Inhibitory Effect Of Platycodin D On Human Colonic Cancer Cell Proliferation

Background:Cancer is one of the leading cause of death in adults.DNA damage caused by various environmental or genetic carcinogenic factors in together or sequential ways activate proto-oncogene or inactivated cancer suppressor genes, causes the apoptosis resistance or uncontrolled growth cycle, make the target cells that come to malignant transformation, which is the main cause of malignant tumor. The morbidity and mortality of carcinoma is rising year by year due to the change of living environment, which already becomes one of the major diseases that threat human health.Colorectal Carcinoma, known as CRC, is one of the most common malignancies in nowadays, chemotherapy is the main treatments of colon cancer as most of the patients diagnosed with colon cancer are already in the middle or late stages and lose the opportunity of surgical treatment, which means little because of can’t taken away completely as well as distant metastasis. But as the chemotherapy methods in clinical application nowadays have some shortages such as serious adverse reaction, Expensive price, Multiple drug resistance, it’s of great significance to find anti-cancer drugs with high efficiency and low toxicity to improve the survival rate of middle-late patients.We have already proved the fact in early research that, PD has an effect in inhibiting the proliferation of chronic myeloid leukemia K562cells and lung adenocarcinoma A549cell. But we have little data with whether PD can inhibit the proliferation of human colonic cancer SW620cell and the research of PD’s molecular mechanism. So we cultured human colonic cancer SW480. SW620、HCT116、HT29cell in vitro as a model to explore the effect and mechanism of PD that inhabits the cell proliferation, which can provide experiment basis for the clinical application value of PD.Objective:This study is aimed to study the effect of platycodin D (PD) on human colonic cancer cell proliferation, and explore whether it inhibit the cell proliferation by mechanism of cell-cycle arrest and inducement of cell apoptosisMethods:We cultured human colonic cancer SW480、SW620、HCT116、HT29cell in vitro, and observed the effect of PD in different levels on proliferation of cells in24/48hours by MTT assay.The effect of PD on cell cycle distribution in24hours was evaluated by flow cytometry and the effect of PD on expression of cyclinDl, CDK6and c-myc was detected by Western blot.The effect of PD on apoptosis rate after48hours was evaluated by Annexin V-FITC/PI double staining, and the expression Level of apoptosis associated proteins(caspse3, PARP) was detected by Western blot. Western blot analysis of the effect of PD on the expression of phosphorylation MAPK.Results:Compared with the control group, the cell proliferation of human colonic cancer cell was inhibited by PD in a dose-dependent manner. After cells were treated with PD (5,10,15,20μM) for24hours, the survival rates of SW620cells were96.2%±2.3%,87.5%±4.9%,67.2%±4.8%and52.6%±3.7%. The survival rates of cells were92.1%±5.4%,73.2%±4.1%,43.2%±3.2%and31.5%±2.1%when after48hours.After cells were treated with PD (15,20μM) for24hours, the proportions of cells in G0/G1phase were72.83%±5.26%and76.82%±5.83%respectively, while the control group cells was56.78%±4.92%, p<0.05.And the expressions of cyclinD1, c-myc and CDK6were reduced obviously.Compared with the control group cells being8.9%±5.7%, the apoptotic rates were increased significantly being19.5%±5.1%,35.8%±5.3%and43.8%±4.0%respectively after cells were treated by PD (10,15,20μM) for48hours.And the expression of pro-caspase3and PARP was reduced. After cells were treated with PD (10,15,20μM) for24hours, the expressions of pERKl/2were reduced obviously, and pJNK, pp38increased significantly.Conclusion:PD inhibits the growth of colon cancer cells. PD could inhibit the growth of SW620cell by blocking cells in the G1phase through regulating the expression of cyclinD1, c-myc and CDK6and thus inducing the apoptosis by cell cycle arrest, and associated with activation of JNK, p38, dephosphorylation of ERK1/2.