Acquired resistance to EGFR inhibitors is associated with a manifestation of stem cell-like properties in cancer cells

Cisplatin selects for stem-like cells in osteosarcoma by activating Notch signaling

Notch signaling regulates normal stem cells and is also thought to regulate cancer stem cells (CSCs). Recent data indicate that Notch signaling plays a role in the development and progression of osteosarcoma, however the regulation of Notch in chemo-resistant stem-like cells has not yet been fully elucidated. In this study we generated cisplatin-resistant osteosarcoma cells by treating them with sub-lethal dose of cisplatin, sufficient to induce DNA damage responses. Cisplatin-resistant osteosarcoma cells exhibited lower proliferation, enhanced spheroid formation and more mesenchymal characteristics than cisplatin-sensitive cells, were enriched for Stro-1+/CD117+ cells and showed increased expression of stem cell-related genes. A similar effect was observed in vivo, and in addition in vivo tumorigenicity was enhanced during serial transplantation. Using several publicly available datasets, we identified that Notch expression was closely associated with osteosarcoma stem cells and chemotherapy resistance. We confirmed that cisplatin-induced enrichment of osteosarcoma stem cells was mediated through Notch signaling in vitro, and immunohistochemistry showed that cleaved Notch1 (NICD1) positive cells were significantly increased in a relapsed xenograft which had received cisplatin treatment. Furthermore, pretreatment with a γ-secretase inhibitor (GSI) to prevent Notch signalling inhibited cisplatin-enriched osteosarcoma stem cell activity in vitro, including Stro-1+/CD117+ double positive cells and spheroid formation capacity. The Notch inhibitor DAPT also prevented tumor recurrence in resistant xenograft tumors. Overall, our results show that cisplatin induces the enrichment of osteosarcoma stem-like cells through Notch signaling, and targeted inactivation of Notch may be useful for the elimination of CSCs and overcoming drug resistance.

Concise Review: Resistance to Tyrosine Kinase Inhibitors in Non-Small Cell Lung Cancer: The Role of Cancer Stem Cells

Among the potential mechanisms involved in resistance to tyrosine kinase inhibitors (TKIs) in non-small cell lung cancer, the manifestation of stem-like properties in cancer cells seems to have a crucial role. Alterations involved in the development of TKI resistance may be acquired in a very early phase of tumorigenesis, supporting the hypothesis that these aberrations may be present in cancer stem cells (CSCs). In this regard, the characterization of tumor subclones in the initial phase and the identification of the CSCs may be helpful in planning a specific treatment to target selected biomarkers, suppress tumor growth, and prevent drug resistance. The aim of this review is to elucidate the role of CSCs in the development of resistance to TKIs and its implication for the management of patients. Stem Cells 2018;36:633-640.

Trk inhibition reduces cell proliferation and potentiates the effects of chemotherapeutic agents in Ewing sarcoma

Ewing sarcoma (ES) is a highly aggressive pediatric cancer that may arise from neuronal precursors. Neurotrophins stimulate neuronal devlopment and plasticity. Here, we found that neurotrophins nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF), as well as their receptors (TrkA and TrkB, respectively) are expressed in ES tumors. Treatment with TrkA (GW-441756) or TrkB (Ana-12) selective inhibitors decreased ES cell proliferation, and the effect was increased when the two inhibitors were combined. ES cells treated with a pan-Trk inhibitor, K252a, showed changes in morphology, reduced levels of β-III tubulin, and decreased mRNA expression of NGF, BDNF, TrkA and TrkB. Furthermore, combining K252a with subeffective doses of cytotoxic chemotherapeutic drugs resulted in a decrease in ES cell proliferation and colony formation, even in chemoresistant cells. These results indicate that Trk inhibition may be an emerging approach for the treatment of ES.

TRIB2 contributes to cisplatin resistance in small cell lung cancer

Small cell lung cancer (SCLC) is the most aggressive lung-cancer subtype and so far, no favorable therapeutic strategy has been established for chemo-resistant SCLC. Cisplatin is one of the most important components among all standard poly-chemotherapeutic regimens for SCLC; therefore, this study focused on revealing Cisplatin-resistance mechanism(s) in this disease. Cisplatin-resistant SCLC cells were generated in the NCI-H69 xenograft model in nude mice by continuous intravenous administration of Cisplatin; Cisplatin resistance of the tumor cells was confirmed by in vitro and in vivo tests, and the gene expression profile of the resistant cells was determined using microarray analysis. A significantly higher expression of tribbles pseudokinase 2 (TRIB2) mRNA in the Cisplatin-resistant cells was found compared to parental H69 cells. Further, the Cisplatin-resistance level was decreased when TRIB2 expression was knocked down. The mRNA and protein levels of CCAAT/enhancer binding protein alpha (CEBPA), known to be a transcription factor regulating cell differentiation and a target for degradation by TRIB2, as well as selected cancer stem cell makers in the Cisplatin-resistant cells, were measured. We found that CEBPA protein levels could be upregulated by knocking down the overexpressed TRIB2, which also reversed the Cisplatin-resistance of these cells; further, the Cisplatin-resistant SCLC cells demonstrated certain cancer stem cell-like properties. Similar patterns were also observed in limited human tumor specimens of chemo-resistant SCLC patients: namely, overexpressed TRIB2 and undetected CEBPA proteins. Our study revealed a possible molecular mechanism for Cisplatin-resistant SCLC involving induced TRIB2 overexpression and downregulation of CEBPA protein. We propose that this mechanism is a potential therapeutic target to circumvent chemo-resistance in SCLC.

YAP-Dependent AXL Overexpression Mediates Resistance to EGFR Inhibitors in NSCLC

The Yes-associated protein (YAP) is a transcriptional co-activator upregulating genes that promote cell growth and inhibit apoptosis. The main dysregulation of the Hippo pathway in tumors is due to YAP overexpression, promoting epithelial to mesenchymal transition, cell transformation, and increased metastatic ability. Moreover, it has recently been shown that YAP plays a role in sustaining resistance to targeted therapies as well. In our work, we evaluated the role of YAP in acquired resistance to epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors in lung cancer. In EGFR-addicted lung cancer cell lines (HCC4006 and HCC827) rendered resistant to several EGFR inhibitors, we observed that resistance was associated to YAP activation. Indeed, YAP silencing impaired the maintenance of resistance, while YAP overexpression decreased the responsiveness to EGFR inhibitors in sensitive parental cells. In our models, we identified the AXL tyrosine kinase receptor as the main YAP downstream effector responsible for sustaining YAP-driven resistance: in fact, AXL expression was YAP dependent, and pharmacological or genetic AXL inhibition restored the sensitivity of resistant cells to the anti-EGFR drugs. Notably, YAP overactivation and AXL overexpression were identified in a lung cancer patient upon acquisition of resistance to EGFR TKIs, highlighting the clinical relevance of our in vitro results. The reported data demonstrate that YAP and its downstream target AXL play a crucial role in resistance to EGFR TKIs and suggest that a combined inhibition of EGFR and the YAP/AXL axis could be a good therapeutic option in selected NSCLC patients.

LncRNAs and their role in cancer stem cells

Cancer stem cells (CSCs) play a vital role in the formation of tumors and have been studied as a target of anticancer therapy. Long non-coding RNAs (lncRNAs) are important in the genesis and progression of cancer. Various lncRNAs, such as ROR, HOTAIR, H19, UCA1, and ARSR, are involved in cancer stemness. These lncRNAs could regulate the expression of CSC-related transcriptional factors, such as SOX2, OCT4, and NANOG, in colorectal, prostate, bladder, breast, liver, and other cancer types. In this work, we review the progress of lncRNAs and cancer stem cells and discuss the potential signal pathways of lncRNAs in cancer stemness.

Novel Molecular Challenges in Targeting Anaplastic Lymphoma Kinase in ALK-Expressing Human Cancers

Targeting anaplastic lymphoma kinase (ALK), a receptor tyrosine kinase receptor initially identified as a potent oncogenic driver in anaplastic large-cell lymphoma (ALCL) in the form of nucleophosmin (NPM)-ALK fusion protein, using tyrosine kinase inhibitors has shown to be a promising therapeutic approach for ALK-expressing tumors. However, clinical resistance to ALK inhibitors invariably occurs, and the molecular mechanisms are incompletely understood. Recent studies have clearly shown that clinical resistance to ALK inhibitors is a multifactorial and complex mechanism. While few of the mechanisms of clinical resistance to ALK inhibitors such as gene mutation are well known, there are others that are not well covered. In this review, the molecular mechanisms of cancer stem cells in mediating resistance to ALK inhibitors as well as the current understanding of the molecular challenges in targeting ALK in ALK-expressing human cancers will be discussed.

mAb MDR1-modified chitosan nanoparticles overcome acquired EGFR-TKI resistance through two potential therapeutic targets modulation of MDR1 and autophagy

BACKGROUND

Tyrosine kinase inhibitors (TKIs) that act against the epithelial growth factor receptor (EGFR) were once widely used in chemotherapy for many human cancers. However, acquired chemoresistance occurred in almost all patients, limiting the clinical application of EGFR-TKI. Thus far, no effective methods existing can resolve this problem. Designing a therapeutic treatment with a specific multi-target profile has been regarded as a possible strategy to overcome acquired EGFR-TKI resistance.

METHODS

MDR1 antibody-modified chitosan nanoparticles loading gefitinib and autophagy inhibitor chloroquine were prepared by ionic crosslinking and electrostatic attracting method. MTT assay, flow cytometry analysis and western blot assay were all performed to confirm the effect of different formulations of gefitinib on the proliferation of SMMC-7721/gefitinib cells. The preparations demonstrated their multi-target potential to achieve both tumor-targeting selectivity and the desired antitumor effects by blocking cell-surface MDR1 and inhibiting autophagy.

RESULTS

mAb MDR1-modified CS NPs, when combined with the co-delivery of gefitinib and chloroquine, showed targeting and therapeutic potential on enhancing the delivery of anticancer drugs and inducing significant cell apoptosis against acquired EGFR-TKI resistance through the modulation of autophagy and while blocking the activity of the MDR1 receptor.

CONCLUSIONS

A new approach to design an excellent nanoparticle drug-delivery system can overcome acquired EGFR-TKI resistance against various multiple antitumor targets.

Vorinostat and metformin sensitize EGFR-TKI resistant NSCLC cells via BIM-dependent apoptosis induction

There is a close relationship between low expression of BIM and resistance to epidermal growth factor receptor tyrosine kinase inhibitor (EGFR-TKI). Vorinostat is a pan-histone deacetylase inhibitor (HDACi) that augments BIM expression in various types of tumor cells, however, this effect is attenuated by the high expression of anti-apoptotic proteins in EGFR-TKI resistant non-small cell lung cancer (NSCLC) cells. Vorinostat in combination with metformin - a compound that can inhibit anti-apoptotic proteins expression, might cooperate to activate apoptotic signaling and overcome EGFR-TKI resistance. This study aimed to investigate the cooperative effect and evaluate possible molecular mechanisms. The results showed that vorinostat combined with gefitinib augmented BIM expression and increased the sensitivity of EGFR-TKI resistant NSCLC cells to gefitinib, adding metformin simultaneously could obviously inhibit the expression of anti-apoptotic proteins, and further increased expression levels of BIM and BAX, and as a result, further improved the sensitivity of gefitinib both on the NSCLC cells with intrinsic and acquired resistance to EGFR-TKI. In addition, autophagy induced by gefitinib and vorinostat could be significantly suppressed by metformin, which might also contribute to enhance apoptosis and improve sensitivity of gefitinib. These results suggested that the combination of vorinostat and metformin might represent a novel strategy to overcome EGFR-TKI resistance associated with BIM-dependent apoptosis in larger heterogeneous populations.

Characterization of epithelial-mesenchymal transition intermediate/hybrid phenotypes associated to resistance to EGFR inhibitors in non-small cell lung cancer cell lines

Increasing evidence points to a key role played by epithelial-mesenchymal transition (EMT) in cancer progression and drug resistance. In this study, we used wet and in silico approaches to investigate whether EMT phenotypes are associated to resistance to target therapy in a non-small cell lung cancer model system harboring activating mutations of the epidermal growth factor receptor. The combination of different analysis techniques allowed us to describe intermediate/hybrid and complete EMT phenotypes respectively in HCC827- and HCC4006-derived drug-resistant human cancer cell lines. Interestingly, intermediate/hybrid EMT phenotypes, a collective cell migration and increased stem-like ability associate to resistance to the epidermal growth factor receptor inhibitor, erlotinib, in HCC827 derived cell lines. Moreover, the use of three complementary approaches for gene expression analysis supported the identification of a small EMT-related gene list, which may have otherwise been overlooked by standard stand-alone methods for gene expression analysis.

Acquisition of EGFR TKI resistance and EMT phenotype is linked with activation of IGF1R/NF-κB pathway in EGFR-mutant NSCLC

Epithelial-mesenchymal transition (EMT) is clinically associated with acquired resistance to epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKI) in non-small cell lung cancers (NSCLC). However, the mechanisms promoting EMT in EGFR TKI-resistant NSCLC have not been fully elucidated. Previous studies have suggested that IGF1R signaling is involved in both acquired EGFR TKI resistance in NSCLC and induction of EMT in some types of tumor. In this study, we further explored the role of the IGF1R signaling in the acquisition of EMT phenotype associated with EGFR TKI resistance in mutant-EGFR NSCLC. Compared to gefitinib-sensitive parental cells, gefitinib-resistant (GR) cells displayed an EMT phenotype associated with increased migration and invasion abilities with the concomitant activation of IGF1R and NF-κB p65 signaling. Inhibition of IGF1R or p65 using pharmacological inhibitor or specific siRNA partially restored sensitivity to gefitinib with the concomitant reversal of EMT in GR cells. Conversely, exogenous IGF1 induced both gefitinib resistance and accompanying EMT in parental cells. We also demonstrated that IGF1R could phosphorylate downstream Akt and Erk to activate NF-κB p65. Taken together, our findings indicate that activation of IGF1R/Akt/Erk/NF-κB signaling is linked to the acquisition of EGFR TKI resistance and EMT phenotype in EGFR-mutant NSCLC and could be a novel therapeutic target for advanced NSCLC.

Establishing Dual Resistance to EGFR-TKI and MET-TKI in Lung Adenocarcinoma Cells In Vitro with a 2-step Dose-escalation Procedure

Drug resistance is a major challenge in cancer therapy. The generation of resistant sublines in vitro is necessary for discovering novel mechanisms to overcome this challenge. Here, a 2-step dose-escalation method for establishing dual-resistance to an epidermal growth factor receptor (EGFR)-tyrosine kinase inhibitor (TKI), gefitinib, and a MET-TKI, PHA665752, is described. This method is based on simple stepwise dose-escalation of inhibitors for inducing acquired resistance in cell lines. The alternate method for generating resistant sublines involves exposing the cells to high concentrations of the inhibitor in one step. The stepwise dose-escalation method has a higher possibility of successfully inducing acquired resistance than this method. Activating EGFR mutations are biomarkers of a response to treatment with EGFR-TKI, which is an applied first-line treatment for non-small cell lung cancers (NSCLC) that harbor these mutations. However, despite reports of effective responses, the use of EGFR-TKI is limited because tumors inevitably acquire resistance. The major mechanisms behind EGFR-TKI resistance include a secondary mutation at the gatekeeper site, T790M in exon 20 of EGFR, and a bypass signal of MET. Thus, a potential solution for this issue would be a combination of EGFR-TKI and MET-TKI. This combined treatment has been shown to be effective in an in vitro study model. Acquired gefitinib-resistance was established through MET-amplification by stepwise dose-escalation of gefitinib for 12 months, and a cell line named PC-9MET1000 was generated in a previous study. To further investigate the mechanisms of acquired MET-TKI and EGFR-TKI resistance, a MET-TKI, PHA665752, was administered to these cells with stepwise dose-escalation in the presence of gefitinib for 12 months. This protocol has also been successfully applied for a number of combination therapies to establish acquired resistance to other inhibitor molecules.

Blockade of Stearoyl-CoA-desaturase 1 activity reverts resistance to cisplatin in lung cancer stem cells

Poor prognosis in lung cancer has been attributed to the presence of lung cancer stem cells (CSCs) which resist chemotherapy and cause disease recurrence. Hence, the strong need to identify mechanisms of chemoresistance and to develop new combination therapies. We have previously shown that Stearoyl-CoA-desaturase 1 (SCD1), the enzyme responsible for the conversion of saturated to monounsaturated fatty acids is upregulated in 3D lung cancer spheroids and is an upstream activator of key proliferation pathways β-catenin and YAP/TAZ. Here we first show that SCD1 expression, either alone or in combination with a variety of CSCs markers, correlates with poor prognosis in adenocarcinoma (ADC) of the lung. Treatment of lung ADC cell cultures with cisplatin enhances the formation of larger 3D tumor spheroids and upregulates CSCs markers. In contrast, co-treatment with cisplatin and the SCD1 inhibitor MF-438 reverts upregulation of CSCs markers, strongly synergizes in the inhibition of 3D spheroids formation and induces CSCs apoptosis. Mechanistically, SCD1 inhibition activates endoplasmic reticulum stress response and enhances autophagy. These data all together support the use of combination therapy with SCD1 inhibitors to achieve better control of lung cancer.

Epithelial-to-Mesenchymal Transition and MicroRNAs in Lung Cancer

Despite major advances, non-small cell lung cancer (NSCLC) remains the major cause of cancer-related death in developed countries. Metastasis and drug resistance are the main factors contributing to relapse and death. Epithelial-to-mesenchymal transition (EMT) is a complex molecular and cellular process involved in tissue remodelling that was extensively studied as an actor of tumour progression, metastasis and drug resistance in many cancer types and in lung cancers. Here we described with an emphasis on NSCLC how the changes in signalling pathways, transcription factors expression or microRNAs that occur in cancer promote EMT. Understanding the biology of EMT will help to define reversing process and treatment strategies. We will see that this complex mechanism is related to inflammation, cell mobility and stem cell features and that it is a dynamic process. The existence of intermediate phenotypes and tumour heterogeneity may be debated in the literature concerning EMT markers, EMT signatures and clinical consequences in NSCLC. However, given the role of EMT in metastasis and in drug resistance the development of EMT inhibitors is an interesting approach to counteract tumour progression and drug resistance. This review describes EMT involvement in cancer with an emphasis on NSCLC and microRNA regulation.

Elacridar, a third-generation ABCB1 inhibitor, overcomes resistance to docetaxel in non-small cell lung cancer

Docetaxel is a third-generation chemotherapeutic drug that is widely used in the treatment of patients with non-small cell lung cancer (NSCLC). However, the majority of patients with NSCLC eventually acquire resistance to the treatment. In the present study, the mechanism of acquired resistance to docetaxel treatment in lung cancer cells was investigated. The three NSCLC cell lines, H1299 with wild-type epidermal growth factor receptor (EGFR), EGFR-mutant HCC4006 and HCC827, and experimentally established docetaxel-resistant (DR) cells, H1299-DR, HCC827-DR, and HCC4006-DR were used with stepwise increases in concentrations of docetaxel. It was demonstrated that the established cell lines showed resistance to docetaxel and EGFR-tyrosine kinase inhibitors (TKIs). Molecular analysis revealed that all of the resistant cell lines highly expressed ATP binding cassette subfamily B member 1 (ABCB1), which is also known as P-glycoprotein or MDR1. Furthermore, HCC827-DR and HCC4006-DR cells exhibited a cancer stem cell-like marker and epithelial-to-mesenchymal transition features, respectively. Elacridar (GF120918), a third-generation inhibitor of ABCB1, was able to overcome resistance to docetaxel. Additionally, knockdown of ABCB1 using small interfering RNA (si)-ABCB1 recovered sensitivity to docetaxel. However, elacridar and si-ABCB1 could not recover sensitivity to EGFR-TKIs in established resistant cells. The results of the present study revealed that docetaxel-resistant NSCLC cells also acquired cross-resistance to EGFR-TKI therapy through mechanisms other than ABCB1, that ABCB1 serves an important role in acquired resistance to docetaxel in lung cancer, and that combination therapy with elacridar can overcome ABCB1-mediated docetaxel resistance.

JAK1/STAT3 Activation through a Proinflammatory Cytokine Pathway Leads to Resistance to Molecularly Targeted Therapy in Non-Small Cell Lung Cancer

Molecularly targeted drugs have yielded significant therapeutic advances in oncogene-driven non-small cell lung cancer (NSCLC), but a majority of patients eventually develop acquired resistance. Recently, the relation between proinflammatory cytokine IL6 and resistance to targeted drugs has been reported. We investigated the functional contribution of IL6 and the other members of IL6 family proinflammatory cytokine pathway to resistance to targeted drugs in NSCLC cells. In addition, we examined the production of these cytokines by cancer cells and cancer-associated fibroblasts (CAF). We also analyzed the prognostic significance of these molecule expressions in clinical NSCLC samples. In NSCLC cells with acquired resistance to targeted drugs, we observed activation of the IL6-cytokine pathway and STAT3 along with epithelial-to-mesenchymal transition (EMT) features. In particular, IL6 family cytokine oncostatin-M (OSM) induced a switch to the EMT phenotype and protected cells from targeted drug-induced apoptosis in OSM receptors (OSMRs)/JAK1/STAT3-dependent manner. The cross-talk between NSCLC cells and CAFs also preferentially activated the OSM/STAT3 pathway via a paracrine mechanism and decreased sensitivity to targeted drugs. The selective JAK1 inhibitor filgotinib effectively suppressed STAT3 activation and OSMR expression, and cotargeting inhibition of the oncogenic pathway and JAK1 reversed resistance to targeted drugs. In the analysis of clinical samples, OSMR gene expression appeared to be associated with worse prognosis in patients with surgically resected lung adenocarcinoma. Our data suggest that the OSMRs/JAK1/STAT3 axis contributes to resistance to targeted drugs in oncogene-driven NSCLC cells, implying that this pathway could be a therapeutic target. Mol Cancer Ther; 16(10); 2234-45. ©2017 AACR.

Overcoming resistance to EGFR tyrosine kinase inhibitors in lung cancer, focusing on non-T790M mechanisms

INTRODUCTION

despite initial dramatic efficacy of EGFR tyrosine kinase inhibitors (TKIs) in EGFR-mutant lung cancer patients, emergence of acquired resistance is almost inevitable. The EGFR T790M secondary mutation that accounts for ~50% of resistance is now treatable with osimertinib. However, for the remaining 50% of patients who develop resistance mechanisms other than T790M mutation, cytotoxic chemotherapies are still the standard of care and novel treatment strategies are urgently needed. Areas covered: In this review, we discuss current experimental and clinical evidence to develop better treatment strategies to overcome or prevent acquired resistance to EGFR-TKIs in lung cancers, focusing on non-T790M mechanisms. Expert commentary: There are numerous non-T790M resistant mechanisms to EGFR-TKIs, and therefore, strategies that can be applied to many of these resistance mechanisms may be reasonable and useful in clinical practice. Although the combination of cytotoxic chemotherapy plus an EGFR-TKI has proved to be detrimental following front-line EGFR-TKI treatment failure, promising experimental and/or early clinical data have been reported for the combination of bevacizumab or anti-EGFR monoclonal antibody plus EGFR-TKIs. Upfront polytherapy, which co-targets potential resistance mechanisms or other important signaling for EGFR-mutant lung cancer cells, is also a promising strategy.

Roles of Grainyhead-like transcription factors in cancer

The mammalian homologs of the D. melanogaster Grainyhead gene, Grainyhead-like 1-3 (GRHL1, GRHL2 and GRHL3), are transcription factors implicated in wound healing, tubulogenesis and cancer. Their induced target genes encode diverse epithelial cell adhesion molecules, while mesenchymal genes involved in cell migration and invasion are repressed. Moreover, GRHL2 suppresses the oncogenic epithelial-mesencyhmal transition, thereby acting as a tumor suppressor. Mechanisms, some involving established cancer-related signaling/transcription factor pathways (for example, Wnt, TGF-β, mir200, ZEB1, OVOL2, p63 and p300) and translational implications of the Grainyhead proteins in cancer are discussed in this review article.

HER2 regulates cancer stem-like cell phenotype in ALK translocated NSCLC

We have previously shown that cancer stem-like cells (CSLCs) can mediate therapy resistance in ALK translocated lung cancers. HER2 has been linked to CSLCs in breast cancers and, therefore, we wanted to assess whether HER2 has a role in CSLCs in ALK translocated cancers. ALK translocated cell lines, H3122 and H2228, with variable sensitivity to ALK inhibition were used in the study. HER2 overexpression or knockdown was induced by retro- or lentiviral infections and cells were treated with pharmacological agents targeting HER2 and ALK signaling. Furthermore, tumorigenic properties of the cells were assessed in vitro using colony and sphere formation assays. In the ALK inhibitor sensitive H3122 cells, HER2 overexpression unaltered the primary response to ALK inhibition, but increased CSLC marker expression and enhanced colony and sphere formation and late AKT and ERK1/2 signaling recovery. In the ALK inhibitor semi-sensitive H2228 cells, HER2 knockdown reduced basal expression of CSLC markers, modestly increased sensitivity to ALK inhibition in colony and sphere formation assays, and reduced late AKT and ERK1/2 signaling recovery. In addition, HER2 induced cross activation of other ErbB-members of which HER3 followed most closely the CSLC marker expression and neuregulin-1, a HER3 ligand, or pan-ErbB inhibitor afatinib, were able to alter CSLC marker expression and colony formation. the present study suggests that HER2 has an important role in the regulation of the CSLC phenotype in ALK translocated lung cancers that is mainly orchestrated by HER2/HER3 heterodimers.

Glucose metabolism-targeted therapy and withaferin A are effective for epidermal growth factor receptor tyrosine kinase inhibitor-induced drug-tolerant persisters

In pathway‐targeted cancer drug therapies, the relatively rapid emergence of drug‐tolerant persisters (DTPs) substantially limits the overall therapeutic benefit. However, little is known about the roles of DTPs in drug resistance. In this study, we investigated the features of epidermal growth factor receptor–tyrosine kinase inhibitor‐induced DTPs and explored a new treatment strategy to overcome the emergence of these DTPs. We used two EGFR‐mutated lung adenocarcinoma cell lines, PC9 and II‐18. They were treated with 2 μM gefitinib for 6, 12, or 24 days or 6 months. We analyzed the mRNA expression of the stem cell‐related markers by quantitative RT‐PCR and the expression of the cellular senescence‐associated proteins. Then we sorted DTPs according to the expression pattern of CD133 and analyzed the features of sorted cells. Finally, we tried to ablate DTPs by glucose metabolism targeting therapies and a stem‐like cell targeting drug, withaferin A. Drug‐tolerant persisters were composed of at least two types of cells, one with the properties of cancer stem‐like cells (CSCs) and the other with the properties of therapy‐induced senescent (TIS) cells. The CD133^high cell population had CSC properties and the CD133^low cell population had TIS properties. The CD133^low cell population containing TIS cells showed a senescence‐associated secretory phenotype that supported the emergence of the CD133^high cell population containing CSCs. Glucose metabolism inhibitors effectively eliminated the CD133^low cell population. Withaferin A effectively eliminated the CD133^high cell population. The combination of phloretin and withaferin A effectively suppressed gefitinib‐resistant tumor growth.

Prognostic significance of ABCB1 in stage I lung adenocarcinoma

Cancer stem cell (CSC) properties have been recently proposed to explain tumor carcinogenesis and multidrug resistance in several human cancers, including non-small cell lung cancer (NSCLC). The present study examined the protein expression of three CSC-associated markers, namely ATP binding cassette subfamily B member 1 (ABCB1), aldehyde dehydrogenase 1 family member A1 (ALDH1A1) and cluster of differentiation (CD) 44, by immunohistochemistry in 194 NSCLC patients who underwent complete resection of NSCLC tumors. The association between the expression of these proteins and patient prognosis was evaluated to clarify the prognostic significance of CSC-associated markers in NSCLC patients. Positive staining for ABCB1 demonstrated a trend toward worse survival compared with negative staining in stage I-III NSCLC. Negative staining for ALDH1 or CD44 exhibited a trend toward worse survival compared with positive staining in stage I-III NSCLC. It was observed that patients with stage I lung adenocarcinoma (ADC) showing positivity for ABCB1 expression had significantly poorer survival than those with negative ABCB1 staining (P=0.03). Furthermore, stage I ADC patients with wild-type epidermal growth factor receptor (EGFR) who exhibited positive staining for ABCB1 had significantly shorter disease-free survival (DFS) compared with patients with negative staining for ABCB1 (P<0.01). Analyses by univariate and multivariate Cox proportional hazards models revealed that ABCB1-positive staining was significantly associated with DFS and was an independent prognostic factor (hazard ratio, 3.49; P<0.05) in these patients. These results suggest that ABCB1 protein expression is useful for predicting prognosis and selecting patients for post-operative therapy in stage I lung ADC patients, particularly those harboring wild-type EGFR.

Therapy-induced E-cadherin downregulation alters expression of programmed death ligand-1 in lung cancer cells

OBJECTIVES

Immunotherapy that targets the programmed death-1/programmed death-ligand 1 (PD-L1) axis has been approved for treatment of non-small cell lung cancer (NSCLC) patients in many countries. However, our current understanding of the role of immunotherapies on NSCLC patients with epidermal growth factor receptor (EGFR) mutation, following acquisition of resistance to EGFR tyrosine kinase inhibitors (TKIs), is so far unclear. Especially, there is little data on if each acquired resistance mechanism to EGFR-TKIs alters PD-L1 expression status which is employed as an important predictive biomarker for PD-1/PD-L1 targeting agents.

MATERIALS AND METHODS

Lung cancer cell lines (HCC827, HCC4006, PC9, H1975, H358, SW900, and H647) and their daughter cells that acquired resistance to EGFR-TKIs or cytotoxic drugs (cisplatin or vinorelbine) were examined. PD-L1 expression was analyzed by immunohistochemistry, immunoblotting, and/or fluorescent imaging. Published microarray data were also employed to evaluate our findings.

RESULTS AND CONCLUSION

We found correlations between therapy-induced E-cadherin downregulation and decreased PD-L1 expression using our cell lines and published microarray data. ShRNA mediated E-cadherin knockdown decreased PD-L1 expression in parental cells, and dual immunofluorescent staining of E-cadherin and PD-L1 suggests co-localization of both molecules. We also observed marked downregulation of PD-L1 in cells with E-cadherin downregulation after chronic treatment with vinorelbine. These results indicate a correlation between therapy-induced E-cadherin downregulation and decreased PD-L1 expression, highlighting the importance of re-biopsy after acquisition of resistance to EGFR-TKIs, not only for the evaluation of resistance mechanisms but also for the determination of PD-L1 expression status.

MET amplification and epithelial-to-mesenchymal transition exist as parallel resistance mechanisms in erlotinib-resistant, EGFR-mutated, NSCLC HCC827 cells

Although many epidermal growth factor receptor (EGFR)-mutated lung cancer patients initially benefit from the EGFR-inhibitor erlotinib, all acquire resistance. So far, several mechanisms implicated in resistance have been identified, but the existence of multiple resistance mechanisms in parallel have only been sparsely investigated. In this study, we investigated parallel resistance mechanisms acquired by HCC827, an EGFR-mutated adenocarcinoma cell line dependent on EGFR activity and sensitive to erlotinib. The cell line was treated with erlotinib by stepwise escalation of the drug-concentration and erlotinib-resistant (HCC827ER) cells created. HCC827ER cells depicted a mixed epithelial and mesenchymal phenotype. To clarify potential parallel resistance mechanisms, 14 resistant subclones were established by limited dilution. Interestingly, all HCC827ER subclones harbored either a MET-amplification (6/14) or underwent EMT (8/14), mechanisms both found in previous studies, but not in co-occurrence. Both subclone-types were resistant to erlotinib, but only MET-subclones responded to the MET-inhibitors crizotinib and capmatinib. EMT-subclones on the other hand had markedly increased FGFR1 expression and responded to the FGFR-inhibitor AZD4547, whereas MET-subclones did not. Monitoring gene expression through the development of HCC827ER revealed upregulation of FGFR1 expression as an early response to erlotinib. In addition, FGFR1 expression increased upon short-term erlotinib treatment (48 h) identifying a physiological role immediately after erlotinib exposure. The high FGFR1 expression seen in EMT-subclones was stable even after five passages without erlotinib. Here we show, that parallel resistance mechanisms appear during erlotinib-resistance development in EGFR-mutated NSCLC cells and highlight a role for FGFR1 expression changes as an early response to erlotinib as well as a bypass-signaling mechanism.

Decitabine reverses TGF-β1-induced epithelial-mesenchymal transition in non-small-cell lung cancer by regulating miR-200/ZEB axis

OBJECTIVE

Epithelial-mesenchymal transition (EMT) is a crucial driver of tumor progression. Tumor growth factor-beta 1 (TGF-β1) is an important factor in EMT induction in tumorigenesis. The targeting of EMT may, therefore, represent a promising approach in anticancer treatment.

METHODS

In this study, we determined the effect of decitabine, a DNA methyltransferase inhibitor, on TGF-β1-induced EMT in non-small-cell lung cancer (NSCLC) PC9 and A549 cells. We also assessed the involvement of the miR-200/ZEB axis.

RESULTS

Decitabine reversed TGF-β1-induced EMT in PC9 cells, but not in A549 cells. This phenomenon was associated with epigenetic changes in the miR-200 family, which regulated EMT by altering the expression of ZEB1 and ZEB2. TGF-β1 induced aberrant methylation in miR-200 promoters, leading to EMT in PC9 cells. Decitabine attenuated this effect and inhibited tumor cell migration in vitro and in vivo. In A549 cells, however, neither TGF-β1 nor decitabine exhibited an effect on miR-200 promoter methylation.

CONCLUSION

Our findings suggest that epigenetic regulation of the miR-200/ZEB axis is responsible for EMT induction by TGF-β1 in PC9 cells. Decitabine inhibits EMT in NSCLC cell PC9 through its epigenetic-based therapeutic activity.

Current FDA-approved treatments for non-small cell lung cancer and potential biomarkers for its detection

BACKGROUND

Lung cancer is the leading worldwide cancer with almost 1.5 million deaths every year. Some drugs for lung cancer treatment have been available on the market for decades, but novel drugs have emerged promising better outcomes, especially for Non-Small Cell Lung Cancer (NSCLC), which represents 75% of lung cancer cases. However, how much do drugs have evolved for NSCLC treatment? Are they sharing the same mechanism of action?

AIM

In this review we analyzed how the approved drugs by Federal Drug Agency for NSCLC have advanced in the last four decades identifying shared mechanism of action of medicines against NSCLC treatment and some of the potential biomarkers for early detection.

RESULTS

Cisplatin and its derivatives are still the most used therapy in combination with some other more specific drugs. However, increasing the survival rates seems to be a great challenge and research is moving into early detection through biomarkers but also trying to identify molecules such as those derived from the immune system, cell-free DNA, non-coding RNAs, but also polymorphisms to detect early tumor formation.

CONCLUSIONS

Cisplatin and derivatives have been one of the most successful therapies in spite of their side effects and low specificity. Some of the drugs developed after cisplatin discovery, have been targeted the epidermal growth factor receptor, anaplastic lymphoma kinase, programmed cell death 1 ligand and vascular endothelial growth factor. Since none of the pharmacological treatments in combination with radiation/surgery have extended dramatically the survival rate, research is now focused in early cancer detection in combination with precision medicine, which attempts to treat patients individually according to their stage and tumor characteristics.

Antagonism of EGFR and Notch limits resistance to EGFR inhibitors and radiation by decreasing tumor-initiating cell frequency

Epidermal growth factor receptor (EGFR) blockade and radiation are efficacious in the treatment of cancer, but resistance is commonly reported. Studies have suggested that dysregulation of Notch signaling and enrichment of the cancer stem cell population underlie these treatment challenges. Our data show that dual targeting of EGFR and Notch2/3 receptors with antibody CT16 not only inhibited signaling mediated by these receptors but also showed a strong anti-stem cell effect both in vitro and in vivo. Treatment with CT16 prevented acquired resistance to EGFR inhibitors and radiation in non-small cell lung cancer (NSCLC) cell line models and patient-derived xenograft tumors. CT16 also had a superior radiosensitizing impact compared with EGFR inhibitors. CT16 in combination with radiation had a larger antitumor effect than the combination of radiation with EGFR inhibitors or tarextumab. Mechanistically, CT16 treatment inhibits the stem cell-like subpopulation, which has a high mesenchymal gene expression and DNA repair activity, and reduces tumor-initiating cell frequency. This finding highlights the capacity of a combined blockade of EGFR and Notch signaling to augment the response to radiation and suggests that CT16 may achieve clinical efficacy when combined with radiation in NSCLC treatment.

Brother of the regulator of the imprinted site (BORIS) variant subfamily 6 is a novel target of lung cancer stem-like cell immunotherapy

Lung cancer is one of the most common malignancies with a high rate of mortality. Lung cancer stem-like cells (CSCs)/ cancer-initiating cells (CICs) play major role in resistance to treatments, recurrence and distant metastasis and eradication of CSCs/CICs is crucial to improve recent therapy. Cytotoxic T lymphocytes (CTLs) are major effectors of cancer immunotherapy, and CTLs recognize antigenic peptides derived from antigens that are presented by major histocompatibility complex (MHC) class I molecules. In this study, we analyzed the potency of a cancer-testis (CT) antigen, brother of the regulator of the imprinted site variant subfamily 6 (BORIS sf6), in lung CSC/CIC immunotherapy. BORIS sf6 mRNA was expressed in lung carcinoma cells (9/19), especially in sphere-cultured lung cancer stem-like cells, and in primary lung carcinoma tissues (4/9) by RT-PCR. Immunohistochemical staining using BORIS sf6-specific antibody revealed that high expression of BORIS sf6 is related to poorer prognosis. CTLs could be induced by using a human leukocyte antigen, (HLA)-A2 restricted antigenic peptide (BORIS C34_24(9)), from all of 3 HLA-A2-positive individuals, and CTL clone cells specific for BORIS C34_24(9) peptide could recognize BORIS sf6-positive, HLA-A2-positive lung carcinoma cells. These results indicate that BORIS sf6 is a novel target of lung cancer immunotherapy that might be useful for targeting treatment-resistant lung cancer stem-like cells.

Most T790M mutations are present on the same EGFR allele as activating mutations in patients with non-small cell lung cancer

OBJECTIVES

The T790M and C797S mutations of the epidermal growth factor receptor gene (EGFR) confer resistance to first- and third-generation EGFR tyrosine kinase inhibitors (TKIs), respectively, in patients with non-small cell lung cancer (NSCLC) harboring activating mutations of EGFR. C797S has been identified in cis or in trans with T790M in tumor specimens from patients who experienced treatment failure with first- and third-generation EGFR-TKIs. The allelic relation between T790M and activating mutations of EGFR has not been well characterized, however. We have now developed a digital polymerase chain reaction (dPCR)-based method for determination of the allelic relation between two types of EGFR mutation (T790M and either C797S or an activating mutation).

MATERIALS AND METHODS

Seven clinical NSCLC specimens and two NSCLC cell lines harboring both an activating mutation and T790M were analyzed with this new method to identify the allelic relation between these EGFR mutations.

RESULTS

The median ratio of the number of alleles positive for both an activating mutation and T790M to the number of T790M-positive alleles was 97.1% (range, 90.0-100%). Confirmatory analysis by next-generation sequencing yielded a corresponding value of 96.7% (range, 89.1-99.5%). Our dPCR method thus reliably identifies the allelic relation between two EGFR mutations in a quantitative manner.

CONCLUSIONS

Almost all T790M mutations were detected in cis with activating mutations of EGFR regardless of the de novo or acquired status of T790M, with cancer cells harboring T790M and activating mutations on the same allele appearing to be selected and enriched during EGFR-TKI treatment.

Yes1 signaling mediates the resistance to Trastuzumab/Lap atinib in breast cancer

Background

Overexpression of human epidermal growth factor receptor 2 (HER2) is observed in approximately 15–23% of breast cancers and these cancers are classified as HER2-positive breast cancer. Trastuzumab is the first-line targeted therapeutic drug for HER2-positive breast cancer and has improved patient overall survival. However, acquired resistance to trastuzumab is still a critical issue in breast cancer treatment. We previously established a trastuzumab-resistant breast cancer cell line (named as BT-474-R) from a trastuzumab-sensitive HER2-amplified cell line BT-474. Lapatinib is also a molecular-targeted drug for HER2-positive breast cancer, which acquired the resistance to trastuzumab. Acquired resistance to lapatinib is also an issue to be conquered.

Methods

We established trastuzumab/lapatinib-dual resistant cell line (named as BT-474-RL2) by additionally treating BT-474-R with lapatinib. We analyzed the mechanisms of resistance to trastuzumab and lapatinib. Besides, we analyzed the effect of the detected resistance mechanism in HER2-positive breast cancer patients.

Results

Proto-oncogene tyrosine-protein kinase Yes1, which is one of the Src family members, was amplified, overexpressed and activated in BT-474-R and BT-474-RL2. Silencing of Yes1 by siRNA induced both BT-474-R and BT-474-RL2 to restore the sensitivity to trastuzumab and lapatinib. Pharmaceutical inhibition of Yes1 by the Src inhibitor dasatinib was also effective to restore the sensitivity to trastuzumab and lapatinib in the two resistant cell lines. Combination treatment with dasatinib and trastuzumab induced down-regulation of signaling molecules such as HER2 and Akt. Moreover, the combination treatments induced G1-phase cell-cycle arrest and apoptosis. Consistent with cell line data, high expression of Yes1 mRNA was correlated with worse prognosis in patients with HER2-positive breast cancer.

Conclusion

Yes1 plays an important role in acquired resistance to trastuzumab and lapatinib in HER2-positive breast cancer. Our data suggest that pharmacological inhibition of Yes1 may be an effective strategy to overcome resistance to trastuzumab and lapatinib.

Targeting the miR-200c/LIN28B axis in acquired EGFR-TKI resistance non-small cell lung cancer cells harboring EMT features

MicroRNA (miR)-200 family members (miR-200s) are frequently silenced in advanced cancer and have been implicated in the process of epithelial-to-mesenchymal transition (EMT). We previously reported that miR-200s were silenced through promoter methylation in acquired EGFR-tyrosine kinase inhibitor (TKI) resistant non-small cell lung cancer (NSCLC) cells harboring EMT features. In this study, we examined the functional role of miR-200s in NSCLC cells and investigated a novel approach to overcoming acquired EGFR-TKI resistance. In the analysis of NSCLC cell lines, each of the miR-200s expression-silenced cell lines showed promoter methylation. Significant correlations between miR-200c silencing and several oncogenic pathway alterations, including EMT-changes and LIN28B overexpression, were observed in the database analysis. In addition, EGFR-wild type cell lines had lower miR-200s expression levels than EGFR-mutant cell lines. The introduction of miR-200c using pre-miR-200c caused LIN28B suppression in cells with acquired EGFR-TKI resistance that harbored EMT features. Interestingly, both the introduction of miR-200c and the knockdown of LIN28B produced an antitumor effect in acquired EGFR-TKI resistance cells, whereas these manipulations were not effective in parental cells. The miR-200c/LIN28B axis plays an important role in cells with acquired resistance to EGFR-TKI that harbor EMT features and might be a useful therapeutic target for overcoming resistance.

Histological Transformation to Large Cell Neuroendocrine Carcinoma from Lung Adenocarcinoma Harboring an EGFR Mutation: An Autopsy Case Report

We herein report a 58-year-old Japanese woman who survived 14 years after surgery for lung adenocarcinoma harboring an epidermal growth factor receptor (EGFR) exon 19 deletion. She developed recurrence, for which she underwent multimodal therapy, including EGFR-tyrosine kinase inhibitor (TKI) administration. She ultimately died from a rapidly progressive right lung tumor that was resistant to EGFR-TKI. According to the autopsy findings, she had combined large-cell neuroendocrine carcinoma (LCNEC) and adenocarcinoma in the right lung, which retained an EGFR exon 19 deletion in both components. Therefore, the histological transformation to LCNEC can be a mechanism of acquired EGFR-TKI resistance.

Interaction of cytokeratin 19 head domain and HER2 in the cytoplasm leads to activation of HER2-Erk pathway

HER2 is a receptor tyrosine kinase and its upregulation via activating mutations or amplification has been identified in some malignant tumors, including lung cancers. Because HER2 can be a therapeutic target in HER2-driven malignancies, it is important to understand the molecular mechanisms of HER2 activation. In the current study, we identified that cytokeratin 19 (KRT19) binds to HER2 at the inside face of plasma membrane. HER2 and KRT19, which were concurrently introduced to a human embryonic kidney 293 T cells, revealed an association with each other and resulted in phosphorylation of HER2 with the subsequent activation of a downstream Erk-associated pathway. A binding assay revealed that both the NH2-terminal head domain of KRT19 and the COOH-terminal domain of HER2 were essential for their binding. To investigate the impact of the interaction between HER2 and KRT19 in lung cancer, we examined their expressions and localizations in lung cancers. We found that KRT19 was highly expressed in HER2-positive lung cancer cells, and KRT19 and HER2 were co-localized at the cell membrane. In conclusion, we found that KRT19 intracellularly binds to HER2, playing a critical role in HER2 activation.

Effect of dasatinib on EMT-mediated-mechanism of resistance against EGFR inhibitors in lung cancer cells

OBJECTIVE

The epithelial to mesenchymal transition (EMT) is associated with acquired resistance to epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) in certain non-small cell lung cancers that harbor EGFR mutations. Because no currently available drugs specifically kill cancer cells via EMT, novel treatment strategies that overcome or prevent EMT are needed. A recent report suggested that dasatinib (an ABL/Src kinase inhibitor) inhibits EMT induced by transforming growth factor (TGF)-beta in lung cancer cells (Wilson et al., 2014). In this study, we analyzed effects of dasatinib on the resistance mechanism in HCC4006 cells, which tend to acquire resistance to EGFR-TKIs via EMT.

MATERIALS AND METHODS

Sensitivity to dasatinib in HCC4006 and HCC4006 erlotinib-resistant (ER) cells with an EMT phenotype was analyzed. HCC4006 cells acquired resistance against the combination of erlotinib and dasatinib (HCC4006EDR) following chronic treatment with these drugs. The expression of EMT markers and the resistance mechanism were analyzed.

RESULTS

Short-term or long-term treatment with dasatinib did not reverse EMT in HCC4006ER. In contrast, HCC4006EDR cells maintained an epithelial phenotype, and the mechanism underlying resistance to erlotinib plus dasatinib combination therapy was attributable to a T790M secondary mutation. HCC4006EDR cells, but not HCC4006ER cells, were highly sensitive to a third-generation EGFR-TKI, osimertinib.

CONCLUSIONS

Although dasatinib monotherapy did not reverse EMT in HCC4006ER cells, preemptive combination treatment with erlotinib and dasatinib prevented the emergence of acquired resistance via EMT, and led to the emergence of T790M. Our results indicate that preemptive combination therapy may be a promising strategy to prevent the emergence of EMT-mediated resistance.

miR-25-3p reverses epithelial-mesenchymal transition via targeting Sema4C in cisplatin-resistance cervical cancer cells

Acquisition of epithelial-mesenchymal transition (EMT) has recently been proposed as an important contributor of drug resistance in cervical cancer cells. However, the underlying mechanisms are still unclear. MicroRNAs play a crucial role in regulating EMT. The aim of this study was to explore the potential role of miR-25-3p in regulating EMT in cisplatin-resistant (CR) cervical cancer cells. To this end, we established stable CR cervical cancer cells, HeLa-CR and CaSki-CR, and investigated the function of miR-25-3p in regulating EMT. It is found that CR cervical cancer cells possessed more EMT characteristics and demonstrated higher migratory abilities and invasiveness. miR-25-3p downregulation was also seen in HeLa-CR and CaSki-CR cells. Of note, ectopic expression of miR-25-3p reversed the EMT phenotype and sensitized CR cells to cisplatin via targeting Sema4C. Furthermore, stable overexpression of miR-25-3p in HeLa-CR cells suppressed tumor growth in mice, downregulated Sema4C and Snail, and upregulated E-cadherin compared with the control group. These results suggest that miR-25-3p is an important regulator of cervical cancer EMT and chemoresistance. Thus, upregulation of miR-25-3p could be a novel approach to treat cervical cancers that are resistant to chemotherapy.

A feed-forward loop between lncARSR and YAP activity promotes expansion of renal tumour-initiating cells

Renal tumour-initiating cells (T-ICs) contribute to tumorigenesis, progression and drug resistance of renal cell carcinoma (RCC). However, the underlying mechanism for the propagation of renal T-ICs remains unclear. Here we show that long non-coding RNA lncARSR is upregulated in primary renal T-ICs and associated with a poor prognosis of clear cell RCCs (ccRCC). Knockdown of lncARSR attenuates the self-renewal, tumorigenicity and metastasis of renal T-ICs. Conversely, forced lncARSR expression enhances T-IC properties of RCC cells. Mechanistically, the binding of lncARSR to YAP impedes LATS1-induced YAP phosphorylation and facilitates YAP nuclear translocation. Reciprocally, YAP/TEAD promotes lncARSR transcription, thus forming a feed-forward circuit. The correlation between lncARSR and YAP is validated in a ccRCC cohort, where the combination of these two parameters exhibits improved prognostic accuracy. Our findings indicate that lncARSR plays a critical role in renal T-ICs propagation and may serve as a prognostic biomarker and potential therapeutic target.

Renal tumour-initiating cells (T-ICs) contribute to tumour initiation and progression. Here, the authors show that lncARSR regulates TICs by blocking LATS1-induced YAP phosphorylation facilitating YAP nuclear translocation, which promotes lncARSR transcription, thus forming a feed-forward circuit to promote TIC expansion.

miR-127 promotes EMT and stem-like traits in lung cancer through a feed-forward regulatory loop

The coordination between cellular differentiation and the mesenchymal/stem transition is essential for both embryo development and neoplasia, suggesting a mechanistic link between these two major processes. In this work we show that miR-127, an embryo-expressing lung miRNA, was prominently induced in lung adenocarcinoma and correlated with poor prognosis. Elevated miR-127 level drove a pronounced shift from the epithelial to the mesenchymal phenotype in cancer cells, and this shift was associated with their acquisition of stem-like traits, increased resistance to the epidermal growth factor receptor inhibitor and tumor-propagating potential. In contrast, antagonizing miR-127 markedly reversed this malignant transition, compromised the stem-like properties and the in vivo tumorigenic capability of cancer cells. Importantly, a regulatory loop involving the inflammatory signals NF-κB, miR-127 and tumor necrosis factor alpha-induced protein 3 was uncovered as a self-reinforcing circuitry that ensured an aggressive transition in lung cancer. Thus, this work identifies a novel molecular mechanism linking stemness, malignancy and inflammation, opening a new avenue for cancer treatment.

Hypoxic resistance of KRAS mutant tumor cells to 3-Bromopyruvate is counteracted by Prima-1 and reversed by N-acetylcysteine

Background

The metabolic inhibitor 3-bromopyruvate (3-BrPA) is a promising anti-cancer alkylating agent, shown to inhibit growth of some colorectal carcinoma with KRAS mutation. Recently, we demonstrated increased resistance to 3-BrPA in wt p53 tumor cells compared to those with p53 silencing or mutation. Since hypoxic microenvironments select for tumor cells with diminished therapeutic response, we investigated whether hypoxia unequally increases resistance to 3-BrPA in wt p53 MelJuso melanoma harbouring (Q61L)-mutant NRAS and wt BRAF, C8161 melanoma with (G12D)-mutant KRAS (G464E)-mutant BRAF, and A549 lung carcinoma with a KRAS (G12S)-mutation. Since hypoxia increases the toxicity of the p53 activator, Prima-1 against breast cancer cells irrespective of their p53 status, we also investigated whether Prima-1 reversed hypoxic resistance to 3-BrPA.

Results

In contrast to the high susceptibility of hypoxic mutant NRAS MelJuso cells to 3-BrPA or Prima-1, KRAS mutant C8161 and A549 cells revealed hypoxic resistance to 3-BrPA counteracted by Prima-1. In A549 cells, Prima-1 increased p21CDKN1mRNA, and reciprocally inhibited mRNA expression of the SLC2A1-GLUT1 glucose transporter-1 and ALDH1A1, gene linked to detoxification and stem cell properties. 3-BrPA lowered CAIX and VEGF mRNA expression. Death from joint Prima-1 and 3-BrPA treatment in KRAS mutant A549 and C8161 cells seemed mediated by potentiating oxidative stress, since it was antagonized by the anti-oxidant and glutathione precursor N-acetylcysteine.

Conclusions

This report is the first to show that Prima-1 kills hypoxic wt p53 KRAS-mutant cells resistant to 3-BrPA, partly by decreasing GLUT-1 expression and exacerbating pro-oxidant stress.

Acquired platinum resistance involves epithelial to mesenchymal transition through ubiquitin ligase FBXO32 dysregulation

To identify the molecules involved in epithelial to mesenchymal transition (EMT) in urothelial carcinoma (UC) after acquisition of platinum resistance, here we examined the changes in global gene expression before and after platinum treatment. Four invasive UC cell lines, T24, 5637, and their corresponding sublines T24PR and 5637PR with acquired platinum resistance, were assessed by microarray, and the ubiquitin E3 ligase FBXO32 was newly identified as a negative regulator of EMT in UC tumors after acquisition of platinum resistance. In vitro and in vivo studies showed an intimate relationship between FBXO32 expression and EMT, demonstrating that FBXO32 dysregulation in T24PR cells results in elevated expression of the mesenchymal molecules SNAIL and vimentin and decreased expression of the epithelial molecule E-cadherin. The association between FBXO32 expression and EMT was further validated using clinical samples. Knockdown of MyoD expression, a specific target of FBXO32 polyubiquitination, revealed upregulation of E-cadherin expression and downregulation of SNAIL and vimentin expression in T24PR cells. Comparative genomic hybridization array analysis demonstrated loss of heterozygosity at 8q24.13 in T24PR cells, which harbors FBXO32. Our findings suggest the importance of the association between EMT and ubiquitin-proteasome regulation when tumors develop acquired platinum resistance.

Mechanisms of Acquired Resistance to AZD9291: A Mutation-Selective, Irreversible EGFR Inhibitor

INTRODUCTION

AZD9291, a third-generation and mutation-selective epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI), is active against patients with EGFR-mutant non-small-cell lung cancer (NSCLC) who failed prior treatment with EGFR TKIs. However, acquired resistance to AZD9291 is inevitable. In this study, we identified the mechanisms of acquired resistance to AZD9291 in EGFR-mutant NSCLC.

METHODS

Four NSCLC patients with both an EGFR exon 19 deletion and the EGFR mutation after developing acquired resistance to first-generation EGFR TKIs received AZD9291 at doses of 20 to 80 mg/day in a phase I trial (NCT01802632). Paired tumor samples before and after treatment were obtained to evaluate EGFR modifications, alternative pathway activation, and histologic transformation. Genetic alterations were analyzed using Sanger sequencing, fluorescence in situ hybridization, real-time polymerase chain reaction, and targeted exome sequencing.

RESULTS

All four patients achieved a partial response (median duration of response, 9 months [range, 9-11 months]) and subsequently showed resistance to AZD9291. EGFR-mutant clones depopulated AZD9291-resistant tumors to below 1% (baseline, 14%-36%) in three patients with progression: one with the loss of EGFR-double mutant clones and two accompanied by transformation to small-cell carcinoma and focal fibroblast growth factor receptor 1 (FGFR1) amplification, respectively. EGFR-mutant clones remained and the EGFR ligand was overexpressed in one patient with focal progression to AZD9291.

CONCLUSION

Acquired resistance mechanisms of AZD9291 in patients with EGFR-mutant NSCLC who failed treatment with first-generation EGFR TKIs include the loss of EGFR-mutant clones plus alternative pathway activation or histologic transformation and EGFR ligand-dependent activation.

Evolution from genetics to phenotype: reinterpretation of NSCLC plasticity, heterogeneity, and drug resistance

Lung cancer is the leading cause of cancer-related deaths worldwide. Targeted therapy is beneficial in most cases, but the development of drug resistance stands as an obstacle to good prognosis. Multiple mechanisms were explored such as genetic alterations, activation of bypass signaling, and phenotypic transition. These intrinsic and/or extrinsic dynamic regulations facilitate tumor cell survival in meeting the demands of signaling under different stimulus. This review introduces lung cancer plasticity and heterogeneity and their correlation with drug resistance. While cancer plasticity and heterogeneity play an essential role in the development of drug resistance, the manipulation of them may bring some inspirations to cancer prognosis and treatment. That is to say, lung cancer plasticity and heterogeneity present us with not only challenges but also opportunities.

DUOX1 silencing in lung cancer promotes EMT, cancer stem cell characteristics and invasive properties

Dual oxidase 1 (DUOX1) is an oxidant-generating enzyme within the airway epithelium that participates in innate airway host defense and epithelial homeostasis. Recent studies indicate that DUOX1 is suppressed in lung cancers by epigenetic silencing, although the importance of DUOX1 silencing in lung cancer development or progression is unknown. Here we show that loss of DUOX1 expression in a panel of lung cancer cell lines is strongly associated with loss of the epithelial marker E-cadherin. Moreover, RNAi-mediated DUOX1 silencing in lung epithelial cells and the cancer cell line NCI-H292 was found to result in loss of epithelial characteristics/molecular features (altered morphology, reduced barrier function and loss of E-cadherin) and increased mesenchymal features (increased migration, anchorage-independent growth and gain of vimentin/collagen), suggesting a direct contribution of DUOX1 silencing to epithelial-to-mesenchymal transition (EMT), an important feature of metastatic cancer. Conversely, overexpression of DUOX1 in A549 cells was capable of reversing EMT features. DUOX1 silencing in H292 cells also led to enhanced resistance to epidermal growth factor receptor tyrosine kinase inhibitors such as erlotinib, and enhanced levels of cancer stem cell (CSC) markers CD133 and ALDH1. Furthermore, acquired resistance of H292 cells to erlotinib resulted in enhanced EMT and CSC features, as well as loss of DUOX1. Finally, compared with control H292 cells, H292-shDUOX1 cells displayed enhanced invasive features in vitro and in vivo. Collectively, our findings indicate that DUOX1 silencing in lung epithelial cancer cells promotes features of EMT, and may be strongly associated with invasive and metastatic lung cancer.

Primary Double-Strike Therapy for Cancers to Overcome EGFR Kinase Inhibitor Resistance: Proposal from the Bench

Diverse molecular mechanisms that confer acquired resistance to EGFR tyrosine kinase inhibitors (TKIs) in lung cancers with sensitive EGFR mutations have been reported. However, it is not realistic to analyze for all these mechanisms at the time of resistance in clinical practice and establish adequate treatment targeting these numerous resistance mechanisms. Therefore, we believe that we should move our research focus from the exploration of "established" diverse resistance mechanisms to the elucidation of molecular mechanisms that enable cancer cells to remain alive at the early phase of the treatment. Here in this review, we summarize up-to-date molecular mechanisms that maintain residual tumor cells against EGFR TKI monotherapy in lung cancers with EGFR mutations. We classified these mechanisms into three categories. The first is a preexisting minor subpopulation with a resistance mechanism such as a pretreatment T790M mutation that can be detected by highly sensitivity methods. The second is the reversible drug-tolerant state that is often observed in cell line models and accounts for the lack of complete response and continued survival of cells exposed to EGFR TKIs in patients. And the last is the role of the microenvironment, including survival signaling from fibroblasts or dying cancer cells and the role of poor vascularization. Primary double-strike cancer therapy, or even initial multiple-strike therapy, to cancer cells that cotarget EGFR and survival mechanism(s) simultaneously would be a promising strategy to improve the outcomes of patients with EGFR mutations.

A genetic cell context-dependent role for ZEB1 in lung cancer

The Zinc-finger E-box-binding Homeobox-1 (ZEB1) is a transcription factor that promotes epithelial–mesenchymal transition (EMT) and acts as an oncogene in KRAS-mutated lung cancer models. Here we report that ZEB1 exerts the opposite effect in EGFR-mutated lung cancer cells, where it suppresses growth by increasing microRNA-200 targets to antagonize ERBB3, a driver of mutant EGFR-dependent cell growth. Among these targets, NOTCH1 represses ERBB3 promoter activity and the expression of ERBB3. Furthermore, we find that EGFR inhibitor treatment, which inhibits the growth of EGFR-mutated cells, induces ZEB1. Despite its growth-inhibiting effect, EGFR inhibitor-induced ZEB1 strongly promotes EMT-dependent resistance to EGFR inhibitors partially through NOTCH1, suggesting a multifunctional role for NOTCH1 in EGFR-mutated cells. These results support a previously unrecognized genetic cell context-dependent role for ZEB1 and suggest that NOTCH1 may be a useful target for treating resistance to EGFR inhibitors, especially EMT-driven resistance.

ZEB1 is a driver of epithelial-to-mesenchymal transition that usually promotes lung cancer in the context of KRAS mutation. Here, the authors uncover a growth suppressive role for ZEB1 in EGFR mutant lung adenocarcinoma, thus elucidating the context dependent function of this protein.

The biological role of epithelial-mesenchymal transition in lung cancer (Review)

Epithelial-mesenchymal transition (EMT) is a process whereby epithelial cells gradually transform into mesenchymal-like cells losing their epithelial functionality and characteristics. EMT is thought to be involved in the pathogenesis of numerous lung diseases ranging from developmental disorders and fibrotic tissue remodeling to lung cancer. Lung cancer is the most lethal form of cancer worldwide, and despite significant therapeutic improvements, the patient survival rate still remains low. Activation of EMT endows invasive and metastatic properties upon cancer cells that favor successful colonization of distal target organs. The present review provides a brief insight into the mechanism and biological assessment methods of EMT in lung cancer and summarizes the recent literature highlighting the controversial experimental data and conclusions.