The contribution of tumor stem cells to progression and relapse of cancer is recognized as a significant clinical challenge in both solid and hematologic malignancies. Critical to understanding the mechanisms of tumor stem cell survival and self-renewal is investigation of their support by the microenvironments in which they thrive. Somewhat unique to hematopoietic malignancies, and subsequently leukemic stem cells (LSC), is an established appreciation of the contribution of the bone marrow microenvironment to regulation of cell fate. In the current study we investigate the interaction of LSC with bone marrow stromal cells (BMSC) and the mechanisms by which BMSC contribute to maintenance of the LSC phenotype. We utilize a unique population of Bcr;Abl+ (Ph+) ALL SUP-B15 cells that co-express a panel of stem cell markers, VE-cadherin, and proteins associated with commitment to the B-lineage. Following long-term co- culture (LTCC) with BMSC, SUP-B15 tumor cells demonstrate tri-lineage hematopoiesis, formed anatomically distinct three dimensional chemo-resistant hemospheres, had increased expression of the stem cell marker Oct-4, and had sustained, high levels of hypoxia inducible factor-2a (HIF-2a). SUP-B15 cells also reconstituted leukemia in NOD/SCID mice, as well as demonstrating differentiation in vivo. Destabilization of VE-cadherin increased chemotherapy-induced apoptosis of LSCs suggesting an important role for it in this novel setting. These studies are supplemented by inclusion of primary, human derived, de-identified pro/pre-B ALL cells that, consistent with the Ph+ SUP-B15 cell line utilized in our studies, express high levels of VE- cadherin, Oct-4 and HIF-2a. Using a model of LTCC of bone marrow stroma with SUP-B15 tumor cells and patient-derived samples we will test the working hypothesis that a LSC phenotype in ALL is supported by bone marrow microenvironment regulation of VE-cadherin and Oct-4 expression and stability. Our hypothesis will be tested by completion of the following specific aims: (1) To determine the contribution of VE-cadherin to LSC phenotype and the mechanism by which VE-cadherin is modulated in LSC, (2) To determine the mechanisms by which stromal cells regulate expression and activity of tumor cell Oct-4, and (3) To develop a murine model to identify the critical factors involved in initiating leukemia from sub-populations of Ph+ cells with a LSC phenotype. Our long-term goal is to identify pathways that are essential to bone marrow niche support of leukemic stem cells that are amenable to disruption, either through targeting the tumor itself, or the niche. Consequently, existing therapies may have enhanced efficacy in targeting the stem cell component of aggressive Ph+ leukemia.

Public Health Relevance

The National Cancer Institute reports that acute lymphoblastic leukemia (ALL) is the most common cancer diagnosed in children and represents 23% of cancer diagnoses among children younger than 15 years. Within ALL there are sub-types of tumors that are characteristic of high risk for relapse and poor prognosis (Ph+ ALL) in which it is particularly urgent to understand the contribution of sub-populations of cells, characterized by a stem cell phenotype, to disease progression. Understanding the mechanisms by which the Ph+ leukemic stem cell is protected by the bone marrow microenvironment will increase our ability to design novel treatment strategies that are more effective in targeting this population.

Agency
National Institute of Health (NIH)
Institute
National Cancer Institute (NCI)
Type
Research Project (R01)
Project #
5R01CA134573-04
Application #
8207303
Study Section
Tumor Progression and Metastasis Study Section (TPM)
Program Officer
Mufson, R Allan
Project Start
2009-02-01
Project End
2013-12-31
Budget Start
2012-01-01
Budget End
2012-12-31
Support Year
4
Fiscal Year
2012
Total Cost
$263,553
Indirect Cost
$84,233
Name
West Virginia University
Department
Pediatrics
Type
Schools of Medicine
DUNS #
191510239
City
Morgantown
State
WV
Country
United States
Zip Code
26506
Hare, Ian; Evans, Rebecca; Fortney, James et al. (2016) Chemotherapy-induced Dkk-1 expression by primary human mesenchymal stem cells is p53 dependent. Med Oncol 33:113
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Moses, Blake S; Slone, William L; Thomas, Patrick et al. (2016) Bone marrow microenvironment modulation of acute lymphoblastic leukemia phenotype. Exp Hematol 44:50-59.e2
Slone, William L; Moses, Blake S; Evans, Rebecca et al. (2016) Modeling Chemotherapy Resistant Leukemia In Vitro. J Vis Exp :e53645
Moses, Blake S; Evans, Rebecca; Slone, William L et al. (2016) Bone Marrow Microenvironment Niche Regulates miR-221/222 in Acute Lymphoblastic Leukemia. Mol Cancer Res 14:909-919
Hare, Ian; Gencheva, Marieta; Evans, Rebecca et al. (2016) In Vitro Expansion of Bone Marrow Derived Mesenchymal Stem Cells Alters DNA Double Strand Break Repair of Etoposide Induced DNA Damage. Stem Cells Int 2016:8270464
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Evans, R; Martin, K H; Moses, B S et al. (2015) Modeling The Bone Marrow Microenvironment's Influence on Leukemic Disease. Transl Biomed 6:
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Jajosky, Audrey N; Coad, James E; Vos, Jeffrey A et al. (2014) RepSox slows decay of CD34+ acute myeloid leukemia cells and decreases T cell immunoglobulin mucin-3 expression. Stem Cells Transl Med 3:836-48

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