumor tissues. Using multiple molecular strategies, we demonstrate that: (a) ERG expressed in TMPRSS2-ERG fusion positive VCaP cells selectively binds with specific ERG/Ets bindings sites in the CXCR4 promoter; (b) distal binding sites mediate promoter activation; (c) exogenously expressed ERG promotes CXCR4 expression; (d) ERG is phosphorylated at Serine 81 and 215, both IKK and Akt kinases induce serine phosphorylation, and Akt mediates CXCR4 expression; (e) ERG-induced CXCR4 drives CXCL12-dependent adhesion to fibronectin; (f) ERG and CXCR4 were co-expressed in human prostate tumor tissues, consistent with ERG-mediated transcriptional activation of CXCR4. These data demonstrates that ERG factor activates CXCR4 expression by binding to the specific ERG/Ets responsive elements and intracellular kinases phosphorylate at ERG at serine residues to induce CXCR4 expression. These findings may provide a mechanistic link between TMPRSS2-ERG translocations and intracellular kinase mediated phosphorylation of ERG on enhanced metastasis of tumor cells via CXCR4 expression and function in prostate cancer cells.