Metallothionein expression and zinc levels in invasive ductal breast carcinoma

Metallothioneins (MTs) and zinc are both known to promote progression of tu mors in human cancers. A close relationship exists between MT and zinc, as synthesis of the former has been reported to be induced by the latter. To a ssess the relationship between MT and zinc content in breast cancer tissues , we analysed MT expression by immunohistochemistry and tissue zinc levels by atomic absorption spectrometry (AAS) in invasive ductal breast cancers a nd adjacent benign breast tissues. We observed overexpression of MT in boas t cancer tissues and noted that zinc content in breast cancer tissues was t wice that of benign breast tissues. The nuclear fraction obtained by subcel lular fractionation of breast cancer tissues was found to have a higher zin c content than the plasma membrane and cytosolic fractions. Contrary to exp ectations, we found a significant inverse correlation of MT expression with zinc levels in breast cancer tissues, suggesting that whilst both synergis tically influence growth and survival of tumor cells, they may also have di vergent roles in carcinogenesis.