Contributions
Abstract: S816
Type: Oral Presentation
Presentation during EHA23: On Saturday, June 16, 2018 from 12:15 - 12:30
Location: Room A4
Background
Our studies have focused on characterizing a role for the lipid phosphatase Inositol polyphosphate 4-phosphate Type II (INPP4B) in Acute Myeloid Leukemia (AML). We have previously published data showing that elevated INPP4B expression in AML patients is predictive of lower response rates to induction chemotherapy and lower overall survival. We have since revealed that INPP4B protein plays a critical role in both human and murine HSC maintenance
Aims
To investigate the role of INPP4B in hematopoiesis and leukemia and how this contributes to leukemogenesis, both in vitro and in vivo.
Methods
We make use of Inpp4b-/- C57/BL6 mice to study the contribution of Inpp4b to the HSC niche. Functional studies of Inpp4b-/- HSCs were carried out in vivo (competitive transplant into CD45.1 B6.SJL mice) and in vitro (CFC assays). Leukemia models of Inpp4b-loss were generated by retroviral transduction of bone-marrow with MLL-AF9. A combination of in vivo transplants, in vitro CFC assays, mass cytometry and next-generation sequencing were utilized to study the contribution of Inpp4b to leukemia.
Results
We show compelling evidence that INPP4B expression is significantly enriched in human and mouse hematopoietic stem and progenitor cells (HSPC). Inpp4b-/- mice show a disrupted bone-marrow stem-niche with reduced long-term HSC, MPP and GMP compared to wild-type controls (49.1%, 32.4% and 19.7% respectively). Functional studies of Inpp4b in HSPC by competitive transplant of bone marrow demonstrated that Inpp4b-/- cells show a greatly diminished contribution to the myeloid compartment in secondary and tertiary transplants. Similarly, serial 5’-fluorouracil injections demonstrate a reduced overall survival of Inpp4b-/- mice compared to wild-type controls, indicating an impaired ability of Inpp4b-/- HSCs to repopulate the hematopoietic system post-insult.
Investigating INPP4B expression in a human primary AML patient sample grown in culture, we show its expression correlates with more primitive populations (CD34+CD38-). To further study the role of INPP4B in primitive leukemia populations we modeled Inpp4b-loss in an MLL-AF9 murine leukemia model. Transplanting MLL-AF9 leukemias into recipient mice in limiting dilution showed that loss of Inpp4b reduces the frequency of leukemia initiating cells (LICs), and increases disease latency. We also show in this model of Inpp4b-loss sensitizes the leukemia model to a 7-day regimen of cytarabine treatment in vivo. Mass-cytometry analysis showed that Inpp4b-loss leads to a more differentiated phenotype, with altered surface marker expression such as Gr-1, c-Kit, Flt3, CD117 and CD44. Also, next-generation sequencing demonstrated a transcriptional profile associated with loss of stem-related genes and upregulation of genes associated with differentiation in Inpp4b-/- MLL-AF9 leukemias.
Conclusion
Our results indicate that Inpp4b plays a role in maintaining stemness, and that Inpp4b loss leads to differentiation and chemosensitization of leukemia in vivo. We hypothesize that INPP4B plays a critical role in HSC maintenance and contributes to worse leukemia, and that its stem-related function is responsible for the poor therapy response observed in patients with elevated INPP4B.
Session topic: 3. Acute myeloid leukemia - Biology & Translational Research
Keyword(s): Acute Myeloid Leukemia, Chemosensitivity, Hematopoietic Stem Cell, Stem and progenitor cell
Abstract: S816
Type: Oral Presentation
Presentation during EHA23: On Saturday, June 16, 2018 from 12:15 - 12:30
Location: Room A4
Background
Our studies have focused on characterizing a role for the lipid phosphatase Inositol polyphosphate 4-phosphate Type II (INPP4B) in Acute Myeloid Leukemia (AML). We have previously published data showing that elevated INPP4B expression in AML patients is predictive of lower response rates to induction chemotherapy and lower overall survival. We have since revealed that INPP4B protein plays a critical role in both human and murine HSC maintenance
Aims
To investigate the role of INPP4B in hematopoiesis and leukemia and how this contributes to leukemogenesis, both in vitro and in vivo.
Methods
We make use of Inpp4b-/- C57/BL6 mice to study the contribution of Inpp4b to the HSC niche. Functional studies of Inpp4b-/- HSCs were carried out in vivo (competitive transplant into CD45.1 B6.SJL mice) and in vitro (CFC assays). Leukemia models of Inpp4b-loss were generated by retroviral transduction of bone-marrow with MLL-AF9. A combination of in vivo transplants, in vitro CFC assays, mass cytometry and next-generation sequencing were utilized to study the contribution of Inpp4b to leukemia.
Results
We show compelling evidence that INPP4B expression is significantly enriched in human and mouse hematopoietic stem and progenitor cells (HSPC). Inpp4b-/- mice show a disrupted bone-marrow stem-niche with reduced long-term HSC, MPP and GMP compared to wild-type controls (49.1%, 32.4% and 19.7% respectively). Functional studies of Inpp4b in HSPC by competitive transplant of bone marrow demonstrated that Inpp4b-/- cells show a greatly diminished contribution to the myeloid compartment in secondary and tertiary transplants. Similarly, serial 5’-fluorouracil injections demonstrate a reduced overall survival of Inpp4b-/- mice compared to wild-type controls, indicating an impaired ability of Inpp4b-/- HSCs to repopulate the hematopoietic system post-insult.
Investigating INPP4B expression in a human primary AML patient sample grown in culture, we show its expression correlates with more primitive populations (CD34+CD38-). To further study the role of INPP4B in primitive leukemia populations we modeled Inpp4b-loss in an MLL-AF9 murine leukemia model. Transplanting MLL-AF9 leukemias into recipient mice in limiting dilution showed that loss of Inpp4b reduces the frequency of leukemia initiating cells (LICs), and increases disease latency. We also show in this model of Inpp4b-loss sensitizes the leukemia model to a 7-day regimen of cytarabine treatment in vivo. Mass-cytometry analysis showed that Inpp4b-loss leads to a more differentiated phenotype, with altered surface marker expression such as Gr-1, c-Kit, Flt3, CD117 and CD44. Also, next-generation sequencing demonstrated a transcriptional profile associated with loss of stem-related genes and upregulation of genes associated with differentiation in Inpp4b-/- MLL-AF9 leukemias.
Conclusion
Our results indicate that Inpp4b plays a role in maintaining stemness, and that Inpp4b loss leads to differentiation and chemosensitization of leukemia in vivo. We hypothesize that INPP4B plays a critical role in HSC maintenance and contributes to worse leukemia, and that its stem-related function is responsible for the poor therapy response observed in patients with elevated INPP4B.
Session topic: 3. Acute myeloid leukemia - Biology & Translational Research
Keyword(s): Acute Myeloid Leukemia, Chemosensitivity, Hematopoietic Stem Cell, Stem and progenitor cell