Apigenin Induces Apoptosis of Human Colorectal Cancer CL187 Cells via PI3K/Akt and MAPK Signaling Pathways / 中国实验方剂学杂志

ABSTRACT

ObjectiveTo study the effect of apigenin on the proliferation and apoptosis of human colon cancer CL187 cells and the underlying mechanisms. MethodHuman colorectal cancer CL187 cells were treated with different concentrations of apigenin （0， 30， 45， 60 mg·L-1） according to the results of the preliminary experiment. The proliferation of CL187 cells was detected by methyl thiazolyl tetrazolium （MTT） and colony formation assays， and the apoptosis was observed via Hoechst 33258 staining. Real-time fluorescence quantitative PCR was conducted to determine the mRNA levels of cysteine protease-3 （Caspase-3）， B-cell lymphoma-2 （Bcl-2）， and Bcl-2-associated X protein （Bax） in the CL187 cells treated with apigenin. Western blot was employed to measure the protein levels of Caspase-3， Bcl-2， and Bax associated with apoptosis， protein kinase B （Akt） and phosphorylated Akt （p-Akt） in phosphatidylinositol 3-kinase/protein kinase B （PI3K/Akt） pathway， and extracellular signal-regulated kinases 1/2 （ERK1/2）， p-ERK1/2， c-Jun N-terminal kinase （JNK）， p-JNK， p38 mitogen-activated protein kinase （MAPK）， and p-p38 MAPK protein in MAPK pathway. ResultCompared with the blank group， the apigenin groups had low cell survival rates and high inhibition rates on cell proliferation （P<0.01）. Apigenin decreased the cell clone number and clone formation rate， and increased the inhibition rate on clone formation （P<0.01）. After CL187 cells were treated with different concentrations of apigenin for 48 h， typical apoptosis characteristics such as nuclear pyknosis， chromatin condensation， and enhanced fluorescence reaction were observed. Compared with blank group， 45， 60 mg·L-1 apigenin treatments down-regulated the mRNA level of anti-apoptotic gene Bcl-2 （P<0.01） and all the apigenin treatments up-regulated those of the pro-apoptotic genes Bax and Caspase-3 （P<0.05， P<0.01）. Similarly， apigenin treatments down-regulated the protein level of Bcl-2 （P<0.05， P<0.01） and up-regulated those of Caspase-3 （P<0.05， P<0.01） and Bax （P<0.01， 45， 60 mg·L-1）. The blank group had higher protein level of Akt than the 60 mg·L-1 apigenin group （P<0.01）， higher protein levels of p-Akt， ERK1/2， and p-ERK1/2 than the 45， 60 mg·L-1 apigenin groups （P<0.01）， and higher protein levels of JNK and p-JNK than the apigenin groups （P<0.05， P<0.01）. Compared with blank group， 60 mg·L-1 apigenin up-regulated the protein level of p38 MAPK （P<0.05）， and all the apigenin groups up-regulated that of p-p38 MAPK （P<0.01）. Furthermore， apigenin lowered the p-Akt/Akt ratio （P<0.05， P<0.01） and p-ERK1/2/ERK1/2 ratio （P<0.01）， while it increased the p-JNK/JNK ratio （45， 60 mg·L-1； P<0.05， P<0.01） and p-p38 MAPK/p38 MAPK ratio （P<0.05， P<0.01）. ConclusionApigenin can inhibit the proliferation and promote the apoptosis of CL187 cells by inhibiting the PI3K/Akt signaling pathway and regulating the expression of proteins in the MAPK signaling pathway.