CXCR4 and hepatocellular carcinoma: For other hub genes, transthyretin (TTR) has the ability to stimulate tumor growth through regulation of tumor, immune, and endothelial cells (Lee et al., 2019); FGG is capable of promoting migration and invasion in hepatocellular carcinoma cells through activating epithelial to mesenchymal transition (EMT) (Zhang et al., 2019); and PTPRC can interact with CXCR4 in a putative molecular network constructed from microarray data, which is closely related to colon cancer metastasis (Chu et al., 2017).