The Role Of Endoplasmic Reticulum Stress In Curcumin Against The Xenograft Tumor Of Liver Cancer In Nude Mice:Potential Mechanisms

Objective:The study was designed to evaluate the effect of natural plant compound,curcumin,on the growth of subcutaneous xenograft tumor of human hepatocellular carcinoma SMMC-7721 cells in nude mice,and explore its underlying mechanisms of endoplasmic reticulum stress.Methods:1.SMMC-7721 cells were injected into nude mice subcutaneously to establish the xenograft tumor model of human hepatocellular carcinoma.All of the nude mice bearing tumor were randomly divided into four groups,including low,medium and high dose curcumin treatment groups and the control group.2.All mice in experimental groups were administrated with curcumin by intraperitoneal injection according to the dose(10 mg·kg^-1,50 mg·kg^-1 and 100 mg·kg^-1),while the control group was only injected with physiological saline solution of equal volume.3.The growth status of all the nude mice was under observation and recorded.The body weight and tumor length and width of nude mice were measured and recorded every other day.4.After 16 days,all nude mice were anesthetized with 3%chloral hydrate solution,and the serum was collected to measure the liver function index.The xenograft tumor tissue was separated and weighed and then the tumor growth inhibition rate of every group was calculated.Morphological characteristics of the xenograft tumors of each group were observed by HE staining.5.The expression of endoplasmic reticulum stress-related proteins and apoptosis proteins were analyzed by application of Western blot assay and immunohistochemical staining.Results:1.The xenograft tumor models of liver cancer in nude mice was successfully prepared and the tumor formation rate is 100%.After dosing,the growth state of nude mice in all groups was good,and the body weight gain was similar in all groups.2.With increasing of curcumin dose,the size of xenograft tumor became smaller and the tumor mass was reduced as well.The tumor inhibition rates were 35.3%,45.7%and 54.7%in the group of low,medium and high dose curcumin,respectively.The inhibition effect was markedly,and there was no obvious hepatotoxicity.3.In the control group,the structure and shape of tumor cells were relatively complete,and no obvious necrotic area was observed in the tumor tissue.However,different degrees of necrosis appeared in each curcumin treatment group,and the higher curcumin dose,the more obvious necrosis.4.Western blotting showed that the expression of GRP78,IRE1,p-PERK,p-e IF2αand CHOP in the curcumin treated groups were dose-dependently higher than those in the control group.Compared with the control group,the expression of Bcl-2 was significantly decreased and the expression of Cleaved Caspase-3 protein was up-regulated in all curcumin treated groups.5.The results of immunohistochemical staining showed that the positive expressions of GRP78,IRE1 and p-e IF2αin the curcumin treated group were obviously higher than those in the control group.Conclusion:As one of natural plant ingredients,curcumin is capable of inhibiting the growth of transplanted liver cancer in nude mice markedly and can up-regulate the level of endoplasmic reticulum stress-related proteins.Therefore,it may be implicated that endoplasmic reticulum stress pathway is the target of curcumin against liver hepatocellular carcinoma.