Suppression of retinoid X receptor alpha and aberrant β-catenin expression significantly associates with progression of colorectal carcinoma.

To investigate retinoid X receptor alpha (RXRα) and β-catenin expression and their relationship with the clinicopathological features of colorectal carcinoma (CRC). Real-time PCR and western blot analyses revealed that β-catenin and RXRα expression at both mRNA and protein levels in four pairs of fresh CRC and adjacent non-tumour tissues (ANT) dramatically was increased and decreased in CRC compared with ANT, respectively. Furthermore, RXRα expression at both mRNA and protein levels was downregulated in higher histological grade CRC. Immunohistochemistry staining in 120 cases of CRC and 60 cases of lymph node metastatic carcinoma of CRC showed that RXRα expression was significantly suppressed in CRC compared with ANT (P<0.001) and low expression of RXRα in CRC was significantly associated with histological grade (P<0.001), TNM stage (P=0.022) and N classification (P=0.002). The aberrant (accumulated cytoplasm or/and nuclei) expression of β-catenin was higher in CRC than that in ANT (P<0.001) and associated with histological grade (P=0.001) and N classification (P=0.002). Moreover, there was a close relationship between low RXRα expression and aberrant β-catenin expression in CRC (P=0.032). Taken together with our previous study, aberrant β-catenin expression upregulated by suppression of RXRα may play a crucial role in pathogenesis and progression of CRC.