In lung squamous cell carcinoma and breast carcinoma cells, protein arginine methyltransferase 5 (PRMT5) complexes with MEP50/WDR77, and WDR5 is recruited by the protein complex to target gene promoters, resulting in histone H3K4 trimethylation, target gene transcription and cancer cell invasion (61). Here, WDR77 is linked to squamous cell lung carcinoma.