Cross-talk between AMPK and EGFR dependent Signaling in Non-Small Cell Lung Cancer.

Lung cancer is the second most prevalent cancer in both men and women and accounts for 12% of all new cases of cancers reported worldwide1. It caused about 1.5 million deaths globally in 20102 and is the leading cause for cancer deaths3. Non small cell lung cancer (NSCLC) is a category of lung cancer in which malignant cells are formed in lung tissues. About 85% of lung cancers are NSCLC, including 40% lung adenocarcinoma (ADC)4. Like most types of cancer, lung ADCs are often perceived as a disease resulting from errant inter and intra-cellular communications manipulated by key signaling molecules. Being a highly heterogeneous malignancy, it is important to understand the etiology and pathogenesis of the disease in order to control and treat lung ADCs. As a critical, disease relevant factor aberrant activation of EGFR dependent signaling has been implicated in lung ADCs5,6. In consequence several monoclonal antibodies against EGFR have been developed. These include gefitinib (Iressa) and erlotinib (Tarceva). Their efficacy is dependent on L858R/Deletion19 mutation7. Many of these therapies induce an initial tumor regression. However, in most cases tumors become insensitive to initial therapies and evolve into more aggressive and resistant phenotypes8,9. One explanation of the decreased therapeutic benefit is the acquisition of second EGFR mutations, which make cells drug resistant10. For example, a T790M mutation occurs in more than 50% of EGFR-mutant lung cancers11. To overcome such treatment failures new targeted therapies need to be developed, possibly within a combinatorial or poly-pharmacological approach12,13. The reason is that most likely alternative cell signaling molecules are responsible for drug insensitivity and drug resistance. A recent study has shown that activation of AMPK sensitizes EGFR wildtype H1299 cells and xenografts to erlotinib treatment14. This synergistic effect was less obvious in EGFR mutated tumor models that may be due to endogenous AMPK activity and solely EGFR TKI (Tyrosine Kinase Inhibitor) sensitivity. This raises the question about possible molecular mechanisms. In this study we thus focused on the interplay between the AMPK and EGFR dependent signaling cascades in lung ADC. Accordingly, we reconstructed and subsequently validated a network of 20 genes that were associated with erlotinib response or harbor mutations in lung cancer xenograft models14. The approach for network reconstruction is based on single siRNA based knockdowns of each gene in the H1650 cell line (EGFR, delE746-A750) and subsequent gene expression profiling. Based on these data we employed Nested Effects Models (NEMs) as a statistical learning approach to unravel key elements of the interplay between AMPK and EGFR dependent signaling15. The resulting network is then validated using protein expression data in cell lines and lung ADC patient data (RNAseq plus somatic mutations) from The Cancer Genome Atlas (TCGA), demonstrating the relevance of our findings.