Another HCMV gene implicated in tumor development is US28, which encodes a functional chemokine receptor that binds several human chemokines, including CCL2/MCP-1, CCL5/Rantes, and CX3CL1/Fractalkine [14, 35]. US28 also exhibits constitutive signaling activity, and cells expressing US28 are highly invasive  and form tumors in nude mice [36, 37]. US28 was found to induce vascular endothelial growth factor (VEGF), cyclooxygenase-2 (COX2), and Stat3 activation through upregulation of IL-6 [36–38]. Analysis of glioblastoma tumor specimens revealed the presence of both US28 and phosphorylated Stat3 [27, 38], demonstrating that US28 may play role in tumor development in vivo.