Abstract LB-095: Type II tyrosine kinase inhibitors overcome novel acquired crizotinib-resistant MET mutations identified in gastric cancer patient
Authors: Wang Ruping , Ding Yan , Wu Xue , Wang Xiaonan , Shao Yang W. 
Published: August 2018

Abstract
Crizotinib, a highly selected type I MET and ALK inhibitor, has been used to counter MET amplification in different human malignancies including gastric cancer. However, transient response was observed in some patients with rapidly acquired resistant mutations on MET, such as D1228N and Y1230H. Cabozantinib and foretinib are type II tyrosine kinase inhibitors (TKIs) against MET, VEGFR2, RET, and other tyrosine kinases, which have been actively tested for treating metastatic cancers in multiple clinical trials. Here, we identified four novel crizotinib-resistant MET mutations, V1092L, G1163R, D1228G, and D1228Y in a MET-amplified gastric cancer patient progressed on crozotinib treatment. Drug responses and the impacts on downstream signaling pathways to type I and type II MET TKIs were characterized in Ba/F3 and 293T cells expressing the wild-type (WT) TPR-MET and the four MET mutants, respectively, as well as D1228N and Y1230H as positive controls for crizotinib-resistance. In consistence with the clinical observations, Ba/F3 cells carrying these mutants were all resistant to crizotinib with significantly increased IC50 compared to WT TPR-MET, although with different extend as V1092L and D1228G were less potent for crizotinib-resistance. These mutants showed similar responses to the two type II TKIs, but with various sensitivities among different mutants. Specifically, V1092L was super-sensitive to cabozantinib and foretinib with 21 folds and 9.5 folds decrease in IC50, respectively, compared to WT TPR-MET, while G1163R showed resistance to these two drugs. Interestingly, D1228Y and D1228N demonstrated moderate resistance to cabozantinib and foretinib, while D1228G showed similar sensitivity compared to WT TPR-MET, which may due to the different amino acid substitutions. Y1230H was also sensitive to these type II TKIs. We further examined the impacts of these TKIs on the three key downstream signaling pathways of MET, MAPK/ERK, PI3K/AKT, and JAK/STAT pathways in 293T cells transiently expressing all these mutants and WT control. Crizotinib significantly inhibited MAPK/ERK pathway activation in WT TPR-MET expressing cells, while all the mutants were resistant to its inhibition. Cabozantinib did not influence the MAPK/ERK and PI3K/AKT pathways for WT TPR-MET, but inhibited downstream STAT3 phosphorylation. In line with the drug response assay, V1092L and D1228G showed significant inhibition in the MAPK/ERK pathway, while G1163R, D1228Y and D1228N presented resistance to cabozantinib. However, none of the downstream signaling pathways were altered upon cabozantinib treatment for Y1230H. In conclusion, we explored the efficacy of type II TKIs cabozantinib and foretinib on crizotinib-resistant MET mutants identified in a gastric cancer patient, which showed various sensitivity to these drugs. Our study suggests that patient with MET V1092L, D1228G and Y1230H could potentially benefit from type II TKI treatment, but not for the G1163R and D1228Y/N mutations.
Citation Format: Ruping Wang, Yan Ding, Xue Wu, Xiaonan Wang, Yang W. Shao. Type II tyrosine kinase inhibitors overcome novel acquired crizotinib-resistant MET mutations identified in gastric cancer patient [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr LB-095.