DIFFERENTIAL MECHANISMS OF CELL DEATH INDUCTION VIA DELIVERY OF THERAPEUTIC NANOLIPOSOMAL CERAMIDE IN LEUKEMIAS

Open Access
- Author:
- Ryland, Lindsay Kate
- Graduate Program:
- Pharmacology
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- July 28, 2011
- Committee Members:
- Mark Kester, Dissertation Advisor/Co-Advisor
Mark Kester, Committee Chair/Co-Chair
Thomas Loughran, Committee Member
Hong Gang Wang, Committee Member
Jin Ming Yang, Committee Member
Richard Robert Young, Committee Member - Keywords:
- sphingolipid
ceramide
nanoliposome
chronic lymphocytic leukemia - Abstract:
- Large granular lymphocyte (LGL) leukemia is a rare lymphoproliferative malignancy that involves blood, bone marrow and spleen infiltration. Clinically, LGL leukemia can manifest as a chronic lymphocytosis or as an aggressive leukemia that is fatal within a short period of time. A segment of LGL leukemia patients are unresponsive to immunosuppressive therapy and currently there is no known curative treatment for this disease. Another hematological malignancy, chronic lymphocytic leukemia (CLL) is the most prevalent leukemia in adults in Western countries and accounts for approximately 30% of all diagnosed leukemia cases. Around 95% of all CLL cases involve clonal expansion and abnormal proliferation of neoplastic B lymphocytes in lymphoid organs, bone marrow and peripheral blood. Similar to LGL leukemia, CLL is also incurable with current therapies. Therefore, this represents a need for new therapeutic approaches for treatment of these diseases. Recent advances in nanotechnology have illustrated the feasibility of generating nanoliposomes that encapsulate hydrophobic compounds, like ceramide, to facilitate treatment of LGL leukemia and CLL. Ceramide is an anti-proliferative sphingolipid metabolite that has been shown to selectively induce cell death in cancer cells. However, the use of ceramide as a chemotherapeutic agent is limited due to hydrophobicity. While it is understood how nanoliposomal ceramide induces cell death in several types of cancers and hematological malignancies, the effect of nanoliposomal ceramide treatment in LGL leukemia and CLL remains unclear. In this study, we investigate the differential mechanisms of cell death induction following nanoliposomal C6-ceramide treatment in both LGL leukemia and CLL. We show that nanoliposomal C6-ceramide displays minimal cytotoxicity in normal donors‟ peripheral blood mononuclear cells (PBMCs) and is a well-tolerated therapy during in vivo treatment in these leukemia models. To further examine this mechanism of selectivity, we utilize CLL as a cancer model which has an increased dependency on glycolysis. As most tumors exhibit a preferential switch to glycolysis, as described in the “Warburg effect,” we hypothesize that ceramide nanoliposomes selectively target this activated glycolytic pathway in cancer. We demonstrate that nanoliposomal ceramide inhibits both the RNA and protein expression of glyceraldehyde-3-phosphate dehydrogenase (GAPDH), an intermediate enzyme in the glycolytic pathway, which is overexpressed in a subset of CLL patients. Taken together, our results suggest that C6-ceramide nanoliposomes preferentially inhibit the enhanced metabolism of glucose in leukemic CLL cells, which results in induction of cell death. We conclude that selective inhibition of the glycolytic pathway in CLL cells with nanoliposomal C6-ceramide could potentially be an effective therapy for this leukemia by targeting the Warburg effect. In addition, we conclude that nanoliposomal C6-ceramide could also be an effective therapy for patients with LGL leukemia. Collectively, the results of this dissertation emphasize exploitation of sphingolipids and sphingolipid metabolism in design and development of novel chemotherapeutics.