Elucidating the functional role of Camk2b loss in pancreatic cancer metastasis

Abstract public domain (NIH RePORTER)

PROJECT SUMMARY Pancreatic cancer is highly metastatic, and patients are often not diagnosed until metastases have already formed, with the vast majority (>75%) presenting with oligometastatic disease. Current genetically engineered mouse models of pancreatic cancer are metastatic in 30-40% of animals and harbor only small focal metastases, complicating the study of metastatic drivers in mice. Preliminary experiments identified Calcium/calmodulin- dependent protein kinase II beta, Camk2b, as a gene whose loss enhances tumor metastasis and creates a highly immunosuppressive tumor microenvironment (TME). Genetically engineered mice with tumor cell-specific Camk2b knockout form metastases in 80% of animals and present with >25 metastatic lesions per mouse. Metastatic burden is so profound in this model that the animals succumb to disease twice as fast as control tumor bearing mice. Preliminary results, show that deletion of Camk2b results in tumors that are more metastatic and express higher levels of Lysyl Oxidase (Lox). Aim 1 will focus on exploring tumor cell intrinsic mechanisms through which Camk2b-deletion promotes tumor cell metastasis. The metastatic cascade typically begins by the modulation of tumor cell epithelial identity through programs such as epithelial-to-mesenchymal (EMT). Thus, Subaim 1.1 will investigate the effect of Camk2b loss on tumor cell epithelial cell identity using isogenic cell lines, genetically engineered mouse model, and patient-derived organoid systems. Subaim 1.2 will investigate the functional contribution of LOX on metastatic competency and the ability of LOX-targeting to block metastatic outgrowth. Preliminary experiments indicate that deletion of Camk2b in tumor cells shifts the immune milieu towards a pro- tumor state that is more permissive to tumor metastasis. In this regard, Camk2b-null tumor cells alter their local microenvironment and confer an immune desert phenotype that may facilitate tumor growth and metastasis. To explore mechanisms of this immunosuppressive phenotype, Aim 2 will test the contribution of the immunosuppressive microenvironment in Camk2b-null tumors on metastasis. Subaim 2.1 will selectively deplete macrophages in Camk2b-deletion tumors and evaluate the impact on the metastatic niche and gross tumor cell metastasis. Subaim 2.2 will investigate the contribution of Tbc1d9, a calcium-responsive gene activated in Camk2b deleted tumor cells, to suppression of the NK and T cell response. Collectively, our work will demonstrate that Camk2b is a metastasis suppressing gene whose loss activates pro- metastatic signaling networks. Our functional and mechanistic work will define targetable downstream signaling nodes, within tumor cells and in the microenvironment, to block immunosuppression and metastatic outgrowth.

Public health relevance public domain (NIH RePORTER)

PROJECT NARRATIVE Current pancreatic cancer mouse models do not fully recapitulate the highly metastatic nature of patient disease. This proposal leverages new highly metastatic genetically engineered mouse models of pancreatic cancer to understand both tumor cell intrinsic and non-cell autonomous mechanisms that promote metastasis. Metastasis is the leading cause of cancer related deaths, thus having a model that more accurately depicts this and research into the molecular mechanisms of metastasis will unlock novel pathways to target metastatic pancreatic cancer.