The increased survival in vivo of 92R mAb-treated animals, rather than restricted to xenografts of the MOLT-4 cell line, was also observed in orthotopic xenografts generated with primary CCR9+ T-ALL leukemias, as demonstrated with HLPR, T-ALL18, and T-ALL10, despite the lower expression levels of CCR9 on the surface of these primary leukemia cells (3.6-fold,17.5-fold and >50-fold lower than in the MOLT-4 cells). The gene discussed is CCR9; the disease is acute lymphoblastic leukemia.