RV + BTZ combination therapy upregulates immune check point expression in MM tumor as early as 4 days posttreatment. (A) IHC staining images of spleen myeloma PD-L1 in mice. Note the rare expression of PD-L1 in the tumors of mice treated with the VC as compared with the strong expression of this checkpoint protein in the tumor after treatment with live virus and BTZ (magnification ×200 = ×10 and ×20; camera: Ventana Vias Zeiss Axio; acquisition software: Nuance; composite figure via Adobe Photoshop CS4). Bar plots representing quantified PD-L1 (B), PD-L2 (C), and IDO expression (D) in MM cells in BM and spleen. N = 3; ***P < .001, **P < .01, *P < .05, Conover’s test.