Relationship between the protein expression of ARID1A, ARID1B and ARID2 with the clinicopathological characteristics of colorectal cancer

Abstract

The SWitch/sucrose non-fermentable chromatin remodeling complex functions as a tumor suppressor by regulating gene expression and thus various cellular processes. Key subunits of this complex, including the AT-rich interactive domain (ARID)-containing proteins ARID1A, ARID1B and ARID2, are frequently mutated in cancer, including colorectal cancer (CRC). However, their protein expression and prognostic significance in CRC remain unclear. The present study investigated the ARID1A, ARID1B and ARID2 expression levels in CRC tissues and their relationship with the clinicopathological characteristics of patients. Bioinformatics analysis of The Cancer Genome Atlas-colon adenocarcinoma cohort revealed frequent mutations, positive mRNA correlations among the ARID genes and increased promoter methylation levels. Immunohistochemical analysis of 63 CRC tissue samples demonstrated significantly decreased ARID1A, ARID1B and ARID2 protein expression in cancerous areas compared with adjacent non-cancerous areas of the tissues. Low ARID1A and ARID1B expression levels were significantly associated with advanced clinicopathological characteristics in Thai patients with CRC. All three ARIDs showed a trend towards an association with the 5-year progression-free survival of Thai patients with CRC. Kaplan-Meier plotter database analysis further demonstrated that low expression of all three ARID genes was associated with a shorter overall survival time in patients with CRC; however, only ARID1A expression showed a statistically significant prognostic relevance. In conclusion, the ARID1A, ARID1B and ARID2 expression levels were shown to be positively correlated, and their reduced expression was associated with worse clinicopathological characteristics in patients with CRC. These findings suggest the potential of ARIDs as prognostic biomarkers, warranting further investigation to validate their clinical significance.

Keywords: AT-rich interactive domain 1A; AT-rich interactive domain 1B; AT-rich interactive domain 2; colorectal cancer; immunohistochemistry.

Figure 1

Gene mutations, expression correlations and promoter methylation levels of ARID1A, ARID1B and ARID2 in COAD. (A) Genetic alterations of ARID1A, ARID1B and ARID2 in patients from TCGA-COAD cohort, analyzed using the Cancer Virtual Cohort Discovery Analysis Platform. Expression correlations between (B) ARID1A and ARID1B, (C) ARID1A and ARID2 and (D) ARID1B and ARID2 in TCGA-COAD cohort, analyzed via the Gene Expression Profiling Interactive Analysis 2 platform. The promoter methylation level of (E) ARID1A, (F) ARID1B and (G) ARID2 in TCGA-COAD samples, analyzed via The University of ALabama at Birmingham CANcer data analysis portal. ^**P<0.01. ARID, AT-rich interactive domain; COAD, colon adenocarcinoma; TCGA, The Cancer Genome Atlas.

Figure 2

ARID1A, ARID1B and ARID2 protein expression in colorectal cancer tissues. Immunohistochemistry of (A) ARID1A, (B) ARID1B and (C) ARID2 proteins in the adjacent non-cancerous area compared with the cancerous area. ARID protein staining appears brown (magnification, x400; scale bar, 20 µm). The H-score of (D) ARID1A, (E) ARID1B and (F) ARID2 protein expression in the non-cancerous area (black bar) compared with the cancerous area (white bar). The data are presented as the mean ± SEM and analyzed by the Mann-Whitney U test. (G) Distribution of ARID1A, ARID1B and ARID2 expression categorization in adjacent non-cancerous and cancerous areas. Expression is classified as low or high depending on the median H-score. ARID1A cut-off, 164; ARID1B cut-off, 100; ARID2 cut-off, 78. ^*P<0.05, ^**P<0.01 and ^***P<0.001. ARID, AT-rich interactive domain; H-score, histoscore; SEM, standard error of the mean; NA, adjacent non-cancerous area; CA, cancerous area.

Figure 3

Expression correlations of ARID1A, ARID1B and ARID2 protein in colorectal cancer. Scatterplots showing the relationships between (A) ARID1A and ARID1B, (B) ARID1A and ARID2 and (C) ARID1B and ARID2. (D) Heatmap of Spearman's correlation coefficients among the ARID proteins. ^*P<0.05. ARID, AT-rich interactive domain; H-score, histoscore.

Figure 4

Relationship between ARID1A, ARID1B and ARID2 protein expression and the survival outcomes of patients with CRC. The 5-year progression-free survival outcomes based on the expression status of (A) ARID1A, (B) ARID1B and (C) ARID2 in patients with CRC (n=63), analyzed using log-rank test. Overall survival based on the expression status of (D) ARID1A, (E) ARID1B and (F) ARID2 in patients with CRC, analyzed using the KM plotter database. The KM plots for overall survival were generated directly by the KM plotter tool without any additional statistical analysis or modification. A late-stage crossover was observed in the survival curves, as provided by the tool. ^*P<0.05. ARID, AT-rich interactive domain; CRC, colorectal cancer; KM, Kaplan-Meier.