| Background and Purpose On a global scale,gastric carcinoma(GC)is still the fourth most common malignancy and the second leading cause of cancer-related death.Surgical resection remains the foremost curative treatment.However,most of the patients are diagnosed at an advanced stage when surgery is no longer feasible.In this way,cytotoxic chemotherapy has been proved to be an effective treatment.Nevertheless,drug resistance and therapy-associated side effects remain major problems.Thus,more effective antitumor drugs with fewer side effects for the treatment of gastric cancer are needed.A diverse range of polyphenols,including flavonoids,stilbenes and proanthocyanidins,have confirmed the capacity to selectively inhibit the growth of tumor cells.Other than cancer fighting potential,flavonoids have a wide range of other biological activities,including antioxidant ability and anti-inflammatory capacity.Kaempferol is an important member of the flavonoids,which is often found in tea,broccoli,apples,strawberries,and beans.It has received much attention due to its anticancer potential,preferable biocompatibility and few side-effects.Plenty of research have documented that kaempferol can inhibit the proliferation,angiogenesis and metastasis,induce cell cycle arrest and promote apoptosis in a wide variety of human cancer cell lines,but the potential role of this phytochemical in gastric cancer treatment has not yet been evaluated.Therefore,we investigated the therapeutic potential and molecular mechanisms of kaempferol on gastric cancer cells in vivo and in vitro.Methods Gastric cancer cell lines(MKN28 and SGC7901)were taken as the object of the present study to explore the role of kaempferol in the growth of gastric cancer.Firstly,MTT assays were performed to detect the effects of kaempferol on the cell viability of gastric cancer cells.Secondly,flow cytometry were used to investigate the effects of kaempferol on cell cycle and apoptosis.Thirdly,we dected the activity of PI3K/AKT signaling pathway,ERK signaling pathway,and the expression of its downstream proteins related to cell cycle and apoptosis after the treatment of kaempferol.Finally,SGC7901 cells were injected into the flanks of 4-week-old athymic mice to establish the subcutaneous tumor model.When the tumor volume reached 100 mm~3,kaempferol(20 mg/kg)was administered i.p.for 3 weeks daily.Body weight,liver weight,and spleen weight were observed.Then,the mice were sacrificed to obtain the snap-frozen and paraffin-embedded tumor tissue for immunohistochemistry and western blot analysis to further confirm the results from in vitro experiments.Results The present study showed that kaempferol significantly supressed the proliferation of MKN28 and SGC7901 cell lines in a time-and dose-dependent manner.Moreover,it did not influence the proliferation of normal gastric GSE-1 cells when treated with even a concentration at 120?M.Kaempferol also arrested gastric cancer cells at the G2/M stage and decreased the expression of cyclinB1,Cdk1 and Cdc25C.We deduced that kaempferol might induce cell cycle arrest by decreasing the activity of Cdk1/cyclin B kinase complex.Otherwise,kaempferol promoted the cell apoptosis of gastric cancer cells and decreased the level of Bcl-2 concomitant with an increase in Bax expression,which resulted in the activation of caspase-9,caspase-3,and PARP.Moreimportantly,thepan-caspaseinhibitorZ-VAD-FMKdecreased kaempferol-mediated apoptosis and activation of caspase-3.These results revealed that kaempferol induced the apoptosis of gastric cancer cells partly through a mitochondrial cell death pathway.Kaempferol-treated cells also lead to decrease in p-AKT,p-ERK and COX-2.Finally,we found kaempferol significantly supressed the growth of the tumor xenografts with no marked change in liver,spleen or body weight,suggested that kaempferol might be an effective anti-tumor drug with less side effects.Conclusions The present paper showed that kaempferol could significantly inhibit the proliferation of MKN28 and SGC7901 cell lines.However,we detected no significant inhibition in the normal gastric epithelial cell line in our experimental dose.Otherwise,we found significant apoptosis and G2/M phase cell cycle arrest following the treatment of kaempferol.More importantly,we also observed that kaempferol could inhibit the growth of the tumor xenografts while causing no marked effects on liver,spleen or body weight.The expression levels of G2/M cell cycle regulating factors,cyclinB1,Cdk1 and Cdc25C,were significantly reduced.In addition,kaempferol treatment dramatically decreased the level of Bcl-2 concomitant with an increase in Bax expression,and resulted in an upregulation of cleaved-caspase 9 and cleaved-caspase 3,which promoted PARP cleavage.Kaempferol-treated cells also lead to decrease in p-AKT,p-ERK and COX-2.The present study has provided a strategy that kaempferol being a therapeutic agent for gastric cancer. |
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