KEGG pathway analyses further indicated that the upregulated DE mRNAs were enriched in 30 pathways including ECM-receptor interactions, focal adhesion, and the PI3K-Akt signaling pathway (Fig. 3C), while downregulated DE mRNAs were enriched in the nicotine addiction, neuroactive ligand-receptor interaction, and retrograde endocannabinoid signaling pathways, among others (Fig. 3D). The gene discussed is AKT1; the disease is nicotine dependence.