NOP2 and gastric cancer: As an RNA-binding protein belonging to NOL1/NOP2/SUN (NSUN) domain family, NSUN2 is found to regulate the methylation that transforms cytosine into 5-methylcytosine (m5C) in a variety of RNAs such as tRNAs, mRNAs and ncRNAs [33], which is involved in the progress of multitype tumors such as GC and bladder cancer [26, 35, 53].