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ABSTRACT: Purpose
Trastuzumab emtansine (T-DM1) is the standard treatment in the current second-line therapy of human epidermal growth factor receptor 2 (HER2)-positive metastatic breast cancer. However, a useful therapy after T-DM1 resistance has not been established. In this study, we established two different HER2-positive T-DM1-resistant cancer cells and evaluated the antitumor effect of trastuzumab in combination with pertuzumab (TRAS?+?PER).Methods
Single-cell-cloned OE19 and BT-474 cells were cultured with increasing concentrations of T-DM1 to generate T-DM1-resistant OE19bTDR and BT-474bTDR cells, respectively. HER2 expression was assessed by immunohistochemistry. Multidrug resistance proteins (MDR1 and MRP1) were evaluated by real-time polymerase chain reaction and western blotting. Intracellular trafficking of T-DM1 was examined by flow cytometry and immunofluorescence staining. Efficacy of TRAS?+?PER was evaluated by cell proliferation assay, HER3 and AKT phosphorylation, caspase 3/7 activity, and antitumor activity.Results
HER2 expression of both resistant cells was equivalent to that of the parent cells. Overexpression of MDR1 and MRP1 was observed and affected the T-DM1 sensitivity in the OE19bTDR cells. Abnormal localization of T-DM1 into the lysosomes was observed in the BT-474bTDR cells. In BT-474bTDR cells, TRAS?+?PER inhibited the phosphorylation of AKT involved in HER2-HER3 signaling, and apoptosis induction and cell proliferation inhibition were significantly higher with TRAS?+?PER than with the individual drugs. TRAS?+?PER significantly suppressed tumor growth in the OE19bTDR xenograft model compared with each single agent.Conclusions
The results suggest that the TRAS?+?PER combination may be effective in T-DM1-resistant cancer cells where HER2 overexpression is maintained.
SUBMITTER: Yamashita-Kashima Y
PROVIDER: S-EPMC7561595 | biostudies-literature | 2020 Nov
REPOSITORIES: biostudies-literature
Yamashita-Kashima Yoriko Y Shu Sei S Osada Masahiro M Fujimura Takaaki T Yoshiura Shigeki S Harada Naoki N Yoshimura Yasushi Y
Cancer chemotherapy and pharmacology 20200930 5
<h4>Purpose</h4>Trastuzumab emtansine (T-DM1) is the standard treatment in the current second-line therapy of human epidermal growth factor receptor 2 (HER2)-positive metastatic breast cancer. However, a useful therapy after T-DM1 resistance has not been established. In this study, we established two different HER2-positive T-DM1-resistant cancer cells and evaluated the antitumor effect of trastuzumab in combination with pertuzumab (TRAS + PER).<h4>Methods</h4>Single-cell-cloned OE19 and BT-474 ...[more]