COL1A1 and gastric cancer: We first performed a univariable Cox regression analysis on the GC group in TCGA cohort and identified 10 PPFRGs (APOA1, CD36, COL1A1, COL1A2, DGKI, F2R, F5, MMRN1, SERPINE1, and SPARC) that were significantly associated with the OS in patients with GC; high expression of these genes was positively correlated with a poor prognosis (Figure 3A; Supplementary Figure S1C).