RESUMO
We have previously demonstrated that two prognostic features of myelodysplastic syndromes (MDS) and acute myelogenous leukemia (AML), mutant NRAS and over-expressing BCL-2, cooperate physically and functionally in vivo. Screening of MDS patient bone marrow (BM) identified NRAS:BCL-2 co-localization in 64% cases, correlating with percentage BM blasts, apoptotic features and disease status (p<0.0001). Localization of the complex at the plasma membrane or the mitochondria correlated with disease and apoptosis features in MDS patients, whilst caspase-9 mediated mechanism was elucidated in vivo and in vitro. The intensity and localization of the RAS:BCL-2 complex merits further evaluation as a novel biomarker of MDS.
Assuntos
Apoptose , Síndromes Mielodisplásicas/metabolismo , Síndromes Mielodisplásicas/patologia , Proteínas Proto-Oncogênicas c-bcl-2/metabolismo , Proteínas ras/metabolismo , Animais , Apoptose/genética , Membrana Celular/metabolismo , Progressão da Doença , Genes ras , Humanos , Camundongos , Camundongos Transgênicos , Modelos Biológicos , Complexos Multiproteicos/metabolismo , Síndromes Mielodisplásicas/genética , Ligação Proteica , Proteínas Proto-Oncogênicas c-bcl-2/genética , Distribuição Tecidual/fisiologiaRESUMO
Myelodysplastic syndromes (MDS) are clonal stem cell hematologic disorders that evolve to acute myeloid leukemia (AML) and thus model multistep leukemogenesis. Activating RAS mutations and overexpression of BCL-2 are prognostic features of MDS/AML transformation. Using NRASD12 and BCL-2, we created two distinct models of MDS and AML, where human (h)BCL-2 is conditionally or constitutively expressed. Our novel transplantable in vivo models show that expression of hBCL-2 in a primitive compartment by mouse mammary tumor virus-long terminal repeat results in a disease resembling human MDS, whereas the myeloid MRP8 promoter induces a disease with characteristics of human AML. Expanded leukemic stem cell (Lin(-)/Sca-1(+)/c-Kit(+)) populations and hBCL-2 in the increased RAS-GTP complex within the expanded Sca-1(+) compartment are described in both MDS/AML-like diseases. Furthermore, the oncogenic compartmentalizations provide the proapoptotic versus antiapoptotic mechanisms, by activating extracellular signal-regulated kinase and AKT signaling, in determination of the neoplastic phenotype. When hBCL-2 is switched off with doxycycline in the MDS mice, partial reversal of the phenotype was observed with persistence of bone marrow blasts and tissue infiltration as RAS recruits endogenous mouse (m)BCL-2 to remain active, thus demonstrating the role of the complex in the disease. This represents the first in vivo progression model of MDS/AML dependent on the formation of a BCL-2:RAS-GTP complex. The colocalization of BCL-2 and RAS in the bone marrow of MDS/AML patients offers targeting either oncogene as a therapeutic strategy.
Assuntos
Genes bcl-2 , Genes ras , Síndromes Mielodisplásicas/genética , Animais , Transplante de Medula Óssea , Transplante de Células , Ensaio de Unidades Formadoras de Colônias , Modelos Animais de Doenças , Progressão da Doença , Imunofenotipagem , Leucemia/genética , Leucemia Mieloide/genética , Camundongos , Camundongos Transgênicos , Microscopia Confocal , Síndromes Mielodisplásicas/patologia , Síndromes Mielodisplásicas/fisiopatologia , BaçoRESUMO
Multidrug resistance (MDR) confers resistance to anticancer drugs and reduces therapeutic efficiency. It is often characterized by the expression of the MDR1 gene product P-glycoprotein (or gp170) at the membrane of tumor cells. To further propose a potential complementary tool in cancer treatment, the sensitivity of gp170 tumor cells to NK-dependent lysis was investigated. Two kinds of cells were generated from wild-type K562 erythroleukemic cells: the first were derived from Taxol-selected cells and cloned, whereas the second were retrovirally transduced by the cDNA of the MDR1 gene. The last process was also applied to the human embryonal carcinoma cells called Tera-2 cells. First, both cloned and MDR-1 K562 cells appeared highly susceptible to naive NK cell killing. Interestingly, in addition, Tera-2 cells that were not sensitive to NK lysis could be killed when they expressed gp170 at their membranes. In previous data, we demonstrated that NK cell release of bimolecular complexes composed of perforin and platelet-activating factor (PAF) interacting with the PAF-R, which has to be expressed on the target cell membranes, were components of NK tumor cell killing. In the present study, we show that gp170 has the capacity to drive constitutive PAF-R expression on tumor cells, which could be responsible for hypersensitivity to NK lysis and accelerated cell death.