Abstract 2753: Potential novel interventions of oncohistones, epigenetic modifications, and RNA processing machinery in betel-nuts related HNSCC in Taiwan

Abstract Background: Betel nut chewing leads to strong invasion & recurrence. We found betel-nuts exposed HNSCC cell line, TW2.6, caused treatment refractoriness in Taiwan with high PDL1, defective p53 mutation, p16 loss, & BCL2 overexpression. PI3K/AKT/mTOR interventions, ALK/IGF1R inhibitor, CDK4/6 inhibitor, BCl2 inhibitor, WEE1 inhibitor, ATR inhibitor, DNA-PK inhibitor, AT2AR inhibitor, Mcl-1 inhibitor, MEK1/2 inhibitor, JAK2 inhibitor, CXCR4 inhibitor, FAK inhibitor, p53 reactivator, MDM2 inhibitor, SHP2 inhibitor, PARP7 inhibitor, IAP inhibitor, GLS1 inhibitor, eribulin, & VEGFR2/ PDGFR/FGFR or VEGFR2/c-MET/Axl triple blockage might be effective on TW2.6 and reverse treatment refractoriness, through the inhibition of mesenchymal transformation, pRB, & PI3K/AKT /mTOR signaling and modulation of stemness & PD1/PDL1 pathway. Besides, PLK inhibitor & GLS1 inhibitor seemed good radiosensitizers for TW2.6(AACR2024). The genomic signature of TW2.6 was figured out(AACR2020) with PIK3CA H1047R mutation, high TMB/MSS, VEGF-A amplification, p53/MYC/HRAS/DDR2/ PDGFRbeta/EPHB1/ATM mutations, FAT1 loss, amplification of TERT/ FGF10/CCND3/SOX9/IL-7R/SDHA/ RICTOR/FLCN, CDK12/PTPRD loss of function, deletions of STK11/ARID1B/MITF/ TNFAIP3, & SETD2(a histone lysine methyltransferase)/KDM5A(a lysine demethylase)/CDK8 mutations. H3K36 mutation and NSD1 defects altering H3K36 methylation will block cellular differentiation and promote oncogenesis. Disrupting NSD1 in HNSCC cell lines led to CpG hypomethylation & enhanced cisplatin sensitivity. Methods: TW2.6 used to test (1)in vitro drug sensitivity to (a)Chemical Modulators of Splicing; (b)PRMT5 inhibitor; (c)CDK9 inhibitor, EZH2i, DNMT3i, BRD/BET4i, and HDACi; (d)NSD1/SETD2 inhibitor; (e)METTL3 inhibitor; (2)synergistic effects with other therapies by MTT assay, colony formation, flow cytometry, & western blotting. Results: Epigenetic modifications were tested over TW2.6. AZD4573(CDK9 inhibitor), tazemetostat(EZH2 inhibitor), azacitidine(DNMT3 inhibitor), AZD5153(BRD4/BET inhibitor), and romidepsin(HDAC inhibitor) were effective over TW2.6 and enhanced ICIs efficacy. AZD4573 can synergize with tazemetostat, AZD5153, AZD6094(c-MET inhibitor), AZD5991(Mcl-1 inhibitor), & AZD2014(TOC1/2 inhibitor); but no synergistic effects with DDR interventions, such as AZD6738(ATR inhibitor) & olaparib except AZD1775(WEE1 inhibitor). AZD4573 will cause the drop of EMT signals, pRB, & p70S6K1 and prominent elevation of p-PARP. TW2.6 was also effective towards STM2457(METTL3 inhibitor) and JNJ64619178(PRMT5 inhibitor). Conclusions: TW2.6 was sensitive to epigenetic modifications due to CDK8/SETD2/KDM5A mutations & ARID1B loss. Novel RNA processing interventions and epigenetic modifications for radiosensitization & immuno-modulation may be future trends. Citation Format: Jo-Pai Chen, Jui-Ying Chang, Ruey-Long Hong. Potential novel interventions of oncohistones, epigenetic modifications, and RNA processing machinery in betel-nuts related HNSCC in Taiwan [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 2753.