T790M-mutant Non-small Cell Lung Cancer Research Articles

Complex EGFR mutations with secondary T790M mutation confer shorter osimertinib progression-free survival and overall survival in advanced non-small cell lung cancer

ObjectivesOsimertinib is active against epidermal growth factor receptor (EGFR) T790M-mutated non-small cell lung cancer (NSCLC). However, its efficacy against complex EGFR mutations with T790M has not been evaluated. Materials and methodsIn order to detect complex EGFR mutations, we consecutively sequenced cancer tissues by RNA reverse transcription polymerase chain reaction. Patients with advanced NSCLC with activating EGFR mutation and secondary T790M who received osimertinib were enrolled. Patients’ clinicopathologic characteristics, prior treatment details, and osimertinib treatment outcomes were analyzed. ResultsTotally, 165 sequenced patients were analyzed. Eleven (7%) of them had complex EGFR mutations with T790M. The osimertinib response rate was 27%. They had a shorter progression-free survival (PFS) (median, 2.9 and 9.7 months, p < 0.001) and overall survival (OS) (median, 17.8 and 31.0 months, p = 0.01) than patients with a single EGFR mutation with T790M. After osimertinib failure, seven patients received rebiopsy with molecular analysis. Four lost the T790M, two transformed to small cell and one acquired C797S. Moreover, taking the median as the demarcation, patients received shorter prior EGFR tyrosine kinase inhibitor (TKI) treatment duration had a shorter osimertinib PFS (median, 7.3 and 13.8 months, p < 0.001) and OS (median, 21.5 and 36.7 months, p = 0.003). Multivariate Cox regression analysis confirmed complex EGFR mutations and prior EGFR TKI treatment duration were independent factors for osimertinib PFS and OS. ConclusionsComplex EGFR mutations and shorter prior EGFR TKI treatment duration may confer shorter osimertinib PFS and OS in advanced NSCLC with secondary T790M mutation.

Applied electric fields suppress osimertinib-induced cytotoxicity via inhibiting FOXO3a nuclear translocation through AKT activation.

Osimertinib is a third-generation epidermal growth factor receptor tyrosine kinase inhibitor against T790M-mutant non-small cell lung cancer (NSCLC). Acquired resistance to osimertinib is a growing clinical challenge that is not fully understood. Endogenous electric fields (EFs), components of the tumor microenvironment, are associated with cancer cell migration and proliferation. However, the impact of EFs on drug efficiency has not been studied. In this study, we observed that EFs counteracted the effects of osimertinib. EFs of 100 mV/mm suppressed osimertinib-induced cell death and promoted cell proliferation. Transcriptional analysis revealed that the expression pattern induced by osimertinib was altered by EFs stimulation. KEGG analysis showed that differential expression genes were mostly enriched in PI3K-AKT pathway. Then, we found that osimertinib inhibited AKT phosphorylation, while EFs stimulation resulted in significant activation of AKT, which could override the effects generated by osimertinib. Importantly, pharmacological inhibition of PI3K/AKT by LY294002 diminished EF-induced activation of AKT and restored the cytotoxicity of osimertinib suppressed by EFs, which proved that AKT activation was essential for EFs to attenuate the efficacy of osimertinib. Furthermore, activation of AKT by EFs led to phosphorylation of forkhead box O3a (FOXO3a), and reduction in nuclear translocation of FOXO3a induced by osimertinib, resulting in decreased expression of Bim and attenuated cytotoxicity of osimertinib. Taken together, we demonstrated that EFs suppressed the antitumor activity of osimertinib through AKT/FOXO3a/Bim pathway, and combination of PI3K/AKT inhibitor with osimertinib counteracted the effects of EFs. Our findings provided preliminary data for therapeutic strategies to enhance osimertinib efficacy in NSCLC patients.

P2.13-13 Real-World Study of Osimertinib in EGFR T790M-Mutated Non-Small Cell Lung Cancer (NSCLC): ASTRIS Canadian Cohort Analysis

ASTRIS is an open-label, single-arm, multinational, real world study of osimertinib for patients with advanced/metastatic epidermal growth factor receptor-mutated (EGFRm) T790M-positive non-small cell lung cancer (NSCLC) who previously received therapy with an EGFR tyrosine kinase inhibitor (EGFR-TKI) (NCT02474355). Data cut-off (DCO) for the second interim analysis was 20 October 2017, with 3014 patients enrolled (full analysis set), including 99 patients in Canada. Adult patients with locally advanced/metastatic EGFRm NSCLC, not amenable to curative surgery/radiotherapy, with confirmation of T790M and prior EGFR-TKI therapy were enrolled. Patients were included with World Health Organization performance status of 0 to 2, as well as those with asymptomatic stable central nervous system (CNS) metastases. Patients received osimertinib 80 mg once daily until loss of clinical benefit. The primary efficacy outcome was overall survival (OS), with secondary outcomes of investigator-assessed response rate (RR), progression-free survival (PFS), and time to treatment discontinuation (TTD). From study start (14 January 2016) to DCO (20 October 2017), 99 patients were enrolled at 12 Canadian centres. Median age was 64 years (30-89 years). Patients were 68% female, 57% Asian, and had ECOG 0/1/2 of 22%/65%/13%. Twenty-five patients had CNS metastases at screening. Gefitinib was the most commonly used previous EGFR-TKI (gefitinib, erlotinib and afatinib were 80%, 14%, and 14%, respectively). Thirty-nine percent had previous chemotherapy; 6% previous immunotherapy; 46% previous radiotherapy. All patients had T790M: 75% tissue, 7% blood and 18% cytology. Biomarker testing methods varied, with the majority (61%) identified by Entrogen EGFR kit. At DCO, 45 patients had discontinued treatment. OS data were immature. Median PFS was 11.0 months (95% CI, 8.9-13.3). Median TTD was 14.9 months (95% CI, 11.2-not calculated). RR was 67.0% (95% CI, 56.7-76.2); sub-analyses showed RR of 69.9% (58.0-80.1), 66.7% (22.3, 95.7) and 55.6% (30.8, 78.5) for patients with T790M by tissue, blood and cytology, respectively. Serious adverse events (AEs) were reported for 18% of patients. AEs leading to dose modifications and discontinuations were reported for 12% and 5% of patients, respectively. The Canadian results from this real world study of osimertinib in advanced/metastatic EGFRm T790M-positive NSCLC, which includes heavily pretreated patients and various approaches to biomarker testing, were comparable to outcomes reported in the phase III study AURA3 (NCT02151981). These findings provide further support for osimertinib as standard of care for EGFRm T790M-positive NSCLC.

MA15.07 Different Responses to Osimertinib in Primary and Acquired EGFR T790M-Mutant NSCLC Patients

Primary EGFR T790M could be occasionally identified by routine molecular testing in tyrosine kinase inhibitor TKI-naive non-small cell lung cancer (NSCLC) patients. This study was aimed to compare clinical characteristics of primary and acquired T790M mutations and their responses to Osimertinib in NSCLC patients. We collected clinical characteristics of patients diagnosed with epidermal growth factor receptor (EGFR) mutation from 2012 to 2017 in Shanghai Chest Hospital. For patients with primary and acquired T790M mutations, the responses to Osimertinib were analyzed. Primary T790M was identified in 1.03% (61/5900) of TKI-naive patients. Acquired T790M was detected in 45.50% (96/211) of TKI-treated patients. T790M always coexisted with sensitizing EGFR mutations. Primary T790M was always coexisted with 21L858R (45/61) whereas acquired T790M was coexisted with 19del (61/96). Among them, 18 patients with primary T790M mutation acquired Osimertinib and 75 patients with acquired T790M mutation received Osimertinib. The median progression-free survival (mPFS) of Osimertinib in primary T790M group was greatly longer than that in acquired T790M group (18.0 months:95% CI:15.0-21.0 VS 10.0months:95% CI:8.3-11.7, P=0.016). The DCR of both groups were 89.3% and 100%. In primary T790M group, the mPFS of concomitant occurrence of 20 T790M and 21 L858R or 19del were 15.7m and 24.0 m, respectively. In acquired T790M group, the mPFS of concomitant occurrence of 20 T790M and 21 L858R or 19del were 11.0m and 10.0m, respectively. Primary and acquired T790M-mutation patients showed different molecular characteristics. Both of them may respond to Osimertinib. However, primary T790M patients showed greater survival benefits from Osimertinib than acquired T790M patients.

AZD9291 promotes autophagy and inhibits PI3K/Akt pathway in NSCLC cancer cells.

AZD9291, a third-generation epidermal growth factor receptor tyrosine kinase inhibitor (EGFR-TKI), is highly selective against EGFR T790M-mutant non-small cell lung cancer (NSCLC). On investigating the growth inhibitory effects of AZD9291 on NSCLC and the underlying mechanism, we found that AZD9291 can trigger autophagy-mediated cell death in both A549 and H1975 cells by increasing the expression of phosphatidylethanolamine-modified microtubule-associated protein light-chain 3 (LC3) and decreasing the expression of p62. In the presence of the autophagy inhibitor chloroquine, the AZD9291-induced increase in LC3 level was further augmented. AZD9291 decreased the levels of phosphoinositide-3 kinase (PI3K), protein kinase B (Akt), and phosphorylated Akt. AZD9291-induced cell death was enhanced by Akt knockdown, and the levels of both EGFR and phosphorylated EGFR were decreased by AZD9291. AZD9291 was also found to significantly suppress the tumor growth in H1975 xenograft nude mice. Thus, AZD9291 was found to induce autophagy, decrease in EGFR levels, and show a strong inhibitory effect on NSCLC both in vitro and in vivo. Furthermore, the PI3K/Akt signaling pathway was found to play a critical role in AZD9291-induced cell death.

Differential MicroRNA Expression between EGFR T790M and L858R Mutated Lung Cancer

BackgroundMicroRNAs (miRNAs) are short, non-coding RNAs that mediate post-transcriptional gene regulation. They are commonly deregulated in human malignancies, including non-small cell lung cancer (NSCLC). The aim of this study is to investigate miRNA expression in T790M-mutated NSCLC resistant to epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors.MethodsSix cases of resected NSCLC harboring the T790M mutation were examined. We performed miRNA time polymerase chain reaction (PCR) array profiling using EGFR T790M-mutated NSCLC and L858R-mutated NSCLC. Once identified, miRNAs that were differentially expressed between the two groups were validated by quantitative real-time polymerase chain reaction (qRT-PCR).ResultsmiRNA PCR array profiling revealed three up-regulated miRNAs whose expression levels were altered 4.0-fold or more in the EGFR T790M mutation group than in the L858R group: miR-1 (fold change, 4.384), miR-196a (fold change, 4.138), and miR-124 (fold change, 4.132). The three differentially expressed miRNAs were validated by qRT-PCR, and they were found to be overexpressed in the T790M group relative to L858R group. In particular, expression levels of miR-1 and miR-124 were significantly higher in the T790M group (p-value of miR-1 = .004, miR-124 = .007, miR-196a = .096).ConclusionsMiR-1, miR-124, and miR-196a are overexpressed in EGFR T790M mutated NSCLC.

Primary and acquired EGFR T790M-mutant NSCLC patients identified by routine mutation testing show different characteristics but may both respond to osimertinib treatment

Primary EGFR T790M mutation is occasionally identified by routine mutation testing in tyrosine kinase inhibitor (TKI)-naive patients with non-small cell lung cancer (NSCLC). We herein aimed to compare the characteristics of primary and acquired T790M mutations in NSCLC patients, and their response to osimertinib. Using amplification refractory mutation system (ARMS) detection, primary T790M was identified in 0.5% (46/8723) of TKI-naive patients, whereas acquired T790M was detected in 49.7% (71/143) of TKI-relapsed patients. T790M always coexisted with a sensitizing EGFR mutation. Primary T790M more commonly coexisted with L858R, whereas acquired T790M was more likely to coexist with exon 19 deletions. Moreover, next-generation sequencing (NGS) showed that concomitant sensitizing EGFR and primary T790M mutant allele frequencies (MAFs) were highly concordant, but acquired T790M MAFs were significantly lower than the sensitizing EGFR MAFs. Sixteen acquired T790M-mutant patients received osimertinib. The median progression-free survival (PFS) was 8.1 months. Four primary T790M-mutant patients received osimertinib and the median PFS was 8.0 months. Together, our study demonstrates that primary and acquired T790M-mutant patients show distinct differences in some clinical and molecular characteristics, but may both respond to osimertinib treatment.

Combination of S-1 and gefitinib increases the sensitivity to radiotherapy in lung cancer cells.

To investigate the potential radiosensitization of S-1 and gefitinib in human non-small cell lung cancer (NSCLC) in vitro and in vivo. The impact of radiation, 5-fluorouracil (5-Fu), and gefitinib on the proliferation and apoptosis of human NSCLC A549, H1299, H1975, and HCC827 cells was examined by MTT and flow cytometry. The effect of radiation, 5-Fu, and gefitinib on the clonogenicity of H1975 and HCC827 cells was determined by colony formation assay. The effect of radiation, 5-fluorouracil (5-Fu), and gefitinib on the EGFR, AKT, and ERK1/2 activation in H1975 cells was determined by Western blot. The therapeutic efficacy of radiation, S-1, and gefitinib in the growth of implanted H1975 tumors and the AKT activation in the tumors were examined in vivo and immunohistochemistry, respectively. Combination of radiation, 5-Fu, and gefitinib significantly inhibited the proliferation of H1975 cells and triggered their apoptosis, but not other NSCLC cells tested. The combination therapy significantly mitigated the clonogenicity and attenuated the activation of EGFR and AKT signaling in H1975 cells. Furthermore, combination of S-1, gefitinib, and radiation significantly inhibited the growth of implanted H1975 tumors in mice and remarkably reduced the AKT phosphorylation in the tumors. Our data indicated that combination of S-1 and gefitinib significantly increased radiosensitivity of H1975 cells. The triple combination therapies may benefit patients with the EGFR T790M mutant NSCLC.

Usefulness of Bronchoscopic Rebiopsy of Non-Small Cell Lung Cancer with Acquired Resistance to Epidermal Growth Factor Receptor-Tyrosine Kinase Inhibitor.

Background: Approximately 50% of non-small cell lung cancer (NSCLC) patients with acquired resistance to EGFR-TKI harbor the EGFR mutation T790M. The recent development and wide use of third-generation EGFR-TKIs targeting T790M-mutant NSCLCs have increased the importance of rebiopsy after EGFR-TKI failure. We aimed to investigate the advantages of flexible bronchoscopy as a rebiopsy method and the prevalence of and factors affecting the T790M mutation after EGFR-TKI failure.Methods: We investigated 139 patients who had undergone bronchoscopic rebiopsy and endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA) between Sep 2014 and Jul 2016.Results: Among the 139 patients, bronchoscopic rebiopsy yielded successful pathological diagnoses in 102 (73.4%). Among them, 41 patients with EGFR-mutant lung adenocarcinoma and EGFR-TKI progression were selected for an investigation of T790M mutation prevalence at rebiopsy. The initial EGFR mutations were exon 19 del (56.1%), L858R or L861Q (34.1%), and others (9.8%). The most common rebiopsy method was transbronchial lung biopsy (41.5%), followed by EBUS-TBNA (26.8%) and endobronchial biopsy (19.5%). The median interval to T790M emergence was the longest among cases with exon 19 deletion (14.1 months), followed by exon 21 L858R or L861Q (11.3 months) and other rare EGFR mutations (2.9 months). The T790M mutation was identified in 18 (43.9%) patients, and exon 19 del was the most significant factor affecting T790M mutation development (hazard ratio: 6.875, P = 0.014).Conclusions: Bronchoscopy was more useful than other rebiopsy approaches. The T790M emergence rate was highest in cases with exon 19 deletion, likely as a consequence of long-term EGFR-TKI exposure.

Abstract 1009: Comprehensive ctDNA sequencing reveals mechanisms of resistance to rociletinib in EGFR T790M-mutated NSCLC

Abstract Background: First and second-generation EGFR tyrosine kinase inhibitors (TKIs) have benefited patients with EGFR-mutated non-small cell lung cancer (NSCLC), but resistance invariably develops after a median of 9-16 months. In ~60% of patients, resistance is mediated by a second mutation in EGFR, namely T790M. Hence, third-generation EGFR TKIs such as osimertinib and rociletinib were developed to target both activating EGFR mutations as well as T790M. Unfortunately, patients also develop resistance to these therapies through mechanisms that have not yet been thoroughly explored. Since repeat tissue biopsies pose potential complications from invasive procedures, circulating tumor DNA (ctDNA) testing is increasingly used in the clinical setting to identify potentially targetable mechanisms of resistance. Methods: Matched pre-treatment and progression plasma from 57 patients with EGFR-mutated NSCLC treated with rociletinib were profiled using a 70-gene ctDNA targeted next-generation sequencing panel (Guardant360) that detects somatic single nucleotide variants, short insertions and deletions, fusions, and copy number variants. Pre-treatment EGFR ctDNA allele fractions were also determined by BEAMing, a technique based on droplet digital PCR followed by flow cytometry. Pre-treatment tumor EGFR status was assessed by the therascreen EGFR test. Results: In all 57 pre-treatment samples profiled, plasma-based ctDNA analysis detected the initial EGFR driver and T790M resistance mutations that were identified in the matched tumor. Interestingly, we found that 12% (7/57) of patients had evidence of compound EGFR driver mutations at baseline, including E709A-L858R, K860I-L858R, and L718V-L858R. EGFR T790M mutations in plasma were observed subclonally (present on average at 40% of the allele fraction of the driver mutation), suggesting tumor heterogeneity at baseline. The correlation coefficients (r) between Guardant360 and BEAMing for EGFR L858R, Exon19Del, and T790M were 0.90, 0.92, 0.95, respectively. Upon progression on rociletinib, 5% of patients (3/57) developed the EGFR C797S resistance mutation, 5% (3/57) developed focal MET amplification, and 2% (1/57) developed a NTRK1 fusion that were not present in the matched baseline plasma. Additionally, 4 deleterious BRCA1/2 alterations (2 germline and 2 somatic) were identified, with the somatic alterations emerging at progression. In 14% (8/57) of the patients, mutations in genes involved in the RAS/RAF signaling pathway, including KRAS Q61H, KRAS K117N and NF1 Q1822*, emerged or increased at progression. Conclusions: Plasma ctDNA revealed heterogeneity and multiple mechanisms of resistance in rociletinib treated patients. Thus comprehensive ctDNA sequencing allows for the identification of potentially actionable alterations and may help inform the choice of next therapy for patients progressing on a third-generation EGFR TKI. Citation Format: Elena Helman, Andrew D. Simmons, Chris A. Karlovich, Thomas C. Harding, Mitch Raponi, Darya I. Chudova, Daniel A. Simon, Richard B. Lanman, AmirAli Talasaz. Comprehensive ctDNA sequencing reveals mechanisms of resistance to rociletinib in EGFR T790M-mutated NSCLC [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1009. doi:10.1158/1538-7445.AM2017-1009

1249P - Detection of EGFR T790M resistance mutation: real-time allele-specific PCR versus Sanger sequencing

Lung cancer is the most common cause of death from cancer worldwide, and 85-90% of lung cancers are non-small cell lung cancer (NSCLC). Presence of driver mutations in epidermal growth cell receptor (EGFR) gene in a subset of NSCLC has led to the use of tyrosine kinase inhibitors (TKI) that inhibit the EGFR signalling pathway. Tumours which harbour certain EGFR mutations may exhibit initial response to EGFR-TKIs, but many will develop resistance mutations post-treatment, commonly at amino acid position 790 (T790M) of exon 20. Newer EGFR inhibitors with activity against T790M-mutated NSCLC have recently been made available. Accurate detection of T790M in patients whose disease progressed on initial TKI therapy is thus vital for subsequent management. Here, we evaluated the performance of Sanger sequencing in detecting T790M mutation against a real-time allele-specific PCR. Ninety-six FFPE samples sent to our laboratory for T790M mutation detection by cobas® EGFR Mutation test (Roche), between July 2014 and March 2016 were included in this study. Archived extracts were used for Sanger sequencing of EGFR exon 20 using an in-house developed protocol. T790M was detected in 49.5% (47/95) and 47.9% (46/96) of the samples by the cobas® assay and Sanger sequencing respectively. Taking cobas® assay as the gold standard for 95 samples with valid real-time PCR results, Sanger sequencing yielded a sensitivity of 95.7% (45/47) and specificity of 100% (48/48). Of the 3 discordant results, cobas® assay detected T790M in 2 samples (both with tumour contents <30%) not detectable by Sanger sequencing; while Sanger sequencing detected T790M in one sample which repeatedly yielded an inconclusive result for exon 20 on the cobas® assay. Overall, concordance rate between the two methods was 96.9% (93/96). Sanger sequencing was generally comparable to, but slightly less sensitive than real-time PCR in detecting T790M. Sanger sequencing may be useful in the event of inconclusive results by the real-time assay. Otherwise, for post-treatment T790M mutation testing, where initial driver mutations had already been identified, Sanger sequencing, which requires samples with higher tumour content, offers little advantage over real-time PCR.

Abstract B52: Bioenergetic switch confers acquired resistance to BEZ235 in EGFR T790M-mutant non-small cell lung cancer

Abstract Introduction: Acquired resistance (AQR) continues to be source of treatment failure in EGFR inhibitor therapy and subsequent second-line strategies. In this study, AQR to the PI3K/mTOR inhibitor BEZ235 was generated in EGFR T790M non-small cell lung cancer (NSCLC) cells refractory to EGFR inhibitors to better understand AQR in this setting. Methods: Acquired resistant clones of H1975 were generated by continual exposure of H1975 cells to parental IC50 concentrations of BEZ235, followed by monoclonal selection. Phenotypic and protein analysis were carried out using standard techniques. Differentially expressed genes were determined using Affymetrix Gene 1.0ST analysis. Combination analysis was carried out using Chou and Talalay's median-effect equation. Oxygen consumption rates (OCR) were measured using the Seahorse XFp analyzer. Metabolomic analysis was carried out with 1H NMR. Depletion of mitochondrial DNA (mtDNA) was achieved by ethidium bromide treatment. Results: Two resistant clones were generated with stably higher IC50 values (Clone 5.2 μM, Clone 6 7.8μM) to parental H1975 cells (0.32μM) after 6 months. The clones were resistant to other PI3K and mTOR inhibitors but not chemotherapeutic drugs, indicating class-specific resistance. Compared to parental cells, the clones exhibited a reduced G1 block, increased migratory capability, reduced PTEN and increased p-AKT. Gene array analysis revealed monocarboxylate transporters as top differentially expressed genes, prompting an investigation of glycolytic status. Proliferation was inhibited in the absence of glucose for the AQR clones but not parental cells. Compared to parental cells, AQR cells were more sensitive to the glycolytic inhibitor, 3BP. Combination treatment with 3BP and BEZ235 reversed the resistance of AQR cells, while in parental cells the combination was antagonistic. Resistant clones had higher extracellular lactate, and lower reactive oxygen species and ATP levels. Metabolomic analysis indicated that the clones had increased intracellular glucose, lactate, NADH and glutamine levels, consistent with enhanced glycolysis. The AQR clones also had lower OCR, reflecting impaired mitochondrial respiratory function. Depletion of mitochondrial DNA in parental cells led to resistance to PI3K and mTOR inhibitors, but not cisplatin. Conclusion: These results highlight that cells could acquire drug resistance through a bioenergetics switch from mitochondrial respiration to glycolysis. Citation Format: Bhaskar Bhattacharya, King Xin Koh, Mohamed Feroz Mohamed Omar, Sarah Low, Juleen Tan, Nur Sabrina Sapari, Barry Iacopetta, Ross Soo, Mounia Beloueche-Babari, Richie Soong. Bioenergetic switch confers acquired resistance to BEZ235 in EGFR T790M-mutant non-small cell lung cancer. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2015 Nov 5-9; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl 2):Abstract nr B52.

Luteolin is effective in the non‐small cell lung cancer model with L858R/T790M EGF receptor mutation and erlotinib resistance

Non-small cell lung cancer (NSCLC) is one of the most commonly diagnosed malignancies in the world. Small-molecule inhibitors of the EGF receptor's tyrosine kinase domain (TKIs), including gefitinib and erlotinib, have been widely used for treating NSCLC. Unfortunately, nearly all patients after initially experiencing a marked improvement while on these drugs, eventually progress to acquire resistance to TKIs. Because there is no effective therapeutic strategy to treat TKI-resistant NSCLC, we evaluated the effects of luteolin, a naturally occurring flavanoid, on T790M mutant NSCLC cells. The effect of luteolin on the viability of NSCLC and normal cell lines was investigated using the Cell Counting Kit-8 (CCK-8) assay. Luteolin-induced apoptosis was assessed by bivariate FITC-annexin V/PI assay, and Western blots were used to measured apoptotic proteins. Co-immunoprecipitation was used to determine the effect of luteolin on the interaction between Hsp90 and mutant EGF receptors. The effect of luteolin on the Akt/mTOR pathway was studied using Western blotting analysis. Its anti-tumour efficacy in vivo was examined in a mouse xenograft model. Luteolin exerted significant anti-tumourigenic effects on the EGF receptor L858R/T790M mutation and erlotinib-resistant NSCLC both at the cellular and animal levels. Mechanistically, luteolin induced degradation of the EGF receptor by inhibiting the association of Hsp90 with the mutant EGF receptor, and, therefore, prevented PI3K/Akt/mTOR signalling, which resulted in NSCLC cell apoptosis. Luteolin may be a potential candidate for NSCLC therapy, especially for treatment of patients with acquired erlotinib-resistant NSCLC.

Effect of simvastatin on the resistance to EGFR tyrosine kinase inhibitors in a non-small cell lung cancer with the T790M mutation of EGFR

Although non-small cell lung cancer (NSCLC) tumors with activating mutations in the epidermal growth factor receptor (EGFR) are highly responsive to EGFR tyrosine kinase inhibitors (TKIs) including gefitinib and erlotinib, development of acquired resistance is almost inevitable. Statins show antitumor activity, but it is unknown whether they can reverse EGFR-TKIs resistance in NSCLC with the T790M mutation of EGFR. This study investigated overcoming resistance to EGFR-TKI using simvastatin. We demonstrated that addition of simvastatin to gefitinib enhanced caspase-dependent apoptosis in T790M mutant NSCLC cells. Simvastatin also strongly inhibited AKT activation, leading to suppression of β-catenin activity and the expression of its targets, survivin and cyclin D1. Both insulin treatment and AKT overexpression markedly increased p-β-catenin and survivin levels, even in the presence of gefitinib and simvastatin. However, inhibition of AKT by siRNA or LY294002 treatment decreased p-β-catenin and survivin levels. To determine the role of survivin in simvastatin-induced apoptosis of gefitinib-resistant NSCLC, we showed that the proportion of apoptotic cells following treatment with survivin siRNA and the gefitinib–simvastatin combination was greater than the theoretical additive effects, whereas survivin up-regulation could confer protection against gefitinib and simvastatin-induced apoptosis. Similar results were obtained in erlotinib and simvastatin-treated HCC827/ER cells. These findings suggest that survivin is a key molecule that renders T790M mutant NSCLC cells resistant to apoptosis induced by EGFR-TKIs and simvastatin. Overall, these data indicate that simvastatin may overcome EGFR-TKI resistance in T790M mutant NSCLCs via an AKT/β-catenin signaling-dependent down-regulation of survivin and apoptosis induction.

309 Potentiating the anti-tumor efficacy of molecular targeted therapy for hepatocellular carcinoma by inhibiting the insulin-like growth factor signaling pathway

Although non-small cell lung cancer (NSCLC) tumors with activating mutations in the epidermal growth factor receptor (EGFR) are highly responsive to EGFR tyrosine kinase inhibitors (TKIs) including gefitinib and erlotinib, development of acquired resistance is almost inevitable. Statins show antitumor activity, but it is unknown whether they can reverse EGFR-TKIs resistance in NSCLC with the T790M mutation of EGFR. This study investigated overcoming resistance to EGFR-TKI using simvastatin. We demonstrated that addition of simvastatin to gefitinib enhanced caspase-dependent apoptosis in T790M mutant NSCLC cells. Simvastatin also strongly inhibited AKT activation, leading to suppression of β-catenin activity and the expression of its targets, survivin and cyclin D1. Both insulin treatment and AKT overexpression markedly increased p-β-catenin and survivin levels, even in the presence of gefitinib and simvastatin. However, inhibition of AKT by siRNA or LY294002 treatment decreased p-β-catenin and survivin levels. To determine the role of survivin in simvastatin-induced apoptosis of gefitinib-resistant NSCLC, we showed that the proportion of apoptotic cells following treatment with survivin siRNA and the gefitinib–simvastatin combination was greater than the theoretical additive effects, whereas survivin up-regulation could confer protection against gefitinib and simvastatin-induced apoptosis. Similar results were obtained in erlotinib and simvastatin-treated HCC827/ER cells. These findings suggest that survivin is a key molecule that renders T790M mutant NSCLC cells resistant to apoptosis induced by EGFR-TKIs and simvastatin. Overall, these data indicate that simvastatin may overcome EGFR-TKI resistance in T790M mutant NSCLCs via an AKT/β-catenin signaling-dependent down-regulation of survivin and apoptosis induction.