P40: Exosomal isolation of immune checkpoints from pancreatic ductal adenocarcinoma patient-derived organoids

Friday, March 24, 2023

5:16 PM – 5:21 PM

Location: SSO HUB Pan-Tumor Zone: CRS, HPB, Pan-Tumor & Upper GI

Poster Presenter(s)

Hannah McDonald, MD

Research Resident
Department of Surgery, University of Kentucky College of Medicine
Lexington, Kentucky, United States

Disclosure information not submitted.

Author(s)

Hannah McDonald, MD

Research Resident
Department of Surgery, University of Kentucky College of Medicine
Lexington, Kentucky, United States

Disclosure information not submitted.
MG

Mei Gao, PhD

Staff Scientist
Department of Surgery, The University of Kentucky College of Medicine, United States

Disclosure information not submitted.
MB

Mautin Barry-Hundeyin, MD

Surgical Oncologist
Department of Surgery, The University of Kentucky College of Medicine, United States

Disclosure information not submitted.
TF

Teresa Fan, PhD

Principal Investigator
University of Kentucky, Department of Toxicology and Cancer Biology, United States

Disclosure information not submitted.
JK

Joseph Kim, MD

Chief of Surgical Oncology
Department of Surgery, The University of Kentucky College of Medicine, United States

Disclosure information not submitted.

Introduction: Exosomes are extracellular vesicles produced by tumor cells which promote cancer growth, metastasis, and immune evasion. Our previous studies have shown that innate immune checkpoint PD1 signaling activated oncogenic MET pathways in pancreatic ductal adenocarcinoma (PDAC) cell lines. This work was the foundation for our ongoing phase II investigator initiated trial treating metastatic PDAC patients with anti-MET (cabozantinib) and anti-PD1 (pembrolizumab) therapy with concurrent drug sensitivity testing in patient-derived organoids (PDOs). We sought to isolate and quantify peritumoral exosomal PD1/PDL1, MET, and related pathway proteins using patient-derived organoids.

Methods: Patient-derived organoids (PDOs) were created from PDAC tumor samples originating from two different clinical trial patients (hPT27 and hPT50), passaged to confluence, and utilized for exosome isolation. Exosome isolation from media was performed using precipitation, followed by size-exclusion chromatography. Reverse-phase protein array (RPPA), a high-throughput state of the art proteomics platform, was used to characterize the exo-PDL1 and associated pathway proteins. Immunohistochemistry (IHC) was performed on hPT27 PDO showing both MET and PD-1 expression. In vitro cell viability assays were performed after 48 hr treatment with pembrolizumab (PEM) and cabozantinib (CABO).

Results: PDOs were successfully created from two patient samples using previously validated methods, passaged to confluence for media exosome isolation and drug testing. RPPA of exosomes isolated from the two PDO lines revealed variable levels of exosomal protein between PDO lines. Exo–PDL1 was identified in exosomes from both PDO lines. Analysis of the two PDO lines showed expression of exosomal tumor promoting proteins including PD1, MET, PDL1, CXCR4, EPCAM, and HER2 (Figure 1A). IHC of PDOs showed both PD-1 and MET expression (1B). In vitro cell viability assays for this patient (hPT27), CABO alone had the greatest effect (1C).

Conclusions: This is the first known report of isolation of exosomes from PDOs and detection of peritumoral exo-PDL1 expression. Exo-PDL1 is required for potent immune suppression, so our results suggest a PD1/MET pathway in PDAC cells that may regulate this mechanism. Further studies are needed to explore therapeutic opportunities, some of which will ultimately be assessed in the ongoing investigator initiated trial.

Learning Objectives:

Upon completion, participant will understand that checkpoints mediate PDAC growth.
Upon completion, participant will understand that exosomal PDL1 is a target of interest in PDAC.
Upon completion, participant will be able to discuss the merit of investigator initiated trials in surgical oncology.