Herpes simplex virus thymidine kinase gene transduction enhances tumor growth rate and cyclooxygenase-2 expression in murine colon cancer cells

Abstract

Transduction of tumor cells with herpes simplex virus thymidine kinase (HSV-tk) gene and subsequent treatment with the prodrug ganciclovir (GCV) is the most common system utilized to date for ''suicide'' gene therapy of cancer. In the current report, we show that HSV-tk gene transduction enhances tumor growth rate of murine colon cancer cells, that are implanted subcutaneously in syngeneic mice, and enhances cyclooxygenase-2 (COX-2) protein expression and prostaglandin E 2 (PGE 2 ) release in vitro and in vivo. It is further shown that the observed phenomenon is related to the presence of the HSV-tk sequence insert in the retroviral vector used for HSV-tk gene delivery. Transduction of murine colon cancer cells with control vector, carrying the neomycinresistance gene alone, failed to increase tumor growth rate and COX-2 protein expression or PGE 2 production. On the contrary, it even decreased tumor growth, COX-2 protein expression and PGE 2. The growth rate of HSV-tk-transduced murine tumors was significantly reduced by treatment with the selective COX-2 inhibitor nimesulide. Additionally, we demonstrate herein that both enhanced growth rate of HSV-tk-transduced murine tumors and increased levels of PGE 2 in HSV-tk-transduced cells persist upon the development of GCV resistance. Taken together, these results provide a better understanding of the direct effect of HSV-tk gene transduction on tumor cell biology and target tumor development.

The involvement of nuclear factor-kappa B in cyclooxygenase-2 overexpression in murine colon cancer cells transduced with herpes simplex virus thymidine kinase gene

“…7 We demonstrate herein that HSV-tk gene transduction of murine colon cancer cells results in enhanced activity of NF-kB pathway, which subsequently leads to COX-2 overexpression.…”

“…Western blot analysis was performed as previously described, 7 with slight modifications. Total cell lysates were obtained by scraping cells (1.5 Â 10 7 ) into 200 ml of ice-cold lysis buffer (50 mM Tris-HCl pH 7.5, 1 mM EDTA, 1 mM EGTA, 50 mM sodium fluoride, 0.1% Triton X-100, 1 mM phenylmethylsulfonyl fluoride, 1 mM leupeptin, 20 m/ml aprotinin and 1 mM sodium vanadate).…”

“…STK and LNL6 retroviral vectors have been described. 1,7 To construct an STK vector, HSV-tk sequence was inserted into LNL6 vector, harboring the neomycin resistance (Neo R ) gene, which encodes for neomycin phosphotransferase II and confers resistance to the neomycin analog G418. MC38 cells transduced with HSV-tk (MC38/HSV-tk) or Neo R gene (MC38/Neo R ) as well as HSV-tk-transduced COS-7 cells (COS-7/HSV-tk) were generated by stable transduction of wild-type cells as previously described.…”

“…5,6 Additionally, we have previously reported that HSV-tk gene transduction of murine colon cancer (MC38) cells results in a significant enhancement of tumor growth rate in syngeneic mice as well as increased cyclooxygenase-2 (COX-2) expression and activity in vitro and in vivo. 7 We proposed that the latter might occur via activation of the nuclear factor-kappa B (NF-kB) pathway, which often plays an essential role in the upregulation of COX-2 expression during carcinogenesis. Thus, our current study aimed to investigate the effect of HSVtk gene transduction on NF-kB activity and the involvement of NF-kB in COX-2 overexpression previously observed in HSV-tk-transduced MC38 cells.…”

“…Thus, our current study aimed to investigate the effect of HSVtk gene transduction on NF-kB activity and the involvement of NF-kB in COX-2 overexpression previously observed in HSV-tk-transduced MC38 cells. 7 NF-kB comprises a family of the most ubiquitous eucaryotic transcription factors that serve as important regulators of the host inflammatory and immune response. NF-kB complex is a heterodimer, consisting of subunits of Rel family (Rel A or p65, p50, p52, c-Rel, v-Rel and Rel B), which is retained in the cytoplasm of unstimulated cells by binding to inhibitory proteins, known as IkB (IkBa, IkBb, IkBe, p105 and p100).…”