Evaluating targeted combination therapies in EGFR wild-type non-small-cell lung cancer using mass spectrometry-based proteomics

Sammanfattning: Survival for non-small cell lung cancer (NSCLC) patients has been significantly improved by epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) in patients with EGFR mutations. However, certain subpopulations of NSCLC patients with EGFR wild-type (wt) status have been shown to also respond to EGFR-TKIs. In an effort to stratify EGFRwt tumors, our group discovered in previous experiments that CDKN2A deletion could be used as a predictive biomarker for EGFR-TKI response. In this setting, we also discovered synergism between EGFR-TKIs and inhibition of the anti-apoptotic protein Bcl-xl. Evaluation of this combination treatment in a lung cancer EGFRwt cell line with CDKN2A deletion, NCI-H292, revealed that an early adaptation upregulation of cholesterol synthesis could be a possible resistance mechanism. Thereby, we hypothesized that the effectiveness of this combination treatment could be further improved by the addition of cholesterol synthesis inhibitors, i.e., statins. In the present project, we investigated the triple-drug combination of afatinib, A-1331852 and simvastatin in vitro, and the results displayed a reduced NCI-H292 viability compared to two-drug combinations or monotherapies of the three drugs. Then, by performing in-depth mass spectrometry (MS)-based molecular profiling we were able to detect patterns linked to primary resistance mechanisms of statin treatments such as feedback upregulation of the drug target 3-hydroxy3-methylglutaryl coenzyme A reductase (HMGCR). Patterns related to successful treatment such as cell cycle arrest were also detected. Taken together, these results indicate that the suggested triple combination could be used with lower concentrations of drugs involved and thereby possibly reduce unwanted side effects while at the same time being more effective.