Project Summary Breast cancer has been the most prevalent cancer and the second leading cause of cancer-related death in American women for many years. Immune checkpoint inhibitors (ICIs) targeting checkpoint proteins such as programmed cell death protein 1 (PD1) resulted in durable clinical remissions in a subset of cancer patients, including breast cancer. However, most patients didn’t show a response to ICI treatment, urging the need for novel biomarkers that can predict patient response and therapeutic targets that can improve the efficacy and durability of ICIs. The goal of this proposal is to investigate how to overcome the ICI resistance. My preliminary data showed that interferon (IFN) -alpha and -gamma signaling are enriched in the tumor and blood neutrophils of nonresponders to ICIs. The central hypothesis of this proposal is that tumor-educated neutrophils with increased IFN signaling mediate breast cancer resistance to ICIs, and can be used as predictive biomarkers. During the K99 phase, I will explore the impact of neutrophil-restricted IFN signaling on tumor response to ICIs and characterize the neutrophil-specific interferon-stimulated gene (ISG) signature (Aim 1). Since we found that ISGs in peripheral blood neutrophils can predict breast cancer response to anti-PD1 therapy, I will determine if blood neutrophil ISGs signature can serve as a biomarker in other cancer types and human patient samples from the clinic and clinical trials (Aim 2, K99 and R00). Finally, I will study the neutrophil IFN signaling in regulating immune memory and durable response to ICIs (Aim 3, R00). Upon successful completion of the Specific Aims, this translational study will extend our knowledge of neutrophil IFN signaling and provide novel biomarkers for the ICI therapy and therapeutic targets to overcome the ICI resistance. My overall career goal is to establish an independent translational cancer research group that will improve understanding of cancer development, identify novel effective therapies, and train the next generation of cancer researchers. This proposed research in the K99 phase will take place in the Lester and Sue Smith Breast Center at Baylor College of Medicine, a highly collaborative and multidisciplinary environment with strong integration of basic, translational, and clinical research. The institution is dedicated to the career development of postdoctoral trainees, and provides a variety of training venues including bioinformatics and immunology, weekly seminars, R&D workshops, journal clubs, and the annual retreat. BCM is part of the Texas Medical Center, the largest medical city in the world consisting of over 60 medical institutions and hospitals, which offers me enormous opportunities for training and collaboration. Finally, I will meet with Drs. Rosen and Zhang weekly to discuss my projects besides our weekly lab meetings and have a formal committee meeting every three months to discuss my progress and receive feedback. I am also supported by a patient advocate and other collaborators. Through the training and research plan proposed within my K99/R00 application, I will acquire knowledge and skills which will greatly improve my ability to launch my scientific career as an independent investigator.

Project Narrative FDA has approved the use of immune checkpoint inhibitors in combination with chemotherapy for triple-negative breast cancer patients, however, half of the patients do not respond. The proposed research will elucidate mechanisms underlying breast cancer patient resistance to immune checkpoint inhibitors. This project will identify novel biomarkers to predict patient response and therapeutic targets to improve the efficacy and durability of immune checkpoint inhibitors.