CRKL mediates EML4-ALK signaling and is a potential therapeutic target for ALK-rearranged lung adenocarcinoma
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Rong An1,*, Yisong Wang1,2,*, Donna Voeller1, Arjan Gower2, In-Kyu Kim2, Yu-Wen Zhang2, Giuseppe Giaccone1,2
1Center for Cancer Research, National Cancer Institute, Bethesda, MD 20892, USA
2Lombardi Comprehensive Cancer Center, Georgetown University, Washington DC 20007, USA
*These authors have contributed equally to this work
Giuseppe Giaccone, email: firstname.lastname@example.org
Keywords: EML4-ALK, NSCLC, CRKL, ALK
Received: February 08, 2016 Accepted: March 16, 2016 Published: April 7, 2016
Anaplastic lymphoma kinase (ALK) gene rearrangements are oncogenic drivers in a small subset of patients with non-small-cell lung cancer (NSCLC). The ALK inhibitors are highly effective in NSCLC patients harboring ALK rearrangements; however, most patients acquire resistance to the therapy following an initial response. Mechanisms of acquired resistance are complex. We used LC-MS/MS-based phosphotyrosine-peptide profiling in the EML4-ALK rearranged H3122 and H2228 cells treated with ALK inhibitors, to identify downstream effectors of ALK. We then used Western blot, siRNA experiments, cell proliferation, viability and migration assays to validate our findings. We identified CRKL as a novel downstream effector of ALK signaling. We demonstrated that CRKL tyrosine phosphorylation was repressed by pharmacological inhibition or small interfering RNA (siRNA) knockdown of ALK in the ALK-rearranged cells. More importantly, CRKL knockdown attenuated their cell proliferation, viability, and migration, but it had no effect on ALK phosphorylation and expression in these cells. Furthermore, CRKL tyrosine phosphorylation was inhibited by dasatinib (an inhibitor of ABL and SRC kinases), which in combination with the ALK inhibitor crizotinib displayed a synergistic inhibitory effect in vitro. In conclusion, our study suggests that CRKL is a key downstream effector of ALK, and combined inhibition of ALK and CRKL may represent an effective strategy for treating ALK-rearranged NSCLC patients.
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