Sunitinib selectively targets leukemogenic signaling of mutant SHP2 in juvenile myelomonocytic leukemia.

Leukemogenic SHP2 mutations occur in 35% of patients with juvenile myelomonocytic leukemia (JMML), a hematopoietic malignancy with poor response to cytotoxic chemotherapy. Novel therapeutic strategies are urgently needed for patients with JMML. Previously, we established a novel cell model of JMML with HCD-57, a murine erythroleukemia cell line that depends on EPO for survival. SHP2-D61Y or -E76K drove the survival and proliferation of HCD-57 in absence of EPO. In this study, we identified sunitinib as a potent compound to inhibit SHP2-mutant cells by screening a kinase inhibitor library with our model. We used cell viability assay, colony formation assay, flow cytometry, immunoblotting, and a xenograft model to evaluate the effect of sunitinib against SHP2-mutant leukemia cells in vitro and in vivo. The treatment of sunitinib selectively induced apoptosis and cell cycle arrest in mutant SHP2-transformed HCD-57, but not parental cells. It also inhibited cell viability and colony formation of primary JMML cells with mutant SHP2, but not bone marrow mononuclear cells from healthy donors. Immunoblotting showed that the treatment of sunitinib blocked the aberrantly activated signals of mutant SHP2 with deceased phosphorylation levels of SHP2, ERK, and AKT. Furthermore, sunitinib effectively reduced tumor burdens of immune-deficient mice engrafted with mutant-SHP2 transformed HCD-57. Our data demonstrated that sunitinib selectively inhibited SHP2-mutant leukemia cells, which could serve as an effective therapeutic strategy for SHP2-mutant JMML in the future.

Leukemogenic SHP2 mutations lead to erythropoietin independency of HCD-57 cells: a novel model for preclinical research of SHP2-mutant JMML.

Leukemogenic SHP2 mutations occur in 35% of patients with juvenile myelomonocytic leukemia (JMML), a rare but fatal hematopoietic malignancy without representative cell models, which are urgently needed to investigate the pathogenesis and to develop novel therapeutic strategies. In this study, we established stable cell lines with aberrant signaling resembling SHP2-mutant JMML through retroviral expression of SHP2-D61Y/E76K in HCD-57 cells, a murine erythroleukemia cell line that depends on erythropoietin (EPO) for survival. SHP2-D61Y/E76K drives the survival and proliferation of HCD-57 cells in the absence of EPO, but not in Ba/F3 cells in the absence of IL-3. Transformed HCD-57 cells showed activated MAPK signaling that is consistent with SHP2-mutant JMML. Transformed HCD-57 cells were sensitive to dasatinib and trametinib, two targeted drugs previously reported to inhibit SHP2-mutant JMML cells. Furthermore, we injected mutant SHP2-transformed HCD-57 cells into immune-deficient mice intravenously and found that these cells rapidly proliferated in the spleen and bone marrow, providing an excellent model for in vivo testing of drugs targeting the aberrant signaling of mutant SHP2. In conclusion, we established the novel cell lines HCD-57/SHP2-E76K and -D61Y that depended on signaling of mutant SHP2 for survival, thus resembling SHP2-mutant JMML. Our model is a valuable tool to investigate the pathogenic mechanisms of mutant SHP2 and targeted drugs for SHP2-mutant JMML.