Kakunaga et al. [21] showed that CD155 enhances growth factor-induced activation of Ras/Raf/mitogen-activated protein kinase/extracellular signal-regulated kinase signaling, leading to the upregulation of cell cycle regulators such as cyclins D2 and E, and eventually shortening the G1 phase of the cell cycle, thereby promoting tumor cell proliferation. Here, PVR is linked to neoplasm.