Lc. Boffa et al., Dihydrotestosterone as a selective cellular/nuclear localization vector for anti-gene peptide nucleic acid in prostatic carcinoma cells, CANCER RES, 60(8), 2000, pp. 2258-2262
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.