Targeting Cholesterol Biosynthesis Sensitizes Diffuse Large B Cell Lymphoma Non-Responsive to EZH2 Inhibition
The histone methyltransferase EZH2 is an oncogenic driver in Germinal Center B cell-like Diffuse Large B Cell Lymphoma (GCB-DLBCL). Inhibition of EZH2 in GCB-DLBCLs identified sensitive and insensitive subsets, yet clinical trials showed only modest efficacy. In the past years, the attention has moved to the drug combination approach to improve the efficacy of the monotherapy. Here, we aimed to discover genetic and pharmacologic vulnerabilities to enhance the clinical efficacy of EZH2 inhibitors in patients with GCB-DLBCL.
To find a novel target that synergizes with EZH2 inhibition, we performed a drug-anchored CRISPR-Cas9 screen. The cholesterol synthesis pathway was identified, and further genetic and pharmacological methods confirmed this pathway being essential for EZH2i non-responsive GCB-DLBCL cell lines.
Combined pharmacological inhibition of EZH2 and cholesterol synthesis was highly effective in targeting GCB-DLBCL cell lines. This dependency on endogenous cholesterol synthesis related to defective uptake of exogenous cholesterol, due to an impaired cycling of the LDL receptor (LDLR) upon EZH2 inhibition. Interestingly, further analysis revealed a critical role of EZH2 in controlling the trafficking of other membrane proteins by Clathrin-Mediated Endocytosis (CME), also responsible for LDLR recycling.
Combined targeting with EZH2 and cholesterol biosynthesis inhibitors synergizes in controlling GCB-DLBCL. Our data identify an unknown link between EZH2 and cholesterol uptake via CME of LDLR. The defect in cholesterol uptake upon EZH2 inhibition renders the cells strictly dependent on endogenous cholesterol biosynthesis. Consequently, co-targeting of the epigenome and metabolome provides an innovative and exploitable intervention strategy for GCB-DLBCL.