Gene therapy for prostate cancer by targeting DNA-damage response.

I Trofimova, PhD, A Dimtchev, PhD, M Jung, PhD, D Rosenthal PhD, M Smulson, PhD, A Dritschilo MD, V Soldatenkov MD, PhD

Georgetown University Medical School, Washington, DC United States

AIM: The central aim of this study is to express the DNA-binding domain (DBD) of poly(ADP-ribose) polymerase (PARP) under control of the prostate-specific antigen (PSA) promoter in prostate carcinoma cells in order to achieve their sensitization to genotoxic treatments. METHODS: We have developed a recombinant plasmid comprised of the coding region of the PARP-DBD linked to 5'-flanking sequences (1.3 kb upstream enhancer/ 0.6 kb minimal promoter) of the human PSA gene. RESULTS: Tissue specificity and PSA-dependence of PARP-DBD expression in human tumor cells were confirmed using the PSA-positive (LNCaP) and PSA-negative (PC-3) prostate cancer cells and cells of non-prostate origin, Ewing's sarcoma (A4573 cells). LNCaP cells stably transfected with PSA regulated PARP-DBD cDNA demonstrated androgen-dependent induction of PARP-DBD expression on Western blotting, RT-PCR and in situ immunofluorescence. Further, we found that PARP-DBD sensitized LNCaP cells to treatments with DNA-damaging agents, including ionizing radiation and etoposide. Forced PARP-DBD expression resulted in growth inhibition in LNCaP cells and activation of caspase-independent cell death in response to ionizing radiation (10-20 Gy) or etoposide (2,5-10 µM). CONCLUSIONS: Androgen-inducible and PSA-dependent expression of the human PARP-DBD sensitizes prostatic adenocarcinoma cells to DNA-damaging treatments, presenting a novel strategy for gene therapy.

KEY WORDS: Poly (ADP-ribose) polymerase.

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Paper presented at the International Symposium on Predictive Oncology and Intervention Strategies; Paris, France; February 9 - 12, 2002; in the section on Gene Therapy, Part 2.