Overexpression of MDR1 and survivin, and decreased Bim expression mediate multidrug-resistance in multiple myeloma cells

Alterations in pharmacogenetic genes and their implications for imatinib resistance in Chronic Myeloid Leukemia patients from an admixed population

Imatinib is the tyrosine kinase inhibitor used as the gold standard for the treatment of Chronic Myeloid Leukemia. However, about 30% of patients do not respond well to this therapy. Variants in drug administration, distribution, metabolism and excretion (ADME) genes play an important role in drug resistance especially in admixed populations. We investigated 129 patients diagnosed with Chronic Myeloid Leukemia treated with imatinib as first choice therapy. The participants of the study are highly admixed, populations that exhibit genetic diversity and complexity due to the contributions of multiple ancestral groups. Thus, the aim of this work was to investigate the association of 30 SNVs in genes related to response to treatment with Imatinibe in CML. Our results indicated that for the rs2290573 of the ULK3 gene, patients with the recessive AA genotype are three times more likely to develop resistance over time (secondary resistance) (p = 0.019, OR = 3.19, IC 95%= 1.21-8.36). Finally, we performed interaction analysis between the investigated variants and found several associations between SNVs and secondary resistance. We concluded that the variant rs2290573 of the ULK3 gene may be relevant for predicting treatment response of CML with imatinib, as well as possible treatment resistance. The use of predictive biomarkers is an important tool for therapeutic choice of patients, improving their quality of life and treatment efficacy.

Shikonin enhances chemosensitivity of oral cancer through β-catenin pathway

OBJECTIVES

This study concentrates on exploring the synergistic effect of shikonin on cisplatin against oral cancer.

METHODS

To analyze the IC50 value of shikonin, gradient concentrations of shikonin were added to the oral cancer cell culture medium. After the cisplatin-resistant cell line was established, the effects of cisplatin and shikonin on the survival rate, proliferation, apoptosis and related pathway protein expression of common/drug-resistant oral cancer cells were compared through MTT, clone formation, flow cytometry, and Western blot experiments. β-catenin, which had the most significant expression changes, was overexpressed and silenced, and used to design a reverse validation.

RESULTS

Shikonin inhibited the viability of oral cancer cells. Although cisplatin killed some cancer cells, its effect on drug-resistant cancer cells was significantly reduced. The addition of shikonin enhanced the sensitivity of drug-resistant cells to cisplatin. Shikonin regulated key proteins in cell proliferation and apoptosis-related pathways. Among them, shikonin generated the most evident inhibitory effect on β-catenin. Therefore, β-catenin overexpression plasmid/siβ-catenin was transfected into the cells. Silenced β-catenin was found to reinforce the damaging effect of cisplatin on cancer cells, and overexpressed β-catenin reversed the effect of shikonin.

CONCLUSION

By down-regulating β-catenin expression, shikonin improves the sensitivity of drug-resistant oral cancer cells to cisplatin.

Epidermal Growth Factor Receptor Inhibitor Mobocertinib Resensitizes Multidrug-Resistant Cancer Cells by Attenuating the Human ATP-Binding Cassette Subfamily B Member 1 and Subfamily G Member 2

ATP-binding cassette (ABC) transporters, notably ABCB1 (P-glycoprotein) and ABCG2, play a crucial role in the development of multidrug resistance (MDR) during the administration of chemotherapy for cancer patients. With a lack of approved treatments for addressing multidrug-resistant cancers, MDR remains a substantial challenge to the effective management of cancer. Rather than focusing on developing novel synthetic inhibitors, a promising approach to combat MDR involves repurposing approved therapeutic agents to enhance the sensitivity to cytotoxic antiproliferative drugs of multidrug-resistant cancer cells with high expression of ABCB1 or ABCG2. In this investigation, we observed a substantial reversal of MDR conferred by ABCB1 and ABCG2 in multidrug-resistant cancer cells through the use of mobocertinib, an approved third-generation inhibitor of the epidermal growth factor receptor (EGFR) tyrosine kinase. Mobocertinib demonstrated the ability to hinder drug transport function without causing changes in protein expression. The interactions between mobocertinib and ABCB1, as well as ABCG2, were validated through ATPase assays. Furthermore, in silico docking simulations were utilized to substantiate the binding of mobocertinib within the drug-binding pockets of both ABCB1 and ABCG2. We conclude that further testing of mobocertinib in combination therapy is warranted for patients with tumors expressing elevated levels of the ABC drug transporters ABCB1 and ABCG2.

Furmonertinib, a Third-Generation EGFR Tyrosine Kinase Inhibitor, Overcomes Multidrug Resistance through Inhibiting ABCB1 and ABCG2 in Cancer Cells

ATP-binding cassette transporters, including ABCB1 (P-glycoprotein) and ABCG2 (BCRP/MXR/ABCP), are pivotal in multidrug resistance (MDR) development in cancer patients undergoing conventional chemotherapy. The absence of approved therapeutic agents for multidrug-resistant cancers presents a significant challenge in effectively treating cancer. Researchers propose repurposing existing drugs to sensitize multidrug-resistant cancer cells, which overexpress ABCB1 or ABCG2, to conventional anticancer drugs. The goal of this study is to assess whether furmonertinib, a third-generation epidermal growth factor receptor tyrosine kinase inhibitor overcomes drug resistance mediated by ABCB1 and ABCG2 transporters. Furmonertinib stands out due to its ability to inhibit drug transport without affecting protein expression. The discovery of this characteristic was validated through ATPase assays, which revealed interactions between furmonertinib and ABCB1/ABCG2. Additionally, in silico docking of furmonertinib offered insights into potential interaction sites within the drug-binding pockets of ABCB1 and ABCG2, providing a better understanding of the underlying mechanisms responsible for the reversal of MDR by this repurposed drug. Given the encouraging results, we propose that furmonertinib should be explored as a potential candidate for combination therapy in patients with tumors that have high levels of ABCB1 and/or ABCG2. This combination therapy holds the potential to enhance the effectiveness of conventional anticancer drugs and presents a promising strategy for overcoming MDR in cancer treatment.

Molecular and immunological mechanisms of clonal evolution in multiple myeloma

Multiple myeloma (MM) is a hematologic malignancy characterized by the proliferation of clonal plasma cells in the bone marrow (BM). It is known that early genetic mutations in post-germinal center B/plasma cells are the cause of myelomagenesis. The acquisition of additional chromosomal abnormalities and distinct mutations further promote the outgrowth of malignant plasma cell populations that are resistant to conventional treatments, finally resulting in relapsed and therapy-refractory terminal stages of MM. In addition, myeloma cells are supported by autocrine signaling pathways and the tumor microenvironment (TME), which consists of diverse cell types such as stromal cells, immune cells, and components of the extracellular matrix. The TME provides essential signals and stimuli that induce proliferation and/or prevent apoptosis. In particular, the molecular pathways by which MM cells interact with the TME are crucial for the development of MM. To generate successful therapies and prevent MM recurrence, a thorough understanding of the molecular mechanisms that drive MM progression and therapy resistance is essential. In this review, we summarize key mechanisms that promote myelomagenesis and drive the clonal expansion in the course of MM progression such as autocrine signaling cascades, as well as direct and indirect interactions between the TME and malignant plasma cells. In addition, we highlight drug-resistance mechanisms and emerging therapies that are currently tested in clinical trials to overcome therapy-refractory MM stages.

Bim downregulation by activation of NF-κB p65, Akt, and ERK1/2 is associated with adriamycin and dexamethasone resistance in multiple myeloma cells

Multiple myeloma (MM) frequently acquires multidrug resistance (MDR), which is due to poor prognosis. Our previous study indicated that high expression of Survivin and multidrug resistance protein 1 (MDR1) and decreased expression of Bim are associated with MDR in adriamycin- and dexamethasone-resistant cells. However, the fundamental mechanism of MDR in adriamycin- and dexamethasone-resistant MM cells is still unidentified. In this study, we examined the MDR mechanism in adriamycin- and dexamethasone-resistant cells. RPMI8226/ADM, ARH-77/ADM, RPMI8226/DEX, and ARH-77/DEX cells exhibited enhanced nuclear factor κB (NF-κB) p65, Akt, and extracellular signal-regulated kinase 1/2 (ERK1/2) activation. Combination treatment with NF-κB p65, phosphoinositide 3-kinase (PI3K), and mitogen-activated protein kinase 1/2 (MEK1/2) inhibitors resensitized to adriamycin and dexamethasone via increased Bim expression. Although treatment with MDR1 or Survivin siRNA did not overcome adriamycin and dexamethasone resistance in RPMI8226/ADM and RPMI8226/DEX cells, administration of Bim siRNA induced adriamycin and dexamethasone resistance in RPMI8226 cells. Moreover, low expression of Bim was related to poor prognosis in MM patients. These results indicate that activation of NF-κB p65, Akt, and ERK1/2 is associated with adriamycin and dexamethasone resistance via decreasing Bim expression, and these signal inhibitor combinations overcome drug resistance in MM. These findings suggest that combination treatment with these inhibitors and adriamycin or dexamethasone may be a promising therapy for adriamycin- and dexamethasone-resistant MM.

Long Noncoding RNAs in Taxane Resistance of Breast Cancer

Breast cancer is a common cancer in women and a leading cause of mortality. With the early diagnosis and development of therapeutic drugs, the prognosis of breast cancer has markedly improved. Chemotherapy is one of the predominant strategies for the treatment of breast cancer. Taxanes, including paclitaxel and docetaxel, are widely used in the treatment of breast cancer and remarkably decrease the risk of death and recurrence. However, taxane resistance caused by multiple factors significantly impacts the effect of the drug and leads to poor prognosis. Long noncoding RNAs (lncRNAs) have been shown to play a significant role in critical cellular processes, and a number of studies have illustrated that lncRNAs play vital roles in taxane resistance. In this review, we systematically summarize the mechanisms of taxane resistance in breast cancer and the functions of lncRNAs in taxane resistance in breast cancer. The findings provide insight into the role of lncRNAs in taxane resistance and suggest that lncRNAs may be used to develop therapeutic targets to prevent or reverse taxane resistance in patients with breast cancer.

Hydroxygenkwanin Improves the Efficacy of Cytotoxic Drugs in ABCG2-Overexpressing Multidrug-Resistant Cancer Cells

Hydroxygenkwanin, a flavonoid isolated from the leaves of the Daphne genkwa plant, is known to have pharmacological properties; however, its modulatory effect on multidrug resistance, which is (MDR) mediated by ATP-binding cassette (ABC) drug transporters, has not been investigated. In this study, we examine the interaction between hydroxygenkwanin, ABCB1, and ABCG2, which are two of the most well-characterized ABC transporters known to contribute to clinical MDR in cancer patients. Hydroxygenkwanin is not an efflux substrate of either ABCB1 or ABCG2. We discovered that, in a concentration-dependent manner, hydroxygenkwanin significantly reverses ABCG2-mediated resistance to multiple cytotoxic anticancer drugs in ABCG2-overexpressing multidrug-resistant cancer cells. Although it inhibited the drug transport function of ABCG2, it had no significant effect on the protein expression of this transporter in cancer cells. Experimental data showing that hydroxygenkwanin stimulates the ATPase activity of ABCG2, and in silico docking analysis of hydroxygenkwanin binding to the inward-open conformation of human ABCG2, further indicate that hydroxygenkwanin sensitizes ABCG2-overexpressing cancer cells by binding to the substrate-binding pocket of ABCG2 and attenuating the transport function of ABCG2. This study demonstrates the potential use of hydroxygenkwanin as an effective inhibitor of ABCG2 in drug combination therapy trials for patients with tumors expressing higher levels of ABCG2.

The WD repeat-containing protein 5 (WDR5) antagonist WDR5-0103 restores the efficacy of cytotoxic drugs in multidrug-resistant cancer cells overexpressing ABCB1 or ABCG2

The development of multidrug resistance (MDR) is one of the major challenges in the treatment of cancer which is caused by the overexpression of the ATP-binding cassette (ABC) transporters ABCB1 (P-glycoprotein) and/or ABCG2 (BCRP/MXR/ABCP) in cancer cells. These transporters are capable of reducing the efficacy of cytotoxic drugs by actively effluxing them out of cancer cells. Since there is currently no approved treatment for patients with multidrug-resistant tumors, the drug repurposing approach provides an alternative route to identify agents to reverse MDR mediated by ABCB1 and/or ABCG2 in multidrug-resistant cancer cells. WDR5-0103 is a histone H3 lysine 4 (H3K4) methyltransferase inhibitor that disrupts the interaction between the WD repeat-containing protein 5 (WDR5) and mixed-lineage leukemia (MLL) protein. In this study, the effect of WDR5-0103 on MDR mediated by ABCB1 and ABCG2 was determined. We found that in a concentration-dependent manner, WDR5-0103 could sensitize ABCB1- and ABCG2-overexpressing multidrug-resistant cancer cells to conventional cytotoxic drugs. Our results showed that WDR5-0103 reverses MDR and improves drug-induced apoptosis in multidrug-resistant cancer cells by inhibiting the drug-efflux function of ABCB1 and ABCG2, without altering the protein expression of ABCB1 or ABCG2. The potential sites of interactions of WDR5-0103 with the drug-binding pockets of ABCB1 and ABCG2 were predicted by molecular docking. In conclusion, the MDR reversal activity of WDR5-0103 demonstrated here indicates that it could be used in combination therapy to provide benefits to a subset of patients with tumor expressing high levels of ABCB1 or ABCG2.

P-glycoprotein Mediates Resistance to the Anaplastic Lymphoma Kinase Inhiitor Ensartinib in Cancer Cells

Ensartinib (X-396) is a promising second-generation small-molecule inhibitor of anaplastic lymphoma kinase (ALK) that was developed for the treatment of ALK-positive non-small-cell lung cancer. Preclinical and clinical trial results for ensartinib showed superior efficacy and a favorable safety profile compared to the first-generation ALK inhibitors that have been approved by the U.S. Food and Drug Administration. Although the potential mechanisms of acquired resistance to ensartinib have not been reported, the inevitable emergence of resistance to ensartinib may limit its therapeutic application in cancer. In this work, we investigated the interaction of ensartinib with P-glycoprotein (P-gp) and ABCG2, two ATP-binding cassette (ABC) multidrug efflux transporters that are commonly associated with the development of multidrug resistance in cancer cells. Our results revealed that P-gp overexpression, but not expression of ABCG2, was associated with reduced cancer cell susceptibility to ensartinib. P-gp directly decreased the intracellular accumulation of ensartinib, and consequently reduced apoptosis and cytotoxicity induced by this drug. The cytotoxicity of ensartinib could be significantly reversed by treatment with the P-gp inhibitor tariquidar. In conclusion, we report that ensartinib is a substrate of P-gp, and provide evidence that this transporter plays a role in the development of ensartinib resistance. Further investigation is needed.

The multi-targeted tyrosine kinase inhibitor SKLB610 resensitizes ABCG2-overexpressing multidrug-resistant cancer cells to chemotherapeutic drugs

The overexpression of ATP-binding cassette (ABC) transporter ABCB1 (P-glycoprotein) or ABCG2 (BCRP/MXR/ABCP) in cancer cells is frequently associated with the development of multidrug resistance (MDR) in cancer patients, which remains a major obstacle to effective cancer treatment. By utilizing energy derived from ATP hydrolysis, both transporters have been shown to reduce the chemosensitivity of cancer cells by actively effluxing cytotoxic anticancer drugs out of cancer cells. Knowing that there are presently no approved drugs or other therapeutics for the treatment of multidrug-resistant cancers, in recent years, studies have investigated the repurposing of tyrosine kinase inhibitors (TKIs) to act as agents against MDR mediated by ABCB1 and/or ABCG2. SKLB610 is a multi-targeted TKI with potent activity against vascular endothelial growth factor receptor 2 (VEGFR2), platelet-derived growth factor receptor (PDGFR), and fibroblast growth factor receptor 2 (FGFR2). In this study, we investigate the interaction of SKLB610 with ABCB1 and ABCG2. We discovered that neither ABCB1 nor ABCG2 confers resistance to SKLB610, but SKLB610 selectively sensitizes ABCG2-overexpressing multidrug-resistant cancer cells to cytotoxic anticancer agents in a concentration-dependent manner. Our data indicate that SKLB610 reverses ABCG2-mediated MDR by attenuating the drug-efflux function of ABCG2 without affecting its total cell expression. These findings are further supported by results of SKLB610-stimulated ABCG2 ATPase activity and in silico docking of SKLB610 in the drug-binding pocket of ABCG2. In summary, we reveal the potential of SKLB610 to overcome resistance to cytotoxic anticancer drugs, which offers an additional treatment option for patients with multidrug-resistant cancers and warrants further investigation.

Significance of a tumor microenvironment-mediated P65-miR-30a-5p-BCL2L11 amplification loop in multiple myeloma

Despite significant progress in the treatment of myeloma, multiple myeloma (MM) remains an incurable hematological malignancy due to cell adhesion-mediated drug resistance (CAM-DR) phenotype. However, data on the molecular mechanisms underlying the CAM-DR remains scanty. Here, we identified a miRNA-mRNA regulatory network in myeloma cells that are directly adherent to bone marrow stromal cells (BMSCs). Our data showed that the BMSCs up-regulated miR-30a-5p and down-regulated BCL2L11 at both mRNA and protein level in the myeloma cells. Besides, luciferase reporter genes demonstrated direct interaction between miR-30a-5p and BCL2L11 gene. Moreover, the BMSCs activated NF-ΚB signaling pathway in myeloma cells and the NF-κB P65 was shown to directly bind the miR-30a-5p promoter region. Moreover, suppression of the miR-30a-5p or upregulation of the BCL2L11 promoted apoptosis of the myeloma cells independent of the BMSCs, thus suggesting clinical significance of miR-30a-5p inhibitor and PLBCL2L11 plasmid in CAM-DR. Together, our data demonstrated the role of P65-miR-30a-5p-BCL2L11 loop in CAM-DR myeloma cells. These findings give new insights into the role of tumor microenvironment in the treatment of patients with myeloma.

The Establishment of Quantitatively Regulating Expression Cassette with sgRNA Targeting BIRC5 to Elucidate the Synergistic Pathway of Survivin with P-Glycoprotein in Cancer Multi-Drug Resistance

Quantitative analysis and regulating gene expression in cancer cells is an innovative method to study key genes in tumors, which conduces to analyze the biological function of the specific gene. In this study, we found the expression levels of Survivin protein (BIRC5) and P-glycoprotein (MDR1) in MCF-7/doxorubicin (DOX) cells (drug-resistant cells) were significantly higher than MCF-7 cells (wild-type cells). In order to explore the specific functions of BIRC5 gene in multi-drug resistance (MDR), a CRISPR/Cas9-mediated knocking-in tetracycline (Tet)-off regulatory system cell line was established, which enabled us to regulate the expression levels of Survivin quantitatively (clone 8 named MCF-7/Survivin was selected for further studies). Subsequently, the determination results of doxycycline-induced DOX efflux in MCF-7/Survivin cells implied that Survivin expression level was opposite to DOX accumulation in the cells. For example, when Survivin expression was down-regulated, DOX accumulation inside the MCF-7/Survivin cells was up-regulated, inducing strong apoptosis of cells (reversal index 118.07) by weakening the release of intracellular drug from MCF-7/Survivin cells. Also, down-regulation of Survivin resulted in reduced phosphorylation of PI3K, Akt, and mTOR in MCF-7/Survivin cells and significantly decreased P-gp expression. Previous studies had shown that PI3K/Akt/mTOR could regulate P-gp expression. Therefore, we speculated that Survivin might affect the expression of P-gp through PI3K/Akt/mTOR pathway. In summary, this quantitative method is not only valuable for studying the gene itself, but also can better analyze the biological phenomena related to it.

Branebrutinib (BMS-986195), a Bruton's Tyrosine Kinase Inhibitor, Resensitizes P-Glycoprotein-Overexpressing Multidrug-Resistant Cancer Cells to Chemotherapeutic Agents

The overexpression of P-glycoprotein (P-gp/ABCB1), an ATP-binding cassette (ABC) drug transporter, often contributes to the development of multidrug resistance (MDR) in cancer cells. P-gp mediates the ATP hydrolysis-dependent efflux of a wide range of chemotherapeutic agents out of cancer cells, thereby reducing the intracellular drug accumulation and decreasing the chemosensitivity of these multidrug-resistant cancer cells. Studies with tyrosine kinase inhibitors (TKIs) in P-gp-overexpressing cells have shown that certain TKIs could reverse MDR mediated by P-gp, while some TKIs are transported by P-gp. In the present work, we explored the prospect of repositioning branebrutinib (BMS-986195), a highly selective inhibitor of Bruton’s tyrosine kinase (BTK), to resensitize P-gp-overexpressing multidrug-resistant cancer cells to chemotherapeutic agents. Our results demonstrated that branebrutinib is capable of reversing P-gp-mediated MDR at sub-toxic concentrations, most likely by directly inhibiting the drug transport function of P-gp. Our findings were supported by the result of branebrutinib stimulating the ATPase activity of P-gp in a concentration-dependent manner and the in silico study of branebrutinib binding to the substrate-binding pocket of P-gp. In addition, we found that branebrutinib is equally cytotoxic to drug-sensitive parental cell lines and the respective P-gp-overexpressing multidrug-resistant variants, suggesting that it is unlikely that the overexpression of P-gp in cancer cells plays a significant role in reduced susceptibility or resistance to branebrutinib. In summary, we discovered an additional pharmacological action of branebrutinib against the activity of P-gp, which should be investigated further in future drug combination studies.

The flavonoid, kaempferol-3-O-apiofuranosyl-7-O-rhamnopyranosyl, as a potential therapeutic agent for breast cancer with a promoting effect on ovarian function

It is widely known that breast cancer cells eventually develop resistance to hormonal drugs and chemotherapies, which often compromise fertility. This study aimed to investigate the effect of the flavonoid, kaempferol-3-O-apiofuranosyl-7-O-rhamnopyranosyl (KARP), on 1) the viability of MCF-7 breast cancer cells and 2) ovarian function in rats. A dose-dependent decrease in MCF-7 cell survival was observed, and the IC50 value was found to be 48 μg/ml. Cells in the control group or those exposed to increasing concentrations of KARP experienced a similar generation of reactive oxygen species and induction of apoptosis. For the rats, estradiol levels correlated negatively to KARP dosages, although a recovery was obtained at administration of 30 mg/kg per day. Noteworthily, when compared against the control, this dosage led to significant increases in mRNA levels for CYP19, CYP17a, CCND2, GDF9, and INSL3 among the treatment groups, and ER1 and ER2 mRNA levels decreased in a dose-dependent manner. KARP shows great promise as an ideal therapy for breast cancer patients since it induced apoptosis and autophagy in cancerous cells without harming fertility in our animal model. Future investigations on humans are necessary to substantiate these findings and determine its efficacy as a general line of treatment.

Treatment of Multiple Myeloma and the Role of Melphalan in the Era of Modern Therapies-Current Research and Clinical Approaches

Multiple myeloma (MM) accounts for 10% of all hematological malignancies, and it is the second most common hematological neoplasm for which chemotherapy is an important pharmacological treatment. High dose melphalan followed by autologous stem cell transplantation remains the standard of treatment for transplant-eligible patients with MM. In this review, we describe aspects of the pharmacokinetics and pharmacodynamics of melphalan therapy and related compounds. In addition, we describe the use of melphalan in innovative therapies for the treatment of MM, including the development of drug carriers to reduce systemic toxicity, combination therapy to improve the effectiveness of cancer therapy, and the chemical modification of the melphalan molecule to improve antitumor activity.

The third-generation EGFR inhibitor almonertinib (HS-10296) resensitizes ABCB1-overexpressing multidrug-resistant cancer cells to chemotherapeutic drugs

The overexpression of the human ATP-binding cassette (ABC) drug transporter ABCB1 (P-glycoprotein, P-gp) or ABCG2 (breast cancer resistance protein, BCRP) in cancer cells often contributes significantly to the development of multidrug resistance (MDR) in cancer patients. Previous reports have demonstrated that some epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) could modulate the activity of ABCB1 and/or ABCG2 in human cancer cells, whereas some EGFR TKIs are transport substrates of these transporters. Almonertinib (HS-10296) is a promising, orally available third-generation EGFR TKI for the treatment of EGFR T790M mutation-positive non-small cell lung cancer (NSCLC) in patients who have progressed on or after other EGFR TKI therapies. Additional clinical trials are currently in progress to study almonertinib as monotherapy and in combination with other agents in patients with NSCLC. In the present work, we found that neither ABCB1 nor ABCG2 confers significant resistance to almonertinib. More importantly, we discovered that almonertinib was able to reverse MDR mediated by ABCB1, but not ABCG2, in multidrug-resistant cancer cells at submicromolar concentrations by inhibiting the drug transport activity of ABCB1 without affecting its expression level. These findings are further supported by in silico docking of almonertinib in the drug-binding pocket of ABCB1. In summary, our study revealed an additional activity of almonertinib to re-sensitize ABCB1-overexpressing multidrug-resistant cancer cells to conventional chemotherapeutic drugs, which may be beneficial for cancer patients and warrant further investigation.

Overexpression of Human ABCB1 and ABCG2 Reduces the Susceptibility of Cancer Cells to the Histone Deacetylase 6-Specific Inhibitor Citarinostat

Citarinostat (ACY-241) is a promising oral histone deacetylase 6 (HDAC6)-selective inhibitor currently in clinical trials for the treatment of multiple myeloma (MM) and non-small-cell lung cancer (NSCLC). However, the inevitable emergence of resistance to citarinostat may reduce its clinical effectiveness in cancer patients and limit its clinical usefulness in the future. In this study, we investigated the potential role of the multidrug efflux transporters ABCB1 and ABCG2, which are two of the most common mechanisms of acquired resistance to anticancer drugs, on the efficacy of citarinostat in human cancer cells. We discovered that the overexpression of ABCB1 or ABCG2 significantly reduced the sensitivity of human cancer cells to citarinostat. We demonstrated that the intracellular accumulation of citarinostat and its activity against HDAC6 were substantially reduced by the drug transport function of ABCB1 and ABCG2, which could be restored by treatment with an established inhibitor of ABCB1 or ABCG2, respectively. In conclusion, our results revealed a novel mechanism by which ABCB1 and ABCG2 actively transport citarinostat away from targeting HDAC6 in cancer cells. Our results suggest that the co-administration of citarinostat with a non-toxic modulator of ABCB1 and ABCG2 may optimize its therapeutic application in the clinic.

Therapeutic strategies to overcome taxane resistance in cancer

One of the primary causes of attenuated or loss of efficacy of cancer chemotherapy is the emergence of multidrug resistance (MDR). Numerous studies have been published regarding potential approaches to reverse resistance to taxanes, including paclitaxel (PTX) and docetaxel, which represent one of the most important classes of anticancer drugs. Since 1984, following the FDA approval of paclitaxel for the treatment of advanced ovarian carcinoma, taxanes have been extensively used as drugs that target tumor microtubules. Taxanes, have been shown to affect an array of oncogenic signaling pathways and have potent cytotoxic efficacy. However, the clinical success of these drugs has been restricted by the emergence of cancer cell resistance, primarily caused by the overexpression of MDR efflux transporters or by microtubule alterations. In vitro and in vivo studies indicate that the mechanisms underlying the resistance to PTX and docetaxel are primarily due to alterations in α-tubulin and β-tubulin. Moreover, resistance to PTX and docetaxel results from: 1) alterations in microtubule-protein interactions, including microtubule-associated protein 4, stathmin, centriole, cilia, spindle-associated protein, and kinesins; 2) alterations in the expression and activity of multidrug efflux transporters of the ABC superfamily including P-glycoprotein (P-gp/ABCB1); 3) overexpression of anti-apoptotic proteins or inhibition of apoptotic proteins and tumor-suppressor proteins, as well as 4) modulation of signal transduction pathways associated with the activity of several cytokines, chemokines and transcription factors. In this review, we discuss the abovementioned molecular mechanisms and their role in mediating cancer chemoresistance to PTX and docetaxel. We provide a detailed analysis of both in vitro and in vivo experimental data and describe the application of these findings to therapeutic practice. The current review also discusses the efficacy of different pharmacological modulations to achieve reversal of PTX resistance. The therapeutic roles of several novel compounds, as well as herbal formulations, are also discussed. Among them, many structural derivatives had efficacy against the MDR phenotype by either suppressing MDR or increasing the cytotoxic efficacy compared to the parental drugs, or both. Natural products functioning as MDR chemosensitizers offer novel treatment strategies in patients with chemoresistant cancers by attenuating MDR and increasing chemotherapy efficacy. We broadly discuss the roles of inhibitors of P-gp and other efflux pumps, in the reversal of PTX and docetaxel resistance in cancer cells and the significance of using a nanomedicine delivery system in this context. Thus, a better understanding of the molecular mechanisms mediating the reversal of drug resistance, combined with drug efficacy and the application of target-based inhibition or specific drug delivery, could signal a new era in modern medicine that would limit the pathological consequences of MDR in cancer patients.

Activation of Serum/Glucocorticoid Regulated Kinase 1/Nuclear Factor-κB Pathway Are Correlated with Low Sensitivity to Bortezomib and Ixazomib in Resistant Multiple Myeloma Cells

Multiple myeloma (MM) is an incurable malignancy often associated with primary and acquired resistance to therapeutic agents, such as proteasome inhibitors. However, the mechanisms underlying the proteasome inhibitor resistance are poorly understood. Here, we elucidate the mechanism of primary resistance to bortezomib and ixazomib in the MM cell lines, KMS-20, KMS-26, and KMS-28BM. We find that low bortezomib and ixazomib concentrations induce cell death in KMS-26 and KMS-28BM cells. However, high bortezomib and ixazomib concentrations induce cell death only in KMS-20 cells. During Gene Expression Omnibus analysis, KMS-20 cells exhibit high levels of expression of various genes, including anti-phospho-fibroblast growth factor receptor 1 (FGFR1), chemokine receptor type (CCR2), and serum and glucocorticoid regulated kinase (SGK)1. The SGK1 inhibitor enhances the cytotoxic effects of bortezomib and ixazomib; however, FGFR1 and CCR2 inhibitors do not show such effect in KMS-20 cells. Moreover, SGK1 activation induces the phosphorylation of NF-κB p65, and an NF-κB inhibitor enhances the sensitivity of KMS-20 cells to bortezomib and ixazomib. Additionally, high levels of expression of SGK1 and NF-κB p65 is associated with a low sensitivity to bortezomib and a poor prognosis in MM patients. These results indicate that the activation of the SGK1/NF-κB pathway correlates with a low sensitivity to bortezomib and ixazomib, and a combination of bortezomib and ixazomib with an SGK1 or NF-κB inhibitor may be involved in the treatment of MM via activation of the SGK1/NF-κB pathway.

Erdafitinib Resensitizes ABCB1-Overexpressing Multidrug-Resistant Cancer Cells to Cytotoxic Anticancer Drugs

The development of multidrug resistance (MDR) in cancer patients, which is often associated with the overexpression of ABCB1 (MDR1, P-glycoprotein) in cancer cells, remains a significant problem in cancer chemotherapy. ABCB1 is one of the major adenosine triphosphate (ATP)-binding cassette (ABC) transporters that can actively efflux a range of anticancer drugs out of cancer cells, causing MDR. Given the lack of Food and Drug Administration (FDA)-approved treatment for multidrug-resistant cancers, we explored the prospect of repurposing erdafitinib, the first fibroblast growth factor receptor (FGFR) kinase inhibitor approved by the FDA, to reverse MDR mediated by ABCB1. We discovered that by reducing the function of ABCB1, erdafitinib significantly resensitized ABCB1-overexpressing multidrug-resistant cancer cells to therapeutic drugs at sub-toxic concentrations. Results of erdafitinib-stimulated ABCB1 ATPase activity and in silico docking analysis of erdafitinib binding to the substrate-binding pocket of ABCB1 further support the interaction between erdafitinib and ABCB1. Moreover, our data suggest that ABCB1 is not a major mechanism of resistance to erdafitinib in cancer cells. In conclusion, we revealed an additional action of erdafitinib as a potential treatment option for multidrug-resistant cancers, which should be evaluated in future drug combination trials.

Dasatinib reverses drug resistance by downregulating MDR1 and Survivin in Burkitt lymphoma cells

Background

Current chemotherapies for Burkitt lymphoma (BL) have dramatically improved its clinical outcome. However, chemoresistance can lead to chemotherapy failure and very poor prognosis; thus, novel strategies are urgently required for patients with drug-resistant BL. To investigate the mechanisms underlying drug resistance in BL, we established drug-resistant BL cell lines: HS-Sultan/ADM (adriamycin-resistant), HS-Sultan/VCR (vincristine-resistant), HS-Sultan/DEX (dexamethasone-resistant), and HS-Sultan/L-PAM (melphalan-resistant).

Methods

Drug transporter and survival factor expression were investigated the using western blotting and real time polymerase chain reaction. Cell survival was analyzed by trypan blue dye exclusion method.

Results

The established cell lines acquired cross-resistance to adriamycin, vincristine, dexamethasone, and melphalan and exhibited 50% inhibitory concentration values 106-, 40-, 81-, and 45-fold higher than the parental cell lines, respectively. We found that protein and mRNA expression of MDR1 and Survivin were higher in drug-resistant BL cells than in the parent cells. Treatment with verapamil, an MDR1 inhibitor, or Survivin siRNA alongside each anti-cancer drug suppressed the proliferation of all drug-resistant BL cells. Src kinase activity was higher in all resistant cell lines than the parental cells; suppressing Src with dasatinib restored drug sensitivity by reducing MDR1 and Survivin expression.

Conclusions

MDR1 and Survivin upregulation are responsible for resistance to conventional drugs and dasatinib can restore drug sensitivity by reducing MDR1 and Survivin expression in drug-resistant BL cells. Src inhibitors could therefore be a novel treatment strategy for patients with drug resistant BL.

Genetic polymorphisms and multiple myeloma risk: a meta-analysis

Previous researches exploring associations between multiple myeloma (MM) and genetic polymorphisms showed controversial results. In this investigation, we aimed to make a meta-analysis to assess the association between MM risk and genetic polymorphisms. We searched for articles on genetic polymorphism and MM risk in Web of Science and PubMed databases from 1951 to August 2019. We computed the odds ratio (OR) and 95% confidence intervals (CI) extracted from included articles. The meta-analysis showed no significant associations between MM risks and tumor necrosis factor (TNF)-α (rs1800629/rs361525/rs1799724), interleukin (IL)-6 (rs1800795), multidrug resistance 1 (MDR1) (rs1045642), Methylenetetrahydrofolate reductase (MTHFR) (rs1801131/rs1801133) polymorphisms. In summary, the study shows that the TNF-α (rs1800629/rs361525/rs1799724), IL-6 (rs1800795), MDR1 (rs1045642), and MTHFR (rs1801131/rs1801133) polymorphisms may not be associated with MM susceptibility. Thus, we do not need more expensive and useless studies to explore the associations between MM risks and these genetic polymorphisms.

Inhibition of HSP90 overcomes melphalan resistance through downregulation of Src in multiple myeloma cells

Multiple myeloma (MM) is the second most common hematologic malignancy. In spite of the development of new therapeutic agents, MM remains incurable due to multidrug resistance (MDR) and the 5-year survival rate is approximately 50%. Thus, further study is needed to investigate the mechanism of MDR and improve MM prognosis. Heat shock protein 90 (HSP90) is a molecular chaperone that is responsible for the stability of a number of client proteins, most of which are involved in tumor progression. Therefore, HSP90 inhibitors represent potential new therapeutic agents for cancer. Furthermore, inhibition of HSP90 leads to degradation of client proteins, overcoming acquired anti-cancer drug resistance. In this study, we assessed the role of HSP90 in MDR using established melphalan-resistant MM cells. We found that expression of HSP90 was higher in melphalan-resistant MM cells than in parent cells and that HSP90 inhibitors KW-2478 and NUV-AUY922 restored drug sensitivity to the level observed in parent cells. Activation of the unfolded protein response is a hallmark of MM, and expression of endoplasmic reticulum stress signaling molecules is reduced in melphalan-resistant cells; however, KW-2478 did not affect endoplasmic reticulum stress signaling. We demonstrated that treatment with KW-2478 decreased expression of Src, a client of HSP90, and suppressed the activity of ERK, Akt, and NF-κB. Our findings indicate that inhibition of HSP90 results in suppression of Src and its downstream effectors, including ERK, Akt, and NF-κB, and therefore that HSP90 inhibitors could be useful for treatment of MDR MM.

Sitravatinib Sensitizes ABCB1- and ABCG2-Overexpressing Multidrug-Resistant Cancer Cells to Chemotherapeutic Drugs

The development of multidrug resistance (MDR) in cancer patients driven by the overexpression of ATP-binding cassette (ABC) transporter ABCB1 or ABCG2 in cancer cells presents one of the most daunting therapeutic complications for clinical scientists to resolve. Despite many novel therapeutic strategies that have been tested over the years, there is still no approved treatment for multidrug-resistant cancers to date. We have recently adopted a drug repurposing approach to identify therapeutic agents that are clinically active and at the same time, capable of reversing multidrug resistance mediated by ABCB1 and ABCG2. In the present study, we investigated the effect of sitravatinib, a novel multitargeted receptor tyrosine kinase inhibitor, on human ABCB1 and ABCG2 in multidrug-resistant cancer cell lines. We discovered that at submicromolar concentrations, sitravatinib re-sensitizes ABCB1- and ABCG2-overexpressing multidrug-resistant cancer cells to chemotherapeutic drugs. We found that sitravatinib blocks the drug efflux function of ABCB1 and ABCG2 in a concentration-dependent manner but does not significantly alter the protein expression of ABCB1 or ABCG2 in multidrug-resistant cancer cells. In conclusion, we reveal a potential drug repositioning treatment option for multidrug-resistant cancers by targeting ABCB1 and ABCG2 with sitravatinib and should be further investigated in future clinical trials.

The Selective Class IIa Histone Deacetylase Inhibitor TMP195 Resensitizes ABCB1- and ABCG2-Overexpressing Multidrug-Resistant Cancer Cells to Cytotoxic Anticancer Drugs

Multidrug resistance caused by the overexpression of the ATP-binding cassette (ABC) proteins in cancer cells remains one of the most difficult challenges faced by drug developers and clinical scientists. The emergence of multidrug-resistant cancers has driven efforts from researchers to develop innovative strategies to improve therapeutic outcomes. Based on the drug repurposing approach, we discovered an additional action of TMP195, a potent and selective inhibitor of class IIa histone deacetylase. We reveal that in vitro TMP195 treatment significantly enhances drug-induced apoptosis and sensitizes multidrug-resistant cancer cells overexpressing ABCB1 or ABCG2 to anticancer drugs. We demonstrate that TMP195 inhibits the drug transport function, but not the protein expression of ABCB1 and ABCG2. The interaction between TMP195 with these transporters was supported by the TMP195-stimulated ATPase activity of ABCB1 and ABCG2, and by in silico docking analysis of TMP195 binding to the substrate-binding pocket of these transporters. Furthermore, we did not find clear evidence of TMP195 resistance conferred by ABCB1 or ABCG2, suggesting that these transporters are unlikely to play a significant role in the development of resistance to TMP195 in cancer patients.

Andrographolide as a Therapeutic Agent Against Breast and Ovarian Cancers

Andrographolide (ANDR), isolated from Andrographis paniculata, is a medicinal compound effective against infections, inflammatory disorders, and various cancers. In the present study, the effects of ANDR on NFkB (nuclear factor kappa-light-chain-enhancer of activated B cells) activation, caspase-8-mediated apoptosis and pyroptosis, and extra cellular matrix (ECM) degradation were analyzed in A431, MDA-MB231, and SKOV-3 cell lines. Results showed that ANDR inhibited the growth and proliferation of cancer cell lines by inhibiting NFkB signaling. A significant decrease in phospho-p65 level was observed upon increasing ANDR concentration in epidermoid carcinoma and breast cancer cell lines, A431 and MDA-MB231, respectively. Accordingly, upon ANDR treatment, the expression of caspase-8 was increased, whereas no significant induction of caspase-1 expression was observed. Moreover, we observed a significant increase in the expression of tissue inhibitor of metallopeptidase-1 (TIMP1) upon increasing ANDR concentration. Such induction of TIMP1 inhibited the activity of matrix metallopeptidase-7 (MMP-7), thus preventing the degradation of ECM. Therefore, as ANDR shows cytotoxicity towards cancer cells via the NFkB signal transduction pathway without inducing pyroptosis and blocks breast and ovarian cancer invasion by inhibiting MMP-7 expression through TIMP1 up-regulation, it has the potential to be developed as a drug targeting ovarian and breast cancers.

Codelivery of DOX and siRNA by folate-biotin-quaternized starch nanoparticles for promoting synergistic suppression of human lung cancer cells

In this paper, the self-assembled folate-biotin-quaternized starch nanoparticles (FBqS NPs) were used as carrier system of doxorubicin (DOX) and siRNAIGF1R for the codelivery of both into human lung adenocarcinoma cell lines (A549 cells) in vitro. The cytotoxicity, targeted ligand competition, cell proliferation inhibition, cellular uptake, endocytosis mechanism and target protein suppression of drug-loaded FBqS NPs were evaluated in detail. Compared with several other drug formulations under same condition, siRNAIGF1R/DOX/FBqS NPs exhibited the greatest cytotoxicity to A549 cells and the cytotoxicity was competitively inhibited by free folate in dose-dependent manner. The A549 cells treated by siRNAIGF1R/DOX/FBqS NPs showed the lowest cell proliferation capacity. The energy-dependent clathrin- and caveolae-mediated endocytosis might be the primary cellular uptake mechanism of drug-loaded FBqS NPs. The expression of IGF1R protein in A549 cells treated by siRNAIGF1R/FBqS NPs declined dramatically. So the FBqS NPs were expected as the co-carrier system of chemotherapeutants and siRNAs for future clinical application.

Overactivation of Akt Contributes to MEK Inhibitor Primary and Acquired Resistance in Colorectal Cancer Cells

RAS and BRAF-mutated colorectal cancers are associated with resistance to chemotherapy and poor prognosis, highlighting the need for new therapeutic strategies. Although these cancers sometimes respond to mitogen activated protein kinase kinase (MEK) inhibitor treatment, they often acquire resistance via mechanisms, which are poorly understood. Here, we investigated the mechanism of MEK inhibitor resistance in primary- and acquired-resistant cells. Cell viability was examined using the trypan blue dye exclusion assay. Protein expression was analyzed by western blotting. Somatic mutations in colorectal cancer cells were investigated using the polymerase chain reaction array. PD0325901 and trametinib induced cell death in LoVo and Colo-205 cells but not in DLD-1 and HT-29 cells, which have a PIK3CA mutation constitutively activating Akt and NF-κB. Treatment with PD0325901 and trametinib suppressed ERK1/2 activation in all four cell lines but only induced Akt and NF-κB activation in DLD-1 and HT-29 cells. Inhibition of Akt but not NF-κB, overcame MEK inhibitor resistance in DLD-1 and HT-29 cells. Acquired-resistant LoVo/PR, Colo-205/PR and LoVo/TR cells have constitutively active Akt due to a M1043V mutation in the kinase activation loop of PIK3CA and Akt inhibitor resensitized these cells to MEK inhibitor. These results demonstrate that the overactivation of Akt plays a critical role in MEK inhibitor primary and acquired resistance and implicate combined Akt/MEK inhibition as a potentially useful treatment for RAS/BRAF-mutated colorectal cancer.

Molecular Mechanism of Matrine from Sophora alopecuroides in the Reversing Effect of Multi-Anticancer Drug Resistance in K562/ADR Cells

Multidrug resistance is the main obstacle to current chemotherapies. In this study, we evaluated the reversing effect of matrine, the principal alkaloid derived from Sophora alopecuroides, on chemoresistant leukemia K562/ADR cells. Matrine in a range of the nontoxic concentration was employed in the whole study. IC₅₀s of cancer medicines were tested using WST-8 assay. Drug export and apoptotic rates were examined using flow cytometry. The mRNA and protein expressions were quantified by quantitative real-time PCR and western blotting, respectively. Our data indicated that matrine had potent reversal properties augmenting cytotoxicity of cancer medicines on K562/ADR cells as well as apoptotic rates induced by doxorubicin. Moreover, matrine inhibited drug-exporting activity and expression of ATP-binding cassette subfamily B member 1 (ABCB1) on both mRNA and protein levels. That might result from inhibited NF-kappa B activation, which also led to restored intrinsic apoptosis. These findings suggest that matrine in the nontoxic concentration can suppress ABCB1 drug transport and facilitate the intrinsic apoptosis pathway through the inhibiting effect on NF-kappa B and has the potential to become an efficient sensitizer for anticancer drug resistance.

Aspirin inhibits cancer stem cells properties and growth of glioblastoma multiforme through Rb1 pathway modulation

Several clinical studies indicated that the daily use of aspirin or acetylsalicylic acid reduces the cancer risk via cyclooxygenases (Cox-1 and Cox-2) inhibition. In addition, aspirin-induced Cox-dependent and -independent antitumor effects have also been described. Here we report, for the first time, that aspirin treatment of human glioblastoma cancer (GBM) stem cells, a small population responsible for tumor progression and recurrence, is associated with reduced cell proliferation and motility. Aspirin did not interfere with cell viability but induced cell-cycle arrest. Exogenous prostaglandin E₂ significantly increased cell proliferation but did not abrogate the aspirin-mediated growth inhibition, suggesting a Cox-independent mechanism. These effects appear to be mediated by the increase of p21 ^waf1 and p27 ^Kip1 , associated with a reduction of Cyclin D1 and Rb1 protein phosphorylation, and involve the downregulation of key molecules responsible for tumor development, that is, Notch1, Sox2, Stat3, and Survivin. Our results support a possible role of aspirin as adjunctive therapy in the clinical management of GBM patients.

In-Vitro and In-Vivo Establishment and Characterization of Bioluminescent Orthotopic Chemotherapy-Resistant Human Osteosarcoma Models in NSG Mice

Osteosarcoma, the most common bone malignancy with a peak incidence at adolescence, had no survival improvement since decades. Persistent problems are chemo-resistance and metastatic spread. We developed in-vitro osteosarcoma models resistant to chemotherapy and in-vivo bioluminescent orthotopic cell-derived-xenografts (CDX). Continuous increasing drug concentration cultures in-vitro resulted in five methotrexate (MTX)-resistant and one doxorubicin (DOXO)-resistant cell lines. Resistance persisted after drug removal except for MG-63. Different resistance mechanisms were identified, affecting drug transport and action mechanisms specific to methotrexate (RFC/SCL19A1 decrease, DHFR up-regulation) for MTX-resistant lines, or a multi-drug phenomenon (PgP up-regulation) for HOS-R/DOXO. Differential analysis of copy number abnormalities (aCGH) and gene expression (RNAseq) revealed changes of several chromosomic regions translated at transcriptomic level depending on drug and cell line, as well as different pathways implicated in invasive and metastatic potential (e.g., Fas, Metalloproteinases) and immunity (enrichment in HLA cluster genes in 6p21.3) in HOS-R/DOXO. Resistant-CDX models (HOS-R/MTX, HOS-R/DOXO and Saos-2-B-R/MTX) injected intratibially into NSG mice behaved as their parental counterpart at primary tumor site; however, they exhibited a slower growth rate and lower metastatic spread, although they retained resistance and CGH main characteristics without drug pressure. These models represent valuable tools to explore resistance mechanisms and new therapies in osteosarcoma.

Avapritinib: A Selective Inhibitor of KIT and PDGFRα that Reverses ABCB1 and ABCG2-Mediated Multidrug Resistance in Cancer Cell Lines

The frequent occurrence of multidrug resistance (MDR) conferred by the overexpression of ATP-binding cassette (ABC) transporters ABCB1 and ABCG2 in cancer cells remains a therapeutic obstacle for scientists and clinicians. Consequently, developing or identifying modulators of ABCB1 and ABCG2 that are suitable for clinical practice is of great importance. Therefore, we have explored the drug repositioning approach to identify candidate modulators of ABCB1 and ABCG2 from tyrosine kinase inhibitors with known pharmacological properties and anticancer activities. In this study, we discovered that avapritinib (BLU-285), a potent, selective, and orally bioavailable tyrosine kinase inhibitor against mutant forms of KIT and platelet-derived growth factor receptor alpha (PDGFRA), attenuates the transport function of both ABCB1 and ABCG2. Moreover, avapritinib restores the chemosensitivity of ABCB1- and ABCG2-overexpressing MDR cancer cells at nontoxic concentrations. These findings were further supported by results of apoptosis induction assays, ATP hydrolysis assays, and docking of avapritinib in the drug-binding pockets of ABCB1 and ABCG2. Altogether, our study highlights an additional action of avapritinib on ABC drug transporters, and a combination of avapritinib with conventional chemotherapy should be further investigated in patients with MDR tumors.

The FLT3 inhibitor midostaurin selectively resensitizes ABCB1-overexpressing multidrug-resistant cancer cells to conventional chemotherapeutic agents

The occurrence of multidrug resistance (MDR) associated with the overexpression of the ATP-binding cassette (ABC) protein ABCB1 in cancer cells remains a significant obstacle to successful cancer chemotherapy. Therefore, discovering modulators that are capable of inhibiting the drug efflux function or expression of ABCB1 and re-sensitizing multidrug-resistant cancer cells to anticancer agents is of great clinical importance. Regrettably, due to potential adverse events associated with drug-drug interactions and toxicity in patients, researchers have struggled to develop a synthetic inhibitor of ABCB1 that is clinically applicable to improve the effectiveness of chemotherapy. Alternatively, through drug repositioning of approved drugs, we discovered that the FMS-like tyrosine kinase-3 (FLT3) inhibitor midostaurin blocks the drug transport function of ABCB1 and re-sensitizes ABCB1-overexpressing multidrug-resistant cancer cells to conventional chemotherapeutic drugs. Our findings were further supported by results demonstrating that midostaurin potentiates drug-induced apoptosis in ABCB1-overexpressing cancer cells and inhibits the ATPase activity of ABCB1. Considering that midostaurin is a clinically approved anticancer agent, our findings revealed an additional action of midostaurin and that patients with multidrug-resistant tumors may benefit from a combination therapy of midostaurin with standard chemotherapy, which should be further investigated.

Overexpression of HIF-1α contributes to melphalan resistance in multiple myeloma cells by activation of ERK1/2, Akt, and NF-κB

Multiple myeloma (MM) commonly displays multidrug resistance and is associated with poor prognosis. Therefore, it is important to identify the mechanisms by which MM cells develop multidrug resistance. Our previous study showed that multidrug resistance is correlated with overexpression of multidrug resistance protein 1 (MDR1) and Survivin, and downregulation of Bim expression in melphalan-resistant RPMI8226/L-PAM cells; however, the underlying mechanism of multidrug resistance remains unclear. In the present study, we investigated the mechanism of multidrug resistance in melphalan-resistant cells. We found that RPMI8226/L-PAM and ARH-77/L-PAM cells showed increased phosphorylation of extracellular signal-regulated protein kinase 1/2 (ERK1/2) and Akt, and nuclear localization of nuclear factor κB (NF-κB). The combination of ERK1/2, Akt, and NF-κB inhibitors with melphalan reversed melphalan resistance via suppression of Survivin expression and enhanced Bim expression in melphalan-resistant cells. In addition, RPMI8226/L-PAM and ARH-77/L-PAM cells overexpressed hypoxia-inducible factor 1α (HIF-1α) via activation of ERK1/2, Akt, and NF-κB. Moreover, suppression of HIF-1α by echinomycin or HIF-1α siRNA resensitized RPMI8226/L-PAM cells to melphalan through downregulation of Survivin expression and upregulation of Bim expression. These results indicate that enhanced Survivin expression and decreased Bim expression by HIF-1α via activation of ERK1/2, Akt, and NF-κB play a critical role in melphalan resistance. Our findings suggest that HIF-1α, ERK1/2, Akt, and NF-κB inhibitors are potentially useful as anti-MDR agents for the treatment of melphalan-resistant MM.

The positive inotropic agent DPI-201106 selectively reverses ABCB1-mediated multidrug resistance in cancer cell lines

The overexpression of ABCB1 in cancer cells is a major factor contributing to the development of multidrug resistance (MDR) and treatment failure in cancer patients. Therefore, re-sensitization of MDR cancer cells to anticancer drugs remains an important aspect in chemotherapy. The progress in developing clinically applicable synthetic inhibitors of ABCB1 has been slow, mostly due to complications associated with intrinsic toxicities and unforeseen drug-drug interactions. Here, we explored the drug-repositioning approach for cancer therapy by targeting ABCB1-mediated MDR in human cancer cells. We found that DPI-201106, a positive inotropic agent, selectively inhibits the drug efflux function of ABCB1, and in doing so, re-sensitizes ABCB1-overexpressing MDR cancer cells to conventional anticancer drugs. Furthermore, the ATPase activity of ABCB1 and docking analysis of DPI-201106 in the drug-binding pocket of ABCB1 were determined to confirm the interaction between DPI-201106 and ABCB1 protein. In summary, we revealed an additional action and a potential clinical application of DPI-201106 to reverse ABCB1-mediated MDR in human cancer cells, which may be beneficial for cancer patients who have developed multidrug resistance and no longer respond to conventional chemotherapy, and should be further investigated.

Human ATP-binding cassette transporters ABCB1 and ABCG2 confer resistance to histone deacetylase 6 inhibitor ricolinostat (ACY-1215) in cancer cell lines

Ricolinostat is the first orally available, selective inhibitor of histone deacetylase 6 (HDAC6), currently under evaluation in clinical trials in patients with various malignancies. It is likely that the inevitable emergence of resistance to ricolinostat is likely to reduce its clinical effectiveness in cancer patients. In this study, we investigated the potential impact of multidrug resistance-linked ATP-binding cassette (ABC) transporters ABCB1 and ABCG2 on the efficacy of ricolinostat, which may present a major hurdle to its development as an anticancer drug in the future. We demonstrated that the overexpression of ABCB1 or ABCG2 reduces the intracellular accumulation of ricolinostat, resulting in reduced efficacy of ricolinostat to inhibit the activity of HDAC6 in cancer cells. Moreover, the efficacy of ricolinostat can be fully restored by inhibiting the drug efflux function of ABCB1 and ABCG2 in drug-resistant cancer cells. In conclusion, our results provide some insights into the basis for the development of resistance to ricolinostat and suggest that co-administration of ricolinostat with a modulator of ABCB1 or ABCG2 could overcome ricolinostat resistance in human cancer cells, which may be relevant to its use in the clinic.

SIS3, a specific inhibitor of Smad3 reverses ABCB1- and ABCG2-mediated multidrug resistance in cancer cell lines

One of the major challenges in cancer chemotherapy is the development of multidrug resistance phenomenon attributed to the overexpression of ATP-binding cassette (ABC) transporter ABCB1 or ABCG2 in cancer cells. Therefore, re-sensitizing MDR cancer cells to chemotherapy by directly inhibiting the activity of ABC transporters has clinical relevance. Unfortunately, previous attempts of developing clinically applicable synthetic inhibitors have failed, mostly due to problems associated with toxicity and unforeseen drug-drug interactions. An alternative approach is by repositioning drugs with known pharmacological properties as modulators of ABCB1 and ABCG2. In this study, we discovered that the transport function of ABCB1 and ABCG2 is strongly inhibited by SIS3, a specific inhibitor of Smad3. More importantly, SIS3 enhances drug-induced apoptosis and resensitizes ABCB1- and ABCG2-overexpressing cancer cells to chemotherapeutic drugs at non-toxic concentrations. These findings are further supported by ATPase assays and by a docking analysis of SIS3 in the drug-binding pockets of ABCB1 and ABCG2. In summary, we revealed an additional action of SIS3 that re-sensitizes MDR cancer cells and a combination therapy with this drug and other chemotherapeutic agents may be beneficial for patients with MDR tumors.

The novel compound STK405759 is a microtubule-targeting agent with potent and selective cytotoxicity against multiple myeloma in vitro and in vivo

Despite advances in treatment, multiple myeloma (MM) remains incurable. Here we propose the use of STK405759, a novel microtubule targeting agent (MTA) and member of the furan metotica family for MM therapy.

STK405759 inhibited tubulin polymerization in a cell-free system and in myeloma cells. This molecule had potent cytotoxic activity against several MM cell lines and patient-derived MM cells. Moreover, STK405759 demonstrated cytotoxicity against drug-resistant myeloma cells that overexpressed the P-glycoprotein drug-efflux pump. STK405759 was not cytotoxic to peripheral blood mononuclear cells, including activated B and T lymphocytes. This compound caused mitotic arrest and apoptosis of myeloma cells characterized by cleavage of poly (ADP-ribose) polymerase-1 and caspase-8, as well as decreased protein expression of mcl-1. The combination of STK405759 with bortezomib, lenalidomide or dexamethasone had synergistic cytotoxic activity. In in vivo studies, STK405759-treated mice had significantly decreased MM tumor burden and prolonged survival compared to vehicle treated- mice.

These results provide a rationale for further evaluation of STK405759 as monotherapy or part of combination therapy for treating patients with MM.

Multidrug resistance 1 (MDR1/ABCB1) gene polymorphism (rs1045642 C > T) and susceptibility to multiple myeloma: a systematic review and meta-analysis

INTRODUCTION

Several studies have evaluated the association between the multidrug resistance 1 (MDR1) polymorphism (rs1045642 C > T) and multiple myeloma (MM). However, the results were not consistent. Therefore, to reach a comprehensive and reliable answer we determined the association of the MDR1 (rs1045642 C > T) polymorphism and MM in the context of meta-analysis.

METHODS

All eligible studies published in EMBASE, PubMed, and Web of Science databases before July 2017 were reviewed. Subsequently, to assess the strength of association in the dominant model, recessive model, allelic model, homozygotes contrast, and heterozygotes contrast, pooled odds ratios and 95% confidence intervals (CIs) were calculated by the fixed effects model.

RESULTS

A total of four case-control studies with 395 MM cases and 418 healthy controls were included in the meta-analysis. The overall results showed no significant association between the MDR1 (rs1045642 C > T) polymorphism and the risk of MM in genetic models (dominant model: OR = 1.04, 95% CI = 0.78-1.38; recessive model: OR = 0.74, 95% CI = 0.52-1.06; allelic model: OR = 0.90, 95% CI = 0.73-1.11; TT vs. CC: OR = 0.80, 95% CI = 0.51-1.25; and CT vs. CC: OR = 1.12, 95% CI = 0.77-1.62). No evidence of publication bias was detected except for the analysis of the recessive model.

CONCLUSION

This meta-analysis suggests that the MDR1 C > T polymorphism was not associated with the risk of MM. To confirm these findings, further comprehensive and well-designed studies are needed.

Bavachin induces the apoptosis of multiple myeloma cell lines by inhibiting the activation of nuclear factor kappa B and signal transducer and activator of transcription 3

Bavachin is a phytoestrogen purified from natural herbal plants such as Psoralea corylifolia. In this study, we examined the effect of bavachin in multiple myeloma (MM) cell lines. We found that bavachin decreased the viability of MM cell lines, but was not cytotoxic towards normal cells. It inhibited the activation of nuclear factor kappa B (NF-κB) and signal transducer and activator of transcription 3 (STAT3). Furthermore, bavachin increased the expression of p53 and NOXA, and decreased the expression of X-linked inhibitor of apoptosis protein (XIAP), survivin, B cell lymphoma-extra large (Bcl-xL), and Bcl-2. Additionally, bavachin induced apoptosis by the activation of caspase-3 and caspase-9, implicating the involvement of the mitochondrial pathway. Our results suggest that bavachin induces apoptosis through the inhibition of NF-κB and STAT3 activation in MM cell lines. Most importantly, few NF-κB and STAT3 inhibitors with high efficiency, specificity, and safety are currently available for clinical cancer therapy. Hence, bavachin, which targets NF-κB and STAT3, is a potential anticancer agent for the treatment of MM.

The MIP-1α autocrine loop contributes to decreased sensitivity to anticancer drugs

Several autocrine soluble factors, including macrophage inflammatory protein-1α (MIP-1α), tumor necrosis factor-α, and hepatocyte growth factor, promote cell survival and growth in multiple myeloma (MM) cells. We hypothesized that inhibition of the MIP-1α autocrine loop may enhance the cytotoxic effect of anticancer drugs in MM cell lines. In the present study, an MIP-1α neutralizing antibody suppressed cell proliferation and enhanced the cytotoxic effect of melphalan or bortezomib on MM cells. In addition, melphalan resistance cells (RPMI8226/L-PAM and HS-sultan/L-PAM cells) secreted MIP-1α and neutralizing antibody of MIP-1α partially overcame melphalan resistance. Moreover, combination treatment with MIP-1α neutralizing antibody and melphalan or bortezomib inhibited extracellular signal regulated kinase 1/2 (ERK1/2), Akt, and mammalian target of rapamycin (mTOR) activation, Bcl-2, Bcl-xL, and Survivin expression, and upregulated the expression of Bim and cleaved Poly (ADP-ribose) polymerase (PARP). Treatment of IM9 cells with MIP-1α siRNA suppressed the activation of ERK1/2, Akt, and mTOR, and enhanced the cytotoxic effect of melphalan and bortezomib. These results indicate that MIP-1α neutralizing antibodies or MIP-1α siRNA enhance the cytotoxic effect of melphalan and bortezomib by suppressing the chemokine receptor/ERK and chemokine receptor/Akt/mTOR pathways. The inhibition of MIP-1α may thus provide a new therapeutic approach to control tumor progression and bone destruction in patients with MM.

Astragalus polysaccharides increase the sensitivity of SKOV3 cells to cisplatin

BACKGROUND

Multidrug resistance in malignant tumours hinders the treatment of tumours. Studies showed that astragalus polysaccharides (APS), one major active ingredient of astragalus, enhanced the sensitivity of non-small cell lung cancer and liver cancer cells to chemotherapeutic drug. However, the effect of APS on ovarian cancer is still unclear. In this study, we will examine the sensitizing effect of APS on SKOV3 cells to cisplatin and explore the possible mechanism.

METHODS

MTT assay was employed to examine the viability of SKOV3 after treatment with APS and cisplatin. The cell apoptosis rate was determined by flow cytometry. The expression of Bax, Bcl-2, Caspase-3, and c-Jun N-terminal kinases 1/2 (JNK1/2) was measured using Western blotting and RT-PCR.

RESULTS

APS synergistically promoted the inhibitory effect of cisplatin on SKOV3 cell viability. Flow cytometry showed that APS promoted cisplatin-induced apoptosis of SKOV3 cell lines. Further studies showed that APS down-regulated the expression of Bcl2, increased the expression of Bax and caspase 3 and activated JNK1/2 signalling pathway. The JNK inhibitors significantly rescued the proliferation inhibition induced by the drugs.

CONCLUSIONS

Astragalus polysaccharides increased the sensitivity of SKOV3 cells to cisplatin potentially by activating the JNK pathway. The apoptosis-related genes may contribute to the process. Thus, APS may be useful for the treatment of ovarian cancer as an enhancer of chemosensitivity.

Aspirin enhances the cytotoxic activity of bortezomib against myeloma cells via suppression of Bcl-2, survivin and phosphorylation of AKT

In our previous study, it was found that aspirin (ASA) exerted antimyeloma actions in vivo and in vitro. The resistance to bortezomib (BTZ) in multiple myeloma (MM) is partly due to AKT activation and the upregulation of survivin induced by BTZ, which are the targets of ASA in gastric and ovarian cancer, respectively. Thus, the present study investigated the interaction between ASA and BTZ in MM and further clarified the underlying mechanisms. MM1.S and RPMI-8226 cell lines harboring the N- and K-Ras mutations, respectively, were treated with 2.5 mM ASA, 10 nM BTZ and ASA+BTZ for different durations. The proliferation and apoptosis of the cells were determined, and the underlying mechanisms governing the interaction of ASA and BTZ were examined in the MM cells. Treatment with ASA+BTZ caused higher rates of proliferative inhibition and apoptosis in the MM1.S and RPMI-8226 cells in time-dependent manner, compared with either agent alone. A drug interaction assay revealed the additive effect of ASA and BTZ on the myeloma cells. ASA alone inhibited the levels of phosphorylated AKT (p-AKT) and survivin, whereas BTZ alone augmented the levels of p-AKT and survivin. Of note, ASA markedly decreased the upregulation of p-AKT and survivin induced by BTZ. Treatment with ASA+BTZ significantly suppressed the level of Bcl-2, compared with either agent alone. ASA may potentiate the antimyeloma activity of BTZ against myeloma cells via suppression of AKT phosphorylation, survivin and Bcl-2, indicating the potential of ASA+BTZ in treating MM, particularly for cases of BTZ-refractory/relapsed MM.

TrxR1 inhibition overcomes both hypoxia-induced and acquired bortezomib resistance in multiple myeloma through NF-кβ inhibition

Multiple myeloma (MM) is a B-cell malignancy characterized by an accumulation of abnormal clonal plasma cells in the bone marrow. Introduction of the proteasome-inhibitor bortezomib has improved MM prognosis and survival; however hypoxia-induced or acquired bortezomib resistance remains a clinical problem. This study highlighted the role of thioredoxin reductase 1 (TrxR1) in the hypoxia-induced and acquired bortezomib resistance in MM. Higher TrxR1 gene expression correlated with high-risk disease, adverse overall survival, and poor prognosis in myeloma patients. We demonstrated that hypoxia induced bortezomib resistance in myeloma cells and increased TrxR1 protein levels. Inhibition of TrxR1 using auranofin overcame hypoxia-induced bortezomib resistance and restored the sensitivity of hypoxic-myeloma cells to bortezomib. Hypoxia increased NF-кβ subunit p65 nuclear protein levels and TrxR1 inhibition decreased hypoxia-induced NF-кβ p65 protein levels in the nucleus and reduced the expression of NF-кβ-regulated genes. In addition, higher TrxR1 protein levels were observed in bortezomib-resistant myeloma cells compared to the naïve cells, and its inhibition using either auranofin or TrxR1-specific siRNAs reversed bortezomib resistance. TrxR1 inhibition reduced p65 mRNA and protein expression in bortezomib-resistant myeloma cells, and also decreased the expression of NF-кβ-regulated anti-apoptotic and proliferative genes. Thus, TrxR1 inhibition overcomes both hypoxia-induced and acquired bortezomib resistance by inhibiting the NF-кβ signaling pathway. Our findings demonstrate that elevated TrxR1 levels correlate with the acquisition of bortezomib resistance in MM. We propose considering TrxR1-inhibiting drugs, such as auranofin, either for single agent or combination therapy to circumvent bortezomib-resistance and improve survival outcomes of MM patients.