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.

In the K14-HPV16 transgenic mouse model of human papillomavirus (HPV)-associated squamous cell cancers, HPV16 E6 and E7 oncogenes and E1 and E2 regulatory genes are driven by the K14 keratinocyte-specific promoter. HPV transcription varies within the different layers of the epithelium. The correlation between HPV transcription patterns and disease pathogenesis is not well understood. Understanding these patterns is critical to designing and testing new HPV-specific therapeutic strategies. We examined HPV gene expression in homogenous populations of cells microdissected from the stratum basale, stratum spinosum, and stratum corneum of lesions from the transgenic mice using PALM microlaser technology. RNA extracted from each cell layer was subjected to two-step gene-specific RT-PCR and real-time quantitative nested PCR. To ensure specific amplification of spliced transcripts, the primers used for real-time nested PCR spanned the splice sites. High levels of E2 were detected in the basal and supra-basal layers of hyperplastic and dysplastic lesions. E7 and E6* levels increased significantly over time in stratum basale and stratum spinosum. E6** was expressed at much lower levels. We showed that the transgenic mice express correctly spliced E2 transcripts and are suitable as a preclinical model to test a therapeutic strategy using transcriptional regulation by the E2 protein.

Introduction:Oral squamous cell carcinoma (OSCC) comprises one of the largest subsets of cancers with a tendency for regional metastasis. Nodal status is a key prognostic indicator in patients with OSCC, particularly with N0 neck. Occult metastasis in the form of micrometastasis (MM) and isolated tumor cells (ITCs), often goes undetected by routine hematoxylin and eosin (H&E) examination using 1–2 sections for analysis. This limitation could be overcome by combining serial sectioning (SS) with immunohistochemistry (IHC) for the detection of MM and ITC. Pan-cytokeratin (pan-CK) (AE1/AE3) is particularly a useful marker to detect these deposits as their presence has resulted in varied interpretations and different applications of the tumor-node-metastasis system.Objectives:The objective of the study was to identify a suitable method for detecting MM and ITC in lymph nodes (LNs) of OSCC by combining SS and IHC and to compare it with conventional H&E staining.Materials and Methods:This laboratory-based, prospective study was conducted on 133 LNs harnessed from ten patients treated with radical neck dissection for primary OSCC. The LNs were subjected to SS at 100 μm intervals. The sections were stained with routine H&E staining, pan-CK and analyzed for MM and ITC according to criteria laid by Hermanek et al.Statistical Analysis:The obtained data were subjected to statistical analysis using Chi-square test.Results:The application of combination of SS and IHC using pan-CK (AE1/AE3) in our study revealed the presence of MM and ITC in 2.25% of the LNs diagnosed as negative on routine H&E examination. The detection of these occult metastatic deposits resulted in upstaging of 33.33% of the patients.Conclusion:In the view of crucial role of occult LN metastasis in prognosis and survival of OSCC patients with N0 neck, diagnostic tools such as IHC staining, particularly with pan-CK (AE1/AE3), combined with SS should be preferred over conventional methods as they result in upstaging, thus sparing the low-risk patients the morbidity of unnecessary treatment.

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