Project description:Multidrug resistance (MDR) of tumor cells to chemotherapeutic agents is the main reason for the failure of cancer chemotherapy. Overexpression of ABCB1 transporter that actively pumps various drugs out of the cells has been considered a major contributing factor for MDR. Over the past decade, many antimicrobial peptides with antitumor activity have been identified or synthesized, and some antitumor peptides have entered the clinical practice. In this study, we report that peptide HX-12C has the effect of reversing ABCB1-mediated chemotherapy resistance. In ABCB1-overexpressing cells, nontoxic dose of peptide HX-12C inhibited drug resistance and increased the effective intracellular concentration of paclitaxel and other ABCB1 substrate drugs. The mechanism study showed that peptide HX-12C stimulated ABCB1 ATPase activity without changing the expression level and localization patterns of ABCB1. Molecular docking predicted the binding modes between peptide HX-12C and ABCB1. Overall, we found that peptide HX-12C reverses ABCB1-mediated MDR through interacting with ABCB1 and blocking its function without affecting the transporter's expression and cellular localization. Our findings suggest that this antimicrobial peptide may be used as a novel prospective cancer therapeutic strategy in combination with conventional anticancer agents.
Project description:Multidrug resistance (MDR), mainly mediated by ABCB1 transporter, is a major cause for chemotherapy failure. Bufalin (BU), an active component of the traditional Chinese medicine chan'su, has been reported to have antitumor effects on various types of cancer cells. The purpose of this present study was to investigate the reversal effect of BU on ABCB1-mediated multidrug resistance in colorectal cancer. BU at safe concentration (5, 10, 20 nM) could reverse chemosensitivity of ABCB1-overexpression HCT8/ADR, LoVo/ADR and HCT8/ABCB1 nearly back to their parental cells level. In addition, results from the drug accumulation studies revealed that BU was able to enhance intracellular accumulation of doxorubicin (DOX) and Rhodamine 123 (Rho-123) in a dose-dependent manner. Furthermore, Western blot assays showed that BU significantly inhibited the expression level of ABCB1 protein. Meanwhile, BU stimulated the ATPase activity of ABCB1, which suggested that BU might be a substrate of ABCB1. More interestingly, docking analysis predicted that BU could be docked into the large hydrophobic drug-binding cavity of human ABCB1. Importantly, BU remarkable increased the effect of DOX against the ABCB1 resistant HCT8/ADR colorectal cell xenografts in nude mice, without inducing any obvious toxicity. Overall, we concluded that BU efficiently reversed ABCB1-mediated MDR through not only inhibited the efflux function of ABCB1, but also down-regulate its protein expression, which might represent a potential and superior ABCB1 modulator in colorectal cancer.
Project description:Sildenafil is a potent and selective inhibitor of the type 5 cGMP (cyclic guanosine 3',5'-monophosphate)-specific phosphodiesterase that is used clinically to treat erectile dysfunction and pulmonary arterial hypertension. Here, we report that sildenafil has differential effects on cell surface ABC transporters such as ABCB1, ABCC1, and ABCG2 that modulate intracompartmental and intracellular concentrations of chemotherapeutic drugs. In ABCB1-overexpressing cells, nontoxic doses of sildenafil inhibited resistance and increased the effective intracellular concentration of ABCB1 substrate drugs such as paclitaxel. Similarly, in ABCG2-overexpressing cells, sildenafil inhibited resistance to ABCG2 substrate anticancer drugs, for example, increasing the effective intracellular concentration of mitoxantrone or the fluorescent compound BODIPY-prazosin. Sildenafil also moderately inhibited the transport of E(2)17βG and methotrexate by the ABCG2 transporter. Mechanistic investigations revealed that sildenafil stimulated ABCB1 ATPase activity and inhibited photolabeling of ABCB1 with [(125)I]-iodoarylazidoprazosin (IAAP), whereas it only slightly stimulated ABCG2 ATPase activity and inhibited photolabeling of ABCG2 with [(125)I]-IAAP. In contrast, sildenafil did not alter the sensitivity of parental, ABCB1-, or ABCG2-overexpressing cells to non-ABCB1 and non-ABCG2 substrate drugs, nor did sildenafil affect the function of another ABC drug transporter, ABCC1. Homology modeling predicted the binding conformation of sildenafil within the large cavity of the transmembrane region of ABCB1. Overall, we found that sildenafil inhibits the transporter function of ABCB1 and ABCG2, with a stronger effect on ABCB1. Our findings suggest a possible strategy to enhance the distribution and potentially the activity of anticancer drugs by jointly using a clinically approved drug with known side effects and drug-drug interactions.
Project description:The growing number of studies suggested that inhibition of autophagy enhances the efficacy of Akt kinase inhibitors in cancer therapy. Here, we provide evidence that ML-9, a widely used inhibitor of Akt kinase, myosin light-chain kinase (MLCK) and stromal interaction molecule 1 (STIM1), represents the 'two-in-one' compound that stimulates autophagosome formation (by downregulating Akt/mammalian target of rapamycin (mTOR) pathway) and inhibits their degradation (by acting like a lysosomotropic agent and increasing lysosomal pH). We show that ML-9 as a monotherapy effectively induces prostate cancer cell death associated with the accumulation of autophagic vacuoles. Further, ML-9 enhances the anticancer activity of docetaxel, suggesting its potential application as an adjuvant to existing anticancer chemotherapy. Altogether, our results revealed the complex effect of ML-9 on autophagy and indentified ML-9 as an attractive tool for targeting autophagy in cancer therapy through dual inhibition of both the Akt pathway and the autophagy.
Project description:The greatest challenge in cancer therapy is posed by drug-resistant recurrence following treatment. Anticancer chemotherapy is largely focused on targeting the rapid proliferation and biosynthesis of cancer cells. This strategy has the potential to trigger autophagy, enabling cancer cell survival through the recycling of molecules and energy essential for biosynthesis, leading to drug resistance. Autophagy recycling contributes amino acids and ATP to restore mTOR complex 1 (mTORC1) activity, which leads to cell survival. However, autophagy with mTORC1 activation can be stalled by reducing the ATP level. We have previously shown that cytosolic NADH production supported by aldehyde dehydrogenase (ALDH) is critical for supplying ATP through oxidative phosphorylation (OxPhos) in cancer cell mitochondria. Inhibitors of the mitochondrial complex I of the OxPhos electron transfer chain and ALDH significantly reduce the ATP level selectively in cancer cells, terminating autophagy triggered by anticancer drug treatment. With the aim of overcoming drug resistance, we investigated combining the inhibition of mitochondrial complex I, using phenformin, and ALDH, using gossypol, with anticancer drug treatment. Here, we show that OxPhos targeting combined with anticancer drugs acts synergistically to enhance the anticancer effect in mouse xenograft models of various cancers, which suggests a potential therapeutic approach for drug-resistant cancer.
Project description: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.
Project description:Breast cancer resistance protein (BCRP; ABCG2), a clinical marker for identifying the side population (SP) cancer stem cell subgroup, affects intestinal absorption, brain penetration, hepatobiliary excretion, and multidrug resistance of many anti-cancer drugs. Nutlin-3a is currently under pre-clinical investigation in a variety of solid tumor and leukemia models as a p53 reactivation agent, and has been recently demonstrated to also have p53 independent actions in cancer cells. In the present study, we first report that nutlin-3a can inhibit the efflux function of BCRP. We observed that although the nutlin-3a IC(50) did not differ between BCRP over-expressing and vector control cells, nutlin-3a treatment significantly potentiated the cells to treatment with the BCRP substrate mitoxantrone. Combination index calculations suggested synergism between nutlin-3a and mitoxantrone in cell lines over-expressing BCRP. Upon further investigation, it was confirmed that nutlin-3a increased the intracellular accumulation of BCRP substrates such as mitoxantrone and Hoechst 33342 in cells expressing functional BCRP without altering the expression level or localization of BCRP. Interestingly, nutlin-3b, considered virtually "inactive" in disrupting the MDM2/p53 interaction, reversed Hoechst 33342 efflux with the same potency as nutlin-3a. Intracellular accumulation and bi-directional transport studies using MDCKII cells suggested that nutlin-3a is not a substrate of BCRP. Additionally, an ATPase assay using Sf9 insect cell membranes over-expressing wild-type BCRP indicated that nutlin-3a inhibits BCRP ATPase activity in a dose-dependent fashion. In conclusion, our studies demonstrate that nutlin-3a inhibits BCRP efflux function, which consequently reverses BCRP-related drug resistance.
Project description:Growing evidence suggests that tumor-associated macrophages (TAM) promote cancer progression and therapeutic resistance by enhancing angiogenesis, matrix-remodeling, and immunosuppression. In this study, prostate cancer under androgen blockade therapy (ABT) was investigated, demonstrating that TAMs contribute to prostate cancer disease recurrence through paracrine signaling processes. ABT induced the tumor cells to express macrophage colony-stimulating factor 1 (M-CSF1 or CSF1) and other cytokines that recruit and modulate macrophages, causing a significant increase in TAM infiltration. Inhibitors of CSF1 signaling through its receptor, CSF1R, were tested in combination with ABT, demonstrating that blockade of TAM influx in this setting disrupts tumor promotion and sustains a more durable therapeutic response compared with ABT alone.
Project description:In recent years, tyrosine kinase inhibitors (TKIs) have been shown capable of inhibiting the ATP-binding cassette (ABC) transporter-mediated multidrug resistance (MDR). In this study, we determine whether osimertinib, a novel selective, irreversible EGFR (epidermal growth factor receptor) TKI, could reverse ABC transporter-mediated MDR. The results showed that, at non-toxic concentrations, osimertinib significantly sensitized both ABCB1-transfected and drug-selected cell lines to substrate anticancer drugs colchicine, paclitaxel, and vincristine. Osimertinib significantly increased the accumulation of [³H]-paclitaxel in ABCB1 overexpressing cells by blocking the efflux function of ABCB1 transporter. In contrast, no significant alteration in the expression levels and localization pattern of ABCB1 was observed when ABCB1 overexpressing cells were exposed to 0.3 µM osimertinib for 72 h. In addition, ATPase assay showed osimertinib stimulated ABCB1 ATPase activity. Molecular docking and molecular dynamic simulations showed osimertinib has strong and stable interactions at the transmembrane domain of human homology ABCB1. Taken together, our findings suggest that osimertinib, a clinically-approved third-generation EGFR TKI, can reverse ABCB1-mediated MDR, which supports the combination therapy with osimertinib and ABCB1 substrates may potentially be a novel therapeutic stategy in ABCB1-positive drug resistant cancers.
Project description:It has been demonstrated that docetaxel (DTX) may improve the overall survival of patients with castration-resistant prostate cancer (CRPC). However, its effectiveness is limited with time, and tumor escape is eventually inevitable. DTX resistance is the main reason for the failure of chemotherapy for CRPC. In the present study, the expression status of multidrug resistance protein 4 (MRP4) in DTX-resistant prostate cancer cells was investigated, and it was explored whether anti-androgen treatment may inhibit MRP4 expression and overcome DTX resistance. DTX-resistant C4-2/D cells were established by exposing DTX-sensitive C4-2/S cells to gradually increasing concentrations of DTX. MRP4 gene expression and the effect of androgen signaling on its expression were assessed by reverse transcription-polymerase chain reaction and western blotting. Intracellular and extracellular concentrations of DTX were detected by high-performance liquid chromatography. Anti-androgen treatment effects on DTX sensitivity were determined by a clonogenic test and an MTT cytotoxicity assay. MRP4 was overexpressed in C4-2/D cells, while its expression was barely detectable in C4-2/S cells. MRP4 expression levels were elevated in C4-2/D cells by dihydrotestosterone, whereas they were blocked by anti-androgen bicalutamide (BKL) treatment. Intracellular and extracellular DTX concentrations in C4-2/D cells were associated with MRP4 levels. The downregulation of MRP4 by BKL increased the intracellular concentration of DTX in C4-2/D cells and re-sensitized C4-2/D cells to DTX. These results indicated that overexpression of MRP4 mediates acquired DTX resistance, and suggest that targeting MRP4 expression by anti-androgen treatment may reverse DTX-resistant prostate cancer cells to DTX chemotherapy.