Abstract 1541: Secondary mutations in ALK and resistance to ALK kinase inhibitors

Abstract

Abstract Background: The anaplastic lymphoma kinase (ALK) inhibitor crizotinib is clinically effective in cancer patients whose tumors harbor ALK translocations. However, drug resistance will ultimately develop in most if not all patients. We studied drug resistance mechanisms using both in vitro models and analyses from tumors of patients that had developed crizotinib resistance. Methods and Results: We identified a secondary mutation in ALK, F1174L, as one cause of crizotinib resistance in a patient with an inflammatory myofibroblastic tumor (IMT) harbouring a RANBP2-ALK translocation who progressed while crizotinib therapy. When present in cis with an ALK translocation, this mutation (also detected in neuroblastomas) causes an increase in ALK phosphorylation, cell growth and downstream signaling. Furthermore, the F1174L mutation inhibits crizotinib mediated downregulation of ALK signaling and blocks apoptosis in RANBP2-ALK Ba/F3 cells. We also evaluated the impact of mutations in the ALK gatekeeper residue (L1196) and engineered all possible gatekeeper mutations resulting from a single nucleotide change into the background of EML4-ALK. Three of the mutations (L1196M, L1196Q and L1196V) in the background of EML4-ALK led to IL-3 independent growth. Furthermore the EML4-ALK L1196M mutant resulted in a greater baseline ALK phosphorylation, cell growth and downstream signaling compared to EML4-ALK alone. A chemically distinct ALK inhibitor, TAE684, or the HSP90 inhibitor 17-AAG are both effective in models harbouring the F1174L or the L1196M ALK mutations. Conclusions: We identify secondary mutations in ALK that confer crizotinib resistance. In addition, we identify therapeutic strategies, alternative ALK inhibitors or HSP90 inhibitors that may be clinically effective in patients that have developed crizotinib resistance. Understanding the mechanistic basis of drug resistance is necessary in order to develop effective clinical treatments for patients with ALK-translocated cancers. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1541. doi:10.1158/1538-7445.AM2011-1541