Absence of prolactin gene expression in colorectal cancer

Aims-Previous studies documenting hyperprolactinaemia in patients with colo rectal cancer have suggested that the tumour is the source of hormone produ ction. The aim of this study was to determine the frequency of hyperprolact inaemia in patients with colorectal cancer before, during, and after surger y, and also to determine whether prolactin is produced by these tumours. Methods-Serum prolactin concentrations were measured in 20 patients with co lorectal cancer before, during, and after surgical resection of their tumou rs. Samples taken during surgery included peripheral venous blood and blood taken from the main veins draining the tumour. To determine whether the tu mour was responsible for the production of prolactin in these patients, par affin wax embedded sections of tumour specimens were subjected to immunohis tochemistry and western blotting using a monoclonal antibody to prolactin. Results-Five patients (three women, two men) had preoperative prolactin con centrations above the normal reference range, although this increase was of clinical importance in only two. After surgical resection of their tumours , prolactin concentrations remained high in both patients. All 20 patients had greatly raised prolactin values at the time of surgery, irrespective of whether this was measured in peripheral blood or in blood taken from veins draining the tumour. All 20 colorectal cancer tissue samples, including th ose with raised preoperative and/or postoperative prolactin concentrations, were negative for prolactin staining. Frozen tissue was also available in four cases. The absence of prolactin gene expression in these four tumours was confirmed both by repeat immunohistochemistry and by western blotting. A further 50 colorectal cancer cases examined by immunohistochemistry alone were also unreactive for prolactin. Conclusions-The results of this study suggest that serum prolactin concentr ations may occasionally be raised in colorectal cancer patients, but that t he tumour is not the source of hormone production.