Purpose: The EML4-ALK fusion gene has been detected in ∼7% of Japanese non-small cell lung cancers (NSCLC). We determined the frequency of EML4-ALK in Caucasian NSCLC and in NSCLC cell lines. We also determined whether TAE684, a specific ALK kinase inhibitor, would inhibit the growth of EML4-ALK-containing cell lines in vitro and in vivo. Experimental Design: We screened 305 primary NSCLC [both U.S. (n = 138) and Korean (n = 167) patients] and 83 NSCLC cell lines using reverse transcription-PCR and by exon array analyses. We evaluated the efficacy of TAE684 against NSCLC cell lines in vitro and in vivo. Results: We detected four different variants, including two novel variants, of EML4-ALK using reverse transcription-PCR in 8 of 305 tumors (3%) and 3 of 83 (3.6%) NSCLC cell lines. All EML4-ALK-containing tumors and cell lines were adenocarcinomas. EML4-ALK was detected more frequently in NSCLC patients who were never or light (<10 pack-years) cigarette smokers compared with current/former smokers (6% versus 1%; P = 0.049). TAE684 inhibited the growth of one of three (H3122) EML4-ALK-containing cell lines in vitro and in vivo, inhibited Akt phosphorylation, and caused apoptosis. In another EML4-ALK cell line, DFCI032, TAE684 was ineffective due to coactivation of epidermal growth factor receptor and ERBB2. The combination of TAE684 and CL-387,785 (epidermal growth factor receptor/ERBB2 kinase inhibitor) inhibited growth and Akt phosphorylation and led to apoptosis in the DFCI032 cell line. Conclusions:EML4-ALK is found in the minority of NSCLC. ALK kinase inhibitors alone or in combination may nevertheless be clinically effective treatments for NSCLC patients whose tumors contain EML4-ALK.

Anaplastic lymphoma kinase (ALK) tyrosine kinase inhibitors (TKI), including crizotinib, are effective treatments in preclinical models and in cancer patients with ALK-translocated cancers. However, their efficacy will ultimately be limited by the development of acquired drug resistance. Here we report two mechanisms of ALK TKI resistance identified from a crizotinib-treated non–small cell lung cancer (NSCLC) patient and in a cell line generated from the resistant tumor (DFCI076) as well as from studying a resistant version of the ALK TKI (TAE684)–sensitive H3122 cell line. The crizotinib-resistant DFCI076 cell line harbored a unique L1152R ALK secondary mutation and was also resistant to the structurally unrelated ALK TKI TAE684. Although the DFCI076 cell line was still partially dependent on ALK for survival, it also contained concurrent coactivation of epidermal growth factor receptor (EGFR) signaling. In contrast, the TAE684-resistant (TR3) H3122 cell line did not contain an ALK secondary mutation but instead harbored coactivation of EGFR signaling. Dual inhibition of both ALK and EGFR was the most effective therapeutic strategy for the DFCI076 and H3122 TR3 cell lines. We further identified a subset (3/50; 6%) of treatment naive NSCLC patients with ALK rearrangements that also had concurrent EGFR activating mutations. Our studies identify resistance mechanisms to ALK TKIs mediated by both ALK and by a bypass signaling pathway mediated by EGFR. These mechanisms can occur independently, or in the same cancer, suggesting that the combination of both ALK and EGFR inhibitors may represent an effective therapy for these subsets of NSCLC patients. Cancer Res; 71(18); 6051–60. ©2011 AACR.