Polycomb group (PcG) proteins are involved in regulation of hematopoiesis, which include two main members Ezh2 and Bmi-1. Reports on their expression levels in different subtypes of malignant lymphoma and role in lymphomagensis and tumor progression are rather limited. To address this issue, we analyzed a total of 197 patient samples including 10 samples of Hodgkin lymphoma (HL), 109 of B-cell lymphoma (BCL) and 78 of T-cell lymphoma (TCL) by immunohistochemistry. The results showed overall expression in HL, BCL and TCL to be 90%, 56.9% and 84.6% for Ezh2 and 90%, 82.5% and 84.6% for Bmi-1 respectively. Among BCL, highest Ezh2 positivity was seen in Burkitt's lymphoma (BL) followed by high-grade follicular lymphoma (FL) and diffuse large B-cell lymphoma (DLBCL). In TCL, Ezh2 expression was observed in all subtypes and seemed more homogenous. Difference in its expression between aggressive and indolent subtypes of BCL was statistically significant (p= 0.000∼0.010). On the other hand, Bmi-1 was rather more consistently expressed in both BCL and TCL up to 100% in 7 subtypes. Difference in its expression between aggressive and indolent subtypes was statistically insignificant. Ki67 showed strong positive correlation with Ezh2 in BCL (Correlation coefficient (Co) =0.983, p= 0.000) and moderate correlation in TCL (Co=0 .629, p= 0.000). This correlation could not be detected in case of Bmi1. These data suggest that out of the two Polycomb group (PcG) proteins, only Ezh2 correlates with tumor proliferation and signals a more aggressive nature.

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 1034. doi:1538-7445.AM2012-1034