Bioactive interleukin-6 levels in serum and ascites as a prognostic factor in patients with epithelial ovarian cancer.

Interleukin-6 (IL-6) is a multifunctional cytokine displaying diverse biologic functions that can be produced by a broad variety of normal and malignant cell types (1). In vivo, high levels of bioactive IL-6 have been detected in the ascites of patients with epithelial ovarian cancer, suggesting abundant local production of this cytokine at the tumor site (2-6). We found IL-6 levels in ascites to correlate significantly with the volume of ascites and nearly so with the size of tumor found at initial surgery (2). Notably, IL-6 levels in malignant ascites also correlated with reactive thrombocytosis, and maximum IL-6 bioactivity in ascites and highest platelet counts occurred in patients with undifferentiated ovarian adenocarcinoma or advanced disease (7). Patients who responded to chemotherapy tended to have lower ascites IL-6 levels compared with patients who failed to respond to chemotherapy (4). Berek et al. concluded that bioactive IL-6 in serum may be a useful tumor marker for ovarian cancer, because in their study it correlated with tumor burden, clinical disease status, and survival time (3). Performing a multivariate analysis, Scambia et al. (6) found serum IL-6 to have an independent prognostic value, but appeared to be less sensitive than CA-125. In conclusion, most investigators found serum and ascitic IL-6 to be of prognostic value in ovarian cancer. In the following section, the B9-bioassay for the detection of IL-6 in body fluids is described in detail.