Master-regulators driving resistance of non-small cell lung cancer cells to p53 reactivator Nutlin-3

p53 is one of the most important targets in various cancers including non-small cell lung cancer (NSCLC). Nutlin-3 reactivates p53 in cancer cells by interacting with the complex of p53 and Mdm-2, which leads to increased apoptosis of cancer cells. Nevertheless, clinical and experimental studies of Nutlin-3 have shown that in some cases cancer cells are not sensitive to this compound. We studied possible mechanisms of Nutlin-3 resistance through increased activity of pro-survival pathways appeared to be more active in the resistant cells, as compared to the cells sensitive to the treatment by this compound. Using genome-wide gene expression profiling we compared several NSCLC cell lines. Using original bioinformatics approaches we analyzed the revealed gene expression patterns in sensitive and resistant cells and identified complexes of transcription factors specifically regulating different expression of genes in the resistant cell lines. Analysis of the signal transduction network upstream from transcription factors allowed us to identify potential master-regulators responsible for maintaining this resistant state. Among them the most promising was mTOR acting in the context of the activated PI3K pathway. We validated these findings experimentally. The Nutlin-3 resistant cell lines showed the highest sensitivity to mTOR/PI3K inhibitors which lead to rapid death.