The neu oncogene product in serum and tissue of patients with metastatic gastrointestinal carcinomas.

We report on our experience investigating the serum levels of the soluble domain of p185 and the neu protein expression in the corresponding tumour tissue in patients with advanced gastrointestinal carcinomas. The study included 32 patients who were treated with palliative chemotherapy. The serum levels of the neu protein were investigated by immunosorbent assay techniques. We used the alkaline phosphatase/anti-(alkaline phosphatase) method for investigating the corresponding tumour tissue immunohistochemically. Increased serum neu protein levels were found in 8 of 22 (36%) patients with colorectal carcinomas and in 2 patients with advanced abdominal adenocarcinoma of unknown primary. All other patients with advanced gastrointestinal cancers were serum-neu-protein-negative. All serum-neu-protein-positive patients with colorectal carcinomas showed also an elevated neu protein expression. The extent of serum neu protein expression corresponded to the clinical course and the tumour marker CA 19-9. The serum neu protein may be useful for monitoring patients with advanced colorectal carcinomas, particularly in cases of immunohistochemical neu-protein-positive primary tumours.