TCF 4 tumor suppressor: a molecular target in the prognosis of sporadic colorectal cancer in humans

BACKGROUND: A huge array of function is played by the Wnt/β-catenin signaling pathway in development by balancing gene expression through the modulation of cell-specific DNA binding downstream effectors such as T-cell factor/lymphoid enhancer factor (TCF/LEF). The β-catenin/TCF-4 complex is a central regulatory switch for differentiation and proliferation of intestinal cells (both normal and malignant). Thus, in the present study we evaluated each of 60 cases of sporadic adenocarcinoma, alongside adjoining and normal mucosa specimens of colorectum in humans, for mutation and expression analysis of the gene coding for TCF-4 protein. METHODS: DNA sequencing following PCR amplification and SSCP analysis (single strand conformation polymorphism) was employed to detect TCF-4 gene mutations in the case of exon 1. Quantitative real-time (qRT) PCR, immunohistochemistry (IHC), confocal microscopy and western blot analysis were used to detect TCF-4 gene/protein expression. RESULTS: Sequencing analysis confirmed 5/60 patients with a point mutation in exon 1 of the TCF-4 gene in tumor samples. mRNA expression using qRT-PCR showed approximately 83% decreased TCF-4 mRNA expression in tumor tissue and adjoining mucosa compared to normal mucosa. Similarly, a significant decrease in protein expression using IHC showed decreased TCF-4 protein expression in tumor tissue and adjoining mucosa compared to normal mucosa, which also corresponds to some important clinicopathological factors, including disease metastasis and tumor grade. Mutational alterations and downregulation of TCF-4 mRNA and hence decreased expression of TCF-4 protein in tumors suggest its involvement in the pathogenesis of CRC. CONCLUSIONS: A remarkable decrease in TCF-4 mRNA and protein expression was detected in tumorous and adjoining tissues compared to normal mucosa. Hence the alterations in genomic architecture along with downregulation of TCF-4 mRNA and decreased expression of TCF-4 protein in tumors, which is in accordance with clinical features, suggest its involvement in the pathogenesis of CRC. Thus, deregulation and collaboration of TCF-4 with CRC could be a concrete and distinctive feature in the prognosis of the disease at an early stage of development.