Interleukin-6 immunoreactivity in human tumors

The cytokine, interleukin-6 (IL-6), has emerged as a likely mediator of many of the systemic alterations observed in patients with cancer (fever, increased erythrocyte sedimentation rate, and alterations in plasma protein composition) and may also mediate local effects such as alteration in proliferation of tumor cells, increased tumor cell motility, and decreased intercellular adhesions between tumor cells. The distribution of IL-6 immunoreactivity in different human tumors was studied. IL-6 immunoreactivity was detected by the avidin-biotin-complex (ABC) procedure using a polyclonal rabbit antiserum raised against an E coli-derived human IL-6 (rIL-6). Preimmune rabbit serum used as a control did not yield specific staining and preadsorption of the IL-6 antiserum with rIL-6 abolished specific staining. Strong-to-moderate IL-6 immunoreactivity was observed in the neoplastic elements present in primary squamous cell carcinomas, in adenocarcinomas of mammary, colonic, ovarian, and endometrial origin, in various adenocarcinomas metastatic to lymph nodes, and in soft tissue tumors including leiomyosarcoma and neurofibrosarcoma. Weak-to-moderate IL-6 immunostaining was observed in Hodgkin's and non-Hodgkin's lymphomas. This study demonstrates that most human tumors stain positively for IL-6, adding weight to the hypothesis that IL-6 is a key cytokine that participates in the host-tumor interaction.