PD-L1 and Notch as novel biomarkers in Pancreatic Sarcomatoid Carcinoma: a pilot study

Background: The improved immunological understanding revealed the tumor microenvironment as an appealing driver to restore the immune response against cancer cells resulting in a paradigm shift in the oncology field. However, the complexity of the tumor milieu suggests a role of several pathways linking in immunomodulation mechanisms. Pancreatic cancer represents a model of the intricate relationship between malignant cells and their surrounding neighborhood. Research design and methods: In this study we analyzed, retrospectively, 6 cases of rare pancreatic sarcomatoid carcinoma (PSC) and evaluated the expression of PD-L1 and Notch, aiming to explore new attributes in immunophenotype. Results: PD-L1 CPS≥1% was common in PSCs (83%) with half samples expressing PD-L1 CPS≥50%. Notch1 and Notch3 expression resulted positive demonstrating a high IRS range of expression. A direct significant correlation between PD-L1 and Nocth3 overexpression (r=0.7; p=0.036) has been observed. Moreover, immunofluorescence studies revealed a co-localization of Notch3 and PD-L1 when both proteins were over-expressed within cytoplasmic or membranous compartments of the same cells. Conclusions: Our data identify a unique biological characterization of this rare pancreatic histotype. These findings provide a rationale for future studies evaluating the potential crosstalk between PD-L1/PD-1 axis and Notch pathways and prompting the development of novel therapeutics strategy.