Abstract 108: Inhibition of demethylase, JMJD3 sensitizes diffuse large B-cell lymphoma (DLBCL) to chemotherapy

Abstract

Abstract Introduction Diffuse large B-cell lymphoma (DLBCL) is the most common form of non-Hodgkin's lymphoma (NHL) representing more than 30% of new cases diagnosed in the United States. DLBCL comprises multiple biologically and clinically distinct subtypes including germinal center B-cell-like (GCB) and activated B-cell like (ABC) DLBCL. Despite improvement in current therapies, nearly 40% of patients die from the disease. Recent studies of the epigenome and the methylome in particular, have revealed widespread epigenetic changes in DLBCL. Aberrant methylation of core histone tails occur with deregulation of methylase enzymes such as Ezh2 in DLBCL. In contrast, the role of JMJD3 and UTX, H3K27(me)3 demethylases in DLBCL remains unknown. In this study, we have evaluated the activity of the selective JMJD3 inhibitor GSK-J4 in DLBCL and investigated the mechanism of its action. Methods Panel of DLBCL cell lines: DB, KARPAS 422, Pfeiffer, Toledo, Sudhl2, Sudhl6, Sudhl8, TMD8, OCI-Ly1, OCI-Ly3, OCI-Ly7, OCI-Ly8, OCI-Ly4, OCI-Ly10, and primary DLBCL cells were analyzed for the expression of lysine demethylases (KDMs) using RT-PCR and Western blot analysis. Sub-G1 analysis was performed to analyze drug-induced apoptosis. Chemical inhibitor GSK-J4 and siRNAs were used for specific inhibition of the JMJD3. Results JMJD3 inhibitor, GSK-J4 induced the killing of DLBCL cell lines of both GC and ABC subtypes. Cell sensitivity to GSK-J4 could not be predicted from the expression of prognostic markers in DLBCL such as Bcl6, IRF4 and Ezh2. For further studies, we selected a cell line Sudhl6 (Bcl6 dependent), sensitive to the killing effect of GSK-J4. Treatment with GSK-J4 reduced the Bcl6 levels along with concomitant increase in IRF4 and FBXO11, negative regulators of Bcl6. Knockdown of JMJD3 by siRNAs also reduced the levels of Bcl6, implicating Bcl6 in the mechanism of action of GSK-J4. Additionally, GSK-J4 synergized in killing with vincristine, doxorubicin as well as proteasome inhibitors bortezomib and carfilzomib. Conclusion We demonstrate the potent effects of inhibition of H3K27(me)3 demethylase JMJD3 by GSK-J4 on proliferation and apoptosis of DLBCL cells. Our results clearly show synergistic effects of inhibition of demethylase with standard drugs in elimination of DLBCL cells. Note: This abstract was not presented at the meeting. Citation Format: Rohit Mathur, Lalit Sehgal, Zuzana Berkova, Sattva S. Neelapu, Felipe Samaniego. Inhibition of demethylase, JMJD3 sensitizes diffuse large B-cell lymphoma (DLBCL) to chemotherapy. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 108. doi:10.1158/1538-7445.AM2015-108