ras p21 expression in relation to DNA ploidy, S-phase fraction and prognosis in colorectal adenocarcinoma

ras p21 expression, as indicated by the monoclonal antibody ras 11, was estimated using immunohistochemistry on 69 primary colorectal adenocarcinomas. Also, DNA ploidy and S-phase fraction (SPF) were analysed with flow cytometry. Positive staining for ras 11 tended to be more common in DNA non-diploid tumours (P = 0.11), but was significantly correlated with high SPF (P = 0.038). Positive ras 11 staining, Dukes' stage, DNA ploidy and SPF were related to the recurrence-free interval of patients with Dukes' A–C tumours (P = 0.0014, P = 0.023, P = 0.035 and P = 0.040, respectively). ras 11 staining was a prognostic factor independent of both Dukes' stage and DNA ploidy (P = 0.011). The results indicate that pan ras p21 expression is associated with proliferative activity and has an independent prognostic value in colorectal adenocarcinoma.