Dr. Nicolas Jose Llosa, MD

As an Associate Professor of Pediatrics and Oncology, Dr. Llosa’s research focuses on developing and advancing immunotherapy approaches for sarcomas, with an emphasis on understanding how the immune system interacts with these tumors and how those interactions can be therapeutically exploited. Sarcomas are a diverse group of cancers that arise in bone and soft tissues, including muscle, fat, blood vessels, nerves, and other connective tissues. They can occur at any age, although several sarcoma subtypes, including rhabdomyosarcoma, Ewing sarcoma, and osteosarcoma, disproportionately affect children, adolescents, and young adults. Because sarcomas encompass many biologically distinct diseases, treatment depends on the specific tumor type, location, stage, molecular characteristics, and other clinical factors. Despite important advances in surgery, radiation therapy, and chemotherapy, outcomes remain poor for many patients with recurrent, metastatic, or treatment-resistant disease, highlighting the need for new therapeutic strategies. Dr. Llosa’s laboratory investigates the sarcoma tumor immune microenvironment to better understand why some tumors are recognized and attacked by the immune system while others remain immunologically resistant. A major goal of this work is to identify mechanisms that suppress effective antitumor immunity and to develop strategies that can restore or enhance immune responses against sarcoma cells. A central area of interest is cancer immunotherapy, a group of treatments designed to harness or strengthen the body's natural immune defenses against cancer. Immunotherapeutic approaches can work by enhancing the ability of immune cells to recognize tumor cells, reversing mechanisms of immune suppression, stimulating antitumor immune responses, or directly targeting molecules expressed by cancer cells or cells within the tumor microenvironment. These strategies include immune checkpoint inhibitors, monoclonal antibodies, cellular therapies, cancer vaccines, and other immune-modulating agents. Particular emphasis is placed on immune checkpoint pathways, which normally serve as regulatory mechanisms that prevent excessive or inappropriate immune activation. Tumors can exploit these pathways to evade immune surveillance. Molecules such as PD-1, PD-L1, CTLA-4, and other inhibitory receptors and ligands can limit the activity of tumor-reactive T cells and other immune populations. Drugs that block these inhibitory signals have transformed the treatment of several cancers by restoring antitumor immune activity and, in a subset of patients, producing deep and durable clinical responses. However, most sarcomas have not demonstrated the same degree of responsiveness to immune checkpoint blockade observed in cancers such as melanoma and certain lung, kidney, and other malignancies. Understanding the biological basis for this resistance is therefore a major focus of Dr. Llosa’s research. His work examines the composition, organization, and functional state of immune cells within sarcoma tumors, including T cells, B cells, macrophages, dendritic cells, and other components of the tumor microenvironment. The laboratory also studies immune structures and signaling pathways that may predict response to immunotherapy or represent new therapeutic targets. Using approaches that integrate multiplex tissue imaging, flow cytometry, single-cell RNA sequencing, spatial transcriptomics, immune-receptor sequencing, molecular profiling, and translational laboratory models, Dr. Llosa’s research seeks to define the mechanisms that shape antitumor immunity across different sarcoma subtypes. These studies are designed not only to identify biomarkers of immune response and resistance, but also to generate rational combinations of immunotherapies with other treatments that can be translated into clinical trials. The overarching objective of this research program is to develop more effective, durable, and biologically informed treatments for patients with sarcoma, particularly children and yo