Identification of a Methylation-Driven Gene Panel for Survival Prediction in Colon Cancer

Abstract

Background: Prediction and improvement of prognosis is important for effective clinical management of colon cancer patients. Accumulation of a variety of genetic as well as epigenetic changes in colon epithelial cells has been identified as one of the fundamental processes that drive the initiation and progression of colon cancer. This study aimed to explore functional genes regulated by DNA methylation and the potential of these DNA methylation changes to become biomarkers predictive of colon cancer prognosis.Methods: Methylation-driven genes (MDGs) were explored by applying an integrative analysis tool (MethylMix) to The Cancer Genome Atlas (TCGA) colon cancer project. TCGA colon cancer patients with available survival information (n=281) were randomly divided into training dataset (50%) for model construction and testing dataset (50%) for model validation. The prognostic MDG panel was identified in the training dataset by combining the Cox regression model with the least absolute shrinkage and selection operator regularization, a widely used approach to penalize the effect of multicollineatity. GSEA was employed to determine functional pathways associated with the prognostic 6-MDG panel. CD40 expression and methylation in colon cancer samples were also examined in datasets (expression profile [GSE8671] and methylation profile [GSE42752]) from Gene Expression Omnibus. Experimental confirmation of DNA methylation in colon cancer cell lines was performed using methylation specific PCR and bisulfite sequencing.Results: We identified and internal validated a prognostic methylation-driven gene panel consisting of six gene members (TMEM88, HOXB2, FGD1, TOGARAM1, ARHGDIB and CD40). High risk phenotype classified by the 6-MDGs panel was associated with cancer-related biological processes, including invasion and metastasis, angiogenesis and tumor immune microenvironment, among others. The prognostic value of the 6-MDGs panel was independent of TNM stage, and its combination with TNM stage and age could help improve survival prediction of colon cancer patients. Additionally, we validated that the expression of CD40 was regulated by promoter region methylation in colon cancer samples and cell lines. Conclusions: The proposed 6-MDGs panel represents a promising signature for estimating overall survival in patients with colon cancer.