Lin F, Monaco G, Sun T, Liu J, Lin H, Stephens C, Belmont J, Arlinghaus RB. BCR gene expression blocks Bcr-Abl induced pathogenicity in a mouse model.
Oncogene 2001;
20:1873-81. [PMID:
11313935 DOI:
10.1038/sj.onc.1204409]
[Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2000] [Revised: 02/14/2001] [Accepted: 02/20/2001] [Indexed: 11/08/2022]
Abstract
It is well accepted that the Bcr-Abl oncoprotein encoded by the Philadelphia chromosome is responsible for causing chronic myelogenous leukemia (CML). We have previously demonstrated that expression of Bcr interferes with the oncogenic effects of Bcr-Abl. To examine the effects of increased Bcr expression on Bcr-Abl oncogenic effects in a more physiological system, we tested the leukemogenic potential of a clone of K562 cells (K6 K562) containing an inducible BCR gene in NOD/scid mice. In this clone, the BCR gene was placed under the control of a tetracycline (Tet) repression system with a cytomegalovirus (CMV) promoter. Induction of exogenous Bcr protein by removal of Tet from the culture medium caused a dramatic increase in Bcr serine kinase activity, yielding predominantly phosphoserine Bcr, despite the presence of Bcr-Abl in the kinase reaction mixture. Prior to induction, the endogenous Bcr was predominantly in the phosphotyrosine form because of phosphorylation by Bcr-Abl, which we previously have shown suppresses Bcr serine/threonine kinase activity. Injection of K6 K562 cells into NOD/scid mice under conditions where BCR expression was suppressed resulted in death or terminal illness in 100% of the mice within 35 days after injection. These mice had a severe wasting syndrome characterized by atrophy of bone marrow hematopoiesis, and/or neoplasia of liver, bone marrow and spleen. Neoplastic spleens from these mice usually contained b3a2 Bcr-Abl transcripts. In contrast, induction of BCR expression at the time of injection allowed 80% survival; these healthy mice had no detectable microscopic lesions in blood forming organs. This difference in survival was significant with P<0.0001. Of interest, mice that were fed Tet for 19 days to initiate the disease syndrome and then released from the BCR transcriptional block had a significantly better survival pattern than mice exposed to Tet throughout the entire period. Moreover, 30% of these mice (three mice) survived through day 50. We conclude from these findings that BCR gene expression strongly inhibits the oncogenic effects of Bcr-Abl in NOD/scid mice, yielding healthy mice in most cases.
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