Reversal of multidrug resistance by Fissistigma latifolium-derived chalconoid 2-hydroxy-4,5,6-trimethoxydihydrochalcone in cancer cell lines overexpressing human P-glycoprotein.

Cancer treatment is an evolving field with various challenges to clinical practice. One unresolved problem in this field is multidrug resistance (MDR) mediated by ABC efflux transporters, particularly P-glycoprotein (P-gp). In this study, by prescreening compounds, we identified the potential of a dihydrochalcone compound, 2-hydroxy-4,5,6-trimethoxydihydrochalcone, for P-gp inhibition. Therefore, we investigated its ability to inhibit P-gp and reverse P-gp-mediated MDR, as well as the underlying mechanisms. The P-gp-inhibitory effects of 2-hydroxy-4,5,6-trimethoxydihydrochalcone were investigated as follows. A P-gp efflux assay and an ATPase assay were used to understand the modulatory mechanisms in the drug-binding and ATP-binding areas, respectively. Prominent reversal effects observed in MDR cancer cell lines; thus, reversal, cytotoxicity, cell cycle, apoptosis, and reactive oxygen species assays were conducted to investigate the underlying mechanism. The results indicated that 2-hydroxy-4,5,6-trimethoxydihydrochalcone functionally inhibited P-gp in a noncompetitive manner, and this inhibition was unrelated to expression. In addition, 2-hydroxy-4,5,6-trimethoxydihydrochalcone served as an ATPase stimulator but not as a P-gp substrate. Moreover, a low binding energy of - 6.85 kcal/mol and one hydrogen bond were obtained, indicating that 2-hydroxy-4,5,6-trimethoxydihydrochalcone has a high affinity for P-gp. P-gp-mediated MDR was reversed by 31.6 µM 2-hydroxy-4,5,6-trimethoxydihydrochalcone in combination with paclitaxel, with a reversal fold value of 379.42. In conclusion, this study provides evidence of the ability of 2-hydroxy-4,5,6-trimethoxydihydrochalcone to inhibit P-gp and reverse MDR.

Wilforine resensitizes multidrug resistant cancer cells via competitive inhibition of P-glycoprotein.

BACKGROUND AND PURPOSE: Multidrug resistance (MDR) remains the main obstacle in cancer treatment and overexpression of P-glycoprotein (P-gp) is one of the most common causes of chemoresistance. The development of novel P-gp inhibitors from natural products is a prospective strategy to combat MDR cancers. Among the natural sesquiterpene compounds, sesquiterpene pyridine alkaloids exhibit various biological properties. Therefore, in the present study, we evaluated the modulatory effects of wilforine on P-gp expression and function. The molecular mechanisms and kinetic models of wilforine-mediated P-gp inhibition were further investigated. METHODS: The human P-gp stable expression cells (ABCB1/Flp-InTM-293) and human cervical cancer cells (sensitive: HeLaS3; MDR: KBvin) were used. The cell viability was assessed by SRB assay. The inhibitory effect of wilforine on P-gp efflux and the underlying mechanism were evaluated by assays for calcein-AM uptake, rhodamine123 and doxorubicin efflux, ATPase activity, real-time quantitative RT-PCR, apoptosis, and cell cycle analysis. Molecular docking was performed by the docking software CDOCKER with BIOVIA Discovery Studio 4.5 (D.S. 4.5). RESULTS: We found that wilforine significantly inhibited the efflux activity of P-gp in a concentration-dependent manner. Further kinetic analysis demonstrated that wilforine significantly inhibited P-gp efflux function by competitive inhibition and stimulated the basal P-gp ATPase activity. In addition, wilforine re-sensitized MDR cancer cells to chemotherapeutic drugs. The docking model indicated that wilforine was bound to residues of P-gp such as LEU884, LYS887, THR176 and ASN172. CONCLUSION: These results suggest a novel future therapeutic strategy for MDR cancer using wilforine as an adjuvant treatment with chemotherapy.

Danazol mediates collateral sensitivity via STAT3/Myc related pathway in multidrug-resistant cancer cells.

Multidrug resistance presents an obstacle in cancer treatment. Among numerous combative strategies, collateral sensitivity (CS) drugs have opened a new avenue to defeat cancer by exploiting selective toxicity against multidrug-resistant (MDR) cancer. In the present study, a clinically used synthetic steroid hormone, danazol, was investigated for its CS properties and cytotoxic mechanisms. Compared with natural hormones, danazol possessed a stronger selective cytotoxicity against MDR cancer cells. Danazol induced the arrest of MDR cancer cells at the G2/M phase and caspase-8-related early apoptosis. Furthermore, in MDR cancer cells, danazol reduced STAT3 phosphorylation as well as the expression of STAT3-regulated genes involved in cell survival, such as c-Myc, CDC25, and CDK1. Danazol also upregulated the cell cycle inhibitor p21 in MDR cancer cells. Supporting the experimental results, docking studies have revealed that danazol can likely bind favourably with STAT3. Taken together, our results suggest that danazol exerts a CS effect by inhibiting the STAT3 pathway in MDR cancer cells and thus provides a possible solution for MDR cancers.

Tenulin and isotenulin inhibit P-glycoprotein function and overcome multidrug resistance in cancer cells.

BACKGROUND: Multidrug resistance (MDR) in cancer is one of the main obstacles in treatment with chemotherapy. Drug efflux through P-glycoprotein is the major mechanism involved in MDR. A potential strategy to provide the best possible clinical outcomes is to develop P-glycoprotein (P-gp) inhibitors from natural products. PURPOSE: The present study investigated the effects of the natural sesquiterpene lactone tenulin and its derivative isotenulin on human P-gp; the mechanisms of kinetic interactions were also explored. METHODS: The human P-gp (ABCB1/Flp-In™-293) stable expression cells were established by using the Flp-In™ system. The effects of tenulin and isotenulin on cell viability were evaluated by SRB assays in established cell lines, sensitive cancer cell line (HeLaS3), and resistant cancer cell line (KB-vin). The transporter inhibition ability was evaluated by calcein-AM uptake assays. The P-gp inhibition kinetics of tenulin and isotenulin were evaluated by rhodamine123 and doxorubicin efflux assays. The ATPase activity was evaluated with the Pgp-Glo™ Assay System. RESULTS: Tenulin and isotenulin significantly inhibited the P-gp efflux function by stimulating P-gp ATPase activity. Tenulin and isotenulin interacted with the effluxes of rhodamine 123 and doxorubicin through a competitive and noncompetitive mechanism, respectively. The combinations of tenulin and isotenulin with chemotherapeutic drugs significantly resensitized MDR cancer cells. CONCLUSION: These results suggested that tenulin and isotenulin are potential candidates to be developed for synergistic treatment of MDR cancers.

Taxifolin Resensitizes Multidrug Resistance Cancer Cells via Uncompetitive Inhibition of P-Glycoprotein Function.

P-glycoprotein (P-gp) effluxes lots of chemotherapeutic agents and leads to multidrug resistance (MDR) in cancer treatments. The development of P-gp inhibitors from natural products provide a potential strategy for the beneficial clinical outcomes. This study aimed to evaluate the effects of the natural flavonoid taxifolin, luteolin, (-)-gallocatechin, and (-)-catechin on human P-gp activity. The kinetic interactions and underlying mechanisms of taxifolin-mediated transporter inhibition were further investigated. The transporter inhibition ability was evaluated in human P-gp stable expression cells (ABCB1/Flp-InTM-293) by calcein-AM uptake assays. The kinetics study for P-gp inhibition was evaluated by doxorubicin and rhodamine123 efflux assays. The MDR reversal ability of taxifolin were performed by SRB assays to detect the cell viability in sensitive cancer cell line (HeLaS3), and resistant cancer cell line (KB-vin). Cell cycle analysis and ABCB1 real-time RT-PCR were used for mechanical exploration. The results demonstrated that taxifolin decreased ABCB1 expression in a concentration-dependent manner. The function of P-gp was inhibited by taxifolin through uncompetitive inhibition of rhodamine 123 and doxorubicin efflux. The combination of taxifolin significantly resensitized MDR cancer cells to chemotherapeutic agents. These results suggested that taxifolin may be considered as a potential P-gp modulator for synergistic treatment of MDR cancers.

Effect of Long-term Incretin-Based Therapies on Ischemic Heart Diseases in Patients with Type 2 Diabetes Mellitus: A Network Meta-analysis.

Patients with type 2 diabetes mellitus (T2DM) experience many cardiovascular complications. Several studies have demonstrated the cardioprotective effects of incretin-based therapies; however, there are few studies on the effects of long-term incretin-based therapies on cardiovascular events. Therefore, the present study conducted a systematic review and network meta-analysis to evaluate the effects of long-term incretin-based therapies on ischaemic diseases. We searched PubMed, CENTRAL, and Clinicaltrial.gov to retrieve randomised control trials reported until December 2016 and enrolled only RCTs with more than a 1-year follow-up. The network meta-analysis was performed using R Software with a GeMTC package. A total of 40 trials were included. Dipeptidyl peptidase 4 inhibitors and glucagon-like peptide-1 agonists were associated with a lower risk of myocardial infarction (MI) than were sulfonylureas (odds ratio [95% credible interval] 0.41 [0.24-0.71] and 0.48 [0.27-0.91], respectively). These results suggested that patients with T2DM receiving long-term incretin-based therapies have a lower risk of MI than do those receiving sulfonylurea-based therapy. These findings highlight the risks of cardiovascular events in patients who receive long-term incretin-based therapies, and may provide evidence for the selection of antidiabetic therapy in the future.

The effectiveness of compliance therapy on drug attitude among schizophrenic patients: a systematic review.

BACKGROUND: Schizophrenia is one of the most severe mental illnesses. Studies have found that 25% to 80% of all schizophrenic patients are non-compliant in medication-taking. Non-compliance of medication-taking is associated with higher readmission rates that result from relapses. Compliance therapy has been developed to modify negative beliefs toward medication and aims to improve drug attitude toward medication-taking. However, the effect of compliance therapy on drug attitude among schizophrenic patients is unclear. OBJECTIVES: The objective of this review was to systematically review the available evidence with regards to the effect of compliance therapy on improving attitudes toward medication among schizophrenic patients. TYPES OF PARTICIPANTS: People diagnosed with schizophrenia, schizophrenia-form disorder, delusion disorder, schizo-affective disorder. TYPES OF INTERVENTION(S): The review considered studies that evaluated any form of compliance therapy. The comparator was standard care. TYPES OF STUDIES: The review considered randomized controlled trials. TYPES OF OUTCOMES: Drug attitude measured by the Drug Attitude Inventory. SEARCH STRATEGY: Database searches included MEDLINE, CINAHL, EMBASE, Science Direct, SocIndex, PsycINFO, ERIC, the Web of Science, the National Central Library and the Chinese Electronic Periodical Services databases. Searches were limited to English and Chinese. Search was limited to articles published from 1983 to 2013. METHODOLOGICAL QUALITY: Two reviewers independently appraised the studies using the standardized critical appraisal checklist for randomized control trial and pseudo-randomized trails designed by Joanna Briggs Institute. Disagreements were resolved through discussion. DATA EXTRACTION: A standardized data extraction tool from the Joanna Briggs Institute was used. Data were extracted by two reviewers independently. DATA SYNTHESIS: Due to the concern of heterogeneity, meta-analysis was not considered as an appropriate approach to synthesize data in the current review. A narrative summary was therefore carried out. RESULTS: Three randomized controlled trials met the inclusion criteria. Two studies compared compliance therapy to standard care and both found compliance therapy to significantly improve drug attitude (Drug Attitude Inventory: 1 randomized controlled trial, n=28, mean difference between groups: 4.32, 'p'=0.001; 1 randomized controlled trial, n=47 mean difference between groups: 2.2, 'p<0.001').However, the other study reported that there was no statistically significant difference in the drug attitude score between the two groups (Drug Attitude Inventory: n=50, mean difference between groups: -2.1 'p=0.32'). CONCLUSIONS: The present review found that the majority of the included studies identified an effect of compliance therapy in improving drug attitude. However, the evidence is still weak as the outcome was from three small and heterogeneous studies. Standardization of the compliance therapy and well-designed study is needed to test the effect in the future. Only then, can the therapy be considered to improve attitude toward medication taking among schizophrenic patients.

Qualitative inquiry into motivators for maintaining medication adherence among Taiwanese with schizophrenia.

Medication non-adherence is associated with higher rates of relapse in persons with schizophrenia. Psychiatric nurses play a significant role in facilitating their medication adherence. The motivators which strengthen patients with schizophrenia to maintain their adherence to medication have seldom been explored. This study aims to explore what motivates persons with schizophrenia to consistently maintain their medication adherence. A qualitative approach was used to collect data from a psychiatric day-care centre at an armed forces hospital in Taiwan. Ten clients agreed to undergo an in-depth interview. The data was analyzed by a content analysis method. Four themes were identified: (i) the benefits of antipsychotic medication treatment; (ii) firm and ongoing family support; and the Chinese values of (iii) filial piety and (iv) hope for the future. These findings may provide psychiatric nurses with a better understanding of the motivators for medication adherence in persons with schizophrenia from the Chinese perspective. Nurses will then be able to adjust their practice to facilitate patients' medication adherence.