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NRF2 and Ara-C resistance in MDS
resulted in a significant reduction of Ara-C IC50 in SKM- 1 (72 h Ara-C IC50, 2.20 mM vs. 0.87 mM; P=0.001) (Figure 2F) and MLLPTD/WT/RUNX1-S291fs (48 h Ara-C IC50, 0.37 mM vs. 0.25 mM; P=0.049) (Online Supplementary Figure S4E). Knockdown of NRF2 enhanced apoptosis induced by Ara-C in MDS cell lines (Figure 2G and Online Supplementary Figure S4F). We also found that NRF2 silenced MDS cell lines after Ara-C treatment tended to be arrested in the S phase (Online Supplementary Figure S4G-J).
DUSP1 is an NRF2 direct target gene in MDS
To further investigate the mechanisms involved in NRF2-mediated Ara-C resistance, we also analyzed pub- lished gene expression profiles of Ara-C-sensitive and Ara- C-resistant AML patient samples. Our analysis indicated that a group of NRF2 target genes might be responsible for Ara-C resistance in AML (P=0.032) (Figure 3A). Leading edge genes are shown in Online Supplementary Appendix List 3. After overlapping the up-regulated NRF2 target genes in high-risk MDS patients (total 132 genes) and Ara-
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Figure 3. DUSP1 is an NRF2 target gene in myelodysplastic syndrome (MDS). (A) Gene set enrichment plot showed that NRF2 target genes were enriched in cytara- bine (Ara-C)--resistant acute myeloid leukemia (AML) patients. (B) Overlap of up-regulated NRF2 target genes in higher-risk MDS patients and Ara-C-resistant AML patients. (C) The gene list of 37 overlapped genes. (D) ChIP sequence analysis of published data24 indicated the NRF2 binding site in the region of DUSP1 gene. (E) NRF2 binding sites in the regions of NQO1 and DUSP1 genes. TSS: transcription start site; TTS: transcription termination site. (F) NRF2 ChIP q-PCR analysis of SKM- 1 cells.
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