Immunostaining of CD44 and SV40 large T in tumors. BALB/c nude mice were injected subcutaneously with 5 × 10⁶ cells (5 mice/cell line) and after 2 months were sacrificed and tumors were fixed in formalin and paraffin embedded sections and immunostained by using an anti-SV40 large T antibody and the anti-CD44 antibody KM201.CD44-positive tumor (A and B), CD44-negative tumor (C and D), anti-CD44 (A and C), and anti-SV40 large T (B and D).