Increased prostate-specific membrane antigen expression in LNCaP cells following treatment with bispecific antisense oligonucleotides directed against bcl-2 and EGFR

Antisense oligonucleotides have been employed against in vivo and in vitro prostate cancer models. While most oligos consist of a single mRNA binding site, targeting a single gene product or others sharing sequence homology, our laboratory has developed bispecific oligos directed toward even unrelated proteins. This study evaluates the inhibition of in vitro propagating LNCaP cells employing mono- and bispecific oligos directed against bcl-2 [the second bispecific binding site was directed against the epidermal growth factor receptor (EGFR)]. Employing RT-PCR, the expression of non-targeted proteins encoded by mRNA for prostate-specific membrane antigen (PSMA) and prostate-specific antigen (PSA) were subsequently evaluated. When LNCaP prostate tumor cells were incubated with bispecific oligos (directed against bcl-2 and EGFR) and compared to lipofectin-containing controls significant growth inhibition resulted. In subsequent experiments, the levels of mRNA encoding PSMA were unexpectedly found to be elevated following treatment with the bispecific oligos but not with the monospecific directed solely against bcl-2. No differences were detected in mRNA levels encoding PSA following treatment with either mono- or bispecific oligos. Previously, we suggested that cell growth inhibition produced by some bispecifics could be attributed to complementary double-stranded regions formed by intra-strand base pairs. Double-stranded nucleic acids are known inducers of interferon, which promote expression of cell surface HLA type antigens. If induced, perhaps this cytokine also enhances PSMA expression, making prostate tumor cells a more recognizable target for cytotoxic T cells.