UVB induces cutaneous squamous cell carcinoma progression by de novo ID4 methylation via methylation regulating enzymes

Abstract

Background: Little is known about whether UVB can directly influence epigenetic regulatory pathways to induce cutaneous squamous cell carcinoma (CSCC). This study aimed to identify epigenetic-regulated signalling pathways through global methylation and gene expression profiling and to elucidate their function in CSCC development. Methods: Global DNA methylation profiling by reduced representation bisulfite sequencing (RRBS) and genome-wide gene expression analysis by RNA sequencing (RNA-seq) in eight pairs of matched CSCC and adjacent normal skin tissues were used to investigate the potential candidate gene(s). Clinical samples, animal models, cell lines, and UVB irradiation were applied to validate the mechanism and function of the genes of interest. Findings: We identified the downregulation of the TGF-b/BMP-SMAD-ID4 signalling pathway in CSCC and increased methylation of inhibitor of DNA binding/differentiation 4 (ID4). In normal human and mouse skin tissues and cutaneous cell lines, UVB exposure induced ID4 DNA methylation, upregulated DNMT1 and downregulated ten-eleven translocation (TETs). Similarly, we detected the upregulation of DNMT1 and downregulation of TETs accompanying ID4 DNA methylation in CSCC tissues. Silencing of DNMT1 and overexpression of TET1 and TET2 in A431 and Colo16 cells led to increased ID4 expression. Finally, we showed that overexpression of ID4 reduced cell proliferation, migration, and invasion, and increased apoptosis in CSCC cell lines and reduced tumourigenesis in mouse models. Interpretation: The results indicate that ID4 is downregulated by UVB irradiation via DNA methylation. ID4 acts as a tumour suppressor gene in CSCC development.

Epigenetic and metabolic interplay in cutaneous squamous cell carcinoma

“…68,69 For its part, the maintenance DNA methyltransferase, DNMT1, was recently shown to be upregulated in human UVB-radiation induced cSCC patient samples while the DNA demethylation enzymes TET1 and TET2 were downregulated resulting in silencing of tumor suppressors. 70 TET enzymes are responsible for active DNA demethylation through a series of oxidation events that are replication independent. TET enzymes are highly mutated in hematopoietic cancers as well as solid tumors, including cSCC.…”

Methyltransferases in the Pathogenesis of Keratinocyte Cancers

“…In addition to genome-wide methylation profiles, gene-specific DNA methylation changes have been correlated with gene expression alterations in cSCC [ 37 ]. Currently, hypermethylation resulting in transcriptional silencing at the promoters of numerous genes involved in cell cycle regulation, DNA repair, epithelial adhesion, and signal transduction has been shown to be a recurring pattern of DNA methylation changes related to cSCC [ 38 ].…”

“…The epigenetic silencing of ID4 can lead to uncontrolled growth of cancer cells via this pathway, suggesting a role of ID4 silencing in tumorigenesis. Similarly, DNMT1 upregulation and TET downregulation accompanied ID4 methylation in cSCC tissues, collectively suggesting that ID4 is downregulated by UVR irradiation via DNA methylation and acts as tumor suppressor gene in cSCC development [ 37 ].…”

“…The WNT signaling network has also emerged as an important regulator in the development and progression of KCs [ 47 ]. Secreted frizzled-related proteins (SFRPs) are known inhibitors of the WNT signaling pathway, binding WNTs directly to prevent receptor binding and the activation of WNT signaling [ 37 ]. The promoter of SFRP3 was hypermethylated in human cSCC, suggesting that loss of SFRP3 and subsequent WNT activation led to metastatic cSCC [ 48 ].…”

Loss of retinoic acid receptor-related receptor alpha (Rorα) promotes the progression of UV-induced cSCC

“…What is more, the expression profile of cSCC has been quantified by either gene expression chips or RNA-sequencing (RNA-seq) technology, and a large number of differentially expressed genes (DEGs) were detected 5 , 15 . As more and more focuses were received on the process of post-transcription and histone modification, the dissection of pathogenesis behind cSCC are spreading from genetics to epigenetics field 16 , 17 . However, although many significant features were identified enriched or suppressed in cSCC, the key factors underlying the progression of NS to cSCC remains to be elucidated.…”