EZH2 upregulates the PI3K/AKT pathway through IGF1R and MYC in clinically aggressive chronic lymphocytic leukaemia. Issue 11 (2nd November 2019)

• Record Type: Journal Article
• Authors: Kosalai, Subazini Thankaswamy; Morsy, Mohammad Hamdy Abdelrazak; Papakonstantinou, Nikos; Mansouri, Larry; Stavroyianni, Niki; Kanduri, Chandrasekhar; Stamatopoulos, Kostas; Rosenquist, Richard; Kanduri, Meena
• Is Part Of: Epigenetics. Volume 14:Issue 11(2019)
• Page Start: 1125
• Page End: 1140
• Publication Date: 2019-11-02
• Subjects: Chronic lymphocytic leukemia -- EZH2 -- ChIP sequencing -- PI3K pathway -- IGFR1; Epigenesis -- Periodicals; Epigenetica; 572.86505
• DOI: 10.1080/15592294.2019.1633867
• Languages: English
• ISSNs: 1559-2294

Abstract

ABSTRACT: EZH2 is overexpressed in poor-prognostic chronic lymphocytic leukaemia (CLL) cases, acting as an oncogene; however, thus far, the EZH2 target genes in CLL have not been disclosed. In this study, using ChIP-sequencing, we identified EZH2 and H3K27me3 target genes in two prognostic subgroups of CLL with distinct prognosis and outcome, i.e., cases with unmutated (U-CLL, n = 6) or mutated IGHV genes (M-CLL, n = 6). While the majority of oncogenic pathways were equally enriched for EZH2 target genes in both prognostic subgroups, PI3K pathway genes were differentially bound by EZH2 in U-CLL versus M-CLL. The occupancy of EZH2 for selected PI3K pathway target genes was validated in additional CLL samples (n = 16) and CLL cell lines using siRNA-mediated EZH2 downregulation and ChIP assays. Intriguingly, we found that EZH2 directly binds to the IGF1R promoter along with MYC and upregulates IGF1R expression in U-CLL, leading to downstream PI3K activation. By investigating an independent CLL cohort (n = 96), a positive correlation was observed between EZH2 and IGF1R expression with higher levels in U-CLL compared to M-CLL. Accordingly, siRNA-mediated downregulation of either EZH2, MYC or IGF1R and treatment with EZH2 and MYC pharmacological inhibitors in the HG3 CLL cell line induced a significant reduction in PI3K pathway activation. In conclusion, we characterize for the first time EZH2 target genes in CLL revealing a hitherto unknown implication of EZH2 in modulating the PI3K pathway in a non-canonical, PRC2-independent way, with potential therapeutic implications considering that PI3K inhibitors are effective therapeutic agents for CLL.