Immunohistochemical expression of mutant p53 oncogene in trans...

The purpose of this study was to analyze the expression of a mutant (MUT) p53 oncogene protein in the mucosal crypts adjacent to a human colon cancer. Five 1-cm mucosal segments were taken from the surgical specimens over a 5-cm distance from the tumor. Immunohistochemistry was performed using a monoclonal antibody (Ab3) to the MUT p53 and examination by light microscopy. The mean % labelling index (LI) of 10 crypts/cm segment was determined by image analysis. The LI for the entire crypt length for the first cm segment was 33.51 +/- 4.2 and for the second cm segment was 29.26 +/- 5.4 (p < 0.02). Due to the unequal distribution of the label within the crypt length, it was divided into halves so that the LI of these levels could be determined. The LI for the upper and lower crypt levels for the first cm segment were 28.67 +/- 3.2 and 78.23 +/- 4.6 (p < 0.01); for the second segment, the LI were 22.0 +/- 5.1 and 68.66 +/- 4.7 (p < 0.01). No expression of MUT p53 nuclear protein was noted distally at 3-5 cm. The localization of MUT p53 protein product to the crypt stem cell nucleus supports the contention that a malignant field change exists in the transitional mucosa adjacent to a human colon cancer.