Abstract 557: Fluorescence in situ hybridization versus qPCR as means to detect Merkel cell polyomavirus in Merkel cell carcinoma

Abstract

Abstract Background: Merkel cell polyoma virus (MCPyV) is detected in 80% of Merkel cell carcinomas (MCC). The clonal integration and tumor specific mutations in the large T Antigen (LTAg) gene strongly implicate an oncogenic impact of the virus. To date the relationship between the viral presence and cancer induction, development or clinical prognosis is discussed controversial. Yet almost all studies are based on quantitative virus detection e.g. PCR or qPCR. Material and Method: In order to gain additional information about the quality of the viral presence on the single cell level we performed FISH analysis of formalin fixed and paraffin embedded (FFPE) MCCs (n= 62) on tissue micro arrays (TMA), determined the FISH pattern and correlated the results of the FISH analysis with the qPCR data. We grouped the MCCs according to different FISH evaluations and correlated them with the respective qPCR data on the basis of a determined cut-off. MCPyV FISH was established using the MKL-1 cell line which harbors integrated copies of MCPyV DNA. For MCPyV-qPCR the LT3 primer pair was used on whole tissue sections. Results: MCPyV-FISH on FFPE MKL-1 cells revealed punctate signals compatible with viral integration. The MCPyV FISH positive MCC cores (76%) mainly revealed two different signal patterns: a punctate pattern (85%) which correlated with a moderate relative viral presence and in some areas the punctate pattern was combined with a diffuse pattern (15%) indicating the episomal presence of the virus which is linked to viral replication. If a pattern mixture was seen this was associated with very high qPCR values. Comparing MCPyV FISH and qPCR data the results correlated highly with 83 % in the MCPyV positive evaluated group, whereas the negative group showed a concordance of 93 %. The mean of the qPCR values of all MCPyV positive cores differed significantly from the negative cores (p= 0.0076). The FISH signals were in some tumor areas from the same patient heterogenic in intensity, pattern and localization. Conclusion: While the qPCR using the LT3 primer pair was highly sensitive to detect MCPyV sequences in the respective MCC cases, the MCPyV FISH analysis highly concordantly revealed the quality of the viral presence, i.e. viral integration or episomal presence and morphological sublocalization in the tissues. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 557. doi:1538-7445.AM2012-557