Novel targeted therapies for chronic myelomonocytic leukemia

PROJECT SUMMARY
Chronic myelomonocytic leukemia (CMML) is an aggressive hematologic malignancy with extremely poor
survival and no effective pharmacologic therapies. The CBL gene, which encodes an E3 ubiquitin ligase and
signaling adaptor protein, is frequently mutated in CMML patients. We identified hyperactivation of the SRC
family kinase LYN as a key oncogenic driver in CBL-mutant cells. Consistent with this finding, we have also
demonstrated the in vitro and in vivo anti-proliferative effects of LYN inhibition by dasatinib in CBL-mutant cell
lines and patient-derived CMML samples, providing rationale to explore the therapeutic potential of dasatinib in
patients with CBL-mutant CMML. The development of drug resistance represents a possible challenge to the
efficacy of dasatinib in CMML patients. Thus, an understanding of dasatinib-resistance mechanisms is essential
for the design of durable therapeutic approaches in CBL-mutant CMML. Moreover, discovery of other targetable
pathways in CBL-mutant disease will guide the selection of combination therapies that prevent the emergence
of drug resistance. Indeed, we have observed that an inhibitor of SYK, fostamatinib, also has anti-proliferative
activity against CBL-mutant cell lines, presenting an opportunity to test the efficacy of combined LYN/SYK
inhibition. In Aim 1 of this proposal, I will assess dasatinib resistance and intracellular signaling in CBL-mutant
cells expressing a series of LYN and SYK alleles, including wild-type, kinase-dead, and drug-binding mutants. I
will also define genetic mechanisms of dasatinib resistance via a genome-wide CRISPR-Cas9 knockout screen
in dasatinib- or vehicle-treated cells. In Aim 2, I will assess the biological effects of combined treatment with
dasatinib and a panel of FDA-approved inhibitors of SYK in vitro and test the efficacy of dasatinib plus
fostamatinib in patient-derived xenograft murine models of CBL-mutant CMML. Altogether, the experiments
proposed here will build significantly on our previous work and lead to further progress in the discovery of
effective treatments for CMML patients. The applicant, Dr. Roger Belizaire, is a clinical pathologist and
laboratory-based investigator in the Department of Oncologic Pathology at the Dana-Farber Cancer Institute
(DFCI). He spends 80% of his time in translational research and 20% in clinical practice as a transfusion medicine
physician. He has proposed a five-year career development plan to enable the development of his independent
laboratory at the DFCI. Dr. Belizaire has assembled an Advisory Committee of world-renowned experts to
provide scientific and career mentorship. He has established collaborations with experts in myeloid neoplasia,
oncogenic signaling, and targeted cancer therapeutics to provide experimental guidance and specific training in
the field. Dr. Belizaire will conduct this research under the mentorship of Dr. Benjamin Ebert at the DFCI and
leverage the exceptional research and teaching environment at the DFCI. The DFCI, which comprises an
outstanding research community with an extensive track-record of successfully mentoring physician-scientists,
is an ideal environment for completion of these experimental and career development aims.

Grant Number: 5K08CA258803-04
NIH Institute/Center: NIH
Principal Investigator: Roger Belizaire