PVR and breast carcinoma: Then, by quantitative real-time PCR (qRT-PCR), we compared the expression of CD155 isoforms among colorectal, gastric, and breast cancers and their adjacent non-tumor tissues; the expressions of CD155α and CD155β, but not CD155γ,were significantly higher in the cancers than in the non-tumor tissues (P < 0.05) (Fig 2).