Characterization of undifferentiated carcinomas of the pancreas with and without osteoclast-like giant cells.

Abstract

Undifferentiated carcinoma (UC) is a rare subtype of pancreatic cancer differentiated from UC with osteoclast-like giant cells (UC-OGC) in 2019, impacting interpretation of literature that does not distinguish these subtypes. We sought to identify translationally relevant differences between these two variants and as compared to pancreatic ductal adenocarcinoma (PDAC). We characterized clinical and multiomic differences between UC (n = 32) and UC-OGC (n = 15) using DNA-sequencing (seq), RNA-seq, and multiplex immunofluorescence (mIF) and compared these findings to PDAC. Characteristics at diagnosis were similar between UC and UC-OGC, though UC-OGC was more resectable (p = .009). Across all stages, median overall survival (OS) was shorter for UC than UC-OGC (0.4 vs 10.8 years, respectively; p = .003). This shorter survival was retained after stratification by resection, albeit without statistical significance (1.8 vs 11.9 years, respectively; p = .08). In a subset of patients with available tissue, the genomic landscape was similar between UC (n = 9), UC-OGC (n = 5), and PDAC (n = 159). Bulk RNA-seq was deconvoluted and, along with mIF in UC (n = 13), UC-OGC (n = 5), and PDAC (n = 16), demonstrated statistically significantly increased antigen-presenting cells (APCs), including M2 macrophages and NK cells, and decreased cytotoxic and regulatory T cells (Tregs) in UC and UC-OGC vs PDAC. Findings were similar between UC and UC-OGC except decreased Tregs in UC-OGC (p = .04). In this series, UC is more aggressive than UC-OGC with these variants having more APCs and fewer Tregs than PDAC, suggesting potential for immune-modulating therapies in treatment of these pancreatic cancer subtypes.