Abstract 2767: Expression of defensin-associated genes may be correlated with lymph node metastasis of early stage tongue cancer

Abstract

Abstract OBJECTIVES: Appropriate patient selection for elective neck dissection in N0 tongue cancer has been controversial, while there has been no genetic consideration so far. We aimed to analyze genetic difference between early and late cervical lymph node metastasis in oral tongue cancer patients using the Seoul National University Hospital (SNUH) cancer cohort and cancer genome atlas (TCGA) data, and to suggest genetic background for choosing eligible patient for elective neck dissection. METHODS: A total of 35 cases with RNAseq in SNUH cancer cohort with tongue cancer were also enrolled in this study. To investigate gene expression in early cervical lymph node metastasis, genomic data of following 2 groups was compared; 1) N0 group: T1/2 and N0, 2) N+ group: T1/2 and N+. Differentially expressed genes (DEGs) were extracted using R and limma package in bioconductor program. Gene ontology and pathway enrichment analysis were performed using DAVID online tool. Immune cell infiltration was analyzed using CIBERSORT online program. Additionally, 70 cases with matched RNAseq data of primary tumor and clinical TCGA data were analyzed to validate the role of DEGs. RESULTS: N0 and N+ groups showed no difference in age, gender, size and thickness of tumor, and nearest resection margin. In addition, there was no significant difference in 22 types of immune cell infiltration. A total of 51 DEGs were identified, and 14 genes were significantly upregulated and 37 genes were significantly downregulated (p<0.01, fold-change >2). Significant genes were PLA2G4D, NELL2, PCOLCE2, PI3, and PLA2G3. On KEGG pathway analysis, calcium, muscle contraction, and arachidonic acid metabolism-related pathway was significantly correlated. The most significant difference was found in 6 genes as follows; DEFB4A, SPRR2B, DEFB103B, SPRR2G, DEFB4B, FAM25A.DEFB which was the most significantly difference in expression was associated with ‘antibiotic’, ‘antimicrobial’, ‘beta defensing type’, defense reponse to bacterium’, and ‘defensin’. In TCGA data, DEFB4A and DEFB103B were more highly expressed in N0 group than N+ group, although it did not attain significant significance. CONCLUSIONS: Defensin (DEFB4A, DEFB103B, DEFB4B) may be a novel biomarker for early regional metastasis in T1/2 tongue cancer. Considering that defensin can be detected in saliva, simple saliva test for prediction of metastasis can be developed in the future. Note: This abstract was not presented at the meeting. Citation Format: Doh Young Lee. Expression of defensin-associated genes may be correlated with lymph node metastasis of early stage tongue cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2767.