P3.02a-006 Immune Recognition of ALK Fusion Proteins in Patients with ALK-Rearranged Non-Small Cell Lung Cancer: Topic: ALK Biomarkers

Although several tyrosine kinase inhibitors have potent antitumor activity against ALK-rearranged non-small cell lung cancers (NSCLC), resistance to these small molecules emerges through a number of mechanisms. Preclinical evidence suggests that ALK-positive NSCLCs can also be successfully targeted immunologically using vaccine-based approaches. Immunologic responses against the ALK protein have been reported in ALK-positive anaplastic large cell lymphoma, and we sought to determine whether ALK could be recognized by the immune systems of patients with ALK-positive NSCLC. Serum was collected from 32 ALK-positive and 29 ALK-negative NSCLC patients over the course of routine clinical care who had consented to an institutional review board approved translational research protocol. We developed a novel enzyme-linked immunosorbent assay (ELISA) to detect autoantibodies against the ALK cytoplasmic domain in patients with ALK-rearranged NSCLC, and the specificity of these autoantibodies was validated using Western blot analysis. Short peptides spanning the length of the ALK cytoplasmic domain were synthesized to more narrowly define the precise immunogenic peptide sequences. Among 32 ALK-positive NSCLC patients, very high ALK autoantibody titers were detected in the serum of 3 patients (9%), and ALK autoantibodies were not detected in any of the 29 patients with ALK-negative NSCLC. These autoantibodies specifically recognized only the ALK cytoplasmic domain and not the ALK extracellular domain. Epitope mapping demonstrated that the autoantibodies from each of the 3 patients with high autoantibody titers recognized distinct ALK peptide sequences within the ALK cytoplasmic domain. ALK is capable of being recognized by the immune systems in some patients with ALK-positive NSCLC. Further investigation is needed to determine whether the presence of anti-ALK antibodies impacts prognosis in NSCLC. The naturally immunogenic properties of ALK in NSCLC may be able to be exploited using therapeutic ALK vaccines in patients.