Dihydrotestosterone as a selective cellular/nuclear localization vector for anti-gene peptide nucleic acid in prostatic carcinoma cells
Boffa,Lidia C.; Scarfi,Sonia; Mariani,Maria Rita; Damonte,Gianluca; Allfrey,Vincent G.; Benatti,Umberto; Morris,Patricia L.
Cancer Research 60(8): 2258-2262
Publication date: 2000
Peptide nucleic acids (PNAs) are synthetic structural analoguesof DNA and RNA that, if allowed to enter the cell, bind to the complementarypolynucleotide sequence and inhibit DNA transcription and mRNAtranslation. Although PNAs have a very limited ability in penetratingnuclei of living cells, there are indications that covalent linkageof the PNA to appropriate vectors, e.g., a nuclear localizationsignal, permits access to the genome. Here we test the abilityof dihydrotestosterone (T) covalently linked to PNA to act asa vector for targeting c-myc DNA to prostatic cancer cell nuclei.LNCaP cells, which express the androgen receptor gene, and DU145cells, in which the androgen receptor gene is silent, offera model to test this biologically active hormone as a cell-specific vector.T vector was covalently linked to the NH-terminal positionof a PNA complementary to a unique sequence of c-myc oncogene(PNAmyc-T). To localize PNAmyc-T and vector-free PNA withinthe cells, a rhodamine (R) group was attached at the COOH-terminalposition (PNAmyc-R, PNAmyc-TR); cellular uptake was monitoredby confocal fluorescence microscopy. PNAmyc-R was detected onlyin the cytoplasm of both prostatic cell lines, whereas PNAmyc-TRwas localized in nuclei as well as in cytoplasm of LNCaP cells.In contrast, PNAmyc-TR uptake in DU145 cells was minimal and exclusivelycytoplasmic. In LNCaP cells, MYC protein remained unchanged byexposure to vector-free PNAmyc, whereas a significant and persistent decreasewas induced by PNAmyc-T. In DU145 cells, MYC expression was unalteredby PNAmyc with or without the T vector. Our data show that theT vector facilitates cell-selective nuclear localization ofPNA and its consequent inhibition of c-myc expression. These findingssuggest a strategy for targeting of cell-specific anti-gene therapyin prostatic carcinoma.