Role of abnormal integrin-cytoskeletal interactions in impaired β1 integrin function in chronic myelogenous leukemia hematopoietic progenitors

Abnormal circulation and unregulated proliferation of chronic myelogenous leukemia (CML) progenitors is related, at least in part, to BCR/ABL induced abnormalities in beta 1 integrin-mediated adhesion and signaling. The BCR/ABL oncogene has several potential interactions with cytoskeletal elements that are important for normal integrin signaling. In the present study, we evaluated whether abnormalities in beta 1 integrin-cytoskeletal interactions were present in primary CML progenitors and contributed to defective integrin function. beta 1 integrin-cytoskeletal interactions were studied in CML and normal CD34(+) primary hematopoietic progenitors as well as BCR/ABL-transfected or mock-transfected M07e cells. In normal CD34(+) progenitors, antibody-mediated cross-linking of beta 1 integrins resulted in their redistribution into caps via a process requiring receptor-cytoskeletal interactions. CML CD34(+) cells demonstrated significantly impaired beta 1 integrin capping. This defect was related to the presence of the BCR/ABL gene, because capping also was impaired in BCR/ABL-transfected M07e cells. Defective receptor capping was not seen for non-integrin receptors. In addition, CML CD34(+) and M07e(BCR/ABL) cells also demonstrated increased actin polymerization and altered actin cytoskeletal organization. Further studies suggested that impaired beta 1 integrin capping and defective integrin-mediated adhesion and proliferation inhibition in CML cells were related to abnormally enhanced integrin-cytoskeletal association and restricted receptor mobility. Finally, interferon or, which restores integrin-mediated adhesion and signaling in CML progenitors, also enhanced integrin capping in CD34(+) cells. These studies suggest that p210(BCR/ABL) induces abnormal association of integrin receptors with the cytoskeleton and restricted receptor mobility and provide new insights into mechanisms underlying abnormal integrin function in Chit progenitors. (C) 1999 International Society for Experimental Hematology. Published by Elsevier Science Inc.