195P Ferroptosis signatures in pancreatic ductal adenocarcinomas and their role in patient survival: A translational unsupervised clustering analysis

Ferroptosis is a type of programmed cell death dependent on iron metabolism distinct from necrosis and apoptosis. In pancreatic ductal adenocarcinomas (PDAC), studies have noted that ferroptosis signatures are also associated with survival. However, no studies have attempted to find histological correlates which might suggest a ferroptosis process occurring. PDACs from the Cancer Genome Atlas (TCGA) Pan-Cancer were used. Clinicopathological, DNA, histological slides, and mRNA expression data were extracted with the GDC Data Transfer Tool. A scree plot was generated to determine the optimal number of clustering groups based on ferroptosis molecular signatures. A K-means clustering approach was used in STATA. Groups of less than 5 patients were excluded. The ferroptosis-based clusters were correlated to clinical, histological, molecular, and survival parameters. Gene Set Enrichment Analysis (GSEA) was also performed by identified cluster. An adjusted α = 0.05 for statistical significance was used for all tests. 175 PDAC cases were used from the TCGA. Optimal K-means clustering identified 4 distinct ferroptosis signature-based PDAC groups, which differed in gene expression. Group 1 (n=47) showed improved overall survival by log-rank analysis versus other 3 groups (p<0.05). There was no significant difference in age, sex distribution, tumor grade, necrosis or staging between Group 1 and other groups. Over-expressed genes in ferroptosis-based group 1 include MAP3K14, TNFAIP3, CYGb; underexpressed genes in Group 1 include EMC2, ZFAS1, CYP4F8. GSEA showed downregulation of EET, DHET and HETE synthesis, and upregulation of RNA metabolism, cell cycle and mitotic activity in Group 1 vs other 3 groups. A comprehensive multimodal approach to ferroptosis expression signatures highlights a clinical impact on overall survival. However, after post-hoc analysis by two pathologists, no histological marker was identified to be significantly associated with ferroptosis signatures. Genes involved in group 1 modulate nF-κB signaling, target lipid peroxidation, and inhibit GPX4 function. Further ancillary testing of ferroptosis pathway in PDACs is warranted.