Sensitization of K562 Leukemia Cells to Doxorubicin by the Viscum album Extract.

Toxicity of conventional chemotherapeutics highlights the requirement for complementary or alternative medicines that would reduce side effects and improve their anticancer effectiveness. European mistletoe (Viscum album) has long been used as a complementary and alternative medicine supporting cancer therapy. The aim of this study was to investigate synergistic antitumor action of V. album extract and doxorubicin during co-treatment of chemoresistant chronic myelogenic leukemia K562 cells. Combined treatment of leukemia cells led to inhibitory synergism at sub-apoptotic doxorubicin concentrations and multifold reduction of cytotoxic effects in healthy control cells. Prolonged co-treatment was associated with reduced G2/M accumulation and increased expression of early and late apoptotic markers. Our data indicate that V. album extract increases antileukemic effectiveness of doxorubicin against resistant K562 cells by preventing G2/M arrest and inducing apoptosis.