Saturday, April 5, 2025
4/5/2025
Targeting anoctamin 6 to disrupt trogocytosis of cancer-associated fibroblasts - Project Summary The fibroblastic stroma comprises most of pancreatic adenocarcinoma mass and is remarkably devoid of functional blood vessels. It has been assumed that the pancreatic cancer cells obtain their essential metabolites, such as lipids, directly from the interstitial fluid, but we have found that this is not the case. Instead, we present evidence from our intravital fluorescent LDL particles tracing experiments that PDAC tumor cells derive their lipids directly from cancer-associated fibroblasts (CAFs). We have discovered that CAFs feed tumor cells lipids via direct transfer of membranes in a process called trogocytosis (trogo = ‘to gnaw’ or ‘nibble’). We have also found that anoctamin 6 (ANO6) is a unique phospholipid scramblase expressed in CAFs in both human and murine PDAC which is critical for trogocytosis and for cancer cell survival. Trogocytosis is executed when cancer cells and CAFs form synapse-like plasma membranes contacts (Oncosynapses). Within the Oncosynapse, PDAC cells induce cytosolic calcium influx via Orai channels (Greek, Orai, gatekeepers) resulting in PtdSer exposure on CAFs. Finally, we have discovered that ANO6 is critical for CAF membrane trogocytosis by cytotoxic T cells (CTLs) and is highly immunosuppressive. Here, we will test our central hypothesis that ANO6 is a safe and effective target in PDAC to disrupt delivery of exogenous lipids to cancer cells and reverse resistance to immunotherapy in three Aims: Aim 1. How ANO6 activity is regulated in CAF-cancer cell oncosynapse? We will focus on delineating the signaling mechanism by which cancer cells induce influx of calcium via ORAI channels to the CAF cytosol and activate ANO6 lipid scrambling, resulting in PtdSer exposure and trogocytosis. Aim 2. How does blockade of ANO6 prevent CAF trogocytosis and antagonize cancer growth? In this Aim, we will address the mechanism by which ANO6 functions to promote trogocytosis. Sub-aim 2.1 will test how ANO6 structure regulates trogocytosis in CAFs and sensitivity to ANO6 inhibitors. In sub-aim 2.2, we will test blockade of ANO6 in CAFs as a therapeutic strategy to antagonize cancer growth. Aim 3. Does blocking ANO6 enhance anti-PDAC immunity? We will delineate the role of ANO6 in CAFs as a regulator of CTL trogocytosis in CAF-imposed immunosuppression. Interference with this pathway should increase the efficacy of anti-cancer immunotherapies by blocking cholesterol transfer from CAFs to CTLs. We have assembled a team of experts in cancer biology and lipid metabolism (Astsaturov), calcium signaling (Soboloff), and immunity (Fuchs) to execute these studies. A successful outcome to these studies will define a paradigm of combined targeting of ANO6, and membrane lipids donation to reinvigorate CTLs, suppress growth of PDAC tumors and increase their responses to immunotherapy with groundbreaking ramifications for the treatment of this intractable malignancy.
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