cAMP/PKA signaling in cancer-immune interactions in head and neck cancer

• Applicant: Dr. Daniel Stehle
• Subject Area: Cell Biology ; Biochemistry ; Immunology ; Pharmacology
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 546478164

Smoking is the number one risk factor for head and neck cancer and is estimated to account for 70-80% of the cases. Immune checkpoint blockade (ICB) is a promising strategy to treat head and neck cancer, but only about 20% of the patients show a durable response to ICB because of the establishment of immune evasion. Recently, Gαs-PKA signaling was shown to trigger T cell exhaustion and abolish the effect of co-applied ICB. cAMP/PKA signaling is highly spatially compartmentalized – cAMP buffers and degrading enzymes help maintain cAMP microdomains, and A-kinase anchoring proteins (AKAPs) localize to PKA to specific subcellular locations to achieve high signaling specificity. Despite the identification of T cell AKAPs such as Ezrin, it is not well understood how cAMP/PKA signaling is spatially regulated in these critical immune cells. We hypothesize that cAMP/PKA signaling in T cells is locally regulated in the immune synapse microdomain, and that disruption thereof can overcome T cell dysfunction. In this study, we will engineer new far-red and green cAMP and PKA biosensors to facilitate multiplexed real-time imaging of these key Gαs-PKA pathway components in T cells. We will optimize the biosensors for live-tissue imaging by improving their dynamic range and kinetics while minimizing phototoxicity. We and others have shown that microdomains are crucial for regulation of PKA activity. In T cells, Ezrin recruits PKA and its downstream effector Csk to the immune synapse. We will assess if and how these PKA microdomains change during tumor cell engagement with and without treatment with PKA-modulating drugs and ICB. At the same time, we will analyze the temporal coordination of cAMP/PKA signaling in the process of T cell exhaustion. The tumor microenvironment crucially contributes to cancer-related immunosuppression. Thus, we will validate in vitro results in live tumor slices under close-to-native conditions. We will assess how the surrounding tumor microenvironment, e.g., acidosis, influences cAMP/PKA signaling and function of individual T cells. In summary, the proposed study will investigate how cAMP/PKA signaling is spatiotemporally regulated during T cell activation on the subcellular level as well as in the tissue context. This will pave the way for novel therapeutic strategies based on manipulation of cAMP/PKA compartmentation in T cells.

• DFG Programme: WBP Fellowship
• International Connection: USA
• Host: Professorin Jin Zhang, Ph.D.