Chemokine mRNA expression in LMP1-expressing and LMP1-nonexpressing Burkitt's tumors shown by semiquantitative RT-PCR analysis. Tumor tissue was obtained from Burkitt's tumors established in BALB/c nu/nu mice by subcutaneous inoculation of 10⁷cells from LMP1-nonexpressing (parental BL41, P3HR-1–converted BL41, or GTP-transfected BL41) or LMP1-expressing BL cells (B95-8–converted BL41, LMP1-transfected BL41, or mixtures of GTP and LMP1-transfected BL41 cells). Tumors were obtained either when tumors were greater than 8 cm² or when they developed typical tumor necrosis and scarring lesions that are indicative of tumor regression.