Interleukins-6 and-11 expression in primary breast cancer and subsequent development of bone metastases

Breast cancers frequently metastasize to bone where they often cause extens ive tumor-induced osteoclast-mediated osteolysis, Interleukin-6 (IL-6) and IL-II are two cytokines exhibiting osteolytic properties through their pote nt stimulation of osteoclast formation. We investigated the expression of I L-6 and IL-IL in 99 invasive primary breast tumors by immunohistochemistry and in situ hybridization, respectively. We examined their potential as pre dictive factors for further development of bone metastases. 52/90 (57%) of tumor samples showed IL-6 cytoplasmic immunostaining, There was no signific ant association between IL-6 status and any of the classical prognostic fac tors. 15/89 (17%) of the tumor samples expressed IL-11 mRNA. A positive IL- il mRNA status was associated with a low tumor grade (P = 0.05). Tumors exp ressing IL-11 mRNA had a statistically significant (P = 0.002) higher rate of bone metastases occurrence (12/15, 80%) than IL-11 negative tumors (27/7 4, 37%). Such association was not found for IL-6. Our findings demonstrate for the first time IL-11 gene expression in some primary invasive breast tu mors and suggest the potential of this cytokine as possible biological pred ictive factor for the development of bone metastases. (C) 2001 Elsevier Sci ence Ireland Ltd. All rights reserved.