title: Use of a novel colony assay to evaluate the cytotoxicity of an immunotoxin containing pokeweed antiviral protein against blast progenitor cells freshly obtained from patients with common B-lineage acute lymphoblastic leukemia.
abstract: We report a novel colony assay for B-lineage progenitor cells in acute lymphoblastic leukemia (ALL). The primary plating efficiency of blast progenitors freshly obtained from common B-lineage ALL patients varied between 0.09 and 2.63%. Morphological, cytochemical, and immunological analyses of cells from day 7 colonies provided the evidence that they are B-lineage lymphoblasts. Immunological marker analyses of cultured blasts using BA-2 (anti-CD9), BA-3 (anti-CD10), BA-1 (anti-CD24), and B43 mAb have allowed us to define two distinct immunological groups. The first group had BA-2+, BA-3+, BA-1+, B43+ marker profiles, consistent with the phenotype of uncultured bone marrow blasts. The second group differed in that the cells in the blast colonies were BA-3 (anti-CD10)-negative, although many of the cells in the bulk population were BA-3+ before culture. Blasts from both groups were able to proliferate and form secondary colonies when recultured. A pan-B immunotoxin was synthesized by linking B43, a human B cell-specific mAb, to pokeweed antiviral protein (PAP). This study showed that B43-PAP can effectively eradicate leukemic progenitor cells freshly obtained from patients with common B-lineage ALL. B43-PAP eliminated greater than 99.96% of blast progenitors under conditions in which only minimal inhibition of normal bone marrow progenitor cells (CFU-GM, CFU-E, CFU-MK, CFU-GEMM) was observed. Our results establish that the surface determinant recognized by B43 is expressed on B-lineage progenitor cells in ALL, and that these cells are sensitive to PAP at the ribosomal level. To our knowledge, B43-PAP is the first IT to prove effective against common B-lineage ALL cells.
mesh_terms: D000293:Adolescent; D000911:Antibodies, Monoclonal / Q000008:administration & dosage; D000951:Antigens, Neoplasm / Q000032:analysis; D000954:Antigens, Surface / Q000032:analysis; D001402:B-Lymphocytes / Q000145:classification / Q000187:drug effects*; D001853:Bone Marrow / Q000187:drug effects / Q000473:pathology; D016026:Bone Marrow Transplantation; D002648:Child; D002675:Child, Preschool; D003114:Colony-Forming Units Assay / Q000379:methods*; D004351:Drug Resistance; D005260:Female; D006412:Hematopoietic Stem Cells / Q000187:drug effects; D006801:Humans; D007223:Infant; D007945:Leukemia, Lymphoid / Q000628:therapy*; D008212:Lymphocyte Depletion; D008297:Male; D009699:N-Glycosyl Hydrolases; D014411:Neoplastic Stem Cells / Q000187:drug effects*; D010940:Plant Proteins / Q000008:administration & dosage / Q000494:pharmacology*; D054789:Ribosome Inactivating Proteins, Type 1; D014182:Transplantation, Autologous
chemical_list: D000911:Antibodies, Monoclonal; D000951:Antigens, Neoplasm; D000954:Antigens, Surface; D010940:Plant Proteins; D054789:Ribosome Inactivating Proteins, Type 1; D009699:N-Glycosyl Hydrolases; C024275:pokeweed antiviral protein