Chibby Suppresses Aerobic Glycolysis And Proliferation Of Nasopharyngeal Carcinoma Via The Wnt/β-catenin-Lin28/let7-PDK1 Cascade

Nasopharyngeal carcinoma(NPC)is a malignant tumor that originates from the nasopharyngeal epithelium and is the third most common malignant tumor in southern China.Due to its high invasive metastasis,approximately 80%of patients with NPC are diagnosed in the advanced stage and lose the opportunity for complete treatment.Currently,radiation therapy is the primary treatment strategy for NPC.However,many patients still have a high distant metastasis rate after receiving radiation therapy,which is easy to relapse and has a poor prognosis.Numerous evidence has indicated that anti-aerobic glycolysis may be a worthwhile approach to treat many types of cancers.It is confirmed that aberrant activation of Wnt/β-catenin is a signaling cascade that mediates the Warburg effect in tumor cells.Chibby,as an endogenous inhibitor of the canonical Wnt/β-catenin signaling pathway,is able to 1)competitively inhibit the binding of β-catenin with Tcf/Lef factor,leading to the inhibition ofβ-catenin-dependent gene activation;2)control the shuttling and subcellular localization of β-catenin between the cytoplasm and the nucleus,inhibiting β-catenin from functioning as a transcriptional coactivator through the interaction with protein 14-3-3.Current research indicates that Chibby is involved in a variety of cell differentiation,fate decisions and tumor development.However,whether there is correlation between Chibby and Wnt/β-catenin-mediated Warburg effect in the progression of NPC still need further studyIn the present study,combined with PCR,WB,CCK8,glucose uptake detection,lactic acid formation measurement,ATP production and O2 consumption rate detection,plasmid transfection,WB and nude mouse xenograft assays,we determined Chibby gene modification and found that Chibby expression is significantly down-regulated in numerous nasopharyngeal carcinoma cell lines(including CNE1,HK-1,HNE1,C666.1,5-8F,CNE-2 and expression in SUNE-1)compared to the immortalized normal nasopharyngeal cell line NP69 which has an opposite expression pattern to nuclear β-catenin.Overexpression of Chibby inhibited,while knockdown of Chibby promoted the proliferation of nasopharyngeal carcinoma cell lines along with the disorder of aerobic glycolysis.Mechanismly,Chibby upregulation completely blunted Wnt/β-catenin-evoked the increase of aerobic glycolysis,cell viability and PDK1 expression.Once knockdowned PDK1,Wnt/β-catenin signaling activation-mediated the promotion of Warburg effect was inhibited.Chibby upregulation-mediated the inhibition role on Warburg effect and cell proliferation were rescued when PDK1 was re-expression.Wnt/β-catenin signaling transduction could regulate the level of PDK1 through affecting Lin28/let-7g.Most importantly,re-expression of PDK1 also significantly rescued the tumor growth phenotype caused by overexpression of Chibby in β-catenin overexpressing cells.It was shown that Chibby and PDK1 were critical for the proliferation of nasopharyngeal carcinoma cells induced by Wnt/β-catenin signaling in in vitro and in vivo.we demonstrated that the inhibition effects of Chibby on proliferation and Warburg effect of nasopharyngeal carcinoma cells were through regulating Wnt/β-catenin-Lin28/let7-PDK1 signal cascade.Eventually,we evaluated the expression pattern of Chibby,β-catenin and PDK1 in human NPC specimens.The data indicated that Chibby was low expression in NPC samples,while β-catenin and PDK1 were significantly upregulated in NPC tissues.More importantly,there was a negative correlation between Chibby and nuclear β-catenin and PDK1,and there was a strong positive correlation betweenβ-catenin and PDK1.Collectively,Chibby might be a tumor suppressor in the process of NPC tumorigenesis,which can inhibited cancer cell proliferation and tumor growth of NPC through limiting the Warburg effect via regulating Wnt/β-catenin-Lin28/let7-PDK1 signaling transduction.Our findings contribute to explore the pathogenesis of nasopharyngeal carcinoma,to find new effective early diagnosis and intervention targets,to improve the treatment of nasopharyngeal cancer and has important social and economic significance.