Metallothionein 1F mRNA expression correlates with histological grade in breast carcinoma

Immunohistochemical expression of metallothioneins (MTs), a group of intrac ellular metal-binding proteins, is well documented in breast cancer. Howeve r, there is a paucity of information on the expression of the different MT isoforms in breast cancer tissues. The dichotomous association of MT overex pression with tumour types and progression led us to examine the role of th e MT-1F mRNA isoform in breast cancer. We evaluated MT expression in 48 pri mary invasive ductal breast cancer tissues by immunohistochemistry, and the corresponding MT-1F mRNA expression via a semi-quantitative reverse transc ription-polymerase chain reaction (RT-PCR) assay. The specificity of the RT -PCR products was confirmed by direct cycle sequencing and restriction enzy me digestion. Immunohistochemical analysis of MT revealed a significantly h igher MT expression in histological grade 3 tumours as compared to grade 1 and 2 tumours (p = 0.021). Similarly, MT-1F mRNA expression was found to be significantly higher in grade 3 tumours (p < 0.001). The results suggest t hat the MT-1F isoform influences histological differentiation in invasive d uctal breast cancer. The converse is also true in that the histological gra de may determine the level of MT-1F expression in breast cancer.