The Investigation On The Induced Differentiation Of Human Hepatocarcinoma SMMC-7721 Cells By Abscisic Acid

OBJECTIVE To induce cancer cells to differentiate into normal cells is a new branch of Oncotherapy, and has become more and more concerned in this field. Presently, the common differentiation-inducing agents still have various side effects, while lack high efficiency of induction. Additionally, there has been lots of investigation on non-solid tumor, but not satisfying. Thus, it is a key to search for non-toxic and natural origin substances that can induce the differentiation of cancer cells efficiently, especially for the therapy of solid tumor, which needs futher studies and researches to resolve. Derived from natural origin phylohormone, Abscisic Acid (ABA) is a "anti-hard environments inducing factor" that can induce the resistance in plants against hard environments, such as drought resistance, cold resistance, disease resistance and salt endurance. It is reported that ABA can inhibit the proliferation of mice leukemia L5178Y cells. However, it remains unclear that ABA can induce differentiation of solid tumor, such as hepatocarcinoma cells. In this study, the differentiation-inducing effects of ABA on SMMC-7721 hepatocarcinoma cells and the differentiation mechanism were investigated. This study may provide helpful theoretical and experimental envidence to develop new methods for hepatocarcinoma therapy. METHODS The effects of ABA were investigated in vitro and in athymic mice subcutaneous-injected with SMMC-7721 hepatocarcinoma cells by using light microscope, electronic microscope, immunohistochemistry, Flow Cytometer, and RT-PCR. Then we measured growth curves of SMMC-7721 cells, cell proliferation index, cell inhibition ratio, cell cycle, the rate of colony forming in SMMC-7721 hepatocarcinoma cells, the microstructure of tissues and cells, the expression level of Alpha fetoprotein(AFP), mtp53, bcl-2, Cyclin D, and Ki-67, and the mRNA expression level of telomerase to evaluate the differentiation-inducing effects of ABA on SMMC-7721 hepatocarcinoma cells. RESULTS ABA inhibited obviously the proliferation of SMMC-7721 hepatocarcinoma cells, decreased the the rate of colony forming in cancer cells, which were made to stay in G₀/G₁ stage. Furthermore, ABA significantly deduced the expression level of Alpha fetoprotein(AFP), mtp53, bcl-2, Cyclin D, and Ki-67, while the mRNA expression level ofmt p53 and hTERT obviously decreased with the time. In addition, ABA had a significantly inhibiting effects on the proliferation of tumor subcutaneous-injected in athymic mice. In a word, ABA can inhibit the proliferation of SMMC-7721 hepatocarcinoma cells in vitro and in vivo. The differentiation-inducing effects of ABA were similar to ABA+ HMBA groups and HMBA group, without statistical significance among three groups. CONCLUSIONS ABA has the effects of inhibiting the proliferation and...