ABSTRACT
We have proposed that modified platelets could potentially be used to correct intrinsic platelet defects as well as for targeted delivery of therapeutic molecules to sights of vascular injury. Ectopic expression of proteins within α-granules prior to platelet activation has been achieved for several proteins, including urokinase, factor (F) VIII, and partially for FIX. Potential uses of platelet-directed therapeutics will be discussed, focusing on targeted delivery of urokinase as a thromboprophylactic agent and FVIII for the treatment of hemophilia A patients with intractable inhibitors. This presentation will discuss new strategies that may be useful in the care of patients with vascular injury as well as remaining challenges and limitations of these approaches.
Subject(s)
Blood Coagulation Disorders/therapy , Blood Platelet Disorders/therapy , Blood Platelets/metabolism , Gene Transfer Techniques , Genetic Therapy/methods , Platelet Transfusion , Animals , Blood Coagulation Disorders/blood , Blood Coagulation Disorders/genetics , Blood Coagulation Factors/biosynthesis , Blood Coagulation Factors/genetics , Blood Platelet Disorders/blood , Blood Platelet Disorders/genetics , Factor V Deficiency/blood , Factor V Deficiency/genetics , Factor V Deficiency/therapy , Genetic Predisposition to Disease , Hemophilia A/blood , Hemophilia A/genetics , Hemophilia A/therapy , Humans , Treatment Outcome , Urokinase-Type Plasminogen Activator/biosynthesis , Urokinase-Type Plasminogen Activator/blood , Urokinase-Type Plasminogen Activator/geneticsABSTRACT
Melanoma is the most deadly type of skin cancer, constituting annually â¼ 75% of all cutaneous cancer-related deaths due to metastatic spread. Currently, because of metastatic spread, there are no effective treatment options for late-stage metastatic melanoma patients. Studies over the past two decades have provided insight into several complex molecular mechanisms as to how these malignancies evade immunological control, indicating the importance of immune escape or suppression for tumor survival. Thus, it is essential to develop innovative cancer strategies and address immune obstacles with the goal of generating more effective immunotherapies. One important area of study is to further elucidate the role and significance of myeloid-derived suppressor cells (MDSCs) in the maintenance of the tumor microenvironment. These cells possess a remarkable ability to suppress immune responses and, as such, facilitate tumor growth. Thus, MDSCs represent an important new target for preventing tumor progression and escape from immune control. In this study, we investigated the role of MDSCs in immune suppression of T cells in an antigen-specific B16 melanoma murine system utilizing a novel synthetic tyrosinase (Tyr) DNA vaccine therapy in both prophylactic and therapeutic models. This Tyr vaccine induced a robust and broad immune response, including directing CD8 T-cell infiltration into tumor sites. The vaccine also reduced the number of MDSCs in the tumor microenvironment through the downregulation of monocyte chemoattractant protein 1, interleukin-10, CXCL5 and arginase II, factors important for MDSC expansion. This novel synthetic DNA vaccine significantly reduced the melanoma tumor burden and increased survival in vivo, due likely, in part, to the facilitation of a change in the tumor microenvironment through MDSC suppression.
Subject(s)
Cancer Vaccines/immunology , Melanoma/immunology , Melanoma/therapy , Monophenol Monooxygenase/immunology , Myeloid Cells/immunology , Vaccines, DNA/immunology , Animals , CD8-Positive T-Lymphocytes/immunology , CD8-Positive T-Lymphocytes/metabolism , Cancer Vaccines/administration & dosage , Cytokines/metabolism , Disease Models, Animal , Female , Humans , Immunity, Cellular , Immunity, Humoral , Immunization , Immunomodulation , Melanoma/genetics , Melanoma/mortality , Melanoma/pathology , Melanoma/prevention & control , Melanoma, Experimental , Mice , Monophenol Monooxygenase/antagonists & inhibitors , Monophenol Monooxygenase/genetics , Myeloid Cells/metabolism , T-Cell Antigen Receptor Specificity , Tumor Burden/immunology , Tumor Microenvironment , Vaccines, DNA/administration & dosageABSTRACT
BACKGROUND: Ectopically expressed B-domainless factor VIII in megakaryocytes is stored in α-granules, is effective in a number of murine hemostatic models, and is protected from circulating inhibitors. However, this platelet (p) FVIII has different temporal-spatial availability from plasma FVIII, with limited efficacy in other murine hemostatic models. OBJECTIVES AND METHODS: We sought to improve pFVIII hemostatic efficacy by expressing canine (c) FVIII, which has higher stability and activity than human (h) FVIII in FVIII(null) mice. RESULTS AND CONCLUSIONS: We found that pcFVIII was more effective than phFVIII at restoring hemostasis, but peak pcFVIII antigen levels were lower and were associated with greater megakaryocyte apoptosis than phFVIII. These new insights suggest that pFVIII gene therapy strategies should focus on enhancing activity rather than levels. We previously showed that modification of the PACE/furin cleavage site in hFVIII resulted in secretion of hFVIII primarily as a single-chain molecule with increased biological activity. In megakaryocytes, this variant was expressed at the same level as phFVIII with a lentiviral bone marrow transplant approach to reconstitute FVIII(null) mice, but was more effective, resulting in near-normal hemostasis in the cremaster laser injury model. These studies may have implications for pFVIII gene therapy in hemophilia A.
