The interplay of CD150 and CD180 receptor pathways contribute to the pathobiology of chronic lymphocytic leukemia B cells by selective inhibition of Akt and MAPK signaling.

Cell surface expression of CD150 and CD180 receptors in chronic lymphocytic leukemia (CLL) associates with mutational IGHV status and favourable prognosis. Here we show a direct correlation between cell surface expression and colocalization of these receptors on CLL B cells. In the absence of CD150 and CD180 on the cell surface both receptors were expressed in the cytoplasm. The CD150 receptor was colocalized with markers of the endoplasmic reticulum, the Golgi apparatus and early endosomes. In contrast, CD180 was detected preferentially in early endosomes. Analysis of CD150 isoforms differential expression revealed that regardless of CD150 cell surface expression the mCD150 isoform with two ITSM signaling motifs was a predominant CD150 isoform in CLL B cells. The majority of CLL cases had significantly elevated expression level of the soluble sCD150, moreover CLL B cells secrete this isoform. CD150 or CD180 crosslinking on CLL B cells alone led to activation of Akt, mTORC1, ERK1/2, p38MAPK and JNK1/2 networks. Both CD150 and CD180 target the translation machinery through mTOR independent as well as mTOR dependent pathways. Moreover, both these receptors transmit pro-survival signals via Akt-mediated inhibition of GSK3ß and FOXO1/FOXO3a. Unexpectedly, coligation CD150 and CD180 receptors on CLL B cells led to mutual inhibition of the Akt and MAPK pathways. While CD150 and CD180 coligation resulted in reduced phosphorylation of Akt, ERK1/2, c-Jun, RSK, p70S6K, S6RP, and 4E-BP; it led to complete blocking of mTOR and p38MAPK phosphorylation. At the same time coligation of CD150 and CD40 receptors did not result in Akt and MAPK inhibition. This suggests that combination of signals via CD150 and CD180 leads to blocking of pro-survival pathways that may be a restraining factor for neoplastic CLL B cells propagation in more than 50% of CLL cases where these receptors are coexpressed.

Malignant diseases of hematopoietic and lymphoid tissues in Chernobyl clean-up workers.

INTRODUCTION: The question as to whether the incidence of leukemias and malignant lymphomas among the clean-up workers increased in 18 years after the catastrophe is still a point of much controversy. Precise diagnosis of the main forms of hematopoietic malignancies and comparison of these data with those in the general population will be helpful in estimating thr relative contribution of the radiation factor to the overall incidence of such pathologies. MATERIALS AND METHODS: In all, 187 consecutive cases of malignant diseases of hematopoietic and lymphoid tissues in Chernobyl clean-up workers were analyzed in Ukrainian Reference Laboratory in 1996-2003. A total of 1942 consecutive patients of general population, mainly the residents of Kyiv city and district, diagnosed in References Laboratory at the same period comprised the group of comparison. The morphology and cytochemistry of bone marrow and peripheral blood cells were studied. Immunocytochemical techniques (PAP, APAAP, ABC) and the panel of monoclonal antibodies to differentiation antigens of leukocytes were employed for immunophenotyping leukemic cells. RESULTS: Various types of malignant disease of hematopoietic and lymphoid tissues were registered in Chernobyl clean-up workers under study including myelodysplastic syndromes (nine patients), acute lymphoblastic leukemia (eight) and acute myeloblastic leukemia (31), chromic myeloid leukemia (17), multiple myeloma (17) and other forms of chromic myeloproliferative and lymphoproliferative disease including B-cell chromic lymphocytic leukemia (49 patients). CONCLUSION: The verified diagnosis of tumors of hematopoietic malignancies according to modern classification (EGIL, WHO) could be the prerequisite for further analytical epidemiology study of leukemias that may be related to the Chernobyl accident.

Histologic verification of leukemia, myelodysplasia, and multiple myeloma diagnoses in patients in Ukraine, 1987-1998.

In preparation for a possible large epidemiological study of radiation-related leukemia in Chernobyl clean-up workers of Ukraine, histologic evaluation of 62 cases of leukemia and related disorders was conducted by a panel of expert hematologists and hematopathologists from the United States, France, and Ukraine. All cases were randomly selected from a surrogate population of men in the general population of 6 regions of Ukraine who were between the ages of 20 and 60 years in 1986 and were reported to have developed leukemia, myelodysplasia, or multiple myeloma between the years 1987 and 1998. The hematologists and hematopathologists on the panel were in agreement with one another and with the previously reported diagnoses and classifications of about 90% of the cases of acute and chronic leukemia in the study. These results suggest that strong reliance can be placed on the clinical diagnoses of acute and chronic forms of leukemia and multiple myeloma that have occurred in Ukrainian Chernobyl clean-up workers providing that the diagnoses are supported by records of the patients having had adequate histologic bone marrow studies. The number of cases in this study with the diagnosis of myelodysplasia, however, was too small to draw firm conclusions.