Study of P33 Tumor Suppressor Protein Expression in Normal and Cancerous Colorectal Tissues

P33 (ING1b) is a tumor suppressor protein involved in growth control and apoptosis. Suppression of P33 expression is associated with the loss of cellular growth control suppression. Colorectal cancer is the second most common malignancy in the world. Detection of the disease at an early stage can reduce mortality. To investigate the role of P33 in colorectal carcinoma pathogenesis, we evaluated P33 expression in colorectal cancer patients by immunohistochemistry. P33 protein expression from 70 colorectal cancer specimens and their matched normal colorectal sections from the series of colorectal cancer patients was examined in paraffin–embedded material by immunohistochemistry. The proportions of cellular staining for P33 were estimated under light microscopy by using Motic Advanced Plus 2 soft ware. P33 was expressed in all tissues, and was mainly localized in the nuclei of epithelial cells. P33 was down-regulated in the colorectal cancer specimens, compared with the matched tissues (P = 0.002). Expression of P33 in cancer tissues was significantly lower than normal tissues. This study showed that P33 expression may be associated with pathogenesis of colorectal cancer.