Prognostic value of p53 protein and MK-1 (a tumor-associated antigen) expression in gastric carcinoma.

BACKGROUND: MK-1, the target molecule of FU-MK-1, is encoded by the GA733-2 gene, which is currently being used as a target in clinical trials for gastric, intestinal and biliary cancer treatment with monoclonal antibodies. Also of interest is p53, a protein that has been intensively investigated in relation to particular types of tumors, patterns of metastases, tumor stage, and prognosis.

METHODS: The expression of p53 protein and MK-1 antigen was investigated in specimens from 42 patients with gastric carcinoma. The specimens were stained by the avidin-biotin peroxidase technique for immunohistochemical examination.

RESULTS: MK-1 was positive in 21 (50%) of the 42 cases. MK-1 expression was more frequent in cardia tumors (71%), in large (>3 cm) tumors (60%-64%), and in specimens from patients with more than five metastatic lymph nodes (69%). p53 expression was present in 20 (48%) of the 42 cases. Of these 20 patients, 15 (52%) had tubular adenocarcinoma (TA) and 5 (38%) had signet ring cell carcinoma. p53 expression was more frequent in the tumors of male patients (55% vs 27%); in poorly differentiated TAs (60% vs 47% in well-to-moderately differentiated TAs); in smaller tumors (< or = 3 cm, 72% vs 43%-50% in larger tumors); in patients with a prominent inflammatory response (61% vs 21%; P < 0.02); and in patients with lymphatic vessel invasion (77% vs 34%; P < 0.02). However, p53 expression was less frequent in the presence of more than five metastatic lymph nodes (23% vs 60% for five or fewer nodes; P < 0.05). Most patients with p53- and MK-1-positive gastric carcinomas and those more than five metastatic lymph nodes had a poor prognosis.

CONCLUSION: The study found that the expression of both p53 and MK-1 was frequent in aggressive gastric carcinomas; however, extensive lymph node involvement (more than five nodes) was the only significant factor related to overall survival.