PROJECT SUMMARY/ABSTRACT The project titled “Oncogenic Synapses: cell-cell contacts enabling trogocytic-based metabolic interactions between pancreatic cancer and fibroblastic stromal cells” directly addresses the NCI Provocative Question (PQ) #7 in seeking advancement in understanding of the pathognomonic significance and functions of newly described synapse-like heterotypic cell-cell contacts formed between carcinoma cells and cancer-associated fibroblasts (CAFs). CAFs are known to provide cancer cells with nutrients and reciprocally- induced signaling inputs. Pancreatic cancer (PC), particularly pancreatic ductal adenocarcinoma, is an extreme example of preponderance of stroma in which particular CAF characteristics confer negative prognosis. Our combined and highly complementary preliminary findings serve as a basis to study the previously uncharacterized heterotypic cell-cell “oncogenic synapse” structure and its PC supportive function. Two specific aims will test the hypothesis that PC cells depend on NTNG1-NGL1 engagement to form oncogenic synapses and consume cholesterol via Wnt5a-regulated Ca2+ and phosphatidylserine (PtdSer)-dependent trogocytosis. Aim 1 will define the molecular requirements for NTNG1-NGL1 engagement and functional oncogenic synapse formation. Molecular engineering of NTNG1 and NGL1 proteins and microscopy imaging will define the structural and functional particulars of the oncogenic synapses formed between CAF and PC cells. Aim 2 will determine the importance of NTNG1/NGL1-mediated oncogenic synapses in trogocytosis. Based on preliminary experiments, we will test if NTNG1-NGL1 engagement is needed for the PC cell-executed trogocytosis. The cell-cell contact structures involved in the CAF-PC oncogenic synapses that facilitate trogocytosis have not been previously described. Therefore, their detailed molecular and cell biology characterization is critical. The adaptation of neuronal synapse mechanisms by PC cells bypasses the metabolic restrictions imposed by the PC microenvironment. Thus, the oncogenic synapses may be the key to understanding the direct CAF-PC cell- cell communication which endorses malignant progression.