Advances in the diagnosis and classification of chronic lymphoproliferative disorders

A phase I study of dacetuzumab (SGN-40, a humanized anti-CD40 monoclonal antibody) in patients with chronic lymphocytic leukemia

Despite advances in therapy, chronic lymphocytic leukemia remains an incurable disease and novel, effective therapies are needed. In this open-label, dose-escalation, phase I study, dacetuzumab (IgG1 humanized monoclonal antibody) was administered to 12 adults, all of whom had received several prior systemic therapies (median, 4; range, 2-11). Intrapatient dose escalation (maximum weekly doses of 3-8 mg/kg) was used to diminish first-dose-related inflammatory symptoms. No dose-limiting toxicities or dose-dependent trends in adverse events (AEs) were observed. The most common AEs (in >/=2 patients) were fatigue, headache, anorexia, conjunctivitis, hyperhidrosis, and night sweats, all of which were mild or moderate. No deaths, serious AEs, or discontinuations due to AEs occurred. Although no patient achieved an objective response, five patients demonstrated stable disease after 1 cycle of therapy, with no discernable correlation between dacetuzumab dose and outcome. This modest single-agent activity may warrant further testing of dacetuzumab in combination with other chronic lymphocytic leukemia therapies.

The leukemias of mature lymphocytes

The leukemias of mature B cells and T cells are a limited set of diseases in which blood and bone marrow are the primary sites of involvement. Although they may superficially resemble one another, they have distinct clinical and pathologic features and must be distinguished from one another. In this article, the major clinical, morphologic, phenotypic, and molecular genetic features of the mature B- and T-cell leukemias are reviewed, and differential diagnostic considerations are discussed.

High expression of 5-lipoxygenase in normal and malignant mantle zone B lymphocytes

Background

Human B lymphocytes can produce leukotriene B₄ but the biological function of the 5-lipoxygenase (5-LO) pathway in B cells is unclear. In order to better understand and define the role of 5-LO in B cells, we investigated the expression of 5-LO mRNA and protein in subsets of B cells from human tonsils and different types of B cell lymphoma.

Results

Based on RT-PCR and western blot/immunohistochemical staining, with a polyclonal antibody raised against 5-LO, high expression of 5-LO was found in mantle zone B cells from tonsils. By contrast, only a weak expression of 5-LO was detected in germinal centre cells and no expression in plasma cells from tonsils. This pattern of 5-LO expression was preserved in malignant lymphoma with high expression in mantle B cell lymphoma (MCL) and weak or no expression in follicular lymphoma. Primary leukemized MCL, so called B-prolymphocytic leukaemia cells, and MCL cell lines also expressed 5-LO and readily produced LTB₄ after activation.

Conclusion

The present report demonstrates the expression of 5-LO mainly in normal and malignant mantle zone B cells while the expression is low or absent in germinal centre B cells and plasma cells, indicating a role of the 5-LO pathway in B cells before the cells finally differentiate to plasma cells.