Abstract
Simple SummaryNon-small-cell lung carcinoma (NSCLC) covers for almost 85% of all lung cancers and a major contributor to the overall cancer death rate. Erlotinib is used to treat NSCLC via inhibition of epithelial growth factor receptor (EGFR) kinase activity. Despite its high efficacy, recurrence can occur in patients who become resistant to the drug. We performed DARTS LC-MS/MS with SWATH of DIA analysis and identified a novel binding protein of Erlotinib that may underlie NSCLC resistance. Our study indicated that Erlotinib binds POLA2 in addition to EGFR. This was confirmed by DARTS and CETSA results. Importantly, POLA2 expression levels in four NSCLC cell lines were positively correlated with anti-proliferative Erlotinib efficacy (Pearson correlation coefficient, R = 0.9886). These results suggest that POLA2 is a novel complementary target protein of Erlotinib, and could clinically provide validity as a surrogate marker for drug resistance in patients with NSCLC.Erlotinib inhibits epithelial growth factor receptor (EGFR) kinase activity and is used to treat non-small cell lung cancer (NSCLC). Despite its high efficacy, recurrence can occur in patients who become resistant to the drug. To address the underlying mechanism of Erlotinib resistance, we investigated additional mechanisms related to mode-of-drug-action, by multiple protein-binding interactions, besides EGFR by using drug affinity responsive target stability (DARTS) and liquid chromatography-mass spectrometry (LC-MS/MS) methods with non-labeled Erlotinib. DNA polymerase alpha subunit B (POLA2) was identified as a new Erlotinib binding protein that was validated by the DARTS platform, complemented with cellular thermal shift assays. Genetic knock-down of POLA2 promoted the anti-proliferative effect of the drug in the Erlotinib-resistant cell line H1299 with high POLA2 expression, whereas the overexpression of POLA2 restored anti-proliferative effects in the Erlotinib-sensitive cell line HCC827 with low POLA2 expression. Importantly, POLA2 expression levels in four NSCLC cell lines were positively correlated with anti-proliferative Erlotinib efficacy (Pearson correlation coefficient, R = 0.9886). These results suggest that POLA2 is a novel complementary target protein of Erlotinib, and could clinically provide validity as a surrogate marker for drug resistance in patients with NSCLC.
Highlights
Non-small-cell lung carcinoma (NSCLC) accounts for almost 85% of all lung cancers and is a major contributor to the overall cancer death rate [1]
The results showed that patients with mutant epithelial growth factor receptor (EGFR) who were treated with receptor tyrosine kinase inhibitor (RTKi) were significantly better off than those treated with traditional chemotherapy [11]
To explore the underlying mechanisms to protein-Erlotinib affinity interactions that builds into a functional drug resistance, we hypothesized the involvement of complementary drug interactions to key regulating NSCLC-proteins, inter-related to the action of EGFR
Summary
Non-small-cell lung carcinoma (NSCLC) accounts for almost 85% of all lung cancers and is a major contributor to the overall cancer death rate [1]. Lung cancer of the non-small cell histotype is treated with surgical exploration and resection with mediastinal lymph node dissection or systematic lymph node sampling. In case an established histologic subtype and adequate tissue for laboratory testing is present, molecular testing for EGFR, ALK, ROS1, NTRK, and BRAF should be conducted as part of broad molecular profiling [2]. This can be extended to PD-L1 testing as well. The resulting molecular profile drives decision making in thoracic oncology of lung cancer [3]
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