Application of Serum ELAVL4 (HuD) Antigen Assay for Small Cell Lung Cancer Diagnosis.

The ELAVL4 (HuD) is a neuron-specific RNA-binding protein expressed in 100% of small cell lung cancer (SCLC) cells and over 50% of neuroblastoma cells. The aim of this study was to investigate the serum HuD concentration in SCLC patients and the possibility of its utilization as a biomarker of small cell lung cancer. Our study included 47 SCLC cases and 29 normal controls. Indirect competitive inhibition ELISA method was established to detect HuD antigen of serum samples. To design the ELISA system, purified antigen and real positive and negative serum samples were used, and checkerboard titration was performed. The value of current serum biomarkers (Pro-GRP, NSE, CYFRA21-1 and CEA) was obtained from a clinical laboratory. The HuD antigen concentration in the SCLCgroup was significantly higher than that in the normal group (p<0.01). The cut-off value, specificity and sensitivity were 60 ng/ml, 89.7% and 74.5%, respectively. The best linear range was 9.75~600 ng/ml. The sensitivity of the HuD-ELISA assay was much better than the current biomarkers-CEA, NSE and pro-GRP. Also,it was equal to or better than the combined use of two or three indicators. The high titres of HuD in SCLC patients and preferable consistency suggested that HuD may serve as a potential diagnostic criterium for SCLC and may serve as a marker of disease progression.