Laboratory and clinical applications of monoclonal antibodies for leukemias and non-Hodgkin's lymphomas

In vitro evaluation of Pyrularia thionin-anti-CD5 immunotoxin

The membrane-active peptide, Pyrularia thionin, purified from Pyrularia pubera, was covalently conjugated to an anti-CD5 monoclonal antibody. The membrane-active properties of thionin were not affected by the conjugation. The immunotoxin killed CD5+ lymphocytes in vitro at a concentration of 0.1 nmol/10(7) cells after 2 h of incubation. The immunotoxin also inhibited the proliferation of T cells in vitro, stimulated either by mitogens or in the mixed lymphocyte reaction. It was shown by electron paramagnetic resonance of spin probes and differential scanning calorimetry that the ability of the immunotoxin to perturb the lipid phase of membranes is close to that of unconjugated thionin. The results obtained suggest that Pyrularia-thionin-anti-CD5 conjugate may be useful for graft-versus-host disease therapy and potentially in the treatment of CD5+ leukemia and lymphomas.

Non-Hodgkin's lymphomas in children. II. Treatment

The prognosis of non-Hodgkin's lymphoma (NHL) in childhood has improved steadily in the last 2 decades. This is primarily the result of increasingly effective chemotherapy regimens tailored to defined and relatively homogeneous prognostic categories and tested in prospective clinical trials. Surgical excision remains of prognostic benefit only when near-total resection can be performed without delay of chemotherapy. The role of radiation therapy is now limited to the treatment of overt central nervous system (CNS) lymphoma, disease unresponsive to chemotherapy, and certain emergencies. Effective 'prophylactic' treatment of the CNS has been achieved in most series by intrathecal and systemic chemotherapy alone. The most relevant modality of treatment is chemotherapy and a very large number of protocols have been published. The origins of current multi-agent regimens stem both from early experience with cyclophosphamide in endemic Burkitt's lymphoma and from therapeutic studies of acute lymphoblastic leukaemia. Sub-stratification of non-localized NHL has produced protocols designed for either lymphoblastic (mostly T cell) or non-lymphoblastic (mostly B cell) categories. While the cure rate for lymphoblastic lymphoma now exceed 70%, the non-localized non-lymphoblastic disease remains a major obstacle to cure. These patients frequently present with large abdominal primaries and are prone to regional as well as hematogenous dissemination. In particular, involvement of the CNS is now considered to be the most adverse prognostic variable in this group. Recently, highly intensive regimens are addressing these obstacles. On the other hand, NHL defined as localized has been shown to be curable in up to 95% of children with the use of simple chemotherapy regimens as short as 6 months in duration. Salvage of patients who relapse during or after chemotherapy remains bleak but cures are possible with regimens incorporating bone marrow transplantation from either an autologous or allogeneic source. Experimental methods, including biologic and immune response modifiers may also offer future promise.

CD10 and CD44 genes of leukemic cells and malignant cell lines show no evidence of transformation-related alterations

The expression of CD10/CALLA is associated primarily with childhood leukemia of pre-B lymphocyte phenotype. We have compared the hybridization pattern of the CALLA gene from leukemic and normal cells digested with several restriction enzymes. No alterations were noticed with Eco RI, Sac I, Pvu II, Eco RV, Hind III, and Msp I. Since CALLA is also found on other malignancies, we analyzed DNA samples prepared from cell lines derived from leukemia, lymphoma, glioblastoma, retinoblastoma, and neuroblastoma. Normal restriction patterns were observed for all the lines regardless of their CALLA phenotype. Having demonstrated previously that CALLA was structurally identical to neutral endopeptidase 3.4.24.11 (NEP), we have now established a correlation between surface expression of CALLA and NEP activity on leukemia samples and on several cell lines. Malignant cells tested expressed a functionally active enzyme and no gross alteration was present in the CALLA gene. The CD44 gene is expressed on most cells of hemopoietic origin and on greater than 95% of cases of acute lymphoblastic leukemia and acute myeloblastic leukemia studied. It is also expressed on normal astrocytes and on malignant cells of glioma/astrocytoma types. We now report that a similar pattern of hybridization was observed with Sac I, Pvu II, and Eco RI for leukemic samples, normal cells, and malignant cell lines. A polymorphism was recently detected for CD44 using Hind III; leukemic cells and malignant lines also showed this normal polymorphism. Thus no deletion or insertion could be detected in the CD44 gene of leukemic cells and malignant lines, suggesting that no gross DNA alterations were involved. The correlation between surface expression and enzymatic activity of CD10/CALLA and the expression of CD44 on a variety of malignant cells would suggest that the structure and function of these two gene products are probably not altered by the process of transformation.