The anaplastic lymphoma kinase (ALK) is a receptor tyrosine kinase that is aberrant in a variety of malignancies. For example, activating missense mutations within full length ALK are found in a subset of neuroblastomas (Chen et al. 2008; George et al. 2008; Janoueix-Lerosey et al. 2008; Mosse et al. 2008). By contrast, ALK fusions are found in anaplastic large cell lymphoma (e.g., NPM-ALK; Morris et al. 1994), colorectal cancer (Lin et al. 2009​; Lipson et al. 2012), inflammatory myofibroblastic tumor (IMT; Lawrence et al. 2000) non-small cell lung cancer (NSCLC; Choi et al. 2008; Koivunen et al. 2008; Rikova et al. 2007; Soda et al. 2007; Takeuchi et al. 2009), and ovarian cancer (Ren et al. 2012). All ALK fusions contain the entire ALK tyrosine kinase domain. To date, those tested biologically possess oncogenic activity in vitro and in vivo (Choi et al. 2008; Morris et al. 1994; Soda et al. 2007; Takeuchi et al. 2009). ALK fusions and copy number gains have been observed in renal cell carcinoma (Debelenko et al. 2011; Sukov et al. 2012). Finally, ALK copy number and protein expression aberrations have also been observed in rhabdomyosarcoma (van Gaal et al. 2012).

The various N-terminal fusion partners promote dimerization and therefore constitutive kinase activity (for review, see Mosse, Wood, and Maris 2009). Signaling downstream of ALK fusions results in activation of cellular pathways known to be involved in cell growth and cell proliferation (Figure 1).

Figure 1. Schematic representation of ALK fusions. "X" represents the various fusion partners that have been described. Dimerization of the ALK fusion mediated by the fusion partner ("X"), results in constitutive activation of the ALK tyrosine kinase. ALK signaling results in pro-growth and anti-apoptosis.

Related Pathways

• Kinase fusions
• Receptor tyrosine kinase/growth factor signaling