The prognostic significance of prolyl 4-hydroxylase subunit alpha 1 and the therapeutic efficacy of diethyl-pythiDC, its small molecule inhibitor, in pancreatic ductal adenocarcinoma

Abstract Background: Prolyl 4-hydroxylase subunit alpha 1 (P4HA1) has an oncogenic role in pancreatic ductal adenocarcinoma (PDAC). Since high expression of P4HA1 in PDAC is suggested to correlate with poor prognosis, targeting P4HA1 could have therapeutic benefits. Herein, we assessed the prognostic significance of P4HA1 expression at the RNA and protein levels in PDAC using publicly available data. We also evaluated the efficacy of diethyl-pythiDC, a small molecule inhibitor of P4HA1, in PDAC cells. Methods: UALCAN (ualcan.path.uab.edu), a comprehensive proteogenomic cancer data analysis portal, was used to obtain gene expression P4HA1 as transcripts per million reads (TPM) (PDAC n=178) from The Cancer Genome Atlas (TCGA); levels of P4HA1 protein expression data were obtained from (normal pancreas, n=74, PDAC n=137) the Clinical Proteomic Tumor Analysis consortium (CPTAC). Immunohistochemical analysis obtained from Human Protein Atlas (HPA) confirmed increased P4HA1 protein expression. Overall survival (OS) between patients with high and low/medium TPM (TPM values above and below upper quartile, respectively) and high and low protein expression score (based on staining intensity and fraction of stained cells) was calculated using the log-rank Wilcoxon test. To determine the efficacy of diethyl-pythiDC in PDAC cells (PANC-1 and BxPC-3), we performed clonogenic assay for colony formation, MTT assay for cell proliferation, flow cytometry for cell cycle analysis, and western blotting for markers of the epithelial-mesenchymal transition (EMT). Results: In the TCGA data, high P4HA1 expression (TPMs) was associated with a poor prognosis (high expression vs. low/medium expression, log-rank p=0.009). Analysis of HPA data showed that the 5-year OS of patients with high P4HA1 expression was 12% vs. 58% for patients with low P4HA1 (log-rank p<0.001). CPTAC data showed higher P4HA1 protein expression in patients with receptor tyrosine kinase (RTK) pathway (p<0.001), mammalian target of rapamycin (mTOR) pathway (p=0.045) and SWItch/Sucrose Non-Fermentable (SWI-SNF) complex (p=0.022) alterations. Diethyl-pythiDC treatment of PDAC cells reduced proliferation, decreased colony formation, and increased G2/M cell cycle arrest. In addition, diethyl-pythiDC increased protein expression of E-cadherin, an epithelial marker, and decreased the expression of N-cadherin and vimentin, the mesenchymal protein markers. Conclusions: Patients with high P4HA1 expression had poor OS. CPTAC data showed higher P4HA1 protein expression in patients with RTK, mTOR and SWI-SNF alterations. Targeting P4HA1 with diethyl-pythiDC reduced proliferation by arresting cells in G2/M phase of the cell cycle and modulated EMT markers. Thus, targeting of P4HA1 can be a viable strategy and may be considered in future PDAC clinical trials. Citation Format: Moh'd Khushman, Farrukh Afaq, Prachi Bajpai, Sameer Al Diffalha, Darryl Outlaw, Grant R. Williams, Rojymon Jacob, Kondal Rao Kyanam Kabir, Ali Ahmed, Peter Shajan, Sooryanarayana Varambally, Upender Manne. The prognostic significance of prolyl 4-hydroxylase subunit alpha 1 and the therapeutic efficacy of diethyl-pythiDC, its small molecule inhibitor, in pancreatic ductal adenocarcinoma [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 1003.