The heat map shows the difference in the expression of these six genes in the normal and tumor groups of the training cohort, and the results showed that TFAP2A, SLC16A1, HNF4A and GDF15 were upregulated in the tumor group, while CDO1 and ALOX15 were downregulated in the tumor group (Figure 1H). The gene discussed is GDF15; the disease is neoplasm.