Login to Access Video or Poster Abstract: MP87-05
Sources of Funding: NY State, Department of Health, Prostate Cancer Research, RFA # 1410200115

Introduction

Patients who die from prostate cancer (PrCa) do so as a result of the development of castrate resistant disease. Identification of novel targets not related to androgen biosynthesis may provide useful therapeutic alternatives that could have a positive impact on the long term survival of these patients. Recently, it has been shown that upregulation of the opiorphin gene (encoding an endogenous neutral endopeptidase inhibitor involved in the hypoxic response) is an unfavorable risk factor for the survival of oropharyngeal squamous cell carcinoma patients after surgery. In the present studies we determined whether opiorphin is also upregulated in PrCa, and if it plays a role in the hypoxic response in PrCa cells.

Methods

We searched the Gene Expression Omnibus (GEO), a public functional genomics data repository administered by the NCBI, for evidence of opiorphin gene (ProL1) expression. Quantitative-(qt)-RT-PCR was used to compare expression of ProL1 in 41 PrCa tissues and 7 control, non-cancerous prostate tissue present on a commercially available tissue array. Two PrCa cell lines (LnCaP, androgen dependent and PC-3, androgen independent) were exposed to hypoxia for various lengths of time (1-24 hours, RNA isolated and expression of opiorphin and other genes involved in the hypoxic response determined by qt-RT-PCR or microarray analysis.

Results

A search of GEO data demonstrated that the gene encoding opiorphin (ProL1) was significantly upregulated in PrCa. We confirmed a significant upregulation, with a trend for greater upregulation with PrCa stage, on an RNA PrCa tissue array. We found hypoxia resulted in an early (2h) 2-fold upregulation of ProL1 in LnCaP cells. In contrast, in PC3 cells, there was only a significant (3-fold) upregulation of ProL1 after 24h of hypoxia, with other markers of the hypoxic response (Hif1a and VEGF) significantly activated after 5h.

Conclusions

For the first time we report up-regulation of the opiorphin gene (ProL1) in PrCa. Opiorphin is a mediator of the hypoxic response in certain cell types. We demonstrate hypoxic upregulation of ProL1 in two PrCa cell lines. Early upregulation in LnCaP cells, prior to other known markers of the hypoxic response (Hif1a and VEGF) suggests in certain PrCa cells (androgen dependent) ProL1 may play a role in regulating downstream modulators of the hypoxic response. Taken together, these results suggest opiorphin may play a role in overcoming the hypoxic environment in certain PrCa tumors and might therefore represent a novel therapeutic for PrCa.

Funding

NY State, Department of Health, Prostate Cancer Research, RFA # 1410200115