From U Colorado: ALK inhibitor resistance in lung cancer

http://www.ncbi.nlm.nih.gov/pubmed/22235099

Clin Cancer Res. 2012 Jan 10. [Epub ahead of print]
Mechanisms of Resistance to Crizotinib in Patients with ALK Gene Rearranged Non-Small Cell Lung Cancer.
Doebele RC, Pilling AB, Aisner D, Kutateladze TG, Le AT, Weickhardt AJ, Kondo KL, Linderman DJ, Heasley LE, Franklin WA, Varella-Garcia M, Camidge DR.
Source
Medicine/Medical Oncology, University of Colorado Anschutz Medical Campus.

Abstract
PURPOSE:
Patients with anaplastic lymphoma kinase (ALK) gene rearrangements often manifest dramatic responses to crizotinib, a small molecule ALK inhibitor. Unfortunately, not every patient responds and acquired drug resistance inevitably develops in those that do respond. This study aimed to define molecular mechanisms of resistance to crizotinib in ALK+ non-small cell lung cancer (NSCLC) patients.

EXPERIMENTAL DESIGN:
We analyzed tissue obtained from 14 ALK+ NSCLC patients demonstrating evidence of radiologic progression while on crizotinib in order to define mechanisms of intrinsic and acquired resistance to crizotinib.

RESULTS:
Eleven patients had material evaluable for molecular analysis. Four patients (36%) developed secondary mutations in the tyrosine kinase domain of ALK. A novel mutation in the ALK kinase domain, encoding a G1269A amino acid substitution that confers resistance to crizotinib in vitro, was identified in two of these cases. Two patients, one with a resistance mutation, exhibited new onset ALK copy number gain (CNG). One patient demonstrated outgrowth of EGFR mutant NSCLC without evidence of a persistent ALK gene rearrangement. Two patients exhibited a KRAS mutation, one of which occurred without evidence of a persisting ALK gene rearrangement. One patient demonstrated the emergence of an ALK gene fusion negative tumor compared to the baseline sample, but with no identifiable alternate driver. Two patients retained ALK positivity with no identifiable resistance mechanism.

CONCLUSIONS:
Crizotinib resistance in ALK+ NSCLC occurs through somatic kinase domain mutations, ALK gene fusion CNG, and emergence of separate oncogenic drivers.