Expression of interleukin 6 (IL-6) correlates with oestrogen receptor in human breast carcinoma

Multifunctional cytokines play important and only partially defined roles i n mammary tumour development and progression. Normal human mammary epitheli al cells constitutively produce interleukin 6 (IL-6), IL-8 and a non-secret ed form of tumour necrosis factor. Transformation of mammary epithelial cel ls by different oncogenes is frequently associated with alterations of cyto kine/growth factor production and responsiveness. In the present study we a nalysed the expression of IL-6 in 149 cases of invasive breast carcinoma an d the data have been correlated with clinico-pathological variables includi ng tumour size, histological grade, nodal status, and oestrogen and progest erone receptors, Ki67 and p53, protein expression. Though the majority of b reast carcinomas expressed at least low levels of immunoreactive IL-6, we f ound that expression of this cytokine was inversely associated with histolo gical tumour grade (P = 0.0017), but not with tumour size and nodal status. Ki67 positivity was inversely correlated with IL-6 expression (P = 0.027). Among biological parameters analysed, a direct association was found betwe en the percentage of IL-6-positive cells and that of oestrogen (P = 0.00005 ) and progesterone (P = 0.025) receptor-positive cells. No correlation was observed between IL-6 and p53 protein expression. These data indicate that down regulation of IL-6 is associated with highly malignant mammary carcino mas. It will be of interest to evaluate whether alterations of cytokines th at are constitutively produced by mammary cells are also associated with hi gh-grade tumours.