RAD51 and esophageal squamous cell carcinoma: Among them, genes in the MMR (HFM1) and BER (NEIL1) pathways were downregulated in ESCC tumor tissues, while genes in HR (EME1, RAD54L, XRCC2, BRCA1/2, RAD51, RAD54B, BRIP1), FA (UBE2T, FANCA, FANCI, FANCB, FANCM), NER (RPA3), NHEJ (PRKDC), and TLS (MAD2L2) pathways were upregulated in ESCC tumor tissues (Figure 4A,B).