GDF6 and gastric cancer: Among the candidate prognostic genes, the roles of APOD, SLITRK2, ADCYAP1, KCNA1, GDF6, CYP1B1, FABP4, MYB, and SYT4 in the progression of GC have been tested in prior studies [19,20,21,22,23,24,25,26,27].Therefore, we focused on the MMRN1 gene, which was ranked high in the risk score of the GC prognostic model established in this study.