TDO2 Promotes Malignant Behavior In Nasopharyngeal Carcinoma By Activating The KYN-AHR Signaling Pathway

Objective: To investigate the effect of tryptophan-2,3-dioxygenase 2(TRyptophan-2,3-dioxygenase2,TDO2)on the biological behavior of nasopharyngeal cancer cell lines(CNE-2Z and HNE-1)and its molecular mechanisms.Methods: Analysis of the expression status of the TDO2 gene in different cancers or specific cancer subtypes through an online database.Culture of human normal nasopharyngeal mucosal epithelial cell lines NP69,nasopharyngeal cancer cell lines5-8F,CNE-2Z,and HNE-1.In the experiment,CNE2 Z and HNE-1 cells were transfected with TDO2 interference sequences and negative control sequences as si-TDO2 group and NC group,respectively.Real-time real-time PCR(q RT-PCR)was used to detect the relative expression level of m RNA of TDO2.Cell counting kit(CCK-8)was used to detect cell viability,and cell colony cloning experiments were used to detect the number of colonies.Transwell method and cell scratch assay to detect cell migration ability;Western blot assay detected the relative expression of epithelial mesenchymalization(EMT)-related proteins E-cadherin,N-cadherin and Vimentin and apoptosis-related proteins Bax and Bcl-2 in nasopharyngeal cancer cells.Through the STRING online database,a PPI network centered on the TDO2 gene was constructed.The TIMER2 tool plotted the corresponding heat maps of KYNU and AHR in different cancer types of TDO2.The GEPIA2 tool analyzed the correlation between TDO2 expression level and KYNU and AHR expression.Western blot experiments detected the relative expression of pathway proteins KYN and AHR.Results: Compared with normal nasopharyngeal mucosal epithelial cells NP69,the relative expression of m RNA of TDO2 in CNE-2Z and HNE-1 cells was significantly upregulated(P<0.001).Compared with the NC group,the cell survival rate of the si-TDO2 group was reduced,(P<0.05),Compared with the NC group,the number of cell shifts was smaller and the migration index was smaller(P<0.05),compared with the NC group,the relative expression levels of N-cadherin and Vimentin proteins in the EMT-related proteins of the si-TDO2 group were reduced,the relative expression levels of E-cadherin protein increased,the relative expression level of Apoptosis related protein Bax protein increased,and the relative expression of Bcl-2protein decreased(P < 0.05).TDO2 gene and KYN gene may interact in gene expression and gene co-production.The corresponding heat maps of KYNU and AHR of TDO2 in different cancer types drawn by the TIMER2 tool showed that there was a positive correlation between TDO2 and the above two genes.The GEPIA2 tool analyzed the correlation between TDO2 expression level and KYNU and AHR expression,and showed that TDO2 expression level was positively correlated with KYNU and AHR expression.Compared with the NC group,the relative expression of KYN and AHR proteins related to the KYN-AHR pathway in the si-TDO2 group decreased(P<0.05).Conclusion: TDO2 can promote the proliferation and migration ability of CNE-2Z and HNE-1 cells of nasopharyngeal cancer cell lines,and inhibit apoptosis,and the mechanism may be regulated by the KYN-AHR pathway.