Abstract
BackgroundAberrant expression of the RON receptor tyrosine kinase, a member of the MET proto-oncogene family, in breast cancer and non-small cell lung cancer (NSCLC) has therapeutic implication. Here we evaluated the efficacy of a novel anti-RON antibody-drug maytansinoid conjugate Zt/g4-DM1 for treatment of breast and NSCLC xenograft tumors in mouse models and explored a treatment strategy by combination of Zt/g4-DM1 with chemotherapeutics to achieve the maximal therapeutic activity.MethodsMouse monoclonal antibody Zt/g4 (IgG1a/κ) specific to human RON was conjugated to DM1 via thioether linkage to form Zt/g4-DM1 with a drug-antibody ratio of 4:1. Several breast cancer and NSCLC cell lines, expressing different levels of RON, were used as the model. Immunofluorescence was used to determine Zt/g4-induced RON internalization. Flow cytometric analysis and cell viability assay were used to determine the effect of Zt-g4-DM1 on cell cycle and death. Mouse xenograft NSCLC models were used in vivo to determine the therapeutic efficacy of Zt/g4-DM1 alone or in combination with chemotherapeutics.ResultsIn vitro, Zt/g4 treatment of breast cancer and NSCLC cells rapidly induced cell surface RON internalization, which results in intracellular delivery of DM1 sufficient to arrest cell cycle at G2/M phase, reduce cell viability, and cause massive cell death. In mouse tumor xenograft models, Zt/g4-DM1 at 20 mg/kg in a Q12 × 2 regimen effectively blocked breast cancer and NSCLC cell- mediated tumor growth. More than 95 % inhibition of tumor growth among three tumor xenograft models tested was achieved according to the measured tumor volume. The minimal dose to balance the tumor growth and inhibition (tumoristatic concentration) was established at 2.02 mg/kg for H2228, 1.94 mg/kg for H358 cell, and 6.25 mg/kg for T-47D cell-mediated xenograft tumors.ConclusionZt/g4 is highly effective in RON-directed drug delivery for targeted inhibition of NSCLC cell-derived tumor growth in mouse xenograft models. This work provides the basis for clinical development of humanized Zt/g4-DM1 for potential cancer therapy in the future.
Highlights
Aberrant expression of the Recepteur d’Origine Nantais (RON) receptor tyrosine kinase, a member of the MET proto-oncogene family, in breast cancer and non-small cell lung cancer (NSCLC) has therapeutic implication
Induction by Zt/g4-N2′-deacetyl-N2′-(3-mercapto-1-oxopropyl) maytansine (DM1) of cell surface RON internalization To study the effect of Zt/g4 on RON internalization, we first determined the number of RON molecules expressed on cell surface using the QIFKIT® fluorescence-based quantitative method (Fig. 1a)
When antibodies were used at 5 μg IgG per ml, the RON binding profile of Zt/g4-DM1 was similar to that of free Zt/g4 among seven cell lines tested, suggesting that DM1 conjugation does not impair the binding capability of Zt/g4
Summary
Aberrant expression of the RON receptor tyrosine kinase, a member of the MET proto-oncogene family, in breast cancer and non-small cell lung cancer (NSCLC) has therapeutic implication. We evaluated the efficacy of a novel anti-RON antibody-drug maytansinoid conjugate Zt/g4-DM1 for treatment of breast and NSCLC xenograft tumors in mouse models and explored a treatment strategy by combination of Zt/g4-DM1 with chemotherapeutics to achieve the maximal therapeutic activity. Antibody-directed drug delivery in the form of antibodydrug conjugates (ADC) is a promising anti-cancer strategy [1,2,3]. Since 2012, two ADCs, ado-trastuzumab emtansine (T-DM1, Kadcyla, Roche-Genentech) and brentuximab vedotin (SGN-35, Adcetris, Seattle Genetics) have been approved for targeted therapy of breast cancer (BC) and lymphomas, respectively [4,5,6,7]. ADCs employing different antibodies targeting different cell surface proteins such as PSMA [8, 9]. ADCs represent a promising therapeutic modality for the clinical management of cancer
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