Expression of Indian hedgehog is negatively correlated with APC gene mutation in colorectal tumors.

The regulatory mechanism of Indian hedgehog (IHH) in colorectal carcinogenesis has not been elucidated. In the current study, the expression of IHH were investigated in 7 digestive tract cancer cell lines, and in 10 normal colorectal mucosas (NCs), 30 hyperplastic polyps (HPs), 35 colorectal adenomas (ADs), and 40 colorectal adenocarcinomas (CAs) by semi-quantitative RT-PCR and immunohistochemical staining. Moreover, the mutational status of adenomatous polyposis coli (APC) and β-catenin in these tumors were analyzed by direct sequencing. IHH mRNA was lost in the 4 colon cancer cell lines harboring APC mutation. IHH mRNA was significantly decreased in CAs (0.17 ± 0.22), compared with that in ADs (0.38 ± 0.35) and HPs (0.56 ± 0.38, P < 0.05). IHH protein was expressed at a very low level or absent in both ADs (7.51 ± 11.92) and CAs (5.15 ± 9.21) in comparison to that in HPs (19.47 ± 17.91) and NCs (42.40 ± 13.67, P < 0.05). Moreover, APC mutations were negatively correlated with IHH mRNA expression (Spearman's R = -0.636, P < 0.01) and IHH protein expression (Spearman's R = -0.426, P < 0.01). In conclusion, down-regulation of IHH expression might be an early event during the carcinogenesis of colorectal cancer. The activation of Wnt signaling by APC mutation might contribute to the down-regulation or loss of IHH expression in colorectal tumors.