Combination efficacy of pertuzumab and trastuzumab for trastuzumab emtansine-resistant cells exhibiting attenuated lysosomal trafficking or efflux pumps upregulation

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.

Pertuzumab retreatment for HER2‐positive advanced breast cancer: A randomized, open‐label phase III study (PRECIOUS)

“…In in vitro and in vivo studies, pertuzumab and trastuzumab significantly suppressed tumor growth activity and tumor growth of T‐DM1‐resistant HER2‐positive cell lines compared to single treatment with trastuzumab or pertuzumab. 31 The present open‐label randomized controlled trial provided results that support this basic research.…”

“…Although no comparative studies of T‐DM1 versus pertuzumab and T‐DM1 in second‐ or later‐line treatment have been carried out, T‐DM1 monotherapy is still the most recommended second‐line treatment. In in vitro and in vivo studies, pertuzumab and trastuzumab significantly suppressed tumor growth activity and tumor growth of T‐DM1‐resistant HER2‐positive cell lines compared to single treatment with trastuzumab or pertuzumab 31 . The present open‐label randomized controlled trial provided results that support this basic research.…”

YES1 as a Therapeutic Target for HER2-Positive Breast Cancer after Trastuzumab and Trastuzumab-Emtansine (T-DM1) Resistance Development

“…The protein expression levels of epithelial-mesenchymal transition markers such as E-cadherin and N-cadherin, cancer stem cell markers such as vimentin and ALDH1 and ATP-binding cassette (ABC) transporters such as ABCB1 and ABCG2, which are known to be involved in mechanisms of resistance development to cytotoxic agents, were not changed (data not shown). Previous reports [ 5 , 6 ] noted that the mechanisms of impairment of DM-1-mediated cytotoxicity include increased expressions of drug efflux transporters [ 26 , 27 , 28 , 29 ], mutations in tubulin [ 30 ], escape from mitotic catastrophe through reduced induction of cyclin B1 and increased expression of polo-like kinase 1 [ 31 , 32 , 33 ]. Further studies are needed to elucidate the mechanisms underlying the reduced sensitivity to DM1 in our resistant cell line.…”

Antibody-drug conjugates: the clinical development in gastric cancer

“…While ADCs are currently offering significant benefits to gastric cancer patients, issues related to resistance mechanisms for each component are surfacing. These currently include downregulation of cell surface antigens like HER2, drug efflux proteins, impaired endocytosis, defects in internalization pathways such as AKT signalling, overexpression of transporters such as V-ATP binding cassettes, and lysosomal degradation ( 24 – 26 ).…”