Cooperative therapeutic effects of herpes simplex virus thymidine kinase gene/ganciclovir system and chemotherapeutic agents on prostate cancer in vitro

Abstract

The killing effects of herpes simplex virus thymidine kinase gene/ganciclovir (HSV-tk/GCV) approach by the addition of several commonly clinical chemotherapeutic agents on hormone refractory prostate cancer (HRPC) cells PC-3m were investigated. After transferring of the HSV-tk gene into PC-3m cells, mRNA and protein expression of HSV-tk was detected by reverse-transcript polymerase chain reaction (RT-PCR) and strept avidin-biotin complex (SABC) immunohistochemical method. The killing effect of GCV, cisplatin (CDDP), etoposide (VP-16), vincristine (VCR), methotrexate (MTX), 5-fluorouracil (5-Fu), and suramin on PC-3m cells was evaluated by morphological assessment analysis, trypan blue exclusion assay and MTT assay respectively. Additionally, the cooperative effect of HSV-tk/GCV system combined with the above agents on the target cancer cells was determined by MTT. Furthermore, apoptosis and necrosis induced by GCV plus 5-Fu or suramin was analyzed by flow cytometry (FCM). The results showed that that there was HSV-tk mRNA and protein expression in pDR2-tk plasmid transduced PC-3m cell. Combination of GCV with VP-16, VCR, 5-Fu or suramin led to an enhanced cellular killing effect, but with CDDP resulted in a reduced one and with MTX in an approximate one. FCM revealed that synergistic use of GCV and 5-fu or suramin resulted in a rather large proportion of apoptosis and necrosis with the apoptosis index being 36.38 % and 35.51 %, and the proportion of necrosis being 33.05 % and 28.87 %, respectively. In conclusion, HSV-tk/CGV approach by addition of certain clinical available chemotherapeutic drugs brings on statistically significant enhanced cell killing over single-agent treatment. Our results highlight the potential for such new combination therapies for future treatments of HRPC.

Keywords

prostatic neoplasms / herpes simplex virus thymidine kinase gene / ganciclovir / chemotherapy / gene therapy

References

[1] ShalevM., KadmonD., TehB. S., et al.. Suicide gene therapy toxicity after multiple and repeat injections I patients with localized prostate cancer. J Urol, 2000, 163: 1747-1750

[2] CheonJ., KimH. K., MoonD. G., et al.. Adenovirus-mediated suicide-gene therapy using the herpes simplex virus thymidine kinase gene in cell and animal models of human prostate cancer: changes in tumor cell proliferative activity. BJU Int, 2000, 85: 759-766

[3] AtkinsonG., HallS. J.. Prodrug activation gene therapy and external beam irradiation in the treatment of prostate cancer. Urology, 1999, 54: 1098-1104

[4] HermanJ. R., AdlerH. L., Aguilar-CordovaE., et al.. In situ gene therapy for adenocarcinoma of the prostate: a phase I clinical trial. Hum Gene Ther, 1999, 10: 1239-1249

[5] StermanD. H., TreatJ., LitzkyL. A., et al.. Adenovirus-mediated herpes simplex virus thymidine kinase/ganciclovior gene therapy in patients with localized malignance: results of a phase I clinical trial in malignant mesothelioma. Hum Gene Ther, 1998, 9: 1083-1092

[6] WildnerO., BlaeseR. M., CandottiF.. Enzyme prodrug gene therapy: synergistic use of the herpes simplex virus-cellular thymidine kinase/ganciclovir system and thymidylate synthase inhibitors for the treatment of colon cancer. Cancer Res, 1999, 59: 5233-5238

[7] BoucherP. D., OstruszkaL. J., ShewachD. S.. Synergistic enhancement of herpes simplex virus thymidine kinase/ganciclovir-mediated cytoxicity by hydroxyurea. Cancer Res, 2000, 60: 1631-1636

[8] McMastersR. A., WilbertT. N., JonesK. E., et al.. Two-drug combinations that increase apoptosis and modulate bak and bcl-X(L) expression in human colon tumor cell lines transduced with herpes simplex virus thymidine kinase. Cancer Gene Ther, 2000, 7: 563-573

[9] WildnerO., BlaeseR. M., MorrisJ. C.. Synergy between the herpes simplex virus tk/ganciclovir prodrug suicide system and the topoisomerase I inhibitor topotecan. Hum Gene Ther, 1999, 10: 2679-2687