Alginate microspheres encapsulating hox transcript antisense RNA siRNA regulate the Hedgehog-Gli1 pathway to alleviate epidermal growth factor receptor tyrosine kinase inhibitors resistance

The long non-coding RNA HOTAIR and the Hedgehog-Gli1 signaling pathway are closely associated with tumor occurrence and drug resistance in various cancers. However, their specific roles in the development of EGFR-TKIs resistance in non-small cell carcinoma remain unclear. To address the issue of EGFR-TKIs resistance, this study utilized the electrospray method to prepare sodium alginate microspheres encapsulating HOTAIR siRNA (SA/HOTAIR siRNA) and investigated its effects on RNA interference (RNAi) in the gefitinib-resistant cell line PC9/GR. Furthermore, the study explored whether HOTAIR could modulate EGFR-TKIs resistance through the Hedgehog-GLi1 signaling pathway. The experimental results showed that sodium alginate (SA) microspheres demonstrated excellent biocompatibility with high encapsulation efficiency and drug-loading capacity, effectively enhancing the silencing efficiency of siRNA. HOTAIR siRNA significantly inhibited the proliferation, migration, and invasion abilities of PC9/GR cells while promoting apoptosis. Additionally, HOTAIR siRNA effectively suppressed tumor growth and downregulated the Hedgehog-GLi1 pathway and anti-apoptotic proteins, which were confirmed in animal experiments. Moreover, SA/HOTAIR siRNA exhibited superior inhibition of cellular and tumor functions compared to using HOTAIR siRNA alone. Clinical research findings indicated that monitoring the expression level of HOTAIR in the serum and urine samples of NSCLC patients before and after receiving EGFR-TKIs treatment can predict the efficacy of EGFR-TKIs to a certain extent. This study provided evidence that HOTAIR siRNA effectively mitigated the development of acquired resistance to EGFR-TKIs by inhibiting the Hedgehog-GLi1 pathway. Furthermore, it introduced a reliable and long-lasting drug delivery system for combating acquired resistance to EGFR-TKIs.

Tumor-associated Macrophages Mediate Gefitinib Resistance in Lung Cancer through HGF/c-met Signaling Pathway

BACKGROUND

The biological behavior of cells changes after they develop drug resistance, and the degree of resistance will be affected by the tumor microenvironment. In this study, we aimed to study the effects of M2 macrophages on gefitinib resistance.

METHODS

We polarized THP-1 cells into M0 and M2 macrophages, and conducted various experiments to investigate the effects of M2 macrophages on gefitinib resistance in lung cancer.

RESULTS

We found that M2 macrophages promote gefitinib resistance in HCC827 and PC9 cells. In addition, we used ELISA to measure the secretion level of HGF. HGF secretion levels were significantly increased in M2 macrophages. Exogenous HGF remarkably increased the proliferation and invasion in HCC827 and PC9 cells. However, the addition of anti-HGF antibodies abolished the proliferation and invasion of both HCC827 and PC9 cells promoted by M2 macrophages. Furthermore, M2 macrophages or exogenous HGF significantly increased the expression of p-met and p-ERK in HCC827 and PC9 cells, while anti-HGF antibodies diminished the expression of p-met and p-ERK by neutralizing HGF in M2 macrophages.

CONCLUSION

Our results revealed that M2 macrophages promote gefitinib resistance by activating ERK and HGF/c-met signaling pathways in HCC827 and PC9 cells. Our findings provide a new therapeutic strategy for gefitinib resistance in lung cancer.

TRIP13 overexpression promotes gefitinib resistance in non‑small cell lung cancer via regulating autophagy and phosphorylation of the EGFR signaling pathway

Non‑small cell lung cancer (NSCLC) accounts for the majority of lung cancers and remains the most common cause of cancer‑related death. Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (EGFR‑TKIs) have been used as first‑line treatment for patients with NSCLC showing EGFR mutations. Unfortunately, drug resistance is a crucial barrier affecting the treatment of patients with NSCLC. Thyroid hormone receptor interactor 13 (TRIP13) is an ATPase that is overexpressed in numerous tumors and is involved in drug resistance. However, whether TRIP13 plays a role in regulating sensitivity to EGFR‑TKIs in NSCLC remains unknown. TRIP13 expression was evaluated in gefitinib‑sensitive (HCC827) and ‑resistant (HCC827GR and H1975) cell lines. The effect of TRIP13 on gefitinib sensitivity was assessed using the MTS assay. The expression of TRIP13 was upregulated or knocked down to determine its effect on cell growth, colony formation, apoptosis and autophagy. Additionally, the regulatory mechanism of TRIP13 on EGFR and its downstream pathways in NSCLC cells were examined using western blotting, immunofluorescence and co‑immunoprecipitation assays. The expression levels of TRIP13 were significantly higher in gefitinib‑resistant than in gefitinib‑sensitive NSCLC cells. TRIP13 upregulation enhanced cell proliferation and colony formation while reducing the apoptosis of gefitinib‑resistant NSCLC cells, suggesting that TRIP13 may facilitate gefitinib resistance in NSCLC cells. In addition, TRIP13 improved autophagy to desensitize gefitinib in NSCLC cells. Furthermore, TRIP13 interacted with EGFR and induced its phosphorylation and downstream pathways in NSCLC cells. The present study demonstrated that TRIP13 overexpression promotes gefitinib resistance in NSCLC by regulating autophagy and activating the EGFR signaling pathway. Thus, TRIP13 could be used as a biomarker and therapeutic target for gefitinib resistance in NSCLC.

CA916798 predicts poor prognosis and promotes Gefitinib resistance for lung adenocarcinoma

Background

Our previous studies have identified CA916798 as a chemotherapy resistance-associated gene in lung cancer. However, the histopathological relevance and biological function of CA916798 in lung adenocarcinoma (LUAD) remains to be delineated. In this study, we further investigated and explored the clinical and biological significance of CA916798 in LUAD.

Methods

The relationship between CA916798 and clinical features of LUAD was analyzed by tissue array and online database. CCK8 and flow cytometry were used to measure cell proliferation and cell cycle of LUAD after knockdown of CA916798 gene. qRT-PCR and western blotting were used to detect the changes of cell cycle-related genes after knockdown or overexpression of CA916798. The tumorigenesis of LUAD cells was evaluated with or without engineering manipulation of CA916798 gene expression. Response to Gefitinib was evaluated using LUAD cells with forced expression or knockdown of CA916798.

Results

The analysis on LUAD samples showed that high expression of CA916798 was tightly correlated with pathological progression and poor prognosis of LUAD patients. A critical methylation site in promoter region of CA916798 gene was identified to be related with CA916798 gene expression. Forced expression of CA916798 relieved the inhibitory effects of WEE1 on CDK1 and facilitated cell cycle progression from G2 phase to M phase. However, knockdown of CA916798 enhanced WEE1 function and resulted in G2/M phase arrest. Consistently, chemical suppression of CDK1 dramatically inhibited G2/M phase transition in LUAD cells with high expression of CA916798. Finally, we found that CA916798 was highly expressed in Gefitinib-resistant LUAD cells. Exogenous expression of CA916798 was sufficient to endow Gefitinib resistance with tumor cells, but interference of CA916798 expression largely rescued response of tumor cells to Gefitinib.

Conclusions

CA916798 played oncogenic roles and was correlated with the development of Gefitinib resistance in LUAD cells. Therefore, CA916798 could be considered as a promising prognostic marker and a therapeutic target for LUAD.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-023-10735-3.

The pseudogene DUXAP10 contributes to gefitinib resistance in NSCLC by repressing OAS2 expression

Gefitinib, an epidermal growth factor receptor-tyrosine kinase inhibitor (EGFR-TKI),is the currently recommended first-line therapy for advanced EGFR-mutant lung cancer, and understanding the mechanism of resistance is the key to formulating therapeutic strategies for EGFR-TKIs. In this study, we evaluate the expression patterns and potential biological functions of the pseudogene DUXAP10 in gefitinib resistance. We find that pseudogene DUXAP10 expression is significantly upregulated in NSCLC gefitinib-resistant cells and tissues. Gain and loss of function assays reveal that knockdown of DUXAP10 by siRNA reverses gefitinib resistance both in vitro and in vivo. Furthermore, DUXAP10 interacts with the histone methyltransferase enhancer of zeste homolog 2 (EZH2) to repress the expression of 2',5'-oligoadenylate synthetase (OAS2). Overall, our study highlights the pivotal role of DUXAP10 in gefitinib resistance, and the DUXAP10/EZH2/OAS2 axis might be a promising therapeutic target to overcome acquired gefitinib resistance in NSCLC.

LncRNA AFAP1-AS1 Induces Gefitinib Resistance of Lung Adenocarcinoma Through the miR-653-5p/AGR2 Axis

Purpose

Gefitinib resistance limits the therapeutic efficacy of gefitinib to lung adenocarcinoma (LUAD). The goal of this research is to learn more about the lncRNA AFAP1-AS1 and how it functions in gefitinib-resistant LUAD cells.

Methods

RT-qPCR was performed to test the expression of AFAP1-AS1, miR-653-5p and AGR2 in LUAD tissues with acquired resistance to gefitinib or not as well as in gefitinib-resistant LUAD cells. Cell proliferation, invasion and apoptosis were measured by CCK8 assays, transwell invasion assays and flow cytometry, respectively. Luciferase reporter assay showed that miR-653-5p and AFAP1-AS1 or AGR2 interactions.

Results

In gefitinib-resistant LUAD cells and tissues, AFAP1-AS1 was overexpressed. Meanwhile, silencing AFAP1-AS1 reduced proliferation and migration while increasing apoptosis and gefitinib sensitivity. Mechanically, AFAP1-AS1 sequestered the miR-653-5p and blocked the inhibition of miR-653-5p to AGR2 and stepwise upregulated AGR2 overexpression in LUAD gefitinib resistant cells, resulting gefitinib resistance in LUAD.

Conclusion

AFAP1-AS1 promotes gefitinib-resistance LUAD cells through a previously unrecognized miR-653-5p/AGR2 axis, suggesting targeting AFAP1-AS1/miR-653-5p/AGR2 axis might be a promising way for LUAD intervention.

HMGB1-mediated autophagy promotes gefitinib resistance in human non-small cell lung cancer

Non-small cell lung cancer (NSCLC) ranks the first in incidence and mortality among malignant tumors in China. Molecular targeted therapies such as gefitinib, an oral inhibitor of the epidermal growth factor receptor tyrosine kinase, have shown significant benefits in patients with advanced NSCLC. However, most patients have unsatisfactory outcomes due to the development of drug resistance, and there is an urgent need to better understand the pathways involved in the resistance mechanisms. In this study, we found that HMGB1 is highly expressed in drug-resistant cells and confers to gefitinib resistance in NSCLC cells via activating autophagy process. Gefitinib upregulates HMGB1 expression in time-dependent and dose-dependent manners in human NSCLC cells. RNA interference-mediated knockdown of HMGB1 reduces PC9GR cell viability, induces apoptosis, and partially restores gefitinib sensitivity. Mechanistic analyses indicate that elevated HMGB1 expression contributes to gefitinib resistance by inducing autophagy. Thus, our results suggest that HMGB1 is an autophagy regulator and plays a key role in gefitinib resistance of NSCLC.

TSPYL2 reduced gefitinib resistance and DNA damage repair via suppressing SIRT1-mediated FOXO3 deacetylation

Background: Colorectal cancer (CRC) is a malignancy with high mortality. TSPYL2 participates in tumor suppression but its role in CRC remains unknown. Methodology & results: TSPYL2 was downregulated and SIRT1 was upregulated in gefitinib drug-resistant (GEF-DR) tissues of patients with CRC. The GEF-resistant cells, HCT116 and HCT-15, were successfully established. The knockdown of TSPYL2 promoted resistance to GEF in CRC cells. Interestingly, immunofluorescence and western blot assays demonstrated that TSPYL2 inhibited DNA damage repair in HCT-15 and HCT116 GEF-resistant cells. Mechanically, TSPYL2 reduced the resistance to GEF and inhibited DNA damage repair via suppressing SIRT1-mediated FOXO3 deacetylation. TSPYL2 consistently inhibited tumor growth and decreased resistance to GEF in vivo. Conclusion: TSPYL2 reduced resistance to GEF and suppressed DNA damage through downregulating SIRT1-mediated FOXO3 deacetylation, indicating that TSPYL2 might be a novel therapeutic target in CRC.

Long non-coding RNA prostate cancer-associated transcript 6 inhibited gefitinib sensitivity of non-small cell lung cancer by serving as a competing endogenous RNA of miR-326 to up-regulate interferon-alpha receptor 2

The critical roles of lncRNAs in drug resistance of malignancies have been widely recognized. This investigation aims to study the function of lncRNA PCAT6 in the resistance of non-small cell lung cancer (NSCLC) to gefitinib. In our study, we demonstrated that prostate cancer-associated transcript 6 (PCAT6) was upregulated in gefitinib-resistant NSCLC. PCAT6 knockdown inhibited gefitinib resistance of NSCLC, as indicated by decreased IC₅₀ value, proliferation, and metastasis, and increased cell apoptosis. Besides, PCAT6 could directly target miR-326 in gefitinib-resistant NSCLC cells and augment NSCLC resistance to gefitinib by serving as ceRNA of miR-326. Furthermore, interferon-alpha receptor 2 (IFNAR2) was validated as a downstream target of miR-326 and miR-326 reduced resistance to gefitinib by inhibiting IFNAR2 expression. Our investigation identified that PCAT6 enhanced gefitinib resistance of NSCLC via miR-326/IFNAR2 axis, which might offer a new therapeutic strategy against gefitinib resistance of NSCLC patients.

CXCR4 promotes gefitinib resistance of Huh7 cells by activating the c-Met signaling pathway

C‐X‐C chemokine receptor type 4 (CXCR4) expression is associated with poor prognosis of hepatocellular carcinoma (HCC). The aim of this study was to explore the biological role of CXCR4 in gefitinib resistance of HCC. Compared with a normal, non‐gefitinib‐resistant, human HCC cell line (Huh7), CXCR4 mRNA and protein were highly expressed in gefitinib‐resistant Huh7 cells (Huh7‐R). Cell proliferation was decreased, and apoptosis was enhanced in Huh7 cells in the presence of gefitinib. These influences conferred by gefitinib treatment on proliferation and apoptosis of Huh7 cells were abolished by CXCR4 overexpression. CXCR4 knockdown reduced the proliferation ability of HuH‐7R cells after gefitinib treatment. Importantly, CXCR4 overexpression had no influence on caveolin 1 (Cav‐1) expression; similarly, Cav‐1 silencing did not cause a substantive change in CXCR4 expression. However, CXCR4 activated Cav‐1, c‐Met, and Raf‐1 in Huh7 cells, whereas Cav‐1 silencing repressed the expression of Raf‐1 and phosphorylated c‐Met in Huh7 cells. CXCR4 overexpression promoted proliferation and repressed apoptosis in gefitinib‐treated Huh7 cells, which was partly rescued by PHA‐665752 (a c‐Met inhibitor) treatment or c‐Met deficiency. Finally, we constructed a tumor xenograft model to determine the influence of CXCR4 overexpression on tumor growth of HCC. CXCR4 overexpression accelerated tumor growth of HCC, which was abrogated by c‐Met deficiency. These findings demonstrate that CXCR4 overexpression activates c‐Met via the Cav‐1 signaling pathway, thereby promoting gefitinib resistance of Huh7 cells. Thus, this study highlights novel insights into the mechanism of gefitinib resistance of HCC and CXCR4 may become a potential target for HCC treatment.

Downregulation of HOXC6 by miR-27a ameliorates gefitinib resistance in non-small cell lung cancer

Non-small cell lung cancer (NSCLC) is a major type of lung cancer. Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs), represented by gefitinib (Gef), are targeted drugs used for the treatment of NSCLC. However, NSCLC patients often develop resistance to tyrosine kinase inhibitors, which limits their efficacy. Homeobox gene HOXC6 is dysregulated in many cancers and contributes to chemoresistance in cancer cells. However, the role and mechanism of HOXC6 in the development of Gef resistance in NSCLC remains unclear. In the present study, we found that HOXC6 was highly expressed in Gef-resistant NSCLC cells. Further experiments showed that silencing of HOXC6 ameliorated Gef resistance in PC9/G cells whereas overexpression of HOXC6 promoted Gef resistance in PC9 cells. HOXC6 influenced Gef sensitivity in NSCLC cells by regulating cell proliferation, colony formation, cell apoptosis, cell cycle, cell mobility and other related signaling molecules or pathways. HOXC6 was also found to be a direct target of miR-27a. As expected, overexpression of miR-27a ameliorated Gef resistance by inhibiting HOXC6 expression in vitro and in vivo. Clinical analysis revealed that high HOXC6 levels and low miR-27a levels were significantly correlated with more malignant clinical features and poorer survival of NSCLC patients. In summary, the present study demonstrates that HOXC6 may be a potential therapeutic target for overcoming Gef resistance in NSCLC patients. A combination of Gef and miR-27a agomirs may be an effective intervention for Gef-resistant NSCLC.

miR-145-5p Modulates Gefitinib Resistance by Targeting NRAS and MEST in Non-Small Cell Lung Cancer

OBJECTIVE

microRNAs may play essential roles in the development and drug resistance of non-small cell lung cancer (NSCLC). However, their functions and mechanisms are not fully understood. Our goal was to define the role of miR-145-5p in the gefitinib resistance of NSCLC.

MATERIALS AND METHODS

An A549 gefitinib-resistant cell line and xenograft nude mice were used in this study. The expression of miR-145-5p and its targets, NRAS and MEST, were detected and measured by qPCR, Western blot, RNA-FISH, or immunofluorescence analysis.

RESULTS

miR-145-5p was downregulated in gefitinib-resistant A549 cells (A549/Gef R). Overexpression of miR-145-5p enhanced the sensitivity to gefitinib and inhibited cell proliferation and invasion in A549/Gef R. miR-145-5p was also significantly reduced in LUAD and LUSC clinical samples and closely associated with a favorable prognosis, according to the UALCAN and TCGA databases. Moreover, NRAS and MEST were found to be downstream target genes of miR-145-5p and to function as oncogenes in NSCLC samples, and gefitinib resistance could be improved following the interference of these two molecules.

CONCLUSION

miR-145-5p improves the sensitivity of acquired gefitinib-resistant cells to gefitinib via inhibiting NRAS and MEST expression. The miR 145-5p-NRAS/MEST axis in NSCLC provides insights for the development of a NRAS/MEST targeting therapeutic approach to overcome gefitinib resistance in NSCLC patients.

Identification of Hub Genes and Small Molecule Drugs Associated with Acquired Resistance to Gefitinib in Non-Small Cell Lung Cancer

Targeting EGFR, epidermal growth factor receptor tyrosine kinase inhibitors (EGFR TKIs), brings lights to the treatment of non-small cell lung cancer (NSCLC). Although T790M mutation responded as one of the main reasons of acquired resistance, still 15% of the resistance patients can't be explained by the known mechanisms. The purpose of this research was to identify some new mechanisms of gefitinib acquired resistance, and to predict small molecules drugs which may reverse drug resistance by integrated bioinformatics analysis. The GSE34228 data package containing the microarray data of acquired gefitinib-resistant cell line (PC9GR) and gefitinib-sensitive cell line (PC9) from the GEO database were downloaded, and gene co-expression networks by weighted gene co-expression network analysis (WGCNA) were constructed to identified key modules and key genes related to gefitinib resistance. Furthermore, the significantly differentially expressed genes (DEGs) between the two cell types were screened out, and a protein-protein interaction (PPI) network to obtain the key genes of DEGs was accordingly constructed. Through the above two methods, 4 hub genes, PI3, S100A8, AXL and PNPLA4 were mined as the most relevant to gefitinib resistance. Among them, PI3, S100A8 were down-regulated in PC9GR cell samples, while AXL, PNPLA4 were up-regulated. The gene set enrichment analysis (GSEA) for single gene showed that the four hub genes were mainly correlated with cell proliferation and cycle. Besides, small molecule drugs with the potential to overcome resistance, such as Emetine and cephaeline, were screened by CMap database. Consistent with this, in vitro experiments results have shown that emetine and cephaeline can increase the sensitivity of drug-resistant cells to gefitinib, and the mechanism may be related to the regulation of PI3 and S100A8. In conclusion, 4 hub genes were found to be related to the occurrence of gefitinib resistance in non-small cell lung cancer, and several small molecule drugs were screened out as potential therapeutic agents to overcome gefitinib resistance, which may lead a new way for the treatment of NSCLC of acquired resistance to gefitinib.

MiR-133a-3p attenuates resistance of non-small cell lung cancer cells to gefitinib by targeting SPAG5

Background

Gefitinib is an epidermal growth factor receptor tyrosine kinase inhibitor (EGFR‐TKI), clinically used to treat patients with non‐small cell lung cancer driven by EGFR mutations. Unfortunately, EGFR‐TKI resistance has become a clinical problem for the effective treatment of NSCLC patients. The purpose of this study was to explore the effect and mechanism of miR‐133a‐3p on the gefitinib sensitivity of NSCLC cells.

Methods

The gefitinib‐resistant PC9 (PC9/GR) cells were established through repeated long‐term exposure to gefitinib for half a year. Then, PC9/GR cells were transfected with miR‐133a‐3p mimics and PC9 cells were transfected with miR‐133a‐3p inhibitors to increase or decrease the expression of miR‐133a‐3p. CCK‐8 assay, colony formation assay, and caspase‐3 activity assay were employed to detect cell resistance to gefitinib. Quantitative real‐time PCR and Western blotting were used to evaluate the levels of miR‐133a‐3p, SPAG5, and other related genes. Starbase database was used to predict the target gene of miR‐133a‐3p and the prognosis of NSCLC patients. Target gene of miR‐133a‐3p was verified through dual‐luciferase reporter gene assay.

Results

MiR‐133a‐3p was significantly downregulated in gefitinib‐resistant cell line PC9/GR vs. gefitinib‐sensitive cell line PC9. Overexpression of miR‐133a‐3p increased the sensitivity of NSCLC cells to gefitinib and vice versa. Furthermore, SPAG5 is an important target gene of miR‐133a‐3p, and SPAG5 can reverse miR‐133a‐3p‐mediated gefitinib sensitivity of NSCLC cells.

Conclusions

These findings indicated that miR‐133a‐3p/SPAG5 axis played a vital role in acquired resistance to gefitinib in NSCLC cells, and miR‐133a‐3p may represent a potential therapeutic strategy for the treatment of human NSCLC.

TIP30 overcomes gefitinib resistance by regulating cytoplasmic and nuclear EGFR signaling in non-small-cell lung cancer

Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) (eg, gefitinib) exert potent therapeutic efficacy in non–small‐cell lung cancer (NSCLC) harboring EGFR‐activating mutations. However, the resistance to EGFR TKIs limits their clinical therapeutic efficacy. TIP30, a newly identified tumor suppressor, appears to be involved in the regulation of cytoplasmic and nuclear EGFR signaling in NSCLC. Our previous study demonstrated that TIP30 regulated EGF‐dependent cyclin D1 transcription in human lung adenocarcinoma and suppressed tumorigenesis. In the present study, the involvement of TIP30 in combating gefitinib resistance in NSCLC was determined for the first time in vitro and in vivo. Gain and loss of function studies showed that overexpression of TIP30 effectively sensitized cells to gefitinib in vitro, whereas TIP30 inhibition promoted gefitinib cell resistance. Moreover, TIP30 negatively regulated the activation of the p‐AKT and p‐MEK signaling pathways in PC9/GR. Importantly, PC9/GR harbored high levels of nuclear EGFR, and overexpression of TIP30 restored irregular EGFR trafficking and degradation from early endosomes to the late endosomes, decreasing the nuclear accumulation of EGFR, which may partly or totally inhibit EGFR‐mediated induction of c‐Myc transcription. Xenographic tumors induced by overexpression of TIP30 by PC9/GR cells in nude mice were suppressed compared with their original counterparts. Overall, it was revealed that TIP30 overexpression restored gefitinib sensitivity in NSCLC cells and attenuated the cytoplasmic and nuclear EGFR signaling pathways and may be a promising biomarker in gefitinib resistance in NSCLC.

Long Noncoding RNA RP11-89K21.1 Interacts with miR-146a/b-5p to Promote Proliferation and Gefitinib Resistance Through Regulating RHPN2 and RhoA/ROCK Pathway in Lung Adenocarcinoma

Background: Long noncoding RNAs (lncRNAs) have major roles in lung adenocarcinoma (LUAD). lncRNA RP11-89K21.1 was reported to be abnormally expressed in LUAD, yet its biological functions in LUAD progression remain unclear. Materials and Methods: The 40 LUAD tissues and pair-matched adjacent normal tissues were enrolled in this study. Quantitative real-time polymerase chain reaction was performed to detect the expression of lncRNA, miRNA, and mRNA in LUAD samples and cell lines. Loss-of-function assays were used to evaluate the effects of RP11-89K21.1 on LUAD cell proliferation and gefitinib resistance. Bioinformatics analysis, luciferase reporter assay, and Western blot were employed to explore the regulatory relationships among RP11-89K21.1, miR-146a/b-5p, and RHPN2. Results: The authors identified that RP11-89K21.1 was highly expressed in LUAD tissues and cell lines. Moreover, upregulated RP11-89K21.1 was strongly associated with unfavorable overall survival of patients with LUAD. Knockdown of RP11-89K21.1 significantly suppressed proliferation and sensitized cell to gefitinib. Mechanistically, RP11-89K21.1 could directly bind miR-146a-5p and miR-146b-5p and decrease their expression to upregulate RHPN2, and subsequently activated RhoA/ROCK pathway. More importantly, overexpression of RHPN2 reversed regulatory effects of RP11-89K21.1 knockdown on cell proliferation and gefitinib resistance. Conclusions: These observations provide new insights into the role of RP11-89K21.1 in regulating LUAD tumorigenesis, suggesting that RP11-89K21.1 is a potential therapeutic target for LUAD treatment.

Zinc-finger E-box-binding homeobox 1 (ZEB1) plays a crucial role in the maintenance of lung cancer stem cells resistant to gefitinib

Background

Zinc‐finger E‐box‐binding homeobox 1 (ZEB1) is an important regulator of epithelial‐mesenchymal transition (EMT) and is involved in the maintenance of cancer stem cells (CSCs) via miR‐200c and BMI1 pathway. Recent studies revealed that ZEB1 contributes to the EMT‐mediated acquired resistance to gefitinib in EGFR‐mutant non‐small cell lung cancer (NSCLC). However, the precise role of ZEB1 in the maintenance of lung CSCs that lead to acquired resistance to gefitinib remains unclear.

Methods

PC9 and HCC827 NSCLC cell lines were treated with high concentrations of gefitinib, and surviving cells were referred to as “gefitinib‐resistant persisters” (GRPs). ZEB1 knockdown or overexpression was performed to determine the biological significance of ZEB1 in the CSC features of GRPs, and animal models were studied for in vivo validation. Expression of ZEB1, BMI1, and ALDH1A1 was analyzed by immunohistochemistry in tumor specimens from NSCLC patients with acquired resistance to gefitinib.

Results

GRPs had characteristic features of mesenchymal and CSC phenotypes with high expression of ZEB1 and BMI1, and decreased miR‐200c, in vitro and in vivo. ZEB1 silencing attenuated the suppression of miR‐200c, resulting in the reduction in BMI1 and reversed the mesenchymal and CSC features of GRPs. Furthermore, ZEB1 overexpression induced EMT and increased the levels of CD133‐ and BMI1‐positive GRPs in vitro and gefitinib resistance in vivo. Finally, ZEB1, BMI1, and ALDH1A1 were highly expressed in tumor specimens from EGFR‐mutant NSCLC patients with gefitinib resistance.

Conclusions

ZEB1 plays an important role in gefitinib‐resistant lung CSCs with EMT features via regulation of miR‐200c and BMI1.

RNA methyltransferase METTL3 induces intrinsic resistance to gefitinib by combining with MET to regulate PI3K/AKT pathway in lung adenocarcinoma

Clinical research data show that gefitinib greatly improves the progression‐free survival of patients, so it is used in advanced non‐small cell lung cancer patients with EGFR mutation. However, some patients with EGFR sensitive mutations do not have good effects on initial gefitinib treatment, and this mechanism is rarely studied. METTL3, a part of N6‐adenosine‐methyltransferase, has been reported to play an important role in a variety of tumours. In this study, we found that METTL3 is up‐regulated in gefitinib‐resistant tissues compared to gefitinib‐sensitive tissues. Cell function experiments have proved that under the treatment of gefitinib, METTL3 knockdown promotes apoptosis and inhibits proliferation of lung cancer cells. Mechanistic studies have shown that METTL3 combines with MET and causes the PI3K/AKT signalling pathway to be manipulated, which affects the sensitivity of lung cancer cells to gefitinib. Therefore, our research shows that METTL3 can be used as a molecular marker to predict the efficacy of EGFR‐TKI therapy in patients, and METTL3 may be a potential therapeutic target.

BST2 promotes growth and induces gefitinib resistance in oral squamous cell carcinoma via regulating the EGFR pathway

INTRODUCTION

Gefitinib, well known as a new antitumor agent, has been applied in various cancers such as oral squamous cell carcinoma (OSCC). However, most patients eventually acquire resistance to gefitinib, and the molecular mechanism of gefitinib resistance is not well described. Bone marrow stromal cell antigen 2 (BST2) has been reported to promote tumor cell growth and confer chemotherapy resistance in various cancers. However, the roles of BST2 in OSCC still need to be fully understood.

MATERIAL AND METHODS

We determined the expression of BST2 in OSCC tissues using qRT-PCR, immunohistochemistry and western blot. Next, we used MTT assay, flow cytometry and western blot to determine the roles of BST2 in OSCC cell proliferation, cycle progression and apoptosis, respectively. Furthermore, we evaluated the effect of BST2 on gefitinib resistance in OSCC cells and explored the related molecular mechanism.

RESULTS

BST2 expression was up-regulated in OSCC tissues compared with the adjacent normal tissues. BST2 overexpression significantly enhanced OSCC cell proliferation, mediated the cell cycle progression and inhibited cell apoptosis. Additionally, the results showed that BST2 overexpression effectively induced gefitinib resistance in OSCC cells. Subsequent analysis revealed that the underlying mechanism was associated with activation of the EGFR pathway.

CONCLUSIONS

Our study indicated that BST2 promoted growth and induced gefitinib resistance in OSCC cells, at least partially, through regulating the EGFR pathway. Thus, BST2 could be used as a therapeutic target for gefitinib resistance in OSCC.

Targeted inhibition of c-MET by podophyllotoxin promotes caspase-dependent apoptosis and suppresses cell growth in gefitinib-resistant non-small cell lung cancer cells

BACKGROUND

Lung cancer has the highest incidence and cancer-related mortality of all cancers worldwide. Its treatment is focused on molecular targeted therapy. c-MET plays an important role in the development and metastasis of various human cancers and has been identified as an attractive potential anti-cancer target. Podophyllotoxin (PPT), an aryltetralin lignan isolated from the rhizomes of Podophyllum species, has several pharmacological activities that include anti-viral and anti-cancer effects. However, the mechanism of the anti-cancer effects of PPT on gefitinib-sensitive (HCC827) or -resistant (MET-amplified HCC827GR) non-small cell lung cancer (NSCLC) cells remains unexplored.

PURPOSE

In the present study, we investigated the underlying mechanisms of PPT-induced apoptosis in NSCLC cells and found that the inhibition of c-MET kinase activity contributed to PPT-induced cell death.

METHODS

The regulation of c-MET by PPT was examined by pull-down assay, ATP-competitive binding assay, kinase activity assay, molecular docking simulation, and Western blot analysis. The cell growth inhibitory effects of PPT on NSCLC cells were assessed using the MTT assay, soft agar assay, and flow cytometry analysis.

RESULTS

PPT could directly interact with c-MET and inhibit kinase activity, which further induced the apoptosis of HCC827GR cells. In contrast, PPT did not significantly affect EGFR kinase activity. PPT significantly inhibited the cell viability of HCC827GR cells, whereas the PPT-treated HCC827 cells showed a cell viability of more than 80%. PPT dose-dependently induced G2/M cell cycle arrest, as shown by the downregulation of cyclin B1 and cdc2, and upregulation of p27 expression in HCC827GR cells. Furthermore, PPT treatment induced Bad expression and downregulation of Mcl-1, survivin, and Bcl-xl expression, subsequently activating multi-caspases. PPT thereby induced caspase-dependent apoptosis in HCC827GR cells.

CONCLUSION

These results suggest the potential of PPT as a c-MET inhibitor to overcome tyrosine kinase inhibitor resistance in lung cancer.

Zoledronic acid re‑sensitises gefitinib‑resistant lung cancer cells by inhibiting the JAK/STAT3 signalling pathway and reversing epithelial‑mesenchymal transition

Studies have shown that suppression of both the JAK/STAT3 pathway and epithelial‑mesenchymal transition (EMT) may overturn the resistance of non‑small cell lung cancer (NSCLC) cells to gefitinib. Zoledronic acid (ZA) injection is used to treat and prevent multiple forms of osteoporosis, hypercalcemia and bone metastasis‑related complications of malignancy. Clinical research has shown that ZA may exert antitumour effects and delay the progression of NSCLC. In the present study, we investigated whether ZA combined with gefitinib could re‑sensitise NSCLC cells to gefitinib in vitro and in vivo through inhibition of the JAK/STAT3 signalling pathway and EMT reversal. The results revealed that ZA potently increased the sensitivity of gefitinib‑resistant lung cancer cells to gefitinib. ZA decreased activation of JAK/STAT3 signalling and reversed EMT in the H1975 and HCC827GR cell lines. Furthermore, addition of IL‑6 to ZA‑pretreated gefitinib‑resistant cell lines abrogated the effect of ZA and restored the cellular resistance to tyrosine kinase inhibitors. Finally, ZA‑based combinatorial therapy effectively inhibited the growth of xenografts derived from gefitinib‑resistant cancer cells, which was correlated with the inhibition of the JAK/STAT3 signalling pathway and EMT reversal. In conclusion, ZA re‑sensitised gefitinib‑resistant lung cancer cells through inhibition of the JAK/STAT3 signalling pathway and EMT reversal. The combination of ZA and gefitinib may be a promising therapeutic strategy to reverse gefitinib resistance and prolong the survival of patients with NSCLC.

Targeting c-kit inhibits gefitinib resistant NSCLC cell growth and invasion through attenuations of stemness, EMT and acquired resistance

EGFR tyrosine kinase inhibitors (TKIs) are the first-line drugs for NSCLC. But, the acquired resistance limited their efficacy, so that the patients deteriorate eventually. Therefore, it is necessary to clarify the mechanism of the acquired resistance and overcome it for effective NSCLC therapy. In this experimental study, a stable gefitinib resistant lung adenocarcinoma cell line (PC9/GR) infected with shRNA-c-kit-homo-1386 were established; c-kit siRNA and c-kit inhibitors were used to block c-kit signaling; the acquired resistance of PC9/GR cells and the effects of c-kit siRNA and c-kit inhibitors on the growth and invasion of PC9/GR cells were investigated with CCK-8 assay, colony formation and cell invasion assays in vitro; the tumor growth inhibition effects of c-kit inhibitors on PC9/GR cell generated tumors were tested in vivo; the mechanisms involved in the acquired resistance reverse, growth and invasion inhibition effects of c-kit siRNA and c-kit inhibitors on PC9/GR cells were evaluated with qRT-PCR, Western blot and immunohistochemistry staining. The proliferation, colony formation, and invasion of PC9/GR cells were decreased by c-kit siRNA and inhibitors in vitro significantly; c-kit inhibitors suppressed the tumor growth of PC9/GR cell generated tumors in vivo. In the stable shRNA-c-kit transfected PC9/GR cells, the protein expressions of c-kit signaling and stemness phenotype related proteins, including ALDH1A1, Oct4, Sox2 and ABCG2 were decreased, and EMT phenotype related protein expressions including vimentin, N-cadherin, and Slug, were downregulated and with upregulation of E-cadherin; c-kit inhibitors reduced stemness phenotype related protein expressions, downregulated EMT phenotype related protein expressions including vimentin, N-cadherin, and Slug, with upregulation of E-cadherin, and the stemness related protein expressions of c-kit, ALDH1A1, ABCG2 and EMT-related proteins of vimentin and slug were decreased in the imatinib treated tumor tissues. The findings of this study indicated that c-kit signaling mediated the acquired gefitinib resistance, cell growth, invasion, stemness and EMT phenotype of PC9/GR cells. Targeting c-kit signaling with c-kit siRNA and small molecule c-kit inhibitors might overcome the acquired gefitinib resistance, and inhibit PC9/GR cell growth in vitro and in vivo.

Overexpression of CTEN is associated with gefitinib resistance in non-small cell lung cancer

COOH-terminus tensin-like molecule (CTEN) is a member of the tensin family, which is considered to be one of the novel proto-oncogenes involved in tumorigenesis and cancer progression. However, the mechanisms of CTEN in acquired resistance of non-small cell lung cancer (NSCLC) remain relatively unknown. The aim of the present study was to understand the roles of CTEN in acquired gefitinib resistance of NSCLC. The present study investigated the expression level of CTEN using reverse transcription-quantitative polymerase chain reaction and Western blot analysis. Cell Counting kit-8 and colony-formation assays were performed to evaluate the proliferative and colony-formative abilities of PC9 and PC9/GR cells in vitro. Mouse xenograft models were used to assess the growth of PC9/GR cells in vivo. A gefitinib-resistant NSCLC cell line (PC9/GR) was established, and the protein and mRNA expression levels of CTEN were observed to be higher in PC9/GR cells than in PC9 cells. Notably, the sensitivity of PC9/GR cells to gefitinib was observed to be decreased when CTEN was overexpressed, while PC9/GR cells with CTEN-downregulation showed markedly enhanced sensitivity to gefitinib. In vitro proliferation and colony formation assays revealed that increased CTEN markedly promoted the cell proliferative and colony-forming capacities of PC9 and PC9/GR cells, and CTEN-silencing inhibited the cell proliferative and colony-forming abilities of the PC9 and PC9/GR cells. Notably, deficient expression of CTEN notably retarded the growth of PC9/GR xenografts in vivo. In addition, the plasma mRNA expression of CTEN was notably elevated in patients with NSCLC with acquired gefitinib resistance. Overexpression of CTEN is associated with acquired gefitinib resistance in NSCLC. CTEN may be investigated as a potential therapeutic target for the treatment of patients with NSCLC with acquired gefitinib resistance.

M2 macrophages reduce the effect of gefitinib by activating AKT/mTOR in gefitinib-resistant cell lines HCC827/GR

BACKGROUND

The biological behavior of cells change after they develop drug resistance, and the degree of resistance will be affected by the tumor microenvironment. Here, we aimed to explore the changes in the biological behavior of tumors and to observe the differences in the release of cytokines and chemokines which can influence the tumor microenvironment. We also aimed to study how TKIs-resistant cell lines recruit macrophages to reduce the sensitivity of the cells following gefitinib administration.

METHODS

We generated and maintained gefitinib-resistant cell lines to study the differences between gefitinib-sensitive cell lines according to clone formation, cell growth curve analysis, whole-exome sequencing, and qPCR ARRAY technology. We used the WNT/β-catenin inhibitor, WNT/β-catenin activator and overexpression β-catenin lentivirus to observe the changes in CCL2. M2 macrophages and gefitinib-resistant cell lines HCC827/GR were cocultured to detect the viability gefitinib for inducing cell death.

RESULTS

The proliferation and migratory activities were much more pronounced in HCC827/GR cells. CCL2 expression was also enhanced and regulated by β-catenin in HCC827/GR. CCL2 promoted the chemotactic ability of M2 macrophages. M2 macrophages reduced the antitumor effect of gefitinib treatment by activating AKT/mTOR.

CONCLUSIONS

Gefitinib-resistant cell lines have stronger proliferation and migration capabilities, and attract macrophages by releasing more CCL2 to reduce the sensitivity of cells to gefitinib.

Multiomics Reveals Ectopic ATP Synthase Blockade Induces Cancer Cell Death via a lncRNA-mediated Phospho-signaling Network

The EGFR tyrosine kinase inhibitor gefitinib is commonly used for lung cancer patients. However, some patients eventually become resistant to gefitinib and develop progressive disease. Here, we indicate that ecto-ATP synthase, which ectopically translocated from mitochondrial inner membrane to plasma membrane, is considered as a potential therapeutic target for drug-resistant cells. Quantitative multi-omics profiling reveals that ecto-ATP synthase inhibitor mediates CK2-dependent phosphorylation of DNA topoisomerase IIα (topo IIα) at serine 1106 and subsequently increases the expression of long noncoding RNA, GAS5. Additionally, we also determine that downstream of GAS5, p53 pathway, is activated by ecto-ATP synthase inhibitor for regulation of programed cell death. Interestingly, GAS5-proteins interactomic profiling elucidates that GAS5 associates with topo IIα and subsequently enhancing the phosphorylation level of topo IIα. Taken together, our findings suggest that ecto-ATP synthase blockade is an effective therapeutic strategy via regulation of CK2/phospho-topo IIα/GAS5 network in gefitinib-resistant lung cancer cells.

miR-365a-5p suppresses gefitinib resistance in non-small-cell lung cancer through targeting PELI3

Aim: Demonstrate the function of dysregulated miR-365a-5p-PELI3 signaling axis in the generation of gefitinib resistance during treatment for non-small-cell lung cancer (NSCLC). Patients & methods: All the NSCLC patients who participated in this research were recruited from the Second Hospital of Hebei Medical University. PC9 cells and PC9GR cells were cultured for in vitro experiments. Results: Patients who were primary resistant to EGFR-tyrosine kinase inhibitor had lower miR-365a-5p levels. MiR-365a-5p directly targeted PELI3 mRNA. MiR-365a-5p overexpression enhanced the function of gefitinib in inhibiting cell viability. Tumor growth was suppressed through miR-365a-5p in nude mice. Conclusion: Dysregulated miR-365a-5p-PELI3 signaling axis triggered the generation of gefitinib resistance in NSCLC.

Overexpression of AGR2 Is Associated With Drug Resistance in Mutant Non-small Cell Lung Cancers

BACKGROUND/AIM

The resistance to epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs), such as gefitinib or erlotinib, is considered a major challenge in the treatment of patients with non-small cell lung cancer (NSCLC). Herein, we identified the critical roles of anterior gradient 2 (AGR2) in gefitinib (Gef) resistance of mutant NSCLC cells.

MATERIALS AND METHODS

Using datasets from a pair of NSCLC-sensitive and NSCLC-resistant cells, immunoblotting, immunofluorescence and immunohistochemistry, and cell viability assays were applied to identify the effects of AGR2.

RESULTS

AGR2 was found to be significantly over-expressed in Gef-resistant cells and was highly associated with drug resistance, proliferation, migration, and invasion of cancer cells. Moreover, AGR2 and ADAMTS6 formed a negative feedback loop in drug-resistant cells.

CONCLUSION

Modulation of overexpression of AGR2 in mutant NSCLC cells may be an attractive therapeutic strategy for the treatment of EGFR-TKI-resistant NSCLC.

Cyclooxygenase-2 mediates gefitinib resistance in non-small cell lung cancer through the EGFR/PI3K/AKT axis

Gefitinib is a potent inhibitor of EGFR and represents the front-line treatment for non-small cell lung cancer (NSCLC) therapeutics. However, NSCLC patients are prone to develop acquired resistance through as yet, undefined mechanisms of resistance. Here, we investigated the role of COX-2 during gefitinib resistance in NSCLC cells and revealed its underlying mechanism(s) of action. We report the upregulation of COX-2 in gefitinib-resistant NSCLC tissues and cells, which is associated with poor prognosis. In vitro assays in NSCLC cells (PC9/GR) showed that COX-2 facilitates gefitinib resistance in NSCLC cells through its effects on P-gp, MRP1, and BCRP, and cancer cell migration and invasion. In vivo, COX-2 silencing could repress tumor growth. We found that the overexpression of COX-2 enhances the transcription of MMP-2, MMP-7, and MMP-9 which mediates PI3K-AKT activation. In summary, we demonstrate that COX-2 mediates the gefitinib resistance of NSCLC cells through its interaction with EGFR and the PI3K-AKT axis. This highlights COX-2 as a novel molecular target for NSCLC.

Knockdown of PLAT enhances the anticancer effect of gefitinib in non-small cell lung cancer

Background

Tyrosine kinase inhibitors (TKIs), such as gefitinib, are widely used as standard treatments for non-small cell lung cancer (NSCLC) patients with epidermal growth factor receptor (EGFR) mutations. However, the subsequent inevitable drug resistance has become a major challenge in clinical treatment. The aim of this study was to investigate the role of tissue-type plasminogen activator (PLAT) in gefitinib resistance in NSCLC.

Methods

The function of PLAT was determined using gefitinib-resistant cells and a nude mouse model. The gene knockdown was achieved by Lentivirus based RNA silence technique. Expression of relevant genes and proteins, cell viability, proliferation, apoptosis, cell cycle, reactive oxygen species levels, mitochondrial membrane potential and differential gene expression was detected by RT-qPCR, western blot, cell counting kit-8 assay, EdU incorporation, flow cytometry, JC-1 dye assay and complementary DNA arrays. The effects of PLAT knockdown on tumorigenesis was analyzed in vivo.

Results

Gefitinib-resistant cells expressed higher levels of PLAT and that knockdown of PLAT in resistant cells restored gefitinib sensitivity. Tumor proliferation was limited in vivo following PLAT knockdown. Moreover, PLAT knockdown affected mitochondrial function, caused caspase activation and cell cycle arrest, and activated TNF-α signaling, leading to apoptosis of gefitinib-resistant PC9 cells.

Conclusions

Our results suggest that PLAT reduces apoptosis of NSCLC cells and knockdown of PLAT enhances anticancer effect of gefitinib by upregulating TNF-α signaling.

Combined treatment with N-acetylcysteine and gefitinib overcomes drug resistance to gefitinib in NSCLC cell line

We aimed to explore the molecular substrate underlying EGFR‐TKI resistance and investigate the effects of N‐acetylcysteine (NAC) on reversing EGFR‐TKI resistance. In the current research, the effects of NAC in combination with gefitinib on reversing gefitinib resistance were examined using CCK‐8 assay, combination index (CI) method, matrigel invasion assay, wound‐healing assay, flow cytometry, western blot, and quantitative real‐time PCR (qRT‐PCR). CCK8 assay showed that NAC plus gefitinib combination overcame EGFR‐TKI resistance in non‐small cell lung cancer (NSCLC) cells by lowering the value of half maximal inhibitory concentration (IC50). CI calculations demonstrated a synergistic effect between the two drugs (CI < 1). Matrigel invasion assay and wound healing assay demonstrated a decrease in migration and invasion ability of PC‐9/GR cells after NAC and gefitinib treatment. Flow cytometry displayed enhanced apoptosis in the combination group. Western blot and qRT‐PCR revealed that increased E‐cadherin and decreased vimentin in the combination group. When PP2 was administered with gefitinib, the same effects were seen. Our findings suggest that NAC could restore the sensitivity of gefitinib‐resistant NSCLC cells to gefitinib via suppressing Src activation and reversing epithelial‐mesenchymal transition.

Linc01014 regulates gefitinib resistance in oesophagus cancer via EGFR-PI3K-AKT-mTOR signalling pathway

This study aimed to explore the underlying mechanism of linc01014 in oesophagus cancer gefitinib resistance. Gefitinib-resistant oesophagus squamous cell carcinoma (ESCC gefitinibR) cell lines were constructed by using different gefitinib treatment in FLO-1, KYAE-1, TE-8 and TE-5 cell lines and confirmed by MTS50 and proliferation assays. Expression of linc01014 was overexpressed/silenced in FLO-1 cells followed by gefitinib treatment, and then, the apoptosis-associated markers Bax and Bcl-2, and PI3KCA in PI3K signalling pathway were determined using Western blotting. MST50 and morphology analyses showed that ESCC gefitinibR cell lines presented obvious gefitinib resistance than their parental ESCC cell lines. ESCC gefitinibR cell lines showed significantly higher proliferation abilities than their parental ESCC cell lines after treating with gefitinib. Overexpression of linc01014 significantly inhibited the apoptosis of FLO-1 cells induced by gefitinib and silencing linc01014 obviously promoted the apoptosis of FLO-1 cells induced by gefitinib. Silencing linc01014 could significantly increase the gefitinib chemotherapy sensitivity of oesophagus cancer via PI3K-AKT-mTOR signalling pathway.

Decitabine reverses gefitinib resistance in PC9 lung adenocarcinoma cells by demethylation of RASSF1A and GADD45β promoter

The acquired resistance to epidermal growth factor receptor tyrosine kinase inhibitor (EGFR-TKI) is the major reason for the failure of target therapy in advanced non small cell lung cancer (NSCLC) patients, the mechanism of which has not been fully elucidated yet. The present study aimed to investigate the different DNA methylation profile before and after acquired EGFR-TKI resistance, and explore the influence of the DNA demethylater, decitabine, on EGFR-TKI resistance. The DNA methylation chip was used to screen the genes whose DNA methylation status were changed in the EGFR-TKI sensitive human NSCLC cell line PC9, and the induced EGFR-TKI resistant NSCLC cell line PC9/GR (harboring T790M mutation). According to the results and literature reports, the tumor suppressor genes, RASSF1A and GADD45β were selected for further research. Methylation specific PCR (MSP) and western blot further confirmed that the promoters of these two genes were methylated, and the protein expressions were significantly inhibited in PC9/GR cells. Additionally, decitabine, the DNA methyl transferase inhibitor, could reverse the methylation status of RASSF1A and GADD45β promoters, elevate protein expression, and partially restore the sensitivity of PC9/GR cells to EGFR-TKI. To conclude, our results suggested that the DNA methylation of RASSF1 and GADD45β may play a role in EGFR-TKI resistance, and epigenetic intervention might be an effective strategy to reverse EGFR-TKI resistance, suggesting further study.

The Effects and Mechanisms by which Saikosaponin-D Enhances the Sensitivity of Human Non-small Cell Lung Cancer Cells to Gefitinib

Non-small cell lung cancer (NSCLC) patients with epidermal growth factor receptor (EGFR)-sensitive mutations benefit from epidermal growth factor receptor tyrosine kinase inhibitors (EGFR- TKIs). However, drug resistance is a major cause of therapeutic failure. This study examined whether saikosaponin-d (SSD) enhances the anti-tumor effect of gefitinib in NSCLC cells. Cell Counting Kit-8 (CCK-8) was used to determine cell viability. Cell apoptosis was examined by flow cytometry. Signal transducer and activator of transcription (STAT3), phosphor-STAT3 (P-STAT3), and B-cell lymphoma 2 (Bcl-2) were detected by Western blot. An HCC827/GR tumor model was established to observe the effect of combination therapy in vivo. The combination of SSD with gefitinib had an enhanced inhibitory effect by reducing cell viability and inducing cells apoptosis in NSCLC cells. Furthermore, SSD decreased and increased the expression of P-STAT3 and Bcl-2, respectively. Down-regulated STAT3 promoted the sensitivity of lung cancer cells to gefitinib. The results of animal experiments also showed that SSD enhanced the anti-tumor effect of gefitinib. These results indicated that the combination of SSD with gefitinib had an increased antitumor effect in NSCLC cells and that the molecular mechanisms were associated with the inhibition of STAT3/Bcl-2 signaling pathway. Our findings suggest a promising approach for the treatment of NSCLC patients with EGFR-TKI resistance.

EGCG overcomes gefitinib resistance by inhibiting autophagy and augmenting cell death through targeting ERK phosphorylation in NSCLC

Background

Several EGFR-tyrosine kinase inhibitors (TKIs), such as gefitinib (Gef), have been used as effective clinical therapies for patients with non-small cell lung cancer (NSCLC). However, due to acquired resistance, the efficacy of Gef treatment is severely blocked. Our preliminary study found that epigallocatechin gallate (EGCG) in combination with Gef could work synergistically to increase the sensitivity to Gef in NSCLC, but the mechanisms responsible for this have not been completely defined.

Purpose

In our present study, we devoted to investigate the synergistic effects of combined EGCG and Gef treatment and the importance of autophagy and ERK signaling pathway in overcoming acquired drug resistance to Gef in NSCLC.

Methods

We evaluated the synergistic effects of combined EGCG and Gef treatment through in vitro cell proliferation/viability assays and in vivo xenograft studies, respectively. Autophagic flux was assessed by GFP-microtubule-associated protein 1 light chain 3 (LC3) plasmid transfection and western blot detection of autophagy-related proteins. Besides, the role of ERK on acquired resistance was validated with a ERK inhibitor.

Results

We discovered that EGCG can synergize with Gef to inhibit the proliferation of Gef-resistant NSCLC cells and suppress tumor growth in a xenograft mouse model. The underlying mechanisms of synergism were investigated, and the results showed that co-treatment with Gef and EGCG could inhibit Gef-induced autophagy and ERK phosphorylation. Consistently, the expression of LC3-II/I and ATG5 were inhibited, whereas the expression of p62 was enhanced in EGCG and Gef combination treatment groups. Further, inhibition of autophagy in Gef-resistant A549 cells could augment cell death.

Conclusion

In conclusion, EGCG overcomes Gef resistance by inhibiting autophagy and augmenting cell death through targeting ERK pathway in NSCLC. Gef and EGCG combination therapy may be an effective strategy to overcome acquired resistance in NSCLC.

Trans-3,5,4´-trimethoxystilbene reduced gefitinib resistance in NSCLCs via suppressing MAPK/Akt/Bcl-2 pathway by upregulation of miR-345 and miR-498

Despite initial dramatic efficacy of epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (EGFR‐TKIs) in EGFR‐mutant lung cancer patients, subsequent emergence of acquired resistance is almost inevitable. Resveratrol and its derivatives have been found to exert some effects on EGFR‐TKI resistance in non‐small cell lung cancer (NSCLC), but the underlying mechanisms remain unclear. We screened several NSCLC cell lines with gefitinib resistance by MTT assay and analysed the miR‐345/miR‐498 expression levels. NSCLC cells were pre‐treated with a resveratrol derivative, trans‐3,5,4‐trimethoxystilbene (TMS) and subsequently challenged with gefitinib treatment. The changes in apoptosis and miR‐345/miR‐498 expression were analysed by flow cytometry and q‐PCR respectively. The functions of miR‐345/miR‐498 were verified by CCK‐8 assay, cell cycle analysis, dual‐luciferase reporter gene assay and immunoblotting analysis. Our results showed that the expression of miR‐345 and miR‐498 significantly decreased in gefitinib resistant NSCLC cells. TMS pre‐treatment significantly upregulated the expression of miR‐345 and miR‐498 increasing the sensitivity of NSCLC cells to gefitinib and inducing apoptosis. MiR‐345 and miR‐498 were verified to inhibit proliferation by cell cycle arrest and regulate the MAPK/c‐Fos and AKT/Bcl‐2 signalling pathways by directly targeting MAPK1 and PIK3R1 respectively. The combination of TMS and gefitinib promoted apoptosis also by miR‐345 and miR‐498 targeting the MAPK/c‐Fos and AKT/Bcl‐2 signalling pathways. Our study demonstrated that TMS reduced gefitinib resistance in NSCLCs via suppression of the MAPK/Akt/Bcl‐2 pathway by upregulation of miR‐345/498. These findings would lay the theoretical basis for the future study of TMS for the treatment of EGFR‐TKI resistance in NSCLCs.

Long Noncoding RNA LINC00460 Promotes the Gefitinib Resistance of Nonsmall Cell Lung Cancer Through Epidermal Growth Factor Receptor by Sponging miR-769-5p

The vital roles of long noncoding RNAs (lncRNAs) in the nonsmall cell lung cancer (NSCLC) tumorigenesis are increasingly important. This work aims to investigate the role of lncRNA LINC00460 in the gefitinib resistance of NSCLC cells and discover its relevant mechanism. Our finding reveals that the expression of lncRNA LINC00460 is upregulated in the gefitinib-resistant NSCLC tissue and cells, and closely correlated with advanced tumor stage and clinical poor prognosis outcome. Gain and loss functional assays are performed in gefitinib-resistant NSCLC cells (A549/GR), stating that LINC00460 facilitates the 50% inhibitive concentration of gefitinib for NSCLC cells, multidrug-resistant-related proteins (P-gp, MRP1, and BCRP), as well as the invasion. In vivo, LINC00460 silencing represses the tumor growth. Bioinformatics prediction tools and luciferase analysis confirm that the upregulated LINC00460 sponged miR-769-5p in NSCLC cells; moreover, epidermal growth factor receptor (EGFR) is identified as a direct target gene of miR-769-5p. Verification experiments confirm that the restoration of EGFR could weaken the sensibility of NSCLC cells toward the gefitinib. In conclusion, our result demonstrates that LINC00460 plays a pivotal role in gefitinib resistance of NSCLC cells by targeting EGFR through sponging miR-769-5p. This finding might serve as a therapeutic target for NSCLC.

Metformin sensitizes hypoxia-induced gefitinib treatment resistance of HNSCC via cell cycle regulation and EMT reversal

Objectives

The objectives of this study were to explore the mechanisms of metformin sensitization to hypoxia-induced gefitinib treatment in resistant head and neck squamous cell carcinoma (HNSCC) and evaluate the effects of this combined treatment strategy.

Methods

The effects of gefitinib treatment on HNSCC were measured under normoxic and hypoxic conditions. The relationship between hypoxia and cell cycle and epithelial-mesenchymal transition (EMT) in tumor cells were analyzed. Palbociclib and LY294002 were used in combination with gefitinib to evaluate the effects on HNSCC cell cytotoxicity during hypoxia. Finally, metformin was used to evaluate the sensitizing effects of gefitinib treatment on HNSCC in vivo and in vitro.

Results

Cell viability and apoptosis assays demonstrated a significant difference in HNSCC cells treated with gefitinib between the normoxia and hypoxia groups. Hypoxia induced the expression of cyclin D1, decreased the percentage of cells in G1, and promoted the EMT of tumor cells. Both palbociclib and LY294002 enhanced gefitinib-induced cytotoxicity of HNSCC cells under hypoxic conditions. Encouragingly, metformin sensitized HNSCC to gefitinib treatment in vivo and in vitro.

Conclusion

Hypoxia promotes G1-S cell cycle progression and EMT in HNSCC, resulting in gefitinib treatment resistance. Metformin sensitizes HNSCC to gefitinib treatment, which might serve as a novel combined treatment strategy.

Integrative Analysis of Proteome and Ubiquitylome Reveals Unique Features of Lysosomal and Endocytic Pathways in Gefitinib-Resistant Non-Small Cell Lung Cancer Cells

Non-small cell lung cancer (NSCLC) patients carrying EGFR activating mutations treated with gefitinib, a tyrosine kinase inhibitor, will develop drug resistance. Ubiquitylation is one of major posttranslational modifications of proteins affecting the stability or function of proteins. However, the role of protein ubiquitylation in gefitinib resistance is poorly understood. To systematically identify the global change in protein expression and ubiquitylation during gefitinib resistance, a quantitative global proteome and ubiquitylome study in a pair of gefitinib-resistant and sensitive NSCLC cells is carried out. Altogether, changes in expression of 3773 proteins are quantified, and changes in ubiquitylation of 2893 lysine sites in 1415 proteins are measured in both cells. Interestingly, lysosomal and endocytic pathways, which are involved in autophagy regulation, are enriched with upregulated proteins or ubiquitylated proteins in gefitinib-resistant cells. In addition, HMGA2 overexpression or ALOX5 knockdown suppresses gefitinib resistance in NSCLC cells by inhibiting autophagy. Overall, these results reveal the previously unknown global ubiquitylome and proteomic features associated with gefitinib resistance, uncover the opposing roles of HMGA2 or ALOX5 in regulating gefitinib resistance and autophagy, and will help to identify new therapeutic targets in overcoming gefitinib resistance.

Krüppel-like factor 4 promotes c-Met amplification-mediated gefitinib resistance in non-small-cell lung cancer

Gefitinib has been widely used in the first‐line treatment of advanced EGFR‐mutated non‐small‐cell lung cancer (NSCLC). However, many NSCLC patients will acquire resistance to gefitinib after 9‐14 months of treatment. This study revealed that Krüppel‐like factor 4 (KLF4) contributes to the formation of gefitinib resistance in c‐Met‐overexpressing NSCLC cells. We observed that KLF4 was overexpressed in c‐Met‐overexpressing NSCLC cells and tissues. Knockdown of KLF4 increased tumorigenic properties in gefitinib‐resistant NSCLC cell lines without c‐Met overexpression, but it reduced tumorigenic properties and increased gefitinib sensitivity in gefitinib‐resistant NSCLC cells with c‐Met overexpression, whereas overexpression of KLF4 reduced gefitinib sensitivity in gefitinib‐sensitive NSCLC cells. Furthermore, Western blot analysis revealed that KLF4 contributed to the formation of gefitinib resistance in c‐Met‐overexpressing NSCLC cells by inhibiting the expression of apoptosis‐related proteins under gefitinib treatment and activating the c‐Met/Akt signaling pathway by decreasing the inhibition of β‐catenin on phosphorylation of c‐Met to prevent blockade by gefitinib. In summary, this study's results suggest that KLF4 is a promising candidate molecular target for both prevention and therapy of NSCLC with c‐Met overexpression.

Exosome-mediated gefitinib resistance in lung cancer HCC827 cells via delivery of miR-21

Acquired resistance to gefitinib remains a major challenge in cancer treatment. In the present study, the effect of exosomes on the transmission of gefitinib resistance from gefitinib-resistant HCC827 lung cancer cells (H827R) to their gefitinib-sensitive counterparts and the potential underlying mechanisms by which this occurs was investigated. Exosomes were obtained from the cell supernatant using ultracentrifugation and the ExoQuick-TC exosome precipitation solution. Drug resistance was assessed by flow cytometry, apoptosis assays and cell counting kit-8 assays. The expression of microRNA (miR)-21 was analyzed by reverse transcription-quantitative polymerase chain reaction. Exosomes released by H827R cells (R/exo) may decrease the sensitivity of the human NSCLC HCC827 cell line to gefitinib. The results indicated that miR-21 expression was increased in R/exo and R/exo-treated H827S cells. However, miR-21 inhibition abrogated exosome-mediated drug resistance. Phosphorylated-protein kinase B (p-Akt), which is downstream of miR-21, was downregulated following gefitinib treatment; however, R/exo pretreatment elevated p-Akt levels and promoted the activation of Akt. By contrast, miR-21 inhibition reduced p-Akt expression. Therefore, the induction of miR-21 via exosomes and the activation of Akt may be mechanisms by which exosomes mediate the transfer of drug resistance.

miR-1-3p and miR-206 sensitizes HGF-induced gefitinib-resistant human lung cancer cells through inhibition of c-Met signalling and EMT

Hepatocyte growth factor (HGF) overexpression is an important mechanism in acquired epidermal growth factor receptor (EGFR) kinase inhibitor gefitinib resistance in lung cancers with EGFR activating mutations. MiR-1-3p and miR-206 act as suppressors in lung cancer proliferation and metastasis. However, whether miR-1-3p and miR-206 can overcome HGF-induced gefitinib resistance in EGFR mutant lung cancer is not clear. In this study, we showed that miR-1-3p and miR-206 restored the sensitivities of lung cancer cells PC-9 and HCC-827 to gefitinib in present of HGF. For the mechanisms, we demonstrated that both miR-1-3p and miR-206 directly target HGF receptor c-Met in lung cancer. Knockdown of c-Met mimicked the effects of miR-1-3p and miR-206 transfections Meanwhile, c-Met overexpression attenuated the effects of miR-1-3p and miR-206 in HGF-induced gefitinib resistance of lung cancers. Furthermore, we showed that miR-1-3p and miR-206 inhibited c-Met downstream Akt and Erk pathway and blocked HGF-induced epithelial-mesenchymal transition (EMT). Finally, we demonstrated that miR-1-3p and miR-206 can increase gefitinib sensitivity in xenograft mouse models in vivo. Our study for the first time indicated the new function of miR-1-3p and miR-206 in overcoming HGF-induced gefitinib resistance in EGFR mutant lung cancer cell.

Targeting Nicotinamide N-Methyltransferase and miR-449a in EGFR-TKI-Resistant Non-Small-Cell Lung Cancer Cells

Epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) are used clinically as target therapies for lung cancer patients, but the occurrence of acquired drug resistance limits their efficacy. Nicotinamide N-methyltransferase (NNMT), a cancer-associated metabolic enzyme, is commonly overexpressed in various human tumors. Emerging evidence also suggests a crucial loss of function of microRNAs (miRNAs) in modulating tumor progression in response to standard therapies. However, their precise roles in regulating the development of drug-resistant tumorigenesis are still poorly understood. Herein, we established EGFR-TKI-resistant non-small-cell lung cancer (NSCLC) models and observed a negative correlation between the expression levels of NNMT and miR-449a in tumor cells. Additionally, knockdown of NNMT suppressed p-Akt and tumorigenesis, while re-expression of miR-449a induced phosphatase and tensin homolog (PTEN), and inhibited tumor growth. Furthermore, yuanhuadine, an antitumor agent, significantly upregulated miR-449a levels while critically suppressing NNMT expression. These findings suggest a novel therapeutic approach for overcoming EGFR-TKI resistance to NSCLC treatment.

Molecular mechanism of action and potential biomarkers of growth inhibition of synergistic combination of afatinib and dasatinib against gefitinib-resistant non-small cell lung cancer cells

Epidermal growth factor receptor - tyrosine kinase inhibitor (EGFR-TKI) is the first choice of treatment for advanced non-small cell lung cancer (NSCLC) patients harbouring activating EGFR mutations. However, single agent usually has limited efficacy due to heterogeneous resistant mechanisms of cancer cells. Thus drug combination therapy would offer more benefits by synergistic interactions and avoidance of resistance emergence. In this study, we selected 8 NSCLC cell lines with different genetic characteristics as research models to investigate the efficacy of 4 agents (gefitinib, cetuximab, afatinib and dasatinib) and their combinations. As a single agent, both afatinib and dasatinib showed more inhibition against cell proliferation than gefitinib and cetuximab. Afatinib combined with dasatinib demonstrated significantly high efficacy against 7 gefitinib-resistant NSCLC cell lines. Moreover, it reversed the resistance to the 4 studied single agents in PTEN mutated NSCLC cells. By studying the activity of EGFR, Src and their downstream signalling pathways including PI3K/PTEN/Akt, Ras/Raf/MEK/ERK, Src/FAK and JAK/Stat, we demonstrated the synergistic interaction between afatinib and dasatinib was not only due to their blockage of different signalling pathways but also the complemental inhibition of the related signalling molecules such as Stat3. We also found that the level of Src, Stat3, and MAPK may be useful biomarkers predicating synergism between afatinib and dasatinib for the treatment of gefitinib-resistant NSCLC cells.

ERK inhibition represses gefitinib resistance in non-small cell lung cancer cells

Gefitinib, an EGFR tyrosine kinase inhibitor, is used to treat non-small cell lung cancer (NSCLC) patients with activating EGFR mutations. However, the resistance to gefitinib eventually emerges in most of the patients. To understand its mechanism, we generated two acquired gefitinib-resistant NSCLC cell lines. The resistant cells have slower growth rates, but are more resistant to apoptosis in the presence of gefitinib, compared with their sensitive counterparts. In addition, our genome-wide transcriptome analysis reveals unexpected pathways, particularly autophagy, are dysregulated in the gefitinib-resistant cells. Autophagy is significantly enhanced in resistant cells. Importantly, inhibition of autophagy reduces gefitinib resistance. Furthermore, the phosphorylation of ERK, the extracellular signal-regulated kinase, is activated in resistant cells. Inhibition of ERK phosphorylation abrogates gefitinib resistance by suppressing autophagy both in vitro and in vivo. These findings establish a link between ERK and autophagy in gefitinib resistance, and suggest that the ERK signaling may serve as the potentially therapeutic target for treating gefitinib resistance in NSCLC patients.

Lentivirus-mediated silencing of HOTAIR lncRNA restores gefitinib sensitivity by activating Bax/Caspase-3 and suppressing TGF-α/EGFR signaling in lung adenocarcinoma

Secondary resistance is a major limitation in the efficacy of epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor treatment of lung cancer. Previous studies have shown that expression of the long non-coding RNA HOX transcript antisense RNA (HOTAIR) is upregulated in lung cancer, which is correlated with metastasis and poor prognosis. However, the precise role of HOTAIR and its effects on gefitinib resistance in human lung adenocarcinoma are not known. To address this issue, in the present study we established a gefitinib-resistant (R)PC-9 human lung adenocarcinoma cell line and examined cell viability with the 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium assay. We found that gefitinib concentrations <10 µM inhibited the viability of PC-9 but not RPC-9 cells in a dose-dependent manner. Lentivirus-mediated HOTAIR RNA interference induced cell apoptosis and S-phase arrest, as determined by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling and flow cytometry. Consistent with these observations, HOTAIR suppression was associated with tumor shrinkage and restoration of gefitinib sensitivity in RPC-9 xenograft mice. Immunohistochemical analyses and western blot revealed that HOTAIR silencing resulted in the upregulation of B cell lymphoma 2-associated X protein (Bax), Caspase-3 and transforming growth factor α (TGF-α) and downregulation of EGFR and B cell lymphoma 2 (Bcl-2) levels. These results indicate that HOTAIR normally prevents the activation of Bax/Caspase-3 while inducing TGF-α/EGFR signaling. Thus, targeting HOTAIR may be a novel therapeutic strategy for treating gefitinib-resistant lung adenocarcinoma.

Liver X receptors agonist GW3965 re-sensitizes gefitinib-resistant human non-small cell lung cancer cell to gefitinib treatment by inhibiting NF-κB in vitro

The recent research shows that the inhibition of the nuclear factor-κB (NF-κB) pathway is a promising therapeutic option for patients who progress after treatment with the novel mutant-selective EGFR-TKIs. For propose to find a nontoxic drug to reverse the acquired gefitinib resistance, we examined whether the Liver X Receptors agonist GW3965 affect gefitinib resistance of HCC827/GR-8-2 cells. Cell viability was measured by CCK-8 assay. Levels of NF-κB, p-AKT and caspases were detected by Western blot analysis. Immunocytochemical analysis was used to detect the expression of NF-κB, p-AKT intracellularly. Induction of apoptosis and cell cycle arrest was measured by Flow cytometry assay. And results revealed that more than 90% of HCC827/GR-8-2 cells lived upon treatment with gefitinib at a dose of 5μM for 48h. However, when under the combine treatment of GW3965 (5μM) & gefitinib(5μM), cell death rate was increased observably. Co-administration of gefitinib & GW3965 induced cell apoptosis and cell cycle arrest. Additionally, we observed a dose-dependent- down-regulation of NF-κB in HCC827/GR-8-2 cells treated with gefitinib & GW3965. GW3965 and gefitinib synergistically decreased cell proliferation and induced apoptosis by inhibiting NF-κB signaling pathway in gefitinib resistant cells. These findings support our hypothesis that GW3965 could act as a useful drug to reverse the gefitinib resistance.

Epithelial-to-mesenchymal transition correlates with gefitinib resistance in NSCLC cells and the liver X receptor ligand GW3965 reverses gefitinib resistance through inhibition of vimentin

The role of epithelial-to-mesenchymal transition in cancer drug resistance is increasingly acknowledged. We examined whether epithelial-to-mesenchymal transition affects gefitinib resistance in non-small cell lung cancer (NSCLC) cells. Cell viability was detected by CCK-8 assay, VIM expression levels were determined by quantitative real-time polymerase chain reaction. Western blot and immunocytochemistry were performed to determine the protein expression level of vimentin. We observed morphologic differences between gefitinib-sensitive and -insensitive cells. Compared with the sensitive parental cell line, HCC827, vimentin expression levels were increased in HCC827 cells with acquired gefitinib resistance. Vimentin expression was also markedly upregulated in cells with intrinsic gefitinib resistance, and upregulated vimentin expression was correlated with gefitinib sensitivity. Our previous study demonstrated that coadministration of gefitinib and GW3965 resulted in decreased cell proliferation and induced apoptosis. Therefore, we investigated the relationship among GW3965, vimentin, and gefitinib resistance in NSCLC cells by analysis of the expression of vimentin in cells treated with a combination of gefitinib and GW3965. Gefitinib treatment led to increased levels of intracellular vimentin, while combined treatment with gefitinib and GW3965 resulted in decreased vimentin expression levels through reduction of gefitinib drug resistance in NSCLC cells. Overall, these findings suggest that vimentin expression is associated with sensitivity to gefitinib, and our study highlights the potential usefulness of the drug, GW3965, for reversal of gefitinib resistance through inhibition of vimentin expression.

Genome-wide profiling of micro-RNA expression in gefitinib-resistant human lung adenocarcinoma using microarray for the identification of miR-149-5p modulation

To understand the mechanism involved in gefitinib resistance, we established gefitinib-resistant human HCC827/GR-8-1 cell line from the parental HCC827 cell line. We compared the micro-RNA expression profiles of the HCC827 cells HCC827/GR-8-1 using Agilent micro-RNA microarrays. The micro-RNAs, such as the miR-149-5p, were up- or downregulated and associated with acquired gefitinib resistance. Quantitative real-time polymerase chain reaction was then performed to verify the expression patterns of different micro-RNAs. The result showed that miR-149-5p was upregulated in the HCC827/GR-8-1 cell line. To investigate the biological function of miR-149-5p in non-small cell lung cancer cells acquired gefitinib resistance, we examined cell proliferation using a cell counting kit-8 assay. Cell viability was evaluated after the miR-149-5p mimics, inhibitors, and negative control were separately transfected into the non-small cell lung cancer cells. The results showed that the non-small cell lung cancer cells transfected with miR-149-5p mimics exhibited reduced cell motility. The drug-sensitivity assay results revealed that the overexpression of miR-149-5p effectively evaluates the half maximal inhibitory concentration values of the cell in response to gefitinib, and the downregulation of miR-149-5p can attenuate the half maximal inhibitory concentration values of the cell lines in response to gefitinib. Furthermore, the levels of miR-149-5p in the HCC827 and HCC827/GR-8-1 cells were inversely correlated with caspase-3 expression. In conclusion, this study revealed that miR-149-5p is upregulated in the HCC827/GR-8-1 cells and involved in the acquired gefitinib resistance.

Increased MIR31HG lncRNA expression increases gefitinib resistance in non-small cell lung cancer cell lines through the EGFR/PI3K/AKT signaling pathway

The aim of the present study was to gain insight into the molecular mechanism of gefitinib resistance in non-small cell lung cancer (NSCLC), and demonstrate whether long noncoding RNA (lncRNA) expression signatures differ between gefitinib-sensitive PC9 and gefitinib-resistant PC9 (PC9-R) cell lines. PC9 and PC9-R cells were treated with gefitinib and, after 48 h, proliferation and apoptosis were analyzed using a Cell Counting Kit-8 (CCK-8) assay and flow cytometry. Microarray expression profiling of lncRNAs was undertaken in both PC9 and PC9-R cells, and the expression profiles were verified by reverse transcription quantitative-polymerase chain reaction. The EGFR/PI3K/AKT signaling pathway and mitochondrial apoptosis protein expression levels were assessed by western blot analysis. The PC9 cell line treated with gefitinib had a more significant effect on cell viability and apoptosis than the PC9-R cell line (P<0.05). Expression of various lncRNAs differed significantly between the two cell lines, and MIR31HG expression in particular was significantly higher in PC9-R cells. As expected, MIR31HG lncRNA knockdown sensitized PC9-R cells to gefitinib, and further experiments revealed that turning off the EGFR/PI3K/AKT signaling pathway activated expression of p53 in PC9-R cells transfected with si-MIR31HG. Furthermore, PC9-R cells transfected with si-MIR31HG induced cell apoptosis through the mitochondrial apoptosis pathway, and arrested the cell cycle in the G0/G1 phase. The results of the current study suggest that MIR31HG lncRNA levels in PC9-R cells are higher than in PC9 cells. Furthermore, overexpression of MIR31HG lncRNAs may contribute to gefitinib resistance in PC9-R cells through the EGFR/PI3K/AKT pathway, which impacts on cell proliferation, apoptosis and the cell cycle. MIR31HG lncRNA may therefore be a novel candidate biomarker for future therapeutic strategies involving EGFR-TKIs.

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.