We then explored the T-cell costimulatory properties of XmAb808 with human carcinoma cell lines by engineering B7-H3+ 22Rv1 prostate cancer cells and B7-H3–negative LOX-IMVI melanoma cells to express the same anti-CD3 antibody used in the HEK293-αCD3 cells. Here, CD276 is linked to prostate carcinoma.