IMMUNOHISTOCHEMICAL EXPRESSION OF MUTANT P53 ONCOGENE IN TRANSITIONALMUCOSA ADJACENT TO HUMAN COLON-CANCER

The purpose of this study was to analyze the expression of a mutant (M UT) p53 oncogene protein in the mucosal crypts adjacent to a human col on cancer. Five 1-cm mucosal segments were taken from the surgical spe cimens over a 5-cm distance from the tumor. Immunohistochemistry was p erformed using a monoclonal antibody (Ab3) to the MUT p53 and examinat ion by light microscopy. The mean % labelling index (LI) of 10 crypts/ cm segment was determined by image analysis. The LI for the entire cry pt length for the first cm segment was 33.51 +/- 4.2 and for the secon d cm segment was 29.26 +/- 5.4 (p < 0.02). Due to the unequal distribu tion 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 upp er 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 pro tein product to the crypt stem cell nucleus supports the contention th at a malignant field change exists in the transitional mucosa adjacent to a human colon cancer.