VIP and lung cancer: Six metabolites, such as D-lyxose, galactinol, urea, D-allose, D-glucose, and D-mannose, were upregulated (all VIP > 1, FC > 1, and p < 0.05), while 5 metabolites, namely lactic acid, glycolic acid, D-mannitol, palatinitol, and maltitol, were down-regulated (all VIP > 1, FC < 1, and p < 0.05), defined on the basis of VIP score of lung cancer (Fig. 2 panel E).