Levels of p53 antigen in the plasma of patients with adenomas and carcinomas of the colon.

Plasma levels of p53 protein were examined by an enzyme linked immunosorbent assay in 184 patients enrolled in a colonoscopy study. The mean levels among 47 individuals with normal colonoscopic examinations and no prior history of colonic neoplasia (0.12 ng/ml) and among 61 individuals with normal colonoscopic examinations and a prior history of colonic neoplasia (0.09 ng/ml) were similar. However, the mean levels among 54 individuals with newly diagnosed colonic adenomas (0.44 ng/ml) and 22 individuals with newly diagnosed colonic carcinomas (0.55 ng/ml) were statistically significantly elevated compared to the normal controls (P < 0.02). Among these tumor patients, the plasma levels tended to increase with increasing adenoma size and with increasing carcinoma stage, although these trends were not statistically significant. Defining a significant positive plasma level as any value greater than ten times background, the percentage of positive samples increased from 4% in the controls to 20% in the adenoma cases to 32% in the carcinoma cases. These results demonstrate that plasma p53 protein levels are elevated in a subgroup of individuals with colonic neoplasia.