Abstract 3504: Evaluating the molecular determinants of PDAC racial health disparities
Authors: Johansen-Sallee Anthony E. , Barber Alexa M. , Law Henry , Trevino Jose , Woods Nicholas T. 
Published: April 2023

Abstract
Pancreatic cancer is the 3rd leading cause of cancer-related deaths with a 5-year survival rate of just 11.5%. Pancreatic ductal adenocarcinoma (PDAC), accounting for over 90% of pancreatic malignancies, has the highest incidence rate, mortality rate, and shortest survival times in non-Hispanic black (defined here as African and/or African American ancestry) patients compared to other races. Due to the racial health disparities of PDAC, this study seeks to quantify the proteomic signatures associated with tumor racial origin to identify the underlying molecular pathways that could contribute to these disparities. Using mass spectrometry on primary PDAC tumor samples collected from 30 Caucasian and 12 African American patients, 183 proteins were differentially expressed between these groups. The most over-expressed protein in African American tumors was Ring Finger Protein 2 (RNF2) with a log2 fold-change greater than six. RNF2 had previously been found to regulate GATA Binding Protein 6 (GATA6) in embryonic stem cells. Additionally, GATA6 is also an important determinant in PDAC subtyping with higher GATA6 expression leading to greater chemosensitivity. To expand upon these findings, chromatin immunoprecipitation and sequencing (ChIP-seq) was performed on MIA-PaCa2 to identify binding sites for RNF2 in PDAC cells. Peaks were called with MACS2 (q &lt;0.01) and a final peak list with an irreproducible discovery rate (IDR) of less than 0.05 across two replicates was generated. From the 1,142 replicated peaks identified, RNF2 peaks were localized over the transcription start site of 644 unique transcripts, including GATA6. Modulating RNF2 levels by exogenous expression or short hairpin RNA (shRNA) knockdown confirms that GATA6 is a target of RNF2 repression in PDAC. To further identify its downstream targets in PDAC, RNF2 knock down in MIA-PaCa2 was analyzed by RNA-seq. Differential gene expression analysis revealed RNF2 knockdown decreased expression of genes related to innate immunity, which we have previously identified as a marker of the aggressive Inflammatory PDAC subtype using proteomics. Of the 4,763 differentially expressed genes (P-adj &lt; 0.05), 226 had RNF2 binding sites, demonstrating the scope of RNF2 regulation in MIA-PaCa2. Our work identifies differences in the underlying proteome of PDAC tumors as a function of racial origin, with overexpression of RNF2 in African American tumors potentially contributing to inflammation and subtype delineation. Because PDAC subtypes are predictive of therapeutic response, additional research is necessary to determine whether targeting RNF2 can mitigate oncogenic phenotypes that contribute to racial health disparities.
Citation Format: Anthony E. Johansen-Sallee, Alexa M. Barber, Henry Law, Jose Trevino, Nicholas T. Woods. Evaluating the molecular determinants of PDAC racial health disparities [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3504.