NSD2 activates the E2F transcription factor 1/Y-box binding protein 2 axis to promote the malignant development of oral squamous cell carcinoma

Highlights

• NSD2 was highly expressed in OSCC tissues and cells.

• Knockdown of NSD2 reduces OSCC cell growth in vitro and in vivo.

• Silencing of NSD2 suppresses E2F1 expression in OSCC cells.

• E2F1 promotes YBX2 transcription and augments OSCC cell growth.

• NSD2 promotes OSCC cell growth through the E2F1/YBX2 axis.

Abstract

Objective

Nuclear receptor-binding SET domain protein 2 (NSD2) belongs to the SET histone methyltransferase family with potential oncogenic roles. This study aimed to probe the roles of NSD2 and its relevant molecules in oral squamous cell carcinoma (OSCC).

Methods

An OSCC-related GSE138206 dataset was analyzed to identify potential key genes implicated in OSCC development. NSD2 expression in OSCC tissues and cells was examined. NSD2 silencing was administrated in OSCC cells to examine its function in cell growth in vitro and in vivo. Downstream molecules mediated by NSD2 were predicted using bioinformatic tools. Rescue experiments of E2F transcription factor 1 (E2F1) and Y-box binding protein 2 (YBX2) were performed to validate their participation in NSD2-regulated events.

Results

NSD2 was highly expressed in OSCC tissues and cells, along with elevated expression of H3K36me2, a major target of NSD2-mediated methylation. NSD2 silencing significantly reduced proliferation, invasion and epithelial to mesenchymal transition of OSCC cells but induced cell apoptosis, and it reduced growth of xenograft tumors in nude mice. Downregulation of NSD2 led to transcriptional suppression of E2F1 by inhibiting H3K36me2 modification at the E2F1 promoter, while E2F1 transcriptionally activated YBX2. Either upregulation of E2F1 or YBX2 restored the malignant behaviors of OSCC cells suppressed by NSD2 silencing.

Conclusion

This work demonstrates that NSD2 plays an oncogenic role in OSCC by activating E2F1 and YBX2. Silencing of NSD2, E2F1 or YBX2 may help suppress the progression of OSCC.

Introduction

Squamous cell carcinoma (SCC) is the major malignancy of oral mucosa and lip, and oral squamous cell carcinoma (OSCC) makes up 95% of all head and neck cancer and represents one of the major causes of cancer-related death in the world (Choi and Myers, 2008, Panarese et al., 2019, Sharma et al., 2018). The occurrence of OSCC is particularly high in Asia owing to the bad lifestyle habits, such as chewing of betel quid, smoking, drinking, infection and poor oral hygiene (Yu-Duan et al., 2013). Since the tumor formation, the tumor cells may break off from the original sites and migrate to other sites of the body (Matsuura et al., 2018). The metastasis in the setting of late diagnosis is a major cause of death (Irani, 2016, Noguti et al., 2012). Although there are effective therapeutic options by far, such as surgery, radiotherapy and adjuvant chemotherapy, the 5-year survival rate only moderately improved from 63% to 65% during the past decades (He et al., 2019, Zou et al., 2019). It is urgent to identify key molecules implicated in the progression of OSCC, which may help develop novel treating strategies for this malignancy.

Advanced bioinformatic tools have offered great convenience in the quick and concrete identification of key genes implicated in the pathogenesis of diseases (Huang, Wu, Zheng, Shao, & Lv, 2019). In this study, using an OSCC-related GSE138206 dataset from GEO (https://www.ncbi.nlm.nih.gov/geo/), we identified nuclear receptor-binding SET domain protein 2 (NSD2) as a candidate molecule leading to cancerigenesis of OSCC. NSD2 is a member of the SET histone methyltransferase family (Tanaka et al., 2020). The NSD2 protein methylates specific histone sites, including H3 lysine 36 (H3K36me2), an active mark leading to transcriptional activation (Li et al., 2009). NSD2 has reportedly been correlated with malignant development of several human cancers via activating the oncogenic signaling pathways (Garcia-Carpizo et al., 2016, Yang et al., 2012, Zhu et al., 2019) through the epigenetic regulations. Damaging mutation of NSD2 has been correlated with favorable prognosis of laryngeal cancer (Peri et al., 2017), indicating its potential correlation with other SCCs of head and neck (SCCHN), including OSCC. But the exact role of NSD2 in OSCC needs further investigation.

The bioinformatic analyses of this study predicted E2F transcription factor 1 (E2F1) as a target of NSD2, and Y-box binding protein 2 (YBX2) a target of E2F1. E2F1 is a transcriptional activator of the E2F family of transcription factors in higher eukaryotes (Sozzani et al., 2006, pp. 106). It is frequently involved in cancer progression through regulating cell cycle progression as well as epithelial to mesenchymal transition (EMT) and metastatic events (Alla et al., 2010, Gaubatz et al., 2000, Marquardt et al., 2018, Swiatnicki and Andrechek, 2021). As far as YBX2, it is a member of the YBX family of RNA binding proteins correlated with DNA repair, transcription and translation (Kohno, Izumi, Uchiumi, Ashizuka, & Kuwano, 2003). YBX2 has been demonstrated to be correlated with the properties of germ cells and cancer cells (Suzuki et al., 2021). Therefore, there might be a NSD2/E2F1/YBX2 axis involved in the progression of OSCC. This study aimed to validate the interactions between NSD2, E2F1 and YBX2 and their functions in the growth of OSCC cells in vitro and in vivo.