THE PS2 PROTEIN IN COLORECTAL CARCINOMAS AND METASTASES

Expression of pS2 protein in 50 primary tumors, metastases and recurre nt tumors of colorectal carcinomas has been analyzed by immunohistoche mistry. Sixty percent of the primary tumors were at least focally posi tive for the antigen. There was no correlation between pS2 expression and histologic grade of the lesions. In contrast, pS2 expression in T4 and T3 tumors was significantly higher than in T2 carcinomas. Immunor eactions in carcinomas with distant metastases (MI) were, stronger tha n in M0 cases. However, this difference did not reach statistical sign ificance. The presence of lymph node metastases did not correlate with pS2 expression. High expression of pS2 in T4 and T3 carcinomas togeth er with the finding of pronounced expression of the antigen at invasio n fronts in single cases could be interpreted as a function in tumor c ell invasion and motility. However, in metastases and recurrent tumors , pS2 expression did not differ from primary lesions (53% positive les ions). All in all, under consideration of the latter finding in partic ular and together with the randomly distributed immunopositive tumor c ells and cell clusters in the majority of cases, it is more likely tha t the expression pattern of pS2 in colorectal carcinomas is a result o f overall tumor cell heterogeneity.