Inhibition Of Human Nasopharyngeal Carcinoma Cell Proliferation And Xenograft Growth In Nude Mice By Laminaria Japonica Polysaccharides

Objective:Nasopharyngeal carcinoma (NPC) is the most prevalent malignant tumors of head and neck in southern China. The main treatment of NPC is radiotherapy supplemented by chemotherapy, which is especially important in patients with advanced NPC. The patient’s quality of life and prognosis is seriously affected by a lot of serious side effects induced by therapeutic dose of chemotherapy drugs. Laminaria japonica polysaccharides(LJP) extracted from kelp is a kind of plant polysaccharides,with various biological activities including anti-tumor activity, improving the immune system and anti-radiation activity. This study aims to evaluate the antitumor activity of Laminaria japonica polysaccharides on human NPC cells in vitro and in vivo,and further to explore the underlying mechanism.Methods:Two human NPC cell lines (HONE1and CNE2) were treated with different concentrations of LJP, and cell proliferation was examined by MTT assays in vitro. The cell apoptosis of LJP-treated HONE1was examined by Annexin V-FITC/PI double staining assay.The tumor models established by the subcutaneous inoculation of NPC cell HONEl into nude mice were used to evaluate the inhibitory action of LJP in vivo. They were randomly divided into five groups:normal control group, DDP therapy group, high, medium and low-dose group. The volume of xenograft tumors and the weight of nude mice were measured every two days. After a two-week treatment of LJP, these nude mice were killed to take out the xenografts, which were then weighed to calculate the inhibition rate(IR).All these data was used to evaluate the inhibitory effect of LJP in vivo. Transmission electron microscopy(TEM) was used to observe changes in the ultrastructure of the NPC cells in xenografts.Results:The anti-proliferative activity of LJP was found in both human NPC cell lines(HONE1and CNE2) by MTT assay. The inhibition ratio was between50%and60%at72h after treatment with320mg/L LJP. Flow cytometry showed that LJP can induce the apoptosis of HONE1. With increased concentration of LJP,the apoptotic rate increased. The apoptosis rate was49.51±1.89%(P<0.01) when treated with320mg/L LJP. Meanwhile, compared with the control group, the growth of xenografts in nude mice was significantly suppressed following the administration of LJP in a dose-dependent manner. The inhibition ratios were33.7%(P<0.05)and47.0%(P< 0.01) when treated with25mg/kg and50mg/kg respectively. However, the inhibition ratio of the12.5mg/kg group was only16.4%(P>0.05). The typical morphological changes in apoptosis were revealed by TEM, including morphological changes of cell shrinkage, chromatin condensation (pyknosis), nuclear fragmentation, cytoplasm vacuolization, plasma membrane blebbing, and formation of discrete apoptotic bodies.Conclusion:Our results indicated that LJP can inhibit the growth of NPC, probably by inducing the apoptosis of NPC cells in vitro and in vivo.