Overcoming acquired resistance of EGFR-mutant NSCLC cells to the third generation EGFR inhibitor, osimertinib, with the natural product honokiol

Pan-EGFR Inhibitor Dacomitinib Resensitizes Paclitaxel and Induces Apoptosis via Elevating Intracellular ROS Levels in Ovarian Cancer SKOV3-TR Cells

Paclitaxel is still used as a standard first-line treatment for ovarian cancer. Although paclitaxel is effective for many types of cancer, the emergence of chemoresistant cells represents a major challenge in chemotherapy. Our study aimed to analyze the cellular mechanism of dacomitinib, a pan-epidermal growth factor receptor (EGFR) inhibitor, which resensitized paclitaxel and induced cell cytotoxicity in paclitaxel-resistant ovarian cancer SKOV3-TR cells. We investigated the significant reduction in cell viability cotreated with dacomitinib and paclitaxel by WST-1 assay and flow cytometry analysis. Dacomitinib inhibited EGFR family proteins, including EGFR and HER2, as well as its downstream signaling proteins, including AKT, STAT3, ERK, and p38. In addition, dacomitinib inhibited the phosphorylation of Bad, and combination treatment with paclitaxel effectively suppressed the expression of Mcl-1. A 2'-7'-dichlorodihydrofluorescein diacetate (DCFH-DA) assay revealed a substantial elevation in cellular reactive oxygen species (ROS) levels in SKOV3-TR cells cotreated with dacomitinib and paclitaxel, which subsequently mediated cell cytotoxicity. Additionally, we confirmed that dacomitinib inhibits chemoresistance in paclitaxel-resistant ovarian cancer HeyA8-MDR cells. Collectively, our research indicated that dacomitinib effectively resensitized paclitaxel in SKOV3-TR cells by inhibiting EGFR signaling and elevating intracellular ROS levels.

miRNAs as short non-coding RNAs in regulating doxorubicin resistance

The treatment of cancer patients has been prohibited by chemoresistance. Doxorubicin (DOX) is an anti-tumor compound disrupting proliferation and triggering cell cycle arrest via inhibiting activity of topoisomerase I and II. miRNAs are endogenous RNAs localized in cytoplasm to reduce gene level. Abnormal expression of miRNAs changes DOX cytotoxicity. Overexpression of tumor-promoting miRNAs induces DOX resistance, while tumor-suppressor miRNAs inhibit DOX resistance. The miRNA-mediated regulation of cell death and hallmarks of cancer can affect response to DOX chemotherapy in tumor cells. The transporters such as P-glycoprotein are regulated by miRNAs in DOX chemotherapy. Upstream mediators including lncRNAs and circRNAs target miRNAs in affecting capacity of DOX. The response to DOX chemotherapy can be facilitated after administration of agents that are mostly phytochemicals including curcumol, honokiol and ursolic acid. These agents can regulate miRNA expression increasing DOX's cytotoxicity. Since delivery of DOX alone or in combination with other drugs and genes can cause synergistic impact, the nanoparticles have been introduced for drug sensitivity. The non-coding RNAs determine the response of tumor cells to doxorubicin chemotherapy. microRNAs play a key role in this case and they can be sponged by lncRNAs and circRNAs, showing interaction among non-coding RNAs in the regulation of doxorubicin sensitivity.

20 years since the approval of first EGFR-TKI, gefitinib: Insight and foresight

Epidermal growth factor receptor (EGFR) actively involves in modulation of various cancer progression related mechanisms including angiogenesis, differentiation and migration. Therefore, targeting EGFR has surfaced as a prominent approach for the treatment of several types of cancers, including non-small cell lung cancer (NSCLC), pancreatic cancer, glioblastoma. Various first, second and third generation of EGFR tyrosine kinase inhibitors (EGFR-TKIs) have demonstrated effectiveness as an anti-cancer therapeutics. However, rapid development of drug resistance and mutations still remains a major challenge for the EGFR-TKIs therapy. Overcoming from intrinsic and acquired resistance caused by EGFR mutations warrants the further exploration of alternative strategies and discovery of novel inhibitors. In this review, we delve into the breakthrough discoveries have been made in previous 20 years, and discuss the currently ongoing efforts aimed to circumvent the chemo-resistance. We also highlight the new challenges, limitations and future directions for the development of improved therapeutic approaches such as fourth-generation EGFR-TKIs, peptides, nanobodies, PROTACs etc.

MARCH8 downregulation modulates profibrotic responses including myofibroblast differentiation

Interstitial lung diseases can result in poor patient outcomes, especially in idiopathic pulmonary fibrosis (IPF), a severe interstitial lung disease with unknown causes. The lack of treatment options requires further understanding of the pathological process/mediators. Membrane-associated RING-CH 8 (MARCH8) has been implicated in immune function regulation and inflammation, however, its role in the development of pulmonary fibrosis and particularly the fibroblast to myofibroblast transition (FMT) remains a gap in existing knowledge. In this study, we demonstrated decreased MARCH8 expression in patients with IPF compared with non-PF controls and in bleomycin-induced PF. TGF-β dose- and time-dependently decreased MARCH8 expression in normal and IPF human lung fibroblast (HLFs), along with induction of FMT markers α-SMA, collagen type I (Col-1), and fibronectin (FN). Interestingly, overexpression of MARCH8 significantly suppressed TGF-β-induced expression of α-SMA, Col-1, and FN. By contrast, the knockdown of MARCH8 using siRNA upregulated basal expression of α-SMA/Col-1/FN. Moreover, MARCH8 knockdown enhanced TGF-β-induced FMT marker expression. These data clearly show that MARCH8 is a critical "brake" for FMT and potentially affects PF. We further found that TGF-β suppressed MARCH8 mRNA expression and the proteasome inhibitor MG132 failed to block MARCH8 decrease induced by TGF-β. Conversely, TGF-β decreases mRNA levels of MARCH8 in a dose- and time-dependent manner, suggesting the transcriptional regulation of MARCH8 by TGF-β. Mechanistically, MARCH8 overexpression suppressed TGF-β-induced Smad2/3 phosphorylation, which may account for the observed effects. Taken together, this study demonstrated an unrecognized role of MARCH8 in negatively regulating FMT and profibrogenic responses relevant to interstitial lung diseases.NEW & NOTEWORTHY MARCH8 is an important modulator of inflammation, immunity, and other cellular processes. We found that MARCH8 expression is downregulated in the lungs of patients with idiopathic pulmonary fibrosis (IPF) and experimental models of pulmonary fibrosis. Furthermore, TGF-β1 decreases MARCH8 transcriptionally in human lung fibroblasts (HLFs). MARCH8 overexpression blunts TGF-β1-induced fibroblast to myofibroblast transition while knockdown of MARCH8 drives this profibrotic change in HLFs. The findings support further exploration of MARCH8 as a novel target in IPF.

Honokiol inhibits the growth of hormone-resistant breast cancer cells: its promising effect in combination with metformin

Background and purpose

Primary and metastatic breast cancers still represent an unmet clinical need for improved chemotherapy and hormone therapy. Considerable attention has been paid to natural anticancer compounds, especially lignans. The study aimed to evaluate the activity of several lignans against breast cancer cells and assess the effect of leading lignans on signaling pathways in combination with metformin.

Experimental approach

Human breast cancer cell lines MCF7 (hormone-dependent), MDA-MB-231, and SKBR3 (hormone-independent) were used. A hormone-resistant MCF7/hydroxytamoxifen (HT) subline was obtained by long-term cultivation of the MCF7 line with hydroxytamoxifen. Antiproliferative activity was assessed by the MTT test; the expression of signaling pathway proteins was evaluated by immunoblotting analysis.

Findings/Results

We evaluated the antiproliferative activity of lignans in breast cancer cells with different levels of hormone dependence and determined the relevant IC50 values. Honokiol was chosen as the leading compound, and its IC50 ranged from 12 to 20 μM, whereas for other tested lignans, the IC50 exceeded 50 μM. The accumulation of cleaved PARP and a decrease in the expression of Bcl-2 and ERα in MCF7/HT were induced following the combination of honokiol with metformin.

Conclusions and implications

Honokiol demonstrated significant antiproliferative activity against both hormone-dependent breast cancer cells and lines with primary and acquired hormone resistance. The combination of honokiol with metformin is considered an effective approach to induce death in hormone-resistant cells. Honokiol is of interest as a natural compound with antiproliferative activity against breast cancers, including resistant tumors.

Honokiol Microemulsion Causes Stage-Dependent Toxicity Via Dual Roles in Oxidation-Reduction and Apoptosis through FoxO Signaling Pathway

Honokiol, the main bioactive extract of Magnolia officinalis, exhibits extensive therapeutic actions. Its treatment for advanced non-small cell lung cancer is undergoing clinical trials in China. However, the published safety evaluation studies have focused on extract mixtures of Magnolia officinalis in which the honokiol content was well below the reported clinical dose of the honokiol monomer. Therefore, safety assessment of the honokiol monomer is urgently needed. Our previous studies have already demonstrated that a high dose of the honokiol microemulsion (0.6 μg/mL) induces developmental toxicity in rats and zebrafish by inducing oxidative stress. By exploring the relationship between time and toxicity, we found that developmental toxic responses were stage-dependent. They mainly occurred within the first 24 h post fertilization (hpf) especially the first 12 hpf. In zebrafish, low doses of honokiol microemulsion (0.15, 0.21 μg/mL) significantly decreased the levels of reactive oxygen species (ROS) and malondialdehyde (MDA) and increased the mRNA expression of bcl-2. In contrast, high dose (0.6 μg/mL) increased the levels of ROS and MDA, decreased activities and mRNA expression of superoxide dismutase (SOD) and catalase (CAT), and increased mRNA expression of bax, c-jnk, p53 and bim. By acridine orange staining, we found that a high dose of honokiol microemulsion induced apoptosis mainly in zebrafish brain. In rat pheochromocytoma cells (PC12 cells), low doses of the honokiol microemulsion (1, 5, 10 µM) exerted a protective effect against H₂O₂-induced oxidative damage while high doses (≥20 µM) induced oxidative stress, which further confirms the dual effects of honokiol microemulsion on nerve cells. These dual roles of the honokiol microemulsion in oxidation-reduction reactions and apoptosis may be regulated by the forkhead box class O (FoxO) signaling pathway. Due to the potential of developmental toxicity, we recommend that the administration of high dose honokiol microemulsion in pregnant women should be considered with caution.

Overview of the multifaceted resistances toward EGFR-TKIs and new chemotherapeutic strategies in non-small cell lung cancer

The role of epidermal growth factor receptor (EGFR) in non-small cell lung cancer (NSCLC) has been vastly studied over the last decade. This has led to the rapid development of many generations of EGFR tyrosine kinase inhibitors (EGFR-TKIs). However, patients treated with third-generation TKIs (osimertinib, avitinib and rociletinib) targeting the EGFR T790M mutation have shown emerging resistances and relapses. Therefore, further molecular understanding of NSCLC mutations, bypass signalling, tumour microenvironment and the existence of cancer stem cells to overcome such resistances is warranted. This will pave the way for designing novel and effective chemotherapies to improve patients' overall survival. In this review, we provide an overview of the multifaceted mechanism of resistances towards EGFR-TKIs, as well as the challenges and perspectives that should be addressed in strategising chemotherapeutic treatments to overcome the ever evolving and adaptive nature of NSCLC.

Targeting apoptosis to manage acquired resistance to third generation EGFR inhibitors

A significant clinical challenge in lung cancer treatment is management of the inevitable acquired resistance to third-generation epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (EGFR-TKIs), such as osimertinib, which have shown remarkable success in the treatment of advanced NSCLC with EGFR activating mutations, in order to achieve maximal response duration or treatment remission. Apoptosis is a major type of programmed cell death tightly associated with cancer development and treatment. Evasion of apoptosis is considered a key hallmark of cancer and acquisition of apoptosis resistance is accordingly a key mechanism of drug acquired resistance in cancer therapy. It has been clearly shown that effective induction of apoptosis is a key mechanism for third generation EGFR-TKIs, particularly osimertinib, to exert their therapeutic efficacies and the development of resistance to apoptosis is tightly associated with the emergence of acquired resistance. Hence, restoration of cell sensitivity to undergo apoptosis using various means promises an effective strategy for the management of acquired resistance to third generation EGFR-TKIs.

Emerging strategies to overcome resistance to third-generation EGFR inhibitors

Epidermal growth factor receptor (EGFR), the receptor for members of the epidermal growth factor family, regulates cell proliferation and signal transduction; moreover, EGFR is related to the inhibition of tumor cell proliferation, angiogenesis, invasion, metastasis, and apoptosis. Therefore, EGFR has become an important target for the treatment of cancer, including non-small cell lung cancer, head and neck cancer, breast cancer, glioma, cervical cancer, and bladder cancer. First- to third-generation EGFR inhibitors have shown considerable efficacy and have significantly improved disease prognosis. However, most patients develop drug resistance after treatment. The challenge of overcoming intrinsic and acquired resistance in primary and recurrent cancer mediated by EGFR mutations is thus driving the search for alternative strategies in the design of new therapeutic agents. In view of resistance to third-generation inhibitors, understanding the intricate mechanisms of resistance will offer insight for the development of more advanced targeted therapies. In this review, we discuss the molecular mechanisms of resistance to third-generation EGFR inhibitors and review recent strategies for overcoming resistance, new challenges, and future development directions.

Opportunities and challenges for co-delivery nanomedicines based on combination of phytochemicals with chemotherapeutic drugs in cancer treatment

The therapeutic limitations such as insufficient efficacy, drug resistance, metastasis, and undesirable side effects are frequently caused by the long duration monotherapy based on chemotherapeutic drugs. multiple combinational anticancer strategies such as nucleic acids combined with chemotherapeutic agents, chemotherapeutic combinations, chemotherapy and tumor immunotherapy combinations have been embraced, holding great promise to counter these limitations, while still taking including some potential risks. Nowadays, an increasing number of research has manifested the anticancer effects of phytochemicals mediated by modulating cancer cellular events directly as well as the tumor microenvironment. Specifically, these natural compounds exhibited suppression of cancer cell proliferation, apoptosis, migration and invasion of cancer cells, P-glycoprotein inhibition, decreasing vascularization and activation of tumor immunosuppression. Due to the low toxicity and multiple modulation pathways of these phytochemicals, the combination of chemotherapeutic agents with natural compounds acts as a novel approach to cancer therapy to increase the efficiency of cancer treatments as well as reduce the adverse consequences. In order to achieve the maximized combination advantages of small-molecule chemotherapeutic drugs and natural compounds, a variety of functional nano-scaled drug delivery systems, such as liposomes, host-guest supramolecules, supramolecules, dendrimers, micelles and inorganic systems have been developed for dual/multiple drug co-delivery. These co-delivery nanomedicines can improve pharmacokinetic behavior, tumor accumulation capacity, and achieve tumor site-targeting delivery. In that way, the improved antitumor effects through multiple-target therapy and reduced side effects by decreasing dose can be implemented. Here, we present the synergistic anticancer outcomes and the related mechanisms of the combination of phytochemicals with small-molecule anticancer drugs. We also focus on illustrating the design concept, and action mechanisms of nanosystems with co-delivery of drugs to synergistically improve anticancer efficacy. In addition, the challenges and prospects of how these insights can be translated into clinical benefits are discussed.

Induction of SREBP1 degradation coupled with suppression of SREBP1-mediated lipogenesis impacts the response of EGFR mutant NSCLC cells to osimertinib

Emergence of acquired resistance to osimertinib (AZD9291), the first-approved third-generation EGFR inhibitor that selectively and irreversibly inhibits the activating EGFR mutations and the resistant T790M mutation, is a giant and urgent clinical challenge. Fully understanding the biology underlying the response of EGFR mutant non-small cell lung cancer (NSCLC) to osimertinib is the foundation for development of mechanism-driven strategies to overcome acquired resistance to osimertinib or other third-generation EGFR inhibitors. This study focused on tackling this important issue by elucidating the critical role of sterol regulatory element-binding protein 1 (SREBP1) degradation in conferring the response of EGFR mutant NSCLC cells to osimertinib and by validating the strategy via directly targeting SREBP1 for overcoming osimertinib acquired resistance. Osimertinib facilitated degradation of the mature form of SREBP1 (mSREBP1) in a GSK3/FBXW7-dependent manner and reduced protein levels of its regulated genes in EGFR-mutant NSCLC cells/tumors accompanied with suppression of lipogenesis. Once resistant, EGFR-mutant NSCLC cell lines possessed elevated levels of mSREBP1, which were resistant to osimertinib modulation. Both genetic and pharmacological inhibition of SREBP1 sensitized osimertinib-resistant cells and tumors to osimertinib primarily through enhancing Bim-dependent induction of apoptosis, whereas enforced expression of ectopic SREBP1 in sensitive EGFR-mutant NSCLC cells compromised osimertinib's cell-killing effects. Collectively, we have demonstrated a novel connection between osimertinib and SREBP1 degradation and its impact on the response of EGFR mutant NSCLC cells to osimertinib and suggested an effective strategy for overcoming acquired resistance to osimertinib, and possibly other EGFR inhibitors, via targeting SREBP1.

Mitochondrial Metabolism in Melanoma

Melanoma and its associated alterations in cellular pathways have been growing areas of interest in research, especially as specific biological pathways are being elucidated. Some of these alterations include changes in the mitochondrial metabolism in melanoma. Many mitochondrial metabolic changes lead to differences in the survivability of cancer cells and confer resistance to targeted therapies. While extensive work has gone into characterizing mechanisms of resistance, the role of mitochondrial adaptation as a mode of resistance is not completely understood. In this review, we wish to explore mitochondrial metabolism in melanoma and how it impacts modes of resistance. There are several genes that play a major role in melanoma mitochondrial metabolism which require a full understanding to optimally target melanoma. These include BRAF, CRAF, SOX2, MCL1, TRAP1, RHOA, SRF, SIRT3, PTEN, and AKT1. We will be discussing the role of these genes in melanoma in greater detail. An enhanced understanding of mitochondrial metabolism and these modes of resistance may result in novel combinatorial and sequential therapies that may lead to greater therapeutic benefit.

Nanoparticles for co-delivery of osimertinib and selumetinib to overcome osimertinib-acquired resistance in non-small cell lung cancer

Osimertinib (OSI) is the first FDA-approved third-generation epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI). It can be used for treating non-small cell lung cancer (NSCLC) patients with activating EGFR mutation and for patients who are resistant to first-generation EGFR TKIs due to T790M resistance mutation. However, patients treated with OSI ultimately develop acquired resistance, which prevents its long-term benefit for patients. Therefore, the development of effective strategies to overcome OSI resistance will address a significant clinical challenge and benefit patients by prolonging their survival time. Our previous studies indicated that combination therapy was a promising strategy for overcoming OSI resistance. In this study, we developed nanoparticle (NP) formulations for co-delivery of osimertinib (OSI) and selumetinib (SEL) to treat OSI-resistant NSCLC effectively. We conjugated SEL with PEG through a reactive oxygen species (ROS)-responsive linker to generate polyethylene glycol (PEG)-SEL conjugate prodrug (PEG-S-SEL). Due to the amphiphilic nature of PEG-S-SEL, it can self-assemble in an aqueous solution to form micelle NP and serve as a delivery carrier for OSI. The ROS-responsive linker can facilitate the release of drugs in the tumor microenvironment with elevated ROS levels. OSI and SEL combination NP can overcome OSI resistance by simultaneously inhibiting both EGFR and mitogen-activated protein kinase (MEK), thus effectively inducing apoptosis in OSI-resistant NSCLC cells and inhibiting OSI-resistant tumors in vivo. In conclusion, the OSI+SEL NP combination therapy showed promising anticancer efficacy and demonstrated potential for treating NSCLC patients with OSI acquired resistance. STATEMENT OF SIGNIFICANCE: Osimertinib (OSI) is the first FDA-approved third-generation epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor. It has been successfully used for treating non-small cell lung cancer (NSCLC) patients with activating EGFR mutation. However, patients treated with OSI ultimately develop acquired resistance. This study developed OSI and selumetinib (SEL) co-delivering nanoparticles to overcome OSI-acquired resistance in NSCLC. PEG-SEL conjugate functions as reactive oxygen species (ROS)-responsive prodrug and forms micelle nanoparticles through self-assembly to deliver OSI. The combination NP can simultaneously inhibit EGFR and mitogen-activated protein kinase (MEK), thus effectively inducing apoptosis in OSI-resistant NSCLC cells. In summary, the OSI and SEL nanoparticle combination therapy showed promising anticancer efficacy and demonstrated potential for treating NSCLC patients with OSI acquired resistance.

Natural Products, Alone or in Combination with FDA-Approved Drugs, to Treat COVID-19 and Lung Cancer

As a public health emergency of international concern, the highly contagious coronavirus disease 2019 (COVID-19) pandemic has been identified as a severe threat to the lives of billions of individuals. Lung cancer, a malignant tumor with the highest mortality rate, has brought significant challenges to both human health and economic development. Natural products may play a pivotal role in treating lung diseases. We reviewed published studies relating to natural products, used alone or in combination with US Food and Drug Administration-approved drugs, active against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and lung cancer from 1 January 2020 to 31 May 2021. A wide range of natural products can be considered promising anti-COVID-19 or anti-lung cancer agents have gained widespread attention, including natural products as monotherapy for the treatment of SARS-CoV-2 (ginkgolic acid, shiraiachrome A, resveratrol, and baicalein) or lung cancer (daurisoline, graveospene A, deguelin, and erianin) or in combination with FDA-approved anti-SARS-CoV-2 agents (cepharanthine plus nelfinavir, linoleic acid plus remdesivir) and anti-lung cancer agents (curcumin and cisplatin, celastrol and gefitinib). Natural products have demonstrated potential value and with the assistance of nanotechnology, combination drug therapies, and the codrug strategy, this "natural remedy" could serve as a starting point for further drug development in treating these lung diseases.

Overview of Evidence-Based Chemotherapy for Oral Cancer: Focus on Drug Resistance Related to the Epithelial-Mesenchymal Transition

The increasing incidence of resistance to chemotherapeutic agents has become a major issue in the treatment of oral cancer (OC). Epithelial-mesenchymal transition (EMT) has attracted a great deal of attention in recent years with regard to its relation to the mechanism of chemotherapy drug resistance. EMT-activating transcription factors (EMT-ATFs), such as Snail, TWIST, and ZEB, can activate several different molecular pathways, e.g., PI3K/AKT, NF-κB, and TGF-β. In contrast, the activated oncological signal pathways provide reciprocal feedback that affects the expression of EMT-ATFs, resulting in a peritumoral extracellular environment conducive to cancer cell survival and evasion of the immune system, leading to resistance to multiple chemotherapeutic agents. We present an overview of evidence-based chemotherapy for OC treatment based on the National Comprehensive Cancer Network (NCCN) Chemotherapy Order Templates. We focus on the molecular pathways involved in drug resistance related to the EMT and highlight the signal pathways and transcription factors that may be important for EMT-regulated drug resistance. Rapid progress in antitumor regimens, together with the application of powerful techniques such as high-throughput screening and microRNA technology, will facilitate the development of therapeutic strategies to augment chemotherapy.

Polyphyllin I reverses the resistance of osimertinib in non-small cell lung cancer cell through regulation of PI3K/Akt signaling

Lung cancer is considered the main cause of cancer mortality worldwide. Osimertinib, a third-generation EGFR-TKI, has been approved and administrated for treating patients with either EGFR T790M mutation or EGFR sensitive mutation. However, resistance to osimertinib emerges and has been considered to be the main obstacle in lung cancer treatment. Polyphyllin I is isolated from the natural herb Paris polyphylla and exhibits anti-cancer activities. In the present study, we identify Polyphyllin I to reverse the resistance of osimertinib in vitro and in vivo. The results showed that Polyphyllin I reversed the resistance of osimertinib through promoting apoptosis, modulating the PI3K/Akt signaling, and regulating the expression of apoptosis-related proteins in osimertinib-resistant cell lines. In vivo study confirmed the results, showing that the tumor growth was significantly suppressed in the Polyphyllin I/osimertinib group compared to the osimertinib group. It has been clarified that Polyphyllin I could reverse the resistance of osimertinib in osimertinib-resistant non-small cell of lung cancer in vitro and in vivo. The underlying mechanism might be related to the downregulation of the PI3K/Akt signaling and increase of the expression of apoptosis-related proteins, suggesting that Polyphyllin I was a promising therapeutic agent for reversing the resistance of osimertinib.

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.

Cell Line Models for Acquired Resistance to First-Line Osimertinib in Lung Cancers-Applications and Limitations

Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) are first-line drugs for lung cancers with activating EGFR mutations. Although first- and second-generation EGFR-TKIs were standard first-line treatments, acquired resistance (AR) to these drugs is almost inevitable. Cell line models have been widely used to explore the molecular mechanisms of AR to first- and second-generation EGFR-TKIs. Many research groups, including ours, have established AR cell lines that harbor the EGFR T790M secondary mutation, MET gene amplification, or epithelial–mesenchymal transition (EMT) features, which are all found in clinical specimens obtained from TKI-refractory lesions. Currently, many oncologists prescribe osimertinib, a third-generation EGFR-TKI that can overcome T790M-mediated resistance, as a first-line TKI. Although few clinical data are available about AR mechanisms that arise when osimertinib is used as a first-line therapy, many research groups have established cell lines with AR to osimertinib and have reported on their AR mechanisms. In this review, we summarize the findings on AR mechanisms against first-line osimertinib obtained from analyses of cell line models.

Honokiol antagonizes doxorubicin resistance in human breast cancer via miR-188-5p/FBXW7/c-Myc pathway

BACKGROUND

Honokiol, a natural phenolic compound derived from Magnolia plants, is a promising anti-tumor compound that exerts a wide range of anti-cancer effects. Herein, we investigated the effect of honokiol on doxorubicin resistance in breast cancer.

METHODS

Doxorubicin-sensitive (MCF-7 and MDA-MB-231) and doxorubicin-resistant (MCF-7/ADR and MDA-MB-231/ADR) breast cancer cell lines were treated with doxorubicin in the absence or presence of honokiol; then, the following tests were performed: flow cytometry for cell apoptosis, WST-1 assay for cell viability, qPCR and western blot for the expression of miR-188-5p, FBXW7, and c-Myc. MiR-188-5p mimic, miR-188-5p inhibitor, siFBXW7, and c-Myc plasmids were transfected into cancer cells to evaluate whether miR-188-5p and FBXW7/c-Myc signaling are involved in the effect of honokiol on doxorubicin resistance in breast cancer. A dual luciferase reporter system was used to study the direct interaction between miR-188-5p and FBXW7.

RESULTS

Honokiol sensitized doxorubicin-resistant breast cancer cells to doxorubicin-induced apoptosis. Mechanically, upregulation of miR-188-5p was associated with doxorubicin resistance, and honokiol enhanced doxorubicin sensitivity by downregulating miR-188-5p. FBXW7 was confirmed to be a direct target gene of miR-188-5p. FBXW7/c-Myc signaling was involved in the chemosensitization effect of honokiol. Honokiol induced apoptosis in MCF-7/ADR and MDA-MB-231/ADR cells. However, FBXW7 silencing or c-Myc transfection resulted in resistance to the honokiol-induced apoptotic effect.

CONCLUSION

These findings suggest that downregulation of miR-188-5p by honokiol enhances doxorubicin sensitivity through FBXW7/c-Myc signaling in human breast cancer. Our study finds an important role of miR-188-5p in the development of doxorubicin resistance in breast cancer, and enriches our understanding of the mechanism of action of honokiol in cancer therapy.

Arctigenin inhibits proliferation of ER-positive breast cancer cells through cell cycle arrest mediated by GSK3-dependent cyclin D1 degradation

Estrogen receptor (ER) positive accounts for a large proportion of breast cancer. Although there are many targeted therapeutic drugs, the emergence of drug resistance urgently requires the development of new drugs. Arctigenin (Arc), a lignan found in certain plants of the Asteraceae, has the effect on inhibiting breast cancer, but its molecular mechanism has not been clear.

AIMS

To this end, the current study focuses on understanding the mechanism of Arc on ER-positive breast cancer cells.

MAIN METHODS

Colony formation experiments and sulforhodamine B methods were used to determine the growth-inhibitory effect of Arc. The cell cycle and apoptosis were analyzed by flow cytometry. Alterations of signaling proteins were measured by Western blotting. Protein degradation was determined by comparing protein half-lives and inhibiting proteasome.

KEY FINDINGS

The experimental results show that Arc did not induce apoptosis in ER-positive breast cancer cell, rather caused G1 cycle arrest by decreasing cyclin D1 levels without effect on altering CDK4/6 levels. Moreover, we have demonstrated that Arc decreases cyclin D1 levels through prompting Akt/GSK3β-mediated degradation.

SIGNIFICANCE

These findings warrant the potential of Arc as a candidate treatment for ER-positive breast cancer.

Association of the Epithelial-Mesenchymal Transition (EMT) with Cisplatin Resistance

Therapy resistance is a characteristic of cancer cells that significantly reduces the effectiveness of drugs. Despite the popularity of cisplatin (CP) as a chemotherapeutic agent, which is widely used in the treatment of various types of cancer, resistance of cancer cells to CP chemotherapy has been extensively observed. Among various reported mechanism(s), the epithelial–mesenchymal transition (EMT) process can significantly contribute to chemoresistance by converting the motionless epithelial cells into mobile mesenchymal cells and altering cell–cell adhesion as well as the cellular extracellular matrix, leading to invasion of tumor cells. By analyzing the impact of the different molecular pathways such as microRNAs, long non-coding RNAs, nuclear factor-κB (NF-ĸB), phosphoinositide 3-kinase-related protein kinase (PI3K)/Akt, mammalian target rapamycin (mTOR), and Wnt, which play an important role in resistance exhibited to CP therapy, we first give an introduction about the EMT mechanism and its role in drug resistance. We then focus specifically on the molecular pathways involved in drug resistance and the pharmacological strategies that can be used to mitigate this resistance. Overall, we highlight the various targeted signaling pathways that could be considered in future studies to pave the way for the inhibition of EMT-mediated resistance displayed by tumor cells in response to CP exposure.