MLH1 and nasopharyngeal carcinoma: Germline variation in NPC mainly focuses on the pathways of DNA damage repair (such as BRCA2 DNA-repair-associated (BRCA2), protein kinase, DNA-activated, catalytic subunit (PRKDC), mutL homolog 1 (MLH1), and lysine methyltransferase 2C (KMT2C)), host defense (macrophage-stimulating 1 receptor (MST1R)), EBV virus infection (BCL2-like 12 (BCL2L12), NEDD4-like E3 ubiquitin protein ligase (NEDD4L)), and NOTCH signaling (notch receptor 1 (NOTCH1), DLL3 delta-like canonical notch ligand 3 (DLL3)) [50,51,52,53].