Document Type: Research Articles
Department of Biochemistry, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand.
Excellent Center for Research and Development of Natural Products for Health, Chiang Mai University, Chiang Mai, Thailand.
School of Chemistry, University of Wollongong, Wollongong, New South Wales, Australia.
Our previous study reported that stemofoline (STF) exhibited a synergistic effect with chemotherapeutic drugs in
human multidrug-resistant (MDR) leukemic cells (K526/Adr) by inhibiting the function of P-glycoprotein, which is a
membrane transporter that is overexpressed in several types of MDR cancers. This study further investigated the effects of
a combination treatment of STF and doxorubicin (DOX) in vitro and in vivo. The combination treatment of 50 mg/kg of
STF strongly enhanced the anti-tumor activity of DOX in SCID-beige mice bearing K562/Adr xenografts without
additional toxicity when compared to the single treatment groups. Additionally, an examination of the proliferation
markers (Ki67) and the apoptotic marker (TUNEL) in tumor tissues in each group revealed that the combination
therapy significantly reduced Ki67 positive cells and increased apoptotic cells. From the in vitro experiments we also
found that this combination treatment dramatically induced G1 and G2M arrest in K562/Adr when compared to a single
treatment of DOX. STF treatment alone did not show any cytotoxic effect to the cells. These results suggest that the
accumulation of DOX enhanced by STF was sufficient to induce cell cycle arrest in K562/Adr. These findings support
our previous in vitro data and indicate the possibility of developing STF as an adjuvant therapy in cancer treatments.