Transferred BCR/ABL DNA from K562 Extracellular Vesicles Causes Chronic Myeloid Leukemia in Immunodeficient Mice

Abstract

Our previous study showed that besides mRNAs and microRNAs, there are DNA fragments within extracellular vesicles (EVs). The BCR/ABL hybrid gene, involved in the pathogenesis of chronic myeloid leukemia (CML), could be transferred from K562 EVs to neutrophils and decrease their phagocytic activity in vitro. Our present study provides evidence that BCR/ABL DNAs transferred from EVs have pathophysiological significance in vivo. Two months after injection of K562 EVs into the tail vein of Sprague-Dawley (SD) rats, they showed some characteristics of CML, e.g., feeble, febrile, and thin, with splenomegaly and neutrophilia but with reduced neutrophil phagocytic activity. These findings were also observed in immunodeficient NOD/SCID mice treated with K562 EVs; BCR/ABL mRNA and protein were found in their neutrophils. The administration of actinomycin D, an inhibitor of de novo mRNA synthesis, prevented the abnormalities caused by K562 EVs in NOD/SCID mice related to CML, including neutrophilia and bone marrow hyperplasia. As a specific inhibitor of tyrosine kinases, imatinib blocked the activity of tyrosine kinases and the expression of phospho-Crkl, induced by the de novo BCR/ABL protein caused by K562 EVs bearing BCR/ABL DNA. Our current study shows the pathophysiological significance of transferred tumor gene from EVs in vivo, which may represent an important mechanism for tumorigenesis, tumor progression, and metastasis.

Barriers to horizontal cell transformation by extracellular vesicles containing oncogenic H-ras

“…In keeping these predictions, we observed no permanent intercellular transfer of oncogenic gDNA, while other EV-associated transforming cargo, such as oncoproteins, mRNA or microRNA lack self-replicating potential, and their effects on cells could be inherently self-limiting due to degradation and dilution [6, 8]. Our study does not rule out the possibility of horizontal transformation mediated by oncogenic viruses, induction of genetic instability or epigenetic influences in the context of specific cancer cell types [22, 39, 40]. …”

“…Also, EVs emitted by viable aggressive breast cancer cells were shown to contain transforming proteins [18] or microRNA [19] whose intercellular transfer engendered a fully tumorigenic phenotype in the case of normal fibroblasts or breast epithelial cell recipients, respectively. Similarly, EVs from BCR-ABL-driven leukaemia caused malignant conversion of normal myeloid cells [20–22]. …”

SRY gene transferred by extracellular vesicles accelerates atherosclerosis by promotion of leucocyte adherence to endothelial cells

“…We found the presence of AT 1 R (angiotensin type 1 receptor) gene-coding region, 5 promoter region and 3 UTR in EVs from vascular smooth muscle cells. Transferred BCR/ABL gene from CML-derived EVs to normal neutrophils is functional not only in vitro, but also in vivo, causing CML in the recipient mice [12,14]. The DNA in EVs could be transferred into the recipient cells, localize to and enter the nuclear membrane, and combine with transcription factor, providing direct evidence that the transferred gene can be transcribed in the recipient cells.…”

“…The transferred EV DNAs have the ability to influence the function of the recipient cells by increasing DNA-coding mRNA and protein levels [12]. Our previous study provided evidence that BCR/ABL DNA transferred by EVs from CML (chronic myeloid leukaemia) cells has pathological significance, for example in the facilitation of metastases [14]. There is increasing evidence that EVs play a pivotal role in tumorigenesis, which can occur in adjacent and remote locations.…”

Endothelial progenitor cells in hematologic malignancies

“…Exosomes purified from K562 cells are able to transfer in vitro and in vivo DNA fragments containing BCR-ABL (44). However, these are only very preliminary evidences and additional carefully controlled experiments are required to assess whether or not the transferred BCR/ABL DNA has pathophysiological significance.…”