Exosomal MEF2C's Association With the Progression of CRC in Regulating CD36 Transcription.

CONTEXT

Exosomes are biologically active, extracellular vesicles that are involved in tumor-related processes, including activating tumors, facilitating tumor growth, and promoting inflammation.

OBJECTIVE

The study intended to investigate microRNAs (miRNAs) in exosomes that are associated with colorectal cancer (CRC).

DESIGN

The research team performed bioinformatics analysis, extracting RNA-sequencing (RNA-seq) datasets from the Cancer Genome Atlas (TCGA); ExoRBase, a database of different types of RNA information that scientists have extracted from human exosomes; and the Gene Expression Omnibus (GEO) databases, and analyzed the data.

SETTING

The study took place at the Department of Colorectal Surgery at the Chinese Academy of Medical Sciences and Peking Union Medical College in Beijing, China.

PARTICIPANTS

From October 2020 to March 2021, a total of 28 CRC patients who underwent curative resection at the National Cancer Center were enrolled. Tumor samples and tumor-adjacent normal sample were obtained from these CRC patients. Postoperative pathological characteristics all shown adenocarcinoma. The research team recruited participants from the hospitals connected with CAMS and PUMC and obtained written informed consent from them for publication of a case report and any accompanying images. The Ethics Committee of the Cancer Institute (Hospital), CAMS & PUMC has officially recognized the study (NCC 2017-YZ-026).

OUTCOME MEASURES

The research team: (1) extracted RNA-seq datasets from the TCGA, exoRBase and GEO and analyzed the differentially expressed genes (DEGs); (2) performed a cluster analysis of variant genes using weighted gene co-expression network analysis (WGCNA);(3) verified expression of myocyte enhancer factor 2C-genecards (MEF2C) and cluster of differentiation 36 (CD36) in CRC tissues; (4) explored the biological function of the MEF2C by performing proliferation, migration, and invasion assays; and (5) used a chromatin immunoprecipitation (ChIP) experiment to analyze mechanisms to reveal CD36 transcription regulated by exosomal MEF2C.

RESULTS

A significant mean difference in exosomal MEF2C existed between normal and tumor tissues. By performing a correlation analysis, the research team found 609 potential target points of exosomal MEF2C (r > 0.5, P < .05). Weighted correlation network analysis (WGCNA) and protein-protein interaction (PPI) network analysis indicated that CD36 may be the target of exosomal MEF2C. Univariate, multivariate, and Kaplan-Meier analyses showed that CD36 was closely related to the overall survival (OS) of CRC patients. Obvious differences existed in the expression levels of MEF2C and CD36 in CRC and normal tissues according to qPCR and immunohistochemical assays. Functional-experiments analysis in vitro showed that exosomal-MEF2C could be considered as an antioncogene. Mechanistically, ChIP assays showed that MEF2C regulated the transcriptional level of CD 36; thus, the expression of CD36 increased significantly.

CONCLUSION

MEF2C is a potential biomarker of a favorable prognosis in CRC and is related to the progression of CRC. Moreover, the MEF2C-CD36 pathway may reveal the tumor regulation mechanism in CRC. The exosomal MEF2C was the hub gene in exosomes, with CD36 was identified as the potential target. Exosomal MEF2C may be a promising molecular biomarker for predicting a good prognosis and may have potential as a medical target for CRC.