Ratio of autoantibodies of tumor suppressor AIMP2 and its oncogenic variant is associated with clinical outcome in lung cancer

Aminoacyl-tRNA synthetase-interacting multi-functional protein 2 (AIMP2) works as potent tumor suppressor, while its splicing variant lacking exon 2 (AIMP2-DX2) competes with AIMP2 for binding to target proteins and compromises its anti-tumor activity. Assuming that AIMP2 and its variant AIMP2-DX2 could be released out to human sera in pathological condition, we investigated the diagnostic and prognostic usefulness of autoantibodies against AIMP2 and AIMP2-DX2 by measuring their serum levels in 80 normal and lung cancer samples that were matched in age, gender and smoking status. The area under the curve of AIMP2-DX2, AIMP2, and AIMP2-DX2/AIMP2 autoantibody ratio was low (0.416, 0.579, and 0.357, respectively), suggesting limited diagnostic value. A total of 165 lung cancer patients were classified into low and high AIMP2-DX2, AIMP2, and AIMP2-DX2/AIMP2 based on the median expression of each parameter. The high AIMP2-DX2 group was older and had larger tumors (>3 cm) than the low AIMP2-DX2 group. The high AIMP2-DX2/AIMP2 group had higher CYFRA-21 levels and significantly shorter overall survival than the low AIMP2-DX2/AIMP2 group (18.6 vs. 48.9 months, P = 0.021, Log Rank Test). Taken together, autoantibodies against AIMP2-DX2 and AIMP2 are detectable in the human blood and the increased ratio of AIMP2-DX2/AIMP2 is related to poor clinical outcome of lung cancer.