Rociletinib (CO-1686) enhanced the efficacy of chemotherapeutic agents in ABCG2-overexpressing cancer cells in vitro and in vivo

In vitro models to evaluate multidrug resistance in cancer cells: Biochemical and morphological techniques and pharmacological strategies

The overexpression of ATP-binding cassette (ABC) transporters contributes to the failure of chemotherapies and symbolizes a great challenge in oncology, associated with the adaptation of tumor cells to anticancer drugs such that these transporters become less effective, a mechanism known as multidrug resistance (MDR). The aim of this review is to present the most widely used methodologies for induction and comprehension of in vitro models for detection of multidrug-resistant (MDR) modulators or inhibitors, including biochemical and morphological techniques for chemosensitivity studies. The overexpression of MDR proteins, predominantly, the subfamily glycoprotein-1 (P-gp or ABCB1) multidrug resistance, multidrug resistance-associated protein 1 (MRP1 or ABCCC1), multidrug resistance-associated protein 2 (MRP2 or ABCC2) and cancer resistance protein (ABCG2), in chemotherapy-exposed cancer lines have been established/investigated by several techniques. Amongst these techniques, the most used are (i) colorimetric/fluorescent indirect bioassays, (ii) rhodamine and efflux analysis, (iii) release of 3,30-diethyloxacarbocyanine iodide by fluorescence microscopy and flow cytometry to measure P-gp function and other ABC transporters, (iv) exclusion of calcein-acetoxymethylester, (v) ATPase assays to distinguish types of interaction with ABC transporters, (vi) morphology to detail phenotypic characteristics in transformed cells, (vii) molecular testing of resistance-related proteins (RT-qPCR) and (viii) 2D and 3D models, (ix) organoids, and (x) microfluidic technology. Then, in vitro models for detecting chemotherapy MDR cells to assess innovative therapies to modulate or inhibit tumor cell growth and overcome clinical resistance. It is noteworthy that different therapies including anti-miRNAs, antibody-drug conjugates (to natural products), and epigenetic modifications were also considered as promising alternatives, since currently no anti-MDR therapies are able to improve patient quality of life. Therefore, there is also urgency for new clinical markers of resistance to more reliably reflect in vivo effectiveness of novel antitumor drugs.

Epertinib counteracts multidrug resistance in cancer cells by antagonizing the drug efflux function of ABCB1 and ABCG2

A significant hurdle in cancer treatment arises from multidrug resistance (MDR), often due to overexpression of ATP-binding cassette (ABC) transporters like ABCB1 and/or ABCG2 in cancer cells. These transporters actively diminish the efficacy of cytotoxic drugs by facilitating ATP hydrolysis-dependent drug efflux and reducing intracellular drug accumulation in cancer cells. Addressing multidrug-resistant cancers poses a significant challenge due to the lack of approved treatments, prompting the exploration of alternative avenues like drug repurposing (also referred to as drug repositioning) of molecularly targeted agents to reverse MDR-mediated by ABCB1 and/or ABCG2 in multidrug-resistant cancer cells. Epertinib, a potent inhibitor of EGFR and HER2 currently in clinical trials for solid tumors, was investigated for its potential to resensitize ABCB1- and ABCG2-overexpressing multidrug-resistant cancer cells to chemotherapeutic agents. Our findings reveal that at sub-toxic, submicromolar concentrations, epertinib restores the sensitivity of multidrug-resistant cancer cells to cytotoxic drugs in a concentration-dependent manner. The results demonstrate that epertinib enhances drug-induced apoptosis in these cancer cells by impeding the drug-efflux function of ABCB1 and ABCG2 without altering their expression. ATPase activity and molecular docking were employed to reveal potential interaction sites between epertinib and the drug-binding pockets of ABCB1 and ABCG2. In summary, our study demonstrates an additional pharmacological capability of epertinib against the activity of ABCB1 and ABCG2. These findings suggest that incorporating epertinib into combination therapy could be advantageous for a specific patient subset with tumors exhibiting high levels of ABCB1 or ABCG2, warranting further exploration.

Magnolol derivatives as specific and noncytotoxic inhibitors of breast cancer resistance protein (BCRP/ABCG2)

The breast cancer resistance protein (BCRP/ABCG2) transporter mediates the efflux of numerous antineoplastic drugs, playing a central role in multidrug resistance related to cancer. The absence of successful clinical trials using specific ABCG2 inhibitors reveals the urge to identify new compounds to attend this critical demand. In this work, a series of 13 magnolol derivatives was tested as ABCG2 inhibitors. Only two compounds, derivatives 10 and 11, showed partial and complete ABCG2 inhibitory effect, respectively. This inhibition was selective toward ABCG2, since none of the 13 compounds inhibited neither P-glycoprotein nor MRP1. Both inhibitors (10 and 11) were not transported by ABCG2 and demonstrated a low cytotoxic profile even at high concentrations (up to 100 µM). 11 emerged as the most promising compound of the series, considering the ratio between cytotoxicity (IG50) and ABCG2 inhibition potency (IC50), showing a therapeutic ratio (TR) higher than observed for 10 (10.5 versus 1.6, respectively). This derivative showed a substrate-independent and a mixed type of inhibition. The effect of compound 11 on the ABCG2 ATPase activity and thermostability revealed allosteric protein changes. This compound did not affect the expression levels of ABCG2 and increased the binding of the conformational-sensitive antibody 5D3. A docking study showed that 11 did not share the same binding site with ABCG2 substrate mitoxantrone. Finally, 11 could revert the chemoresistance to SN-38 mediated by ABCG2.

USP10 suppresses ABCG2-induced malignant characteristics of doxorubicin-resistant thyroid cancer by inhibiting PI3K/AKT pathway

Doxorubicin (DOX) is the most extensively used drug in the chemotherapy of thyroid cancer (TC). However, the existence of DOX resistance is not conducive to TC treatment. Here, we investigated the role of USP10 in DOX-resistant TC and explored the underlying molecular mechanism. CCK-8 assay was used to measure cell viability in thyroid cancer FTC133 and DOX-resistant FTC133-DOX cells. RT-qPCR and western blot were used to evaluate USP10 expression. Cell migration, invasion, and apoptotic assays were conducted. Western blot was used to detect cellular signaling proteins, EMT-related proteins, and apoptosis-related proteins. We found a lower expression of USP10 in the human TC cell line FTC133 as compared to the normal human thyroid Htori-3 cells. Notably, USP10 expression was further reduced in DOX-resistant (FTC133-DOX) cells compared to the FTC133 cells. FTC133-DOX cells had increased invasion, migration, and EMT properties while less apoptosis by activating the PI3K/AKT pathway. Interestingly, overexpressing USP10 increased the chemosensitivity of FTC133 cells to DOX therapy. Overexpressing USP10 inhibited invasion, migration, and EMT properties of FTC133-DOX cells and promoted apoptosis. Mechanistically, overexpressing USP10 inhibited PI3K/AKT pathway by activating PTEN. Furthermore, overexpressed USP10 controlled all these processes by downregulating ABCG2. This study demonstrates that USP10 could reduce DOX-induced resistance of TC cells to DOX therapy and could suppress TC malignant behavior by inhibiting the PI3K/AKT pathway. Furthermore, USP10 targeted ABCG2 to inhibit all these malignant processes, therefore, either increasing USP10 expression or inhibiting ABCG2 could be used as novel targets for treating DOX-resistant thyroid cancer.

Recent advances in targeting the "undruggable" proteins: from drug discovery to clinical trials

Undruggable proteins are a class of proteins that are often characterized by large, complex structures or functions that are difficult to interfere with using conventional drug design strategies. Targeting such undruggable targets has been considered also a great opportunity for treatment of human diseases and has attracted substantial efforts in the field of medicine. Therefore, in this review, we focus on the recent development of drug discovery targeting "undruggable" proteins and their application in clinic. To make this review well organized, we discuss the design strategies targeting the undruggable proteins, including covalent regulation, allosteric inhibition, protein-protein/DNA interaction inhibition, targeted proteins regulation, nucleic acid-based approach, immunotherapy and others.

Glutamine metabolism targeting liposomes for synergistic chemosensitization and starvation therapy in ovarian cancer

Platinum-based chemotherapy is a first-line therapeutic regimen against ovarian cancer (OC); however, the therapeutic potential is always reduced by glutamine metabolism. Herein, a valid strategy of inhibiting glutamine metabolism was proposed to cause tumor starvation and chemosensitization. Specifically, reactive oxygen species-responsive liposomes were developed to co-deliver cisplatin (CDDP) and bis-2-(5-phenylacetamido-1,3,4-thiadiazol-2-yl) ethyl sulfide (BPTES) [C@B LPs]. The C@B LPs induced effective tumor cell starvation and significantly sensitized OC cells to CDDP by reducing glutathione generation to prevent CDDP detoxification, suppressing ATP production to avoid CDDP efflux, hindering nucleotide synthesis to aggravate DNA damage induced by CDDP, and blocking mammalian target of rapamycin (mTOR) signaling to promote cell apoptosis. More importantly, C@B LPs remarkably inhibited tumor growth in vivo and reduced the side effects. Taken together, this study provided a successful strategy of synergistic chemosensitization and starvation therapy escalating the rate of therapeutic success in OCs. STATEMENT OF SIGNIFICANCE: This work proposed a valid strategy of inhibiting glutamine metabolism to cause tumor starvation and chemosensitization. Specifically, ROS-responsive liposomes were developed to co-deliver cisplatin CDDP and BPTES [C@B LPs]. The C@B LPs induced effective tumor cell starvation and significantly sensitized OC cells to cisplatin by reducing glutathione generation to prevent cisplatin detoxification, suppressing ATP production to avoid cisplatin efflux, hindering nucleotide synthesis to aggravate DNA damage induced by cisplatin, and blocking mTOR signaling to promote cell apoptosis. More importantly, C@B LPs remarkably inhibited tumor growth in vivo and reduced the side effects. Taken together, this study provided a successful strategy of synergistic chemosensitization and starvation therapy escalating the rate of therapeutic success in OCs.

In silico screening of c-Met tyrosine kinase inhibitors targeting nucleotide and drug-substrate binding sites of ABCB1 as potential MDR reversal agents

PURPOSE

Cancer is a significant public health problem and ranks as a leading cause of death globally. Multidrug resistance (MDR) affects the therapeutic potential of conventional chemotherapeutic agents in cancer chemotherapy. Receptor tyrosine kinases (RTKs) are enzymes whose aberrant activation contributes to the tumorigenesis of various types of cancers. The ability of several RTKs, such as c-Met, to reverse ABC transporters mediated MDR was shown before. We aimed to explore the ability of c-Met inhibitors to circumvent MDR in cancer by inhibiting the ABCB1 transporter using in silico studies.

METHODS

Docking virtual screening of several potent and structurally diverse c-Met inhibitors were applied to find repurposed candidates to target the ATP binding sites and drug-substrate binding pockets of the ABCB1 transporter. The selected candidate was subjected to molecular dynamics simulations.

RESULTS

Based on docking findings, among 19 clinical c-Met inhibitors, several drugs, particularly golvatinib, exerted the affinity to both ATP binding sites in the nucleotide-binding domains (NBDs) as well as the drug-substrate binding site in the transmembrane domains (TMDs). Moreover, several non-clinical c-Met inhibitors obtained from the ChEMBL database had strong interactions with TMDs and NBDs, among which CHEMBL1950194 and CHEMBL2385194 compounds showed the highest binding affinity, respectively. Additionally, as a potential repositioning drug, MD simulation studies of golvatinib, corroborated the docking results.

CONCLUSION

We applied docking and molecular dynamics simulations to screen the potential c-Met inhibitors as the MDR reversing agents targeting ATP and drug-substrate binding sites, and the results suggested several repurposed candidate drugs.

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 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.

Lazertinib improves the efficacy of chemotherapeutic drugs in ABCB1 or ABCG2 overexpression cancer cells in vitro, in vivo, and ex vivo

Multidrug resistance (MDR) is the major cause of chemotherapy failure, which is usually caused by the overexpression of ATP-binding cassette (ABC) transporters such as ABCB1 and ABCG2. To date, no MDR modulator has been clinically approved. Here, we found that lazertinib (YH25448; a novel third-generation tyrosine kinase inhibitor [TKI]) could enhance the anticancer efficacy of MDR transporter substrate anticancer drugs in vitro，in vivo, and ex vivo. Mechanistically, lazertinib was shown to inhibit the drug efflux activities of ABCB1 and ABCG2 and thus increase the intracellular accumulation of the transporter substrate anticancer drug. Moreover, lazertinib was found to stimulate the ATPase activity of ABCB1/ABCG2 and inhibit the photolabeling of the transporters by ¹²⁵I-iodoarylazidoprazosin (IAAP). However, lazertinib neither changed the expression or locolization of ABCB1 and ABCG2 nor blocked the signal pathway of Akt or Erk1/2 at a drug concentration effective for MDR reversal. Overall, our results demonstrate that lazertinib effectively reverses ABCB1- or ABCG2-mediated MDR by competitively binding to the ATP-binding site and inhibiting drug efflux function. This is the first report demonstrating the novel combined use of lazertinib and conventional chemotherapeutical drugs to overcome MDR in ABCB1/ABCG2-overexpressing cancer cells.

A new porphyrin as selective substrate-based inhibitor of breast cancer resistance protein (BCRP/ABCG2)

The ABCG2 transporter plays a pivotal role in multidrug resistance, however, no clinical trial using specific ABCG2 inhibitors have been successful. Although ABC transporters actively extrude a wide variety of substrates, photodynamic therapeutic agents with porphyrinic scaffolds are exclusively transported by ABCG2. In this work, we describe for the first time a porphyrin derivative (4B) inhibitor of ABCG2 and capable to overcome multidrug resistance in vitro. The inhibition was time-dependent and 4B was not itself transported by ABCG2. Independently of the substrate, the porphyrin 4B showed an IC₅₀ value of 1.6 μM and a mixed type of inhibition. This compound inhibited the ATPase activity and increased the binding of the conformational-sensitive antibody 5D3. A thermostability assay confirmed allosteric protein changes triggered by the porphyrin. Long-timescale molecular dynamics simulations revealed a different behavior between the ABCG2 porphyrinic substrate pheophorbide a and the porphyrin 4B. Pheophorbide a was able to bind in three different protein sites but 4B showed one binding conformation with a strong ionic interaction with GLU446. The inhibition was selective toward ABCG2, since no inhibition was observed for P-glycoprotein and MRP1. Finally, this compound successfully chemosensitized cells that overexpress ABCG2. These findings reinforce that substrates may be a privileged source of chemical scaffolds for identification of new inhibitors of multidrug resistance-linked ABC transporters.

The third-generation EGFR inhibitor almonertinib (HS-10296) resensitizes ABCB1-overexpressing multidrug-resistant cancer cells to chemotherapeutic drugs

The overexpression of the human ATP-binding cassette (ABC) drug transporter ABCB1 (P-glycoprotein, P-gp) or ABCG2 (breast cancer resistance protein, BCRP) in cancer cells often contributes significantly to the development of multidrug resistance (MDR) in cancer patients. Previous reports have demonstrated that some epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) could modulate the activity of ABCB1 and/or ABCG2 in human cancer cells, whereas some EGFR TKIs are transport substrates of these transporters. Almonertinib (HS-10296) is a promising, orally available third-generation EGFR TKI for the treatment of EGFR T790M mutation-positive non-small cell lung cancer (NSCLC) in patients who have progressed on or after other EGFR TKI therapies. Additional clinical trials are currently in progress to study almonertinib as monotherapy and in combination with other agents in patients with NSCLC. In the present work, we found that neither ABCB1 nor ABCG2 confers significant resistance to almonertinib. More importantly, we discovered that almonertinib was able to reverse MDR mediated by ABCB1, but not ABCG2, in multidrug-resistant cancer cells at submicromolar concentrations by inhibiting the drug transport activity of ABCB1 without affecting its expression level. These findings are further supported by in silico docking of almonertinib in the drug-binding pocket of ABCB1. In summary, our study revealed an additional activity of almonertinib to re-sensitize ABCB1-overexpressing multidrug-resistant cancer cells to conventional chemotherapeutic drugs, which may be beneficial for cancer patients and warrant further investigation.

Hedgehog signaling in gastrointestinal carcinogenesis and the gastrointestinal tumor microenvironment

The Hedgehog (HH) signaling pathway plays important roles in gastrointestinal carcinogenesis and the gastrointestinal tumor microenvironment (TME). Aberrant HH signaling activation may accelerate the growth of gastrointestinal tumors and lead to tumor immune tolerance and drug resistance. The interaction between HH signaling and the TME is intimately involved in these processes, for example, tumor growth, tumor immune tolerance, inflammation, and drug resistance. Evidence indicates that inflammatory factors in the TME, such as interleukin 6 (IL-6) and interferon-γ (IFN-γ), macrophages, and T cell-dependent immune responses, play a vital role in tumor growth by affecting the HH signaling pathway. Moreover, inhibition of proliferating cancer-associated fibroblasts (CAFs) and inflammatory factors can normalize the TME by suppressing HH signaling. Furthermore, aberrant HH signaling activation is favorable to both the proliferation of cancer stem cells (CSCs) and the drug resistance of gastrointestinal tumors. This review discusses the current understanding of the role and mechanism of aberrant HH signaling activation in gastrointestinal carcinogenesis, the gastrointestinal TME, tumor immune tolerance and drug resistance and highlights the underlying therapeutic opportunities.

pH-responsive delivery vehicle based on RGD-modified polydopamine-paclitaxel-loaded poly (3-hydroxybutyrate-co-3-hydroxyvalerate) nanoparticles for targeted therapy in hepatocellular carcinoma

A limitation of current anticancer nanocarriers is the contradiction between multiple functions and favorable biocompatibility. Thus, we aimed to develop a compatible drug delivery system loaded with paclitaxel (PTX) for hepatocellular carcinoma (HCC) therapy. A basic backbone, PTX-loaded poly (3-hydroxybutyrate-co-3-hydroxyvalerate) PHBV nanoparticle (PHBV-PTX-NPs), was prepared by emulsion solvent evaporation. As a gatekeeper, the pH-sensitive coating was formed by self-polymerization of dopamine (PDA). The HCC-targeted arginine-glycine-aspartic acid (RGD)-peptide and PDA-coated nanoparticles (NPs) were combined through the Michael addition. Subsequently, the physicochemical properties of RGD-PDA-PHBV-PTX-NPs were characterized by dynamic light scattering-autosizer, transmission electron microscope, fourier transform infrared spectroscopy, differential scanning calorimetry, thermogravimetry and X-ray spectroscopy. As expected, the RGD-PDA-PHBV-PTX-NPs showed robust anticancer efficacy in a xenograft mouse model. More importantly, they exhibited lower toxicity than PTX to normal hepatocytes and mouse in vitro and in vivo, respectively. Taken together, these results indicate that the RGD-PDA-PHBV-PTX-NPs are potentially beneficial for easing conflict between multifunction and biocompatible characters of nanocarriers.

Poziotinib Inhibits the Efflux Activity of the ABCB1 and ABCG2 Transporters and the Expression of the ABCG2 Transporter Protein in Multidrug Resistant Colon Cancer Cells

Simple Summary

Globally, colorectal cancer (CRC) is a leading cause of cancer deaths and chemotherapy, in combination with radiotherapy when appropriate, is used to treat the majority of CRC patients. However, the acquisition or development of drug resistance can decrease, or even abolish, the efficacy of chemotherapy. ATP-binding cassette (ABC) transporters, particularly, the ABCB1 and ABCG2 transporter, are mediators of multidrug resistance (MDR) in certain types of cancer cells. The aim of our in vitro study was to determine if poziotinib can overcome MDR to certain chemotherapeutic drugs in colon cancer cells. Our results indicated that in MDR CRC cell lines, poziotinib inhibits the transport function of the ABCB1 and ABCG2 transporters, increasing the intracellular accumulation of certain anticancer drugs, and thus, their efficacy. Furthermore, poziotinib decreased the expression of the ABCG2 protein. Therefore, if our results can be translated to humans, they suggest that using poziotinib in combination with certain anticancer drugs may be of therapeutic benefit in colorectal cancer patients.

Abstract

Colorectal cancer (CRC) is a leading cause of cancer deaths in the United States. Currently, chemotherapy is a first-line treatment for CRC. However, one major drawback of chemotherapy is the emergence of multidrug resistance (MDR). It has been well-established that the overexpression of the ABCB1 and/or ABCG2 transporters can produce MDR in cancer cells. In this study, we report that in vitro, poziotinib can antagonize both ABCB1- and ABCG2-mediated MDR at 0.1–0.6 μM in the human colon cancer cell lines, SW620/Ad300 and S1-M1-80. Mechanistic studies indicated that poziotinib increases the intracellular accumulation of the ABCB1 transporter substrates, paclitaxel and doxorubicin, and the ABCG2 transporter substrates, mitoxantrone and SN-38, by inhibiting their substrate efflux function. Accumulation assay results suggested that poziotinib binds reversibly to the ABCG2 and ABCB1 transporter. Furthermore, western blot experiments indicated that poziotinib, at 0.6 μM, significantly downregulates the expression of the ABCG2 but not the ABCB1 transporter protein, suggesting that the ABCG2 reversal effect produced by poziotinib is due to transporter downregulation and inhibition of substrate efflux. Poziotinib concentration-dependently stimulated the ATPase activity of both ABCB1 and ABCG2, with EC₅₀ values of 0.02 μM and 0.21 μM, respectively, suggesting that it interacts with the drug-substrate binding site. Molecular docking analysis indicated that poziotinib binds to the ABCB1 (−6.6 kcal/mol) and ABCG2 (−10.1 kcal/mol) drug-substrate binding site. In summary, our novel results show that poziotinib interacts with the ABCB1 and ABCG2 transporter, suggesting that poziotinib may increase the efficacy of certain chemotherapeutic drugs used in treating MDR CRC.