Abstract 2941: Increased expression of ABCB1/MDR1 could be associated with alectinib resistance in ALK-rearranged lung cancer cells

Abstract

Abstract Alectinib, a second-generation anaplastic lymphoma kinase (ALK) inhibitor, has shown promising activity in ALK-rearranged non-small cell lung cancer (NSCLC). The mechanisms of drug resistance to alectinib have been still unclear. To explore whether overexpression of ATP-binding cassette (ABC) transporters might provide a potential mechanism of alectinib resistance in lung cancer, we established alectinib-resistant cell lines from NCI-H2228 and primary ALK-rearranged cells and evaluated the expression of ABC transporters. We established ALK-rearranged NSCLC cell lines (KTOR 1, 2, and 3) from tumor cells in pleural effusion obtained from 3 patients with alectinib naïve ALK-rearranged NSCLC. In the 2 of 3 patients, tumor cells in pleural effusion were also obtained when disease progression was observed during alectinib treatment (KTOR1-RE and KTOR2-RE). Expression profiling of ABC transporters using quantitative real-time polymerase chain reaction (qRT-PCR) revealed that the expression of ABCB1 was significantly increased in KTOR1-RE and KTOR2-RE compared with the parental cells (4.6 and 10.8 folds), but not other ABC transporters. Then, alectinib-resistant NCI-H2228 cell lines (H2228-AR) were established by exposing the parental cells to stepwise-increasing alectinib up to 5μM for 10 months. We found that the ABCB1/MDR1 expression in H2228-AR cells were significantly increased (2.09-16.6 folds) compared with the parental cells using qRT-PCR and immunoblotting. Then, we examined the alternation of alectinib cytotoxicity by inhibition of ABCB1. Knockdown of ABCB1 expression using small interfering RNA and inhibition of ABCB1 by verapamil enhanced alectinib cytotoxicity in H2228-AR cells. Next, the levels of ABCB1 expression after short-term alectinib exposure were examined in NCI-H2228 and the three alectinib naïve ALK-rearranged NSCLC primary cell lines (KTOR 1, 2, and 3). In all the four ALK-rearranged cell lines, exposure to 100 nM alectinib for 72 hours induced increased expression of ABCB1 compared with control medium. These data suggested that increased expression of ABCB1/MDR1 might be, in part, responsible acquired resistance and sensitivity to alectinib in ALK-rearranged NSCLC cells. Citation Format: Takahiro Tsuji, Hiroaki Ozasa, Yuichi Sakamori, Takashi Nomizo, Yoshitaka Yagi, Hiroki Nagai, Young Hak Kim, Michiaki Mishima. Increased expression of ABCB1/MDR1 could be associated with alectinib resistance in ALK-rearranged lung cancer cells. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2941.