The low expression of the proteins LTA4H, PGK1, NDRG1, COL6A1, and ITGAV in the saliva samples was associated with lymph node metastasis and advanced clinical staging (crosstabulation and chi-square test, P value < 0.05, Supplementary Data 32). This evidence concerns the gene PGK1 and metastatic malignant neoplasm in the lymph nodes.