Expression Patterns And Prognostic Values Of Nrf2 And Keap1 In Nasopharyngeal Carcinoma

Objective: Looking for the prognosis of patients with nasopharyngeal carcinoma radiotherapy molecular markers.Explore Nrf2-Keap1 signaling pathways associated with nasopharyngeal carcinoma radiotherapy resistance whether,for nasopharyngeal carcinoma radiotherapy-targeted gene therapy to lay the theoretical foundation,and for the next step of nasopharyngeal cancer molecular targeted therapy provides effective intervention targets.Methods: We retrospectively searched the patient database of the Department of Otolaryngology,Zhangjiagang First People's Hospital,Affiliated Hospital of Soochow University,Suzhou,China,and identified patients with NPC who were treated from January 2005 to December 2013.A total of 108 patients with biopsy-proven nonkeratinizing squamous cell carcinoma-undifferentiated type(NKSCC-UD)(Word Health Organization types of II or III)with available biopsy specimens for tissue microarray(TMA)construction were eligible for the study;no other malignant diseases;no distant metastases;karnofsky performance score ?70;without RT or CRT before biopsy.All patients signed written informed consent,and our study was approved and supervised by the ethical committee of the Zhangjiagang First People's Hospital,and the study followed the Declaration of Helsinki.Results: By using IHC to examine the protein expressions of nuclear Nrf2 and cytoplasmic Keap1 in NPC tissues,we found that the high rates of nuclear Nrf2 and cytoplasmic Keap1 expressions were 36.1%(39/108),58.3%(63/108),respectively.Representative staining patterns of Nrf2 and Keap1 are shown in Figure 1.Nrf2 and Keap1 expressions were localized in both nuclei and cytoplasm in NPC cells,but Nrf2 mainly in nuclei.Statistical analyses revealed that nuclear Nrf2 or cytoplasmic Keap1 expression had no significant association with clinicopathological features including age,gender,tumor T stage,lymph node(LN)metastasis,clinical stages,and differentiation had no significant association.The overall 5-year DFS and OS rates were 57.4% and 70.2%,respectively.The 5-year DFS rate was 59.4% in the low nuclear Nrf2 expression group,and 53.8% in the high nuclear Nrf2 expression group.The 5-year DFS rate was 42.2% in the low cytoplasmic Keap1 expression group,and 68.2% in the high cytoplasmic Keap1 expression group.The 5-year OS rate was 70.8% in the low nuclear Nrf2 expression group,and 69.2% in the high nuclear Nrf2 expression group.The 5-year OS rate was 55.6% in the low cytoplasmic Keap1 expression group,and 80.9% in the high cytoplasmic Keap1 expression group.The log-rank test showed that nuclear Nrf2 expression level didn't correlate with DFS(P=0.595,Fig.2A)and OS(P=0.496,Fig.2B).However,NPC patients with high level of cytoplasmic Keap1 expression had longer DFS(P=0.016,Fig.2C)and OS(P<0.001,Fig.2D).Univariate and multivariate Cox proportional hazards regression analyses were performed to evaluate whether nuclear Nrf2 and cytoplasmic Keap1 expressions serve as prognostic markers in NPC patients treated with RT or CRT.As shown in Table 3,For univariate analysis,we found that Keap1 expression(Hazard ratio [HR]=0.544,95% confidence interval [CI]: 0.329-0.900;P=0.018)was significantly correlated with DFS;while T stage(HR=1.943,95% CI: 1.114-3.390;P=0.019),clinical stage(HR=4.673,95% CI: 1.135-19.242;P=0.033),and Keap1 expression(HR=0.338,95% CI: 0.190-0.599;P<0.001)were significantly correlated with OS.Multivariate analysis indicated that Keap1 expression was an independent prognostic factor for DFS(HR=0.544,95% CI: 0.329-0.900;P=0.018)and OS(HR=0.362,95% CI: 0.204-0.644;P=0.001).Conclusion: In summary,the present study retrospectively investigated the clinical values of Nrf2 and keap1 expressions in NPC tissues for the first time.We found that nuclear Nrf2 or cytoplasmic Keap1 expression had no significant association with clinicopathological features,and elevated Keap1,but not Nrf2,is an independent prognostic factor for DFS and OS in NPC.In order to verify the usefulness of this biomarker,further studies of larger patient scale are required to validate these findings.Considering the possible role of Nrf2 and Keap1 in radioresistance/chemoresistance,in our next project,experiments on NPC cell lines' survival in response to RT/CRT by elevating Keap1and/or decreasing Nrf2 will be explored.