Multiple effects induced by herceptin® on 8701-BC breast cancer cells

Herceptin, an anti-neoplastic humanized monoclonal antibody (Herceptin®, Roche, CH), has been shown to be active against breast cancer cells over-expressing HER-2 receptor. HER-2 is a cell membrane protein that belongs to the epidermal growth factor receptors family and that results over-expressed in the 25-30% of breast cancer patients. The over-expression of HER-2 is considered a predictive and prognostic marker for breast cancer malignancy and invasiveness. On these bases, we aimed to analyze the effects caused by Herceptin treatment on 8701-BC breast cancer cells (Minafra et al., 1989). Firstly we evaluated the effects of Herceptin on the growth rate of 8701-BC cells. To this purpose, parallel cell cultures were daily treated with 0.5, 1, 1.5 and 3 µgr/ml of drug respectively, for a period of 7 days. Cell number was determined by a MTS assay. The resulting growth curves have shown a dose-dependent pharmacologic response, where cells treated with 3µgr/ml of Herceptin underwent 50% inhibition after 7 days. Therefore this concentration was selected to evaluate phenotypic effects exerted by the drug on the surviving cells. In a branch of experiments, the expression level of a group of pivotal protein classes was assayed, both at proteomic and immunological level. Concurrently, MMP-2 and MMP-9 activity in conditioned media of treated and untreated cells was assayed by zymographic assays. This investigation is justified by previous observation of our group, showing a certain degree of correlation between gelatinase expression and HER-2 overexpression in vivo (La Rocca et al., 2004). The results so far obtained, have shown that Herceptin treatment induces a strong inhibition of gelatinolytic activity and modulates the expression levels of some proteins involved in cancer progression, such as cytoskeletal proteins, cell cycle regulators, membrane receptors and associated proteins and some metabolic enzymes. We suggest that present data may contribute greatly to the knowledge of the multiple effects exerted by Herceptin on breast cancer cells.