Abstract A032: Elucidating the role of p53 in suppressing pancreatic ductal adenocarcinoma

Abstract

Pancreatic ductal adenocarcinoma (PDAC) is frequently diagnosed at advanced, metastatic stages, emphasizing the need to study the earliest events in disease progression. The tumor suppressor p53 strongly opposes PDAC development and is mutated in nearly 75% of cases, yet how wild-type p53 functions to delay cancer onset remains unclear. To address this question, we are using Kras LSL-G12D/+ ;Rosa26 LSL-tdTomato/LSL-tdTomato ;Ptf1a CreER/+ (KTC) and Kras LSL-G12D/+ ;Trp53 flox/flox ;Rosa26 LSL-tdTomato/LSL-tdTomato ;Ptf1a CreER/+ (KPTC) mice, in which we induce oncogenic changes in adult acinar cells to recapitulate PDAC development and the spectrum of precursor lesions found in humans. Using these models, we seek to understand p53 tumor suppressor function by characterizing changes both in precancerous cells and in the microenvironment during PDAC evolution. Initial analysis of KTC and KPTC mice has revealed that precursor lesions efficiently accumulate irrespective of genotype, but that cancer arises rapidly in KPTC mice. We are carefully characterizing the heterogeneity of premalignant lesions to determine whether p53 influences a specific cell state. By coupling single-cell transcriptomics with immunohistochemistry and hematoxylin and eosin (H&E) staining, we have defined a diverse range of precursors in KTC and KPTC mice that arise after tumor induction. We are assessing how p53 influences the accumulation of these precursors using immunofluorescence. In parallel, we are applying a machine learning model trained on H&E staining to compare the proportions of different lesions between KTC and KPTC pancreata. Notably, we have shown that p53 and its target genes are strongly expressed in a specific subset of precursor lesions. We hypothesize that p53 acts in these cells to suppress lineage plasticity and regulate precursor interactions with the microenvironment. Accordingly, we are developing a cell culture model to characterize pathways of p53 action in precancerous cells. To investigate the microenvironment, we have performed CosMx spatial transcriptomics on 30 tissue cores from KTC and KPTC pancreata collected 10 weeks post-tumor induction. These results, in combination with secretomics experiments, will inform how p53 influences the precursor microenvironment to suppress cancer development. This study will advance our understanding of p53 function during PDAC initiation while informing new biomarkers for early detection and interception.