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

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

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

Adagrasib, a KRAS G12C inhibitor, reverses the multidrug resistance mediated by ABCB1 in vitro and in vivo

Background

Multidrug resistance (MDR) is a complex phenomenon that frequently leads to chemotherapy failure during cancer treatment. The overexpression of ATP-binding cassette (ABC) transporters represents the major mechanism contributing to MDR. To date, no effective MDR modulator has been applied in clinic. Adagrasib (MRTX849), a specific inhibitor targeting KRAS G12C mutant, is currently under investigation in clinical trials for the treatment of non-small cell lung cancer (NSCLC). This study focused on investigating the circumvention of MDR by MRTX849.

Methods

The cytotoxicity and MDR reversal effect of MRTX849 were assessed by MTT assay. Drug accumulation and drug efflux were evaluated by flow cytometry. The MDR reversal by MRTX849 in vivo was investigated in two ABCB1-overexpressing tumor xenograft models in nude mice. The interaction between MRTX849 and ABCB1 substrate binding sites was studied by the [125I]-IAAP-photoaffinity labeling assay. The vanadate-sensitive ATPase assay was performed to identify whether MRTX849 would change ABCB1 ATPase activity. The effect of MRTX849 on expression of ABCB1 and PI3K/AKT signaling molecules was examined by flow cytometry, Western blot and Quantitative Real-time PCR analyses.

Results

MRTX849 was shown to enhance the anticancer efficacy of ABCB1 substrate drugs in the transporter-overexpressing cells both in vitro and in vivo. The MDR reversal effect was specific against ABCB1 because no similar effect was observed in the parental sensitive cells or in ABCG2-mediated MDR cells. Mechanistically, MRTX849 increased the cellular accumulation of ABCB1 substrates including doxorubicin (Dox) and rhodamine 123 (Rho123) in ABCB1-overexpressing MDR cells by suppressing ABCB1 efflux activity. Additionally, MRTX849 stimulated ABCB1 ATPase activity and competed with [125I]-IAAP for photolabeling of ABCB1 in a concentration-dependent manner. However, MRTX849 did not alter ABCB1 expression or phosphorylation of AKT/ERK at the effective MDR reversal drug concentrations.

Conclusions

In summary, MRTX849 was found to overcome ABCB1-mediated MDR both in vitro and in vivo by specifically attenuating ABCB1 efflux activity in drug-resistant cancer cells. Further studies are warranted to translate the combination of MRTX849 and conventional chemotherapy to clinical application for circumvention of MDR.

The inhibitory effect and mechanism of Yi-qi-hua-yu-jie-du decoction on the drug resistance of gastric cancer stem cells based on ABC transporters

Background

The drug resistance of tumor stem cells is an obstacle in gastric cancer (GC) treatment and the high expression of ABC transporters is a classic reason for drug resistance. This study aimed to construct a reliable GC drug-resistant stem cell model and explore the inhibitory effect and mechanism of Yi-qi-hua-yu-jie-du medicated serum (YQHY) on the drug resistance of GC stem cells based on ABC transporters.

Methods

The tumor stemness biomarker CD44 was primary identification from WGCNA. The magnetic-activated cell sorting (MACS) method was used to separate CD44( +)BGC823/5-Fu (BGC823/5–Fu-CSCs) cells and the stemness characteristics were verified from multiple dimensions. Then, the drug resistance index and expression of ABC transporter genes MDR1 and MRP1 were detected in CD44(−)/CD44(+) cells. The inhibition and apoptosis rates of the cells administrated with YQHY or/and 5-Fu were calculated to confirm that YQHY can suppress the drug resistance of BGC823/5-Fu-CSCs. Afterwards, the effects of YQHY on the expression of MDR1 and MRP1 and the activation of the PI3K/Akt/Nrf2 pathway were observed. Finally, under the administration of IGF-1 (the activator of PI3K/Akt pathway) and Nrf2 siRNA, the mechanism of YQHY on reversing the drug resistance of BGC823/5–Fu-CSCs through inhibiting the expression of MDR1 and MRP1 via PI3K/Akt/Nrf2 was verified.

Results

CD44 was a reliable GC stemness biomarker and can be applied to construct the drug-resistant GC stem cell model CD44(+)BGC823/5-Fu. The growth rate, cell proliferation index, soft agar colony formation, expression of stemness specific genes and tumorigenesis ability of CD44(+)BGC823/5-Fu cells were significantly higher than those of CD44(−)BGC823/5-Fu cells. BGC823/5–Fu-CSCs exhibited strong drug resistance to 5-Fu and high expression of ABC transporter genes MDR1 and MRP1 compared to CD44(-) cells. YQHY increased the inhibition and apoptosis rates to efficiently inhibit the drug resistance of BGC823/5–Fu-CSCs. Meanwhile, it suppressed the expression of MDR1 and MRP1 and restrained the activation of PI3K/Akt/Nrf2 signaling pathway. Finally, it was found that IGF-1 partially restored the activation of PI3K/Akt/Nrf2 pathway, alleviated the inhibition of MDR1 and MRP1, blocked the proliferation-inhibitory and apoptosis-promotion effects. YQHY and si-Nrf2 synergistically suppressed the MDR1/MRP1 expression and the drug resistance of BGC823/5–Fu-CSCs.

Conclusions

CD44 was a reliable GC stemness biomarker, and the high expression of ABC transporter genes MDR1 and MRP1 was an important feature of drug-resistant stem cells. YQHY inhibited the MDR1 and MRP1 expression via PI3K/Akt/Nrf2 pathway, thus reversing the drug resistance of BGC823/5–Fu-CSCs.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13020-022-00647-y.

A curated binary pattern multitarget dataset of focused ATP-binding cassette transporter inhibitors

Multitarget datasets that correlate bioactivity landscapes of small-molecules toward different related or unrelated pharmacological targets are crucial for novel drug design and discovery. ATP-binding cassette (ABC) transporters are critical membrane-bound transport proteins that impact drug and metabolite distribution in human disease as well as disease diagnosis and therapy. Molecular-structural patterns are of the highest importance for the drug discovery process as demonstrated by the novel drug discovery tool ‘computer-aided pattern analysis’ (‘C@PA’). Here, we report a multitarget dataset of 1,167 ABC transporter inhibitors analyzed for 604 molecular substructures in a statistical binary pattern distribution scheme. This binary pattern multitarget dataset (ABC_BPMDS) can be utilized for various areas. These areas include the intended design of (i) polypharmacological agents, (ii) highly potent and selective ABC transporter-targeting agents, but also (iii) agents that avoid clearance by the focused ABC transporters [e.g., at the blood-brain barrier (BBB)]. The information provided will not only facilitate novel drug prediction and discovery of ABC transporter-targeting agents, but also drug design in general in terms of pharmacokinetics and pharmacodynamics.

Measurement(s)	Influx • Efflux • Tracer • Transport velocity
Technology Type(s)	Fluorometry • Radioactivity • Plate reader • Flow cytometer • Tracer distribution
Factor Type(s)	half-maximal inhibition concentration
Sample Characteristic - Organism	Homo sapiens
Sample Characteristic - Environment	cell culture
Sample Characteristic - Location	Kingdom of Norway • Germany • Australia • Latvia

High expression of nuclear NRF2 combined with NFE2L2 alterations predicts poor prognosis in esophageal squamous cell carcinoma patients

Nuclear factor erythroid-2 related factor-2 (NFE2L2 or NRF2) is a frequently mutated gene in esophageal squamous cell carcinoma (ESCC). However, the roles of NFE2L2 alterations in ESCC remain elusive. In order to elucidate this issue, 130 ESCC patients who underwent esophagectomy were enrolled. The majority of tumor tissues were positive for NRF2, which was significantly enriched in the nucleus of the primary tumor tissues compared with the noncancerous mucosae. Primary ESCC tumors positive for NRF2 tended to be positive for NAD(P)H quinone oxidoreductase 1 (NQO1) as the downstream target of NRF2. There was a positive correlation between NRF2 and NQO1 expression level in primary tumors. NQO1 staining in primary tumors with NRF2 nuclear expression was significantly stronger than that with NRF2 cytoplasmic expression. In addition, high concordance for the status of NRF2 expression between primary tumors and corresponding metastatic lesions was observed. Next, we found high expression of nuclear NRF2 (the proportion of nuclear NRF2 expression >20% or nuclear NRF2 immunohistochemistry score >20) predicted shorter overall survival in patients with dual-positive expression of NRF2 and NQO1. Captured-based targeted sequencing revealed that NFE2L2 somatic alterations were observed in 52.8% of ESCC patients with dual-positive expression of NRF2 and NQO1. NFE2L2 amplification and mutations within the DLG/ETGE motifs were seen more frequently in ESCC tumors with nuclear or nucleocytoplasmic expression of NRF2 compared with those with cytoplasmic expression of NRF2. We also found high expression of nuclear NRF2 plus the status of NFE2L2 alteration exhibited high performance in predicting prognosis of ESCC patients. Our study demonstrated that high nuclear NRF2 expression and NFE2L2 alterations were associated with poor prognosis of ESCC patients. These findings suggest that NRF2 signaling pathway might play vital roles in ESCC malignancy and the aberrant activation of NRF2 pathway predicts unfavorable prognosis in ESCC.

Perindopril sensitizes hepatocellular carcinoma to chemotherapy: A possible role of leptin / Wnt/ β-catenin axis with subsequent inhibition of liver cancer stem cells

Hepatocellular carcinoma (HCC) is one of the leading causes of cancer-related death. The major challenge in managing HCC is the resistance to chemotherapy. Leptin hormone is associated with different oncogenic pathways implicated in drug resistance. Angiotensin II was found to decrease the production and secretion of leptin.

Objective

This study investigated the potential role of an ACEI perindopril as a chemosensitizer agent to sorafenib.

Method

HCC was induced in mice using a single dose of diethylnitrosamine DENA (200 mg/kg) followed by phenobarbital 0.05% in drinking water for 16 weeks. Mice were then treated with perindopril (1 mg/kg/day), Sorafenib (30 mg/kg/day), or both of them for another four weeks. Leptin, VEGF, MMP-9, Cyclin D1, EpCAM, and β-catenin were measured using immunoassay while Wnt and ALDH1 were assayed using western blotting assay.

Results

Perindopril whether alone or in combination with sorafenib decrease liver enzymes and preserve the liver architecture. Our study revealed that perindopril significantly increased the antineoplastic, antiangiogenic as well as anti-metastatic effects of sorafenib. This effect was correlated with the downregulation of the leptin / Wnt / β-catenin pathway and overexpression of ALDH1 while downregulation of EpCAM

Conclusion

This study presents perindopril as a potential chemosensitizer agent that works through decreased expression of the leptin / Wnt / β-catenin pathway.

Combination of Elacridar with Imatinib Modulates Resistance Associated with Drug Efflux Transporters in Chronic Myeloid Leukemia

Multidrug resistance (MDR) development has emerged as a complication that compromises the success of several chemotherapeutic agents. In chronic myeloid leukemia (CML), imatinib resistance has been associated with changes in BCR-ABL1 and intracellular drug concentration, controlled by SLC and ABC transporters. We evaluate the therapeutic potential of a P-glycoprotein and BCRP inhibitor, elacridar, in sensitive (K562 and LAMA-84) and imatinib-resistant (K562-RC and K562-RD) CML cell lines as monotherapy and combined with imatinib. Cell viability was analyzed by resazurin assay. Drug transporter activity, cell death, cell proliferation rate, and cell cycle distribution were analyzed by flow cytometry. Both resistant models presented an increased activity of BCRP and P-gP compared to K562 cells. Elacridar as monotherapy did not reach IC50 in any CML models but activated apoptosis without cytostatic effect. Nevertheless, the association of elacridar (250 nM) with imatinib overcomes resistance, re-sensitizing K562-RC and K562-RD cells with five and ten times lower imatinib concentrations, respectively. Drug combination induced apoptosis with increased cleaved-caspases-3, cleaved-PARP and DNA damage, reduced cell proliferation rate, and arrested CML cells in the S phase. These data suggest that elacridar combined with imatinib might represent a new therapeutic option for overcoming TKI resistance involving efflux transporters.

Meclofenamic Acid Restores Gefinitib Sensitivity by Downregulating Breast Cancer Resistance Protein and Multidrug Resistance Protein 7 via FTO/m6A-Demethylation/c-Myc in Non-Small Cell Lung Cancer

Background and Objective

Gefitinib (GE) is a first-line epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI) for patients with advanced non-small cell lung cancer (NSCLC) carrying EGFR activating mutations. However, drug resistance limits the clinical efficacy of gefitinib and ultimately leads to extremely poor clinical benefit. Meclofenamic acid (MA) is a non-steroidal anti-inflammatory drug (NSAID) that relieves moderate and severe pain. In the present study, we aim to determine the MA sensibilization of GE in NSCLC.

Methods

MTT assay was conducted to determine the synergistic effect of MA with GE in GE-sensitive and -resistant cell lines based on the Chou–Talalay method. The Annexin V-PI flow cytometry analysis was conducted to evaluate apoptosis. Western blot assay was used to detect alterations of EGFR downstream molecules. Tritium-labeled GE accumulation analysis was used to determine the efflux activity of GE. Dot blot assays were conducted to determine m6A levels after the MA and GE co-administration. Western blot evaluated the expression of FTO, c-Myc, MRP7, BCRP, and apoptotic proteins.

Results

MA showed a significant synergistic effect with GE in GE-resistant NSCLC cells; co-administration of MA with GE induced caspase-related apoptosis in resistant NSCLC cells. Moreover, EGFR downstream molecules, including Akt and MAPKs pathways, were significantly inhibited by the MA-GE combination. Short-term incubation of MA did not alter the efflux of GE; however, after incubation for 24 h, the accumulation of tritium-labeled GE significantly increased. A mechanism study showed that co-administration of MA and GE significantly downregulated BCRP and MRP7 expression in GE-resistant cells; increased N6-methylation was also observed after co-administration. The FTO/c-Myc was determined as target pathways on MA and GE co-administration mechanisms.

Conclusion

Our findings provide novel therapeutic approaches for GE-resistant NSCLC by combination use with MA through FTO-mediated N6-demethylation.

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

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

Lapatinib Suppresses HER2-Overexpressed Cholangiocarcinoma and Overcomes ABCB1- Mediated Gemcitabine Chemoresistance

Background

Recent breakthroughs in cholangiocarcinoma (CCA) genomics have led to the discovery of many unique identifying mutations, of which HER2 has been found to be overexpressed specifically in cases of extrahepatic CCA. However, whether or not lapatinib (an oral tyrosine kinase inhibitor selective for inhibition of HER2), or a combination of lapatinib and gemcitabine, exerts inhibitory effects on HER2-overexpressed CCA is still unclear.

Methods

The effect of lapatinib and a lapatinib-gemcitabine combination treatment on CCA was determined using organoid and cell line models. Cell cycle arrest, apoptosis and proteins involving HER2-dependent downstream signaling pathways were analyzed to assess the effect of lapatinib on HER2⁺ CCA. The synergistic effect of lapatinib and gemcitabine was interpreted by docking analysis, ABCB1-associated ATPase assay, rhodamine transport assay and LC-MS/MS analyses.

Results

dFdCTP, the active metabolite of gemcitabine, is proved to be the substrate of ABCB1 by docking analysis and ATPase assay. The upregulation of ABCB1 after gemcitabine treatment accounts for the resistance of gemcitabine. Lapatinib exerts a dual effect on HER2-overexpressed CCA, suppressing the growth of CCA cells by inhibiting HER2 and HER2-dependent downstream signaling pathways while inhibiting ABCB1 transporter function, allowing for the accumulation of active gemcitabine metabolites within cells.

Conclusions

Our data demonstrates that lapatinib can not only inhibit growth of CCA overexpressing HER2, but can also circumvent ABCB1-mediated chemoresistance after gemcitabine treatment. As such, this provides a preclinical rationale basis for further clinical investigation into the effectiveness of a combination treatment of lapatinib with gemcitabine in HER2-overexpressed CCA.

Understanding Drug Sensitivity and Tackling Resistance in Cancer

Decades of research into the molecular mechanisms of cancer and the development of novel therapeutics have yielded a number of remarkable successes. However, our ability to broadly assign effective, rationally targeted therapies in a personalized manner remains elusive for many patients, and drug resistance persists as a major problem. This is in part due to the well-documented heterogeneity of cancer, including the diversity of tumor cell lineages and cell states, the spectrum of somatic mutations, the complexity of microenvironments, and immune-suppressive features and immune repertoires, which collectively require numerous different therapeutic approaches. Here, we describe a framework to understand the types and biological causes of resistance, providing translational opportunities to tackle drug resistance by rational therapeutic strategies.

Molecular Mechanisms of Resistance to Tyrosine Kinase Inhibitors Associated with Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is the second leading cause of cancer-related death, which can be attributed to the high incidence and first diagnosis at an advanced stage. Tyrosine kinase inhibitors (TKIs), a class of small-molecule targeting drugs, are primarily used for the clinical treatment of HCC after chemotherapy because they show significant clinical efficacy and low incidence of clinical adverse reactions. However, resistance to sorafenib and other TKIs, which can be used to treat advanced HCC, poses a significant challenge. Recent mechanistic studies have shown that epithelial-mesenchymal transition or transformation (EMT), ATP binding cassette (ABC) transporters, hypoxia, autophagy, and angiogenesis are involved in apoptosis, angiogenesis, HCC cell proliferation, and TKI resistance in patients with HCC. Exploring and overcoming such resistance mechanisms is essential to extend the therapeutic benefits of TKIs to patients with TKI-resistant HCC. This review aims to summarize the potential resistance mechanism proposed in recent years and methods to reverse TKI resistance in the context of HCC.

Infigratinib (BGJ 398), a Pan-FGFR Inhibitor, Targets P-Glycoprotein and Increases Chemotherapeutic-Induced Mortality of Multidrug-Resistant Tumor Cells

The microtubule-targeting agents (MTAs) are well-known chemotherapeutic agents commonly used for therapy of a broad spectrum of human malignancies, exhibiting epithelial origin, including breast, lung, and prostate cancer. Despite the impressive response rates shortly after initiation of MTA-based therapy, the vast majority of human malignancies develop resistance to MTAs due to the different mechanisms. Here, we report that infigratinib (BGJ 398), a potent FGFR1-4 inhibitor, restores sensitivity of a broad spectrum of ABCB1-overexpressing cancer cells to certain chemotherapeutic agents, including paclitaxel (PTX) and doxorubicin (Dox). This was evidenced for the triple-negative breast cancer (TNBC), and gastrointestinal stromal tumor (GIST) cell lines, as well. Indeed, when MDR-overexpressing cancer cells were treated with a combination of BGJ 398 and PTX (or Dox), we observed a significant increase of apoptosis which was evidenced by an increased expression of cleaved forms of PARP, caspase-3, and increased numbers of Annexin V-positive cells, as well. Moreover, BGJ 398 used in combination with PTX significantly decreased the viability and proliferation of the resistant cancer cells. As expected, no apoptosis was found in ABCB1-overexpressing cancer cells treated with PTX, Dox, or BGJ 398 alone. Inhibition of FGFR-signaling by BGJ 398 was evidenced by the decreased expression of phosphorylated (i.e., activated) forms of FGFR and FRS-2, a well-known adaptor protein of FGFR signaling, and downstream signaling molecules (e.g., STAT-1, -3, and S6). In contrast, expression of MDR-related ABC-transporters did not change after BGJ 398 treatment, thereby suggesting an impaired function of MDR-related ABC-transporters. By using the fluorescent-labeled chemotherapeutic agent PTX-Alexa488 (Flutax-2) and doxorubicin, exhibiting an intrinsic fluorescence, we found that BGJ 398 substantially impairs their efflux from MDR-overexpressing TNBC cells. Moreover, the efflux of Calcein AM, a well-known substrate for ABCB1, was also significantly impaired in BGJ 398-treated cancer cells, thereby suggesting the ABCB1 as a novel molecular target for BGJ 398. Of note, PD 173074, a potent FGFR1 and VEGFR2 inhibitor failed to retain chemotherapeutic agents inside ABCB1-overexpressing cells. This was consistent with the inability of PD 173074 to sensitize Tx-R cancer cells to PTX and Dox. Collectively, we show here for the first time that BGJ 398 reverses the sensitivity of MDR-overexpressing cancer cells to certain chemotherapeutic agents due to inhibition of their efflux from cancer cells via ABCB1-mediated mechanism.

Exploration of novel phthalazinone derivatives as potential efflux transporter inhibitors for reversing multidrug resistance and improving the oral absorption of paclitaxel

Chemotherapy is an important means of cancer treatment. However, overexpression of efflux transporters (including but not limited to P-gp and BCRP) can lead to resistance to cancer chemotherapy. Multiple-target inhibitors of efflux transporter can be overcome the resistance and improve the oral bioavailability of chemotherapy drugs. Therefore, we designed and synthesized a series of phthalazinone ring derivatives (1-20) with different aromatic heterocycles substituents on the amide bond for dual inhibition of P-gp and BCRP. Most target compounds significantly increased the accumulation of P-gp substrates in the chemo-resistant cancer cell lines by inhibiting the efflux of transporters. Compound 19 in particular showed stronger MDR reversal compared to Gefitinib and Verapamil, and comparable to that of the BCRP inhibitor Ko143. In addition, compound 19 improved intestinal absorption of paclitaxel (PTX) and enhanced the bioavailability of the orally administered drug in vivo.

Copper-Based Metal-Organic Framework Overcomes Cancer Chemoresistance through Systemically Disrupting Dynamically Balanced Cellular Redox Homeostasis

Chemodrug resistance is a major reason accounting for tumor recurrence. Given the mechanistic complexity of chemodrug resistance, molecular inhibitors and targeting drugs often fail to eliminate drug-resistant cancer cells, and sometimes even promote chemoresistance by activating alternative pathways. Here, by exploiting biochemical fragility of high-level but dynamically balanced cellular redox homeostasis in drug-resistant cancer cells, we design a nanosized copper/catechol-based metal-organic framework (CuHPT) that effectively disturbs this homeostasis tilting the balance toward oxidative stress. Within drug-resistant cells, CuHPT starts disassembly that is triggered by persistent consumption of cellular glutathione (GSH). CuHPT disassembly simultaneously releases two structural elements: catechol ligands and reductive copper ions (Cu⁺). Both of them cooperatively function to amplify the production of intracellular radical oxidative species (ROS) via auto-oxidation and Fenton-like reactions through exhausting GSH. By drastically heightening cellular oxidative stress, CuHPT exhibits selective and potent cytotoxicity to multiple drug-resistant cancer cells. Importantly, CuHPT effectively inhibits in vivo drug-resistant tumor growth and doubles the survival time of tumor-bearing mice. Thus, along with CuHPT's good biocompatibility, our biochemical, cell biological, preclinical animal model data provide compelling evidence supporting the notion that this copper-based MOF is a predesigned smart therapeutic against drug-resistant cancers through precisely deconstructing their redox homeostasis.

An engineered abcb4 expression model reveals the central role of NF-κB in the regulation of drug resistance in zebrafish

Multi-drug resistance (MDR) is a phenomenon that tumor cells are exposed to a chemotherapeutic drug for a long time and then develop resistance to a variety of other anticancer drugs with different structures and different mechanisms. The in vitro studies of tumor cell lines cannot systematically reflect the role of MDR gene in vivo, and the cost of in vivo studies of transgenic mice as animal models is high. Given the myriad merits of zebrafish relative to other animal models, we aimed to establish a screening system using zebrafish stably expressing ATP-binding cassette (ATP-cassette) superfamily transporters and unveil the potential regulatory mechanism. We first used the Tol2-mediated approach to construct a Tg (abcb4:EGFP) transgenic zebrafish line with ATP-binding cassette (ABC) subfamily B member 4 (abcb4) gene promoter to drive EGFP expression. The expression levels of abcb4 and EGFP were significantly increased when Tg(abcb4:EGFP) transgenic zebrafish embryos were exposed to doxorubicin (DOX) or vincristine (VCR), and the increases were accompanied by a marked decreased accumulation of rhodamine B (RhB) in embryos, indicating a remarkable increase in DOX or VCR efflux. Mechanistically, Akt and Erk signalings were activated upon the treatment with DOX or VCR. With the application of Akt and Erk inhibitors, drug resistance was reversed with differing responsive effects. Notably, downstream NF-κB played a central role in the regulation of abcb4-mediated drug resistance. Taken together, the data indicate that the engineered Tg(abcb4:EGFP) transgenic zebrafish model is a new platform for screening drug resistance in vivo, which may facilitate and accelerate the process of drug development.

Alisertib shows negligible potential for perpetrating pharmacokinetic drug-drug interactions on ABCB1, ABCG2 and cytochromes P450, but acts as dual-activity resistance modulator through the inhibition of ABCC1 transporter

Alisertib (MLN8237), a novel Aurora A kinase inhibitor, is currently being clinically tested in late-phase trials for the therapy of various malignancies. In the present work, we describe alisertib's potential to perpetrate pharmacokinetic drug-drug interactions (DDIs) and/or to act as an antagonist of multidrug resistance (MDR). In accumulation assays, alisertib potently inhibited ABCC1 transporter, but not ABCB1 or ABCG2. The results of molecular modeling suggested a bifunctional mechanism for interaction on ABCC1. In addition, alisertib was characterized as a low- to moderate-affinity inhibitor of recombinant CYP3A4, CYP2C8, CYP2C9, CYP2C19, and CYP2D6 isoenzymes, but without potential clinical relevance. Drug combination studies revealed the capability of alisertib to synergistically antagonize ABCC1-mediated resistance to daunorubicin. Although alisertib exhibited substrate characteristics toward ABCB1 transporter in monolayer transport assays, comparative proliferation studies showed lack of its MDR-victim behavior in cells overexpressing ABCB1 as well as ABCG2 and ABCC1. Lastly, alisertib did not affect the expression of ABCC1, ABCG2, ABCB1 transporters and CYP1A2, CYP3A4, CYP2B6 isozymes on mRNA level in various systemic and tumoral models. In conclusion, our study suggests that alisertib is a drug candidate with negligible potential for perpetrating systemic pharmacokinetic DDIs on ABCB1, ABCG2 and cytochromes P450. In addition, we introduce alisertib as an effective dual-activity chemosensitizer whose MDR-antagonistic capacities are not impaired by efflux or effect on MDR phenotype. Our in vitro findings provide important pieces of information for clinicians when introducing alisertib into the clinical area.

Binding mode analysis of ABCA7 for the prediction of novel Alzheimer's disease therapeutics

The adenosine-triphosphate-(ATP)-binding cassette (ABC) transporter ABCA7 is a genetic risk factor for Alzheimer's disease (AD). Defective ABCA7 promotes AD development and/or progression. Unfortunately, ABCA7 belongs to the group of 'under-studied' ABC transporters that cannot be addressed by small-molecules. However, such small-molecules would allow for the exploration of ABCA7 as pharmacological target for the development of new AD diagnostics and therapeutics. Pan-ABC transporter modulators inherit the potential to explore under-studied ABC transporters as novel pharmacological targets by potentially binding to the proposed 'multitarget binding site'. Using the recently reported cryogenic-electron microscopy (cryo-EM) structures of ABCA1 and ABCA4, a homology model of ABCA7 has been generated. A set of novel, diverse, and potent pan-ABC transporter inhibitors has been docked to this ABCA7 homology model for the discovery of the multitarget binding site. Subsequently, application of pharmacophore modelling identified the essential pharmacophore features of these compounds that may support the rational drug design of innovative diagnostics and therapeutics against AD.

Nanodesigning of multifunctional quantum dots and nanoparticles for the treatment of fibrosarcoma

AIM

An effective, dual drug(DD) loaded nanocarrier system (nano particle(NP), quantum dots(QDs)) having two active substances was aimed to develop for the treatment of fibrosarcoma.

METHODS

Zinc oxide(ZnO) QDs were produced using zinc acetate dehydrate as a precursor, were incorporated with chitosan(Ch), and finally decorated with PEG-linked folic acid and were found to be effective after imatinib mesylate(IM) and dexketoprofen trometamol(DT) were loaded. Characterizations, invitro drug releases, cell toxicities, penetrations through cell lines and in-vivo animal tests of the prepared nanosystems were performed.

RESULTS

The size of hybrid nanoparticles were 168.6 ± 48.8nm, surface charge was -35.8 ± 0.26mV. The encapsulation efficiency was 75% for IM and 99% for DT. DD-functionalized QDChNPs and lyophilized functionalized QDChNPs in capsules slowed down tumor growth by up to 76.5 % and 88.7 %.

CONCLUSIONS

Our results demonstrate that developed hybrid nanoparticles are highly effective. This hybrid system gathers many of the advantages of nanotechnology into one form.

New Therapeutic Strategy for Overcoming Multidrug Resistance in Cancer Cells with Pyrazolo[3,4-d]pyrimidine Tyrosine Kinase Inhibitors

Simple Summary

P-glycoprotein (P-gp) is an ATP-binding cassette transporter whose overexpression in cancer cells is one of the main causes of multidrug resistance (MDR). Tyrosine kinase inhibitors (TKIs) have been reported to interact with ABC transporters and in some cases, increase the susceptibility of cancer cells to chemotherapy. We investigated the potential of novel TKI pyrazolo[3,4-d] pyrimidines and their prodrugs to inhibit P-gp in two MDR cancer cell lines with P-gp overexpression. The tested compounds were able to suppress P-gp by inhibiting its ATPase activity. Interestingly, prodrugs displayed a stronger potential to modulate P-gp and showed higher interaction energies in the docking simulations compared to their parent drugs. Furthermore, prodrugs showed significant potential to inhibit P-gp activity even in prolonged treatment and therefore to enhance the efficacy of doxorubicin and paclitaxel in MDR cancer cells. All of these characteristics imply that the new TKIs could be considered a valuable strategy for combating resistant cancers, especially in combination with other chemotherapeutics.

Abstract

Tyrosine kinase inhibitors (TKIs) often interact with the multidrug resistant (MDR) phenotype of cancer cells. In some cases, TKIs increase the susceptibility of MDR cancer cells to chemotherapy. As the overexpression of membrane transporter P-glycoprotein (P-gp) is the most common alteration in MDR cancer cells, we investigated the effects of TKI pyrazolo[3,4-d]pyrimidines on P-gp inhibition in two cellular models comprising sensitive and corresponding MDR cancer cells (human non-small cell lung carcinoma and colorectal adenocarcinoma). Tested TKIs showed collateral sensitivity by inducing stronger inhibition of MDR cancer cell line viability. Moreover, TKIs directly interacted with P-gp and inhibited its ATPase activity. Their potential P-gp binding site was proposed by molecular docking simulations. TKIs reversed resistance to doxorubicin and paclitaxel in a concentration-dependent manner. The expression studies excluded the indirect effect of TKIs on P-gp through regulation of its expression. A kinetics study showed that TKIs decreased P-gp activity and this effect was sustained for seven days in both MDR models. Therefore, pyrazolo[3,4-d]pyrimidines with potential for reversing P-gp-mediated MDR even in prolonged treatments can be considered a new therapeutic strategy for overcoming cancer MDR.

Synthesis and biological evaluation of novel quinoline analogs of ketoprofen as multidrug resistance protein 2 (MRP2) inhibitors

Objectives

A new series of quinoline analogs of ketoprofen was designed and synthesized as multidrug resistance protein 2 (MRP2) inhibitors using ketoprofen as the lead compounds.

Materials and Methods

The cytotoxic activity of the compounds was evaluated againt two cancer cell lines including A2780/RCIS (MRP2-overexpressing ovarian carcinoma), A2780, drug-sensitive ovarian carcinoma using MTT assay. Compounds showing low toxicity in MTT test were selected to investigate their MRP inhibition activity. MRP2 inhibitory potency was evaluated by determination of the uptake amount of fluorescent 5-carboxy fluorescein diacetate (5-CFDA) substrate, by A2780/RCIS in the presence of the selected compounds. Mode of interaction between synthesized ligands and homology modeled MRP2 was investigated by MOE software.

Results

Compound 6d, a 4-carboxy quinoline possessing dimethoxy phenyl in position 2 of quinoline ring, showed the most MRP2 inhibition activity among all the quinolines and more than the reference drug ketoprofen. MRP2 inhibition activity of compound 7d was less in comparison to that of compound 6d, indicating that carboxyl group in position 4 of quinoline may interact with MRP2. Docking studies showed that compound 7d methyl ester of 6d, interacted less compared to its parent 6d, which is consistent with biological results.

Conclusion

This study indicates that 6- or 8-benzoyl-2-arylquinoline is a suitable scaffold to design MRP2 inhibitors. The position of benzoyl in quinoline ring is important in inhibition of MRP2. Generally, MRP2 inhibition activity of compound 7d was less in comparison to that of 6d, indicating that carboxyl group in position 4 of quinoline may interact with MRP2.

Hype or hope - Can combination therapies with third-generation EGFR-TKIs help overcome acquired resistance and improve outcomes in EGFR-mutant advanced/metastatic NSCLC?

Three generations of epidermal growth factor receptor - tyrosine kinase inhibitors (EGFR-TKIs) have been developed for treating advanced/metastatic non-small cell lung cancer (NSCLC) patients harboring EGFR-activating mutations, while a fourth generation is undergoing preclinical assessment. Although initially effective, acquired resistance to EGFR-TKIs usually arises within a year due to the emergence of clones harboring multiple resistance mechanisms. Therefore, the combination of EGFR-TKIs with other therapeutic agents has emerged as a potential strategy to overcome resistance and improve clinical outcomes. However, results obtained so far are ambiguous and ideal therapies for patients who experience disease progression during treatment with EGFR-TKIs remain elusive. This review provides an updated landscape of EGFR-TKIs, along with a description of the mechanisms causing resistance to these drugs. Moreover, it discusses the current knowledge, limitations, and future perspective regarding the use of EGFR-TKIs in combination with other anticancer agents, supporting the need for bench-to-bedside approaches in selected populations.

The Cytotoxicity of Doxorubicin Can Be Accelerated by a Combination of Hyperthermia and 5-Aminolevulinic Acid

Chemotherapy is cytotoxic to various cancer cells and as well as normal cells. Thus, treatments that demonstrate selective cytotoxicity for cancer cells are desired. The combination of chemotherapy and other cancer therapies can show synergic cytotoxicity, which may be a clue to the nature of the involved cancer cellar-specific damage. We previously reported a phenomenon whereby mitochondrial reactive oxygen species (mitROS) regulate the expression transporters involved in anticancer drug transport and mitROS production is increased by hyperthermia. Moreover, the uptake of 5-aminolevulinic acid (ALA) was enhanced by the increase in mitROS production. In this study, we investigated whether the combination of hyperthermia and ALA can enhance the cytotoxicity of doxorubicin. MitROS production and ALA-derived porphyrin accumulation by hyperthermia (HT) were increased in a murine breast cancer cell line. The expression of solute carrier 15A1 (SLC15A1) upregulated and an ATP-binding cassette subfamily G member 2 (ABCG2) downregulated by HT. Since SLC15A1 is an accumulating transporter for ALA, while ABCG2 is a porphyrin efflux transporter, porphyrin accumulation was enhanced. ABCG2 is also a doxorubicin efflux transporter. Thus, ALA treatment accelerates the intracellular concentration of porphyrin, which acts as a competitive inhibitor of doxorubicin. Indeed, the amount of intracellular doxorubicin was increased by a combination of HT and ALA. The cytotoxicity of doxorubicin was also enhanced. This enhancement was observed in the human breast cancer cell line while it was not seen in normal cells. The combination of HT and ALA treatment can enhance the cancer-specific cytotoxicity of doxorubicin.

Resistance to Tyrosine Kinase Inhibitors in Chronic Myeloid Leukemia-From Molecular Mechanisms to Clinical Relevance

Simple Summary

Chronic myeloid leukemia (CML) is a myeloproliferative neoplasia associated with a molecular alteration, the fusion gene BCR-ABL1, that encodes the tyrosine kinase oncoprotein BCR-ABL1. This led to the development of tyrosine kinase inhibitors (TKI), with Imatinib being the first TKI approved. Although the vast majority of CML patients respond to Imatinib, resistance to this targeted therapy contributes to therapeutic failure and relapse. Here we review the molecular mechanisms and other factors (e.g., patient adherence) involved in TKI resistance, the methodologies to access these mechanisms, and the possible therapeutic approaches to circumvent TKI resistance in CML.

Abstract

Resistance to targeted therapies is a complex and multifactorial process that culminates in the selection of a cancer clone with the ability to evade treatment. Chronic myeloid leukemia (CML) was the first malignancy recognized to be associated with a genetic alteration, the t(9;22)(q34;q11). This translocation originates the BCR-ABL1 fusion gene, encoding the cytoplasmic chimeric BCR-ABL1 protein that displays an abnormally high tyrosine kinase activity. Although the vast majority of patients with CML respond to Imatinib, a tyrosine kinase inhibitor (TKI), resistance might occur either de novo or during treatment. In CML, the TKI resistance mechanisms are usually subdivided into BCR-ABL1-dependent and independent mechanisms. Furthermore, patients’ compliance/adherence to therapy is critical to CML management. Techniques with enhanced sensitivity like NGS and dPCR, the use of artificial intelligence (AI) techniques, and the development of mathematical modeling and computational prediction methods could reveal the underlying mechanisms of drug resistance and facilitate the design of more effective treatment strategies for improving drug efficacy in CML patients. Here we review the molecular mechanisms and other factors involved in resistance to TKIs in CML and the new methodologies to access these mechanisms, and the therapeutic approaches to circumvent TKI resistance.

Nrf2 signaling promotes cancer stemness, migration, and expression of ABC transporter genes in sorafenib-resistant hepatocellular carcinoma cells

Background and aim

As a multiple tyrosine kinase inhibitor, sorafenib is widely used to treat hepatocellular carcinoma (HCC), but patients frequently face resistance problems. Because the mechanism controlling sorafenib-resistance is not well understood, this study focused on the connection between tumor characteristics and the Nrf2 signaling pathway in a sorafenib-resistant HCC cell line.

Methods

A sorafenib-resistant HCC cell line (Huh7) was developed by increasing the dose of sorafenib in the culture medium until the target concentration was reached. Cell morphology, migration/invasion rates, and expression of stemness-related and ATP-binding cassette (ABC) transporter genes were compared between sorafenib-resistant Huh7 cells and parental Huh7 cells. Next, a small interfering RNA was used to knock down Nrf2 expression in sorafenib-resistant Huh7 cells, after which cell viability, stemness, migration, and ABC transporter gene expression were examined again.

Results

Proliferation, migration, and invasion rates of sorafenib-resistant Huh7 cells were significantly increased relative to the parental cells with or without sorafenib added to the medium. The expression levels of stemness markers and ABC transporter genes were up-regulated in sorafenib-resistant cells. After Nrf2 was knocked down in sorafenib-resistant cells, cell migration and invasion rates were reduced, and expression levels of stemness markers and ABC transporter genes were reduced.

Conclusion

Nrf2 signaling promotes cancer stemness, migration, and expression of ABC transporter genes in sorafenib-resistant HCC cells.

Rutaecarpine Increases Anticancer Drug Sensitivity in Drug-Resistant Cells through MARCH8-Dependent ABCB1 Degradation

The overexpression of adenosine triphosphate (ATP)-binding cassette (ABC) subfamily B member 1 (ABCB1; P-glycoprotein; MDR1) in some types of cancer cells is one of the mechanisms responsible for the development of multidrug resistance (MDR), which leads to the failure of chemotherapy. Therefore, it is important to inhibit the activity or reduce the expression level of ABCB1 to maintain an effective intracellular level of chemotherapeutic drugs. In this study, we found that rutaecarpine, a bioactive alkaloid isolated from Evodia Rutaecarpa, has the capacity to reverse ABCB1-mediated MDR. Our data indicated that the reversal effect of rutaecarpine was related to the attenuation of the protein level of ABCB1. Mechanistically, we demonstrated that ABCB1 is a newly discovered substrate of E3 ubiquitin ligase membrane-associated RING-CH 8 (MARCH8). MARCH8 can interact with ABCB1 and promote its ubiquitination and degradation. In short, rutaecarpine increased the degradation of ABCB1 protein by upregulating the protein level of MARCH8, thereby antagonizing ABCB1-mediated MDR. Notably, the treatment of rutaecarpine combined with other anticancer drugs exhibits a therapeutic effect on transplanted tumors. Therefore, our study provides a potential chemotherapeutic strategy of co-administrating rutaecarpine with other conventional chemotherapeutic agents to overcome MDR and improve therapeutic effect.

Small molecule kinase inhibitors enhance aminolevulinic acid-mediated protoporphyrin IX fluorescence and PDT response in triple negative breast cancer cell lines

SIGNIFICANCE

We demonstrate that clinically used kinase inhibitors such as lapatinib can be used for enhancing aminolevulinic acid (ALA) for tumor fluorescence imaging and photodynamic therapy (PDT).

AIM

ALA is used as a prodrug for protoporphyrin IX (PpIX) fluorescence-guided tumor resection and PDT. Our previous studies indicate that tumors with high ABCG2 activity exhibit low PpIX fluorescence, which hampers the application of ALA. We aim to determine whether clinically used ABCG2-interacting kinase inhibitors increase ALA-PpIX fluorescence and PDT.

APPROACH

PpIX fluorescence was determined by spectrofluorometry, flow cytometry, and confocal microscopy after ALA alone or in combination with kinase inhibitors in triple negative breast cancer (TNBC) cell lines. Cytotoxicity was examined after ALA-PDT alone or in combination with kinase inhibitors. Effect of single and combination treatments on apoptosis was assessed by Western blot.

RESULTS

Four kinase inhibitors (lapatinib, PD169316, sunitinib, gefitinib) significantly increased ALA-PpIX fluorescence and PDT response in TNBC cells with ABCG2 activity, but not in MCF10A nontumor breast epithelial cell line without ABCG2 activity. Confocal microscopic imaging showed that PpIX fluorescence was weak and diffuse after ALA alone, which was greatly enhanced by kinase inhibitors, particularly in the mitochondria. Lapatinib was the only inhibitor that significantly reduced PpIX efflux in cell culture medium and showed stronger enhancement of PDT response than other kinase inhibitors. Lapatinib, in combination with ALA, induced tumor cells to undergo apoptosis, whereas no apoptosis was detected after each individual treatment.

CONCLUSIONS

Although all four kinase inhibitors were able to enhance ALA-PpIX fluorescence and PDT, lapatinib exhibited the strongest enhancement effect. As an FDA-approved kinase inhibitor for breast cancer treatment, lapatinib is ready to be used in combination with ALA for therapeutic enhancement in tumors with elevated ABCG2 activity. This rational combination approach warrants further investigation in tumor models.

The Second-Generation PIM Kinase Inhibitor TP-3654 Resensitizes ABCG2-Overexpressing Multidrug-Resistant Cancer Cells to Cytotoxic Anticancer Drugs

Human ATP-binding cassette (ABC) subfamily G member 2 (ABCG2) mediates the transport of a wide variety of conventional cytotoxic anticancer drugs and molecular targeted agents. Consequently, the overexpression of ABCG2 in cancer cells is linked to the development of the multidrug resistance (MDR) phenotype. TP-3654 is an experimental second-generation inhibitor of PIM kinase that is currently under investigation in clinical trials to treat advanced solid tumors and myelofibrosis. In this study, we discovered that by attenuating the drug transport function of ABCG2, TP-3654 resensitizes ABCG2-overexpressing multidrug-resistant cancer cells to cytotoxic ABCG2 substrate drugs topotecan, SN-38 and mitoxantrone. Moreover, our results indicate that ABCG2 does not mediate resistance to TP-3654 and may not play a major role in the induction of resistance to TP-3654 in cancer patients. Taken together, our findings reveal that TP-3654 is a selective, potent modulator of ABCG2 drug efflux function that may offer an additional combination therapy option for the treatment of multidrug-resistant cancers.

Genetic Heterogeneity, Therapeutic Hurdle Confronting Sorafenib and Immune Checkpoint Inhibitors in Hepatocellular Carcinoma

Despite the latest advances in hepatocellular carcinoma (HCC) screening and treatment modalities, HCC is still representing a global burden. Most HCC patients present at later stages to an extent that conventional curative options are ineffective. Hence, systemic therapy represented by the tyrosine kinase inhibitor, sorafenib, in the first-line setting is the main treatment modality for advanced-stage HCC. However, in the two groundbreaking phase III clinical trials, the SHARP and Asia-Pacific trials, sorafenib has demonstrated a modest prolongation of overall survival in almost 30% of HCC patients. As HCC develops in an immune-rich milieu, particular attention has been placed on immune checkpoint inhibitors (ICIs) as a novel therapeutic modality for HCC. Yet, HCC therapy is hampered by the resistance to chemotherapeutic drugs and the subsequent tumor recurrence. HCC is characterized by substantial genomic heterogeneity that has an impact on cellular response to the applied therapy. And hence, this review aims at giving an insight into the therapeutic impact and the different mechanisms of resistance to sorafenib and ICIs as well as, discussing the genomic heterogeneity associated with such mechanisms.

MYC: a multipurpose oncogene with prognostic and therapeutic implications in blood malignancies

MYC oncogene is a transcription factor with a wide array of functions affecting cellular activities such as cell cycle, apoptosis, DNA damage response, and hematopoiesis. Due to the multi-functionality of MYC, its expression is regulated at multiple levels. Deregulation of this oncogene can give rise to a variety of cancers. In this review, MYC regulation and the mechanisms by which MYC adjusts cellular functions and its implication in hematologic malignancies are summarized. Further, we also discuss potential inhibitors of MYC that could be beneficial for treating hematologic malignancies.

New frontiers against sorafenib resistance in renal cell carcinoma: From molecular mechanisms to predictive biomarkers

Renal cell carcinoma (RCC) is a highly vascularized tumor and prone to distant metastasis. Sorafenib is the first targeted multikinase inhibitor and first-line chemical drug approved for RCC therapy. In fact, only a small number of RCC patients benefit significantly from sorafenib treatment, while the growing prevalence of sorafenib resistance has become a major obstacle for drug therapy effectivity of sorafenib. The molecular mechanisms of sorafenib resistance in RCC are not completely understood by now. Herein, we comprehensively summarize the underlying mechanisms of sorafenib resistance and molecular biomarkers for predicting sorafenib responsiveness. Moreover, we outline strategies suitable for overcoming sorafenib resistance and prospect potential approaches for identifying biomarkers associated with sorafenib resistance in RCC, which contributes to guide individualized and precision drug therapy.

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

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

Pharmacogenomics of Impaired Tyrosine Kinase Inhibitor Response: Lessons Learned From Chronic Myelogenous Leukemia

The use of small molecules became one key cornerstone of targeted anti-cancer therapy. Among them, tyrosine kinase inhibitors (TKIs) are especially important, as they were the first molecules to proof the concept of targeted anti-cancer treatment. Since 2001, TKIs can be successfully used to treat chronic myelogenous leukemia (CML). CML is a hematologic neoplasm, predominantly caused by reciprocal translocation t(9;22)(q34;q11) leading to formation of the so-called BCR-ABL1 fusion gene. By binding to the BCR-ABL1 kinase and inhibition of downstream target phosphorylation, TKIs, such as imatinib or nilotinib, can be used as single agents to treat CML patients resulting in 80 % 10-year survival rates. However, treatment failure can be observed in 20-25 % of CML patients occurring either dependent or independent from the BCR-ABL1 kinase. Here, we review approved TKIs that are indicated for the treatment of CML, their side effects and limitations. We point out mechanisms of TKI resistance focusing either on BCR-ABL1-dependent mechanisms by summarizing the clinically observed BCR-ABL1-mutations and their implications on TKI binding, as well as on BCR-ABL1-independent mechanisms of resistances. For the latter, we discuss potential mechanisms, among them cytochrome P450 implications, drug efflux transporter variants and expression, microRNA deregulation, as well as the role of alternative signaling pathways. Further, we give insights on how TKI resistance could be analyzed and what could be learned from studying TKI resistance in CML in vitro.

CASK Silence Overcomes Sorafenib Resistance of Hepatocellular Carcinoma Through Activating Apoptosis and Autophagic Cell Death

Hepatocellular carcinoma (HCC) patients usually fail to be treated because of drug resistance, including sorafenib. In this study, the effects of CASK in HCC were investigated using gain- or loss-of-function strategies by performing cell counting kit-8 assay, colony formation assay, flow cytometry, transmission electron microscopy, immunofluorescent confocal laser microscopy, tumor xenograft experiment and immunohistochemistry staining. The current results suggested that CASK expression was positively associated with sorafenib resistance and poor prognosis of HCC. Moreover, inhibition of CASK increased the role of sorafenib partially by promoting apoptosis and autophagy, while CASK overexpression presented the opposite effects. Besides, when treatment with sorafenib, inhibition of apoptosis using the pan-caspase inhibitor Z-VAD-FMK and inhibition of autophagy using autophagy inhibitor 3-Methyladenine (3-MA) or small interfering RNA (siRNA) of LC3B all significantly reversed CASK knockout-induced effects, suggesting that both apoptosis and autophagy were involved in CASK-mediated above functions and autophagy played a pro-death role in this research. Intriguingly, similar results were observed in vivo. In molecular level, CASK knockout activated the c-Jun N-terminal kinase (JNK) pathway, and treatment with JNK inhibitor SP600125 or transiently transfected with siRNA targeting JNK significantly attenuated CASK knockout-mediated autophagic cell death. Collectively, all these results together indicated that CASK might be a promising biomarker and a potential therapeutic target for HCC patients.

Lapatinib enhances paclitaxel toxicity in MCF-7, T47D, and MDA-MB-321 breast cancer cells

Paclitaxel (PTX) is used to treat breast cancer both as a monotherapy and in combination with other anticancer drugs. Chemoresistance is one of the main reasons for the failure of breast cancer treatment. Mechanisms which contribute to multidrug resistance of breast cancer cells to PTX include the active removal of the drug from the cell related to the increased activity of ABC family membrane transporters. Lapatinib (LAP) has been approved by the FDA in combination with other anticancer agents for the treatment of HER2-positive breast cancer. LAP can reverse chemoresistance by interaction with ABC transporters. Therefore the aim of the study was to investigate whether LAP is able to potentiate PTX toxicity in MCF-7, T47D, and MDA-MB-321 breast cancer cells which do not express the HER-2. It was found that LAP inhibited the PTX efflux, increased its intracellular concentration and thus significantly increased the anticancer activity of PTX. The combination of PTX and LAP can be useful in HER2-negative breast cancer treatment.

Polymerized vorinostat mediated photodynamic therapy using lysosomal spatiotemporal synchronized drug release complex

A combination of photodynamic therapy (PDT) and histone deacetylase inhibitor (HDACis) could potentiate single-mode anti-tumor activity of HDACis or PDT to inhibit tumor relapse and metastasis. However, poor solubility and heterogeneity in cellular uptake and tissue distribution hamper the dual mode antitumor effect. For a controlled drug release of photosensitizers and HDACis in cytoplasm, photosensitizer pyropheophorbide-a (Pyro) encapsulated in polymer polyethylene glycol-b-poly (asparaginyl-vorinostat) (simplified as Pyro@FPPS) are fabricated to achieve their lysosomal spatiotemporal synchronized release. With HDACis modeling PDT in vitro and in vivo, it seems that polymerized Vorinostat encapsulated photosensitizers significantly inhibited the tumor proliferation and metastasis by spatiotemporal synchronized drugs release, and Pyro@FPPS reported here reveals a promising prospect to exert drugs' synergistic effect in a spatiotemporal synchronized manner and can be an effective strategy to inhibit tumor growth, recurrence and metastasis in clinic.

Unique indolizidine alkaloid securinine is a promising scaffold for the development of neuroprotective and antitumor drugs

Alkaloids, secondary plant metabolites, are used in traditional medicine in many countries to treat various pathological conditions. Securinine, a unique indolizidine alkaloid combining four cycles, "6-azobicyclo[3.2.1]octane" as a key structure fused with α,β-unsaturated-γ-lactone and piperidine ring, has a broad spectrum of actions including anti-inflammatory, antibacterial, neuroprotective and antitumor, and has been previously used in medical practice. It has several reactive centers, which are double bonds at positions 12-13 and 14-15, and this is a challenging scaffold for the synthesis of biologically active compounds. In this review, works on the production of modified securinine derivatives and their biological activity are addressed. Both monovalent and bivalent derivatives that are most promising in our opinion, and have potential for further research, are considered.

Structure-Based Discovery of Pyrimidine Aminobenzene Derivatives as Potent Oral Reversal Agents against P-gp- and BCRP-Mediated Multidrug Resistance

Overexpression of ATP binding cassette (ABC) transporters, including P-glycoprotein (P-gp) and breast cancer resistance protein (BCRP), is an important factor leading to multidrug resistance (MDR) in cancer treatments. Three subclasses of dual inhibitors of P-gp and BCRP were designed based on the active moieties of BCRP inhibitors, tyrosine kinase inhibitors, and P-gp inhibitors, of which compound 21 possessed low cytotoxicity, high reversal potency, and good lipid distribution coefficient. 21 also increased the accumulation of Adriamycin (ADM) and Mitoxantrone (MX), blocked Rh123 efflux, and made no change in the protein expression of P-gp and BCRP. Importantly, coadministration of 21 can significantly improve the oral bioavailability of paclitaxel (PTX). It was also demonstrated that 21 significantly inhibited the growth of K562/A02 xenograft tumors by increasing the sensitivity of ADM in vivo. In summary, 21 has the potential to overcome MDR caused by P-gp and BCRP and to improve the oral bioavailability of PTX.

Combination of HGF/MET-targeting agents and other therapeutic strategies in cancer

MET receptor has emerged as a druggable target across several human cancers. Agents targeting MET and its ligand hepatocyte growth factor (HGF) including small molecules such as crizotinib, tivantinib and cabozantinib or antibodies including rilotumumab and onartuzumab have proven their values in different tumors. Recently, capmatinib was approved for treatment of metastatic lung cancer with MET exon 14 skipping. In this review, we critically examine the current evidence on how HGF/MET combination therapies may take advantage of synergistic effects, overcome primary or acquired drug resistance, target tumor microenvironment, modulate drug metabolism or tackle pharmacokinetic issues. Preclinical and clinical studies on the combination of HGF/MET-targeted agents with conventional chemotherapeutics or molecularly targeted treatments (including EGFR, VEGFR, HER2, RAF/MEK, and PI3K/Akt targeting agents) and also the value of biomarkers are examined. Our deeper understanding of molecular mechanisms underlying successful pharmacological combinations is crucial to find the best personalized treatment regimens for cancer patients.

Dihydro-β-agarofuran-Type Sesquiterpenoids from the Seeds of Celastrus virens and Their Multidrug Resistance Reversal Activity against the KB/VCR Cell Line

Twenty-nine dihydro-β-agarofuran-type sesquiterpenoids, including 17 new and 12 known compounds, were obtained from the seeds of Celastrus virens. The structures of the new isolates were characterized by spectroscopic methods and X-ray diffraction analysis. Among these, 20 sesquiterpenoids were evaluated for their multidrug resistance (MDR) reversal activity against the KB/VCR cell line. As a result, compounds 6 and 8 were found to exhibit MDR-reversal activity of more than 10-fold at a concentration of 2 μM, and the reversal fold (RF) ratios of compounds 19, 21, and 24 were >97.9 at a 20 μM nontoxic concentration level.

Long Non-coding RNAs in Cisplatin Resistance in Osteosarcoma

OPINION STATEMENT

Osteosarcoma (OS), the most common primary malignant bone tumor, is a vastly aggressive disease in children and adolescents. Although dramatic progress in therapeutic strategies have achieved over the past several decades, the outcome remains poor for most patients with metastatic or recurrent OS. Nowadays, conventional treatment for OS patients is surgery combined with multidrug chemotherapy including doxorubicin, methotrexate, and cisplatin (CDDP). In this sense, cisplatin (CDDP) is one of the most drugs used in the treatment of OS but drug resistance to CDDP appears as a serious problem in the use of this drug in the treatment of OS. Thus, we consider that the understanding the molecular mechanisms and the genes involved that lead to CDDP resistance is essential to developing more effective treatments against OS. In this review, we present an outline of the key role of the long non-coding RNAs (lncRNAs) in CDDP resistance in OS. This overview is expected to contribute to understand the mechanisms of CDDP resistance in OS and the relationship of the expression regulation of several lncRNAs.

ABC transporter superfamily. An updated overview, relevance in cancer multidrug resistance and perspectives with personalized medicine

The ATP binding-cassette superfamily corresponds the mostly transmembrane transporters family found in humans. These proteins actively transport endogenous and exogenous substrates through biological membranes in body tissues, so they have an important role in the regulation of many physiological functions necessary for human homeostasis, as well as in response regulation to several pharmacological substrates. The development of multidrug resistance has become one of the main troubles in conventional chemotherapy in different illnesses including cancer, being the increased efflux of antineoplastic drugs the main reason for this multidrug resistance, with a key role of the ABC superfamily. Likely, the interindividual variability in the pharmacological response among patients is well known, and may be due to intrinsically factors of the disease, genetic and environmental ones. Thus, the understanding of this variability, especially the genetic variability associated with the efficacy and toxicity of drugs, can provide a safer and more effective pharmacological treatment, so ABC genes are considered as important regulators due to their relationship with the reduction in pharmacological response. In this review, updated information about transporters belonging to this superfamily was collected, the possible role of these transporters in cancer, the role of genetic variability in their genes, as well as some therapeutic tools that have been tried to raise against main transporters associated with chemoresistance in cancer.

Anlotinib suppresses metastasis and multidrug resistance via dual blockade of MET/ABCB1 in colorectal carcinoma cells

Anlotinib, a highly selective multi-targeted tyrosine kinase inhibitor (TKI) has therapeutic effects on non-small-cell lung cancer (NSCLC). In this study, the anti-tumor activity and molecular mechanism of anlotinib in metastatic colorectal cancer (mCRC) was explored. The anti-angiogenesis, anti-metastasis, anti-proliferative, and anti-multidrug resistance efficacy of anlotinib were analyzed by using in vitro and in vivo models of human CRC cells. The results indicated that anlotinib boosted chemo-sensitivity of CRC cells, and restrained its proliferation. Besides the suppression of the MET signaling pathway, anlotinib also inhibited invasion and migration of CRC cells. Furthermore, anlotinib prevented VEGF-induced angiogenesis, N-cadherin (CDH2)-induced cell migration, and reversed ATP-binding cassette subfamily B member 1 (ABCB1) -mediated CRC multidrug resistance in CRC. The CRC liver metastasis and subcutaneously implanted xenograft model testified that anlotinib could inhibit proliferation and liver metastasis in CRC cells. Such an observation suggested that a combination of anlotinib with anti-cancer drugs could attenuate angiogenesis, metastasis, proliferative, and multidrug resistance, which constitutes a novel treatment strategy for CRC patients with metastasis.

OTS964, a TOPK Inhibitor, Is Susceptible to ABCG2-Mediated Drug Resistance

OTS964 is a potent T-LAK cell-originated protein kinase (TOPK) inhibitor. Herein, we investigated the interaction of OTS964 and multidrug resistance (MDR)-associated ATP-binding cassette sub-family G member 2 (ABCG2). The cell viability assay indicated that the effect of OTS964 is limited in cancer drug-resistant and transfected cells overexpressing ABCG2. We found that the known ABCG2 transporter inhibitor has the ability to sensitize ABCG2-overexpressing cells to OTS964. In mechanism-based studies, OTS964 shows inhibitory effect on the efflux function mediated by ABCG2, and in turn, affects the pharmacokinetic profile of other ABCG2 substrate-drugs. Furthermore, OTS964 upregulates ABCG2 protein expression, resulting in enhanced resistance to ABCG2 substrate-drugs. The ATPase assay demonstrated that OTS964 stimulates ATPase activity of ABCG2 in a concentration-dependent manner. The computational molecular docking analysis combined with results from ATPase assay suggested that OTS964 interacts with drug-binding pocket of ABCG2 and has substrate-like behaviors. Thus, OTS964 is an MDR-susceptible agent due to its interactions with ABCG2, and overexpression of ABCG2 transporter may attenuate its therapeutic effect in cancer cells.

ABCA8-mediated efflux of taurocholic acid contributes to gemcitabine insensitivity in human pancreatic cancer via the S1PR2-ERK pathway

The development of resistance to anticancer drugs is believed to cause chemotherapy failure in pancreatic cancer (PC). The efflux of anticancer drugs mediated by ATP-binding cassette (ABC) transporters is a widely accepted mechanism for chemoresistance, but for ABCA subfamily members, which are characterized by their ability to transport lipids and cholesterol, its role in chemoresistance remains unknown. Here we found that the expression of ABCA8, a member of ABCA subfamily transporters, was significantly increased in human PC cells after gemcitabine (GEM) treatment, as well as in established GEM-resistant (Gem-R) PC cells. Importantly, ABCA8 knockdown reversed the chemoresistance phenotype of Gem-R cells, whereas ABCA8 overexpression significantly decreased the sensitivity of human PC cells to GEM, both in vitro and in vivo, demonstrating an important role of ABCA8 in regulating chemosensitivity. Moreover, our results showed that treatment with taurocholic acid (TCA), an endogenous substrate of ABCA8, also induced GEM insensitivity in PC cells. We further demonstrated that ABCA8 mediates the efflux of TCA out of PC cells, and that extracellular TCA activates extracellular signal-regulated kinase (ERK) signaling via the sphingosine 1-phosphate receptor 2 (S1PR2), which is responsible for ABCA8-induced GEM ineffectiveness. Together, these findings reveal a novel TCA-related mechanism of ABCA subfamily transporter-mediated chemoresistance that goes beyond the role of a drug pump and suggest ABCA8 or the TCA-S1RP2-ERK pathway as potential targets for improving the effectiveness of and overcoming the resistance to chemotherapy in PC.

Sirtuin 1 and 2 inhibitors enhance the inhibitory effect of sorafenib in hepatocellular carcinoma cells

Multidrug resistance (MDR) counteracts the efficiency of sorafenib, an important first-line therapy for hepatocellular carcinoma (HCC). Sirtuins (SIRTs) 1 and 2 are associated with tumor progression and MDR. We treated 2D and 3D cultures (which mimic the features of in vivo tumors) from HCC cells with sorafenib alone or in the presence of SIRTs 1 and 2 inhibitors (cambinol or EX-527; combined treatments). Cultures subjected to combined treatments showed a greater fall in cellular viability, proliferation (PCNA, cyclin D1 and Ki-67 expression and cell cycle analysis), migration and invasion when compared with cultures treated only with sorafenib. Similarly, combined treatments produced more apoptosis (annexin V/PI, caspase-3/7 activity) than sorafenib alone. Since cell cycle dysregulation and apoptotic blockage are reported mechanisms of MDR, the modulation found in PCNA, cyclin D1, Ki-67 and caspase-3/7 proteins by cambinol and EX-527 are probably playing a role in enhancing the sensitivity of HCC cell lines to sorafenib. EX-527 reduced MRP3 and BCRP expression in sorafenib-treated HCC cells. Since ABC transporters contribute to MDR, MRP3 and BCRP could be also influencing in the response of HCC cells to sorafenib. Overall, 2D and 3D cultures behave similarly except that 3D cultures were less sensitive to treatments, reinforcing the clinical relevance of the current study. Findings presented in this manuscript support a potential application for SIRTs 1 and 2 inhibitors since we demonstrated that these compounds enhance the inhibitory effect of sorafenib upon treatment of hepatocellular carcinoma cells lines.

Aberrant DNA Methylation of ABC Transporters in Cancer

ATP-binding cassette (ABC) transporters play a crucial role in multidrug resistance (MDR) of cancers. They function as efflux pumps, resulting in limited effectiveness or even failure of therapy. Increasing evidence suggests that ABC transporters are also involved in tumor initiation, progression, and metastasis. Tumors frequently show multiple genetic and epigenetic abnormalities, including changes in histone modification and DNA methylation. Alterations in the DNA methylation status of ABC transporters have been reported for a variety of cancer types. In this review, we outline the current knowledge of DNA methylation of ABC transporters in cancer. We give a brief introduction to structure, function, and gene regulation of ABC transporters that have already been investigated for their DNA methylation status in cancer. After giving an overview of the applied methodologies and the CpGs analyzed, we summarize and discuss the findings on aberrant DNA methylation of ABC transporters by cancer types. We conclude our review with the discussion of the potential to target aberrant DNA methylation of ABC transporters for cancer therapy.

Sapitinib Reverses Anticancer Drug Resistance in Colon Cancer Cells Overexpressing the ABCB1 Transporter

The efficacy of anti-cancer drugs in patients can be attenuated by the development of multi-drug resistance (MDR) due to ATP-binding cassette (ABC) transporters overexpression. In this in vitro study, we determined the reversal efficacy of the epidermal growth factor receptor (EFGR) inhibitor, saptinib, in SW620 and SW720/Ad300 colon cancer cells and HEK293/ABCB1 cells which overexpress the ABCB1 transporter. Sapitinib significantly increased the efficacy of paclitaxel and doxorubicin in ABCB1 overexpressing cells without altering the expression or the subcellular location of the ABCB1 transporter. Sapitinib significantly increased the accumulation of [³H]-paclitaxel in SW620/AD300 cells probably by stimulating ATPase activity which could competitively inhibit the uptake of [³H]-paclitaxel. Furthermore, sapitinib inhibited the growth of resistant multicellular tumor spheroids (MCTS). The docking study indicated that sapitinib interacted with the efflux site of ABCB1 transporter by π-π interaction and two hydrogen bonds. In conclusion, our study suggests that sapitinib surmounts MDR mediated by ABCB1 transporter in cancer cells.