FAT1 and head and neck squamous cell carcinoma: However, FAT1 seems to be playing different roles in different tissues or cancer types based the finding that its expression level is upregulated in acute leukemia, hepatocellular carcinoma (HCC), glioblastoma (GMB), and gastric cancer, but downregulated in HNSCC, ESCC, breast cancer, and cervical cancer [15], though one recent study reported upregulation of FAT1 in oral cancer [16].