Signaling through receptor tyrosine kinases (RTKs) regulates and fine-tunes many processes including cell growth, proliferation, differentiation, and apoptosis. The improper activation of RTKs is involved in the pathogenesis, growth, and metastasis of many cancers. The receptor tyrosine kinase ALK (Anaplastic Lymphoma Kinase) is a member of the insulin receptor superfamily that was initially identified from the t(2;5)(p23;q35) translocation in anaplastic large cell lymphoma (ALCL) (Fischer, P., et al. Blood, 72: 234-240. (1988)). The protein product of this translocation is ALK fused to nucleophosmin (NPM) (Morris et al., 1994). When fused to ALK, the dimerization domain of NPM results in constitutive dimerization and activation of ALK (reviewed in Chiarle, R., Nature reviews, 8:11-23 (2008)). Once activated, ALK recruits several adaptor proteins and stimulates multiple signaling pathways known to mediate tumor cell growth and survival including STAT3, PLC-γ, RAS-ERK1,2, and PI3K-AKT (Bai, R. Y., et al. Molecular and cellular biology 18: 6951-6961 (1998); Bai, R. Y., et al. Blood 96:4319-4327 (2000); Chiarle, R., et al. Nature medicine 11:623-629 (2005); Pulford, K., et al. Journal of cellular physiology 199:330-358 (2004)). The dysregulation of ALK is highly oncogenic, as it is sufficient to induce cell transformation in a several immortalized cell lines (Bischof, D., et al. Molecular and cellular biology 17:2312-2325 (1997); Fujimoto, J., et al. Proceedings of the National Academy of Sciences of the United States of America 93: 4181-4186 (1996)) and to form tumors in animal models (Chiarle, R., et al. Blood 101: 1919-1927 (2003); Kuefer, M. U., et al. Blood 90: 2901-2910 (1997)). Moreover, NPM-ALK drives tumor formation, proliferation and survival in ALCL (reviewed in (Duyster, J., et al. Oncogene 20: 5623-5637 (2001)).
More recently, ALK translocations have been detected in ˜5% of non-small cell lung cancers (NSCLC). Similar to ALK translocations in ALCL, the fusion proteins in NSCLC display constitutive ALK activity and drive tumor growth and survival (Soda et al., Nature 448: 561-566 (2007); Soda et al., Proceedings of the National Academy of Sciences of the United States of America 105: 19893-19897 (2008)). NSCLC tumors harboring ALK translocations are mutually exclusive from K-Ras or EGFR aberrations and predominantly occur in younger patients that are non-smokers (Rodig et al., Clin Cancer Res 15: 5216-5223 (2009); Shaw et al., J Clin Oncol 27: 4247-4253 (2009); Wong et al., Cancer 115: 1723-1733 (2009)). In addition to chromosomal rearrangements, activating point mutations and amplifications have been reported in a subset of sporadic and familial neuroblastomas, further expanding the spectrum of tumors dependent on ALK activity (Chen et al., Nature 455: 971-974 (2008); George et al., Nature 455: 975-978 (2008); Janoueix-Lerosey et al., Nature 455: 967-970 (2008); Mosse et al., Nature 455: 930-935 (2008)). Neuroblastomas with ALK genetic aberrations also are dependent on ALK for proliferation and survival, and cells expressing ALK containing activating mutations form tumors in animal models.
Inhibitors of RTKs have the potential to cause lethality in cancerous cells that are reliant on deregulated RTK activity while sparing normal tissues. Thus, small molecule inhibitors of ALK would be beneficial for therapeutic intervention in ALCL, NSCLC, neuroblastoma, and other cancers that are dependent on ALK for growth and survival.