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Introduction
Leukemia is a type of hematological malignancy of the blood and the bone marrow characterized by an abnormal increase in immature hemamegba called 'blasts' (1). Chemotherapy drugs kill cancer cells as well as normal cells, leading to significant side effects (2). As a step in overcoming this limitation in chemotherapy, medicines prepared from natural traditional Chinese medicine (TCM) are currently being considered as anticancer agents (3,4). In the past decades, a series of studies have demonstrated that many extracted products from natural plants can kill cancer cells including leukemia cells in vitro (5).
Ginsenosides (total saponins of Panax ginseng, TSPG), are important components extracted from the root of Panax ginseng. TSPG as an extract of a medicinal plant is used in a wide range of ailments and has been reported to have various potent biological functions, including improvement of physical and mental capacity, reduction of fatigue, regulation of the central nervous system and antitumor effects (6–10). TSPG includes many monomers, such as ginsenoside Rb1 (Rb1), ginsenoside Re (Re), ginsenoside Rg1 (Rg1), ginsenoside Rg3 (Rg3), 20(S)-ginsenoside Rh2 [(S)Rh2] and compound K. TSPG shows enhancement of proliferation and differentiation of bone marrow cells (9–12). To date, TSPG and its monomers have not been compared in regard to their effects on cell viability, thus research on the effects of TSPG and other monomers on proliferation inhibition in KG-1a cells is warranted.
(S)Rh2 belongs to the protopanaxadiol family and has attracted attention in the research concerning chemoprevention and chemotherapy (13–15). Recently, researchers have found that (S)Rh2 exhibits anticancer functions and inhibits the growth and induces the apoptosis of various cancer cell lines, including leukemia cells (10,16–20). Evidence has proven that (S)Rh2 displays a marked inhibitory effect on leukemia cells, although its specific molecular mechanism is not well understood. Moreover, the Wnt pathway is apparently related to tumor progression. Therefore, we hypothesized that there may be some correlation between (S)Rh2 and the Wnt pathway.
The Wnt signaling pathway plays an important role in embryogenesis and shows little or no activity in fully differentiated cells (21). Self-renewal, proliferation and differentiation are tightly controlled during normal hematopoiesis to ensure lifelong hematopoietic stem cell homeostasis and blood production...