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Background: Tumor hypoxia has been frequently detected in nasopharyngeal carcinoma (NPC) and is intently associated with therapeutic resistance. The aim of the study is to establish a clonogenically stable hypoxia-inducible dual reporter model and apply it to investigate the effect of tumor hypoxia on DNA double strand break (DSB) and synergistic effect of irradiation in combination with chemotherapy or targeted therapy. Methods: The plasmid vector consisting of hypoxia response elements to regulate HSV1-TK and GFP genes, was constructed and stably transfected into human NPC cells. The expected clone was identified and validated by in vivo and in vitro assay. DSB repair was measured by γH2AX foci formation. Tumor growth delay assay and spatial biodistribution of various biomarkers was designed to investigate the anti-tumor effect. Results: The system has the propensity of high expression of reporter genes under hypoxia and low to no expression under normoxia. Intratumoral biodistributions of GFP and classic hypoxic biomarkers were identical in poor-perfused region. Upon equilibration with 10% O2, the xenografts showed higher expression of hypoxic biomarkers. Cisplatin radiosensitized SUNE-1/HRE cells under hypoxia by suppressing DSB repair while the addition of PI3K/mTOR inhibitor further enhanced the anti-tumoral therapeutic efficacy. Combination of IR, DDP and NVP-BEZ235 exhibited most effective anti-tumor response in vivo. These observations underline the importance of dual reporter model for imaging tumor hypoxia in therapeutic study. Conclusions: Our preclinical model enables the investigation of heterogeneous tumor hypoxic regions in xenograft tissues and explores the treatment efficacy of combinations of various therapeutic approaches to overcome hypoxia.
RESUMEN
OBJECTIVE: There is a lack of effective biomarkers for predicting the distant metastasis in nasopharyngeal carcinoma (NPC). We aimed to explore the expression of FAP+Cancer-associated fibroblasts (CAFs) derived CXCL1 in NPC and its predictive values for distant metastasis and correlation with PD-L1 expression. MATERIALS AND METHODS: A total of 345 patients with locoregionally advanced NPC were retrospectively enrolled (the training cohort: the validation cohort = 160:185). Co-expression of CXCL1 and FAP and the expression of PD-L1 were detected by multi-immunofluorescence staining and immunohistochemistry, respectively. The primary end-point was distant metastasis-free survival (DMFS). The Kaplan-Meier method was used to calculate the survival. The Cox proportional hazards model was used to assess prognostic risk factors. RESULTS: A novel CXCL1+_FAP+ phenotype in CAFs was identified in NPC and then used to divide patients into low and high risk groups. Both in the training cohort and validation cohort, patients in the high risk group had poorer DMFS, overall survival (OS), progression-free survival (PFS) and locoregional relapse-free survival (LRFS) than patients in the low risk group. Multivariate analysis revealed CXCL1+_FAP+ phenotype was an independent prognostic factor for DMFS, OS, PFS and LRFS. Further results showed patients in the high risk group had higher PD-L1 expression than those in the low risk group. CONCLUSION: Our study showed CXCL1+_FAP+ phenotype in CAFs could effectively classified locoregionally advanced NPC patients into different risk groups for distant metastasis and might be a potential biomarker for anti-PD-1/PD-L1 immunotherapy.