Merkel Cell Polyomavirus Gene Expression and Mutational Analysis of Large Tumor Antigen in Non-Merkel Cell Carcinoma Tumors of Iranian Patients

Abstract

<b><i>Introduction:</i></b> The presence of Merkel cell polyomavirus (MCPyV) was identified in Merkel cell carcinoma (MCC). However, there was sparse information on the link of other common nonmelanoma skin cancers – basal cell carcinoma (BCC) and squamous cell carcinoma (SCC) – to MCPyV infection. The current study describes the phylogenetic information of MCPyV isolated from Iranian non-MCC (nonmelanoma skin cancers) focusing on tumorigenesis of mutations in large tumor (LT) antigen (LT-Ag) fragment. <b><i>Methods:</i></b> Sixty patients with BCC and 20 patients with SCC were included in this study (48 males and 32 females; average age 65 years). The MCPyV-DNA copy number in positive samples was measured by quantitative real-time PCR. Then, mutational analysis of the MCPyV LT gene was carried out by direct sequencing. <b><i>Results:</i></b> While MCPyV DNA was detected in 6 (10%) of 60 BCC samples, no viral genome was found in SCCs. There was no distinct association of MCPyV positivity with gender, age, or type of tumor (BCC or SCC) (<i>p</i> value &#x3e;0.05). Quantitative real-time PCR revealed that the median number of viral DNA copies per cell was 0.7 in 6 MCPyV-positive BCC samples. Furthermore, full-length LT-Ag sequencing of positive samples indicated no stop codon or frameshift mutations compared to reference sequences. <b><i>Conclusion:</i></b> Considering the important role of the LT-Ag in the pathogenicity of MCPyV, non-synonymous mutations compared with the reference proteins triggered relevant amino acid substitutions. Overall, the results showed no tumor-associated mutations in the LT-Ag sequence of MCPyVs from positive samples.