Metallothionein 1E mRNA is highly expressed in oestrogen receptor-negativehuman invasive ductal breast cancer

Metallothioneins (MTs), a group of ubiquitous metalloproteins, comprise iso forms encoded by ten functional genes in humans. Different MT isoforms poss ibly play different functional roles during development or under Various ph ysiological conditions. The MT-1E isoform mRNA has been recently shown to b e differentially expressed in oestrogen receptor (OR)-positive and OR-negat ive breast cancer cell lines. In this study, we evaluated MT-IE mRNA expres sion via semi-quantitative RT-PCR in 51 primary invasive ductal breast canc er tissues, concurrently with OR-positive and progesterone receptor (PR)-po sitive MCF7 cells, OR-negative and PR-negative MDA-MB-231 cells and PR-tran sfected MDA-MB-231 breast cancer cells (ABC28). We demonstrated significant ly higher MT-1E mRNA expression in OR-negative compared with OR-positive br east cancer tissues (P = 0.026). MCF7 cells lacked MT-1E mRNA expression, w hile both OR- and PR-negative MDA-MD-231 cells exhibited a high level of MT -1E mRNA expression. The level of MT-IE mRNA expression in progesterone-tre ated and -untreated ABC28 cells remained similar as the parental cell line MDA-MB-231-C2 cells. The results suggest that MT-1E may have specific and f unctional roles in OR-negative invasive ductal breast cancers, possibly med iated via effector genes downstream of the oestrogen receptor, but not thro ugh the PR pathway. (C) 2000 Cancer Research Campaign.