S100A9 and nicotine dependence: The expression of S100A9 significantly correlated with fatty acid biosynthesis, fructose and mannose metabolism, galactose metabolism, glycine, serine and threonine metabolism, mineral absorption, nicotine addiction, pantothenate and CoA biosynthesis, porphyrin metabolism, starch and sucrose metabolism, systemic lupus erythematosus, yersinia infection.