To further investigate the mechanism by which MELK affects the tumorigenesis and prognosis of HCC, we performed GSEA and found a positive correlation between MELK and well-known oncogenic pathways, including apoptosis, the mTOR signaling pathway and Notch signaling pathways [27, 28](Fig. 1M), and a negative correlation between MELK and fatty acid metabolism and the PPAR signaling pathway [29], which are important in maintaining the normal function of cells (Fig. 1N). The gene discussed is PPARA; the disease is hepatocellular carcinoma.