P53 GENETIC ALTERATIONS, PROTEIN EXPRESSION AND AUTOANTIBODIES IN HUMAN COLORECTAL-CARCINOMA - A COMPARATIVE-STUDY

This study investigated a total number of 120 colorectal malignant tum or tissues by applying a new quantitative luminometric assay (LIA)-mat , immunohistochemistry (IHC) (n=100), PCR/SSCP (n=42), and sequencing (n=7). Sera were collected from 235 patients suffering from colorectal carcinoma in addition to 195 healthy individuals as a control group. Manual ELISA kit was developed to detect p53 autoantibodies in the ser a of those patients. Our data demonstrated that the LIA-mat yields rel iable estimates of p53 expression in soluble cell extracts as compared with results obtained by immunohistochemistry which showed positive i mmunostaining in 63% of the studied cases. Using a cut-off value of 1. 8 ng/mg protein, 65 tumors out of 120 (54%) were classified to be posi tive by LIA-mat, manifesting protein overexpression, while 22 out of 4 2 (52%) tumor samples showed p53 gene alteration when applying single strand conformation polymorphism (SSCP) analysis on polymerase chain r eaction products. In tumor samples without a p53 gene alteration, the median soluble p53 protein level was 4.3 ng/mg protein, whereas the me dian p53 protein level for tumor samples with p53 gene alteration was 7.5 times higher. Despite a significant correlation between the outcom e of LIA and SSCP, a disagreement was found in 30% of cases. We found no significant correlation between p53 protein overexpression and clin icopathological findings except for distant metastasis (p=0.33), indic ating p53 immunoreactivity to be an independent prognostic factor. Our data showed that 18% of patients suffering from colorectal cancer dev eloped autoantibodies against p53 in their sera which might be an earl y indicator for tumor development and distant metastasis.