Antitumor effect of reduction of 150-kDa oxygen-regulated protein expression on human prostate cancer cells

The 150-kDa oxygen-regulated protein ORP150, a new member of the heat shock protein family that functions as a molecular chaperone in the endoplasmic reticulum, was found to increase in infiltrating cancer cells. Since enhancement of ORP150 expression and the presence of vascular endothelial growth factor (VEGF) in human prostate cancer glands were immunohistochemically demonstrated, we examined whether transduced antisense ORP150 cDNA can reduce angiogenicity and tumorigenicity through suppression of VEGF secretion.

Human prostate cancer specimens were immunohistochemically stained with fluorescein isothiocyanate (FITC) for ORP150 or vascular endothelial growth factor (VEGF). An adenovirus vector (Ad) carrying antisense ORP150 cDNA (AdCA-Antisense ORP150) was constructed and infected to prostate cancer DU145 cells. Expression of ORP150 in the cells was analyzed with western blotting and secretion of VEGF into the supernatant with an enzyme-linked immunoabsorbent assay (ELISA). Angiogenicity was evaluated by chorioallantoic membrane (CAM) assay. A nude mouse xenograft model was used to examine tumorigenicity.

Immunohistochemical study proved that the expression of ORP150 and VEGF was enhanced in the cytoplasm of prostate cancer cells. The Ad showed 100% transduction efficiency and minimum cytotoxicity when the cells were infected at a multiplicity of infection (MOI) of 20 for 24 h. Expression of ORP150 was substantially reduced by the antisense treatment. Secretion of VEGF into the culture supernatant was reduced to 30%. Consequently, the CAM assay showed relatively low angiogenicity, while marked suppression of tumor formation was observed in the xenograft model.

Adenoviral-mediated antisense ORP150 cDNA transfer is well worth considering as an option for prostate cancer gene therapy.