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Erlotinib, an epidermal growth factor receptor tyrosine kinase inhibitor (EGFR-TKI), is widely applied as a first-line treatment for non-small cell lung cancer (NSCLC) and greatly improves the clinical outcomes of patients. However, acquired resistance to EGFR-TKIs remains a major clinical challenge. Here, we identified guanylate-binding protein-1 (GBP1) as a novel protein related to erlotinib resistance, and explored the specific mechanism by which GBP1 is involved in erlotinib resistance. First, the human NSCLC cells PC9ER and HCC827ER were generated by exposing cells to increasing concentrations of erlotinib over 6 months. We screened different genes between erlotinib-sensitive and erlotinib-resistant cells with data from the Gene Expression Omnibus database and detected the expression of these genes in erlotinib-resistant and erlotinib-sensitive cells by quantitative real-time polymerase chain reaction (qPCR). Moreover, we constructed GBP1-knockdown and GBP1-overexpressing cells to determine the IC50 value of erlotinib, to perform an apoptosis assay and to examine cell cycle distribution. A subcutaneous tumorigenesis test was used to analyze how GBP1 affects erlotinib resistance. Then, mass spectrometry analysis and coimmunoprecipitation were performed to verify the interaction between GBP1 and phosphoglycerate kinase 1 (PGK1). Changes in epithelial-mesenchymal transition (EMT)-related markers were observed following the upregulation and down-regulation of PGK1 expression. Finally, a rescue experiment was used to determine whether GBP1 regulates EMT through PGK1. In the present study, GBP1 was significantly upregulated in erlotinib-resistant cells, compared with erlotinib-sensitive cells. In vitro and in vivo experiments showed that upregulated GBP1 expression contributed to erlotinib resistance, while decreased GBP1 expression had the opposite effect. As shown by performing survival analysis, high GBP1 expression predicted poor prognosis in patients with lung adenocarcinoma. Furthermore, the interaction between GBP1 and PGK1 was confirmed, and a rescue experiment revealed that GBP1 regulates EMT via PGK1. Finally, functional experiments showed that EMT is involved in erlotinib resistance. Our study suggests that GBP1 regulates erlotinib resistance via PGK1-mediated EMT signaling, suggesting GBP1 as a potential therapeutic target in erlotinib-resistant NSCLC.

Drug resistance restrains the effect of drug therapy in non-small cell lung cancer (NSCLC). However, the mechanism of the acquisition of drug resistance remains largely unknown. This study aims to investigate the effect of exosomal lncRNA H19 on erlotinib resistance in NSCLC and the underlying mechanism. HCC827 and A549 cells were continuously grafted into erlotinib-containing culture medium to establish erlotinib-resistant cell lines. The expression of H19 and miR-615-3p was detected by qRT-PCR. The protein levels of MMP2, MMP9, CD9, CD63 and ATG7 were measured by Western blot. Cell viability and proliferation were determined by Cell Counting Kit-8 (CCK-8) and 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide (MTT) assay, respectively. Migration and invasion were assessed by transwell assay. Xenograft tumor models were used to investigate the effect of H19 on erlotinib resistance in vivo. Online software and dual-luciferase reporter assay were used to predicate the downstream targets and confirm the targeted relationships. H19 was upregulated in erlotinib-resistant cells, and knockdown of H19 inhibited cell proliferation, migration and invasion in erlotinib-resistant cells. Extracellular H19 can be packaged into exosomes. Exosomes containing H19 induced erlotinib resistance of sensitive cells, while knockdown of H19 abolished this effect. miR-615-3p was a target of H19 and can bind to ATG7. Exosomal H19 affected erlotinib resistance of erlotinib-resistant NSCLC cells via targeting miR-615-3p to regulate ATG7 expression. In addition, the serum exosomal H19 was upregulated in patients with erlotinib resistance. Furthermore, downregulated H19 decreased the resistance of tumor cells to erlotinib in vivo. Our study demonstrated that exosomal H19 facilitated erlotinib resistance in NSCLC via miR-615-3p/ATG7 axis, which might provide a potential target for the diagnosis and treatment of NSCLC.

Epidermal growth factor receptor (EGFR) is a pivotal therapeutic target in pancreatic ductal adenocarcinoma (PDAC); however, the clinical efficacy of tyrosine kinase inhibitors (TKIs) such as erlotinib is frequently curtailed by acquired resistance. This study identifies histone deacetylase 1 (HDAC1) as a critical epigenetic driver of this resistance. HDAC1 is markedly upregulated in erlotinib-resistant PDAC cells, where it directly suppresses the transcriptional activity of TFCP2 through site-specific deacetylation at lysine 256 (K256). This modification attenuates TFCP2 function, leading to transcriptional repression of the metastasis suppressor NDRG1 and increased expression of EGFR, thereby activating EGFR-TKI resistance signaling pathways. Furthermore, EGFR-mediated tyrosine phosphorylation protects HDAC1 from ubiquitin-proteasome system (UPS)-dependent degradation, stabilizing HDAC1 and establishing a self-reinforcing feedback loop that sustains its elevated expression in the resistant state. To counter this mechanism, we designed a bioactive peptide derived from TFCP2 that competitively inhibits K256 deacetylation, thereby restoring TFCP2 transcriptional activity. In and in studies demonstrate that pharmacological inhibition of HDAC1 or restoration of TFCP2 acetylation reverses erlotinib resistance in PDAC. These findings unveil a previously unrecognized mechanism of EGFR-TKI resistance and suggest a promising strategy to enhance therapeutic efficacy in PDAC.

Acquired resistance to epidermal growth factor receptor (EGFR)-tyrosine kinase inhibitors (TKIs) such as erlotinib is a major challenge to achieve an overall clinical benefit of the targeted therapy. Recently, aldehyde dehydrogenase 1 (ALDH1) induction has been found to render lung adenocarcinomas resistant to EGFR-TKIs, and targeting ALDH1A1 becomes a novel strategy to overcome resistance. However, the molecular mechanism underlying such effect remains poorly understood. Comprehensive assays were performed in a panel of lung adenocarcinoma cell lines and xenografts that acquired resistance to erlotinib. Cancer phenotype was evaluated by cell viability, apoptosis, migration, and epithelial-mesenchymal transition analysis , tumorsphere formation analysis , and tumor growth and dissemination analysis . Reactive oxygen species (ROS) and reactive carbonyl species (RCS) were detected based on fluorescent oxidation indicator and liquid chromatography coupled to mass spectrometry, respectively. Protein target was suppressed by RNA interference and pharmacological inhibition or ecto-overexpressed by lentivirus-based cloning. Gene promoter activity was measured by dual-luciferase reporting assay. Knockdown or pharmacological inhibition of ALDH1A1 overcame erlotinib resistance and . ALDH1A1 overexpression was sufficient to induce erlotinib resistance. Metabolomic analysis demonstrated lower ROS-RCS levels in ALDH1A1-addicted, erlotinib-resistant cells; in line with this, key enzymes for metabolizing ROS and RCS, SOD2 and GPX4, respectively, were upregulated in these cells. Knockdown of SOD2 or GPX4 re-sensitized the resistant cells to erlotinib and the effect was abrogated by ROS-RCS scavenging and mimicked by ROS-RCS induction. The ALDH1A1 overexpressed cells, though resisted erlotinib, were more sensitive to SOD2 or GPX4 knockdown. The ALDH1A1 effect on erlotinib resistance was abrogated by ROS-RCS induction and mimicked by ROS-RCS scavenging. Detection of GPX4 and SOD2 expression and analysis of promoter activities of GPX4 and SOD2 under the condition of suppression or overexpression of ALDH1A1 demonstrated that the RCS-ROS-metabolic pathway was controlled by the ALDH1A1-GPX4-SOD2 axis. The ROS-RCS metabolic dependence mechanism in ALDH1A1-induced resistance was confirmed . Analysis of public databases showed that in patients undergoing chemotherapy, those with high co-expression of ALDH1A1, GPX4, and SOD2 had a lower probability of survival. ALDH1A1 confers erlotinib resistance by facilitating the ROS-RCS metabolic pathway. ALDH1A1-induced upregulation of SOD2 and GPX4, as well as ALDH1A1 itself, mitigated erlotinib-induced oxidative and carbonyl stress, and imparted the TKI resistance. The elucidation of previously unrecognized metabolic mechanism underlying erlotinib resistance provides new insight into the biology of molecular targeted therapies and help to design improved pharmacological strategies to overcome the drug resistance.

Calcium signaling is critical in tumorigenesis. This study analyzed the characteristics of a calcium-related prognostic genes (CRPGs) signature in lung adenocarcinoma (LUAD) for prognostic value and explored as a potential therapeutic target for erlotinib resistance. Clinical and RNA sequencing data from LUAD patients were obtained from the TCGA and GEO databases. CRPGs were identified through univariate Cox and Kaplan-Meier survival analyses. Calcium-related subtypes were determined via unsupervised clustering. A prognostic signature was constructed and validated using external datasets. Differences in immune infiltration and potential mechanisms in LUAD were explored using seven algorithms. The relationship between signature genes, chemotherapy sensitivity, and potential targeted therapies was evaluated. Potential drug targets were identified using Mendelian randomization (MR) and phenome-wide association studies (PheWAS). The association between , erlotinib resistance, and macrophage M2 polarization was investigated through experiments. The study identified 33 CRPGs and four subtypes among LUAD patients. The prognostic signature, comprising nine CRPGs, accurately predicted 1-, 2-, and 3-year overall survival. was identified as a crucial tumor suppressor gene and potential drug target. Down-regulation of decreased the IC value of erlotinib in LUAD cells and inhibited macrophage M2 polarization. This study developed a reliable prognostic signature based on nine CRPGs for predicting LUAD patient outcomes. may enhance LUAD cell resistance to erlotinib through macrophage polarization to the M2 phenotype.

The aim of this study was to investigate the anti-angiogenic effects of the hexane fraction of Adenophora triphylla var. japonica root extract (HAT) and its influence on the development of erlotinib resistance in human lung cancer cells. HAT significantly reduced the migration, invasion, and tube formation of human umbilical vein endothelial cells (HUVECs). The phosphorylation levels of vascular endothelial growth factor receptor 2 (VEGFR2) and its downstream molecules were decreased via HAT, indicating its anti-angiogenic potential in endothelial cells (ECs). A docking analysis demonstrated that β-sitosterol and lupeol, representative components of HAT, exhibit a high affinity for binding to VEGFR2. In addition, conditioned media from HAT-pretreated H1299 human lung cancer cells attenuated cancer-cell-induced chemotaxis of HUVECs, which was attributed to the decreased expression of angiogenic and chemotactic factors in H1299 cells. Interestingly, co-culture of erlotinib-sensitive PC9 human lung cancer cells with HUVECs induced erlotinib resistance in PC9 cells. However, co-culture with HAT-pretreated HUVECs partially restored the sensitivity of PC9 cells to erlotinib. HAT inhibited the development of erlotinib resistance by attenuating hepatocyte growth factor (HGF) production by ECs. Taken together, our results demonstrate that HAT exerts its anticancer effects by regulating the crosstalk between ECs and lung cancer cells.

Here, we discovered that targeting cell cycle processes or protein ubiquitination pathways are promising treatment strategies for overcoming resistance to EGFR inhibitors in lung cancer using a genome‐scale CRISPR‐Cas9 screening. Combination therapies targeting each of these two processes such as nutlin‐3 and carfilzomib increased cancer cell death when combined with erlotinib in both in vitro and in vivo experiments. Erlotinib is highly effective in lung cancer patients with epidermal growth factor receptor (EGFR) mutations. However, despite initial favorable responses, most patients rapidly develop resistance to erlotinib soon after the initial treatment. This study aims to identify new genes and pathways associated with erlotinib resistance mechanisms in order to develop novel therapeutic strategies. Here, we induced knockout (KO) mutations in erlotinib‐resistant human lung cancer cells (NCI‐H820) using a genome‐scale CRISPR‐Cas9 sgRNA library to screen for genes involved in erlotinib susceptibility. The spectrum of sgRNAs incorporated among erlotinib‐treated cells was substantially different to that of the untreated cells. Gene set analyses showed a significant depletion of ‘cell cycle process’ and ‘protein ubiquitination pathway’ genes among erlotinib‐treated cells. Chemical inhibitors targeting genes in these two pathways, such as nutlin‐3 and carfilzomib, increased cancer cell death when combined with erlotinib in both in vitro cell line and in vivo patient‐derived xenograft experiments. Therefore, we propose that targeting cell cycle processes or protein ubiquitination pathways are promising treatment strategies for overcoming resistance to EGFR inhibitors in lung cancer.

Background Epidermal growth factor receptor- tyrosine kinase inhibitors (EGFR-TKIs) benefit Non-small cell lung cancer (NSCLC) patients, and an EGFR-TKIi erlotinib, is approved for patients with recurrent NSCLC. However, resistance to erlotinib is a major clinical problem. Earlier we have demonstrated the role of Hedgehog (Hh) signaling in Epithelial-to-Mesenchymal transition (EMT) of NSCLC cells, leading to increased proliferation and invasion. Here, we investigated the role of Hh signaling in erlotinib resistance of TGF-β1-induced NSCLC cells that are reminiscent of EMT cells. Methods Hh signaling was inhibited by specific siRNA and by GDC-0449, a small molecule antagonist of G protein coupled receptor smoothened in the Hh pathway. Not all NSCLC patients are likely to benefit from EGFR-TKIs and, therefore, cisplatin was used to further demonstrate a role of inhibition of Hh signaling in sensitization of resistant EMT cells. Specific pre- and anti-miRNA preparations were used to study the mechanistic involvement of miRNAs in drug resistance mechanism. Results siRNA-mediated inhibition as well as pharmacological inhibition of Hh signaling abrogated resistance of NSCLC cells to erlotinib and cisplatin. It also resulted in re-sensitization of TGF-β1-induced A549 (A549M) cells as well the mesenchymal phenotypic H1299 cells to erlotinib and cisplatin treatment with concomitant up-regulation of cancer stem cell (CSC) markers (Sox2, Nanog and EpCAM) and down-regulation of miR-200 and let-7 family miRNAs. Ectopic up-regulation of miRNAs, especially miR-200b and let-7c, significantly diminished the erlotinib resistance of A549M cells. Inhibition of Hh signaling by GDC-0449 in EMT cells resulted in the attenuation of CSC markers and up-regulation of miR-200b and let-7c, leading to sensitization of EMT cells to drug treatment, thus, confirming a connection between Hh signaling, miRNAs and drug resistance. Conclusions We demonstrate that Hh pathway, through EMT-induction, leads to reduced sensitivity to EGFR-TKIs in NSCLCs. Therefore, targeting Hh pathway may lead to the reversal of EMT phenotype and improve the therapeutic efficacy of EGFR-TKIs in NSCLC patients.

Epidermal growth receptor (EGFR)‐targeted tyrosine kinase inhibitors (TKIs) have emerged as first‐line drugs for advanced non‐small‐cell lung cancer (NSCLC) patients with EFGR mutations. However, most patients with NSCLC show acquired resistance to EGFR‐TKIs, and low expression of NF1 is a mechanism of EGFR‐TKI resistance in lung cancer. However, the mechanism by which NF1 is downregulated in EGFR‐TKI‐resistant NSCLC is unclear. Here, we found the increased expression of miR‐641 in NSCLC cells and human NSCLC samples with resistance to TKI compared to those with sensitive to TKI. In addition, our in vitro experiments show that overexpression of miR‐641 induces TKI resistance in NSCLC cells. Furthermore, we identified that miR‐641 activates ERK signaling by direct targeting of neurofibromatosis 1 (NF1) in NSCLC cells. Our data show that overexpression of NF1 or silencing of ERK can block miR‐641‐induced resistance of NSCLC cells to erlotinib treatment. Importantly, our animal experiments show that combination of miR‐641 inhibition and erlotinib treatment can significantly inhibit erlotinib‐resistant NSCLC growth, inhibit proliferation and induce apoptosis compared to single‐drug treatment. Our findings suggest that increased expression of miR‐641 significantly contributes to erlotinib resistance development in NSCLC cells through activating ERK signaling by targeting NF1 and that inhibition of miR‐641 may reverse acquired resistance of NSCLC cells to erlotinib treatment. We first time determined the role of miR‐641 on the erlotinib resistance development in NSCLC cells. Our findings suggest that upregulated expression of miR‐641 was significantly associated with erlotinib resistance development in NSCLC cells. Our findings may also aid in the development of potential therapeutics for the treatment of erlotinib‐resistant NSCLC.

Acquired resistance to epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs), such as erlotinib, remains a major challenge in the targeted therapy of non-small cell lung cancer (NSCLC). HKB99 is a novel allosteric inhibitor of phosphoglycerate mutase 1 (PGAM1) that preferentially suppresses cell proliferation and induces more apoptosis in acquired erlotinib-resistant HCC827ER cells compared with its parental HCC827 cells. In this study we identified the molecular biomarkers for HKB99 response in erlotinib-resistant HCC827ER cells. We showed that HCC827ER cells displayed enhanced invasive pseudopodia structures as well as downregulated plasminogen activator inhibitor-2 (PAI-2). Meanwhile, PAI-2 knockdown by siPAI-2 candidates decreased the sensitivity of HCC827 parental cells to erlotinib. Moreover, HKB99 (5 μM) preferentially inhibited the invasive pseudopodia formation and increased the level of PAI-2 in HCC827ER cells. Collectively, this study provides new insight into the role of PAI-2 in regulating the sensitivity of erlotinib resistant NSCLC cells to PGAM1 inhibitor. Furthermore, PAI-2 level might be considered as a potential biomarker for predicting the efficacy of the PGAM1 allosteric inhibitor on the erlotinib resistant NSCLC cells.