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Jurkat/A4 cells with multidrug resistance exhibit reduced sensitivity to quercetin
Background: While multidrug resistance of cancer cells is a well-known phenomenon, little is known on the cross resistance between cytotoxic chemotherapeutical agents and unrelated substances such as natural flavonoids. Aim: To compare the effects of cytotoxic drug, vepeside and natural flavonoid, quercetin in Jurkat cells and their multidrug-resistant subline Jurkat/A4, in particular to analyze the effector mechanisms of apoptosis and the profiles of several pro- and antiapoptotic proteins in these cells upon exposure to vepeside or quercetin. Methods: Apoptosis and poly (ADP-ribose) polymerase cleavage were assessed by flow cytometry. Expression of apoptosisrelated proteins was analyzed by Western blotting. Results: Jurkat/A4 cells are less sensitive to antiproliferative effects of quercetin as compared with the parental Jurkat cell line. While vepeside as well as quercetin initially induces apoptosis in both cell lines, the following survival of the exposed cells is essentially different. In resistant Jurkat/A4 cells, vepeside or quercetin treatment activates significantly less caspase-9 and -3 as compared with that in the parental cells. The expression of Bad and BNip1 proteins in Jurkat/A4 cells is lower than in the parental cell line. At the same time, XIAP and CAS levels in Jurkat/A4 cells increase. Upon apoptosis induction, XIAP and CAS levels in Jurkat cells decrease, this effect being negligible in resistant cells. Conclusion: Multidrug-resistant Jurkat/A4 cells exhibit reduced sensitivity to cytotoxic effects of quercetin. The expression profile of Jurkat/A4 cells is characterized by the increased levels of XIAP and CAS representing the endogenous inhibitors of apoptosis.
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