Lovastatin enhances the antiproliferative effect of trastuzumab in HER2 over expressing breast cancer cells

Abstract

2546 Background: Trastuzumab, a recombinant humanized anti-HER2 monoclonal antibody, has been found to have potent antiproliferative effects in HER2 overexpressing human breast tumors. Lovastatin, an HMG-CoA reductase inhibitor suppresses growth, and induces apoptosis in breast cancer cells. Both agents induce a G0/G1 arrest of cell cycle progression. The purpose of this study was to evaluate the antiproliferative effect of the novel combination of lovastatin and trastuzumab in human breast cancer cell lines. Methods: Increasing doses of lovastatin (0.16-40 μM) and trastuzumab (0.039-1 μg/ml) were tested alone and in combination. Three breast carcinoma cell lines were studied: two HER2 overexpressing lines (BT474 and SKBR3) and one cell line that expresses low levels of the receptor (MCF7). Inhibition of growth was assessed after 7 days of treatment by the MTT colorimetric assay, while apoptosis was detected using an in situ DNA Fragmentation Detection kit. Results: A dose-dependent growth inhibition was demonstrated in all three cell lines tested with lovastatin, while trastuzumab was only effective in the HER2 overexpressing cells. Trastuzumab (0.06 μg/ml) inhibited cell growth by 29.3% and 40.1%, while lovastatin (2.5 μM) caused an inhibition of 19.1% and 43% in the BT474 and SKBR3 cell lines, respectively. The combination of trastuzumab and lovastatin, at these doses, significantly inhibited growth in BT474 and SKBR3 cells by 45.4% and 68.9% (P < 0.001, oneway ANOVA) compared to either agent alone. Conclusions: Lovastatin plus trastuzumab treatment led to increased growth inhibition in HER2 positive breast cancer cell lines. Further studies in an animal model are warranted. This combination may also have important clinical therapeutic implications. No significant financial relationships to disclose.