DNA methylation contributes toward silencing of antioncogenic microRNA-203 in human and canine melanoma cells

Abstract

Melanoma is a poor-prognosis cancer in both humans and dogs. We have elucidated the antitumor mechanisms of antioncogenic microRNA (miR)-203 which is downregulated in human melanoma, as well as in canine melanoma. The aim of this study was to clarify the mechanism of this downregulation. We focused on epigenetic aberration of miR-203 transcription. Treatment with 5-aza-2'-deoxycitidine (5-aza) markedly upregulated the expression level of miR-203 in almost all of the cell lines tested. Furthermore, bisulfite sequencing or methylation-specific PCR showed DNA methylation of CpG islands upstream of the miR-203 coding region (MIR203) in both human and canine melanoma cells, as well as in canine clinical specimens, but not in human normal melanocytes. The results of a luciferase activity assay showed obvious suppression of the transcription of miR-203 by DNA methylation. The use of the luciferase activity assay for CREB1 and an inhibition assay of miR-203 function performed with an miR-203 inhibitor confirmed the contribution of miR-203 upregulation toward the negative regulation of the target gene of miR-203. These results indicate that canine melanoma might be a preclinical model of human melanoma for epigenetic studies. In addition, this study suggests that agents that can demethylate MIR203 could be a common promising therapeutic agent for the treatment of human and canine melanomas.

Aberrant DNA methylation in melanoma: biomarker and therapeutic opportunities

“…Ectopic expression of miR-211 in melanoma is associated with decreased cell growth during hypoxia [59]. DNA methylation is also thought to regulate the expression of miR-203 [61]. miR-203 ectopic expression was reported to decrease cell invasion by targeting the Polycomb group gene BMI1 in melanoma [62].…”

Concise Review: Stem Cell Trials Using Companion Animal Disease Models

“…Homology of gene sequences in healthy tissues and tumors is more extensive between humans and companion animals (e.g., dogs and cats), than between humans and rodents [7][8][9][10][11][12]. The epigenomic behavior (e.g., DNA methylation) of canine and human tumor cells strongly resembles each other [13][14][15][16]. Thus, data from companion animal research have significant potential to illuminate disease pathogenesis and mechanisms of treatment resistance, while also testing the potential benefits of humanready, but untested therapies.…”

Bosutinib, an SRC inhibitor, induces caspase‐independent cell death associated with permeabilization of lysosomal membranes in melanoma cells

“…In addition, we confirmed that miR‐203 directly targeted SRC (Figure S1A‐C, Supporting Information). Earlier, we have reported that miR‐203 is downregulated and acts as an anti‐oncogene in melanoma cells . Therefore, SRC is considered to be not only activated but also possibly be overexpressed in canine and human melanoma cells.…”

“…On the other hand, SRC is known to be a target gene of anti‐oncogenic microRNA (miR)‐203 in several kinds of human cancers . Recently, we reported that miR‐203 is downregulated by DNA methylation and exhibits anti‐oncogenic functions in melanoma cells . Based on these findings, we hypothesized that SRC is overexpressed and a promising therapeutic target in melanoma.…”