Modulation of the ATPase and transport activities of broad-acting multidrug resistance factor ABCC10 (MRP7)

Cytotoxicity and reversal effect of sertraline, fluoxetine, and citalopram on MRP1- and MRP7-mediated MDR

Cancer is one of the leading causes of death worldwide, and the development of resistance to chemotherapy drugs is a major challenge in treating malignancies. In recent years, researchers have focused on understanding the mechanisms of multidrug resistance (MDR) in cancer cells and have identified the overexpression of ATP-binding cassette (ABC) transporters, including ABCC1/MRP1 and ABCC10/MRP7, as a key factor in the development of MDR. In this study, we aimed to investigate whether three drugs (sertraline, fluoxetine, and citalopram) from the selective serotonin reuptake inhibitor (SSRI) family, commonly used as antidepressants, could be repurposed as inhibitors of MRP1 and MRP7 transporters and reverse MDR in cancer cells. Using a combination of in silico predictions and in vitro validations, we analyzed the interaction of MRP1 and MRP7 with the drugs and evaluated their ability to hinder cell resistance. We used computational tools to identify and analyze the binding site of these three molecules and determine their binding energy. Subsequently, we conducted experimental assays to assess cell viability when treated with various standard chemotherapies, both with and without the presence of SSRI inhibitors. Our results show that all three SSRI drugs exhibited inhibitory/reversal effects in the presence of chemotherapies on both MRP1-overexpressed cells and MRP7-overexpressed cells, suggesting that these medications have the potential to be repurposed to target MDR in cancer cells. These findings may open the door to using FDA-approved medications in combination therapy protocols to treat highly resistant malignancies and improve the efficacy of chemotherapy treatment. Our research highlights the importance of investigating and repurposing existing drugs to overcome MDR in cancer treatment.

The worthy role of hepatic arterial infusion chemotherapy in combination with anti-programmed cell death protein 1 monoclonal antibody immunotherapy in advanced hepatocellular carcinoma

Systemic therapy remains the primary therapeutic approach for advanced hepatocellular carcinoma (HCC). Nonetheless, its efficacy in achieving control of intrahepatic lesions is constrained. Hepatic arterial infusion chemotherapy (HAIC) is a therapeutic approach that combines localized treatment with systemic antitumor effects, which aim is to effectively manage the progression of cancerous lesions within the liver, particularly in patients with portal vein tumor thrombosis (PVTT). Combining HAIC with anti-programmed cell death protein 1 (anti-PD-1) monoclonal antibody (mAb) immunotherapy is anticipated to emerge as a novel therapeutic approach aimed at augmenting the response inside the localized tumor site and achieving prolonged survival advantages. In order to assess the effectiveness, safety, and applicability of various therapeutic modalities and to address potential molecular mechanisms underlying the efficacy of HAIC-sensitizing immunotherapy, we reviewed the literature about the combination of HAIC with anti-PD-1 mAb therapies.

Pharmacological Activity of Cepharanthine

Cepharanthine, a natural bisbenzylisoquinoline (BBIQ) alkaloid isolated from the plant Stephania Cephalantha Hayata, is the only bisbenzylisoquinoline alkaloid approved for human use and has been used in the clinic for more than 70 years. Cepharanthine has a variety of medicinal properties, including signaling pathway inhibitory activities, immunomodulatory activities, and antiviral activities. Recently, cepharanthine has been confirmed to greatly inhibit SARS-CoV-2 infection. Therefore, we aimed to describe the pharmacological properties and mechanisms of cepharanthine, mainly including antitumor, anti-inflammatory, anti-pathogen activities, inhibition of bone resorption, treatment of alopecia, treatment of snake bite, and other activities. At the same time, we analyzed and summarized the potential antiviral mechanism of cepharanthine and concluded that one of the most important anti-viral mechanisms of cepharanthine may be the stability of plasma membrane fluidity. Additionally, we explained its safety and bioavailability, which provides evidence for cepharanthine as a potential drug for the treatment of a variety of diseases. Finally, we further discuss the potential new clinical applications of cepharanthine and provide direction for its future development.

Efficacy and safety of HAIC alone vs. HAIC combined with lenvatinib for treatment of advanced hepatocellular carcinoma

To investigate efficacy and safety of hepatic arterial infusion chemotherapy combined with lenvatinib (HAIC-Len) and HAIC alone for the treatment of advanced hepatocellular carcinoma (Ad-HCC). Totally 349 patients with Ad-HCC participated in the research from February 2018 to October 2020. On the basis of propensity score matching (PSM), 132 and 110 cases were assigned to the HAIC group and the HAIC-Len group, respectively, with a ratio of 1:1. Progression-free survival (PFS), overall survival (OS), and complications were compared between two groups. The Kaplan-Meier method and log-rank test were utilized to estimate cumulative OS and PFS. Additionally, uni- and multi-variate Cox regression models were employed to identify significant independent factors. The median follow-up period in this study was set to be 20.8 months. Following PSM, the one-, two- and three-year cumulative OS rates in the HAIC-Len and HAIC groups were 63.6%, 12.1%, and 3.0%, and 47.2%, 11.8%, and 2.7%, respectively, with a significant difference (P < 0.001). The first-three-year cumulative incidence rates PFS in the HAIC-Len and the HAIC groups were 15.2%, 1.5%, and ND, and 11.8%, 4.5%, and 3.6%, respectively, with no significant difference detected (P = 0.092). BMI (HR 0.709. 95% CI 0.549, 0.915. P = 0.008) and AST (HR 1.005. 95% CI 1.003, 1.007. P < 0.001) represented independent prognostic factors for OS. Additionally, the two groups exhibited no significant difference in the incidence rates of adverse events. HAIC-Len significantly improved survival outcomes of patients with Ad-HCC and demonstrated acceptable toxicity compared to HAIC alone.

Differential Regulation of Glucosylceramide Synthesis and Efflux by Golgi and Plasma Membrane Bound ABCC10

Glucosylceramide (GlcCer) synthesis by the enzyme glucosylceramide synthase (GCS) occurs on the cytosolic leaflet of the Golgi and is the first important step for the synthesis of complex glycosphingolipids (GSLs) that takes place inside the lumen. Apart from serving as a precursor for glycosylation, newly synthesized GlcCer is also transported to the plasma membrane and secreted onto HDL in the circulation. The mechanism by which GlcCer is transported to HDL remains unclear. Recently, we showed that ATP-binding cassette transporter protein C10 (ABCC10) plays an important role in the synthesis and efflux of GlcCer in Huh-7 cells. In this study, we found that treatment of Huh-7 cells with an ABCC10 inhibitor, sorafenib, decreased the synthesis and efflux of GlcCer. However, treatment of cells with cepharanthine reduced only the efflux, but not synthesis, of GlcCer. These results indicate that ABCC10 may regulate the synthesis and efflux of GlcCer differentially in liver cells.

Sorafenib plus hepatic arterial infusion chemotherapy versus sorafenib alone for advanced hepatocellular carcinoma: A systematic review and meta-analysis

BACKGROUND

The combination of sorafenib and hepatic arterial infusion chemotherapy (HAIC) is expected to exert a synergistic anticancer effect. We conducted this systematic review to examine the efficacy and safety of sorafenib plus HAIC vs sorafenib alone for advanced hepatocellular carcinoma (HCC).

METHODS

We systematically searched the PubMed, Embase, and Cochrane Library with the following search terms: "sorafenib," "hepatic arterial infusion chemotherapy," "HAIC," "advanced," "hepatocellular carcinoma," and "HCC." Pooled hazard ratios (HRs) and 95% CIs were calculated for overall survival (OS) and progression-free survival (PFS), and we calculated the pooled risk ratios (RRs) and 95% CIs for objective response rate (ORR) and adverse events (AEs).

RESULTS

We found that sorafenib plus HAIC was associated with significantly better OS (HR, 0.56; 95% CI, 0.37-0.83; P < 0.01), PFS (HR, 0.44; 95% CI, 0.27-0.72; P < 0.01), and ORR (RR, 3.77; 95% CI, 1.87-7.58; P < 0.01) than sorafenib alone in advanced HCC. Grade 3/4 AEs were more frequent in the sorafenib plus HAIC group, including leukopenia (RR, 4.54; 95% CI, 1.77-11.64; P < 0.01), neutropenia (RR, 7.81; 95% CI, 3.36-18.16; P < 0.01), thrombocytopenia (RR, 2.97; 95% CI, 1.98-4.46; P < 0.01), anemia (RR, 2.24; 95% CI, 1.22-4.09; P < 0.01), anorexia (RR, 2.37; 95% CI, 1.07-5.27; P = 0.03), nausea (RR, 2.98; 95% CI, 1.19-7.42; P = 0.02), and vomiting (RR, 3.99; 95% CI, 1.14-14.01; P = 0.03).

CONCLUSION

Sorafenib plus HAIC improved OS, PFS, and ORR compared with sorafenib alone in advanced HCC, with acceptable safety profile.

ATP-Binding Cassette Transporter Family C Protein 10 Participates in the Synthesis and Efflux of Hexosylceramides in Liver Cells

In addition to sphingomyelin and ceramide, sugar derivatives of ceramides, hexosylceramides (HexCer) are the major circulating sphingolipids. We have shown that silencing of ABCA1 transmembrane protein function for instance in cases of loss of function of ABCA1 gene results in low levels of HDL as well as a concomitant reduction in plasma HexCer levels. However, proteins involved in hepatic synthesis and egress of HexCer from cells is not well known although ABCA1 seems to be indirectly controlling the HexCer plasma levels by supporting HDL synthesis. In this study, we hypothesized that protein(s) other than ABCA1 are involved in the transport of HexCer to HDL. Using an unbiased knockdown approach, we found that ATP-binding cassette transporter protein C10 (ABCC10) participates in the synthesis of HexCer and thereby affects egress to HDL in human hepatoma Huh-7 cells. Furthermore, livers from ABCC10 deficient mice had significantly lower levels of HexCer compared to wild type livers. These studies suggest that ABCC10 partakes in modulating the synthesis and subsequent efflux of HexCer to HDL in liver cells.

The Role of Uptake and Efflux Transporters in the Disposition of Glucuronide and Sulfate Conjugates

Glucuronidation and sulfation are the most typical phase II metabolic reactions of drugs. The resulting glucuronide and sulfate conjugates are generally considered inactive and safe. They may, however, be the most prominent drug-related material in the circulation and excreta of humans. The glucuronide and sulfate metabolites of drugs typically have limited cell membrane permeability and subsequently, their distribution and excretion from the human body requires transport proteins. Uptake transporters, such as organic anion transporters (OATs and OATPs), mediate the uptake of conjugates into the liver and kidney, while efflux transporters, such as multidrug resistance proteins (MRPs) and breast cancer resistance protein (BCRP), mediate expulsion of conjugates into bile, urine and the intestinal lumen. Understanding the active transport of conjugated drug metabolites is important for predicting the fate of a drug in the body and its safety and efficacy. The aim of this review is to compile the understanding of transporter-mediated disposition of phase II conjugates. We review the literature on hepatic, intestinal and renal uptake transporters participating in the transport of glucuronide and sulfate metabolites of drugs, other xenobiotics and endobiotics. In addition, we provide an update on the involvement of efflux transporters in the disposition of glucuronide and sulfate metabolites. Finally, we discuss the interplay between uptake and efflux transport in the intestine, liver and kidneys as well as the role of transporters in glucuronide and sulfate conjugate toxicity, drug interactions, pharmacogenetics and species differences.

Efficacy and safety of sorafenib plus hepatic arterial infusion chemotherapy for advanced hepatocellular carcinoma

BACKGROUND

Sorafenib is the standard treatment for patients with advanced HCC with improvement in survival and radiologic progression of the disease. Recently, few studies have advocated the Sorafenib + HAIC combination therapy results in better overall survival and progression-free survival than Sorafenib monotherapy in patients with advanced HCC. Herein, we aim to identify the best possible treatment option among the above two lines of therapy for patients with advanced HCC.

METHODS

The fixed effects and a random-effects model were used to perform a meta-analysis for overall response rate overall survival, and adverse events. Subgroup analysis of the data of univariate analysis in each included trial was performed to identify the specific patient population who could be benefitted from the combination therapy.

RESULTS

Four RCTs containing 609 patients were included in the final analysis. The overall response rate (OR: 3.81; 95% CI 1.01 to 14.42; P = 0.05) and overall survival (HR: 0.70; 95% CI 0.40 to 1.24; P > 0.05) were comparable. Subgroup analysis of OS showed that patients with Child-Pugh score B (HR: 0.30; 95% CI 0.13 to 0.72; P < 0.05) and AFP <400 ng/ml (HR: 0.72; 95% CI 0.52 to 0.99; P < 0.05) were associated with significantly improved survival in the Sorafenib + HAIC group. Bone marrow suppression (OR: 3.76; 95% CI 2.58 to 5.48; P < 0.001) was significantly higher in the Sorafenib + HAIC group, but hepatic function impairment, constitutional symptoms, gastrointestinal events, and dermatological events were comparable (p > 0.05).

CONCLUSIONS

Patients with Child-Pugh score B and AFP <400 ng/ml may be benefited most from Sorafenib + HAIC combination therapy.

Drug resistance: from bacteria to cancer

The phenomenon of drug resistance has been a hindrance to therapeutic medicine since the late 1940s. There is a plethora of factors and mechanisms contributing to progression of drug resistance. From prokaryotes to complex cancers, drug resistance is a prevailing issue in clinical medicine. Although there are numerous factors causing and influencing the phenomenon of drug resistance, cellular transporters contribute to a noticeable majority. Efflux transporters form a huge family of proteins and are found in a vast number of species spanning from prokaryotes to complex organisms such as humans. During the last couple of decades, various approaches in analyses of biochemistry and pharmacology of transporters have led us to understand much more about drug resistance. In this review, we have discussed the structure, function, potential causes, and mechanisms of multidrug resistance in bacteria as well as cancers.

Inhibitors of Chemoresistance Pathways in Combination with Ara-C to Overcome Multidrug Resistance in AML. A Mini Review

Acute myeloid leukemia (AML), the most common type of leukemia in older adults, is a heterogeneous disease that originates from the clonal expansion of undifferentiated hematopoietic progenitor cells. These cells present a remarkable variety of genes and proteins with altered expression and function. Despite significant advances in understanding the molecular panorama of AML and the development of therapies that target mutations, survival has not improved significantly, and the therapy standard is still based on highly toxic chemotherapy, which includes cytarabine (Ara-C) and allogeneic hematopoietic cell transplantation. Approximately 60% of AML patients respond favorably to these treatments and go into complete remission; however, most eventually relapse, develop refractory disease or chemoresistance, and do not survive for more than five years. Therefore, drug resistance that initially occurs in leukemic cells (primary resistance) or that develops during or after treatment (acquired resistance) has become the main obstacle to AML treatment. In this work, the main molecules responsible for generating chemoresistance to Ara-C in AML are discussed, as well as some of the newer strategies to overcome it, such as the inclusion of molecules that can induce synergistic cytotoxicity with Ara-C (MNKI-8e, emodin, metformin and niclosamide), subtoxic concentrations of chemotherapy (PD0332991), and potently antineoplastic treatments that do not damage nonmalignant cells (heteronemin or hydroxyurea + azidothymidine).

Cost-Effectiveness Analysis of Hepatic Arterial Infusion of FOLFOX Combined Sorafenib for Advanced Hepatocellular Carcinoma With Portal Vein Invasion

Background

Hepatic arterial infusion (HAI) of oxaliplatin, leucovorin, and fluorouracil (FOLFOX) plus sorafenib has a more desirable effect versus sorafenib for hepatocellular carcinoma (HCC) patients with portal vein invasion. However, considering the high cost of hepatic arterial infusion of chemotherapy (HAIC), this study evaluated the cost-effectiveness of HAIC plus sorafenib (SoraHAIC) versus standard care for HCC patients from the Chinese health system perspective.

Methods

A Markov multi-state model was constructed to simulate the disease course and source consumption of SoraHAIC. Costs of primary therapeutic drugs were calculated based on the national bid price, and hepatic artery catheterization fee was collected from the Fujian Provincial Price Bureau. Clinical data, other costs, and utility values were extracted from references. Primary outcomes included life-years (LYs), quality-adjusted life years (QALYs) and incremental cost-effectiveness ratio (ICER). The robustness of model was verified by uncertainty sensitivity analyses.

Results

SoraHAIC gained 1.18 QALYs (1.68 LYs) at a cost of $65,254, while the effectiveness and cost of sorafenib were 0.52 QALYs (0.79 LYs) and $14,280, respectively. The ICER of SoraHAIC vs sorafenib was $77,132/QALY ($57,153/LY). Parameter that most influenced the ICER was utility of PFS state. The probabilistic sensitivity analysis (PSA) showed that SoraHAIC was not cost-effective in the WTP threshold of 3*Gross Domestic Product (GDP) per capita of China ($30,492/QALY). But about 38.8% of the simulations were favorable to SoraHAIC at the WTP threshold of 3*GDP per capita of Beijing ($72,000/QALY). When 3*GDP per capita of Fujian ($47,285/QALY) and Gansu Province ($14,595/QALY) were used as WTP threshold, the acceptability of SoraHAIC was 0.3% and 0%, respectively.

Conclusions

The study results indicated that SoraHAIC was not cost-effective in medium-, and low-income regions of China. In developed areas of China (Beijing), there was a 38.8% probability that the SoraHAIC regimen would be cost-effective.

Sorafenib combined with embolization plus hepatic arterial infusion chemotherapy for inoperable hepatocellular carcinoma

BACKGROUND

There is little evidence of combining sorafenib with hepatic arterial infusion chemotherapy (HAIC) after transarterial chemoembolization (TACE) for intermediate and advanced hepatocellular carcinoma (HCC). It is important to identify that patients with intermediate and advanced HCC are most likely to benefit from this combination therapy.

AIM

To investigate the safety and clinical outcomes of sorafenib combined with HAIC with folinic acid, 5-fluorouracil (5-FU), and oxaliplatin (FOLFOX) after TACE for intermediate and advanced HCC.

METHODS

This prospective phase II study enrolled patients with intermediate and advanced HCC who underwent treatment with sorafenib combined with TACE-HAIC. All patients initially received the standard 400 mg dose of sorafenib twice daily before TACE-HAIC. Participants at our institute with intermediate and advanced HCC underwent routine TACE. Then, the catheter used for embolization was kept in place in the hepatic artery, and oxaliplatin was intra-arterially administered for 6 h, followed by 5-FU for 18 h, and folinic acid was intravenously administered for 2 h. The primary endpoints were safety, as evaluated by the Common Terminology and Criteria for Adverse Events version 4.0, and 12-mo progression-free survival (PFS), as analyzed by the Kaplan-Meier method. As secondary endpoints, the objective response rate (ORR) was evaluated by the modified Response Evaluation Criteria for Solid Tumors, and survival time [overall survival (OS)] was analyzed by the Kaplan-Meier method.

RESULTS

Sixty-six participants at our institute with intermediate and advanced HCC were enrolled in this prospective study (mean age, 53.3 ± 11.7 years). Approximately 56.1% of participants had Barcelona Clinic Liver Cancer (BCLC) stage C disease, and 43.9% had BCLC stage B disease. The ORR was 42.4%. The disease control rate was 87.9%. The grade 3-4 toxicities consisted of thrombocytopenia (4.5%), neutropenia (3.0%), and elevated aspartate aminotransferase (12.2%). Hand-foot skin reaction was also observed (40.9%). The median PFS was 13.1 mo (13.5 mo in the BCLC stage B participants and 9.4 mo in the BCLC stage C participants). The 6-mo, 12-mo, and 24-mo PFS rates were 75.0%, 54.7%, and 30.0%, respectively. The median OS was 21.8 mo.

CONCLUSION

Sorafenib combined with HAIC (FOLFOX) after TACE may be a feasible treatment choice for intermediate and advanced HCC because this treatment met the prespecified endpoint of a 6-mo PFS rate exceeding 50% and had good patient tolerance. Prospective randomized controlled trials are needed to confirm the effect of this combination therapy.

Cepharanthine hydrochloride induces mitophagy targeting GPR30 in hepatocellular carcinoma (HCC)

Objectives: Cepharanthine exhibits a wide range of therapeutic effects against numerous cancers by virtue of its pleiotropic mechanisms. However, cepharanthine monotherapy has insufficient drug efficacy for cancers in animal models and clinical trials. The mechanism of its limited efficacy is unknown.Methods: We investigated the possible mechanism for the limited drug efficacy of cepharanthine in cancer therapy using both hepatocellular carcinoma (HCC) primary cells and cell lines, in vitro and in mouse xenograft models.Results: We found that cepharanthine hydrochloride (CH), a semi-synthetic derivative of cepharanthine, induced mitophagy independent of mTOR signaling, and played an AMPK-dependent protective role in the cell fate of HCC in vitro and in vivo. Mechanistically, we demonstrated that CH may bind to GPR30 receptor to activate the subsequent signal cascade involving mitochondrial fission, thus facilitating mitophagy. Therefore, we proposed a new therapeutic regimen for HCC involving CH combined with an autophagy inhibitor. This regimen exhibited remarkable anti-cancer effects in HCC xenograft mouse model.Conclusion: These results identify CH as a new mitophagy inducer targeting GPR30 receptor. The combination therapy of CH and an autophagy inhibitor may become a novel strategy for enhancing the anti-tumor potential of cepharanthine in HCC.

Sorafenib Plus Hepatic Arterial Infusion of Oxaliplatin, Fluorouracil, and Leucovorin vs Sorafenib Alone for Hepatocellular Carcinoma With Portal Vein Invasion: A Randomized Clinical Trial

Importance

Sorafenib is the first-line treatment for hepatocellular carcinoma with portal vein invasion; however, it has shown unsatisfactory survival benefit. Sorafenib plus hepatic arterial infusion chemotherapy (HAIC) of oxaliplatin, fluorouracil, and leucovorin (FOLFOX) has shown promising results for these patients in a previous phase 2 study.

Objective

To investigate the efficacy and safety of sorafenib plus HAIC compared with sorafenib for hepatocellular carcinoma with portal vein invasion.

Design, Setting, and Participants

This randomized, open-label clinical trial enrolled 818 screened patients. Of the 818 participants, 247 with hepatocellular carcinoma and portal vein invasion were randomly assigned (1:1) via a computer-generated sequence to receive sorafenib plus HAIC or sorafenib. This trial was conducted at 5 hospitals in China and enrolled patients from April 1, 2016, to October 10, 2017, with a follow-up period of 10 months.

Interventions

Randomization to receive 400 mg sorafenib twice daily (sorafenib group) or 400 mg sorafenib twice daily plus HAIC (SoraHAIC group) (oxaliplatin 85 mg/m2, leucovorin 400 mg/m2, fluorouracil bolus 400 mg/m2 on day 1, and fluorouracil infusion 2400 mg/m2 for 46 hours, every 3 weeks).

Main Outcomes and Measures

The primary endpoint was overall survival by intention-to-treat analysis. Safety was assessed in patients who received at least 1 dose of study treatment.

Results

For 247 patients (median age, 49 years; range, 18-75 years; 223 men and 24 women), median overall survival was 13.37 months (95% CI, 10.27-16.46) in the SoraHAIC group vs 7.13 months (95% CI, 6.28-7.98) in the sorafenib group (hazard ratio [HR], 0.35; 95% CI, 0.26-0.48; P < .001). The SoraHAIC group showed a higher response rate than the sorafenib group (51 [40.8%] vs 3 [2.46%]; P < .001), and a longer median progression-free survival (7.03 [95% CI, 6.05-8.02] vs 2.6 [95% CI, 2.15-3.05] months; P < .001). Grade 3/4 adverse events that were more frequent in the SoraHAIC group than in the sorafenib group included neutropenia (12 [9.68%] vs 3 [2.48%]), thrombocytopenia (16 [12.9%] vs 6 [4.96%]), and vomiting (8 [6.45%] vs 1 [0.83%]).

Conclusions and Relevance

Sorafenib plus HAIC of FOLFOX improved overall survival and had acceptable toxic effects compared with sorafenib in patients with hepatocellular carcinoma and portal vein invasion.

Trial Registration

ClinicalTrials.gov identifier: NCT02774187.

Circadian clock-controlled drug metabolism and transport

Metabolism and transport of many drugs oscillate with times of the day (solar time), resulting in circadian time-dependent drug exposure and pharmacokinetics.Time-dependent pharmacokinetics (also known as chronopharmacokinetics) is associated with time-varying drug effects and toxicity.This review summarizes drug-metabolizing enzymes and transporters with rhythmic expressions in the liver, intestine and/or kidney. Correlations of these diurnal proteins with circadian variations in drug exposure and effects/toxicity are covered. We also discuss the molecular mechanisms for circadian control of enzymes and transporters.Mechanism-based chronopharmacokinetics would facilitate a better understanding of chronopharmacology and the design of time-specific drug delivery systems, ultimately leading to improved drug efficacy and minimized toxicity.

Cepharanthine: An update of its mode of action, pharmacological properties and medical applications

BACKGROUND

Cepharanthine (CEP) is a drug used in Japan since the 1950s to treat a number of acute and chronic diseases, including treatment of leukopenia, snake bites, xerostomia and alopecia. It is the only approved drug for Human use in the large class of bisbenzylisoquinoline alkaloids. This natural product, mainly isolated from the plant Stephania cephalantha Hayata, exhibits multiple pharmacological properties including anti-oxidative, anti-inflammatory, immuno-regulatory, anti-cancer, anti-viral and anti-parasitic properties.

PURPOSE

The mechanism of action of CEP is multifactorial. The drug exerts membrane effects (modulation of efflux pumps, membrane rigidification) as well as different intracellular and nuclear effects. CEP interferes with several metabolic axes, primarily with the AMP-activated protein kinase (AMPK) and NFκB signaling pathways. In particular, the anti-inflammatory effects of CEP rely on AMPK activation and NFκB inhibition.

CONCLUSION

In this review, the historical discovery and development of CEP are retraced, and the key mediators involved in its mode of action are presented. The past, present, and future of CEP are recapitulated. This review also suggests new opportunities to extend the clinical applications of this well-tolerated old Japanese drug.

Sorafenib plus hepatic arterial infusion chemotherapy with oxaliplatin versus sorafenib alone for advanced hepatocellular carcinoma

Objective

To compare the efficacy of sorafenib plus hepatic arterial infusion chemotherapy (HAIC) with oxaliplatin to that of sorafenib alone in patients with advanced hepatocellular carcinoma (HCC).

Methods

This was a retrospective, single-center trial. Between April 3, 2017 and July 2, 2018, 104 patients with Child-Pugh A and advanced HCC received either 400 mg of sorafenib orally twice daily plus HAIC with oxaliplatin (oxaliplatin 85 mg/m², every 3 weeks via repetitive catheterization) (n = 46, soraOXA group) or 400 mg of only sorafenib orally twice daily (n = 58, sorafenib group). Overall survival, progression-free survival, objective response rate, and treatment-related adverse events were compared.

Results

The median overall survival was 9.37 months (95% CI, 7.05–11.68) in the soraOXA group versus 4.8 months (95% CI, 2.98–6.62) in the sorafenib group (HR 0.46 [95% CI, 0.29–0.72]; P < 0.001). The soraOXA group also showed a higher objective response rate (16 [34.8%] vs 1 [1.7%]; P < 0.001) and a longer progression-free survival rate (5.5 months [95% CI, 2.32–8.68] vs 2.4 months [95% CI, 1.65–3.15], HR 0.54 [95% CI, 0.36–0.81], P = 0.003) than the sorafenib group. There was no significant difference in the overall incidence of any grade adverse events, grade 3/4 adverse events, serious adverse events, or incidence of treatment termination due to adverse events between the two groups.

Conclusion

Compared with sorafenib alone, sorafenib plus HAIC with oxaliplatin showed favorable treatment outcomes in patients with advanced HCC. The merits of this approach need to be established with a prospective trial.

The Circadian Clock Gene Bmal1 Controls Intestinal Exporter MRP2 and Drug Disposition

The intestinal exporter MRP2 plays an important role in disposition and elimination of a wide range of drugs. Here, we aimed to clarify the impact of circadian clock on intestinal MRP2, and to determine the molecular mechanisms for generation of diurnal MRP2 expression. Methods: The regulatory effects of Bmal1 on intestinal MRP2 expression were assessed using intestine-specific Bmal1 knockout (Bmal1iKO ) mice and colon cancer cells. The relative mRNA and protein levels were determined by qPCR and Western blotting, respectively. Everted gut sac, cell viability and in situ intestinal perfusion experiments were performed to evaluate intestinal efflux of the MRP2 substrate methotrexate (MTX). Toxicity and pharmacokinetic experiments were performed with Bmal1iKO mice and control littermates (Bmal1fl/fl mice) after oral gavage of MTX. Transcriptional gene regulation was investigated using luciferase reporter, mobility shift and chromatin immunoprecipitation (ChIP) assays. Results: Bmal1iKO mice were generated by inter-crossing the mice carrying a Bmal1 exon 8 floxed allele (Bmal1fl/fl ) with Villin-Cre mice. Intestinal MRP2 expression exhibited a diurnal oscillation in Bmal1fl/fl mice with a zenith value at ZT6. Bmal1 ablation caused reductions in Mrp2 mRNA and protein levels [as well as in transport activity (measured by MTX)], and blunted their diurnal rhythms. Intestinal ablation of Bmal1 abrogated circadian time-dependency of MTX pharmacokinetics and toxicity. Bmal1/BMAL1 regulation of rhythmic Mrp2/MRP2 expression was also confirmed in the colon cancer CT26 and Caco-2 cells. Based on a combination of luciferase reporter, mobility shift and ChIP assays, we found that Dbp activated and E4bp4 repressed Mrp2 transcription via specific binding to a same D-box (-100/-89 bp) element in promoter region. Further, Bmal1 directly activated the transcription of Dbp and Rev-erbα through the E-boxes, whereas it negatively regulated E4bp4 via the transcriptional repressor Rev-erbα. Positive regulation of Mrp2 by Rev-erbα was also observed, and attained through modulation of E4bp4. Conclusion: Bmal1 coordinates temporal expressions of DBP (a MRP2 activator), REV-ERBα (an E4BP4 repressor) and E4BP4 (a MRP2 repressor), generating diurnal MRP2 expression.

The Syk inhibitor R406 is a modulator of P-glycoprotein (ABCB1)-mediated multidrug resistance

In a previously published study, higher levels of spleen tyrosine kinase (Syk) were observed in recurrent post-chemotherapy ovarian cancers compared to primary tumors. Syk inhibition was found to stabilize microtubules and potentiate paclitaxel activity in cellular models of taxane-resistant ovarian cancers. We further studied the effects of Syk inhibition on paclitaxel activity in Syk(+) ovarian cancer cell models and in variants selected for taxane resistance. Syk inhibition was accomplished using RNAi and by exposure to the small molecule competitive inhibitor R406, the active metabolite of fostamatinib. Exposure to R406 or to a SYK-specific pool of siRNAs did not alter taxane activity in the OVCAR-3 cell line, which has the most Syk content in our panel of nine human ovarian cancer cell lines. However, treatment with R406 sensitised the multidrug resistant (MDR) variants MES-SA/Dx5 and SK-OV-3/TR to paclitaxel in a dose-dependent manner resulting from the inhibition of the ABCB1/P-glycoprotein (P-gp) drug transporter. These observations are Syk-independent since both MDR cell models are Syk negative. R406 modulated resistance to other known P-gp substrates, and we observed orthovanadate-sensitive ATPase stimulation resulting from treatment with R406. These data indicate that the chemo-sensitizing effect of R406 in taxane-resistant cells previously reported was not associated with Syk but resulted from the modulation of P-gp-mediated MDR.

Phase II Study of Sorafenib Combined with Concurrent Hepatic Arterial Infusion of Oxaliplatin, 5-Fluorouracil and Leucovorin for Unresectable Hepatocellular Carcinoma with Major Portal Vein Thrombosis

BACKGROUND

Sorafenib is recommended for the first-line treatment of advanced hepatocellular carcinoma (HCC). However, the median progression-free survival (PFS) of patients with HCC and major portal vein tumor thrombosis treated with sorafenib monotherapy is no more than 3 months. A prospective single-arm phase II study was conducted to determine whether adding hepatic arterial infusion chemotherapy of oxaliplatin, 5-fluorouracil and leucovorin to sorafenib could improve on these results.

METHODS

Thirty five patients were treated with sorafenib 400 mg orally twice a day, oxaliplatin 85 mg/m² HAI on day 1, leucovorin 400 mg/m² HAI on days 1, and 5-fluorouracil 2800 mg/m² on days 1 and 2, repeated every 21 days. The primary end point was the 3-month PFS rate.

RESULTS

The 3-, 6-, and 12-month PFS rates were 82.9, 51.4, and 22.9%, respectively. The median PFS and overall survival was 6.7 and 13.2 months, respectively. The objective response rate was 40%, and the disease control rate was 77.1% by RECIST criteria. Five (14.3%) patients achieved conversion to complete resection after the study treatment, and one of them experienced a pathological complete response. Treatment-related deaths did not occur. Grade 3-4 toxicities consisted of increases in aspartate aminotransferase (31.4%), hand-foot syndrome (17.1%), thrombocytopenia (14.3%), and neutropenia (8.6%).

CONCLUSIONS

The combination treatment met the pre-specified end point of a 3-month progression free survival rate exceeding 65% and was clinical tolerable. The merits of this approach need to be established with a phase III trial. Clinical trial number http://ClinicalTrials.gov (No. NCT02981498).

HES1 Promotes Colorectal Cancer Cell Resistance To 5-Fu by Inducing Of EMT and ABC Transporter Proteins

Background and Aim: Hairy enhancer of split-1 (HES1) is a downstream transcriptional factor of Notch signaling pathway, which was found to be related to chemoresistance. This study was aimed to investigate the role of HES1 in chemoresistance of colorectal cancer (CRC). Methods: Tissue microarray was used to analyze the clinical significance of HES1 in radical resected (R0) stage II/III CRC patients that received adjuvant chemotherapy. 5-fluorouracil (5-Fu) chemoresistance was examined in CRC cell lines (RKO and HCT8, LOVO) with stable over-expression and inhibition of HES1 gene by cytotoxicity test. Gene expression microarray was used to investigate the enriched pathways and different expressed of genes in cells with over-expressed HES1. Expression changes of the chemoresistance related genes were confirmed by qPCR and western blot analysis. Results: Stage II CRC patients with higher HES1 expression showed higher recurrence rate after chemotherapy. Colon cancer cell lines which over-expressed HES1 were more resistant to 5-Fu treatment in vitro. Gene expression microarray revealed that HES1 was related to the signaling pathways of epithelial-mesenchymal transition (EMT) and drug metabolism. Immunofluorescence assay showed HES1 over-expression lead to depressed E-cadherin and elevated N-cadherin. QPCR and western blot analysis confirmed that ABCC1, ABCC2 and P-gp1 were induced after HES1 over-expression. Conclusions: HES1 promotes chemoresistance to 5-Fu by prompting EMT and inducing of several ABC transporter genes. HES1 might be a novel therapeutic target in CRC treatment.

Overcoming ABC transporter-mediated multidrug resistance: The dual role of tyrosine kinase inhibitors as multitargeting agents

Resistance to conventional and target specific antitumor drugs still remains one of the major cause of treatment failure and patience death. This condition often involves ATP-binding cassette (ABC) transporters that, by pumping the drugs outside from cancer cells, attenuate the potency of chemotherapeutics and negatively impact on the fate of anticancer therapy. In recent years, several tyrosine kinase inhibitors (TKIs) (e.g., imatinib, nilotinib, dasatinib, ponatinib, gefitinib, erlotinib, lapatinib, vandetanib, sunitinib, sorafenib) have been reported to interact with ABC transporters (e.g., ABCB1, ABCC1, ABCG2, ABCC10). This finding disclosed a very complex scenario in which TKIs may behave as substrates or inhibitors depending on the expression of specific pumps, drug concentration, affinity for transporters and types of co-administered agents. In this context, in-depth investigation on TKI chemosensitizing functions might provide a strong rationale for combining TKIs and conventional therapeutics in specific malignancies. The reposition of TKIs as antagonists of ABC transporters opens a new way towards anticancer therapy and clinical strategies aimed at counteracting drug resistance. This review will focus on some paradigmatic examples of the complex and not yet fully elucidated interaction between clinical available TKIs (e.g. BCR-ABL, EGFR, VEGFR inhibitors) with the main ABC transporters implicated in multidrug resistance.

New Potential Pharmacological Functions of Chinese Herbal Medicines via Regulation of Autophagy

Autophagy is a universal catabolic cellular process for quality control of cytoplasm and maintenance of cellular homeostasis upon nutrient deprivation and environmental stimulus. It involves the lysosomal degradation of cellular components such as misfolded proteins or damaged organelles. Defects in autophagy are implicated in the pathogenesis of diseases including cancers, myopathy, neurodegenerations, infections and cardiovascular diseases. In the recent decade, traditional drugs with new clinical applications are not only commonly found in Western medicines, but also highlighted in Chinese herbal medicines (CHM). For instance, pharmacological studies have revealed that active components or fractions from Chaihu (Radix bupleuri), Hu Zhang (Rhizoma polygoni cuspidati), Donglingcao (Rabdosia rubesens), Hou po (Cortex magnoliae officinalis) and Chuan xiong (Rhizoma chuanxiong) modulate cancers, neurodegeneration and cardiovascular disease via autophagy. These findings shed light on the potential new applications and formulation of CHM decoctions via regulation of autophagy. This article reviews the roles of autophagy in the pharmacological actions of CHM and discusses their new potential clinical applications in various human diseases.

ABCC4 Is a Determinant of Cytarabine-Induced Cytotoxicity and Myelosuppression

Resistance to cytarabine remains a major challenge in the treatment of acute myeloid leukemia (AML). Based on previous studies implicating ABCC4/MRP4 in the transport of nucleosides, we hypothesized that cytarabine is sensitive to ABCC4‐mediated efflux, thereby decreasing its cytotoxic response against AML blasts. The uptake of cytarabine and its monophosphate metabolite was found to be facilitated in ABCC4‐expressing vesicles and intracellular retention was significantly impaired by overexpression of human ABCC4 or mouse Abcc4 (P < 0.05). ABCC4 was expressed highly in AML primary blasts and cell lines, and cytotoxicity of cytarabine in cells was increased in the presence of the ABCC4 inhibitors MK571 or sorafenib, as well as after ABCC4 siRNA. In Abcc4‐null mice, cytarabine‐induced hematological toxicity was enhanced and ex vivo colony‐forming assays showed that Abcc4‐deficiency sensitized myeloid progenitors to cytarabine. Collectively, these studies demonstrate that ABCC4 plays a protective role against cytarabine‐mediated insults in leukemic and host myeloid cells.

Antiandrogens Inhibit ABCB1 Efflux and ATPase Activity and Reverse Docetaxel Resistance in Advanced Prostate Cancer

PURPOSE

Previous studies show that inhibition of ABCB1 expression overcomes acquired docetaxel resistance in C4-2B-TaxR cells. In this study, we examined whether antiandrogens, such as bicalutamide and enzalutamide, could inhibit ABCB1 activity and overcome resistance to docetaxel.

EXPERIMENTAL DESIGN

ABCB1 efflux activity was determined using a rhodamine efflux assay. ABCB1 ATPase activity was determined by Pgp-Glo assay systems. The effects of the antiandrogens bicalutamide and enzalutamide on docetaxel sensitivity were determined by cell growth assays and tumor growth in vivo.

RESULTS

We found that bicalutamide and enzalutamide inhibit ABCB1 ATP-binding cassette transporter activity through blocking ABCB1 efflux activity. Bicalutamide inhibited ABCB1 efflux activity by 40%, whereas enzalutamide inhibited ABCB1 efflux activity by approximately 60%. Both bicalutamide and enzalutamide inhibit ABCB1 ATPase activity. In addition, bicalutamide and enzalutamide inhibit ABCB1 efflux activity and desensitize docetaxel-resistant and androgen receptor (AR)-negative DU145 cells. Combination of bicalutamide with docetaxel had a significant antitumor effect in both AR-positive and AR-negative docetaxel-resistant xenograft models, suggesting that bicalutamide desensitizes docetaxel-resistant cells to docetaxel treatment independent of AR status.

CONCLUSIONS

We identified a novel mechanism of action for antiandrogens such as bicalutamide and enzalutamide as inhibitors of ABCB1 efflux and ATPase activity. Bicalutamide and enzalutamide desensitize docetaxel-resistant prostate cancer cells to docetaxel treatment independent of AR status. These studies may lead to the development of combinational therapies with bicalutamide/enzalutamide and docetaxel as effective regimens to treat advanced prostate cancer independent of AR status, and possibly other types of cancer.

The modulation of ABC transporter-mediated multidrug resistance in cancer: a review of the past decade

ATP-binding cassette (ABC) transporters represent one of the largest and oldest families of membrane proteins in all extant phyla from prokaryotes to humans, which couple the energy derived from ATP hydrolysis essentially to translocate, among various substrates, toxic compounds across the membrane. The fundamental functions of these multiple transporter proteins include: (1) conserved mechanisms related to nutrition and pathogenesis in bacteria, (2) spore formation in fungi, and (3) signal transduction, protein secretion and antigen presentation in eukaryotes. Moreover, one of the major causes of multidrug resistance (MDR) and chemotherapeutic failure in cancer therapy is believed to be the ABC transporter-mediated active efflux of a multitude of structurally and mechanistically distinct cytotoxic compounds across membranes. It has been postulated that ABC transporter inhibitors known as chemosensitizers may be used in combination with standard chemotherapeutic agents to enhance their therapeutic efficacy. The current paper reviews the advance in the past decade in this important domain of cancer chemoresistance and summarizes the development of new compounds and the re-evaluation of compounds originally designed for other targets as transport inhibitors of ATP-dependent drug efflux pumps.

Synthesis and biological evaluation of pentacyclic strychnos alkaloids as selective modulators of the ABCC10 (MRP7) efflux pump

The selective modulation of ATP-binding cassette (ABC) efflux pumps overexpressed in multidrug resistant cancers (MDR) and attendant resensitization to chemotherapeutic agents represent a promising strategy for treating cancer. We have synthesized four novel pentacyclic Strychnos alkaloids alstolucines B (2), F (3), and A (5) and N-demethylalstogucine (4), in addition to known Strychnos alkaloid echitamidine (16), and we evaluated compounds 1–5 in biochemical assays with ABCC10 and P-glycoprotein (P-gp). Alstolucines B (2) and F (3) inhibited ABCC10 ATPase activity at 12.5 μM without affecting P-gp function; moreover, they resensitized ABCC10-transfected cell lines to paclitaxel at 10 μM. Altogether, the alstolucines represent promising lead candidates in the development of modulators of ABCC10 for MDR cancers overexpressing this pump.

Mechanisms of resistance to cabazitaxel

We studied mechanisms of resistance to the novel taxane cabazitaxel in established cellular models of taxane resistance. We also developed cabazitaxel-resistant variants from MCF-7 breast cancer cells by stepwise selection in drug alone (MCF-7/CTAX) or drug plus the transport inhibitor PSC-833 (MCF-7/CTAX-P). Among multidrug-resistant (MDR) variants, cabazitaxel was relatively less cross-resistant than paclitaxel and docetaxel (15- vs. 200-fold in MES-SA/Dx5 and 9- vs. 60-fold in MCF-7/TxT50, respectively). MCF-7/TxTP50 cells that were negative for MDR but had 9-fold resistance to paclitaxel were also 9-fold resistant to cabazitaxel. Selection with cabazitaxel alone (MCF-7/CTAX) yielded 33-fold resistance to cabazitaxel, 52-fold resistance to paclitaxel, activation of ABCB1, and 3-fold residual resistance to cabazitaxel with MDR inhibition. The MCF-7/CTAX-P variant did not express ABCB1, nor did it efflux rhodamine-123, BODIPY-labeled paclitaxel, and [(3)H]-docetaxel. These cells are hypersensitive to depolymerizing agents (vinca alkaloids and colchicine), have reduced baseline levels of stabilized microtubules, and impaired tubulin polymerization in response to taxanes (cabazitaxel or docetaxel) relative to MCF-7 parental cells. Class III β-tubulin (TUBB3) RNA and protein were elevated in both MCF-7/CTAX and MCF-7/CTAX-P. Decreased BRCA1 and altered epithelial-mesenchymal transition (EMT) markers are also associated with cabazitaxel resistance in these MCF-7 variants, and may serve as predictive biomarkers for its activity in the clinical setting. In summary, cabazitaxel resistance mechanisms include MDR (although at a lower level than paclitaxel and docetaxel), and alterations in microtubule dynamicity, as manifested by higher expression of TUBB3, decreased BRCA1, and by the induction of EMT.

Deconstructing breast cancer cell biology and the mechanisms of multidrug resistance

Cancer complexity constantly challenges the way that clinicians manage breast cancer therapy. Tumor heterogeneity and intratumoral stroma characteristics allow cells with different phenotypes and deregulated apoptotic, proliferative and migration abilities to co-exist contributing to a disappointing therapeutic response. While new approaches are being associated with conventional chemotherapy, such as hormonal therapy or target monoclonal antibodies, recurrence and metastasization are still observed. Membrane transporters are the cell's first line of contact with anticancer drugs having a major role in multidrug resistance events. This structural-based activity enables the cell to be drug-resistant by decreasing drug intracellular concentration through an efflux-transport mechanism, mainly associated with overexpression of ATP-binding cassette (ABC) proteins. This review focuses on some of the important structural and biological properties of the malignant cell and tumor microenvironment, addressing the role of the membrane ABC transporters in therapeutic outcomes, and highlighting related molecular pathways that may represent meaningful target therapies.

Natural small-molecule enhancers of autophagy induce autophagic cell death in apoptosis-defective cells

Resistance of cancer cells to chemotherapy is a significant problem in oncology, and the development of sensitising agents or small-molecules with new mechanisms of action to kill these cells is needed. Autophagy is a cellular process responsible for the turnover of misfolded proteins or damaged organelles, and it also recycles nutrients to maintain energy levels for cell survival. In some apoptosis-resistant cancer cells, autophagy can also enhance the efficacy of anti-cancer drugs through autophagy-mediated mechanisms of cell death. Because the modulation of autophagic processes can be therapeutically useful to circumvent chemoresistance and enhance the effects of cancer treatment, the identification of novel autophagic enhancers for use in oncology is highly desirable. Many novel anti-cancer compounds have been isolated from natural products; therefore, we worked to discover natural, anti-cancer small-molecule enhancers of autophagy. Here, we have identified a group of natural alkaloid small-molecules that function as novel autophagic enhancers. These alkaloids, including liensinine, isoliensinine, dauricine and cepharanthine, stimulated AMPK-mTOR dependent induction of autophagy and autophagic cell death in a panel of apoptosis-resistant cells. Taken together, our work provides novel insights into the biological functions, mechanisms and potential therapeutic values of alkaloids for the induction of autophagy.

Abcc10 status affects mammary tumour growth, metastasis, and docetaxel treatment response

Background:

Resistance to chemotherapeutic agents is a major obstacle to cancer treatment. A group of ABC efflux pumps, the Multidrug Resistance Proteins, is a source of resistance. Herein, we investigated the role of ABCC10 in mammary tumours, given the important role we have defined for ABCC10 in transporting taxanes, and the recognition that some ABCC proteins have roles in tumour growth.

Methods:

ABCC10 expression was correlated to human breast cancer subtype using breast tissue microarrays. Real-time quantitative PCR and western blot analysis were used to examine ABCC10 expression in human breast cancer lines. Abcc10^−/− mice were crossed to MMTV-PyVmT mice to produce Abcc10^−/−vs Abcc10^+/+ mammary tumours and derivative cell lines. We used allograft and cellular assays to perform baseline and drug sensitization analysis of tumours and cell lines.

Results:

Clinical sample analyses indicated that ABCC10 was more highly expressed in Her2+ and ER+ than in Her2−, ER−, and triple-negative breast cancer. Unexpectedly, PyVmT; Abcc10^−/− tumours grew more rapidly than PyVmT; Abcc10^+/+ tumours and were associated with significantly reduced apoptosis and metastasis. PyVmT; Abcc10^−/− lines were less migratory than PyVmT; Abcc10^+/+ lines. Finally, we showed increased survival of docetaxel-treated MMTV-PyVmT; Abcc10^−/− mice compared with wild-type mice.

Conclusions:

These data identify roles for Abcc10 in breast cancer pathogenesis and in vivo docetaxel resistance.

Priming cancer cells for drug resistance: role of the fibroblast niche

Conventional and targeted chemotherapies remain integral strategies to treat solid tumors. Despite the large number of anti-cancer drugs available, chemotherapy does not completely eradicate disease. Disease recurrence and the growth of drug resistant tumors remain significant problems in anti-cancer treatment. To develop more effective treatment strategies, it is important to understand the underlying cellular and molecular mechanisms of drug resistance. It is generally accepted that cancer cells do not function alone, but evolve through interactions with the surrounding tumor microenvironment. As key cellular components of the tumor microenvironment, fibroblasts regulate the growth and progression of many solid tumors. Emerging studies demonstrate that fibroblasts secrete a multitude of factors that enable cancer cells to become drug resistant. This review will explore how fibroblast secretion of soluble factors act on cancer cells to enhance cancer cell survival and cancer stem cell renewal, contributing to the development of drug resistant cancer.

Ponatinib enhances anticancer drug sensitivity in MRP7-overexpressing cells

The presence of acquired multidrug resistance (MDR) is one of the primary impediments to the success of chemotherapy. MDR is often a result of overexpression of ATP-binding cassette (ABC) transporters, which are involved in the extrusion of therapeutic drugs. Recently, it was shown that several ABC transporters could be modulated by specific tyrosine-kinase inhibitors (TKIs). Ponatinib, a multi-targeted TKI, inhibits the activity of BCR-ABL with very high potency and broad specificity, including the T315I mutation which confers resistance to other TKIs. It was reported that ponatinib was capable of reversing breast cancer resistance protein (BCRP)- and P-glycoprotein (P-gp)-mediated MDR. In the present study, we report for the first time that ponatinib also potentiates the cytotoxicity of widely used therapeutic substrates of MRP7, such as paclitaxel, docetaxel, vincristine and vinblastine. Ponatinib significantly enhances the accumulation of [³H]-paclitaxel in cells expressing MRP7. Furthermore, accumulation of [³H]-paclitaxel was achieved by inhibition of MRP7-mediated transport. Ponatinb limited drug export via MRP7 by multiple mechanisms. In addition to inhibition of pump function, ponatinib also downregulated MRP7 protein expression in a time- and concentration-dependent manner. Thus, ponatinib may represent a potential reversal agent for the treatment of MDR and may be useful for combination therapy in MDR cancer patients in clinical practice.

Masitinib antagonizes ATP-binding cassette subfamily C member 10-mediated paclitaxel resistance: a preclinical study

Paclitaxel displays clinical activity against a wide variety of solid tumors. However, resistance to paclitaxel significantly attenuates the response to chemotherapy. The ABC transporter subfamily C member 10 (ABCC10), also known as multidrug resistance protein 7 (MRP7) efflux transporter, is a major mediator of paclitaxel resistance. In this study, we show that masitinib, a small molecule stem-cell growth factor receptor (c-Kit) tyrosine kinase inhibitor, at nontoxic concentrations, significantly attenuates paclitaxel resistance in HEK293 cells transfected with ABCC10. Our in vitro studies indicated that masitinib (2.5 μmol/L) enhanced the intracellular accumulation and decreased the efflux of paclitaxel by inhibiting the ABCC10 transport activity without altering the expression level of ABCC10 protein. Furthermore, masitinib, in combination with paclitaxel, significantly inhibited the growth of ABCC10-expressing tumors in nude athymic mice in vivo. Masitinib administration also resulted in a significant increase in the levels of paclitaxel in the plasma, tumors, and lungs compared with paclitaxel alone. In conclusion, the combination of paclitaxel and masitinib could serve as a novel and useful therapeutic strategy to reverse paclitaxel resistance mediated by ABCC10.

Recent advances regarding the role of ABC subfamily C member 10 (ABCC10) in the efflux of antitumor drugs

ABCC10, also known as multidrug-resistant protein 7 (MRP7), is the tenth member of the C subfamily of the ATP-binding cassette (ABC) superfamily. ABCC10 mediates multidrug resistance (MDR) in cancer cells by preventing the intracellular accumulation of certain antitumor drugs. The ABCC10 transporter is a 171-kDa protein that is localized on the basolateral cell membrane. ABCC10 is a broad-specificity transporter of xenobiotics, including antitumor drugs, such as taxanes, epothilone B, vinca alkaloids, and cytarabine, as well as modulators of the estrogen pathway, such as tamoxifen. In recent years, ABCC10 inhibitors, including cepharanthine, lapatinib, erlotinib, nilotinib, imatinib, sildenafil, and vardenafil, have been reported to overcome ABCC10-mediated MDR. This review discusses some recent and clinically relevant aspects of the ABCC10 drug efflux transporter from the perspective of current chemotherapy, particularly its inhibition by tyrosine kinase inhibitors and phosphodiesterase type 5 inhibitors.

Reversal of MRP7 (ABCC10)-mediated multidrug resistance by tariquidar

Multidrug resistance protein 7 (MRP7, ABCC10) is a recently discovered member of the ATP-binding cassette (ABC) family which are capable of conferring resistance to a variety of anticancer drugs, including taxanes and nucleoside analogs, in vivo. MRP7 is highly expressed in non-small cell lung cancer cells, and Mrp7-KO mice are highly sensitive to paclitaxel, making MRP7 an attractive chemotherapeutic target of non-small cell lung cancer. However, only a few inhibitors of MRP7 are currently identified, with none of them having progressed to clinical trials. We used MRP7-expressing cells to investigate whether tariquidar, a third generation inhibitor of P-glycoprotein, could inhibit MRP7-mediated multidrug resistance (MDR). We found that tariquidar, at 0.1 and 0.3 µM, significantly potentiated the sensitivity of MRP7-transfected HEK293 cells to MRP7 substrates and increased the intracellular accumulation of paclitaxel. We further demonstrated that tariquidar directly impaired paclitaxel efflux and could downregulate MRP7 protein expression in a concentration- and time-dependent manner after prolonged treatment. Our findings suggest that tariquidar, at pharmacologically achievable concentrations, reverses MRP7-mediated MDR through inhibition of MRP7 protein expression and function, and thus represents a promising therapeutic agent in the clinical treatment of chemoresistant cancer patients.