Abstract 753: Genomic alterations of autophagy genes disrupts autophagic flux in human lung adenocarcinomas

Proceedings: AACR 106th Annual Meeting 2015; April 18-22, 2015; Philadelphia, PA Targeted therapy using EGFR tyrosine kinase inhibitor (TKI) is a standard therapy for a subset of non-small cell lung cancer (NSCLC) patients with lung adenocarcinomas (LADs) harboring EGFR kinase domain mutations; however, EGFR TKI therapy shows limited efficacy due to de novo and acquired resistance. Consequently, formulating strategies to potentiate the efficacy of EGFR TKI is of great interest. In EGFR TKI sensitive cells harboring EGFR mutation, it has been shown that EGFR inhibition induces autophagy to protect the cells from metabolic stress. Hydroxychloroquine (HQ), an inhibitor of autophagy, has been shown to potentiate EGFR TKIs in preclinical models, however, preliminary results from recent phase II clinical trials shows no added benefits to the development of resistance to erlotinib in patients with EGFR mutant NSCLC. The result suggests additional layers of mechanisms in controlling autophagy in EGFR mutated NSCLC. Furthermore, little is known about genomic alterations affecting these autophagy genes in lung cancer samples. The meta-analysis of The Cancer Genome Atlas (TCGA) database shows that essential genes for autophagic flux such as ATG5 and ATG7 tend to reduce their expression levels and/or are deleted in a significant proportion of LAD patients, suggesting a more complex scenario where the presence of these genetic alterations may lead to a structurally deficient autophagy. Besides, the detailed CNV analysis of the Cancer Cell Line Encyclopedia (CCLE) dataset suggests that a small subset of NSCLC cell lines may have lost ATG7 locus at chromosome 3. Our validation study showed that, as expected, EGFR-mutant H1650 cells exhibit an intragenic deletion at ATG7 and lack of protein expression. Moreover, functional assays of autophagic flow by western blot and confocal microscopy demonstrated that ATG7-deficient H1650 cells are not able to activate autophagy, whereas infection with lentivirus expressing ectopic ATG7 reconstituted autophagic flux and sensitivity to autophagy inhibitors including HQ. Taken together, our results suggest that genomic biomarkers based on autophagy genes could allow stratification of tumors, and selection of those candidates who could benefit from anti-autophagy therapy. Citation Format: Ines Pulido, Juan L. Pascual, Margaret Soucheray, Maria L. Rodriguez, Daniel T. Crespo, Salvador Aparisi, Joan A. Sirerol, Salvador Mena, Javier Pereda, Fatima Al-shahrour, Angel L. Ortega, Takeshi Shimamura, Julian Carretero. Genomic alterations of autophagy genes disrupts autophagic flux in human lung adenocarcinomas. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 753. doi:10.1158/1538-7445.AM2015-753