Cyclosporine A sensitizes human non-small cell lung cancer cells to gefitinib through inhibition of STAT3

PPP3CB overexpression mediates EGFR TKI resistance in lung tumors via calcineurin/MEK/ERK signaling

Despite initial high response rates to first-line EGFR TKI, all non-small-cell lung cancer (NSCLC) with EGFR-activating mutation will ultimately develop resistance to treatment. Identification of resistance mechanisms is critical to adapt treatment and improve patient outcomes. Here, we show that a PPP3CB transcript that encodes full-length catalytic subunit 2B of calcineurin accumulates in EGFR-mutant NSCLC cells with acquired resistance against different EGFR TKIs and in post-progression biopsies of NSCLC patients treated with EGFR TKIs. Neutralization of PPP3CB by siRNA or inactivation of calcineurin by cyclosporin A induces apoptosis in resistant cells treated with EGFR TKIs. Mechanistically, EGFR TKIs increase the cytosolic level of calcium and trigger activation of a calcineurin/MEK/ERK pathway that prevents apoptosis. Combining EGFR, calcineurin, and MEK inhibitors overcomes resistance to EGFR TKI in both in vitro and in vivo models. Our results identify PPP3CB overexpression as a new mechanism of acquired resistance to EGFR TKIs, and provide a promising therapeutic approach for NSCLC patients that progress under TKI treatment.

Inhibitors to degraders: Changing paradigm in drug discovery

The chemical understanding of biological processes provides not only a deeper insight but also a solution to abnormal biological functioning. Protein degradation, a natural biological process for debris removal in the cell, has been studied for years. The recent finding that natural degradation pathways can be utilized for therapeutic purposes is a paradigm shift in the drug discovery approach. Methods such as Proteolysis Targeting Chimera (PROTAC), lysosomal targeting chimera, hydrophobic tagging, AUtophagy TArgeting Chimera, AUTOphagy TArgeting Chimera and several other variants of these methods have made a considerable impact on the way of drug design. Few selected examples testify that a huge wave of change is on the way. The drug design based on the targeted protein degradation is a powerful tool in our arsenal. More molecules will be invented that will uncover the hidden secrets of biological functioning and provide enduring solutions to several unmet medical needs.

Relevance and mechanism of STAT3/miR-221-3p/Fascin-1 axis in EGFR TKI resistance of triple-negative breast cancer

The epidermal growth factor receptor 1 (EGFR) plays a crucial role in the progression of various malignant tumors and is considered a potential target for treating triple-negative breast cancer (TNBC). However, the effectiveness of representative tyrosine kinase inhibitors (TKIs) used in EGFR-targeted therapy is limited in TNBC patients. In our study, we observed that the TNBC cell lines MDA-MB-231 and MDA-MB-468 exhibited resistance to Gefitinib. Treatment with Gefitinib caused an upregulation of Fascin-1 (FSCN1) protein expression and a downregulation of miR-221-3p in these cell lines. However, sensitivity to Gefitinib was significantly improved in both cell lines with either inhibition of FSCN1 expression or overexpression of miR-221-3p. Our luciferase reporter assay confirmed that FSCN1 is a target of miR-221-3p. Moreover, Gefitinib treatment resulted in an upregulation of phosphorylated signal transducer and activator of transcription 3 (p-STAT3) in MDA-MB-231 cells. Using Stattic, a small-molecule inhibitor of STAT3, we observed a significant enhancement in the inhibitory effect of Gefitinib on the growth, migration, and invasion of MDA-MB-231 cells. Additionally, Stattic treatment upregulated miR-221-3p expression and downregulated FSCN1 mRNA and protein expression. A strong positive correlation was noted between the expression of STAT3 and FSCN1 in breast cancer tissues. Furthermore, patients with high expression levels of both STAT3 and FSCN1 had a worse prognosis. Our findings suggest that elevated FSCN1 expression is linked to primary resistance to EGFR TKIs in TNBC. Moreover, we propose that STAT3 regulates the expression of miR-221-3p/FSCN1 and therefore modulates resistance to EGFR TKI therapy in TNBC. Combining EGFR TKI therapy with inhibition of FSCN1 or STAT3 may offer a promising new therapeutic option for TNBC.

Lung cancer treatment potential and limits associated with the STAT family of transcription factors

Lung cancer is one of the mortal cancers and the leading cause of cancer-related mortality, with a cancer survival rate of fewer than 5% in developing nations. This low survival rate can be linked to things like late-stage detection, quick postoperative recurrences in patients receiving therapy, and chemoresistance developing against various lung cancer treatments. Signal transducer and activator of transcription (STAT) family of transcription factors are involved in lung cancer cell proliferation, metastasis, immunological control, and treatment resistance. By interacting with specific DNA sequences, STAT proteins trigger the production of particular genes, which in turn result in adaptive and incredibly specific biological responses. In the human genome, seven STAT proteins have been discovered (STAT1 to STAT6, including STAT5a and STAT5b). Many external signaling proteins can activate unphosphorylated STATs (uSTATs), which are found inactively in the cytoplasm. When STAT proteins are activated, they can increase the transcription of several target genes, which leads to unchecked cellular proliferation, anti-apoptotic reactions, and angiogenesis. The effects of STAT transcription factors on lung cancer are variable; some are either pro- or anti-tumorigenic, while others maintain dual, context-dependent activities. Here, we give a succinct summary of the various functions that each member of the STAT family plays in lung cancer and go into more detail about the advantages and disadvantages of pharmacologically targeting STAT proteins and their upstream activators in the context of lung cancer treatment.

Natural Cyclophilin A Inhibitors Suppress the Growth of Cancer Stem Cells in Non-Small Cell Lung Cancer by Disrupting Crosstalk between CypA/CD147 and EGFR

Non-small cell lung cancer (NSCLC) is a fatal malignant tumor with a high mortality rate. Cancer stem cells (CSCs) play pivotal roles in tumor initiation and progression, treatment resistance, and NSCLC recurrence. Therefore, the development of novel therapeutic targets and anticancer drugs that effectively block CSC growth may improve treatment outcomes in patients with NSCLC. In this study, we evaluated, for the first time, the effects of natural cyclophilin A (CypA) inhibitors, including 23-demethyl 8,13-deoxynargenicin (C9) and cyclosporin A (CsA), on the growth of NSCLC CSCs. C9 and CsA more sensitively inhibited the proliferation of epidermal growth factor receptor (EGFR)-mutant NSCLC CSCs than EGFR wild-type NSCLC CSCs. Both compounds suppressed the self-renewal ability of NSCLC CSCs and NSCLC-CSC-derived tumor growth in vivo. Furthermore, C9 and CsA inhibited NSCLC CSC growth by activating the intrinsic apoptotic pathway. Notably, C9 and CsA reduced the expression levels of major CSC markers, including integrin α6, CD133, CD44, ALDH1A1, Nanog, Oct4, and Sox2, through dual downregulation of the CypA/CD147 axis and EGFR activity in NSCLC CSCs. Our results also show that the EGFR tyrosine kinase inhibitor afatinib inactivated EGFR and decreased the expression levels of CypA and CD147 in NSCLC CSCs, suggesting close crosstalk between the CypA/CD147 and EGFR pathways in regulating NSCLC CSC growth. In addition, combined treatment with afatinib and C9 or CsA more potently inhibited the growth of EGFR-mutant NSCLC CSCs than single-compound treatments. These findings suggest that the natural CypA inhibitors C9 and CsA are potential anticancer agents that suppress the growth of EGFR-mutant NSCLC CSCs, either as monotherapy or in combination with afatinib, by interfering with the crosstalk between CypA/CD147 and EGFR.

Reprogramming of TAMs via the STAT3/CD47-SIRPα axis promotes acquired resistance to EGFR-TKIs in lung cancer

Cross-talk between the tumor microenvironment (TME) and cancer cells plays an important role in acquired drug resistance to epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs). The role of tumor-associated macrophages (TAMs), the major component of the TME, in acquired resistance remains unclear. In this study, M2-like reprogramming of TAMs and reduced phagocytosis by macrophages were observed in gefitinib-resistant lung cancer cells and tumor xenografts. CD47 was upregulated in TKI-resistant lung cancer cells, and M2 macrophage polarization and cancer cell escape from macrophage phagocytosis were enhanced. Culture medium from TKI-resistant cells led to metabolic reprogramming of TAMs. STAT3 was associated with CD47 expression in TKI-resistant lung cancer cells. Genetic and pharmacological inhibition of STAT3 enhanced the phagocytic activity of TAMs and alleviated the acquired resistance to EGFR-TKIs via inhibiting the CD47-SIRPα signaling axis and M2 polarization in the co-culture system. Moreover, STAT3 transcriptionally regulated CD47 expression by binding to consensus DNA response elements in the intron of the CD47 gene. Furthermore, the combination of gefitinib with a STAT3 inhibitor and an anti-CD47 monoclonal antibody alleviated the acquired resistance to gefitinib in vitro and in vivo. Collectively, our study reveals the role of TAM reprogramming and the CD47-SIRPα axis in acquired EGFR-TKI resistance and provides a novel therapeutic strategy to overcome the acquired resistance to EGFR-TKIs in lung cancer.

A novel alkaloid compound, DCZ0358, exerts significant antitumor activity in bortezomib-resistant multiple myeloma cells through inhibition of JAK2/STAT3 pathway

Multiple myeloma (MM), the second most common haematological malignancy, is currently incurable because patients often develop multiple drug resistance and experience subsequent relapse of the disease. This study aims to identify a potential therapeutic agent that can counter bortezomib (BTZ) resistance in MM. DCZ0358, a novel alkaloid compound, is found to exert potent cytotoxic effects against BTZ-resistant MM cells in vivo and in vitro. The anti-myeloma activity of DCZ0358 is associated with inhibition of cell proliferation, promotion of cell apoptosis via caspase-mediated apoptotic pathways, and induction of G0/G1 phase arrest via downregulation of cyclin D1, CDK4, and CDK6. Further investigation of the molecular mechanism shows that DCZ0358 suppresses the JAK2/STAT3 signaling pathway. In conclusion, DCZ0358 can successfully counter BTZ resistance in MM cells. This study provides evidence that warrants future preclinical assessments of DCZ0358 as a therapeutic agent against BTZ resistance in MM.

STAT3 promotes RNA polymerase III-directed transcription by controlling the miR-106a-5p/TP73 axis

Deregulation of Pol III products causes a range of diseases, including neural diseases and cancers. However, the factors and mechanisms that modulate Pol III-directed transcription remain to be found, although massive advances have been achieved. Here, we show that STAT3 positively regulates the activities of Pol III-dependent transcription and cancer cell growth. RNA-seq analysis revealed that STAT3 inhibits the expression of TP73, a member of the p53 family. We found that TP73 is not only required for the regulation of Pol III-directed transcription mediated by STAT3 but also independently suppresses the synthesis of Pol III products. Mechanistically, TP73 can disrupt the assembly of TFIIIB subunits and inhibit their occupancies at Pol III target loci by interacting with TFIIIB subunit TBP. MiR-106a-5p can activate Pol III-directed transcription by targeting the TP73 mRNA 3' UTR to reduce TP 73 expression. We show that STAT3 activates the expression of miR-106a-5p by binding to the miRNA promoter, indicating that the miR-106a-5p links STAT3 with TP73 to regulate Pol III-directed transcription. Collectively, these findings indicate that STAT3 functions as a positive regulator in Pol III-directed transcription by controlling the miR-106a-5p/TP73 axis.

Central Roles of STAT3-Mediated Signals in Onset and Development of Cancers: Tumorigenesis and Immunosurveillance

Since the time of Rudolf Virchow in the 19th century, it has been well-known that cancer-associated inflammation contributes to tumor initiation and progression. However, it remains unclear whether a collapse of the balance between the antitumor immune response via the immunological surveillance system and protumor immunity due to cancer-related inflammation is responsible for cancer malignancy. The majority of inflammatory signals affect tumorigenesis by activating signal transducer and activation of transcription 3 (STAT3) and nuclear factor-κB. Persistent STAT3 activation in malignant cancer cells mediates extremely widespread functions, including cell growth, survival, angiogenesis, and invasion and contributes to an increase in inflammation-associated tumorigenesis. In addition, intracellular STAT3 activation in immune cells causes suppressive effects on antitumor immunity and leads to the differentiation and mobilization of immature myeloid-derived cells and tumor-associated macrophages. In many cancer types, STAT3 does not directly rely on its activation by oncogenic mutations but has important oncogenic and malignant transformation-associated functions in both cancer and stromal cells in the tumor microenvironment (TME). We have reported a series of studies aiming towards understanding the molecular mechanisms underlying the proliferation of various types of tumors involving signal-transducing adaptor protein-2 as an adaptor molecule that modulates STAT3 activity, and we recently found that AT-rich interactive domain-containing protein 5a functions as an mRNA stabilizer that orchestrates an immunosuppressive TME in malignant mesenchymal tumors. In this review, we summarize recent advances in our understanding of the functional role of STAT3 in tumor progression and introduce novel molecular mechanisms of cancer development and malignant transformation involving STAT3 activation that we have identified to date. Finally, we discuss potential therapeutic strategies for cancer that target the signaling pathway to augment STAT3 activity.

Cyclosporine A Downregulates Selenoprotein P Expression via a Signal Transducer and Activator of Transcription 3-Forkhead Box Protein O1 Pathway in Hepatocytes In Vitro

Cyclosporine A (CsA) is an immunosuppressant applied worldwide for preventing graft rejection and autoimmune diseases. However, CsA elevates oxidative stress, which can lead to liver injuries. The present study aimed to clarify the mechanisms underlying the CsA-mediated oxidative stress. Among the redox proteins, CsA concentration-dependently downregulated Selenop-encoding selenoprotein P, a major circulating antioxidant protein reducing reactive oxygen species, in hepatocytes cell lines and primary hepatocytes. The luciferase assay identified the CsA-responsive element in the SELENOP promoter containing a putative binding site for forkhead box protein O (FoxO) 1. The CsA-mediated suppression on the SELENOP promoter was independent of the nuclear factor of activated T-cell, a classic target repressed by CsA. A chromatin immunoprecipitation assay showed that CsA suppressed the FoxO1 binding to the SELENOP promoter. Foxo1 knockdown significantly downregulated Selenop expression in H4IIEC3 cells. Furthermore, CsA downregulated FoxO1 by inactivating its upstream signal transducer and activator of transcription 3 (STAT3). Knockdown of Stat3 downregulated Foxo1 and Selenop expression in hepatocytes. These findings revealed a novel mechanism underlying CsA-induced oxidative stress by downregulating the STAT3-FoxO1-Selenop pathway in hepatocytes. SIGNIFICANCE STATEMENT: This study shows that Cyclosporine A (CsA) downregulates Selenop, an antioxidant protein, by suppressing the signal transducer and activator of transcription 3-forkhead box protein O1 pathway in hepatocytes, possibly one of the causations of CsA-induced oxidative stress in hepatocytes. The present study sheds light on the previously unrecognized CsA-redox axis.

Cyclosporine A downregulates selenoprotein P expression via a STAT3-FoxO1 pathway in hepatocytes in vitro

Cyclosporine A (CsA) is a worldwide applied immunosuppressant for preventing graft rejection and autoimmune diseases. However, CsA elevates oxidative stress leading to liver injuries. The present study aimed to clarify the mechanisms underlying the CsA-mediated oxidative stress. Among the redox proteins, CsA concentration-dependently downregulated Selenop encoding selenoprotein P (SeP), a major circulating antioxidant protein reducing reactive oxygen species (ROS), in hepatocytes cell lines and primary hepatocytes. The luciferase assay identified the CsA-responsive element in the SELENOP promoter containing a putative binding site for FoxO1. The CsA-mediated suppression on the SELENOP promoter was independent of NFAT, a classic target repressed by CsA. A ChIP assay showed that CsA suppressed the FoxO1 binding to the SELENOP promoter. Foxo1 knockdown significantly downregulated Selenop expression in H4IIEC3 cells. Furthermore, CsA downregulated FoxO1 by inactivating its upstream signal transducer and activator of transcription 3 (STAT3). Knockdown of Stat3 downregulated Foxo1 and Selenop expression in hepatocytes. These findings revealed a novel mechanism underlying CsA-induced oxidative stress via downregulating the STAT3-FoxO1-Selenop pathway in hepatocytes. Significance Statement Our study shows that CsA downregulates Selenop, an antioxidant protein, via suppressing the STAT3-FoxO1 pathway in hepatocytes, possibly one of the causations of CsA-induced oxidative stress in hepatocytes. The present study sheds light on the previously unrecognized CsA-redox axis.

Glycyrrhizin as a Nitric Oxide Regulator in Cancer Chemotherapy

Simple Summary

Glycyrrhizin (GL) has anti-cancer, anti-inflammatory, anti-viral, and anti-oxidant activity. In particular, GL reduces multidrug resistance (MDR) in cancer cells, which is a major obstacle to chemotherapy. Nitric oxide (NO) also plays an important role in MDR, and GL affects NO concentration in the tumor microenvironment. However, the effects of GL and NO interaction on MDR have not been reviewed. Here, we review the role of GL as an NO regulator in cancer cells and its subsequent anti-MDR effect and posit that GL is a promising MDR inhibitor for cancer chemotherapy.

Abstract

Chemotherapy is used widely for cancer treatment; however, the evolution of multidrug resistance (MDR) in many patients limits the therapeutic benefits of chemotherapy. It is important to overcome MDR for enhanced chemotherapy. ATP-dependent efflux of drugs out of cells is the main mechanism of MDR. Recent studies have suggested that nitric oxide (NO) can be used to overcome MDR by inhibiting the ATPase function of ATP-dependent pumps. Several attempts have been made to deliver NO to the tumor microenvironment (TME), however there are limitations in delivery. Glycyrrhizin (GL), an active compound of licorice, has been reported to both reduce the MDR effect by inhibiting ATP-dependent pumps and function as a regulator of NO production in the TME. In this review, we describe the potential role of GL as an NO regulator and MDR inhibitor that efficiently reduces the MDR effect in cancer chemotherapy.

PAR2 blockade reverses osimertinib resistance in non-small-cell lung cancer cells via attenuating ERK-mediated EMT and PD-L1 expression

Osimertinib, as the third-generation EGFR tyrosine kinase inhibitors (EGFR-TKIs), is a first-line molecularly targeted drug for non-small cell lung cancer (NSCLC). However, the emergence of therapeutic resistance to osimertinib markedly impairs its efficiency and efficacy, leading to the failure of clinical applications. Novel molecular targets and drugs are urgently needed for reversing osimertinib resistance in NSCLC. Protease-activated receptor 2 (PAR2) that belongs to a subfamily of G protein-coupled receptors can stimulate the transactivation of EGFR to regulate multiple cellular signalling, actively participating in tumour progression. This study firstly discovered that PAR2 expression was notably enhanced when NSCLC cells became resistant to osimertinib. A PAR2 inhibitor facilitated osimertinib to attenuate EGFR transactivation, ERK phosphorylation, EMT and PD-L1 expression which were associated to osimertinib resistance. The combination of the PAR2 inhibitor and osimertinib also notably blocked cell viability, migration, 3D sphere formation and in vivo tumour growth whereas osimertinib itself lost such inhibitory effects in osimertinib-resistant NSCLC cells. Importantly, this reversal effect of PAR2 blockade was uncovered to depend on ERK-mediated EMT and PD-L1, since inhibition of β-arrestin or ERK, which could be modulated by PAR2, sensitized osimertinib to prevent EMT, PD-L1 expression and consequently overcame osimertinib resistance. Thus, this study demonstrated that PAR2 antagonism could limit ERK-mediated EMT and immune checkpoints, consequently attenuating EGFR transactivation and reactivate osimertinib. It suggested that PAR2 may be a novel drug target for osimertinib resistance, and PAR2 inhibition may be a promising strategy candidate for reversing EGFR-TKI resistance in NSCLC.

Chemotherapy: a double-edged sword in cancer treatment

Chemotherapy is a well-known and effective treatment for different cancers; unfortunately, it has not been as efficient in the eradication of all cancer cells as been expected. The mechanism of this failure was not fully clarified, yet. Meanwhile, alterations in the physiologic conditions of the tumor microenvironment (TME) were suggested as one of the underlying possibilities. Chemotherapy drugs can activate multiple signaling pathways and augment the secretion of inflammatory mediators. Inflammation may show two opposite roles in the TME. On the one hand, inflammation, as an innate immune response, tries to suppress tumor growth but on the other hand, it might be not powerful enough to eradicate the cancer cells and even it can provide appropriate conditions for cancer promotion and relapse as well. Therefore, the administration of mild anti-inflammatory drugs during chemotherapy might result in more successful clinical results. Here, we will review and discuss this hypothesis. Most chemotherapy agents are triggers of inflammation in the tumor microenvironment through inducing the production of senescence-associated secretory phenotype (SASP) molecules. Some chemotherapy agents can induce systematic inflammation by provoking TLR4 signaling or triggering IL-1B secretion through the inflammasome pathway. NF-kB and MAPK are key signaling pathways of inflammation and could be activated by several chemotherapy drugs. Furthermore, inflammation can play a key role in cancer development, metastasis and exacerbation.

Discovery and development of tumor glycolysis rate-limiting enzyme inhibitors

Tumor cells mainly provide necessary energy and substances for rapid cell growth through aerobic perglycolysis rather than oxidative phosphorylation. This phenomenon is called the "Warburg effect". The mechanism of glycolysis in tumor cells is more complicated, which is caused by the comprehensive regulation of multiple factors. Abnormal enzyme metabolism is one of the main influencing factors and inhibiting the three main rate-limiting enzymes in glycolysis is thought to be important strategy for cancer treatment. Therefore, numerous inhibitors of glycolysis rate-limiting enzyme have been developed in recent years, such as the latest HKII inhibitor and PKM2 inhibitor Pachymic acid (PA) and N-(4-(3-(3-(methylamino)-3-oxopropyl)-5-(4'-(trifluoromethyl)-[1,1'-biphenyl]-4-yl)-1H-pyrazol-1-yl)phenyl)propiolamide. The review focuses on source, structure-activity relationship, bioecological activity and mechanism of the three main rate-limiting enzymes inhibitors, and hopes to guide the future research on the design and synthesis of rate-limiting enzyme inhibitors.

Strategies for Targeting Serine/Threonine Protein Phosphatases with Small Molecules in Cancer

Among numerous posttranslational regulation patterns, phosphorylation is reversibly controlled by the balance of kinases and phosphatases. The major form of cellular signaling involves the reversible phosphorylation of proteins on tyrosine, serine, or threonine residues. However, altered phosphorylation levels are found in diverse diseases, including cancer, making kinases and phosphatases ideal drug targets. In contrast to the success of prosperous kinase inhibitors, design of small molecules targeting phosphatase is struggling due to past bias and difficulty. This is especially true for serine/threonine phosphatases, one of the largest phosphatase families. From this perspective, we aim to provide insights into serine/threonine phosphatases and the small molecules targeting these proteins for drug development, especially in cancer. Through highlighting the modulation strategies, we aim to provide basic principles for the design of small molecules and future perspectives for the application of drugs targeting serine/threonine phosphatases.

Targeting PAR2 Overcomes Gefitinib Resistance in Non-Small-Cell Lung Cancer Cells Through Inhibition of EGFR Transactivation

Drug resistance can notably restrict clinical applications of gefitinib that is a commonly used EGFR-tyrosine kinase inhibitors (EGFR-TKIs) for non-small cell lung cancer (NSCLC). The attempts in exploring novel drug targets and reversal strategies are still needed, since gefitinib resistance has not been fully addressed. Protease-activated receptor 2 (PAR2), a G protein-coupled receptor, possesses a transactivation with EGFR to initiate a variety of intracellular signal transductions, but there is a lack of investigations on the role of PAR2 in gefitinib resistance. This study established that protease-activated receptor 2 (PAR2), actively participated in NSCLC resistant to gefitinib. PAR2 expression was significantly up-regulated when NSCLC cells or tumor tissues became gefitinib resistance. PAR2 inhibition notably enhanced gefitinib to modulate EGFR transactivation, cell viability, migration and apoptosis in gefitinib-sensitive and-resistant NSCLC cells, suggesting its reversal effects in gefitinib resistance. Meanwhile, the combination of a PAR2 inhibitor (P2pal-18S) and gefitinib largely blocked ERK phosphorylation and epithelial-mesenchymal transition (EMT) compared to gefitinib alone. Importantly, we probed its underlying mechanism and uncovered that PAR2 blockade sensitized gefitinib and reversed its resistance mainly via β-arrestin-EGFR-ERK signaling axis. These effects of PAR2 inhibition were further confirmed by the in vivo study which showed that P2pal-18S reactivated gefitinib to inhibit tumor growth via restricting ERK activation. Taken together, this study could not only reveal a new mechanism of receptor-mediated transactivation to modulate drug resistance, but also provide a novel drug target and direction for overcoming gefitinib resistance in NSCLC.

EGFR mutation mediates resistance to EGFR tyrosine kinase inhibitors in NSCLC: From molecular mechanisms to clinical research

With the development of precision medicine, molecular targeted therapy has been widely used in the field of cancer, especially in non-small-cell lung cancer (NSCLC). Epidermal growth factor receptor (EGFR) is a well-recognized and effective target for NSCLC therapies, targeted EGFR therapy with EGFR-tyrosine kinase inhibitors (EGFR-TKIs) has achieved ideal clinical efficacy in recent years. Unfortunately, resistance to EGFR-TKIs inevitably occurs due to various mechanisms after a period of therapy. EGFR mutations, such as T790M and C797S, are the most common mechanism of EGFR-TKI resistance. Here, we discuss the mechanisms of EGFR-TKIs resistance induced by secondary EGFR mutations, highlight the development of targeted drugs to overcome EGFR mutation-mediated resistance, and predict the promising directions for development of novel candidates.

Antitumour immunity regulated by aberrant ERBB family signalling

Aberrant signalling of ERBB family members plays an important role in tumorigenesis and in the escape from antitumour immunity in multiple malignancies. Molecular-targeted agents against these signalling pathways exhibit robust clinical efficacy, but patients inevitably experience acquired resistance to these molecular-targeted therapies. Although cancer immunotherapies, including immune checkpoint inhibitors (ICIs), have shown durable antitumour response in a subset of the treated patients in multiple cancer types, clinical efficacy is limited in cancers harbouring activating gene alterations of ERBB family members. In particular, ICI treatment of patients with non-small cell lung cancers with epidermal growth factor receptor (EGFR) alterations and breast cancers with HER2 alterations failed to show clinical benefits, suggesting that EGFR and HER2 signalling may have an essential role in inhibiting antitumour immune responses. Here, we discuss the mechanisms by which the signalling of ERBB family members affects not only autonomous cancer hallmarks, such as uncontrolled cell proliferation, but also antitumour immune responses in the tumour microenvironment and the potential application of immune-genome precision medicine into immunotherapy and molecular-targeted therapy focusing on the signalling of ERBB family members.

Cryptotanshinone strengthens the effect of gefitinib against non-small cell lung cancer through inhibiting transketolase

Lung cancer is the leading cause of cancer-related mortality and causes more than a million deaths per year. Gefitinib is the first-line agent of advanced lung cancer, however, resistance to gefitinib becomes a major problem in clinical application. Transketolase (TKT) is a key enzyme functioning between the oxidative arm and the non-oxidative arm of the pentose phosphate pathway. In this study, we firstly found that the expression of TKT was remarkably up-regulated in NSCLC cells, while the knockdown of TKT could inhibit cell proliferation and enhance the effect of gefitinib on NSCLC cells, which indicated the role of TKT in treating advanced lung cancer. Cryptotanshinone (CTS) is a natural active compound possessing anti-cancer effect. Here we demonstrated that CTS could strengthen the effect of gefitinib on NSCLC cells via inhibition of TKT in vitro and in vivo. Moreover, Nrf2 was involved in the repression of CTS on TKT expression. Collectively, these findings indicated the role of TKT in lung cancer progression and may provide novel therapeutic strategies to overcome resistance to gefitinib. Furthermore, CTS may serve as a new candidate in adjuvant treatment of advanced lung cancer.

A novel STAT3 inhibitor W2014-S regresses human non-small cell lung cancer xenografts and sensitizes EGFR-TKI acquired resistance

Constitutive activation of signal transducer and activator of transcription 3 (STAT3) is a common feature in human non-small cell lung cancer (NSCLC). STAT3 plays an important role in cancer progression as a driver oncogene and acquired resistance of targeted therapies as an alternatively activated pathway. W2014-S with pharmacophore structure of imidazopyridine, which was firstly reported to be utilized in STAT3 inhibitor discovery, was screened out as a potent STAT3 inhibitor from a library of small molecules. The aim of this study is to investigate the antitumor activities and mechanisms of W2014-S in NSCLC and effect on epidermal growth factor receptor-tyrosine kinase inhibitors (EGFR-TKIs) resistance in vitro and in vivo. Methods: SPR analysis, Co-immunoprecipitation, confocal microscope imaging, and luciferase report gene assays were utilized to determine the mechanisms. Cell viability, colonial survival, wound healing, cell invasion assay, human cancer cell xenografts and PDX tumor xenografts were used to determine antitumor activities. Results: W2014-S disrupted STAT3 dimerization and selectively inhibited aberrant STAT3 signaling in NSCLC cell line. W2014-S strongly suppressed proliferation, survival, migration and invasion of lung cancer cells with aberrant STAT3 activation and inhibited the growth of human NSCLC cell xenografts and PDX tumor xenografts in mouse model. Furthermore, W2014-S significantly sensitized resistant NSCLC cell line to gefitinib and erlotinib in vitro and enhances the anti-tumor effect of gefitinib in TKI-resistant lung cancer xenografts in vivo. Conclusions: Our study has provided a novel STAT3 inhibitor with significant anti-tumor activities in NSCLC and suggests that combination of STAT3 inhibitor such as W2014-S with gefitinib could serve as a promising strategy to overcome EGFR-TKIs acquired resistance in NSCLC patients.

Analyses of putative anti-cancer potential of three STAT3 signaling inhibitory compounds derived from Salvia officinalis

The extract of Salvia officinalis (Common Sage) exhibited inhibitory activity of STAT3 signal after screening of several plants extracts using the STAT3-responsive reporter system. Cirsiliol, luteolin, and carnosol were identified from the methanol extract of Silvia officinalis as inhibitors of STAT3 signaling and the effects of these three compounds on STAT3 protein or growth inhibition on cancer cells was compared. Luteolin at the dose of 90 μM clearly suppressed the phosphorylation of STAT3 induced by IL-6, while carnosol was prone to decrease total STAT3 proteins at high doses (>90 μM). Cirsiliol had almost no effect. Since the three compounds exhibited similar concentration-dependent suppression patterns in the reporter assay except for cirsiliol became plateau beyond 30 μM, these compounds appeared to function as STAT3 inhibitory factors in different ways. The direct anti-proliferative activity of three compounds was examined with or without the anti-cancer drug gefitinib using HepG2 and A549 cells. The anti-proliferative effect of the three compounds was additively enhanced by gefitinib. At the doses of 3.6 μM, statistically significant suppression of proliferation was observed in HepG2 cells only by cirsiliol among the three compounds in the absence of gefitinib but all three compounds were prone to suppress the proliferation of HepG2 cells and A549 cells dose-dependently although cirsiliol showed a modest dose-dependency and this suppression of proliferation was enhanced by the addition of gefitinib. Cirsiliol, a dimethyoxylated flavone, activated the natural killer activity of KHYG-1 cells against erythroleukemia K562 cells like a hexamethoxylated flavone, nobiletin, suggesting that it may also have an indirect anti-cancer potential through activation of NK cells. These results shed light on the putative anti-cancer potential of Salvia officinalis.

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Carnosol, luteolin and cirsiliol were identified as STAT3 signal inhibitors in S. officinalis.

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Cirsiliol inhibited the STAT3-responsive reporter expression at 7.5 μM but showed low dose-dependency at higher doses.

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Cirsiliol at 90 μM showed almost no effect on phosphorylation of STAT3 and weakly suppressed total STAT3.

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Cirsiliol exhibited anti-proliferative activity at 3.6 μM against HepG2 cells and A549 cells but showed low dose-dependency.

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Cirsiliol activated NK cells by stimulating exocytosis of granules for cytolysis.

Inhibition of JNK-Mediated Autophagy Promotes Proscillaridin A- Induced Apoptosis via ROS Generation, Intracellular Ca+2 Oscillation and Inhibiting STAT3 Signaling in Breast Cancer Cells

Breast cancer is the most heterogenous cancer type among women across the world. Despite concerted efforts, breast cancer management is still unsatisfactory. Interplay between apoptosis and autophagy is an imperative factor in categorizing therapeutics for cancer treatment. Proscillaridin A (PSD-A), a well-known cardiac glycoside used for cardiac arrest and arrythmias, has been unveiled in many cancer types but the underlying mechanism for apoptosis and autophagy in breast cancer is not fully understood. In our study, PSD-A restricted cell growth, inhibited STAT3 activation and induced apoptosis and autophagy in breast cancer cells via ROS generation and Ca⁺² oscillation. Pretreatment of NAC and BAPTA-AM restored PSD-A induced cellular events in breast cancer cells. PSD-A induced apoptosis via DNA fragmentation, caspase-cascade activation, PARP cleavage, mitochondrial dysfunction, Bax/Bcl-2 proteins modulation and ER chaperone GRP78 inhibition along with decreased phosphorylation of ERK1/2. Inhibition of STAT3 activation was found to be associated with decreased phosphorylation of SRC. Moreover, PSD-A induced events of autophagy i.e. conversion of LC3-I to LC3-II, and Atg3 expression via JNK activation and decreased mTOR and AKT phosphorylation. In this study, pretreatment of SP600125, a JNK inhibitor, reduced autophagy and enhanced STAT3 inhibition and apoptosis. Additionally, SB203580, a commercial p38 inhibitor, stimulated STAT3 activation and improved autophagic events rate in breast cancer cells, displaying the role of the MAPK signaling pathway in interplay between apoptosis and autophagy. Our data suggest that the rate of apoptotic cell death is improved by blocking JNK-induced autophagy in PSD-A treated MCF-7 and MDA-MB-231 breast cancer cells.

RPL32 Promotes Lung Cancer Progression by Facilitating p53 Degradation

Lung cancer is the leading cause of cancer death worldwide, and the overall survival rate of advanced lung cancer patients is unsatisfactory. Ribosomal proteins (RPs) play important roles in carcinogenesis. However, the role of RPL32 in lung cancer has not been demonstrated. Here, we report that RPL32 is aberrantly, highly expressed in lung cancer tissues and that the overexpression of RPL32 is correlated with the poor prognosis of these patients. RPL32 silencing significantly inhibited the proliferation of lung cancer cells, with an observed p53 accumulation and cell-cycle arrest. Mechanistically, knockdown of RPL32 resulted in ribosomal stress and affected rRNA maturation. RPL5 and RPL11 sensed stress and translocated from the nucleus to the nucleoplasm, where they bound to murine double minute 2 (MDM2), an important p53 E3 ubiquitin ligase, which resulted in p53 accumulation and inhibition of cancer cell proliferation. As lung cancer cells usually express high levels of Toll-like receptor 9 (TLR9), we conjugated RPL32 small interfering RNA (siRNA) to the TLR9 ligand CpG to generate CpG-RPL32 siRNA, which could stabilize and guide RPL32 siRNA to lung cancer cells. Excitingly, CpG-RPL32 siRNA displayed strong anticancer abilities in lung cancer xenografts. Therefore, RPL32 is expected to be a potential target for lung cancer treatment.

NHE1 Mediates 5-Fu Resistance in Gastric Cancer via STAT3 Signaling Pathway

BACKGROUND

Several recent studies have addressed the role of Na+/H+ exchanger isoform 1 (NHE1) in tumor cell growth and apoptosis, including in gastric cancer. However, the role of NHE1 expression related to the 5-Fu resistance in gastric cancer has not been investigated.

METHODS

The expression of NHE1 was examined by qPCR in the SGC7901/5-FU cell line and its parental cell line. pcDNA3.1-NHE1 and NHE1-siRNA were transfected to SGC7901/5-FU resistance cells and cell apoptosis was detected via TUNEL assay. The upstream activators in NHE1 mediated 5-Fu resistant gastric cancer cells were detected by Western blot and immunofluorescent.

RESULTS

A significant increase of the expression of NHE1 was observed in SGC7901 5-FU resistance cells compared to the GES-1 and SGC7901 cell line. NHE1 can suppress the cell apoptosis of SGC7901 5-FU resistance cells and involved in cell cycle. Also, the migration and invasion of SGC7901 5-FU resistance cells were promoted by NHE1. NHE1 also increases the intracellular pH. The results of Western blot analysis showed that NHE1 overexpression induced an increase in the expression of phosphorylated activator transcription factor 3 (pSTAT3). The more obvious phosphorylated level was shown in the phosphorylated STAT3 at pSTAT3tyr705. Further investigations revealed that the constitutive activation of STAT3 may be induced by JAK1 and JAK2, and thus effect the 5-FU resistance by regulating NHE1.

DISCUSSION

In summary, our findings provided evidence that NHE1 contributed to 5-Fu resistance in gastric cancer cells by regulating the JAK/STAT3 pathway. Therefore, NHE1 can be a useful marker for predicting and monitoring 5-Fu resistance.

Ginsenoside Rk1 induces apoptosis and downregulates the expression of PD-L1 by targeting the NF-κB pathway in lung adenocarcinoma

Ginsenoside Rk1 can function as an antitumor modulator that induces apoptosis in lung adenocarcinoma cells by inhibiting NF-κB transcription and triggering cell cycle arrest.

Novel activators and small-molecule inhibitors of STAT3 in cancer

Excessive activation of signal transducer and activator of transcription 3 (STAT3) signaling is observed in a subset of many cancers, making activated STAT3 a highly promising potential therapeutic target supported by multiple preclinical and clinical studies. However, early-phase clinical trials have produced mixed results with STAT3-targeted cancer therapies, revealing substantial complexity to targeting aberrant STAT3 signaling. This review discusses the diverse mechanisms of oncogenic activation of STAT3, and the small molecule inhibitors of STAT3 in cancer treatment.

Novel ADAM-17 inhibitor ZLDI-8 inhibits the proliferation and metastasis of chemo-resistant non-small-cell lung cancer by reversing Notch and epithelial mesenchymal transition in vitro and in vivo

Acquired drug-resistant non-small cell lung cancer (NSCLC) has strong proliferation ability and is prone to epithelial-mesenchymal transition (EMT) and subsequent metastasis. Notch pathway mediates cell survival and EMT and is involved in the induction of multidrug resistance (MDR). ZLDI-8 is an inhibitor of Notch activating/cleaving enzyme ADAM-17 we found before. However, the effects of ZLDI-8 on resistant NSCLC was unclear. Here, we demonstrated for the first time that ZLDI-8 could induce apoptosis in lung cancer, especially in chemotherapy-resistant non-small cell lung cancer cells, and also inhibit migration, invasion and EMT phenotype of drug-resistant lung cancer. ZLDI-8 inhibits the Notch signaling pathway, thereby regulating the expression of survival/apoptosis and EMT-related proteins. Moreover, ZLDI-8 suppresses multidrug-resistant lung cancer xenograft growth in vivo and blocks metastasis in a tail vein injection mice model. Therefore, ZLDI-8 is expected to be an effective agent in the treatment of drug-resistant lung cancer.

EGFR TKIs impair lysosome-dependent degradation of SQSTM1 to compromise the effectiveness in lung cancer

Tyrosine kinase inhibitors for epidermal growth factor receptor (EGFR TKIs) greatly improved clinical outcomes of patients with non-small cell lung cancer (NSCLC). Unfortunately, primary and acquired resistance limits their clinical benefits. To overcome such resistance, new generations of EGFR TKIs have been developed by targeting newly identified mutations in EGFR. However, much less effort has been put into alternative strategies, such as targeting the intrinsic protective responses to EGFR TKIs. In this study, we found that EGFR TKIs, including gefitinib and AZD9291, impaired lysosome-dependent degradation of SQSTM1, thus compromising their anti-cancer efficiency. By accumulating in the lysosome lumen, gefitinib and AZD9291 attenuated lysosomal acidification and impaired autolysosomal degradation of SQSTM1 owing to their intrinsic alkalinity. As a result, SQSTM1 protein was stabilized in response to gefitinib and AZD9291 treatment and conferred EGFR TKI resistance. Depleting SQSTM1 significantly increased the sensitivity of NSCLC cells to gefitinib and AZD9291 both in vitro and in vivo. Furthermore, a chemically modified gefitinib analog lacking alkalinity displayed stronger inhibitory effects on NSCLC cells. Therefore, targeting accumulated SQSTM1 or chemically modified EGFR TKIs may represent new strategies to increase the effectiveness of EGFR targeted therapy.

Cyclosporine A Suppresses the Malignant Progression of Oral Squamous Cell Carcinoma in vitro

Background:

The Oral Squamous Cell Carcinoma (OSCC) is one of the most frequent cancer types. Failure of treatment of OSCC is potentially lethal because of local recurrence, regional lymph node metastasis, and distant metastasis. Chemotherapy plays a vital role through suppression of tumorigenesis. Cyclosporine A (CsA), an immunosuppressant drug, has been efficiently used in allograft organ transplant recipients to prevent rejection, and also has been used in a subset of patients with autoimmunity related disorders. The present study aims to investigate novel and effective chemotherapeutic drugs to overcome drug-resistance in the treatment of OSCC.

Methods:

Cells were incubated in the standard way. Cell viability was assayed using the MTT assay. Cell proliferation was determined using colony formation assay. The cell cycle assay was performed using flow cytometry. Apoptosis was assessed using fluorescence-activated cell sorting after stained by the Annexin V-fluorescein isothiocyanate (FITC). Cell migration and invasion were analyzed using wound healing assay and tranwell. The effect of COX-2, c-Myc, MMP-9, MMP-2, and NFATc1 protein expression was determined using Western blot analysis while NFATc1 mRNA expression was determined by RT-PCR.

Results:

In vitro studies indicated that CsA inhibited partial OSCC growth by inducing cell cycle arrest, apoptosis, and the migration and invasion of OSCC cells. We also demonstrated that CsA could inhibit the expression of NFATc1 and its downstream genes COX-2, c-Myc, MMP-9, and MMP-2 in OSCC cells. Furthermore, we analyzed the expression of NFATc1 in head and neck cancer through the Oncomine database. The data was consistent with the experimental findings.

Conclusion:

The present study initially demonstrated that CsA could inhibit the progression of OSCC cells and can mediate the signal molecules of NFATc1 signaling pathway, which has strong relationship with cancer development. That explains us CsA has potential to explore the possibilities as a novel chemotherapeutic drug for the treatment of OSCC.

Cyclosporine A sensitizes lung cancer cells to crizotinib through inhibition of the Ca2+/calcineurin/Erk pathway

Background

Crizotinib has potent anti-tumor activity in patients with advanced MET-amplified non-small cell lung cancer (NSCLC). However, the therapeutic effect is still not satisfying. Thus, developing approaches that improve the efficacy of crizotinib remains a significant challenge.

Methods

MET-amplified NSCLC cell lines were treated with crizotinib and cyclosporine A (CsA). Cell viability was determined by MTS assay. The changes of apoptosis, cell cycle and calcineurin-Erk pathways were assessed by western blot. Xenograft mouse model, primary human NSCLC cells and hollow fiber assays were utilized to confirm the effects of CsA.

Findings

We demonstrated that CsA significantly increased the anti-tumor effect of crizotinib on multiple MET-amplified NSCLC cells in vitro and in vivo. Mechanistically, crizotinib treatment led to the activation of Ca²⁺-calcineurin (CaN)-Kinase suppressor of Ras 2 (KSR2) signaling, resulting in Erk1/2 activation and enhanced survival of cancer cells. CsA effectively blocked CaN-KSR2-Erk1/2 signaling, promoting crizotinib-induced apoptosis and G2/M arrest. Similarly, pharmacologic or genetic inhibition of Erk1/2 also enhanced crizotinib-induced growth inhibition in vitro. Xenograft studies further confirmed that CsA or Erk1/2 inhibitor PD98059 enhanced the anti-cancer activity of crizotinib through inhibition of CaN-Erk1/2 axis. The results were also validated by primary human NSCLC cells in vitro and hollow fiber assays in vivo.

Interpretation

This study provides preclinical evidences that combination therapy of CsA and crizotinib is a promising approach for targeted treatment of MET-amplified lung cancer patients.

Fund

This work was supported by the National Natural Science Foundation of China, the Key Projects of Natural Foundation of Zhejiang Province, the Ten thousand plan youth talent support program of Zhejiang Province, the Zhejiang Natural Sciences Foundation Grant, and the Zhejiang medical innovative discipline construction project-2016.

Daurinoline suppressed the migration and invasion of chemo-resistant human non-small cell lung cancer cells by reversing EMT and Notch-1 and sensitized the cells to Taxol

Non-small cell lung cancer (NSCLC) is one of the most common malignancies, and Taxol is a cornerstone in the treatment. However, taxol-resistance eventually limits the clinical effects and applications. Daurinoline could restore the sensitivity of resistant MCF-7/adr and KBv200 cells. Whereas, the effect of daurinoline on the chemo-resistant NSCLC cells and the mechanism has not been elucidated. In this study, daurinoline was firstly demonstrated that inhibited the proliferation, migration, invasion and EMT phenotype of chemo-resistant NSCLC cells. And these effects were associated with EMT and Notch-1 reversal. Moreover, daurinoline could significantly enhance the anti-tumor effect of Taxol rather than epirubicin, adriamycin and cisplatin. And the reverse fold (RF) value of daurinoline was greater than terfenadine reported before. There are little cytotoxic effects of daurinoline and its derivatives reported by L.W. Fu, et al. (2001). Therefore, daurinoline may be a potential anti-tumor agent or chemosensitizer for chemo-resistant NSCLC patients.

A nanomedicine approach enables co-delivery of cyclosporin A and gefitinib to potentiate the therapeutic efficacy in drug-resistant lung cancer

Drug resistance, accounting for therapeutic failure in the clinic, remains a major challenge to effectively manage cancer. Cyclosporin A (CsA) can reverse multidrug resistance (MDR), especially resistance to epidermal growth factor receptor tyrosine kinase inhibitors. However, the application of both drugs in cancer therapies is hampered by their poor aqueous solubility and low bioavailability due to oral administration. CsA augments the potency of gefitinib (Gef) in both Gef-sensitive and Gef-resistant cell lines. Here, we show that the simultaneous encapsulation of CsA and Gef within polyethylene glycol-block-poly(_{D, L}-lactic acid) (PEG-PLA) produced a stable and systemically injectable nanomedicine, which exhibited a sub-50-nm diameter and spherical structures. Impressively, the co-delivery of therapeutics via single nanoparticles (NPs) outperformed the oral administration of the free drug combination at suppressing tumor growth. Furthermore, in vivo results indicated that CsA formulated in NPs sensitized Gef-resistant cells and Gef-resistant tumors to Gef treatment by inactivating the STAT3/Bcl-2 signaling pathway. Collectively, our nanomedicine approach not only provides an alternative administration route for the drugs of choice but also effectively reverses MDR, facilitating the development of effective therapeutic modalities for cancer.

Injection of nanoparticles containing the anticancer drug gefitinib and the immunosuppressant cyclosporin A reverses drug-resistant cancer growth in mice. The development of multidrug resistance is the main reason why many forms of chemotherapy fail. Cyclosporin A, a drug used to prevent immune rejection after organ transplantation, has previously been shown to enhance the potency of gefitinib. Hangxiang Wang and colleagues at Zhejiang University, Hangzhou, China, have successfully combined cyclosporin A and gefitinib, two poorly water-soluble and slowly absorbed drugs, into stable injectable nanoparticles that delay the growth of gefitinib resistant human lung cancer cells as well as the growth of drug resistant tumors in mice. Importantly, this novel co-formulation was more effective than oral co-administration of the two drugs. Further investigation into this drug delivery route could yield much needed alternative treatments for patients with multidrug-resistant cancers.

Proliferating cell nuclear antigen promotes cell proliferation and tumorigenesis by up-regulating STAT3 in non-small cell lung cancer

Proliferating cell nuclear antigen (PCNA) functions as a bridging molecule, which targets proteins that have distinct roles in cell growth. The expression of PCNA is dysregulated in some tumors and takes part in the progression of oncogenesis. However, the roles of PCNA in the progression of non-small cell lung cancer (NSCLC) remain unknown. The present study aimed to investigate the function of PCNA in the occurrence and development of NSCLC and its underlying molecular mechanisms. Western blotting, RT-PCR, and immunohistochemistry assays were used to detect the expression pattern of PCNA in NSCLC tissues and cells. A log rank test was performed to compare the overall survival (OS) of patients with high/low expression of PCNA. Besides, the relationship between PCNA and signal transducer and activator of transcription-3 (STAT3) proteins were evaluated. Then, MTT, flow cytometry, clonal formation, and in vivo xenograft assays were conducted to investigate the effects of PCNA/STAT3 on cell growth, clonal formation, apoptosis, and tumorigenesis. Results showed that PCNA expression was elevated in NSCLC tissues and cells and it could combine with STAT3 and increased its expression and phosphorylation. Moreover, the expression of PCNA showed a positive correlation with the TNM grade and occurrence rate of the lymphatic metastasis and poor prognosis of NSCLC patients. Overexpression of PCNA promoted cell proliferation, clonal formation, and tumorigenesis in lung cancer cells and inhibited cell apoptosis. In contrast, these effects were inhibited when knockdown of STAT3. In conclusion, this study demonstrates that PCNA functions as an oncogene in the progression of NSCLC through up-regulation of STAT3. These findings point to a potentially new therapeutic strategy for NSCLC.

Ex Vivo Cardiotoxicity of Antineoplastic Casiopeinas Is Mediated through Energetic Dysfunction and Triggered Mitochondrial-Dependent Apoptosis

Casiopeinas are a group of copper-based antineoplastic molecules designed as a less toxic and more therapeutic alternative to cisplatin or Doxorubicin; however, there is scarce evidence about their toxic effects on the whole heart and cardiomyocytes. Given this, rat hearts were perfused with Casiopeinas or Doxorubicin and the effects on mechanical performance, energetics, and mitochondrial function were measured. As well, the effects of Casiopeinas-triggered cell death were explored in isolated cardiomyocytes. Casiopeinas III-Ea, II-gly, and III-ia induced a progressive and sustained inhibition of heart contractile function that was dose- and time-dependent with an IC₅₀ of 1.3 ± 0.2, 5.5 ± 0.5, and 10 ± 0.7 μM, correspondingly. Myocardial oxygen consumption was not modified at their respective IC₅₀, although ATP levels were significantly reduced, indicating energy impairment. Isolated mitochondria from Casiopeinas-treated hearts showed a significant loss of membrane potential and reduction of mitochondrial Ca²⁺ retention capacity. Interestingly, Cyclosporine A inhibited Casiopeinas-induced mitochondrial Ca²⁺ release, which suggests the involvement of the mitochondrial permeability transition pore opening. In addition, Casiopeinas reduced the viability of cardiomyocytes and stimulated the activation of caspases 3, 7, and 9, demonstrating a cell death mitochondrial-dependent mechanism. Finally, the early perfusion of Cyclosporine A in isolated hearts decreased Casiopeinas-induced dysfunction with reduction of their toxic effect. Our results suggest that heart cardiotoxicity of Casiopeinas is similar to that of Doxorubicin, involving heart mitochondrial dysfunction, loss of membrane potential, changes in energetic metabolites, and apoptosis triggered by mitochondrial permeability.

U-box ubiquitin ligase PPIL2 suppresses breast cancer invasion and metastasis by altering cell morphology and promoting SNAI1 ubiquitination and degradation

Metastasis is the leading cause of breast cancer fatalities. To develop new therapeutic strategies, the mechanisms underlying breast cancer invasion and metastasis need to be further investigated. Peptidylprolyl isomerase (cyclophilin)-like 2 (PPIL2) is a U-box-type E3 ubiquitin ligase belonging to the cyclophilin family. Proteins within this family are the major cytosolic binding proteins of the immunosuppressant drug cyclosporine A (CsA). Although PPIL2 has been reported to potentially be involved in cell migration, its role in breast cancer is still unclear. Herein, we demonstrate that PPIL2 suppressed metastasis in a breast cancer model by altering cell morphology and suppressing the epithelial–mesenchymal transition (EMT) process. Moreover, elevated PPIL2 inhibited EMT and breast cancer invasion by interacting with the classical EMT transcription factor, SNAI1, to enhance its ubiquitin-dependent degradation. Furthermore, PPIL2 protein level and stability was upregulated after CsA treatment, indicating that PPIL2 might be involved in CsA-mediated repression of EMT in breast cancer. Analysis of tissue samples taken from breast cancer patients showed a significant correlation between the expression of PPIL2 and the degree of cancer invasion and metastasis. In summary, these results would shed light on a potential clinical use of CsA in breast cancer patients.

Understanding and targeting resistance mechanisms in NSCLC

The expanding spectrum of both established and candidate oncogenic driver mutations identified in non-small-cell lung cancer (NSCLC), coupled with the increasing number of clinically available signal transduction pathway inhibitors targeting these driver mutations, offers a tremendous opportunity to enhance patient outcomes. Despite these molecular advances, advanced-stage NSCLC remains largely incurable due to therapeutic resistance. In this Review, we discuss alterations in the targeted oncogene ('on-target' resistance) and in other downstream and parallel pathways ('off-target' resistance) leading to resistance to targeted therapies in NSCLC, and we provide an overview of the current understanding of the bidirectional interactions with the tumour microenvironment that promote therapeutic resistance. We highlight common mechanistic themes underpinning resistance to targeted therapies that are shared by NSCLC subtypes, including those with oncogenic alterations in epidermal growth factor receptor (EGFR), anaplastic lymphoma kinase (ALK), ROS1 proto-oncogene receptor tyrosine kinase (ROS1), serine/threonine-protein kinase b-raf (BRAF) and other less established oncoproteins. Finally, we discuss how understanding these themes can inform therapeutic strategies, including combination therapy approaches, and overcome the challenge of tumour heterogeneity.

MMPP Attenuates Non-Small Cell Lung Cancer Growth by Inhibiting the STAT3 DNA-Binding Activity via Direct Binding to the STAT3 DNA-Binding Domain

Rationale: Signal transducer and activator of transcription-3 (STAT3) plays a pivotal role in cancer biology. Many small-molecule inhibitors that target STAT3 have been developed as potential anticancer drugs. While designing small-molecule inhibitors that target the SH2 domain of STAT3 remains the leading focus for drug discovery, there has been a growing interest in targeting the DNA-binding domain (DBD) of the protein. Methods: We demonstrated the potential antitumor activity of a novel, small-molecule (E)-2-methoxy-4-(3-(4-methoxyphenyl)prop-1-en-1-yl)phenol (MMPP) that directly binds to the DBD of STAT3, in patient-derived non-small cell lung cancer (NSCLC) xenograft model as well as in NCI-H460 cell xenograft model in nude mice. Results: MMPP effectively inhibited the phosphorylation of STAT3 and its DNA binding activity in vitro and in vivo. It induced G1-phase cell cycle arrest and apoptosis through the regulation of cell cycle- and apoptosis-regulating genes by directly binding to the hydroxyl residue of threonine 456 in the DBD of STAT3. Furthermore, MMPP showed a similar or better antitumor activity than that of docetaxel or cisplatin. Conclusion: MMPP is suggested to be a potential candidate for further development as an anticancer drug that targets the DBD of STAT3.

STAT3 signaling mediates tumour resistance to EGFR targeted therapeutics

Several EGFR inhibitors are currently undergoing clinical assessment or are approved for the clinical management of patients with varying tumour types. However, treatment often results in a lack of response in many patients. The majority of patients that initially respond eventually present with tumours that display acquired resistance to the original therapy. A large number of receptor tyrosine and intracellular kinases have been implicated in driving signaling that mediates this tumour resistance to anti-EGFR targeted therapy, and in a few cases these discoveries have led to overall changes in prospective tumour screening and clinical practice (K-RAS in mCRC and EGFR T790M in NSCLC). In this mini-review, we specifically focus on the role of the STAT3 signaling axis in providing both intrinsic and acquired resistance to inhibitors of the EGFR. We also focus on STAT3 pathway targeting in an attempt to overcome resistance to anti-EGFR therapeutics.

Correlation between p-STAT3 overexpression and prognosis in lung cancer: A systematic review and meta-analysis

Objective

Previous studies have shown the correlation between p-STAT3 overexpression and prognosis in a variety of human tumors. However, their correlation in lung cancer remains controversial. We performed a systematic review and meta-analysis to explore the correlation between p-STAT3 overexpression and prognosis in lung cancer patients.

Methods

We searched PubMed, Embase, Web of Science, CNKI, VIP, and WanFang Data to identify relevant studies. Two reviewers independently screened the literature search results, extracted data, and assessed the methodological quality of the included studies. Then, meta-analysis was performed by using Review Manager 5.3 and STATA 14 software. A random-effect model was employed to evaluate all related pooled results. Statistical heterogeneity of each study was assessed by I². Publication bias was determined by funnel plot and the Begg’s or Egger’s tests.

Results

Eventually, 13 studies were included in present meta-analysis. Among these 13 studies, 8 studies were associated with the overall survival of lung cancer and 10 studies with other clinicopathological characteristics. The results of this meta-analysis suggested that p-STAT3 overexpression may be a poor prognosis biomarker in lung cancer (HR: 1.23; 95% CI: 1.04–1.46; P = 0.02). In terms of other clinicopathological characteristics, p-STAT3 overexpression was more frequent to advanced TNM stages ranging from III to IV (OR: 1.92; 95% CI: 1.13–3.27; P = 0.02) and lymphatic node metastasis (OR: 1.81; 95% CI: 1.20–2.72; P = 0.004). But, it was not associated with tumor differentiation (OR: 0.82; 95% CI: 0.44–1.53; P = 0.54).

Conclusion

p-STAT3 overexpression has significant correlation with poorer overall survival of lung cancer patients, as well as with more advanced TNM stages and lymph node metastasis. Thus, it may serve a biomarker for poor prognosis in lung cancer. Nevertheless, our findings should be confirmed by large prospective studies.

Terfenadine combined with epirubicin impedes the chemo-resistant human non-small cell lung cancer both in vitro and in vivo through EMT and Notch reversal

The acquired resistance of non-small cell lung cancer (NSCLC) to taxanes eventually leads to the recurrence and metastasis of tumours. Thus, the development of therapeutic strategies based on the mechanisms by which cells acquire resistance to prolong their survival rate in chemotherapy drug treatment failure patients are warranted. In this study, we found that the resistant cells acquired increased migratory and invasive capabilities, and this transformation was correlated with epithelial-mesenchymal transition (EMT) and Notch pathway deregulation in the resistant cells. Finally, we reported for the first time that terfenadine augmented the effect of epirubicin (EPI) better than Taxol and cisplatin (DDP) by inhibiting migration, invasion, and the EMT phenotype, and the combination therapy also reversed Notch signalling pathway and enhanced the accumulation of fluorescent P-gp substrate rhodamine 123 (Rh123). Similar activities of terfenadine on EPI were observed in xenografts. All of our results confirmed that terfenadine combined with EPI synergistically inhibits the growth and metastatic processes of resistant cells both in vitro and in vivo. Therefore, terfenadine or its derivatives are a promising approach for the clinical challenge of resistance in patients with advanced NSCLC.

Alantolactone induces apoptosis, promotes STAT3 glutathionylation and enhances chemosensitivity of A549 lung adenocarcinoma cells to doxorubicin via oxidative stress

Alantolactone (ALT), a sesquiterpene lactone component of Inula helenium, has been reported to exert anticancer activity in various cancers. However, the cellular targets and underlying mechanism of anticancer activity of ALT in various cancers including lung cancer has not been fully defined. In the present study, we found that ALT effectively inhibits proliferation and triggers oxidative stress mediated-apoptosis in A549 lung adenocarcinoma cells by inducing ER stress and mitochondrial dysfunction. This ALT-mediated apoptosis was inhibited by NAC while diamide potentiated it. Moreover, ALT effectively suppressed both constitutive and inducible STAT3 activation, inhibited its translocation into nucleus and decreased its DNA binding activity. Further mechanistic study revealed that ALT abrogated STAT3 activation by promoting STAT3 glutathionylation. ROS scavenger NAC reverted ALT-mediated STAT3 glutathionylation and inhibition of STAT3 phosphorylation. Finally, ALT enhanced chemosensitivity of A549 cells to doxorubicin and reversed doxorubicin resistance in A549/DR cells by inhibiting STAT3 activation and P-glycoprotein expression and increasing intracellular accumulation of doxorubicin. Suppression of STAT3 activation by targeting ROS metabolism with ALT thus discloses a previously unrecognized mechanism underlying the biological activity of ALT. Taken together; ALT induces oxidative stress-dependent apoptosis, inhibits STAT3 activation and augments doxorubicin toxicity in A549 lung cancer cells. These findings provide an in-depth insight into the molecular mechanism of ALT in the treatment of lung cancer.