Gefitinib-resistant Cell Lines Research Articles

Chronic treatment of non-small-cell lung cancer cells with gefitinib leads to an epigenetic loss of epithelial properties associated with reductions in microRNA-155 and -200c.

BackgroundThe EGFR tyrosine kinase inhibitor gefitinib is used in therapy for non-small-cell lung cancer (NSCLC). However, its application is limited by resistance-accelerated disease progression, which is accompanied by the epithelial-to-mesenchymal transition (EMT). In the present study, we performed multiple expression analyses of microRNAs (miRNAs) and quantified the expression of several related EMT players in gefitinib-resistant NSCLC cells.Methods and resultsTo establish gefitinib-resistant NSCLC cells, gefitinib-sensitive HCC827 cells, which exhibit an in-frame deletion [E746-A750] in EGFR exon 19, were exposed to gefitinib for at least 1.5 months. Next, to profile “gefitinib-resistant HCC827 (HCC827GR)” cells, which have a secondary T790M mutation in EGFR exon 20, a miRNA array analysis was performed in HCC827 and HCC827GR cells. The greatest differences were seen in the levels of miR-155 and miR-200c, which essentially disappeared in HCC827GR cells. In addition to these reductions, the levels of smad2 and zeb1, which are both key players in EMT and targets for miR-155 and miR-200c, respectively, were dramatically increased in HCC827GR cells. In HCC827GR cells, the expression of epithelial-cadherin (E-cadherin) was greatly reduced with repressive histone modifications, whereas vimentin, which is expressed in mesenchymal cells, was dramatically increased with active histone modifications. In another gefitinib-resistant NSCLC cell line (H1975 cells), similar to the findings in HCC827GR cells, both miR-155 and miR-200c were absent, and the EMT was induced along with epigenetic modifications. Interestingly, the inhibition of both miR-155 and miR-200c in HCC827 cells without gefitinib induced significant increases in smad2 and zeb1 along with a dramatic decrease in E-cadherin and a slight increase in vimentin. Furthermore, although the inhibition of these miRNAs in HCC827 cells decreased gefitinib sensitivity, this dual-inhibition in HCC827 cells without gefitinib did not produce a secondary T790M mutation in EGFR exon 20.Conclusion and implicationsThese results suggest that chronic treatment of NSCLC cells with gefitinib changes the expression of miRNAs, including dramatic reductions in miR-155 and miR-200c along with an EGFR mutation. Furthermore, this depletion of miR-155 and miR-200c may be associated with the EMT along with histone modifications, and may contribute to the decrease in the sensitivity to gefitinib independent of a secondary EGFR mutation.

P2.05-005 Mechanism of Radiotherapy in Reduction/Delay of T790M-Mediated EGFR TKI Resistance: Topic: Biology

EGFR T790M mutation accounts for more than 50% of acquired resistance to TKI. In pre-clinical, EGFR-TKI resistant cells with T790M exhibited enhanced sensitivity to radiation, suggesting the potential of radiotherapy in reduction and delay of T790M-mediated EGFR TKI resistance. Under different radiotherapy dose and times, we use droplet digital PCR to observe the emerging time of T790M and its proportion during chronic exposure to gefitinib in TKI-sensitivity cell lines, and to evaluate the anti-tumor effect of early radiation combined with gefitinib in xenograft model with different proportion of T790M. Furthermore, we performed miRNA microarray to screen miRNAs differentially expressed in the paired NSCLC gefitinib-sensitivity cell lines and gefitinib resistant cell lines and find potential molecular markers of T790M mutation. Our data showed radiation combined with gefitinib delayed the occurrence of EGFR T790M mutation compared to gefitinib alone in T790M wild type (TKI-sensitive) cell line and it also reduced the T790M mutation abundance in de novo T790M mutation (TKI-resistant) cell line. The phenomena was also confirm in mice xenograft model. In addition, our results showed TKI-resistant (induced T790M mutation) cells had higher radiosensitivity than TKI-sensitive cells. miRNA array showed miR-1275 was the one of the most significantly elevated miRNAs in TKI-resistant cells. Knockdown of miRNA-1275 significantly decreased the radiosensitivity of TKI-resistant cells. Western blot showed knockdown of miR-1275 affected proteins relating to cell proliferation and apoptosis. Bioinformatics showed SPOCK1 might be one of the targets of miRNA-1275. Our results contribute to understand molecular mechanisms of T790M-mediated EGFR-TKI resistance, but also provide a new therapeutic strategy for patients in advanced NSCLC to aid expansion of the effectiveness of TKI treatment through radiotherapy.

MiR-200c enhances sensitivity of drug-resistant non-small cell lung cancer to gefitinib by suppression of PI3K/Akt signaling pathway and inhibites cell migration via targeting ZEB1

Acquired resistance to epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) is a major obstacle in the treatment of non-small cell lung cancer (NSCLC) patients. We explored the role of miR-200c in modulating the sensitivity of gefitinib-resistant NSCLC cells and examined the underlying mechanism. The gefitinib-resistant cell line PC-9-ZD and its parental PC-9 cells were used. Growth inhibition was detected by MTT assay. The cell apoptosis was detected by Annexin V/PI assay. Cell migration was assessed by wound-healing assay. RT-PCR was used to detected levels of miR-200c and ZEB1. The PI3k, Bcl-2, Bax, caspase-3 and ZEB1 protein expression were detected using Western blot analysis, and TUNEL, Immunohistochemistry for xenograft model. PC-9-ZD cells had low level of miR-200c expression compared to its parental PC-9 cells. PC-9-ZD cells with miR-200c transfection were more sensitive to gefitinib treatment. Apoptosis induced by gefitinib was observed in PC-9-ZD cells with miR-200c transfection significantly. The levels of phosphorylated-Akt and Bcl-2 expression decreased and levels of Bax and Caspase-3 expression increased in PC-9-ZD cells with miR-200c transfection. Cell migration was inhibited and ZEB1 mRNA level and protein expression were significantly decreased in PC-9-ZD cells with miR-200c transfection. Further in gefitinib resistant xenograft model, miR-200c enhanced sensitivity of gefitinib and induced apoptosis significantly through PI3K/Akt signaling pathway and targeting ZEB1. These results provided insights into the functions of miR-200c and offered an alternate approach in treating gefitinib-resistance NSCLC.

MiR-124 modulates gefitinib resistance through SNAI2 and STAT3 in non-small cell lung cancer.

Gefitinib is used as a first-line treatment for advanced non-small cell lung cancer (NSCLC). Unfortunately, most NSCLC patients inevitably develop gefitinib resistance during treatment. In addition to EGFR mutation status, the mechanisms involved are largely unknown. In this study, we showed that miR-124, a tumor suppressor, was significantly down-regulated in gefitinib-resistant NSCLC patients and cell lines compared with gefitinib-sensitive patients and cell lines. In addition, the miR-124 depletion induced gefitinib resistance, and miR-124 overexpression sensitized gefitinib-resistant cells to gefitinib. Mechanistic analysis revealed that miR-124 decreased SNAI2 and STAT3 expression by directly targeting their 3'UTRs and that knocking down SNAI2 or STAT3 partly reversed the gefitinib resistance induced by miR-124 depletion. Our data demonstrate that the miR-124 plays a new critical role in acquired resistance to gefitinib and that the manipulation of miR-124 might provide a therapeutic strategy for reversing acquired gefitinib resistance.

MiR-30a-5p Overexpression May Overcome EGFR-Inhibitor Resistance through Regulating PI3K/AKT Signaling Pathway in Non-small Cell Lung Cancer Cell Lines.

Lung cancer is one of the most common deadly diseases worldwide, most of which is non-small cell lung cancer (NSCLC). The epidermal growth factor receptor (EGFR) mutant NSCLCs frequently respond to the EGFR tyrosine kinase inhibitors (EGFR-TKIs) treatment, such as Gefitinib and Erlotinib, but the development of acquired resistance limits the utility. Multiple resistance mechanisms have been explored, e.g., the activation of alternative tyrosine kinase receptors (TKRs) sharing similar downstream pathways to EGFR. MicroRNAs (miRNAs) are short, endogenous and non-coding RNA molecules, regulating the target gene expression. In this study, we explored the potential of miR-30a-5p in targeting the EGFR and insulin-like growth factor receptor-1 (IGF-1R) signaling pathways to overcome the drug resistance. IGF-1R is one of the tyrosine kinase receptors that share the same EGFR downstream molecules, including phosphatidylinositol 3 kinase (PI3K) and protein kinase B (AKT). In this work, an in vitro study was designed using EGFR inhibitor (Gefitinib), IGF-1R inhibitor (NVP-AEW541), and miRNA mimics in two Gefitinib-resistant NSCLC cell lines, H460 and H1975. We found that the combination of EGFR and IGF-1R inhibitors significantly decreased the phosphorylated AKT (p-AKT) expression levels compared to the control group in these two cell lines. Knockdown of phosphoinositide-3-kinase regulatory subunit 2 (PIK3R2) had the same effect with the dual inhibition of EGFR and IGF-1R to reduce the expression of p-AKT in the signaling pathway. Overexpression of miR-30a-5p significantly reduced the expression of the PI3K regulatory subunit (PIK3R2) to further induce cell apoptosis, and inhibit cell invasion and migration properties. Hence, miR-30a-5p may play vital roles in overcoming the acquired resistance to EGFR-TKIs, and provide useful information for establishing novel cancer treatment.

Abstract 1893: The effect of kinase signaling for miR-205 regulation in gefitinib-resistant lung cancer cell lines

Abstract Lung cancer is the leading cause of cancer related death in the world. Platinum-based combination regimen or molecular target drugs, such as EGFR tyrosine kinase inhibitors (EGFR-TKIs) and ALK inhibitors are used for first line chemotherapy of NSCLC. Somatic mutation in the tyrosine kinase domain of epidermal growth factor receptor (EGFR) have been identified in NSCLC and those mutations confer sensitivity to the EGFR-TKIs such as gefitinib. Unfortunately, it is well known that the almost cases are developed to drug resistance after chemotherapy. Several EGFR-TKI resistant mechanisms have been reported, including gatekeeper mutation (T790M), c-MET amplification and ErbB3 activation. Re-biopsy is generally required for determine the resistance mechanism and second line chemotherapy. However, re-biopsy is invasive test for cancer patients. Recently, microRNAs (miRNAs) are paid attention as biomarkers for cancer diagnosis and sensitivity to chemotherapy in various cancers. In the previous study, we revealed that the miRNA biosynthesis pathway is critical for maintain the cisplatin resistant phenotype. Further, it was reported that EGFR modulated microRNA maturation through the phosphorylation of AGO2. Protein phosphorylation is one of most important post transcriptional modification mechanisms and miRNA is also associated with fine tuning of mRNA expression. Thus, we focused on the relationship between miRNA expression and kinase signaling in gefitinib resistance. In this study, we performed characterization of gefitinib resistant cell lines, PC-9/MET200 and PC-9/MET1000 established from NSCLC cell line, PC-9, which were confirmed to have a c-MET amplification using miRNA microarray and quantitative PCR. Furthermore, we analyzed miRNA activity and kinase signaling using a luciferase reporter assay system, siRNA, RTK/phosphokinase protein array and kinase inhibitors. We revealed that miR-205 was significantly elevated in both gefitinib resistant cell lines. By the computational analysis using miRNA target prediction database, we found that ErbB3 was a target of miR-205. However, ErbB3 expression levels were rather up-regulated and highly phosphorylated in both resistant cell lines compared with a parental cell line. Under ErbB3 knockdown condition, miR-205 expression levels were slightly down regulated. Furthermore, under c-MET knockdown or Foretinib treatment condition, miR-205 activity were down regulated and ErbB3 dephosphorylated in resistant cell lines. This down-regulation of miR-205 appears to be mediated by inhibition of kinase signals. Moreover, we found that some kinase inhibitors suppressed miR-205 activity in gefitinib resistant cell lines. In conclusion, our results suggest that alterations of kinase signals are more effective for miR-205 regulation than protein expression of target molecule itself, such as ErbB3. Citation Format: Toshihiro Suzuki, Ikuko Nagasawa, Toshimitsu Yamaoka, Tohru Ohmori, Kazuto Nishio, Kiyotaka Koyama, Yuki Ogasawara. The effect of kinase signaling for miR-205 regulation in gefitinib-resistant lung cancer cell lines. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1893.

Abstract 2482: The Calcineurin/NFAT pathway mediates tumor initiating cell and drug resistance in lung cancer through SOX2 enhancer binding and ALDH upregulation

Abstract Tumor initiating cells (TIC) are a small population of cancer cells with enhanced tumorigenicity and drug resistance. Their stemness properties could be activated by stress-induced cell plasticity but the mechanisms remain to be studied. Calcium signaling is important for integrating cell responses to intra- and extracellular stresses. The role of its downstream pathway, calcineurin/NFAT, in lung TIC has not been explored. This study investigated the role and mechanisms of calcineurin/NFAT in regulating TIC and drug resistance by analyzing NFATc2 expression in multiple TIC populations and functional evaluation using in vitro and in vivo models. In tumor spheres and TIC isolated by marker-based flow cytometry, NFATc2 showed overexpression and higher luciferase reporter activities. Knockdown of NFATc2 reduced TIC marker proportions and suppressed TIC properties including pluripotency genes expression, sphere formation, cell mobility and drug resistance in vitro. Xenograft models and limiting dilution assay showed shNFATc2 effectively suppressed tumorigenesis and reduced TIC frequency. Stable NFATc2 knockdown sensitized tumors to cisplatin and gefitinib treatment. In contrast, TIC-supportive effects were observed in vitro and in vivo when NFATc2 was overexpressed. Further, NFATc2 was activated in stable gefitinib or cisplatin resistant cell lines, and knockdown of NFATc2 sensitized them to drug treatment. These data implicated NFATc2 is involved in lung TIC maintenance and drug resistance. To further investigate the molecular mechanisms of how NFATc2 mediate these roles, we analyzed pluripotency genes and observed a significant correlation between NFATc2 and SOX2 expression in lung cancer cell lines and human lung carcinomas. Computational analysis predicted NFATc2 binding sequences in SOX2 regulatory regions. Detailed studies including luciferase reporter assay, site-directed mutagenesis and CHIP-qRCR confirmed NFATc2 could regulate SOX2 expression through binding to its enhancer. Furthermore, immunohistochemistry on human lung cancers showed significant correlation between expressions of SOX2 and the anti-oxidative stem cell marker ALDH, suggesting SOX2 regulates ALDH expression. In vitro, NFATc2 knockdown suppressed ALDH1A1 expression but it was rescued by SOX2 overexpression. Vice versa, ALDH1A1 was upregulated in NFATc2 overexpressing cells but this was prevented by SOX2 knockdown. Functionally, reactive oxidative species (ROS) levels assessed by flow cytometry were suppressed by activated NFATc2/SOX2/ALDH1A1 axis, while treatment with the ROS inhibitor N-acetylcysteine reversed the sensitization of shNFATc2 on cisplatin treatment. Together, the data showed NFATc2 is involved in the regulation of TIC phenotypes in lung cancer. It increases drug resistance by ROS scavenging mediated by the SOX2/ALDH1A1 axis. Citation Format: Zhi-Jie Xiao, Jing Liu, Vicky PC Tin, Maria P. Wong. The Calcineurin/NFAT pathway mediates tumor initiating cell and drug resistance in lung cancer through SOX2 enhancer binding and ALDH upregulation. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2482.

Abstract 3034: Overcoming gefitinib resistance in non-small-cell lung cancer by inducing epidermal growth factor receptor (EGFR) degradation via methionine 790 oxidation

Abstract Personalized therapy is becoming a dominant cancer therapeutic strategy, Epidermal Growth Factor Receptor (EGFR) tyrosine kinase inhibitors (TKIs) have been developed to treat non-small-cell lung cancer (NSCLC) patients with EGFR mutation but they only inhibit EGFR phosphorylation, acquired-resistance still remains unavoidable without EGFRT790M removal. Here, we report a new treatment strategy to overcome such drug resistance by selectively inducing EGFRT790M degradation via specific stimulation of methionine 790 (M790) oxidation. The basal reactive oxygen species (ROS) levels in EGFRT790M containing gefitinib-resistant NSCLC cell lines were substantially high and 63 clinical lung tumors showed higher NADPH oxidase 2 (NOX2) expression than 61 normal lung tissues which may contribute to high basal ROS in cancer. Interestingly, only NOX3 was upregulated by sanguinarine, a pharmacological agent to elevate ROS, resulted in EGFR over-oxidation and degradation as well as apoptosis. By contrast, such responses were lacking in EGFRWild-type (WT) cells, suggesting a new promising drug development strategy with wide therapeutic window between EGFRT790M and EGFRWT. Selective EGFRT790M degradation was manipulated by REDOX imbalance between NOX3 and methionine reductase (MsrA). When NOX3 was activated, NADPH, the key substrate of MsrA, was depleted to generate excessive ROS, resulting in inhibition of MsrA physiological reduction function on oxidized-methionine, thus localized methionine 790 oxidation of EGFRT790M occurred. Furthermore, the in vivo tumor suppression effect of sanguinarine, NOX3 upregulation and EGFR degradation were confirmed. These findings indicate that specific inducing EGFRT790M degradation via manipulating REDOX imbalance between NOX3 and MsrA would be promising strategy for treating gefitinib-resistant NSCLC. Citation Format: Elaine Lai-Han Leung, Xing-Xing Fan, Maria Pik Wong, Zhi-Hong Jiang, Zhong-Qiu Liu, Xiao-Jun Yao, Lin-Lin Lu, Yan-Ling Zhou, Li-Fong Yau, Vicky Pui-Chi Tin, Liang Liu. Overcoming gefitinib resistance in non-small-cell lung cancer by inducing epidermal growth factor receptor (EGFR) degradation via methionine 790 oxidation. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3034.

Targeting Adenine Nucleotide Translocase-2 (ANT2) to Overcome Resistance to Epidermal Growth Factor Receptor Tyrosine Kinase Inhibitor in Non-Small Cell Lung Cancer.

EGFR tyrosine kinase inhibitor (EGFR-TKI) therapy has achieved favorable clinical outcomes in non-small cell lung cancer (NSCLC) patients with EGFR mutations. However, patients eventually develop resistance to EGFR-TKIs by several mechanisms. Adenine nucleotide translocase-2 (ANT2) is an oncogenic mitochondrial membrane-associated protein. We investigated the therapeutic potential of ANT2 inhibition to EGFR-TKI resistance in NSCLC using gefitinib-sensitive (PC9 and HCC827) and gefitinib-resistant (H1975 and HCC827/GR) NSCLC cell lines. ANT2 was inhibited by transfecting cells with an ANT2-specific shRNA. ANT2 expression was elevated in the H1975 and HCC827/GR cells compared with the PC9 and HCC827 cells. ANT2 upregulation in gefitinib-resistant cells was associated with increased SP1 binding to the ANT2 promoter. ANT2-specific shRNA decreased NSCLC cell viability. Moreover, ANT2-specific shRNA sensitized the H1975 and HCC827/GR cells to gefitinib, accompanied by HSP90 and EGFR downregulation. ANT2-specific shRNA also inactivated the PI3K/Akt signaling pathway in the H1975 and HCC827/GR cells, which was mediated by the suppression of miR-221/222 levels and by the subsequent restoration of PTEN. In EGFR-TKI-treated NSCLC patients, ANT2 expression was higher in patients exhibiting poor responses compared with patients showing excellent responses. Furthermore, ANT2 expression increased in tumor tissues biopsied after acquiring gefitinib resistance compared with tissues before gefitinib treatment. These findings suggest that ANT2 overexpression contributes to EGFR-TKI resistance in NSCLC and that ANT2 targeting may be considered a novel strategy for overcoming this resistance. Mol Cancer Ther; 15(6); 1387-96. ©2016 AACR.

Cetuximab-modified mesoporous silica nano-medicine specifically targets EGFR-mutant lung cancer and overcomes drug resistance.

Drug resistance to tyrosine kinase inhibitor (TKI) is the main obstacle for efficient treatment of epidermal growth factor receptor (EGFR)-mutant lung cancer patients. Here we design a cetuximab-capped mesoporous silica nanoparticle (MP-SiO2 NP) as the drug carrier to specifically target EGFR-mutant lung cancer cells and efficiently release loaded drugs including doxorubicin and gefitinib. This innovative nano-medicine can specifically target lung cancer cells with high EGFR expression rather than those with low EGFR level. Treatment of a gefitinib-resistant cell line derived from PC9 cell (PC9-DR) with the gefitinib-loaded cetuximab-capped MP-SiO2 NP showed a significant inhibition of cell growth. Moreover, this nano-medicine successfully suppressed the progression of PC9-DR xenograft tumors. This tumor suppression was due to the endocytosis of large amount of nano-medicine and the effective gefitinib release induced by high glutathione (GSH) level in PC9-DR cells. Collectively, our study provides a novel approach to overcome EGFR-TKI resistance using cetuximab modified MP-SiO2 NP, which holds strong potential for effective management of EGFR-mutant lung cancer.

Molecular Understanding of the Acquisition of Resistance to Anti-cancer Drugs Associated with the Exacerbation of Cancer.

Gefitinib and erlotinib target the ATP cleft in the tyrosine kinase EGFR, which is overexpressed in 40-80 percent of non-small-cell lung cancer (NSCLC) and many other epithelial cancers. However, the application of gefitinib is ultimately limited by the emergence of mutations and other molecular mechanisms conferring drug resistance. Furthermore, it has been considered that acquired resistance to gefitinib is associated with a clinically significant risk of accelerated disease progression. We previously established a new gefitinib-resistant NSCLC cell line, HCC827GR, which harbors the T790M mutation. Using HCC827GR, we found that the inhibition of adenosine A2a receptors of NSCLC regulated cancer proliferation and exacerbation, indicating that adenosine A2a receptors may be new targets for a novel strategy in NSCLC therapy. These findings suggest that multilayered crosstalk between G-protein coupled receptors (GPCRs) and EGFR may play an important role in regulating downstream signaling molecules that are implicated in the development of gefitinib-resistant NSCLC.

Paris Saponins enhance radiosensitivity in a gefitinib-resistant lung adenocarcinoma cell line by inducing apoptosis and G2/M cell cycle phase arrest.

Acquired resistance to epidermal growth factor inhibitors has been reported to be associated with cross‑resistance to radiation. Paris Saponins (PSs) exert a wide range of pharmacological activities, including cell apoptosis induction, multidrug resistance inhibition, angiogenesis inhibition and tumor cell migration by modulating various signaling pathways. The present study aimed to investigate the radiosensitization effects of PSII, PSVI and PSVII in a gefitinib‑resistant PC‑9‑ZD lung adenocarcinoma cell line, and the possible mechanism underlying their function. A clonogenic assay was performed to determine the effects of PS radiosensitization on the PC‑9‑ZD cell line. The cell cycle was analyzed by flow cytometry, and cell apoptosis was analyzed with Annexin V/propidium iodide and Hoechst staining. Protein expression levels were detected by western blotting. The results of the present study revealed a significant increase in PC‑9‑ZD cell line radiosensitivity following treatment with PSs. PSs induced G2/M cell cycle phase arrest and apoptosis of the irradiated PC‑9‑ZD cells. Notably, the expression levels of B cell lymphoma 2 (Bcl‑2) were downregulated, and those of caspase‑3, Bcl‑2‑associated X protein (Bax) and p21/Waf1/Cip1 were upregulated following treatment with PSs. The present results demonstrated that PSs induced radiosensitivity in gefitinib‑resistant cells by inducing G2/M phase arrest and by enhancing the apoptotic response via the modulation of caspase‑3, Bax, Bcl‑2 and p21/Waf1/Cip1 expression.

Abstract C134: Alternative pathways associated with resistance to tyrosine kinase inhibitors in glioblastoma

Abstract Glioblastoma (GBM) is the most aggressive brain tumor in adults and remains incurable despite multimodal intensive treatment regimens. The majority of GBM tumors show a mutated or overexpressed EGFR. However, the kinase domain mutations that usually correlate with response to the tyrosine kinase inhibitors in other cancers are infrequent in glioblastomas and phase II trials of the tyrosine kinase inhibitor (TKI), gefitinib showed no survival benefit in glioblastoma. Furthermore, tumors treated with the TKIs will inevitably recur, highlighting the need to identify signaling pathways involved in GBM resistance to TKIs. We isolated and developed gefitinib-resistant cell lines and subjected those cell lines to RNA sequencing. By evaluating transcriptomic profiles of the resistant cell lines, we were able to identify several upregulated genes, including a number of other tyrosine kinase receptors such as ROS1, DDR1 and PDGFRA that are known to control pathways downstream of EGFR. The upregulation of these genes was confirmed at the protein level by western blot. Treatment with our highly specific pyrazole ROS1 inhibitor in ROS1-overexpressing cell lines led to sensitization to low doses of gefitinib. Combined treatment with gefitinib and ROS1 inhibitor induced massive cell death by apoptosis following a prolonged cell cycle arrest in S phase. Our current study led to the discovery of alternative pathways used by GBM cells to evade cell death following treatment with gefitinib and identifies new therapeutic targets to prevent GBM cell resistance to the drug. Citation Format: Hashim M. Aljohani, Robert F. Koncar, Ahmed Zarzour, Byung Sun Park, So Ha Lee, El Mustapha Bahassi. Alternative pathways associated with resistance to tyrosine kinase inhibitors in glioblastoma. [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 C134.

244-MPT overcomes gefitinib resistance in non-small cell lung cancer cells.

The epidermal growth factor receptor (EGFR) is known to play a critical role in non-small cell lung cancer(NSCLC). Several EGFR tyrosine kinase inhibitors(TKIs), such as gefitinib, have been used as effective clinical therapies for patients with NSCLC. Unfortunately, acquired resistance to gefitinib commonly occurs after 6-12 months of treatment. The resistance is associated with the appearance of the L858R/T790M double mutation of the EGFR. In our present study, we discovered a compound,referred to as 244-MPT, which could suppress either gefitinib-sensitive or -resistant lung cancer cell growth and colony formation, and also suppressed the kinase activity of both wildtype and double mutant (L858R/T790M) EGFR. The underlying mechanism reveals that 244-MPT could interact with either the wildtype or double-mutant EGFR in an ATP-competitive manner and inhibit activity. Treatment with 244-MPT could substantially reduce the phosphorylation of EGFR and its downstream signaling pathways, including Akt and ERK1/2 in gefitinib-sensitive and -resistant cell lines. It was equally effective in suppressing EGFR phosphorylation and downstream signaling in NL20 cells transfected with wildtype, single-mutant (L858R) or mutant (L858R/T790M) EGFR. 244-MPT could also induce apoptosis in a gefitinib-resistant cell line and strongly suppress gefitinib-resistant NSCLC tumor growth in a xenograft mouse model. In addition, 244-MPT could effectively reduce the size of tumors in a gefitinib-resistant NSCLC patient-derived xenograft (PDX) SCID mouse model. Overall, 244-MPT could overcome gefitinib-resistance by directly targeting the EGFR.

Abstract 5551: Anti-tumorigenic function of polyphenolic compounds on gefitinib resistant lung cancer

Abstract EGFR-mutant non-small cell lung cancer (NSCLC) is initially very sensitive to EGFR tyrosine kinase inhibitors (TKIs). Even with the remarkable effect of EGFR TKIs, patients eventually acquire resistance to gefitinib or elortinib, leading to a clinical challenge for overcoming TKI resistance. Some polyphenolic compounds are known as potential anti-tumorigenic compounds, such as resveratrol, curcumin or EGCG. However the function of these natural compounds in resistant NSCLC remains to be elucidated. Here, we identified a polyphenolic compound (named as compound A) from screening a set of natural compounds for anti-cancer effects on NSCLC. We found that compound A is a potential anticancer agent both in vivo and in vitro. Moreover, the growth inhibition of compound A turns out to be selective for cancer cells. Next, we further evaluated the growth inhibitory effect of compound A in two sets of NSCLC panels which are either sensitive or resistant to gefitinib treatment. Interestingly, the cell lines which are resistant to gefitinib are highly sensitive to compound A treatment, whereas the gefitinib-sensitive (GS) cell lines are not responsive to the compound A treatment. In gefitinib resistant (GR) cells, compound A increases expression of autophagy markers, p62 and LC3, which might result in the growth inhibition of the GR panel of cells but not in the GS cell panel. Moreover, we profiled the metabolic genes in the GR and GS cell lines. Surprisingly, compound A treatment significantly reduces the expression of a subset of enzymes associated with Warburg effect, which includes GLUT1, LDHA, PDK1, HK1, and HK2. As a result, compound A decreases Warburg effect, subsequently suppressing cell proliferation, especially of the GR cell lines. Taken together, compound A decreases Warburg effect and up-regulates autophagy process that may contribute to tumor suppression function of compound A in gefitinib-resistant cancer. Citation Format: Ai N. H. Phan, Yangsik Jeong. Anti-tumorigenic function of polyphenolic compounds on gefitinib resistant lung cancer. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 5551. doi:10.1158/1538-7445.AM2015-5551

Abstract 5563: Tripterygium induces apoptosis in NSCLC via mitochondria dysfunction

Abstract Lung cancer remains the leading cause of cancer deaths globally. Patients with non-small cell lung cancer (NSCLC) account for 80% of all lung cancer cases. Active mutation of EGFR was identified as one of the key anti-cancer target for NSCLC patients. Recently, tyrosine kinase inhibitor, like gefitinib which can specifically inhibit the activation of EGFR, emerges as a new potential anticancer drug. However, drug resistance remains an unsolved problem. Most of patient acquired resistance to this inhibitor within 12 months. Therefore, it is necessary and urgent to discover more effective potential agents as candidate drugs for treating gefitinib resistant NSCLC. Tripterygium, a triterpene extracted from the Chinese herb “Thunder of God Vine”, has been shown to have multiple bioactivities. Its anti-cancer effect has been proved in many kinds of cancers. However, the effect of Tripterygium on gefitinib-resistant NSCLC cells is still unknown. In this study, we examined the potency of Tripterygium in induction of apoptosis in a gefitinib-resistant NSCLC cell line and explored its underlying anti-cancer mechanism. Our results demonstrated that Tripterygium induced its apoptotic effect on NSCLC cells in a dose- and time-dependent manner. Moreover, the function of mitochondria was disrupted by the treatment of Tripterygium. The mitochondria membrane potential was gradually loss, and the ratio of Bax/Bcl-2 which is the indicator of mitochondria membrane integrity, was significantly up-regulated after the treatment of Tripterygium. Although the caspases were activated, the treatment of pan-caspase inhibitor could only partially inhibit the level of apoptosis. Moreover, the level of Hsp90 client proteins, EGFR and its downstream target AKT, were measured. Interestingly, both of them were remarkably decreased after Tripterygium treatment. Taken together, our data suggest that Tripterygium, which may be developed as a promising agent for gefitinib-resistant NSCLC patient, induced apoptosis through mitochondria dysfunction and EGFR degradation in gefitinib-resistant NSCLC cells. Citation Format: Xing-Xing Fan, Na Li, Jin-Lin Wu, Yan-Ling Zhou, Liang Liu, Jian-Xing He, Elaine L. Leung. Tripterygium induces apoptosis in NSCLC via mitochondria dysfunction. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 5563. doi:10.1158/1538-7445.AM2015-5563

Abstract 742: Effect of Hsp90 inhibitor NVP-AUY922 with radiation on lung adenocarcinoma cell lines with acquired resistance to EGFR-tyrosine kinase inhibitors

Abstract Recent progress in understanding of molecular pathology in lung adenocarcinoma has been changing the therapeutic strategy. Especially, tyrosine kinase inhibitors (TKIs) for epidermal growth factor receptor (EGFR) mutant lung adenocarcinoma have improved the outcomes. However acquired resistances to TKIs are observed in most of cases and how to overcome the resistances must be the key factor to make them curable. 90-kDa heat shock protein (Hsp90) is a chaperone protein that assists maturation of client proteins and EGFR is one of them. Reportedly, Hsp90 inhibitors have anti-tumor effect against not only EGFR-TKI sensitive lung adenocarcinomas but also those with EGFR-TKI resistantce. Furthermore Hsp90 inhibitor can increase radiosensitivity through inhibition of hypoxia-inducible factor-1α (HIF-1α), checkpoint kinase 1 (CHK1) and WEE1 G2 checkpoint kinase (WEE1). These facts prompted us to investigate the combined effect of Hsp90 inhibitors and radiation to EGFR-TKI resistant cells. We exposed Hsp90 inhibitor NVP-AUY922 (AUY) to Gefitinib-resistant lung adenocarcinoma cell lines, PC-9 with T790M (PC-9 GRt790m) which is well known secondary mutation with EGFR-TKI resistant cells and HCC827 with MET amplification (HCC827-GRmet) which is also well known mechanism of EGFR-TKI resistant. Our earlier work showed another EGFR-TKI resistant mechanism, acquiring cancer stem cell properties. We also used HCC827 with stem-cell like properties (HCC827-GRstem). To examine the anti-tumor effect, we conducted colonogenic assay with radiation. Then we conducted immunofluorescence staining for γH2AX and counted the foci to observe DNA double strand breaks. We also conducted cell cycle assay with propidium iodide-staining method using flow cytometry. The colonogenic assay showed anti-tumor effect in PC-9 GRt790m and HCC827-GRmet but HCC827-GRstem showed limited effect to AUY and radiation. In γH2AX staining, HCC827-GRmet showed prolonged DNA double strand breaks suggesting leading to apoptosis. In contrast, HCC827-GRstem showed rapid decrease of DNA double strand breaks. In cell cycle analysis, HCC827-GRstem showed smaller population of G2/M compared to HCC827-GRmet and parental HCC827. Taken together, AUY with radiation can be a effective therapy to EGFR-TKI resistant lung adenocarcinoma but stem-cell like properties cause resistant even these therapies. Citation Format: Yuho Maki, Shinsuke Hashida, Hiromasa Yamamoto, Kazuhiko Shien, Tomoaki Ohtsuka, Ken Suzawa, Masashi Furukawa, Junichi Soh, Hiroaki Asano, Kazunori Tsukuda, Shinichiro Miyoshi, Susumu Kanazawa, Shinichi Toyooka. Effect of Hsp90 inhibitor NVP-AUY922 with radiation on lung adenocarcinoma cell lines with acquired resistance to EGFR-tyrosine kinase inhibitors. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 742. doi:10.1158/1538-7445.AM2015-742

An Integrative Analysis of the Putative Gefitinib-resistance Related Genes in a Lung Cancer Cell Line Model System.

The epidermal growth factor receptor-tyrosine kinase inhibitors (EGFRTKI), such as gefitinib and erlotinib have improved the survival of patients with nonsmall cell lung cancer (NSCLC). Unfortunately, acquired resistance will eventually develop in most patients who initially respond to the therapy. Currently known molecular mechanisms for such an acquired resistance may interpret only about 70% of clinical cases. In this study, using NSCLC cell model H1650, we constructed a gefitinib resistant cell line H1650GR through long term drug exposure with increased doses. RNA sequencing and whole genome SNP array were applied to investigate the transcriptome and genome alterations possibly involved in gefitinib resistance. By comparing the expression profiles between H1650GR and H1650 cells, we identified a large set of differentially expressed genes (DEGs), including FOXM1. In the PI3K/AKT pathway, AKT activity was predicted to be inhibited. However, genes that play important roles in gefitinib-induced apoptosis, including TP53, FOXO3 and BAD, were not up-regulated. Ingenuity Pathway Analysis (IPA) canonical pathway analysis showed that p53 signaling was inhibited in H1650GR cells, with down-regulation of pro-apoptosis genes FAS, PUMA, NOXA, and upregulation of anti-apoptosis genes BIRC5/Survivin. Besides, a large number of immune response-related genes were differently expressed, the role of which in gefitinib resistance requires further investigation. Whole genome copy number alterations (CNAs) were also analyzed and NOXA was located in the H1650GR unique copy number loss region, 18q21. Our results suggested that the much higher EGFR-TKI resistance in H1650GR may be produced by the integration of multi-aspect factors.

Reciprocal positive regulation between Cx26 and PI3K/Akt pathway confers acquired gefitinib resistance in NSCLC cells via GJIC-independent induction of EMT.

Gefitinib efficiency in non-small-cell lung cancer (NSCLC) therapy is limited due to development of drug resistance. The molecular mechanisms of gefitinib resistance remain still unclear. In this study, we first found that connexin 26 (Cx26) is the predominant Cx isoform expressed in various NSCLC cell lines. Then, two gefitinib-resistant (GR) NSCLC cell lines, HCC827 GR and PC9 GR, from their parental cells were established. In these GR cells, the results showed that gefitinib resistance correlated with changes in cellular EMT phenotypes and upregulation of Cx26. Cx26 was detected to be accumulated in the cytoplasm and failed to establish functional gap-junctional intercellular communication (GJIC) either in GR cells or their parental cells. Ectopic expression of GJIC-deficient chimeric Cx26 was sufficient to induce EMT and gefitinib insensitivity in HCC827 and PC9 cells, while knockdown of Cx26 reversed EMT and gefitinib resistance in their GR cells both in vitro and in vivo. Furthermore, Cx26 overexpression could activate PI3K/Akt signaling in these cells. Cx26-mediated EMT and gefitinib resistance were significantly blocked by inhibition of PI3K/Akt pathway. Specifically, inhibition of the constitutive activation of PI3K/Akt pathway substantially suppressed Cx26 expression, and Cx26 was confirmed to functionally interplay with PI3K/Akt signaling to promote EMT and gefitinib resistance in NSCLC cells. In conclusion, the reciprocal positive regulation between Cx26 and PI3K/Akt signaling contributes to acquired gefitinib resistance in NSCLC cells by promoting EMT via a GJIC-independent manner.

Homoharringtonine induces apoptosis and inhibits STAT3 via IL-6/JAK1/STAT3 signal pathway in Gefitinib-resistant lung cancer cells.

Tyrosine kinase inhibitors (TKIs) are mostly used in non-small cell lung cancer (NSCLC) treatment. Unfortunately, treatment with Gefitinib for a period of time will result in drug resistance and cause treatment failure in clinic. Therefore, exploring novel compounds to overcome this resistance is urgently required. Here we investigated the antitumor effect of homoharringtonine (HHT), a natural compound extracted from Cephalotaxus harringtonia, on Gefitinib-resistant NSCLC cell lines in vitro and in vivo. NCI-H1975 cells with EGFR T790M mutation are more sensitive to HHT treatment compared with that of A549 cells with wild type EGFR. HHT inhibited cells growth, cell viability and colony formation, as well as induced cell apoptosis through mitochondria pathway. Furthermore, we explored the mechanism of HHT inhibition on NSCLC cells. Higher level of interleukin-6 (IL-6) existed in lung cancer patients and mutant EGFR and TGFβ signal requires the upregulation of IL-6 through the gp130/JAK pathway to overactive STAT3, an oncogenic protein which has been considered as a potential target for cancer therapy. HHT reversiblely inhibited IL-6-induced STAT3 Tyrosine 705 phosphorylation and reduced anti-apoptotic proteins expression. Gefitinib-resistant NSCLC xenograft tests also confirmed the antitumor effect of HHT in vivo. Consequently, HHT has the potential in Gefitinib-resistant NSCLC treatment.