Neuronal glutamate-mediated pancreatic cancer progression through neuro-cancer synapses

• Applicant: Professor Dr. Ihsan Ekin Demir
• Subject Area: General and Visceral Surgery
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 520728947

Neural invasion (NI) is one of the strongest prognostic factors in human pancreatic cancer (PCa). During NI, PCa cells adhere to intrapancreatic nerves and exploit them as routes of spread. The molecular mechanisams of NI have, however, not yet been fully elucidated. Recent studies have shown that in the central nervous system, glioma cells or metastatic breast cancer cells can form pseudo-tripartite synapses with neuronal synapses to fuel themselves with L-glutamate in a manner similar to that found within an excitatory synapse structure. The presence of such a glutamate-NMDA axis and of pseudo-tripartite synapses outside the nervous system, i.e., in a peripheral cancer like PCa, has not yet been demonstrated. Here, we intend to explore whether a similar glutamatergic neuronal input over the glutamate-NMDAR signaling into the cancer cells fosters their growth and promotes NI in PCa. In our preliminary study, we profiled the glutamate receptor profile of human and murine PCA cell lines on the CCLE database and correlated this pattern to the neuro-or non-neuro-invasive PCA cell lines. We found that the glutamate receptor subtype GluN2D (encoded by GRIN2D) was explicitly involved in cell migration and invasion of the neuroinvasive pancreatic cancer cells mediated by L-Glutamate or DRG (dorsal root ganglion) conditioned medium (CM). These phenotypic features could be completely reversed after GluN2D antagonist and GRIN2D siRNA treatment, however, not in non-neuroinvasive pancreatic cancer cells. The transduction molecules of Glutamate-GluN2D-NMDAR signaling were activated and up-regulated by co-culture with DRG or DRG CM. In co-cultures of neurons and PCa cancer cells, GRIN2D, GRIN1, and the NMDAR-interaction partners PSD95 were upregulated in neuro-invasive PCa cells exposed to neurons, whereas synaptobrevin-1 and vGlut-2 were notably present on axons that extended from neurons and synapsed on PCa cells. This finding was not observed in non-neuroinvasive PCa cells. Mechanistically, glutamate or DRG CM treatment led to the enrichment of the transcription factor EZH2 on the Grin2d promotor through the EZH2-E2F1-Rb pathway. We conclude that neurons promote the migration of PCA towards neurons in a glutamate-fueled manner via GluN2D mediated Glutamate-NMDAR signaling, which is regulated by the upstream EZH2-E2F1-RB pathway. This molecular machinery between synapse-triggered PCA migration represents a novel targetable pathway, which we want to explore further within the herein proposed in vivo targeting approaches. Furthermore, we will assess the electrical activity in DRG neurons that interact with PCa cells over the glutamate-GluN2D signalling and will detect the putative neuro-cancer synapses via electron microscopy in human PCa in situ. Collectively, the proposed study will advance our understanding of neuron-cancer interactions and provide potential actionable targets against NI in PCa.

• DFG Programme: Research Grants