(3fq) Engineering Macrophage Recognition of "Self" for Cancer Immunotherapy and Tissue Patterning

Immunotherapy, Phagocytosis, Protein-based Materials, Mechanobiology

Phagocytosis is the evolutionarily conserved process by which cells engulf large particulate matter including other cells. Clearance of pathogens and dead cells by macrophages or other phagocytic cells is critical for host defense and tissue homeostasis. At the same time, engulfment of healthy “self” cells must be avoided in most situations. This is achieved in part by the ubiquitous expression of the “marker of self” protein CD47, which delivers an inhibitory signal by binding to its receptor SIRPα on macrophages. By manipulating the balance between pro-phagocytic signaling (e.g., antibodies and other opsonins) and inhibitory CD47:SIRPα signaling, it may be possible to engineer phagocytic cells to achieve desired therapeutic and engineering outcomes including engulfment and clearance of tumor cells, shielding materials from immune recognition, and programmed cell removal from engineered tissues. This concept forms the basis for my proposed research directions as an independent investigator initially focusing on the following areas:

(1) Engineering better macrophages for cellular therapies This project builds on my postdoctoral research demonstrating that macrophages engulf antibody-opsonized tumor cells more readily in the absence of CD47:SIRPα signaling and stimulate adaptive immune responses under some circumstances. It remains unclear, however, how macrophages integrate diverse and potentially conflicting self and non-self signals during this process. Therefore, I propose to study downstream events following tumor cell engulfment including antigen presentation and cytokine production. These studies will inform parallel efforts to engineer monocyte/macrophage-based cellular immunotherapies using primary immune cells and induced pluripotent stem cells together with gene editing technologies to delete or rewire inhibitory pathways and introduce immunostimulatory pathways.

(2) Role of CD47 on tumor-derived extracellular vesicles (EVs) and development of tools for isolating cell-type specific EVs Extracellular vesicles are nano to micron-sized particles released by cells and are thought to be important for intercellular communication, tumor metastasis, and immunomodulation. They have also attracted considerable attention for drug delivery applications. Because EVs are derived from recycled or budded plasma membrane, they display membrane proteins including CD47. I propose to investigate how CD47 influences the circulation and immune signaling capacity of EVs, especially those derived from tumor cells. As a component of this project, I propose to develop new technologies enabling isolation of EVs originating from specific cell types in vitro and in vivo.

(3) Programmed cell removal for tissue patterning Phagocytosis is a critical process during tissue development. Inspired by sculpting of limb digits in developing embryos, I propose to use programmed cell removal by phagocytes as a tool for tissue patterning toward applications in regenerative medicine.

Postdoctoral Research: Macrophage Checkpoint Disruption for Cancer Immunotherapy

(Adviser: Dennis E. Discher, University of Pennsylvania)

In my postdoctoral research, I am developing new approaches to immunotherapy using phagocytic cells including macrophages to target cancer. I have shown that genetic knockout of CD47 from cancer cells, which disrupts the inhibitory CD47:SIRPα immune checkpoint, enhances phagocytosis in vitro and tumor clearance in vivo, but only when combined with an opsonizing anti-tumor IgG antibody. Animals that successfully cleared knockout tumors with treatment developed an endogenous IgG antibody response suggesting that adaptive immunity can feed back to enhance the effects of macrophage checkpoint disruption. Because depletion of healthy cells is a major concern with injection with anti-CD47 monoclonal antibodies being pursued clinically, I am also developing a cellular immunotherapy using adoptive transfer of bone marrow-derived phagocytic cells that are treated ex vivo with anti-SIRPα. Additional research projects in the Discher lab to which I have contributed include (1) chemical etching of polymer membranes for the study of constricted cellular migration, nuclear rupture, and DNA damage, and (2) measurement of tissue and tumor viscoelasticity by pipette aspiration rheology.

Ph.D. Thesis: “Programming Molecular Association and Viscoelastic Behavior in Protein Hydrogels”

(Adviser: David A. Tirrell, California Institute of Technology)

In my Ph.D. research, I designed, fabricated, and characterized protein-based hydrogels with the goal of developing programmable materials in which the primary protein sequence encodes macroscopic viscoelastic properties. This work combined substantial elements of materials science, molecular biology, and protein engineering. These hydrogels have applications as matrices for studying the effects of ECM viscoelasticity on cellular fate, as model systems for studying biomolecular condensates, and for developing tough soft materials with reversible, energy dissipating cross-links.

Teaching Interests

Biomaterials, Immunology, Biomolecular Engineering, Nanomedicine and Drug Delivery, Core Chemical Engineering Curriculum

My undergraduate and graduate training were both in Chemical Engineering, and I would be comfortable teaching the core undergraduate courses in transport phenomena, kinetics, and thermodynamics. My graduate and postdoctoral research and previous teaching experience has prepared me to teach courses in biotechnology and biomolecular engineering at the graduate and undergraduate levels. I envision designing graduate or advanced undergraduate level courses at the interface of immunology and chemical and biological engineering with a strong basis in recent literature. The course(s) would be a hybrid of immunological fundamentals (e.g. immune cells and tissues, immunological biomolecules and macromolecular assemblies, immune signaling) and biomedical applications (development and biomanufacturing of antibodies, vaccines, and cellular therapies, immunological assays and methods, immunological responses to biomaterials). In addition to core and elective engineering courses, I am interested in developing or coordinating a course focusing on basic research skills for graduate students and upper level undergraduates. Topics would be tailored to the specific needs of the students and potentially include data presentation and scientific illustration, library and digital resources, proposal writing and overviews of research funding organizations, responsible conduct of research, and others. I would seek to leverage existing resources at the university or within department to cover these topics.

Teaching Experience

My teaching experience includes teaching assistantships for a graduate level cell engineering course and an undergraduate (junior/senior) level biomolecular engineering laboratory. I have guest lectured (2-5 classes per semester) for Nanoscale Systems Biology and Biological Soft Matter Fundamentals courses. I view mentoring as an important component to teaching and have mentored researchers across multiple levels including undergraduates and master’s thesis students. I also supervised high students and teachers as part of summer research outreach program.