Multidrug-resistant Human Cancer Cell Line Research Articles

Abstract 1321: IT-147: A stabilized polymer micelle formulation of epothilone D for treatment of solid tumors

Abstract IT-147 is a formulation of epothilone D encapsulated in a stabilized polymer micelle. Epothilones are a class of cytotoxic chemotherapeutics that induce apoptosis via microtubule stabilization. Epothilone D is a poor substrate for P-glycoprotein efflux pumps and has demonstrated equivalent activity against drug-sensitive and multidrug-resistant human cancer cell lines. This offers a distinct advantage over other microtubule stabilizing agents such as taxanes, however clinical utility is limited by a narrow therapeutic window due to dose limiting toxicities such as peripheral sensory neuropathy, GI toxicities, and cognitive abnormalities. We have optimized a lead formulation comprising 2% epothilone D (w/w) encapsulated in a polymer micelle that is crosslinked with iron to provide micelle stability upon dilution. IT-147 has an average diameter of 70 nm. The iron-mediated crosslinking provides pH-dependent release of epothilone D such that drug can be released in the tumor microenvironment as well as in the endosome/lysosome upon cellular entry. In addition, the geometrical arrangement of iron molecules around the core of the micelle imparts superparamagnetic properties that allow for imaging of intact nanoparticles by MRI. IT-147 demonstrates a low nanomolar IC50 against a panel of human cancer cell lines in vitro. In vivo, IT-147 demonstrates a 4-fold increase in maximum tolerated dose in a mouse model compared to epothilone D free drug. Pharmacokinetics (PK) in a cannulated rat model for a 20 mg/kg epothilone D dose demonstrates a 6.5-fold increase in area under the time versus concentration curve (AUC), and a 14.3-fold increase in the terminal half-life compared to free drug. Dose escalation of IT-147 to 30 and 40 mg/kg epothilone D in the rat PK model results in linear increases in AUC from 53.5 h*μg/mL at 20 mg/kg to 82.9 and 110.8 h*μg/mL at 30 and 40 mg/kg, respectively. Treatment with IT-147 at the MTD in an HCT116 tumor xenograft model led to tumor stasis during the course of treatment, and MRI imaging of mice treated with IT-147 demonstrates tumor accumulation over 24 and 48 hours post administration. Taken together, data for IT-147 demonstrates successful encapsulation of epothilone D leading to a safer, more effective formulation with the potential for MRI imaging as a predictor for response. Citation Format: Adam Carie, Taylor Buley, Bradford Sullivan, J.Edward Semple, Tyler Ellis, Tara Lee Costich, Jyothi Sethuraman, Rick Crouse, Kevin Sill, Suzanne Bakewell. IT-147: A stabilized polymer micelle formulation of epothilone D for treatment of solid tumors. [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 1321.

Reversion of P-glycoprotein-mediated multidrug resistance by guggulsterone in multidrug-resistant human cancer cell lines

Multidrug resistance (MDR) presents a serious problem in cancer chemotherapy. Our previous studies have shown that guggulsterone could reverse MDR through inhibiting the function and expression of P-glycoprotein (P-gp). The present study is to further investigate the reversal effects of guggulsterone on MDR in drug-resistant cancer cell lines. The effects of guggulsterone on MDR1mRNA gene expression, intracellular pH, P-gp ATPase activity and glucosylceramide synthase (GCS) expression were assessed by RT-PCR, Laser Scanning Confocal Microscope using the pH-sensitive fluorescent probe BCECF-AM, Pgp-Glo assay system, and flow cytometric technology, respectively. The results showed that guggulsterone ranging from 2.5 to 80μM significantly promoted the activity of P-gp ATPase in a dose-dependent manner. The intracellular pH of K562/DOX cells was found to be higher than K562 cells. After treatment with guggulsterone (1, 3, 10, 30, 100μM), intracellular pH of K562/DOX cells decreased in a dose- and time-dependent manner. However, the present study revealed that guggulsterone ranging from 3 to 100μM had little influence on MDR1 gene expression in K562/DOX cells. Further, the isogenic doxorubicin-resistant MCF-7/DOX cells exhibited a 4.9-fold increase in GCS level as compared with parental MCF-7 human breast cancer cells. After treatment with guggulsterone (0.1, 1, 10μM) for 48h, MCF-7/DOX cells were found to have no change of GCS protein expression amount. Guggulsterone might be a potent MDR reversal agent, and its mechanism on MDR needs more research.

Methyl-beta-cyclodextrin in HL-60 parental and multidrug-resistant cancer cell lines: effect on the cytotoxic activity and intracellular accumulation of doxorubicin.

The purpose of this work was to determine the role of methyl-beta-cyclodextrin (MEBCD) in combination with doxorubicin (DOX) on the cellular proliferation of a sensitive parental and a multidrug-resistant human cancer cell line (HL-60 S and HL-60 R) and to study the effect of MEBCD on DOX intracellular accumulation. The cytotoxicity of DOX at five concentrations (50-50,000 nM) was evaluated with or without the coadministration of four fixed noncytotoxic concentrations of MEBCD (100, 200, 500, and 1,000 microM). Intracellular DOX concentrations were determined by a high-performance liquid chromatography (HPLC) method with fluorescence detection. MEBCD applied at 500 and 1000 microM in combination with doxorubicin (DOX) significantly potentiated the activity of DOX used alone on both sensitive and multidrug-resistant cell lines; 50% growth-inhibitory (IC50) ratios (IC50 MEBCD-DOX/IC50 DOX) were about 3:4 and 1.6:4 for HL-60 S and HL-60 R, respectively. Moreover, intracellular DOX accumulation, determined by HPLC during 6 h of drug exposure, was about 2-4 times higher for cells treated with MEBCD in combination with DOX than in those treated with DOX alone. Similar results were obtained using other paired MCF 7 sensitive and resistant cell lines. Correlation between these results and an MEBCD-cell membrane interaction was discussed. These initial data provide a basis for the potential therapeutic application of MEMBCD in cancer therapy.