PVR and cancer: A higher fractional dose of 3–10 Gy and hypofractionation induce tumor tissue infiltration by cytotoxic T lymphocytes with high expression of the T-cell immunoreceptor with Ig and ITIM domains (TIGIT, polyovirus receptor, PVR, CD155), high expression of PD-L1 on cancer cells, but also intensive infiltration of tumor tissue by Treg lymphocytes.