Abstract 4313: Mouse model of human T-cell acute lymphoblastic leukemia stem cells

Proceedings: AACR 101st Annual Meeting 2010‐‐ Apr 17‐21, 2010; Washington, DC T-cell acute lymphoblastic leukemia (T-ALL) is a very common malignancy diagnosed in children, accounting for 15% of all pediatric ALL cases. In pediatric T-ALL, 50% of patients harbor a Notch1 activating mutation1. Patients with relapsed T-ALL have a poor prognosis and thus it is important to understand the molecular mechanisms. Leukemia stem cells (LSC) play a key role in cancer propagation and have the capacity to self-renew and differentiate. LSC have been reported in T-ALL where, following in vitro culture, CD34+/CD4—— and CD34+/CD7——subfractions of T-ALL marrow were enriched for LSC capable of engrafting leukemia in NOD/SCID mice2. However, difficulties in maintaining primary cultures of leukemia cells have hampered investigations into the biology of T-ALL underscoring the need for a direct xenotransplant model for screening candidate drugs that inhibit self-renew pathways. Candidate LSC from T-ALL patient samples (n=10) were sorted using a FACSAria. Notch1, Hes1 and c-myc expression were analyzed in sorted cells by Q-PCR and Notch1 levels were measured by FACS. In addition, key genes were sequenced from some of the samples. To develop a mouse model for human T-ALL, sorted candidate LSC were lentivirally transduced with GFP-Luciferase fusion protein (GLF) and transplanted intrahepatically into neonatal T, B, and NK cell deficient mice3. Leukemic engraftment was monitored by in vivo bioluminescence imaging. The mice were sacrificed 8 weeks after transplant; hematopoietic organs were collected for FACS analysis of human CD2, CD7, CD34 and CD45 engraftment. Finally, to assay LSC self-renewal, engrafted human CD34+ cells from the bone marrow or thymus were transplanted into secondary and tertiary recipients. While Q-PCR and FACS data showed that Notch1 levels varied among different T-ALL patients, Notch 1 expression correlated with level of engraftment. We transplanted 10 T-ALL patient samples with higher Notch1 expression and 9 of 10 samples engrafted immunocompromised mice. Transplanted LSC could be tracked 4 weeks after transplant byin vivo bioluminescent imaging and human CD34+/CD45+, CD2+/CD7+/CD45+ cells were found in hematopoietic organs of engrafted mice at 8 weeks post transplant. Importantly, the engraftment of CD34+/CD45+, CD2+/CD7+/CD45+ cell populations in hematopoietic organs derived from T-ALL patient samples correlates with the status of mutations. Finally, isolated human CD34 progenitor cells could engraft 2nd and 3rd recipients demonstrating their propensity for self-renewal and differentiation. 1. Enhanced Notch1 expression was found in T-ALL CD34+ cells. 2. Candidate T-ALL LSC (CD34+/CD4−/CD7−) give rise to CD34+/CD45+ and CD2+/CD7+/CD45+ cells in the hematopoietic organs of transplanted mice. 3. T-ALL LSC can be tracked in 1st and 2nd transplanted mice providing a robust in vivo model for testing novel self-renew pathway inhibitors. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4313.