H3K36me2 methyltransferase NSD2/WHSC1 promotes triple-negative breast cancer metastasis via activation of ULK1-dependent autophagy.

Metastasis is the primary cause for treatment failure and poor prognosis in patients with triple-negative breast cancer (TNBC). Macroautophagy/autophagy plays a crucial role in tumor growth and metastasis. Genetic or epigenetic regulation of autophagy-related factors alters autophagy levels, which subsequently promotes cancer progression and affects the therapeutic effectiveness. However, the molecular basis for the transcriptional and epigenetic regulation of autophagy in TNBC progression is poorly understood. In this study, we reveal the histone methyltransferase NSD2/WHSC1 (nuclear receptor binding SET domain protein 2) as a novel epigenetic regulator of autophagy in TNBC progression. We demonstrate that the expression of NSD2 is significantly upregulated in TNBC cells and high NSD2 expression is correlated with poor TNBC survival. Elevated expression of NSD2 significantly promotes TNBC metastasis in multiple TNBC models. Mechanistically, ULK1 (unc-51 like autophagy activating kinase 1) is identified as a novel target of NSD2 and NSD2-mediated histone H3K36me2 methylation directly activates ULK1 transcription in TNBC cells. Notably, NSD2-induced ULK1 expression facilitates autophagosome maturation and increases autophagic flux, thus promoting autophagy-related malignancy progression in TNBC. Furthermore, pharmacological inhibition of NSD2 using MS159 and MCTP-39 significantly suppresses TNBC autophagy, growth, and metastasis both in vivo and in vitro. In conclusion, our findings demonstrate a pivotal epigenetic role for the NSD2-H3K36me2 axis in regulating ULK1 expression and identify a novel NSD2-ULK1-autophagy signaling axis in the promotion of TNBC progression, suggesting that NSD2 inhibition may be an effective treatment strategy for TNBC.Abbreviations: CDH2/N-cadherin: cadherin 2; ChIP: chromatin immunoprecipitation; EMT: epithelial-mesenchymal transition; ESR: estrogen receptor; FN1: fibronectin 1; GEPIA: Gene Expression Profiling Interactive Analysis; H3K36me2: di-methylation at lysine 36 of histone 3; H&E: hematoxylin and eosin; HDM: histone demethylase; HMT: histone methyltransferase; HIF1A/HIF-1α: hypoxia inducible factor 1 subunit alpha; IF: Immunofluorescence; IHC: Immunohistochemistry; NSD: nuclear receptor binding SET domain protein; PGR: progesterone receptor; qRT-PCR: quantitative RT-PCR; TCGA: The Cancer Genome Atlas; TNBC: triple-negative breast cancer; TSS: transcription start site; ULK1: unc-51 like autophagy activating kinase 1.