The Presence of Merkel Cell Polyomavirus (MCPyV) in Chronic Lymphocytic Leukemia/Small Lymphocytic Lymphoma.
Carolin Teman, Sheryl Tripp, Sherrie Perkins, Eric J Duncavage. University of Utah, Salt Lake City; ARUP Laboratories, Salt Lake City, UT
Background: Merkel Cell Polyomavirus (MCPyV) is a novel polyomavirus with a high seroprevalence in the normal adult popuation, that shows a strong association with Merkel cell carcinoma (MCC). Although recent studies have demonstrated the presence of MCPyV in a subset of chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL), a malignancy that shares a similar demographic to MCC, this finding is controversial. We sought to characterize MCPyV in cases of CLL/SLL by both PCR and immunohistochemistry.
Design: 18 consecutive cases of formalin-fixed nodal CLL/SLL, with adequate tissue available, were selectively sampled by 1mm punches and DNA extracted. Standard PCR was performed using 2 previously published MCPyV primer sets (MCVPS1 and N-terminal) with 100ng of genomic DNA. A similarly-sized beta globin product (110bp) was used as an amplification control, and previously tested cases of MCC were used as positive controls. PCR products were detected by 2% agarose gel electrophoresis. To quantitate MCPyV levels, we also performed TaqMan PCR in triplicate with 500ng of genomic DNA and primers targeting the conserved small T antigen. Furthermore, we evaluated the expression of MCPyV at the protein level by performing immunohistochemistry (IHC) with CM2B4 MCPyV LT antibody followed by automated image analysis.
Results: Standard PCR testing demonstrated no evidence of MCPyV in CLL/SLL cases with either the MCVPS1 or N-terminal primer sets (0/18). The higher sensitivity TaqMan PCR detected low viral levels (∼50,000x lower than the MCC reference control) in 6/18 cases (33%). MCPyV immunohistochemistry showed that only 1 of 18 cases had appreciable (≥2+) staining in ≥5% of lymphocytes, by automated image analysis. The single IHC positive case also demonstrated low MCPyV viral copy numbers by TaqMan PCR.
Conclusions: We detected low-level MCPyV in 33% CLL/SLL cases and could confirm weak viral protein expression by IHC in a single case (1/18). Several European groups have recently reported MCPyV in up to 27% of CLL/SLL as well as 'tumor specific' truncating mutations, findings that may reflect differences in the geographic distribution of MCPyV. However, given the low level of MCPyV in CLL/SLL compared to MCC and the high seroprevalence of MCPyV in the general population, our findings likely represent low-level viral re-activation in CLL/SLL rather than MCPyV-driven oncogenesis.
Wednesday, March 2, 2011 9:30 AM
Poster Session V # 166, Wednesday Morning