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Combinatorial Ixazomib and Belinostat Therapy Induce Nuclear Factor Erythroid 2-Related Factor 2 (NRF2)-Dependent Apoptosis in Hodgkin and T-cell Lymphoma

ABSTRACT: Ixazomib has documented pre-clinical activity in T cell (TCL) and Hodgkin (HL) lymphoma models with transcriptomic analyses predicting synergistic activity in combination with histone deacetylase (HDAC) inhibition. In the present study, we determined the mechanistic basis for synergism with ixazomib in combination with the HDAC inhibitor, belinostat, in HL and TCL cells lines (ixazomib-sensitive and -resistant clones) and primary tumor cells. In ixazomib-treated TCL and HL cells, we observed induction of proteasomal gene expression and NRF2 as a prominent upstream regulator. Ixazomib treatment in TCL and HL cells resulted in transient inhibition followed by full recovery of proteasomal activity within 72 hours. Furthermore, transcriptomic analysis following belinostat treatment resulted in downregulation of both NRF2 and proteasomal gene expression (validated by qPCR) without direct impact on proteasomal activity in Jurkat and L428. In addition, CRISPR/Cas9 mediated knockdown of NRF2 in Jurkat cells resulted in a significant decrease in cell viability with ixazomib compared with untreated control cells. Using transcriptomic and proteosomal activity evaluation of ixazomib, belinostat or ixazomib+belinostat treated cells, we observed that NRF-2, proteasome gene expression and functional recovery were abrogated by the combination. We also confirmed that ixazomib/belinostat resulted in synergistic activity in ixazomib-sensitive and -resistant cell lines and primary cells. Altogether, these results suggest that the synergistic activity of ixazomib and belinostat is mediated via inhibition NRF2-dependent proteasomal recovery and extended proteasomal inhibition culminating in increased cell death. Further investigation is warranted to determine the full biological role for NRF2 as a response modifier in proteasomal targeted therapies.

ORGANISM(S): Homo sapiens

PROVIDER: GSE126768 | GEO | 2019/04/01

REPOSITORIES: GEO

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Project description:We examined the biological effects of a potent second-generation proteasome inhibitor, ixazomib, in T-cell lymphoma and Hodgkin lymphoma cell lines and human xenograft models. Ixazomib resulted in time- and dose-dependent cytotoxicity and apoptosis in all cell lines (IC50’s <75nM). In vivo studies via SCID tumor xenografts showed significant inhibition of tumor growth (P<0.001) with significantly improved survival (P<0.001) in Jurkat and L540 models with ixazomib-treated mice versus controls. Through global transcriptome and network analyses, ixazomib-treated Jurkat and L540 cells showed significant overlap in biological functions involved in regulation of cell cycle, chromatin modification, and DNA repair processes with a lack of conservation observed in a relatively ixazomib-resistant cell line, L428. Moreover, the predicted activation and inhibition status of tumor suppressors and oncogenes strongly favored ixazomib inhibition of tumor progression. Most notably, ixazomib down-regulated protein levels of MYC and its target genes. Additionally, chromatin immunoprecipitation showed that histone H3 acetylation affected MYC levels and cell death response to ixazomib. Furthermore, inhibition of MYC with JQ1 resulted in synergistic cell death in L428, which was confirmed utilizing MYC knockout. Collectively, ixazomib down-regulated MYC and downstream substrates in TCL and HL, while resistance appeared mediated through MYC- and CHK1-dependent mechanisms. Jurkat (TCL)and L540 cells were treated with ixazomib for 24 hours, RNA was isolated using RNeasy Minikit (Qiagen), following instructions recommended supplied by the manufacturer. Purity and the yield of isolated RNA was determined using Bioanalyzer. These experiments were performed in biological triplicates. Microarray experiment with Jurkat and L540 was performed Affy Human Gene Chip 2.0, at UMASS Medical School Genomic Core facility. Data for Jurkat and L540 cell lines were background adjusted and quantile normalized using RMAExpress. Statistically relevant genes were determined by applying LIMMA with a FDR < 0.05 that resulted in 764 significant genes for the Jurkat experimental group and 5819 significant genes for the L540 experimental group.

Project description:We examined the biological effects of a potent second-generation proteasome inhibitor, ixazomib, in T-cell lymphoma and Hodgkin lymphoma cell lines and human xenograft models. Ixazomib resulted in time- and dose-dependent cytotoxicity and apoptosis in all cell lines (IC50’s <75nM). In vivo studies via SCID tumor xenografts showed significant inhibition of tumor growth (P<0.001) with significantly improved survival (P<0.001) in Jurkat and L540 models with ixazomib-treated mice versus controls. Through global transcriptome and network analyses, ixazomib-treated Jurkat and L540 cells showed significant overlap in biological functions involved in regulation of cell cycle, chromatin modification, and DNA repair processes with a lack of conservation observed in a relatively ixazomib-resistant cell line, L428. Moreover, the predicted activation and inhibition status of tumor suppressors and oncogenes strongly favored ixazomib inhibition of tumor progression. Most notably, ixazomib down-regulated protein levels of MYC and its target genes. Additionally, chromatin immunoprecipitation showed that histone H3 acetylation affected MYC levels and cell death response to ixazomib. Furthermore, inhibition of MYC with JQ1 resulted in synergistic cell death in L428, which was confirmed utilizing MYC knockout. Collectively, ixazomib down-regulated MYC and downstream substrates in TCL and HL, while resistance appeared mediated through MYC- and CHK1-dependent mechanisms. L428 cells were treated with 25nM ixazomib for 24 hours, RNA was isolated using RNeasy Minikit (Qiagen), following instructions recommended supplied by the manufacturer. Purity and the yield of isolated RNA was determined using Bioanalyzer. These experiments were performed in biological triplicates. Microarray experiment with L428 was performed using Human HT 12 Genechip Illumina. Data for the L428 cell line was corrected through normalization of the housekeeping genes, quantile normalized, and then statistically relevant genes were determined with one-way ANOVA analysis with FDR <0.05.

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Combinatorial Ixazomib and Belinostat Therapy Induce Nuclear Factor Erythroid 2-Related Factor 2 (NRF2)-Dependent Apoptosis in Hodgkin and T-cell Lymphoma

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