Down-regulation of Inositol Polyphosphate 4-Phosphatase Type II Expression in Colorectal Carcinoma

Abstract

BACKGROUND/AIM: Aberrant expression of survival signaling pathways causes deregulation of cellular proliferation and resistance to apoptosis, and plays a crucial role in the development, progression and metastasis of cancer. Inositol polyphosphate 4-phosphatase type II (INPP4B) negatively regulates phosphatidylinositol 3-kinase signaling and has a tumor-suppressive role in several human malignancies.

MATERIALS AND METHODS: We analyzed the expression levels of INPP4B mRNA and protein in colorectal carcinoma (CRC) cell lines and tissue samples using western blot, quantitative real-time reverse-transcriptase polymerase chain reaction, and immunohistochemical staining.

RESULTS: Western blot analysis revealed that the CRC cell lines HCT 116, SW620, DLD-1, and WiDr expressed significantly lower levels of INPP4B protein than the normal colonic epithelial cell lines CCD 841 CoTr and FHC. Consistent with these results, INPP4B mRNA expression in the CRC cell lines was significantly lower than in the normal colonic epithelial cells. Immunohistochemical staining revealed that normal colonic mucosa displayed uniform and strong-to-moderate INPP4B immunoreactivity, whereas 60.7% (71/117; p<0.001) and 76.5% (62/81; p<0.001) of the primary and metastatic CRC tissue samples exhibited reduced INPP4B expression, respectively.

CONCLUSION: Our results indicate that INPP4B is down-regulated in CRC and that INPP4B is involved in the development and progression of CRC.