An Artificial Chromosome-Based System as a Novel Delivery Strategy for CAR-T Cell Therapy of Ovarian Cancer
Abstract
Ovarian cancer remains one the leading cause of cancer death among women in the United States. The incidence rates remained relatively stable over the last decade, but patient survival remained static. Unfortunately, most cases are diagnosed in advanced stages of the disease, when all common treatments by surgery or chemotherapy are limited. The only major innovation in therapy of ovarian cancer during the 21st century has been the introduction of poly-ADP Ribose polymerase inhibitors (PARPi), but benefits are limited to patients with significant mutations in DNA repair. Thus, new therapeutic strategies are needed to improve therapeutic response in patients with ovarian cancer. Recent progress in immunotherapy in other malignancies has stimulated the development of new strategies in ovarian cancer treatment. One cancer immunotherapy of high potential is to modify the patient’s own immune cells using chimeric antigen receptors (CARs) delivered by viruses to T-cells. These CAR T-cells have high efficiency in treatment of hematological tumors. However, their use to treat solid tumors has been challenging because of the unique tumor microenvironment (TME) of solid tumors. TME impedes access, shortens survival, and strongly suppresses T-cells’ (or CAR T-cells’) anti-tumor responses. In efforts to overcome the cumulative suppressive effect of TME, CAR T-cells were additionally armed by co-delivery of other immunoactive agents to improve the CAR T-cells persistence, traffic into the TME, prevent T-cell downregulation, and increase anti-tumor activity. But the problem is that current genes delivery strategies have very limited capacity and typically are only able to introduce one or two protein agents to reinforce CAR T-cells’ function (armored CAR T-cells). Armored CAR T-cells show measurably better effects in treatment of solid tumors, but the limited studies in humans have not shown breakthrough efficacy. We suggest more potent new strategies for CAR T-cell-based ovarian cancer treatment that may overcome this limitation. The combination of CAR T-cell therapy with bispecific diabodies and multiple agents, including IL12, IL18, the CD40L gene, chemokine receptor CXCR3, PD-1 blocking, and anti- CSF1 single-chain variable fragments, should enhance the ability of T-cells to penetrate, attract, activate, and resist hostile TME and the cytotoxic activity of modified T-cells toward tumor cells. But such a strategy encounters two main problems which need to be solved: transgene silencing and the small amount of genetic material that can be successfully integrated into adoptive T-cells by a wide range of viral and non-viral vectors. Using a new, efficient gene delivery system with unlimited capacity represents a very promising therapeutic option: development of the new generation of Human Artificial Chromosomes (HACs) can overcome all of these limitations. HACs share many common features with natural human chromosomes, but have much smaller size. Thus, HACs can independently propagate and segregate during cell division like a 47th chromosome without integration into the human genome and provide long-term stable therapeutic genes expression. We are planning to construct six increasingly complex HACs with multiple therapeutic transgenes for testing in cells and in mice. They will include therapeutic bispecific antibodies, CARs, and additional agents like cytokine IL12, CD40L ligand, chemokine receptor CXCR3, and checkpoint inhibitors PD-1 blocking scFv or anti-CSF1 (see above) to improve T-cells’ resistance to TME. Tracking/imaging genes (fluorescence proteins) and suicide genes (Thymidine Kinase) will be included for safety reasons to the HACs to delete such modified T-cells for toxicity reasons or after completion of their therapeutic effect. We will perform a battery of functional tests based on cultured cells and mouse models to demonstrate a better therapeutic effect of the T-cells propagating HACs wit
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Mar 10, 2021
- Source ID
- W81XWH2010252
Entities
People
- David Spriggs
Organizations
- Massachusetts General Hospital
- United States Army