| [Background]Nasopharyngeal carcinoma(NPC) is a common malignant tumor of the head andneck,and its main clinical treatment are radiotherapy and chemotherapy. Although withthe development of intensity-modulated radiotherapy techniques，the cure rate of NPC hasbeen increased and its side effects has been reduced, the5-year overall survival rate ofpatients with advanced stage of the cancer is still not ideal, and the side-effects afterradiotherapy still can not be neglected, and the multidrug risistance(MDR) afterchemotherapy is still unavoidable. It’s imperative to find a new kind of anticancer drugswith high efficiency and fewer side effects Epigallocatechin-3-gallate (EGCG),the maincomponent of green tea polyphenols,is a kind of natural compound with high efficiency inanti-cancer and low toxicity in normal cells.Therefore, it is not only significant to studythe pharmacological mechanism of EGCG against NPC,but also promising for clinicalpractice.A lot of studies have confirmed that EGCG can inhibit tumor cells proliferation andpromote apoptosis of tumor cells [1-3].But its mechanism still unclear. The Telomerase isa DNA polymerase with reverse transcriptase activity, it is pivotal for cell growth. Most ofthe human somatic cells donn’t or have low telomerase activity, their division times islimited,and the cells go towards aging and apoptosis finally. As for a small number ofhuman somatic cells,some germline cells and the majority of tumor cells(approximately90%) thetelomeres will not be shortened due to replication, and cells go toimmortalization. Telomerase contains a reverse transcriptase protein (human of telomerasereverse transcriptase activity of the reverse transcriptase, hTERT) and telomerase RNA(TERC/TR). hTERT is the catalytic subunit of telomerase, also a key rate-limiting factorof telomerase activation. this paper will explore the impact of EGCG on telomerase genehTERT and its expression of CNE2At the cellular and molecular levels in NPC cell line,to provide theoretical and research basis for investigating the mechanism ofbroad-spectrum natural green tea polyphenol EGCG resistance to nasopharyngealcarcinoma in vivo and in vitro and for the development of new drugs of EGCG. 【objective】Through the cell biology and molecular biology experiments, to explore theanti-cancer mechanism of the natural green tea polyphenols EGCG to nasopharyngealcarcinoma cell line CNE2in vitro,to provide theoretical and research basis for thedevelopment of new drugs of EGCG.【methods】1CCK-8test to detect the effect of EGCG on proliferation of NPC cell line CNE2.2. flow cytometry experiments to test the influence of EGCG on the cell cycle andapoptosis of NPC cell line CNE2.3.RT-PCR experiments to test the influence of EGCG on hTERT mRNA level of NPCcell line CNE2.4. Western blot experiments to test the influence of EGCG on hTERT and c-Mycexpression of NPC cell line CNE2.【results】1. EGCG significantly inhibited proliferation of NPC cell line CNE2,and its inhibitionpresented time and drug concentration dependence.2.EGCG blocked cell cycle progression of CNE2, made G0/G1phase ratio increase（P<0.001），S phase ratio reduce（P<0.002）. The cell cycle block was time-dependencein low concertration group (100ug/mL), with increased concentration and extension ofresponse time，time-dependence of cell cycle block was not clear, but the cell apoptosisrate was increased.3. EGCG promoted cell apoptosis of CNE2,with extension of response time,theapoptosis rate increased (P<0.001) and presented time-dependence.4. EGCG downregulated the mRNA expression of hTERT in CNE2(P<0.001).5. EGCG downregulated hTERT and c-Myc expression in CNE2。 【conclusion】EGCG can inhibit proliferation and promote apoptosis of NPC cell line CNE2, Themechanism may be the downregulation expression of c-Myc by EGCG and thedownregulation transcription level of hTERT gense by c-Myc,so as to reduce the proteinexpression of the telomerase hTERT. |
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