HER-2 SMASH 

Abstract Purpose Human epidermal growth factor-2 (HER-2) targeted drugs are used in only HER-2 overexpressed cancers. However, only a small portion of these cancer types are HER-2 overexpressed. In this study, we aimed to upregulate HER-2 receptors in MCF-7 breast cancer and HT-29 colon cancer cell cultures, which these cells are not HER-2 upregulated in natural status. Methods We used a 10-day non-cytotoxic lapatinib dose to upregulate HER-2 receptors. HER-2 levels of these cell lines were tested with ELISA and immunofluorescence tests before and after 10 days of lapatinib administration. After upregulation of HER-2, we administered trastuzumab, and T-DM1 to these cell lines to observe whether there is an increase in anticancer activity. We used a cell viability test (XTT) to show the cytotoxicity of trastuzumab and T-DM1. Also, we used ELISA and immunofluorescence for HER-2 pathway proteins to understand the mechanism of increased anti-cancer activity. Results We showed that administration of lapatinib for 10 days leads to overexpression of HER-2 receptors on both MCF-7 and HT-29 cells. A significant increase in the cytotoxicity of trastuzumab or T-DM1 was observed after 10 days of lapatinib administration. Conclusion We named this method the smash method, which is the volleyball term. In volleyball, the ball is raised while low and quickly hits the ground again, just like we do with the HER-2 receptor. The smash method can switch HER-2 negative or HER-2 low tumors into HER-2 overexpressed, iatrogenically. Thus, we can use her2-targeted therapies in all cancer patients instead of a small portion.