The relationship between ARID1A and epithelial-mesenchymal transition-related proteins expression in differential histological grading of colorectal cancer tissues

Abstract

AT-rich interactive domain-containing protein 1A (ARID1A) is an essential component of the switch/sucrose nonfermentable (SWI/SNF) chromatin remodeling complexes. ARID1A also belongs to the tumor suppressor family, which is involved in gene regulation during carcinogenesis. Previously, ARID1A mutations in colorectal cancer (CRC) resulted in loss of its expression level in CRC specimens and were associated with CRC-related clinicopathologic characteristics. Then, ARID1A has been proposed as a potential prognostic biomarker for CRC prognosis and diagnosis. Using the cBioPortal for cancer genomics database analysis, we found ARID1A mutations in 7.09% of CRCs, in which truncating and missense mutations were mostly found. The protein expression in the ARID1A-mutated group was lower than in the ARID1A non-mutated group. Furthermore, the epithelial-mesenchymal transition (EMT) process plays a crucial role in the progression and aggressiveness of CRC. The altered ARID1A expression is also involved in the EMT process in several cancers. However, the relationship between ARID1A and EMT-related protein expression in human CRC tissues still remains unclear. Thus, this study aimed to investigate the relationship between ARID1A and EMT-related protein expressions using immunohistochemistry (IHC). One hundred formalin-fixed, paraffin embedded (FFPE) blocks of CRC patients, including 65 well-differentiated, 23 moderately differentiated, and 12 poorly differentiated adenocarcinomas, were acquired from Sawanpracharak Hospital, Nakhonsawan, Thailand. The CRC paraffin sections were immunostained with a specific antibody to observe the expression of ARID1A and EMT-related proteins, including epithelial proteins (epithelial-cadherin (E-cad) and zonula occludens-1 (ZO-1)) and mesenchymal proteins (vimentin and fibronectin). The staining intensity and percentage of ARID1A-positive cells were evaluated using a histological (H)-score. A quantitative analysis was performed to evaluate ARID1A and EMT-related protein expressions. The result demonstrated that the immunoreactivity signal of ARID1A was low in most of the cancerous areas of CRC samples (92.00%), while another 8.00% was unchanged. Quantitative analysis using ImageJ Fiji software revealed that the level of ARID1A protein was significantly decreased in the cancerous area when compared to the adjacent non-cancerous area in all three pathological differentiations of CRC (p<0.001). Moreover, the expressions of vimentin and fibronectin were increased, whereas E-cad and ZO-1 were decreased in CRC tissues with low ARID1A expression. The association of ARID1A protein expression with the pathological outcomes and prognosis of the patients was also investigated. The Fisher’s exact test revealed that low expression of ARID1A protein was significantly associated with a greater number of positive lymph nodes, lymphovascular invasion, lymph node metastasis, lymph node ratio, and comorbidity. Moreover, the results of Kaplan-Meier analysis revealed that the 5-year progression-free survival (PFS) of CRC patients tended to be associated with ARID1A expression. Our results may be useful for the clinicopathological assessment and prognosis of patients with CRC, as well as confirm the involvement of ARID1A in cancer progression and EMT process induction.

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