Dr. Sotiriou’s research builds on his previous BCRF-supported work, which utilized cutting edge technologies to interrogate the genomic and cellular heterogeneity in HER2-positive breast cancer. He and his team are extending this technology to assess the impact of tumor and immune cell heterogeneity on response to immunotherapy in TNBC. The team is combining multiple layers of single-cell analyses of tumor tissue from before treatment, at the start of treatment, and from residual disease at the time of surgery to build a complete picture of treatment response. They looked at 37 patients receiving different types of treatment—some got chemotherapy alone while others got a combination of chemotherapy and immunotherapy. They found that the makeup of immune cells, particularly T cells, changed during treatment, and this change differed between the groups receiving chemotherapy vs. chemotherapy and immunotherapy. The team also identified specific types of T cells that seemed to be linked with better responses to chemotherapy. Tumor profiling identified different gene expression patterns that might explain why some tumors resist treatment. Overall, the study gives us a better understanding of how the immune system responds to treatment and may ultimately enable tailored care to spare patients unnecessary side effects related to immunotherapy.