Reversal effects of two new milbemycin compounds on multidrug resistance in MCF-7/adr cells in vitro

A (Traditional Chinese Medicine) TCM-Inspired Doxorubicin Resistance Reversing Strategy: Preparation, Characterization, and Application of a Co-loaded pH-Sensitive Liposome

In this study, nano-strategy for combined medication of active compounds from traditional Chinese medicine herbs was proposed to achieve the synergistic effects of inhibiting the doxorubicin (DOX) resistance, reducing the cardio-toxicity, and improving the treatment efficacy simultaneously. Dihydroartemisinin (DHA) and tetrandrine (TET) were co-delivered for the first time to treat DOX resistance of breast cancer with multi-pathway mechanism. Tumor micro-environment sensitivity prescription was adopted to enhance the reversal effect of DOX resistance nearly 50 times (resistance index, RI was 46.70) and uptake ability. The DHA-TET pH-sensitive liposomes (DHA-TET pH-sensitive LPs) had a good spherical structure and a uniform dispersion structure with particle size, polydispersity index (PDI), and zeta potential of 112.20 ± 4.80 nm, 0.20 ± 0.02, and - 8.63 ± 0.74 Mv, and was stable until 14 days under the storage environment of 4°C and for 6 months at room temperature environment. With the DOX resistance reversing ability increased, the inhibition effect of DHA-TET pH-sensitive LPs on both MCF-7/ADR cells and MCF-7 cells was significantly enhanced; meanwhile, the toxicity on cardiac cell (H9c2) was lowered. Ferroptosis induced by the DHA was investigated showing that the intracellular reactive oxygen species (ROS) and lipid peroxidation were increased to promote the synergistic effect through the due-loaded nano-carrier, providing a promising alternative for future clinical application.

Repositioning of Antiparasitic Drugs for Tumor Treatment

Drug repositioning is a strategy for identifying new antitumor drugs; this strategy allows existing and approved clinical drugs to be innovatively repurposed to treat tumors. Based on the similarities between parasitic diseases and cancer, recent studies aimed to investigate the efficacy of existing antiparasitic drugs in cancer. In this review, we selected two antihelminthic drugs (macrolides and benzimidazoles) and two antiprotozoal drugs (artemisinin and its derivatives, and quinolines) and summarized the research progresses made to date on the role of these drugs in cancer. Overall, these drugs regulate tumor growth via multiple targets, pathways, and modes of action. These antiparasitic drugs are good candidates for comprehensive, in-depth analyses of tumor occurrence and development. In-depth studies may improve the current tumor diagnoses and treatment regimens. However, for clinical application, current investigations are still insufficient, warranting more comprehensive analyses.

A milbemycin compound isolated from Streptomyces Sp. FJS31-2 with cytotoxicity and reversal of cisplatin resistance activity in A549/DDP cells

Streptomyces Sp FJS31-2 is a strain isolated from special habitat soils in the early stage of our laboratory for producing a new type of halogenated type II polyketide antibiotic with good anti-MRSA activity. In this experiment, a variety of chromatographic and spectroscopic methods was used to isolate and identify a milbemycin compound VM48130 from the ethyl acetate extract of the fermentation products. To investigate its bioactivity, Cell Counting Kit-8 (CCK-8) assay was used to test the cytotoxic activity of the compound against a variety of cancer cells (human liver cancer cell line MHCC97H and SK-Hep1, human nasopharyngeal carcinoma cell line CNE1, mouse melanoma cell line B16, human colon cancer cell line LOVO, human lung adenocarcinoma cell line A549) and normal cells (human bronchial epithelial cell line 16HBE, human normal liver cell line L02, human nasopharyngeal epithelial cell line NP69). The results showed that the compound had significant cytotoxic activity against the above cancer cells, and the IC₅₀ values were 21.96 ± 1.45, 22.18 ± 0.55, 19.42 ± 0.71, 18.61 ± 1.68, 18.62 ± 0.67, 18.52 ± 0.64 μM, respectively. Furthermore, the CCK-8 method was used to evaluate the compound's reversal of cisplatin resistance in multidrug resistant cisplatin-resistant human lung adenocarcinoma (A549/DDP) cells. The results indicated that when the compound concentration was 0.5 μM, the reversal fold (RF) reached 6.25 and showed a dose-dependent effect. At 5 μM, the RF reached 8.35, which was approximately equivalent to the reversal effect of the positive drug verapamil at the same concentration. The expression of MDR1, MRP1, LRP, MAST1 resistance genes and the corresponding proteins were analyzed by quantitative RT-PCR and Western blot assay, and found that the compound could significantly down-regulate the expression of these genes and proteins. These results indicated that VM48130 had the potential of being a lead compound for the treatment or adjuvant treatment of cancer.

Barbigerone reverses multidrug resistance in breast MCF-7/ADR cells

Development of agents to overcome multidrug resistance (MDR) is one of the important strategies in cancer chemotherapy, and P-glycoprotein (P-gp) correlates with the degree of resistance. As a naturally occurring isoflavone, whether barbigerone (BA) could reverse MDR, is unknown. In this paper, we evaluated effects of BA on reversing P-gp mediated MDR of adriamycin (ADR)-resistant human breast carcinoma (MCF-7/ADR) cells. BA (0.5 μM) treatment showed strong potency to increase ADR cytotoxicity toward MCF-7/ADR cells. It was also demonstrated that BA time- and dose-dependently increased accumulations of ADR and reduced the efflux in MCF-7/ADR cells, pretreatment of these cells with BA might relocalized ADR to the nuclei. Furthermore, the results also revealed that BA did not affect P-gp, but alter P-gp ATPase activity. Intravenous administration of BA significantly increased anticancer efficacy of ADR to MCF-7/ADR xenograft model in nude mice. These results revealed that BA might reverse P-gp mediated MDR through inhibition of ATPase activity, which indicated a novel use of BA as a potent candidate for cancer chemotherapy.

Astragaloside Ⅳ reduces the expression level of P-glycoprotein in multidrug-resistant human hepatic cancer cell lines

Astragaloside is a saponin widely used in traditional Chinese medicine and has been reported to be a potent multidrug resistance (MDR) reversal agent. The present study investigated the role of astragaloside Ⅳ (ASIV) in the regulation of P-glycoprotein (P-gp, encoded by the mdr1 gene) and its effect on the reversal of MDR. The activity of ASIV was evaluated using human hepatic cancer cells Bel-7402 and the corresponding 5-fluorouracil (5-FU) resistant cells Bel-7402/FU. ASIV (0.08 mg/ml) potentiated the cytotoxicity of 5-FU which was demonstrated using the MTT assay on Bel-7402/FU cells. ASIV reduced the expression of P-gp as was revealed by immunocytochemistry. Accumulation and efflux studies with the P-gp substrate, rhodamine 123 (Rh123), demonstrated that ASIV inhibited P-gp-mediated drug efflux. Furthermore, it was demonstrated that ASⅣ enhanced the drug accumulation of 5-FU using a high performance liquid chromatography (HPLC) assay for drug resistant cells. Furthermore, ASIV may downregulate the expression of P-gp, which was examined using western blot analysis and polymerase chain reaction. In conclusion, the results of the present study indicated that ASIV reverses the drug resistance of Bel-7402/FU cells by downregulating the expression of mdr1. ASIV may represent a potent modulator of P-gp-mediated MDR in hepatic cancer therapy.

Drug efflux transporters and multidrug resistance in acute leukemia: therapeutic impact and novel approaches to mediation

Multidrug resistance (MDR), which is mediated by multiple drug efflux ATP-binding cassette (ABC) transporters, is a critical issue in the treatment of acute leukemia, with permeability glycoprotein (P-gp), multidrug resistance-associated protein 1, and breast cancer resistance protein (i.e., ABCG2) consistently being shown to be key effectors of MDR in cell line studies. Studies have demonstrated that intrinsic MDR can arise as a result of specific gene expression profiles and that drug-induced overexpression of P-gp and other MDR proteins can result in acquired resistance, with multiple ABC transporters having been shown to be overexpressed in cell lines selected for resistance to multiple drugs used to treat acute leukemia. Furthermore, numerous anticancer drugs, including agents commonly used for the treatment of acute leukemia (e.g., doxorubicin, vincristine, mitoxantrone, and methotrexate), have been shown to be P-gp substrates or to be susceptible to efflux mediated by other MDR proteins, and multiple clinical studies have demonstrated associations between P-gp or other MDR protein expression and responses to therapy or survival rates in acute leukemia. Here we review the importance of MDR in cancer, with a focus on acute leukemia, and we highlight the need for rapid accurate assessment of MDR status for optimal treatment selection. We also address the latest research on overcoming MDR, from inhibition of P-gp and other MDR proteins through various approaches (including direct antagonism and gene silencing) to the design of novel agents or novel delivery systems for existing therapeutic agents, to evade cellular efflux.

Moxidectin and the avermectins: Consanguinity but not identity

The avermectins and milbemycins contain a common macrocyclic lactone (ML) ring, but are fermentation products of different organisms. The principal structural difference is that avermectins have sugar groups at C13 of the macrocyclic ring, whereas the milbemycins are protonated at C13. Moxidectin (MOX), belonging to the milbemycin family, has other differences, including a methoxime at C23. The avermectins and MOX have broad-spectrum activity against nematodes and arthropods. They have similar but not identical, spectral ranges of activity and some avermectins and MOX have diverse formulations for great user flexibility. The longer half-life of MOX and its safety profile, allow MOX to be used in long-acting formulations. Some important differences between MOX and avermectins in interaction with various invertebrate ligand-gated ion channels are known and could be the basis of different efficacy and safety profiles. Modelling of IVM interaction with glutamate-gated ion channels suggest different interactions will occur with MOX. Similarly, profound differences between MOX and the avermectins are seen in interactions with ABC transporters in mammals and nematodes. These differences are important for pharmacokinetics, toxicity in animals with defective transporter expression, and probable mechanisms of resistance. Resistance to the avermectins has become widespread in parasites of some hosts and MOX resistance also exists and is increasing. There is some degree of cross-resistance between the avermectins and MOX, but avermectin resistance and MOX resistance are not identical. In many cases when resistance to avermectins is noticed, MOX produces a higher efficacy and quite often is fully effective at recommended dose rates. These similarities and differences should be appreciated for optimal decisions about parasite control, delaying, managing or reversing resistances, and also for appropriate anthelmintic combination.

P-glycoproteins and other multidrug resistance transporters in the pharmacology of anthelmintics: Prospects for reversing transport-dependent anthelmintic resistance

Parasitic helminths cause significant disease in animals and humans. In the absence of alternative treatments, anthelmintics remain the principal agents for their control. Resistance extends to the most important class of anthelmintics, the macrocyclic lactone endectocides (MLs), such as ivermectin, and presents serious problems for the livestock industries and threatens to severely limit current parasite control strategies in humans. Understanding drug resistance is important for optimizing and monitoring control, and reducing further selection for resistance. Multidrug resistance (MDR) ABC transporters have been implicated in ML resistance and contribute to resistance to a number of other anthelmintics. MDR transporters, such as P-glycoproteins, are essential for many cellular processes that require the transport of substrates across cell membranes. Being overexpressed in response to chemotherapy in tumour cells and to ML-based treatment in nematodes, they lead to therapy failure by decreasing drug concentration at the target. Several anthelmintics are inhibitors of these efflux pumps and appropriate combinations can result in higher treatment efficacy against parasites and reversal of resistance. However, this needs to be balanced against possible increased toxicity to the host, or the components of the combination selecting on the same genes involved in the resistance. Increased efficacy could result from modifying anthelmintic pharmacokinetics in the host or by blocking parasite transporters involved in resistance. Combination of anthelmintics can be beneficial for delaying selection for resistance. However, it should be based on knowledge of resistance mechanisms and not simply on mode of action classes, and is best started before resistance has been selected to any member of the combination. Increasing knowledge of the MDR transporters involved in anthelmintic resistance in helminths will play an important role in allowing for the identification of markers to monitor the spread of resistance and to evaluate new tools and management practices aimed at delaying its spread.