Project Summary Pancreatic cancer is the fourth-most lethal cancer across both sexes, with five-year overall survival of all stages at 12%. In patients diagnosed with pancreatic cancer, first-line chemotherapy with gemcitabine and nab- paclitaxel with or without FOLFIRINOX often requires second-line chemotherapy combinations, with median survival ranging from 6 to 26 months. New therapeutic combinations are needed. One promising approach for overcoming this impasse centers on senescence. Cells can undergo senescence in response to replication, oncogene induction, or targeted drug therapy, including most chemotherapeutic regimens used for pancreatic cancer. However, while senescent cells have been implicated in tumorigenesis via pro-inflammatory factors seen in circulation as part of the senescence-associated secretory phenotype (SASP), their direct tumoral activity over time and distribution elsewhere is unknown. Moreover, current senescence imaging agents are small molecules measuring lysosome activity. An antibody-based approach, in contrast, offers greater targeting specificity and biological links to surface antigens. Noninvasive PET tools for senescence antigens will improve our ability to identify senescence with the option to change the isotope for targeted alpha therapy in the tumor. The members of the Scott Lowe Lab have pioneered senescence induction in pancreatic cancer with the combination of trametinib (T) and palbociclib (P), leading to the release of cytokines as SASP remodels the tumor microenvironment and beyond. Using immunoPET to study combination TP therapy in their models, we have found that shed antigens such as VEGF and IL-6 are decreased in the tumor environment while membrane- bound antigens like uPAR are elevated. We hypothesize that senescence induced by chemotherapy is temporal and immunoPET can be used noninvasively to quantify these dynamics during therapy. In collaboration with the Scott Lowe and Christine Iacobuzio-Donahue Labs at Memorial Sloan Kettering Cancer Center, we will use noninvasive immunoPET imaging to (1) quantify previously identified senescence markers during senescence- inducing therapy in human and murine pancreatic cancer models, (2) independently discover more senescence- specific markers, and (3) use targeted immunoPET agents for endoradiotherapy and improved senolytic delivery. In collaboration with Patricia Ribeiro Pereira at Washington University at St. Louis, we will also identify pharmacologic methods to prevent antigen shed, while advanced PET reconstruction with Joaquin Lopez- Herraiz at Complutense University Madrid will enable dual radiotracer immunoPET imaging of immune populations during therapy. Our efforts to quantify senescence in vivo with the proposed markers and enhance targeted alpha therapy with senescence will be guided by Dr. Lisa Bodei for clinical relevance and Andrea Schietinger for immunological insight. This work will unlock multiple directions in the precision theranostics of senescence, with great potential for career development and R01 research encompassing numerous cancers.

Project Narrative While numerous chemotherapies give rise to senescence, a type of cell arrest implicated in metastatic disease and therapy resistance, non-invasive methods to image senescence via associated antigens in tumors remain lacking. In this proposal, we will characterize in vitro and in vivo changes in antibody- based PET imaging agents in response to several senescence-inducing therapies in murine as well as human pancreatic cancer models; define pharmacological methods to minimize antigen shed; and identify new antigens in collaboration with the Lowe Lab and independently from available RNAseq databases. Overall, we will demonstrate the enhanced potency of targeted alpha therapy with chemotherapy-induced senescence and apply our newly developed multiplexed PET method for dual imaging of the therapeutic impact in immune populations.