Dihydrotestosterone as a selective cellular/nuclear localization vector for anti-gene peptide nucleic acid in prostatic carcinoma cells

Peptide nucleic acids (PNAs) are synthetic structural analogues of DNA and RNA that, if allowed to enter the cell, bind to the complementary polynucle otide sequence and inhibit DNA transcription and mRNA translation, Although PNAs have a very limited ability in penetrating nuclei of living cells, th ere are indications that covalent linkage of the PNA to appropriate vectors , e.g., a nuclear localization signal, permits access to the genome. Here w e test the ability of dihydrotestosterone (T) covalently linked to PNA to a ct as a vector for targeting c-myc DNA to prostatic cancer cell nuclei. LNC aP cells, which express the androgen receptor gene, and DU145 cells, in whi ch me androgen receptor gene is silent, offer a model to test this biologic ally active hormone as a cell-specific vector, T vector was covalently link ed to the NH2-terminal position of a PNA complementary to a unique sequence of c-myc oncogene (PNAmyc-T), To localize PNAmyc-T and vector-free PNA wit hin the cells, a rhodamine (R) group was attached at the COOH-terminal posi tion (PNAmyc-R, PNAmyc-TR); cellular uptake was monitored by confocal fluor escence microscopy, PNAmyc-R was detected only in the cytoplasm of both pro static cell lines, whereas PNAmyc-TR was localized in nuclei as well as in cytoplasm of LNCaP cells. In contrast, PNAmyc-TR uptake in DU145 cells was minimal and exclusively cytoplasmic, In LNCaP cells, MYC protein remained u nchanged by exposure to vector-free PNAmyc, whereas a significant and persi stent decrease was induced by PNAmyc-T, In DU145 cells, MYC expression was unaltered by PNAmyc with or without the T vector. Our data show that the T vector facilitates cell-selective nuclear localization of PNA and its conse quent inhibition of c-myc expression. These findings suggest a strategy for targeting of cell-specific anti-gene therapy in prostatic carcinoma.