Metallothionein expression and zinc levels in invasive ductal breast carcinoma.
Metallothioneins (MTs) and zinc are both known to promote progression of tumors 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 assess 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 and adjacent benign breast tissues. We observed overexpression of MT in breast cancer tissues and noted that zinc content in breast cancer tissues was twice that of benign breast tissues. The nuclear fraction obtained by subcellular fractionation of breast cancer tissues was found to have a higher zinc content than the plasma membrane and cytosolic fractions. Contrary to expectations, we found a significant inverse correlation of MT expression with zinc levels in breast cancer tissues, suggesting that whilst both synergistically influence growth and survival of tumor cells, they may also have divergent roles in carcinogenesis.