Various PET/CT based metabolic tumor volume (MTV) was found to influence the prognosis of non-metastatic nasopharyngeal carcinoma. The proteomic analysis of primary tumor was compared for 18FDG-PET/CT based MTV in non-metastatic nasopharyngeal carcinoma. We tried to find the potential biomarker related to MTV.
We respectively analyzed 110 patients with PET/CT confirmed non-metastatic nasopharyngeal carcinoma at our institution. MTV of primary tumors was defined with SUV2.5.The ROC curve was portrayed with treatment failure events of patients.With the optimal cut-off point of MTV,another 25 nasopharyngeal carcinoma patients were divided into two groups to compare the primary tumor proteomics.Proteomic analysis was conducted with the combination of iTRAQ and nano-RPLC-MS/MS.We analyzed the previous tumor specimens(97/110) to verify the potential biomarker found by proteomics.
The area under the ROC curve (AUC) was 0.726. And the best cut-off point for MTV was 9.88 ml (≈10 ml). MTV ≤10 ml appeared a favorable disease-free survival (DFS, 93.5% vs 81.3%, P = 0.035). A total of 7913 proteins were identified with proteomics, of which 360 had significant differences. In MTV>10ml group, the expression of 244 proteins was up-regulated and the other 116 was down-regulated. According to GO analysis and clustering, these proteins were mainly localized in organelles (34%), cytoplasm (20%), extracellular matrix (13%), and plasma membrane (10%). They were involved in many biological processes and molecules features. KEGG suggested that these differential proteins participated in metabolism, migration and inflammation-related pathways. The PPI interaction network showed that the core proteins were mainly implicated in protein phosphorylation, signal transduction and cell adhesion. Higher TRIM29 protein expression was found in the MTV>10ml group by immunohistochemistry (x2=19.041, P < 0.001).
With proteomic comparison based on MTV, the differential proteins were closely related to tumor cell growth, migration, metabolism and immunity. Also, patients with MTV ≤10 ml had a favorable DFS. Lower expression of TRIM29 found in this group might be considered as a promising prognostic biomarker.
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