TP53 and small cell lung carcinoma: In vivo, KEGG pathways “cell cycle,” “DNA replication,” “small cell lung cancer,” “p53 signaling” and “cellular senescence” scored highest among the downregulated, while the upregulated pathways were dominated by “Glutamatergic synapse,” “circadian entrainment,” “morphine addiction,” “neuroactive ligand-receptor interaction” and “oxytocin signaling” (Figure 2B).