Project Grant F31CA298725

NEUTROPHIL-DRIVEN PRO-RECURRENT NICHE FORMATION IN MAMMARY ADIPOSE TISSUE - PROJECT SUMMARY RECURRENCE REMAINS A SIGNIFICANT CHALLENGE FOR TRIPLE NEGATIVE BREAST CANCER (TNBC) PATIENTS DESPITE TREATMENT WITH SURGERY, CHEMOTHERAPY, AND RADIOTHERAPY (RT). ALTHOUGH IRRADIATION OF THE RESECTED TUMOR BED DECREASES RECURRENCE IN MOST PATIENTS, PATIENTS WITH CHRONIC LYMPHOPENIA AND A HIGH NEUTROPHIL-TO-LYMPHOCYTE RATIO (NLR) FOLLOWING RT EXPERIENCE RELAPSE AT HIGH RATES. THE MECHANISMS UNDERLYING THIS ASSOCIATION OF HIGH NLR WITH RECURRENCE ARE POORLY UNDERSTOOD. HOWEVER, A GROWING BODY OF LITERATURE SHOWS THAT IRRADIATION OF MAMMARY ADIPOSE TISSUE INITIATES AN INNATE IMMUNE CELL-DRIVEN PROGRAM THAT FACILITATES TUMOR CELL RESEEDING. ADDITIONALLY, PRELIMINARY EVIDENCE SUGGESTS THAT IRRADIATION PROMOTES RECURRENCE VIA NEUTROPHIL-MEDIATED VASCULAR REMODELING AND SENESCENCE. THEREFORE, THE CENTRAL HYPOTHESIS OF THIS PROPOSAL IS THAT NEUTROPHILS FACILITATE FORMATION OF A PRO-RECURRENT NICHE IN IRRADIATED MAMMARY ADIPOSE TISSUE THROUGH RELEASE OF PRO-INFLAMMATORY PROTEINS AND IN- DUCTION OF VASCULAR REMODELING WHEN PRIMED BY SENESCENT CELLS. THE RATIONALE FOR THE PROPOSED RESEARCH IS THAT UNDERSTANDING THE IMPACT OF POST-THERAPY IMMUNE CELL INFILTRATION ON TUMOR CELL RESEEDING AND VASCULAR REMODEL- ING WILL IDENTIFY CANDIDATES FOR TARGETED THERAPIES. THE CENTRAL HYPOTHESIS WILL BE TESTED BY PURSUING TWO SPECIFIC AIMS: 1) DETERMINE NEUTROPHIL PHENOTYPES AND FUNCTIONS ASSOCIATED WITH TUMOR CELL RESEEDING IN IRRADIATED ADI- POSE TISSUE; AND 2) IDENTIFY THE EFFECT OF NEUTROPHIL ACTIVATION ON PRO-ANGIOGENIC SIGNALING AND VASCULAR REMODEL- ING. IN AIM 1, I WILL USE A LYMPHOPENIC MOUSE MODEL TO REPRESENT AT-RISK PATIENT POPULATIONS AND ESTABLISH HOW NEUTROPHIL INFILTRATION TO IRRADIATED MAMMARY ADIPOSE TISSUE FACILITATES RECURRENCE. TO CONFIRM THAT NEUTROPHILS ARE NECESSARY AND SUFFICIENT FOR TUMOR CELL RECRUITMENT INTO ADIPOSE TISSUE, I WILL DEVELOP A NEUTROPHIL-DEPLETED MOUSE MODEL. IN AIM 2, I WILL DETERMINE THE INFLUENCE OF THE SENESCENT ENDOTHELIAL CELL SECRETOME ON NEUTROPHIL ACTIVA- TION, USING A WELL-CHARACTERIZED MICROFLUIDIC MODEL OF THE MAMMARY VASCULATURE TO ANALYZE HOW THIS ACTIVATION PROMOTES NF-KB AND PRO-ANGIOGENIC SIGNALING IN ENDOTHELIAL CELLS. I WILL THEN EVALUATE THE IMPACT OF NEUTROPHIL PROTEINS ON NF-KB SIGNALING AND VASCULAR REMODELING AS WELL AS ON TUMOR CELL RECRUITMENT TO IRRADIATED ADIPOSE TISSUE IN VIVO. THESE STUDIES WILL IDENTIFY MECHANISMS OF NEUTROPHIL-MEDIATED VASCULAR REMODELING AND TUMOR CELL RESEEDING AFTER RT, PROVIDING TWO POTENTIAL POINTS OF INTERVENTION TO PREVENT RECURRENCE IN PATIENTS WITH TNBC.