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Histone modifier gene mutations in PTCL-NOS
week), relapsed patients with a histone modifier gene mutation showed a remarkably increased response rate (complete or partial remission), as compared to those without mutations (Figure 3E and Online Supplementary Table S3). Thus, such mutations might alter the protein function on chromatin state regulation, sensitizing PTCL- NOS patients to HDAC inhibitors.
In vitro, Jurkat cells bearing the KMT2D V5486M or EP300 H1377R mutant were treated with different con- centrations of chidamide and/or the hypomethylating agent decitabine for 48 h. The combination index (CI) curve yielded most of the data points to the area <1, denoting synergistic interactions in KMT2D V5486M mutated cells. Meanwhile, the inhibitory effect on EP300
H1377R mutated cells was achieved by chidamide alone (Figure 4A). Flow cytometry revealed that chidamide and decitabine synergistically induced KMT2D V5486M mutated cell apoptosis and G0/G1 arrest (Figure 4B). The in vivo anti-tumor activity of dual treatment on T-cell lym- phoma was further evaluated in a murine xenograft model in which KMT2D V5486M mutated Jurkat cells subcuta- neously injected into nude mice. The tumors formed in mice co-treated with chidamide and decitabine were sig- nificantly smaller than those that formed in untreated ani- mals or those treated with the single agents, starting from 15 days of treatment (Figure 4C, left panel), as visualized by 18F-fluorodeoxyglucose small-animal positron emission tomography – computed tomography at 21 days of treat-
ABC
DE
Figure 3. Effect of histone deacetylase inhibitor in KMT2D-mutated and EP300-mutated T-lymphoma. (A) Structure prediction of the missense mutations. The crys- tal structure of the complex of KMT2D and EP300 is PDB: 4Z4P and PDB: 4PZR, respectively. SAM, S-adenosyl-L-methionine. (B and C) Western blot and immuno- fluoresence assay of Jurkat cells transfected with wild-type (WT), KMT2D mutants (V5486M) (B) and EP300 mutants (H1377R) (C) upon treatment with different HDAC inhibitors. Jurkat cells were treated for 48 h at IC50. Histone 3 (H3) was used as a loading control. VPA, valproic acid, 3.7 mm; SAHA, suberoylanilide hydroxamic acid, 10 mm; ROMI, romidepsin, 5 nm; CHID, chidamide, 5 mm (48 h). Bar=10 mm. (D) Immunostaining of H3K4me3 and H3K18ac in tumor samples of PTCL-NOS patients with or without KMT2D or EP300 mutations. Bar=20 mm. (E) Response rate in relapsed PTCL-NOS patients treated with CHID according to the mutation sta- tus of histone modifier genes.
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