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Blood, 15 October 2008, Vol. 112, No. 8, pp. 3373-3382.
Prepublished online as a Blood First Edition Paper on July 28, 2008; DOI 10.1182/blood-2008-03-147587.
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NEOPLASIA
K-RasG12D–induced T-cell lymphoblastic lymphoma/leukemias harbor Notch1 mutations and are sensitive to -secretase inhibitors
Thomas Kindler1,
Melanie G. Cornejo1,
Claudia Scholl1,
Jianing Liu1,
Dena S. Leeman1,
J. Erika Haydu1,
Stefan Fröhling1,
Benjamin H. Lee1,2, and
D. Gary Gilliland1,3,4
1 Division of Hematology, Department of Medicine, and
2 Department of Pathology, Brigham & Women's Hospital;
3 Department of Medical Oncology, Dana-Farber Cancer Institute; and
4 Howard Hughes Medical Institute, Harvard Medical School, Boston, MA
To study the impact of oncogenic K-Ras on T-cell leukemia/lymphoma development and progression, we made use of a conditional K-RasG12D murine knockin model, in which oncogenic K-Ras is expressed from its endogenous promoter. Transplantation of whole bone marrow cells that express oncogenic K-Ras into wild-type recipient mice resulted in a highly penetrant, aggressive T-cell leukemia/lymphoma. The lymphoblasts were composed of a CD4/CD8 double-positive population that aberrantly expressed CD44. Thymi of primary donor mice showed reduced cellularity, and immunophenotypic analysis demonstrated a block in differentiation at the double-negative 1 stage. With progression of disease, approximately 50% of mice acquired Notch1 mutations within the PEST domain. Of note, primary lymphoblasts were hypersensitive to -secretase inhibitor treatment, which is known to impair Notch signaling. This inhibition was Notch-specific as assessed by down-regulation of Notch1 target genes and intracellular cleaved Notch. We also observed that the oncogenic K-Ras-induced T-cell disease was responsive to rapamycin and inhibitors of the RAS/MAPK pathway. These data indicate that patients with T-cell leukemia with K-Ras mutations may benefit from therapies that target the NOTCH pathway alone or in combination with inhibition of the PI3K/AKT/MTOR and RAS/MAPK pathways.

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[Abstract]
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