TOP2A and nicotine dependence: In the high TOP2A subgroup, fat digestion and absorption, linolenic acid metabolism, maturity onset diabete of the young, the nicotine addiction and steroid biosynthesis were significantly enriched, whereas were significantly Aminoacyl-tRNA biosynthesis non-homologous end-joining, one carbon pool by folate, other glycan degradation and Protein export enriched in the low TOP2A subgroup (Fig. 8C).