Clinical Focus

  • Anatomic Pathology

Academic Appointments

  • Clinical Instructor, Pathology

Professional Education

  • Doctor of Medicine, University of Florida (2015)
  • Bachelor of Arts, New College of Florida (2009)
  • Board Certification: Anatomic Pathology, American Board of Pathology (2019)
  • Fellowship:Stanford University Pathology Fellowships (2018) CA
  • Residency:Stanford University Department of Pathology (2018) CA
  • Medical Education:Univeristy of Florida College of Medicine (2015) FL

Stanford Advisors

All Publications

  • Endothelin receptor emerges as a potential target of Hoxa9-mediated leukemogenesis LEUKEMIA RESEARCH Gars, E., Kaur, S., Thomas, D. 2018; 75: 69–70
  • Bone marrow histomorphological criteria can accurately diagnose hemophagocytic lymphohistiocytosis HAEMATOLOGICA Gars, E., Purington, N., Scott, G., Chisholm, K., Gratzinger, D., Martin, B. A., Ohgami, R. S. 2018; 103 (10): 1635–41
  • A replicable CD271+ mesenchymal stromal cell density score: bringing the dysfunctional myelodysplastic syndrome niche to the diagnostic laboratory. Leukemia & lymphoma Gars, E., Yousry, S. M., Babu, D., Kurzer, J. H., George, T. I., Gratzinger, D. 2016: 1-3

    View details for PubMedID 27808583

  • Endothelial cell derived angiocrine support of acute myeloid leukemia targeted by receptor tyrosine kinase inhibition. Leukemia research Drusbosky, L., Gars, E., Trujillo, A., McGee, C., Meacham, A., Wise, E., Scott, E. W., Cogle, C. R. 2015; 39 (9): 984–89


    In acute myeloid leukemia (AML), refractory disease is a major challenge and the leukemia microenvironment may harbor refractory disease. Human AML cell lines KG-1 and HL-60 expressed receptors also found on endothelial cells (ECs) such as VEGFRs, PDGFRs, and cKit. When human AML cells were co-cultured with human umbilical vein endothelial cells (HUVECs) and primary bone marrow endothelial cell (BMECs), the AML cells were more resistant to cytarabine chemotherapy, even in transwell co-culture suggesting angiocrine regulation. Primary BMECs secreted significantly increased levels of VEGF-A and PDGF-AB after exposure to cytarabine. Pazopanib, a receptor tyrosine kinase inhibitor (RTKI) of VEGFRs, PDGFRs, and cKit, removed EC protection of AML cells and enhanced AML cell sensitivity to cytarabine. Xenograft modeling showed significant regression of AML cells and abrogation of BM hypervascularity in RTKI treated cohorts. Together, these results show direct cytotoxicity of RTKIs on AML cells and reversal of EC protection. Combining RTKIs with chemotherapy may serve as promising therapeutic strategy for patients with AML.

    View details for DOI 10.1016/j.leukres.2015.05.015

    View details for PubMedID 26189107

  • Activation of the vascular niche supports leukemic progression and resistance to chemotherapy. Experimental hematology Poulos, M. G., Gars, E. J., Gutkin, M. C., Kloss, C. C., Ginsberg, M., Scandura, J. M., Rafii, S., Butler, J. M. 2014; 42 (11): 976–86.e3


    Understanding the intricate cellular components of the bone marrow microenvironment can lead to the discovery of novel extrinsic factors that are responsible for the initiation and progression of leukemic disease. We have shown that endothelial cells (ECs) provide a fertile niche that allows for the propagation of primitive and aggressive leukemic clones. Activation of the ECs by vascular endothelial growth factor (VEGF)-A provides cues that enable leukemic cells to proliferate at higher rates and also increases the adhesion of leukemia to ECs. Vascular endothelial growth factor A-activated ECs decrease the efficacy of chemotherapeutic agents to target leukemic cells. Inhibiting VEGF-dependent activation of ECs by blocking their signaling through VEGF receptor 2 increases the susceptibility of leukemic cells to chemotherapy. Therefore, the development of drugs that target the activation state of the vascular niche could prove to be an effective adjuvant therapy in combination with chemotherapeutic agents.

    View details for DOI 10.1016/j.exphem.2014.08.003

    View details for PubMedID 25179751

    View details for PubMedCentralID PMC4254082

  • Human ESC-derived hemogenic endothelial cells undergo distinct waves of endothelial to hematopoietic transition. Blood Rafii, S., Kloss, C. C., Butler, J. M., Ginsberg, M., Gars, E., Lis, R., Zhan, Q., Josipovic, P., Ding, B. S., Xiang, J., Elemento, O., Zaninovic, N., Rosenwaks, Z., Sadelain, M., Rafii, J. A., James, D. 2013; 121 (5): 770–80


    Several studies have demonstrated that hematopoietic cells originate from endotheliumin early development; however, the phenotypic progression of progenitor cells during human embryonic hemogenesis is not well described. Here, we define the developmental hierarchy among intermediate populations of hematopoietic progenitor cells (HPCs) derived from human embryonic stem cells (hESCs). We genetically modified hESCs to specifically demarcate acquisition of vascular (VE-cadherin) and hematopoietic (CD41a) cell fate and used this dual-reporting transgenic hESC line to observe endothelial to hematopoietic transition by real-time confocal microscopy. Live imaging and clonal analyses revealed a temporal bias in commitment of HPCs that recapitulates discrete waves of lineage differentiation noted during mammalian hemogenesis. Specifically, HPCs isolated at later time points showed reduced capacity to form erythroid/ megakaryocytic cells and exhibited a tendency toward myeloid fate that was enabled by expression of the Notch ligand Dll4 on hESC-derived vascular feeder cells. These data provide a framework for defining HPC lineage potential, elucidate a molecular contribution from the vascular niche in promoting hematopoietic lineage progression, and distinguish unique subpopulations of hemogenic endothelium during hESC differentiation.Live imaging of endothelial to hematopoietic conversion identifies distinct subpopulations of hESC-derived hemogenic endothelium. Expression of the Notch ligand DII4 on vascular ECs drives induction of myeloid fate from hESC-derived hematopoietic progenitors.

    View details for DOI 10.1182/blood-2012-07-444208

    View details for PubMedID 23169780

  • Development of a vascular niche platform for expansion of repopulating human cord blood stem and progenitor cells. Blood Butler, J. M., Gars, E. J., James, D. J., Nolan, D. J., Scandura, J. M., Rafii, S. 2012; 120 (6): 1344–47


    Transplantation of ex vivo expanded human umbilical cord blood cells (hCB) only partially enhances the hematopoietic recovery after myelosuppressive therapy. Incubation of hCB with optimal combinations of cytokines and niche cells, such as endothelial cells (ECs), could augment the efficiency of hCB expansion. We have devised an approach to cultivate primary human ECs (hECs) in serum-free culture conditions. We demonstrate that coculture of CD34(+) hCB in direct cellular contact with hECs and minimal concentrations of thrombopoietin/Kit-ligand/Flt3-ligand resulted in a 400-fold expansion of total hematopoietic cells, 150-fold expansion of CD45(+)CD34(+) progenitor cells, and 23-fold expansion of CD45(+) Lin(-)CD34(hi+)CD45RA(-)CD49f(+) stem and progenitor cells over a 12-day period. Compared with cytokines alone, coculture of hCB with hECs permitted greater expansion of cells capable of multilineage engraftment and serial transplantation, hallmarks of long-term repopulating hematopoietic stem cells. Therefore, hECs establish a cellular platform for expansion of hematopoietic stem and progenitor cells and treatment of hematologic disorders.

    View details for DOI 10.1182/blood-2011-12-398115

    View details for PubMedID 22709690

    View details for PubMedCentralID PMC3418723