[Immunohistochemical study of ras p21 expression in human gastric cancers and benign lesions]

Expression of ras p21 in human gastric cancers, benign lesions (i.e. dysplasia, intestinal metaplasia and hyperplastic polyps) and normal tissues was immunohistochemically evaluated by the avidin-biotin complex (ABC) immunoperoxidase method with anti-ras p21 monoclonal antibody(rp-28). Positive p21-immunoreactivity was shown in 23(77%) of 30 gastric cancers, in 13(48%) of 27 benign lesions and in 10(22%) of 46 normal mucosa. Among them, strong staining was demonstrated only in 11(37%) of 30 gastric cancers, but not in benign lesions and normal tissues. Cases showing more than 20% positive cell ratio were observed in 22(73%) of gastric cancers, in 11(41%) of benign lesions and 6(13%) of normal mucosa. Furthermore, there was clear difference in intracellular distribution of ras p21 between in gastric cancers and in benign lesions or normal tissues. Plasma membrane and cytoplasm of malignant cells showed positive immunoreactivity in some gastric cancers. On the other hand, ras p21 was observed in cytoplasm of positive cells in benign tissues. The ABC method with this antibody could be useful for clinical differential diagnosis between gastric cancers and benign lesions by investigating three factors: staining intensity, positive cell ratio and intracellular distribution.