Abstract 2717: Detection of Merkel cell polyomavirus in chronic lymphocytic leukemia cells by fluorescence in situ hybridization (FISH)

Abstract

Background: Merkel cell polyomavirus (MCPyV) is detected in approximately 80% of Merkel cell carcinomas (MCC). A number of previous studies have shown that MCC patients are at a significantly increased risk to develop chronic lymphocytic leukemia (CLL) and vice versa. Until recently, clonal integration and truncating mutations of the Large T antigen (LTAg) of MCPyV were restricted to MCC. We have recently reported the presence of the MCPyV in highly purified tumor cells of CLL (n = 19/70, 27.1%) (Blood. 2010 Sep 3). Of these, six revealed a novel 246 bp deletion in the helicase gene of the LTAg. The presence of MCPyV was confirmed by immunohistochemistry. Material and Method: Here we aimed to determine the presence of MCPyV by fluorescence in situ hybridization (FISH) analysis in CLL cells in order to evaluate whether MCPyV was integrated or episomal. For this purpose we performed FISH analysis as previously described (Int J Cancer. 2005, 115:419-428) using the MCPyV genome as FISH probe. We tested 2 of the previously reported MCPyV positive CLL cases (EDTA decalcified bone marrow trephines) and MCPyV-positive MCC (n = 5). In addition, we tested MCPyV-negative tumors, e.g. breast and colon cancers. All tissues were formalin-fixed and paraffin-embedded. Results: Specific MCPyV DNA by FISH analysis was detected in the nuclei of MCPyV-positive CLL and MCC cells. In contrast to particularly punctate FISH signals in MCC indicating viral integration, the nuclear FISH signals of the CLL cases revealed especially granular signals, indicative for integrated MCPyV DNA together with transcribed viral RNA (Int J Cancer. 2008, 122:2656-2664). No signals were obtained by MCPyV FISH in breast or colon cancer specimens. Conclusion: The specific detection of MCPyV in CLL cells further supports our previous report of a possible involvement of MCPyV in a significant subset of CLL. The specific but rather granular nuclear FISH signals in MCPyV positive CLL cells needs further study to evaluate if it is also generated by co-existing episomal virus copies, by viral RNA or by the decalcification process. In addition, more CLL cases will be analyzed for the presence of MCPyV. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2717. doi:10.1158/1538-7445.AM2011-2717