Abstract 4194: Antitumor activity of multikinase inhibitors in HER2-positive gastric cancer cells
Authors: Yoshioka Takahiro , Shien Kazuhiko , Namba Kei , Torigoe Hidejiro , Sato Hiroki , Yamamoto Hiromasa , Soh Junichi , Asano Hiroaki , Tsukuda Kazunori , Fujiwara Toshiyoshi , Toyooka Shinichi 
Published: July 2017

Background: The developments of novel anti-HER2 drugs including multikinase inhibitors have achieved advancing evolution for past several years, and the options in the treatment of HER2-positive malignant tumors have been increasing, especially in breast and lung cancers. On the other hand, regarding HER2-positive gastric cancer, trastuzumab is still the only anti-HER2 drug with the established clinical evidences. Afatinib, an irreversible human epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor, binds to the kinase domain of HER2, and is one of the hopeful candidates as novel molecularly targeted drugs for HER2-positive gastric cancer. In this study, we investigated the antitumor effect of multikinase inhibitors including afatinib in gastric cancer cell lines.

Method: We examined the relation between molecular profiles and multikinase inhibitors sensitivities in 12 gastric cancer cell lines: ECC10, GCIY, KATO-III, MKN7, MKN74, N87, NUGC3, NUGC4, OCUM-1, SH-10-TC, SNU-16, and SNU-216. In addition to multikinase inhibitors including afatinib, we also examined trastuzumab and gefitinib sensitivity in 12 cell lines. HER2 copy number alteration, HER2 mutation, and protein expression status of HER2 and its downstream pathway molecules of these cell lines were analyzed by qPCR, direct sequencing, and Western blotting, respectively. Cell proliferation was determined by a MTS assay.

Result: Afatinib was effective in GCIY, N87, SNU-216, NUGC3, and NUGC4 cells. The range of IC50 for these cell lines was 2.1 to 39.4 nM. All these cell lines except for NUGC3 were HER2 amplified. NUGC4, the most afatinib sensitive cells, had also EGFR amplification. Interestingly, among the HER2 amplified cell lines, MKN7 cells were not sensitive to afatinib, nevertheless this cell line showed the activation of HER2 pathway with the expression of phospho-HER2 by Western blotting. In addition, MKN7 cells were not sensitive to other HER2-targeted drugs trastuzumab, and reported to be insensitive to lapatinib either. On the other hand, ECC10 with HER2-L755S mutation was not sensitive to afatinib. The range of IC50 in 7 insensitive cell lines was 0.80 to more than 10 µM. Three cell lines showed moderate sensitivity to gefitinib of which IC50 ranged from 100 to 1000uM. Inhibition rate of trastuzumab was under 25% in all 12 cell lines.

Conclusion: Afatinib, a multikinase inhibitor, is highly effective to HER2 amplified gastric cancer cell lines, and may become a novel treatment option in HER2-positive gastric cancer treatment. On the other hand, afatinib is not always effective even if cancer cells have HER2 mutation or amplification. In this study, we report the detailed predictive biomarkers of sensitivity to afatinib and other several multikinase inhibitors in HER2-positive gastric cancer cells.

Citation Format: Takahiro Yoshioka, Kazuhiko Shien, Kei Namba, Hidejiro Torigoe, Hiroki Sato, Hiromasa Yamamoto, Junichi Soh, Hiroaki Asano, Kazunori Tsukuda, Toshiyoshi Fujiwara, Shinichi Toyooka. Antitumor activity of multikinase inhibitors in HER2-positive gastric cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4194. doi:10.1158/1538-7445.AM2017-4194