RESUMO
A role of endothelial cells in the survival of CLL cells during extravasation is presently unknown. Herein we show that CLL cells but not normal B cells can receive apoptotic signals through physical contact with TNF-α activated endothelium impairing survival in transendothelial migration (TEM) assays. In addition, the CLL cells of patients having lymphadenopathy (LApos) show a survival advantage during TEM that can be linked to increased expression of α4 and αL integrin chains. Within this context, ephrinA4 expressed on the surface of CLL cells sequestrates integrins and inactivates them resulting in reduced adhesion and inhibition of apoptotic/survival signals through them. In agreement, ephrinA4 silencing resulted in increased survival of CLL cells of LApos patients but not LA neg patients. Similarly was observed when a soluble ephrinA4 isoform was added to TEM assays strongly suggesting that accumulation of this isoform in the serum of LApos patients could contribute to CLL cells dissemination and survival in vivo. In supporting, CLL lymphadenopathies showed a preferential accumulation of apoptotic CLL cells around high endothelial venules lacking ephrinA4. Moreover, soluble ephrinA4 isolated from sera of patients increased the number and viability of CLL cells recovered from the lymph nodes of adoptively transferred mice. Finally, we present evidence suggesting that soluble ephrinA4 mediated survival during TEM could enhance a transcellular TEM route of the CLL cells. Together these findings point to an important role of ephrinA4 in the nodal dissemination of CLL cells governing extravasation and survival.
Assuntos
Apoptose , Antígeno CD11a/metabolismo , Sobrevivência Celular , Efrina-A4/metabolismo , Integrina alfa4/metabolismo , Leucemia Linfocítica Crônica de Células B/patologia , Idoso , Idoso de 80 Anos ou mais , Animais , Linfócitos B/fisiologia , Células Cultivadas , Técnicas de Cocultura , Endotélio/metabolismo , Efrina-A4/sangue , Efrina-A4/genética , Feminino , Células Endoteliais da Veia Umbilical Humana , Humanos , Leucemia Linfocítica Crônica de Células B/sangue , Linfonodos/patologia , Metástase Linfática , Masculino , Camundongos , Camundongos Endogâmicos BALB C , Pessoa de Meia-Idade , Isoformas de Proteínas/sangue , Isoformas de Proteínas/metabolismo , Interferência de RNA , RNA Interferente Pequeno/metabolismo , Organismos Livres de Patógenos Específicos , Migração Transendotelial e Transepitelial , Células Tumorais Cultivadas , Fator de Necrose Tumoral alfa/metabolismo , Ensaios Antitumorais Modelo de XenoenxertoRESUMO
A better knowledge of the molecular mechanisms that govern leukocyte trafficking is of major relevance for the clinics. Both normal and pathologic extravasation of lymphocytes are a fine-tuned spatio-temporal event of migratory path-finding likely regulated by molecular guidance cues underlying cell movements in other systems. We have recently reported that members of the Eph family of receptor tyrosine kinases, namely EphA2 and one of its ligands, ephrin-A4 (EFNA4) can mediate in the traffic of chronic lymphocytic leukemia (CLL) cells and presumably of normal B cells between the blood and the tissues. The importance of EphA2-EFNA4 interactions at the endothelium-lymphocyte interface during TEM could rely on their attractive/repulsive properties. In the present work, we expand on those results by including additional insights and new suggestions for future studies that discuss the relevance of these molecules in overall cell adhesion dynamic events.
Assuntos
Efrinas/metabolismo , Linfócitos/citologia , Linfócitos/metabolismo , Receptores da Família Eph/metabolismo , Transdução de Sinais , Migração Transendotelial e Transepitelial , Animais , Efrina-A4/metabolismo , Humanos , Leucemia Linfocítica Crônica de Células B/enzimologia , Leucemia Linfocítica Crônica de Células B/patologia , Linfonodos/enzimologia , Linfonodos/patologia , Receptor EphA2/metabolismoRESUMO
Chronic lymphocytic leukemia (CLL) cell migration into lymphoid tissues is an important aspect of the pathobiology of this disease. Here, we investigated the role of ephrin-A4 (EFNA4) in the transendothelial migration (TEM) capacity of CLL and normal B cells through interacting with endothelial EphA2 (erythropoietin-producing hepatocellular carcinoma). CLL cells showed a remarkable impairment in the adhesion to and transmigration through human umbilical vein endothelial cell (HUVEC) monolayers, correlating with their higher EFNA4 expression. In vitro, TEM was mediated by EFNA4 binding to endothelial EphA2 receptor, which is highly expressed in tumor necrosis factor-alpha-activated HUVECs as well as in the CD31(+) endothelial cells of human lymph nodes. The pretreatment of CLL cells with EphA2 homodimers further impaired their adhesion to and transmigration through HUVEC monolayers, whereas pretreatment of HUVECs with EFNA4 homodimers improved those phenomena in both CLL and normal B cells, suggesting that EFNA4 signaling negatively contributed to TEM. In fact, EFNA4 signaling into CLL cells significantly reduced their adhesion to intercellular adhesion molecule 1, vascular cell adhesion molecule 1, and several extracellular matrix molecules and impaired CCL-19-mediated TEM and chemotaxis. Our results suggest that EFNA4-EphA2 interactions are involved in CLL cell trafficking between blood and the tissues and therefore may become a therapeutic target in the future.
