Maria Wasik

Statins impair antitumor effects of rituximab by inducing conformational changes of CD20.

Background Rituximab is used in the treatment of CD20+ B cell lymphomas and other B cell lymphoproliferative disorders. Its clinical efficacy might be further improved by combinations with other drugs such as statins that inhibit cholesterol synthesis and show promising antilymphoma effects. The objective of this study was to evaluate the influence of statins on rituximab-induced killing of B cell lymphomas. Methods and Findings Complement-dependent cytotoxicity (CDC) was assessed by MTT and Alamar blue assays as well as trypan blue staining, and antibody-dependent cellular cytotoxicity (ADCC) was assessed by a 51Cr release assay. Statins were found to significantly decrease rituximab-mediated CDC and ADCC of B cell lymphoma cells. Incubation of B cell lymphoma cells with statins decreased CD20 immunostaining in flow cytometry studies but did not affect total cellular levels of CD20 as measured with RT-PCR and Western blotting. Similar effects are exerted by other cholesterol-depleting agents (methyl-β-cyclodextrin and berberine), but not filipin III, indicating that the presence of plasma membrane cholesterol and not lipid rafts is required for rituximab-mediated CDC. Immunofluorescence microscopy using double staining with monoclonal antibodies (mAbs) directed against a conformational epitope and a linear cytoplasmic epitope revealed that CD20 is present in the plasma membrane in comparable amounts in control and statin-treated cells. Atomic force microscopy and limited proteolysis indicated that statins, through cholesterol depletion, induce conformational changes in CD20 that result in impaired binding of anti-CD20 mAb. An in vivo reduction of cholesterol induced by short-term treatment of five patients with hypercholesterolemia with atorvastatin resulted in reduced anti-CD20 binding to freshly isolated B cells. Conclusions Statins were shown to interfere with both detection of CD20 and antilymphoma activity of rituximab. These studies have significant clinical implications, as impaired binding of mAbs to conformational epitopes of CD20 elicited by statins could delay diagnosis, postpone effective treatment, or impair anti-lymphoma activity of rituximab.

Partial defects of cell-mediated immunity in patients with epidermodysplasia verruciformis

Different parameters of cell-mediated immunity, including natural cytotoxic reactions, were studied in nine patients with epidermodysplasia verruciformis with or without cutaneous malignancy. We found decreased total number of T lymphocytes and T-helper cells in peripheral blood of the patients, and normal T-suppressor cell number, as detected by monoclonal antibody typing and functional E-rosette test with the use of theophylline. This decrease was found both in active and in late rosette-forming cell subpopulations. Natural killer cell activity of peripheral blood mononuclear cells was found to be increased in four of nine patients with epidermodysplasia verruciformis, whereas antibody-dependent cellular cytotoxicity was within the normal range in all patients studied. Lymphocyte-induced angiogenesis assay, which is a sensitive test for the estimation of the immunocompetence of lymphoid cells, revealed increased angiogenic capability of peripheral blood mononuclear cells in the majority of the patients. Our results suggest that cellular defects in patients with epidermodysplasia verruciformis did not relate to all functions of the immune system.

Potentiation of the anti-tumour effects of Photofrin®-based photodynamic therapy by localized treatment with G-CSF

Photofrin®-based photodynamic therapy (PDT) has recently been approved for palliative and curative purposes in cancer patients. It has been demonstrated that neutrophils are indispensable for its anti-tumour effectiveness. We decided to evaluate the extent of the anti-tumour effectiveness of PDT combined with administration of granulocyte colony-stimulating factor (G-CSF) as well as the influence of Photofrin®and G-CSF on the myelopoiesis and functional activity of neutrophils in mice. An intensive treatment with G-CSF significantly potentiated anti-tumour effectiveness of Photofrin®-based PDT resulting in a reduction of tumour growth and prolongation of the survival time of mice bearing two different tumours: colon-26 and Lewis lung carcinoma. Moreover, 33% of C-26-bearing mice were completely cured of their tumours after combined therapy and developed a specific and long-lasting immunity. The tumours treated with both agents contained more infiltrating neutrophils and apoptotic cells then tumours treated with either G-CSF or PDT only. Importantly, simultaneous administration of Photofrin®and G-CSF stimulated bone marrow and spleen myelopoiesis that resulted in an increased number of neutrophils demonstrating functional characteristics of activation. Potentiated anti-tumour effects of Photofrin®-based PDT combined with G-CSF observed in two murine tumour models suggest that clinical trials using this tumour therapy protocol would be worth pursuing.

Changes in Lymphocyte Subsets in Children with Newly Diagnosed Type 1 Diabetes Mellitus

UNLABELLED The aim of this study was to assess changes in selected peripheral blood lymphocyte subsets in children and adolescents with newly diagnosed type 1 diabetes mellitus (DM) and determine the correlation between these changes and other immunological markers. The study involved a group of 39 patients aged 2-14 years and a control group. The number of T- and B-lymphocytes and the number of CD4, CD8, CD4/HLA-DR, CD8/HLA-DR, CD5/CD20 subsets were measured by flow-cytometry using monoclonal antibodies. Islet cell antibodies (ICA) and antibodies to glutamic acid decarboxylase (GADA) were assessed. In both the diabetic and control groups the number of T-and B-lymphocytes were within normal limits. In patients with DM, the percentage of CD5+/CD20+ cells was significantly increased compared with the control group (p < 0.0001). ICA were positive in 80% of patients and GADA in nearly 65%. A positive correlation between the CD5/CD20 subset and ICA and GADA was found. In patients with a high percentage of CD5+/CD20+ lymphocytes, a higher percentage of activated subsets (CD4/HLA DR and CD8/ HLA DR) was detected. IN CONCLUSION CD5/ CD20 lymphocyte subsets are a good additional marker of autoimmunological processes in DM.

Leptin Receptor in Childhood Acute Leukemias

Ob-R receptor is encoded by db gene and belongs to class I cytokine receptors family. Its expression was observed in hematopoietic CD34+ stem cells, erythropoietic, myeloid and lymphoblastic lineages cell lines and in human leukemic blast cells in lymphomas, acute myeloid leukemia (AML), acute lymphoblastic leukemia (ALL), and chronic myeloid leukemia (CML). The studies on human bone marrow cells show that JAK/STAT pathway plays a substantial role in signal transduction in young bone marrow cells. The aim of the study was to examine the relationship between leptin receptor expression and the proliferation of neoplastic hematopoietic cells in bone marrow. The study was performed in a total of 57 children of both sexes aged 3 months to 16 years. A group of 46 patients with acute leukemia involved 25 children with ALLB, 11 children with ALLT and 10 children with ANNL. The control group consisted of 11 non-obese children with non-malignant hematological disturbances. The tests were performed on bone marrow samples. The assessments of membrane expression of Ob-R and the antigens determining the phenotype of bone marrow cells were performed using a flow cytometry method. In acute lymphoblastic leukemia, a significant decrease of Ob-R expression on leukemic blasts was observed in comparison with respective populations of normal bone marrow cells. Also in progenitor cells populations a significant decrease of CD34+Ob-R+w ALLT and ALLB was observed in comparison with the cells from normal bone marrow. No statistically significant differences in the percentage of Ob-R+ cells in ANNL bone marrow and in control bone marrow were observed.

Lymphocytes sensitivity to Fas stimulation in healthy and asthmatic children

The T cell hypothesis of asthma is based on the concept that the disease is driven and maintained by the persistence of a specialized subset of chronically activated T memory cells sensitized against an array of allergenic, occupational or viral antigens. Overreaction of CD4+ T cells in the peripheral blood and airway tissues is an invariant feature of asthma; therefore a potent mechanism for augmenting the number of activated T cells in this disease would be the resistance to the normally programmed pathway for cell death. The aim of the study was to evaluate the presence of apoptotic markers on peripheral blood lymphocytes from healthy and asthmatic children before and after stimulation with antiCD95 antibodies. The blood was collected from 21 children with atopic asthma suffering from allergic rhinitis because of house dust mite and/or grass pollen allergens and 8 healthy children matched for their age and sex. Blood was mixed with purified monoclonal antibody antiCD95 (Beckman Coulter), incubated for 24 hours and than stained with Annexin V andPI (Becton Dickinson). Prepared suspensions were analyzed with Cytomics FC 500 (Beckman Coulter) flow cytometer. Annexin V(+)/PI(-) cells were characterized as early apoptotic, Annexin V(+)/PI(+) as late apoptotic and Annexin V(-)/PI(+) as dead. In unstimulated sample from asthmatic children 21.09+/-11.20% cells were characterized as Annexin V positive/PI negative. After stimulation with antiCD95 Annexin V positive/PI negative cells constituted 18.72+/-9.42% of cells, p=0.1. In unstimulated sample from healthy children 11.69+/-6.70% cells were characterized as Annexin V positive/PI negative. In the sample stimulated with antiCD95 16.54+/-2.98% of cells were Annexin V positive/PI negative, p=0.02. There were no differences between results of late apoptotic and necrotic lymphocytes from healthy and asthmatic children. Performed research indicates that lymphocytes from asthmatic children are resistant to Fas mediated apoptosis.

Expression of Cytotoxic T Lymphocyte Antigen-4 in T Cells from Children with Hashimoto’s Thyroiditis

The cytotoxic T lymphocyte antigen-4 (CTLA-4) (CD152) is a basic negative regulatory molecule of T cell activation and its hypo-function is associated with severe lymphoproliferative syndrome. The aim of the present study was to evaluate the intracellular and surface expression of CTLA-4 on peripheral T cells before and after T cell activation in children with Hashimotos thyroiditis (HT). Blood samples were obtained from 46 children: 25 with Hashimotos thyroiditis and 21 controls free of autoimmune disease or thyroid disorders. T cell phenotype was evaluated by flow cytometry with the use of monoclonal antibodies combination: CD4- FITC/ CD28 -PC5/ CD152 -PE and CD8 -FITC/ CD28 -PC5/ CD152 -PE on T cell surface and intracellularly at baseline and after 48 h of T cell culture with the mitogen 48-PHA. We found that the number of T cells with intracellular CD152 expression was comparable in HT patients and controls at baseline and increased after 48-PHA, in CD4 subset only, in both patients and controls. However, the increase was more evident in the HT patients. The number of T cells with the surface expression of CD152 at baseline was significantly lower in the HT patients than in controls (p < 0.0002) in non-stimulated CD4+ and CD8+ T cells. After 48-PHA, surface CD152 expression in CD4+T cells increased in both groups; the increase was greater in controls. In conclusion, impaired function of CTLA-4 in HT patients may depend on the imbalance of intracellular/surface expression of CD152 in T cells.