Serum interleukin-6 level reflects the tumor proliferative activity in patients with colorectal carcinoma

Abstract

BACKGROUND Interleukin (IL)‐6 plays a central role as a differentiation and growth factor of tumor cells. It may be hypothesized that increased serum IL‐6 derives from the tumor tissue, and that serum IL‐6 levels consequently reflect the biologic characteristics of the tumor. The authors investigated the association between the serum levels of IL‐6 in colorectal carcinoma patients and the biologic characteristics of the tumor as well as clinicopathologic status of the patients. METHODS Serum and tissue levels of IL‐6 in 70 patients were determined using an immunoradiometric assay. Expression of IL‐6 and IL‐6 receptor were evaluated immunohistochemically. The proliferative activity of the tumor was assessed by nuclear Ki‐67 labeling index. RESULTS The concentration of serum IL‐6 in the patients was significantly higher than that in normal controls. The tissue concentration of IL‐6 in tumor tissue was significantly higher than that in normal mucosa, and was correlated strongly with the serum IL‐6 concentration. The serum IL‐6 concentration was correlated with clinicopathologic parameters, including liver metastases and tumor size, and with proliferative activity of the tumor as assessed by the Ki‐67 labeling index. In the patients with Stage I or II tumors, the preoperative serum IL‐6 concentration was reduced significantly 3 months after surgery. Immunohistochemically, tumor tissues that expressed IL‐6 immunoreactivity had a higher incidence of expression of IL‐6 receptor immunoreactivity. CONCLUSIONS Serum IL‐6 concentration reflects IL‐6 concentration in the tumor component and may reflect the proliferative activity of the tumor in patients with colorectal carcinoma. Cancer 1999;85:2526–31. © 1999 American Cancer Society.