C-kit receptor (CD117) expression on plasma cells in monoclonal gammopathies.

The surface expression of CD117 antigen (c-kit) on plasma cells from 158 multiple myeloma (MM), 12 plasma cell leukemia (PCL), 7 MGUS, 7 IgM lymphoplasmacytic lymphoma patients and 10 healthy subjects has been analyzed by flow cytometry using triple staining with the monoclonal antibodies CD138, CD117 and CD38. The antigen expression intensity was calculated as relative fluorescence intensity (RFI) and for direct quantitative analysis the QuantiBRITE test (Becton Dickinson) was applied. Antibody bounding capacity (ABC) was calculated using QuantiCALC software. CD117 antigen was present in 49/158 MM, 5/12 PCL and 5/7 MGUS patients. The RFI values ranged from 0.2 to 20.2 in particular MM patients (mean: 11.0+/-5.3; median 11.5) while the number of CD117 binding sites (ABC) on MM plasma cells ranged from 637 to 6217 (mean: 3029+/-1568; median 2946) (r=0.8328). In responsive to chemotherapy c-kit positive MM patients the percentage of CD117+ plasma cells in the bone marrow decreased significantly while in c-kit negative MM patients the percentage of CD117+ cells in bone marrow did not change and remained in the normal limits. When comparing the clinical and biological disease characteristics (monoclonal protein isotype, albumin, beta2-microglobulin, lactate dehydrogenase, stage of disease, response to chemotherapy, survival time) of c-kit positive and c-kit negative cases, no significant differences were found. In CD117 positive PCL cases expression of CD117 was detected in bone marrow plasma cells as well as in peripheral blood plasma cells. Normal plasma cells and those in IgM lymphoplasmacytic lymphoma did not show reactivity for the CD117 antigen. We conclude that it may be rationale to consider usefulness of therapy with tyrosine kinase inhibitors in the management of c-kit positive plasma cell proliferations. In one third of MM and PCL patients c-kit antigen could be considered as a "tumor associated marker" and together with CD38 and CD138 it may be of value for the identification of the malignant clone in minimal residual disease as it was first suggested by Spanish authors.

c-Kit receptor (CD117) expression on myeloblasts and white blood cell counts in acute myeloid leukemia.

BACKGROUND: The c-Kit receptor is considered to play a crucial role in hematopoiesis. Induction of mobilization of hematopoietic cells in the bone marrow requires cooperative signaling through c-Kit and c-Kit ligand pathway, and these interactions are important in the retention of stem cells within the bone marrow. Therefore, we analyzed c-Kit density on the leukemic myeloblasts of patients with acute myeloid leukemia (AML) in relation to white blood cell count (WBC) in the peripheral blood. METHODS: Bone marrow aspirates collected from patients with AML and bone marrow aspirates and leukapheresis products after granulocyte colony-stimulating factor blood mobilization from adult volunteers were studied. To determine the level of c-Kit receptor expression, we applied quantitative (relative fluorescence intensity and antibody binding per cell) cytometric methods. RESULTS: Our data showed negative correlation between the level of c-Kit expression intensity on myeloblasts and the number of leukocytes in blood of AML patients. The c-Kit receptor density on myeloblasts in patients with low WBC was significantly stronger than that on myeloblasts in patients with high WBC. In the latter patient group, the density c-Kit receptor on myeloblasts was similar to that on CD34(+) cells in mobilized peripheral blood. CONCLUSIONS: The obtained data suggest an involvement of c-Kit receptor in the regulation of leukemic myeloblasts egress to the peripheral blood.

Hepatocellular peroxisome proliferation and DNA synthesis in Wistar rats treated with herbicide fluazifop.

The aim of this study was to determine the effect of herbicide fluazifop, on the early occurring changes in rat liver regarded as hepatic markers of peroxisome proliferators (PPs). Fluazifop was administered orally to male Wistar rats at increasing doses from 5.6 to 891 mg/kg body weight per day for 1, 2, 4, 7 and 14 consecutive days and peroxisome proliferation, induction of some peroxisome-associated enzymes and mitogenesis (S-phase, M-phase and percentage of binucleated hepatocytes) were studied. Short-term treatment of rats with fluazifop resulted in hepatomegaly due to time dependent proliferation of smooth endoplasmic reticulum (SER) and peroxisomes. The increase in the number of peroxisomes in the hepatocytes was supported by an increase in peroxisomal palmitoyl-CoA oxidation and catalase activity. In contrast to other PPs fluazifop induced low rate of rcplicative DNA synthesis and did not affect mitoses (M-phase). DNA synthesis was accompanied by the appearance of binucleated hepatocytes. Thus, we can conclude that fluazifop produces in male Wistar rats hepatomegaly due to cellular hypertrophy. The threshold dose for palmitoyl-CoA oxidation and DNA synthesis was 112 and 223 mg/kg body weight per day, respectively. The value for hepatomegaly and catalase activity was 56 mg/kg body weight per day. The results presented in this paper demonstrated that fluazifop can be classified as a weak rodent PPs.

Potential link between MHC-self-peptide presentation and hematopoiesis; the analysis of HLA-DR expression in CD34-positive cells and self-peptide presentation repertoires of MHC molecules associated with paroxysmal nocturnal hemoglobinuria.

The mechanisms of MHC allele associations with paroxysmal nocturnal hemoglobinuria (PNH) and its aplastic anemia subtype (AA/PNH) remain unclear. It might be dependent on MHC molecule functional properties, such as a scope and frequency of antigen sampling and presentation. For documented PNH-associated MHC alleles we analyzed current reference databases on MHC molecule-eluted peptide presentation repertoires and searched for a range of presented peptides. MHC class II expression was measured on CD34+ cells and appeared to be increased in PNH patients. Two class I alleles (HLA-A*24:02 and B*18:01) have been previously confirmed to associate with protection and increased risk of AA/PNH, respectively. Their product molecules presented immunodominant epitopes derived from proapoptotic (serine/threonine-protein phosphatase) and antiapoptotic (phospholipase D), respectively, intracellular enzymes dependent on phosphoinositide (PI) content. For total PNH and non-aplastic PNH (n/PNH) subtype-associated DRB1*15:01 and DRB1*04:01 class II molecules presentation of exceptionally broad arrays of their own peptide fragments has been found. We conclude that self antigen peptides presented with high frequency in the context of MHC molecules of increased expression may be involved in the immune recognition and the regulation of HSC in the periphery. The block in the normal plasma membrane PI production due to the PIG-A mutation can help explain the differences in the activation of intracellular regulatory pathways observed between PNH and normal HSC. This is evident in the variation in MHC association patterns and peptide presentation repertoires between these two groups of patients.

Flow cytometric immunophenotypic characteristics of plasma cell leukemia.

The aim of this prospective study was to define the flow cytometric characteristics of simultaneously investigated bone marrow and peripheral blood plasma cells antigens expression in 36 plasma cell leukemia (PCL) patients. The immunophenotypic profile of plasma cells was determined with a panel of monoclonal antibodies. The antigen expression intensity was calculated as relative fluorescence intensity (RFI). Bone marrow plasma cells showed expression of particular antigens in the following proportion of cases: CD49d 100%, CD29 94%, CD54 93%, CD44 83%, CD56 60%, CD18 26%, CD11b 29%, CD11a 19%, CD117 27%, CD71 30%, CD126 100% and CD19 0%, while the expression of those antigens on peripheral blood plasma cells was present in the following percentage of patients: CD49d 100%, CD29 96%, CD54 93%, CD44 95%, CD56 56%, CD18 50%, CD11b 53%, CD11a 29%, CD117 26%, CD71 28%, CD126 100% and CD19 0%. The expression of CD54 was significantly higher than that of adhesion molecules belonging to the integrin b2 family: CD11a, CD18 and CD11b, on both bone marrow and peripheral blood cells (p < 0.01). Expression of CD18, CD11a and CD11b was differential between two cell compartments: lower on bone marrow and higher on peripheral blood cells. We found that plasma cells in the bone marrow of patients with plasma cell leukaemia showed significantly greater granularity and size than those in the peripheral blood (p = 0.0001 and p = 0.04, respectively). However, no differences in cell size or granularity were revealed between bone marrow plasma cells from patients with PCL and multiple myeloma. In conclusion, impaired expression of adhesion molecules such as CD11a/CD18 (LFA-1) or CD56 may explain hematogenic dissemination characterizing PCL. The following pattern of adhesion molecule expression according to the proportion of plasma cells expressing a given antigen in peripheral blood and bone marrow and arranged in diminishing order may be established: CD49d > CD44 > CD54 > CD29 > CD56 > CD18 > CD11b > CD11a. Immuno-phenotyping of plasma cells in PCL, as in multiple myeloma, might be useful in detecting minimal residual disease in cases with aberrant antigen expression and for selecting therapeutic agents towards specific membrane targets.

Flow cytometric immunophenotypic characteristics of 36 cases of plasma cell leukemia.

Prospective flow cytometric analysis of antigens expression on bone marrow and peripheral blood plasma cells of 36 plasma cell leukemia (PCL) patients enabled to establish the following immunophenotype of leukemic plasma cell: CD38(++), CD138(+), CD54(+), CD49d(+), CD29(+), CD44(+), CD126(+), CD19(-), CD45(-). In one-third of patients PCL cells express CD56, CD71 and CD117. Expression of CD54 on plasma cells was higher as compared to expression of adhesion molecules CD11a, CD18 and CD11b (p<0.01). Expression of CD18, CD11a, CD11b was lower on bone marrow and higher on peripheral blood cells. In conclusion, impaired expression of adhesion molecules such as CD11a/CD18 or CD56 may explain hematogenic dissemination characterizing PCL.

Clinicopathological correlates of plasma cell CD56 (NCAM) expression in multiple myeloma.

The aim of this prospective, long-term study was to define the flow cytometric characteristics of plasma cell CD56 expression as well as determine the clinical characteristics of 204 multiple myeloma (MM) patients and 26 plasma cell leukemia (PCL) patients with regard to CD56 expression. CD56 expression intensity was determined by measurement of antigen molecules on the cell defined as Antibodies Bound per Cell (ABC) and calculation of Relative Fluorescence Intensity (RFI). CD56 expression was found in 66% of MM and 54% of PCL cases. The RFI values for individual MM patients ranged from 7.6 to 27.4 while ABC values on MM plasma cells from 2255 to 58469. There was a correlation between the proportion of all bone marrow CD38(++)/CD138(+) cells with CD56 expression and ABC and RFI indices. With regard to CD56 expression positive patients, the CD56(-) MM patients presented lower frequency of osteolysis (p = 0.01). The median survival was 48 months in CD56(+) patients and 43 months (p = 0.84) in CD56(-) cases. In conclusion, CD56 expression carries no distinct adverse prognosis and the lack of CD56 expression does not define a unique clinicopathological or prognostic entity in MM. A remarkable heterogeneity of CD56 expression intensity in CD56(+) patients imposes the necessity of determining CD56 expression intensity in candidates to antibody-based therapy.