Abstract 3718: NSD histone methyltransferases drive cell proliferation in HPV-negative head and neck squamous cell carcinoma (HNSCC)

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Abstract Histone modifications play important role in regulating the function and structure of chromatin. Abnormal histone methylation is often detected during tumor development and progression. NSD1, NSD2, and NSD3 are key histone methyltransferases (HMTs) that catalyze lysine 36 dimethylation (K36me2) at histone H3. Inactivating NSD1 mutations are frequent in head neck squamous cell carcinoma (HNSCC) commonly occur in HPV-negative oropharyngeal (OP) carcinoma and laryngeal carcinomas (LC), and define a novel prognostic subtype in LC, where they associate with dramatically improved overall and progression-free survival. Here, we explored the biological impact of the loss of function of NSD1 in head neck squamous carcinoma (HNSCC). First, we discovered that HNSCC cells with a damaging mutation in NSD1 have reduced K36me2 methylation levels relative to NSD1 wild-type HNSCC cells. Second, we also found slower cell proliferation in NSD1 mutant cell line (SCC4) in comparison with other NSD1 WT cell lines. To further investigate the biologic impact of NSDs, we knocked down NSD1 and NSD2 with shRNA in different histologic subtypes of HNSCC cell lines (JHU011, JHU022, Cal27, and FaDu cell lines). We discovered that depletion of NSD1 and NSD2 results in a reduction of K36me2 and a significant decrease in cell proliferation and clonogenic formation in HNSCC, but not in lung cancer cells. Next, we performed a flow cytometry-based assay and found that NSD1/NSD2 depletion in HNSCC cells causes a significant increase in apoptosis level. We also probed for gene expression and signaling in HNSCC cells following NSD1 depletion using RNA sequencing and reverse protein phase array (RPPA) approaches. From a list of RPPA candidate targets of NSD1, we confirmed the decrease in the protein and mRNA level of Phosphatidylinositol-5-Phosphate 4-Kinase Type 2 Beta (PIP4K2B), but not other members of this family (PIP4K2A and PIP4K2C). PIP4K2B may regulate the ratio of lipid messengers PI5P and PI(4,5)P2 (substrate and reaction product, respectively). The level of phosphorylation of mitogen-activated kinase p70S6 was also decreased under NSD1 knockdown. PIP4K2B siRNA depletion has also led to a significant decrease in HNSCC proliferation. Taken together, this data supports the idea that NSD1 is required for HNSCC cell proliferation via PIP4K2B. Downstream signaling, gene expression effects, and possible cell cycle regulation by NSD enzymes remain to be investigated in more detail. Further, NSDs might be attractive targets for drug development, and targeting NSD1/NSD2 enzymes may be a new strategy for improving outcomes in HNSCC patients. Citation Format: Iuliia Topchu, Rajendra Pangeni, Igor Bychkov, Petr Makhov, John Karanicolas, Jindan Yu, Erica Golemis, Jochen Lorch, Yanis Boumber. NSD histone methyltransferases drive cell proliferation in HPV-negative head and neck squamous cell carcinoma (HNSCC) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3718.