WHSC1L1 drives cell cycle progression through transcriptional regulation of CDC6 and CDK2 in squamous cell carcinoma of the head and neck

Abstract

Wolf-Hisrchhorn Syndrome Candidate 1-Like 1 (WHSC1L1) is a protein lysine methyltransferase that is recurrently amplified (8p11.23) in patients with squamous cell carcinoma of the head and neck (SCCHN). In this study, we investigated the oncogenic role of WHSC1L1 in SCCHN. Using immunohistochemistry on tissue microarrays of patients with locoregionally advanced SCCHN, we found that WHSC1L1 is significantly overexpressed in patients with SCCHN, and is associated with poor grade and heavy smoking history. Knockdown of WHSC1L1 expression resulted in significant growth suppression and reduction of H3K36 dimethylation (H3K36me2) in SCCHN cells. Chromatin immunoprecipitation analysis showed that WHSC1L1 and H3K36me2 are enriched in the gene bodies of the cell cycle-related genes CDC6 and CDK2, implying that WHSC1L1 directly regulates the transcription of these genes. According to the importance of CDC6 and CDK2 for G1 to S transition, WHSC1L1 knockdown induced strong G0/G1 arrest which was rescued by introduction of wild-type WHSC1L1 but not by that of enzyme-inactive WHSC1L1. Our results imply that WHSC1L1 and its product H3K36me2 are essential for the transition from G1 to S phase in SCCHN cells and that WHSC1L1 could serve as a rational target for anticancer drug development for patients with head and neck cancer.

WHSC1L1-mediated EGFR mono-methylation enhances the cytoplasmic and nuclear oncogenic activity of EGFR in head and neck cancer

“…Given the absence of correlations with survival and the fact that EGFRK721me1 levels increased significantly in the transition from normal squamous epithelium to dysplasia and SCCHN, EGFRK721me1 may be important in the initial stage of head and neck oncogenesis. This finding is in accordance with our previous report for WHSC1L129.…”

“…We previously reported that WHSC1L1 is significantly overexpressed in SCCHN samples compared to normal epithelium29. To assess the pattern and levels of EGFRK721me1 in SCCHN, we performed immunohistochemical staining of 127 SCCHN samples, 21 normal squamous and 18 dysplastic epithelial samples.…”

“…We previously reported that WHSC1L1 knockdown led to cell cycle arrest at the G2/M phase of bladder and lung adenocarcinoma cancer cells and found CCNG1 (cyclin G1) and NEK7 to be potential downstream genes of WHSC1L128. Furthermore, we recently showed that WHSC1L1 was significantly overexpressed in SCCHN tissues compared to normal epithelium, and its siRNA-mediated knockdown significantly decreased cell viability in SCCHN cells29.…”

“…While we found that WHSC1L1 functions as an oncogene by transcriptionally upregulating CDC6 and CDK2 through H3K36 di-methylation in SCCHN cells29, we further attempted to assess whether the oncogenic activity of WHSC1L1 is also mediated through a non-histone protein substrate(s). In this study, we show that WHSC1L1 mono-methylates lysine 721 in the tyrosine kinase domain of EGFR, and that this methylation enhances activation of its downstream RAS-RAF-MEK-ERK cascade, even without epidermal growth factor stimulation.…”

Genomic, Pathway Network, and Immunologic Features Distinguishing Squamous Carcinomas

“…This encodes a novel methyltransferase recently found to promote monomethylation of histones and signal activation of membrane and nuclear epidermal growth factor receptor (EGFR) (Saloura et al, 2016, 2017). Chr 11q gene KDM2A is a histone demethylase implicated in the activation of genes involved in stemness, differentiation, and inflammation (Chen et al, 2017).…”