Addition of a single E2 binding site to the human papillomavirus (HPV) type 16 long control region enhances killing of HPV positive cells via HPV E2 protein-regulated herpes simplex virus type 1 thymidine kinase-mediated suicide gene therapy

Human papillomavirus type 16 (HPV16) is associated with the development of anogenital cancers and their precursor lesions, intraepithelial neoplasia. Treatment strategies against HPV-induced intraepithelial neoplasia are not HPV specific and mostly consist of physical removal or ablation of lesions. We had previously designed an HPV-specific approach to kill HPV-infected cells by the herpes simplex virus type 1 thymidine kinase (TK) gene driven by HPV E2 binding to E2-binding sites (E2BS) in the native HPV16 long control region. E2-induced TK expression renders the cells sensitive to the prodrug ganciclovir. To optimize this therapeutic approach, we modified the native long control region by adding variable numbers of E2BS adjacent to E2BS4, resulting in greatly increased cell death in HPV-positive cell lines with variable levels of E2 protein expression and no reduction in HPV specificity. Our results showed maximum increase in TK expression and cell killing when one additional E2BS was added adjacent to E2BS. As HPV-infected patients also exhibit variable E2 expression across lesions and within a lesion, this approach may potentiate the clinical utility of the herpes simplex virus type 1 TK/ganciclovir therapeutic approach.

Human papillomavirus E2 protein associates with nuclear receptors to stimulate nuclear receptor- and E2-dependent transcriptional activations in human cervical carcinoma cells

Steroid hormones are proposed to act with human papillomaviruses (HPVs) as cofactors in the etiology of cervical cancer. Steroid hormone-activated nuclear receptors (NRs) are thought to bind to specific DNA sequences within transcriptional regulatory regions on the HPV DNA to either increase or suppress transcription of dependent genes. HPV-induced immortalization of epithelial cells usually requires integration of the viral DNA into the host cell genome. The integration event causes disruption of the E2 gene: the E2 protein is a transcription factor that regulates expression of the E6 and E7 oncoproteins by binding to four sites within the viral long control region (LCR). Our previous study suggested that E6 and E7 oncoproteins both directly bind to some NRs and serve as their cofactors. Here, we provide several lines of evidence demonstrating that the E2 protein is an NR coactivator through its physical interaction with NRs. In our study, the NR coactivator function of HPV E2 protein in human cervical carcinoma cells was independent of the type of E2, HPV transformation and the p53 status. Our observations also provide evidence suggesting regulatory mechanisms for the LCR involving interaction between the E2 protein and NRs in HeLa cells.

Treatment of human papillomavirus (HPV) type 16-infected cells using herpes simplex virus type 1 thymidine kinase-mediated gene therapy transcriptionally regulated by the HPV E2 protein

Human papillomavirus type 16 (HPV-16) is associated with development of anogenital squamous cell cancers (SCCs) and their precursor, intraepithelial neoplasia (IN). Few approaches to the treatment of IN to prevent SCC are targeted specifically to HPV. We have designed an HPV-specific therapy using the herpes simplex virus type 1 thymidine kinase (HSV-1 TK) gene driven by an HPV-specific promoter in the HPV-16 long control region (LCR) (nucleotide 7450-nucleotide 104), which is regulated by the HPV E2 protein. Expression of the HSV-1 TK gene is designed to render HPV-infected cells sensitive to the prodrugs ganciclovir (GCV) and acyclovir (ACV). To assess the E2 specificity of gene expression driven by the HPV-16 LCR, we measured luciferase expression in HPV-positive and HPV-negative cell lines. Significant induction of luciferase activity was observed in HPV-positive cells when compared with four different HPV-negative epithelial cell lines. Cotransfection of an HPV-negative cell line, MDCK, with an HPV-16 E2-expressing plasmid resulted in 15- to 20-fold induction of luciferase activity, suggesting specific activation by E2 protein. A plasmid expressing the HSV-1 TK gene driven by the LCR was transfected into CaSki and SiHa cells. Treatment of transfected cells with either GCV or ACV (20-30 microg/ml) for 6-10 days resulted in 80-95% cell death. Cell death was progressive, dose dependent, and mediated by apoptosis. These results suggest that direct gene transfer of the HSV-1 TK gene into HPV-16-infected cells expressing E2 protein, accompanied by treatment with either GCV or ACV, may be a clinically feasible therapeutic strategy.

Interleukin-10 induces transcription of the early promoter of human papillomavirus type 16 (HPV16) through the 5'-segment of the upstream regulatory region (URR)

The effects of various proinflammatory cytokines on the transcription of human papillomaviruses (HPVs) have been demonstrated. On the other hand, the role of anti-inflammatory cytokines has not been elaborated, despite the fact that levels of interleukin-10 (IL-10) have been found significantly elevated in cervical dysplasias or carcinomas as well as in the cervix of HIV-positive individuals. These conditions are also associated with elevated viral transcription. Thus, the impact of IL-10 on HPV transcription might be important in pathogenesis of cervical lesions in both immunocompetent or immunosuppressed individuals. In this paper we describe the effects of IL-10 on the transcription of HPV type 16. We found that treatment of HPV 16-positive cervical carcinoma cells with IL-10 increased mRNA levels of the E7 early gene at the level of transcription. Similarly, IL-10 significantly and dose-dependently induced the transcription from the HPV early promoter in a reporter system. Employing deletion mutants we determined that this induction is mapped to the 5' segment of the URR. Transient transfection of an antisense-STAT3-expression vector abolished IL-10-induced reporter activity as well as HPV 16 E7 expression. This suggests that STAT3 either directly binds to the URR and stimulates transcription or affects expression and/or binding of transcription factors that bind to the 5'-region. Our findings suggest a mechanism by which--in addition to its immunosuppressive effects--IL-10 might enhance persistence and progression of HPV-related lesions under conditions (e.g. dysplastic progression, HIV infection) when the cytokine expression in the cervical microenvironment changes.

Differences in responses of interleukin-1 and tumor necrosis factor alpha production and secretion to cyclosporin-A and ultraviolet B-irradiation by normal and transformed keratinocyte cultures

Among epidermal cytokines, IL-1 and TNF alpha are involved in inflammatory skin reactions and suspected of modulation by immunosuppressive treatment (e.g., cyclosporin A, CsA) or UVB-irradiation, 2 mediators probably being involved in epithelial carcinogenesis. We evaluated the effects of 8 micrograms/ml CsA and 100 J/m2 UVB-irradiation on the production and secretion of IL-1 and TNF alpha on normal human epidermal keratinocytes (NHK) and epidermal keratinocyte cell lines either spontaneously transformed (HaCaT) or transformed by human papillomavirus (HPV) type 16 or 18 (EK 16 and EK18), by using ELISA test. Normal and immortalized keratinocytes constitutively produced and released IL-1 alpha, IL-1 beta and IL-1 receptor antagonist (IL-1RA) but IL-1 synthesis by NHK was significantly higher than by cell lines. All the cells spontaneously excreted low amounts of TNF alpha. Different responses to treatments were evidenced between NHK and cell lines. CsA modified significantly the production and secretion of IL1 in most cells whereas slight changes were observed with TNF alpha secretion. UVB irradiation had no effect on the intracellular IL1 pool of any cells but increased the release of IL1 and TNF alpha. The association CsA-UVB did not result in additive effects on synthesis and secretion of IL1; the release of TNF alpha by the cells remained poor except for EK18 cells. Taken together, these results show that, in immortalized keratinocytes, the IL-1 and TNF alpha expression was differently affected by treatments with CsA and/or UVB-irradiation as compared to NHK. In addition, spontaneously transformed keratinocytes, HaCaT, reacted differently from HPV-transformed keratinocytes, EK16 and EK18.

Response to interferon treatment decreases with epidermal dedifferentiation in condylomas

After interferon (IFN) treatment of patients with condyloma acuminatum, groups clinically proven to be responders or nonresponders were selected, and cellular parameters that might influence the clinical response were studied in pretreatment biopsies by reverse transcription polymerase chain reaction (RT-PCR). The nonresponders were found to express higher amounts of cellular proliferative markers, such as proliferating cell nuclear antigen (PCNA), cyclin A, and cdc 2 kinase, but lower levels of growth suppressor genes (TGF-beta 1, TGF-beta 2 and p53) before IFN treatment. The responders retained the epidermal keratinization, except for some signs of hyperproliferation (K6, K16 cytokeratins). In addition, the nonresponders showed a shift in the keratinization pattern to a mucosal or fetal type, as evidenced by high expression of the K18, K6, K16 and K13 cytokeratins but decreased K5, K14 and K10 levels before treatment. The expression of the human papillomavirus (HPV) genes is consistent with these differentiation patterns. The crucial conclusion to be drawn from this study is that those condylomas whose pretreatment phenotype most closely resembles that of normal epidermis respond to IFN treatment, whereas those more akin to nonkeratinizing epithelia fail to respond, i.e. the resistance of condylomas to IFN treatment is correlated with dedifferentiation.