Guan-Nan Zhang

β-elemene, a compound derived from Rhizoma zedoariae, reverses multidrug resistance mediated by the ABCB1 transporter

In the present in vitro study, we examined the effect of the compound β-elemene on the response of KB-C2 cells overexpressing the ABCB1 transporter to specific antineoplastic compounds. The MTT assay was used to determine the effects of β-elemene in combination with other anticancer drugs on ABCB1-overexpressing cancer cell lines. Furthermore, we used [3H]-paclitaxel accumulation, efflux assay, immunofluorescence experiments, western blot assays and docking analysis to ascertain the mechanism of action of β-elemene. The incubation of KB-C2 cells overexpressing ABCB1 transporter with β-elemene (100 µM) significantly augmented the antineoplastic efficacy of colchicine, vinblastine and paclitaxel when compared to KB-C2 cells incubated with these drugs alone. In HEK293 cells overexpressing the ABCB1 transporter, β-elemene significantly increased the cytotoxicity of paclitaxel. In addition, 100 µM of β-elemene significantly increased the accumulation of [3H]-paclitaxel and this was due to a decrease in [3H]-paclitaxel efflux when compared to controls. The incubation of KB-C2 cells with β-elemene (100 µM) for 72 h did not significantly alter the expression of ABCB1 protein levels. Immunofluorescence experiments indicated that β-elemene did not significantly alter the subcellular localization of the ABCB1 transporter. Docking analysis indicated that β-elemene binds to the drug-binding site of ABCB1 transporter. Finally, β-elemene at 100 µM partially (~50%) increased the sensitivity of the BCRP-overexpressing cell line, NCI-H460/MX20, to mitoxantrone, but β-elemene did not significantly alter the resistance of MRP1-transfected HEK293/MRP1 cells to vincristine. Overall, our in vitro findings indicated that β-elemene potentiates the cytotoxic effects of various antineoplastic drugs in cell lines overexpressing the ABCB1 transporter and that this is due to the inhibition of the efflux component of the ABCB1 transporter.

Bafetinib (INNO-406) reverses multidrug resistance by inhibiting the efflux function of ABCB1 and ABCG2 transporters.

ATP-Binding Cassette transporters are involved in the efflux of xenobiotic compounds and are responsible for decreasing drug accumulation in multidrug resistant (MDR) cells. Discovered by structure-based virtual screening algorithms, bafetinib, a Bcr-Abl/Lyn tyrosine kinase inhibitor, was found to have inhibitory effects on both ABCB1- and ABCG2-mediated MDR in this in-vitro investigation. Bafetinib significantly sensitized ABCB1 and ABCG2 overexpressing MDR cells to their anticancer substrates and increased the intracellular accumulation of anticancer drugs, particularly doxorubicin and [3H]-paclitaxel in ABCB1 overexpressing cells; mitoxantrone and [3H]-mitoxantrone in ABCG2 overexpressing cells, respectively. Bafetinib stimulated ABCB1 ATPase activities while inhibited ABCG2 ATPase activities. There were no significant changes in the expression level or the subcellular distribution of ABCB1 and ABCG2 in the cells exposed to 3 μM of bafetinib. Overall, our study indicated that bafetinib reversed ABCB1- and ABCG2-mediated MDR by blocking the drug efflux function of these transporters. These findings might be useful in developing combination therapy for MDR cancer treatment.

Tea nanoparticle, a safe and biocompatible nanocarrier, greatly potentiates the anticancer activity of doxorubicin

An infusion-dialysis based procedure has been developed as an approach to isolate organic nanoparticles from green tea. Tea nanoparticle (TNP) can effectively load doxorubicin (DOX) via electrostatic and hydrophobic interactions. We established an ABCB1 overexpressing tumor xenograft mouse model to investigate whether TNP can effectively deliver DOX into tumors and bypass the efflux function of the ABCB1 transporter, thereby increasing the intratumoral accumulation of DOX and potentiating the anticancer activity of DOX. MTT assays suggested that DOX-TNP showed higher cytotoxicity toward CCD-18Co, SW620 and SW620/Ad300 cells than DOX. Animal study revealed that DOX-TNP resulted in greater inhibitory effects on the growth of SW620 and SW620/Ad300 tumors than DOX. In pharmacokinetics study, DOX-TNP greatly increased the SW620 and SW620/Ad300 intratumoral concentrations of DOX. But DOX-TNP had no effect on the plasma concentrations of DOX. Furthermore, TNP is a safe nanocarrier with excellent biocompatibility and minimal toxicity. Ex vivo IHC analysis of SW620 and SW620/Ad300 tumor sections revealed evidence of prominent antitumor activity of DOX-TNP. In conclusion, our findings suggested that natural nanomaterials could be useful in combating multidrug resistance (MDR) in cancer cells and potentiating the anticancer activity of chemotherapeutic agents in cancer treatment.

Regorafenib overcomes chemotherapeutic multidrug resistance mediated by ABCB1 transporter in colorectal cancer: In vitro and in vivo study

Chemotherapeutic multidrug resistance (MDR) is a significant challenge to overcome in clinic practice. Several mechanisms contribute to MDR, one of which is the augmented drug efflux induced by the upregulation of ABCB1 in cancer cells. Regorafenib, a multikinase inhibitor targeting the RAS/RAF/MEK/ERK pathway, was approved by the FDA to treat metastatic colorectal cancer and gastrointestinal stromal tumors. We investigated whether and how regorafenib overcame MDR mediated by ABCB1. The results showed that regorafenib reversed the ABCB1-mediated MDR and increased the accumulation of [3H]-paclitaxel in ABCB1-overexpressing cells by suppressing efflux activity of ABCB1, but not altering expression level and localization of ABCB1. Regorafenib inhibited ATPase activity of ABCB1. In mice bearing resistant colorectal tumors, regorafenib raised the intratumoral concentration of paclitaxel and suppressed the growth of resistant colorectal tumors. But regorafenib did not induce cardiotoxicity/myelosuppression of paclitaxel in mice. Strategy to reposition one FDA-approved anticancer drug regorafenib to overcome the resistance of another FDA-approved, widely used chemotherapeutic paclitaxel, may be a promising direction for the field of adjuvant chemotherapy. This study provides clinical rationale for combination of conventional chemotherapy and targeted anticancer agents.

Selective reversal of BCRP-mediated MDR by VEGFR-2 inhibitor ZM323881

ABSTRACT The expression of breast cancer resistant protein (BCRP) in lung cancer is correlated with development of multidrug resistance (MDR) and therefore leads to lower response to chemotherapy. ZM323881, a previously developed selective VEGFR‐2 inhibitor, was found to have inhibitory effects on BCRP‐mediated MDR in this investigation. ZM323881 significantly decreased the cytotoxic doses of mitoxantrone and SN‐38 in BCRP‐overexpressing NCI‐H460/MX20 cells. Mechanistic studies revealed that ZM323881 effected by inhibiting BCRP‐mediated drug efflux, leading to intracellular accumulation of BCRP substrates. No significant alteration in the expression levels and localization pattern of BCRP was observed when BCRP‐overexpressing cells were exposed to ZM323881. Stimulated bell‐shaped ATPase activities were observed. Molecular docking suggested that ZM323881 binds to the modulator site of BCRP and the binding pose is stable validated by 100 ns molecular dynamic simulation. Overall, our results indicated that ZM323881 reversed BCRP‐related MDR by inhibiting its efflux function. These findings might be useful in developing combination chemotherapy for MDR cancer treatment.

Modulating the function of ATP-binding cassette subfamily G member 2 (ABCG2) with inhibitor cabozantinib

Graphical abstract Figure. No Caption available. ABSTRACT Cabozantinib (XL184) is a small molecule tyrosine kinase receptor inhibitor, which targets c‐Met and VEGFR2. Cabozantinib has been approved by the Food and Drug Administration to treat advanced medullary thyroid cancer and renal cell carcinoma. In the present study, we evaluated the ability of cabozantinib to modulate the function of the ATP‐binding cassette subfamily G member 2 (ABCG2) by sensitizing cells that are resistant to ABCG2 substrate antineoplastic drugs. We used a drug‐selected resistant cell line H460/MX20 and three ABCG2 stable transfected cell lines ABCG2‐482‐R2, ABCG2‐482‐G2, and ABCG2‐482‐T7, which overexpress ABCG2. Cabozantinib, at non‐toxic concentrations (3 or 5 &mgr;M), sensitized the ABCG2‐overexpressing cells to mitoxantrone, SN‐38, and topotecan. Our results indicate that cabozantinib reverses ABCG2‐mediated multidrug resistance by antagonizing the drug efflux function of the ABCG2 transporter instead of downregulating its expression. The molecular docking analysis indicates that cabozantinib binds to the drug‐binding site of the ABCG2 transporter. Overall, our findings demonstrate that cabozantinib inhibits the ABCG2 transporter function and consequently enhances the effect of the antineoplastic agents that are substrates of ABCG2. Cabozantinib may be a useful agent in anticancer treatment regimens for patients who are resistant to ABCG2 substrate drugs.

Regorafenib antagonizes BCRP-mediated multidrug resistance in colon cancer

Overexpression of breast cancer resistance protein (BCRP) has been shown to produce multidrug resistance (MDR) in colon cancer, leading to major obstacles for chemotherapy. In this study, we evaluated the effect of regorafenib, an oral multi-kinase inhibitor, in inhibiting BCRP-mediated MDR in silico, in vitro and in vivo. We found that regorafenib significantly sensitized MDR colon cancer cells to BCRP substrates by increasing their intracellular accumulation. There are no significant changes in the expression level or the subcellular distribution of BCRP in the cells exposed to regorafenib. Investigation of the mechanism revealed that regorafenib stimulated BCRP ATPase activity. Our induced-fit docking and molecular dynamics simulations suggested the existence of a strong and stable interaction between regorafenib and the transmembrane domain of human crystalized BCRP. In vivo tumor xenograft study revealed that the combination of regorafenib and topotecan exhibited synergistic effects on mitoxantrone-resistant S1-M1-80 xenograft tumors. In conclusion, our studies indicate that regorafenib would be beneficial in combating MDR in colon cancer.

Abstract 4684: Modulating the function of multidrug resistance ABCG2 transporter by tyrosine kinases receptor inhibitor cabozantinib

Cabozantinib (XL184) is an oral tyrosine kinases receptor inhibitor which inhibits MET and vascular endothelial growth factor receptor 2 (VEGFR2). Cabozantinib has been approved by Food and Drug Administration for treating advanced medullary thyroid cancer and it is also tested in clinical trials on other solid tumors, including prostate, bladder, ovarian and breast cancer. In the present study, we evaluated the ability of cabozantinib in modulating the function of ABCG2 transporter in drug-selected H460/MX20 cell line and ABCG2 stable transfected cell lines ABCG2-482-R2, ABCG2-482-G2 and ABCG2-482-T7. Cabozantinib at non-toxic level can sensitize the ABCG2-overexpressing cells to antineoplastic drugs mitoxantrone, SN-38 and topotecan. Our results indicated that cabozantinib reversed ABCG2 mediated multi-drug resistance by antagonizing the drug efflux function of ABCG2. However, this reversal effect was not attributed to reduced expression of ABCG2 protein, because ABCG2 protein level was unchanged after treatment of 4μM cabozantinib for 72 hours. Immunofluorescence result showed that cabozantinib did not alter the cellular localization of ABCG2 transporter. Docking analysis indicated that cabozantinib binds to the drug-binding site of ABCG2 transporter. Finally, cabozantinib at 4μM did not significantly change the resistance of ABCB1 overexpressing cell line SW620/AD300 to antineoplastic drug paclitaxel. Overall, our finding demonstrated that cabozantinib potentiates the cytotoxic effects of various antineoplastic drugs that are substrates of ABCG2 and that this is due to modulating the function of ABCG2 transporter. Keyword: Cabozantinib; ABCG2; Multidrug resistance; Citation Format: Guannan Zhang, Yun-Kai Zhang, Yi-Jun Wang, Zhe-Sheng Chen. Modulating the function of multidrug resistance ABCG2 transporter by tyrosine kinases receptor inhibitor cabozantinib. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4684.

Abstract 2201: Tea nanoparticle, a safe and biocompatible nanocarrier, greatly potentiates the anticancer activity of doxorubicin

An infusion-dialysis based procedure has been developed as an approach to isolate organic nanoparticles from green tea. Tea nanoparticle (TNP) can effectively load doxorubicin (DOX) via electrostatic and hydrophobic interactions. We established an ABCB1 overexpressing tumor xenograft mouse model to investigate whether TNP can effectively deliver DOX into tumors and bypass the efflux function of the ABCB1 transporter, thereby increasing the intratumoral accumulation of DOX and potentiating the anticancer activity of DOX. MTT assays suggested that DOX-TNP showed higher cytotoxicity toward CCD-18Co, SW620 and SW620/Ad300 cells, as compared to DOX. Animal study revealed that DOX-TNP resulted in a greater inhibitory effect on the growth of SW620 and SW620/Ad300 tumors than DOX alone. The cTnI levels in mice showed that TNP had no cardiotoxicity and DOX-TNP had moderate cardiotoxicity. Blood Smear tests demonstrated that TNP and DOX-TNP did not cause neutropenia or thrombocytopenia in mice. Therefore, TNP is a safe nanocarrier with excellent biocompatibility and minimal toxicity. In pharmacokinetics study, DOX-TNP greatly increased the SW620 and SW620/Ad300 intratumoral concentrations of DOX, as compared to DOX alone. But DOX-TNP had no effect on the plasma concentrations of DOX up to 240 min after administration. Furthermore, ex vivo IHC analysis of SW620 and SW620/Ad300 tumor sections revealed evidence of prominent antitumor activity of DOX-TNP. In conclusion, our findings suggested that natural nanomaterials could be useful in combating multidrug resistance (MDR) in cancer cells and potentiating the anticancer activity of chemotherapeutic agents in cancer treatment. Citation Format: Yi-Jun Wang, Yujian Huang, Nagaraju Anreddy, Guan-Nan Zhang, Yun-Kai Zhang, Meina Xie, Derrick Lin, Dong-Hua Yang, Mingjun Zhang, Zhe-Sheng Chen. Tea nanoparticle, a safe and biocompatible nanocarrier, greatly potentiates the anticancer activity of doxorubicin. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2201.

Abstract 4422: TTT-28, a newly synthesized thiazole-valine peptide, antagonizes multidrug resistance by inhibiting the efflux activity of the ABCB1 transporter

Cancer cells often exhibit either intrinsic or acquired resistance to chemotherapy through a phenomenon known as multidrug resistance (MDR). Different mechanisms contribute to the development of MDR, preeminent among them being the accelerated drug efflux mediated by overexpression of ATP-binding cassette (ABC) transporters. Currently, it has been found that some small molecule tyrosine kinase inhibitors (TKIs), such as motesanib, linsitinib, masitinib and nilotinib, were able to modulate the activity of ABC transporters. Thus, the aim of this study was to determine whether TTT-28, a newly synthesized thiazole-valine peptide, could reverse ABCB1-mediated MDR. The results showed that TTT-28 significantly sensitized both ABCB1-transfected and drug-selected cell lines overexpressing this transporter to its substrate anticancer drugs. Using calcein-AM efflux assay, we identified TTT-28 (IC50 = 1.0 μM) carrying 3,4,5-trimethoxybenzoyl and 2-aminobenzophenone groups, respectively, at the amino and carboxyl termini of the monothiazole zwitterion. TTT-28 significantly increased the accumulation of [3H]-paclitaxel in ABCB1 overexpressing cells by blocking the efflux function of ABCB1 transporter. Furthermore, TTT-28 inhibited the photolabeling of ABCB1 with [125I]-iodoarylazidoprazosin with IC50 = 0.75 μM and stimulated the basal ATP hydrolysis of ABCB1 in a concentration-dependent manner (EC50 ATPase = 0.027 μM). Consistent with these findings, biochemical and docking studies showed site-1 to be the preferable binding site for TTT-28 within the drug-binding pocket of human ABCB1. Therefore, we report that TTT-28 antagonizes MDR by inhibiting the efflux activity of the ABCB1 transporter. These findings reveal high clinical values for the co-administration of TTT-28 and ABCB1 substrate chemotherapeutic drugs in cancer patients that overexpress ABCB1 and stimulate further research on circumventing the ABCB1-mediated MDR in cancers. Citation Format: Yi-Jun Wang, Nagaraju Anreddy, Bhargav A. Patel, Eduardo E. Chufan, Satyakam Singh, Guan-Nan Zhang, Yun-Kai Zhang, Anna Maria Barbuti, Suresh V. Ambudkar, Tanaji T. Talele, Zhe-Sheng Chen. TTT-28, a newly synthesized thiazole-valine peptide, antagonizes multidrug resistance by inhibiting the efflux activity of the ABCB1 transporter. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4422. doi:10.1158/1538-7445.AM2015-4422