Identification of AEG-1 and BARD1 as predictors of erlotinib outcome in EGFR-mutant non-small cell lung cancer (NSCLC) by NanoString multiple target profiling.

Abstract

7589 Background: Low BRCA1 mRNA expression prolongs progression-free survival (PFS) to erlotinib in EGFR-mutant NSCLC patients (p). In order to explore other genes potentially involved in erlotinib resistance, we used NanoString, an integrated digital technology, to examine expression levels of 48 genes in a single reaction. Several genes involved in homologous recombination repair were included in the 48-gene assessment. BARD1 couples with BRCA1 and, together with the E3 ubiquitin ligases RNF8, RNF168 and RAP80, is essential for DNA repair. AEG-1 activates the NF-kB and PI3K/Akt pathways and causes chemoresistance. Methods: CodeSets (Reporter and Capture probe sets) for 48 genes were custom-designed by NanoString Technologies. 100ng of total RNA for each sample was mixed with the reagents and hybridized at 65º overnight. Samples were processed and analyzed with the nCounter Prep Station (NanoString Technologies). Data analysis was performed adjusting the expression values according to positive control values and normalizing the data according to housekeeping genes. Results: In 55 EGFR-mutant NSCLC p treated with erlotinib, response rate was 67.6%, PFS was 16 months (m), median survival (MS) was 29 m. AEG-1 expression levels were significantly associated with PFS: low, 22 m; high, 6 m (P=0.003). BARD1 levels were also significantly associated with PFS: low, 23 m; high, 6 m (P=0.03). We generated an AEG-1/BARD1 risk model: p with high levels of both genes were considered high-risk, p with low levels of both genes were low-risk, and p with high levels of one and low levels of the other gene were intermediate-risk. PFS was not reached in the low-risk group, while it was 16 m for the intermediate-risk group and 6 m for the high-risk group (P=0.004). MS was not reached in the low-risk group, while it was 21 m for the intermediate-risk group and 31 m for the high-risk group (P=0.14). Conclusions: NanoString is a feasible technique to detect the expression of multiple genes in a single reaction, making it suitable for clinical use. Together with BARD1, AEG-1 predicts PFS in erlotinib-treated EGFR-mutant NSCLC p and could have important implications for the optimal management of NSCLC.