Modulation of P-glycoprotein multidrug transporter in chronic myeloid leukemia cells by 8-acetoxypinoresinol

LIOLO, J.; JORAY M.B.; GONZÁLEZ M.L.; RUMJANEK V; CARPINELLA M. C.

Simposio; X Simpósio de Oncobiologia.; 2016

Programa de Oncobiología, Universidad Federal de Rio de Janeiro

Introduction and objective: P-Glycoprotein (P-gp) is an ATP- dependent efflux pump responsible for the elimination of hundreds of structurally unrelated agents compounds, including anticancer drugs. This trans-membrane pump is linked to multidrug resistance (MDR) in cancer cells, being one of the major barriers to successful chemotherapy treatment. With the aim of reversing resistance, 8-acetoxypinoresinol (1) was tested in the P-gp over-expressing human myelogenous leukemia cells (CML). Materials and methods: The K562 human CML cell line and its MDR counterpart Lucena 1 were used for the assays. The effect of 1 on doxorubicin (DOX) cytotoxicity was evaluated by the multidrug resistance reversal assay (MTT). Intracellular DOX accumulation was determined with by flow cytometry. The cytotoxicity of 1 on peripheral blood mononuclear cells (PBMC) was them evaluated by the MTT assay. Data were analyzed using Student´s t test or one or two-ways analysis of variance (ANOVA), regarding p-values ≤ 0.05 as statistically significant. All experiments were performed at least three times. Results and conclusion: Compound 1 increased DOX cytotoxicity by a factor of 21.5 at 14 µM and 1.4 at 0.11 µM showing the same level of activity than that observed with the commercial modulator verapamil. At 14 µM, no potentiation in DOX activity was observed in K562 cells. When tested at the maximum non-toxic concentration (28 µM) it caused a 96.8-fold sensitization to DOX in Lucena 1 while a 17.3-fold sensitization was observed in K562, meaning that this shift in the IC50 of DOX was not only due to P-gp inhibition. This result was confirmed by significant increase in the intracellular DOX accumulation in MDR cells, where the minimum effective concentration of the compound was 0.87 µM. In addition, 1 did not affect cell viability of PBMC up to 28 µM. In conclusion, the present study demonstrates that 8-acetoxypinoresinol significantly inhibits the function of human P-gp.