Enhancement of Effector CD8 Cell Motility through Mitochondrial Metabolism

University Of Colorado Denver, Aurora CO

Investigators

Abstract

PROJECT SUMMARY: CD8 cells play a critical role in the immune response to infections as well as in prevention and restriction of cancer growth. Cytotoxicity and cytokine production have been identified as the primary mechanisms by which CD8 cells mediate their immune functions. Furthermore, chemokine-directed migration of CD8 cells is critical for their localization to lymphoid tissue for immune priming and to sites of infection and inflammation. However, after CD8 cells traffic to their target tissues, basal cell motility of effector CD8 cells within the tissue is an aspect of immunity that is poorly understood. Basal cell motility, defined as random walk and exploratory spread, is essential for effector CD8 cells to locate and engage their cell targets within inflamed tissue, such as a tumor. Little is known about the factors which could impact motility characteristics (distance, trajectory, speed) of CD8 cells. Mitochondria have been shown to play a critical role in cell motility through mitochondrial ATP and mitochondrial Ca2+. Mitochondrial Ca2+ enables cell motility through decreasing actin cytoskeleton stiffness. My recent studies show that IL-21 enhances motility of effector CD8 cells in the absence of TCR signals. I show that upon activation, effector CD8 cells expanded with IL-2 proliferate and survive but lose their cell polarity, adopting a round morphology and minimal motility capacity. In contrast, effector CD8 cells expanded with IL-2 plus IL-21 are highly motile. In addition, effector CD8 cells expanded with IL-2 plus IL-21 exhibit increased mitochondrial membrane potential, mitochondrial ATP, mitochondrial Ca2+, and in vitro cancer cell killing, compared to those expanded with IL-2 alone. In T cells IL-21 primarily signals through STAT3, and STAT3 has been shown to translocate to mitochondria and enhance mitochondrial respiration. My data also shows elevated mitochondrial STAT3 levels in CD8 cells expanded in the presence of IL-2 plus IL-21 compared to those expanded with IL-2 alone. Therefore, I propose that during the expansion of effector CD8 cells, IL-21 enhances CD8 cell motility by increasing mitochondrial ATP and/or mitochondrial Ca2+ through mitochondrial STAT3, leading to improved motility within solid tumors, which contributes to a more robust anti-tumor response. To address this hypothesis, I will: 1) Determine whether IL-21 induces effector CD8 cell motility by increasing mitochondrial ATP and/or mitochondrial Ca2+ through mitochondrial STAT3 (Aim 1) and 2) Examine whether effector CD8 cells expanded with IL-2 plus IL-21 exhibit increased motility within solid tumors and enhanced anti- tumor effects (Aim 2). This study will provide insight into improving effector CD8 cell motility through the IL-21- mitochondrial STAT3 signaling axis, which can be leveraged in modifying motility of these cells for improving adoptive T cell cancer therapies and/or reducing progression of CD8 cell-mediated autoimmune diseases, such as Type I Diabetes.