Characterization of the Subcellular Distribution of Phospho--catenin in Colorectal Cancer

Background/Aim: /i-Catenin is a multifunctional protein, which is localized to different subcellular compartments of the normal colon epithelium. The hyperactivation of Wnt pathway results in the nuclear accumulation of /i-catenin and induction of colorectal carcinogenesis. Although N-terminally hypo-phosphorylated /i-catenin (active /i-catenin) is known as the transcriptionally active form, phospho-S33/S37/T41-/icatenin (phospho-/i-catenin) can also accumulate in the nucleus. In this study, we aimed to characterize the subcellular distribution of phospho-/i-catenin and the other forms of /icatenin in normal colon epithelium and colorectal cancer (CRC). Materials and Methods: Phosphorylated, hypo-phosphorylated, and the total pool of /i-catenin were evaluated in colon epithelium and CRC using immunohistochemistry, immunofluorescence staining, and western blotting. Tissue microarrays were used to determine the expression pattern of phospho-/icatenin in CRC samples. Results: Almost 11% (49/452) of CRCs expressed moderate to high levels of phospho-/i-catenin in the nucleus. In addition, hypo-phosphorylated and phosphorylated forms of /i-catenin localized to different subcellular regions in normal colon epithelium and CRC. Immunoblotting experiments suggested that truncated phospho-/i-catenin forms can be found in CRCs. Conclusion: Phospho-/i-catenin accumulates in the nucleus and different molecular weight /i-catenin proteins are present in colon cancer cells. To elaborate on the functional significance of nuclear phospho-/i-catenin, further studies should be performed.