Increase in the Level of P-Glycoprotein mRNA Expression in Multidrug-resistant K562 Cell Lines Treated with Sodium Butyrate Is Not Accompanied with Erythroid Differentiation

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Abstract
We examined the effects of hemin, sodium butyrate and mitomycin C on levels of P‐glycoprotein mRNA in human myelogenous K562 cells by northern blot analysis. After treatment with sodium butyrate a dose‐dependent increase of P‐glycoprotein mRNA expression was observed in the adriamycin‐resistant K562 and vincristine‐resistant K562 lines. With 10 mM sodium butyrate, the level of P‐glycoprotein mRNA reached 20 times that of control adriamycin‐resistant K562 and with 30 mM sodium butyrate, it exceeded 5 times that of control vincristine‐resistant K562. In contrast, hemin and mitomycin C had almost no effect on P‐glycoprotein mRNA. In this experiment, since expression of P‐glycoprotein mRNA was not necessarily accompanied with induction of erythroid differentiation, the increased amount of P‐glycoprotein mRNA is unlikely to be a result of differentiation.