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

To investigate retinoid X receptor alpha (RXR alpha) and beta-catenin expression and their relationship with the clinicopathological features of colorectal carcinoma (CRC). Real-time PCR and western blot analyses revealed that beta-catenin and RXR alpha 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, RXR alpha 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 RXR alpha expression was significantly suppressed in CRC compared with ANT (P < 0.001) and low expression of RXR alpha 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 beta-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 RXR alpha expression and aberrant beta-catenin expression in CRC (P = 0.032). Taken together with our previous study, aberrant beta-catenin expression upregulated by suppression of RXR alpha may play a crucial role in pathogenesis and progression of CRC. (C) 2011 Elsevier Ltd. All rights reserved.