Abstract A263: Combination of quinacrine and erlotinib overcomes resistance to erlotinib in non-small cell lung cancer.

Abstract

Abstract The epidermal growth factor receptor (EGFR) inhibitor erlotinib is highly effective in non-small cell lung cancer (NSCLC) patients whose tumors express EGFR mutations, e.g., EGFR-L858R or EGFR exon 19 del. However, the efficacy of erlotinib is limited by either primary or secondary resistance, i.e., in patients whose tumors express wild-type EGFR (wtEGFR), or in initially sensitive patients whose tumors develop the second-site mutation EGFR-L858R/T790M or Met amplification after 10-14 months of erlotinib treatment. To improve treatment with erlotinib, we combined it with quinacrine in several erlotinib-resistant NSCLC cells. Quinacrine is a 9-aminoacridine derivative that suppresses nuclear factor-kappa B (NF-κB) by causing chromatin trapping of the FACT (facilitates chromatin transcription) complex. In A549 (wtEGFR), H1975 (EGFR-L858R/T790M), and H1993 (Met amplification) cells, the combination of erlotinib and quinacrine at 5 to 1 or 10 to 1 fixed ratios was highly synergistic, as quantified by the Chou-Talalay combination indices [ED50: 0.61 (0.42-0.81); ED75: 0.53 (0.40-0.67); ED90: 0.63 (0.54-0.71)]. Addition of quinacrine to erlotinib treatment inhibited colony formation and induced significant cell cycle arrest and apoptosis in A549 and H1975 cells. Upon quinacrine treatment, the FACT subunit SSRP1 disappeared from the soluble protein fraction, and NF-κB-dependent luciferase activity was decreased. Knockdown of SSRP1 decreased cell viability and colony formation, and sensitized the cells to erlotinib treatment. Moreover, microarray analysis of A549 and H1975 cells treated with erlotinib only, quinacrine only, or both, showed that quinacrine or combination treatment significantly affected genes involved in cell cycle progression or nucleotide metabolism, and many of these genes contain binding sites for transcription factors that regulate SSRP1-enriched genes. These data support a Phase I/II clinical trial (NCT01839955) that is just beginning, combining erlotinib and quinacrine in wtEGFR NSCLC patients after first-line chemotherapy. To assess synergistic effects in this clinical trial, we identified genes from the microarray analysis that were more significantly suppressed by combination treatment than by either single treatment. We further narrowed them down to those whose increased expression is associated with poorer survival in lung adenocarcinoma patients (HR ranges from 1.58-2.92) as potential biomarkers of drug synergy for the clinical trial. These genes, most of which are involved in various cell cycle processes, included BIRC5, DLGAP5, FOSL1, FOXM1, HIST1H2AK, HIST1H2BM, KIFC1, MKI67, PBK, PLK1, TOP2A, and ZWILCH. We conclude that the combination of quinacrine and erlotinib helps overcome erlotinib resistance in NSCLC, potentially by targeting FACT and suppressing cell cycle progression. Citation Information: Mol Cancer Ther 2013;12(11 Suppl):A263. Citation Format: Josephine Kam Tai Dermawan, Katerina Gurova, John Pink, Afshin Dowlati, Sarmishtha De, Goutham Narla, Neelesh Sharma, George Stark. Combination of quinacrine and erlotinib overcomes resistance to erlotinib in non-small cell lung cancer. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr A263.