Abstract C012: TIGIT expression correlates to worse overall survival in primary and metastatic pancreatic ductal adenocarcinoma

Abstract

Abstract Pancreatic Cancer has a 12% 5-year survival rate due to late-stage detection and lack of many chemotherapy or targeted therapy options. TIGIT is an immune checkpoint inhibitor being explored in clinical trials in pancreatic cancer due to the implications of its ligand (CD155) promoting immune evasion. TIGIT is a marker of T cell exhaustion and plays a key role in the inhibition of anti-tumor immune responses. We hypothesize that targeted anti-TIGIT therapy, in conjunction with other therapies targeting the tumor microenvironment, could reverse immune suppression that is characteristic of pancreatic ductal adenocarcinoma (PDAC). As such, here we aim to quantify TIGIT expression using automated RNAscope technology and to correlate it with overall patient survival. We performed RNAscope in situ hybridization and immunohistochemistry on 25 primary and 4 metastatic (liver) formalin-fixed paraffin-embedded (FFPE) tissue sections from patients with histologically confirmed PDAC. A nuclear counterstain combined with an RNAscope probe specific for the human TIGIT mRNA was utilized. Slides were scanned at 40X magnification with an automated slide scanner and quantified using the ISH-IHC module of the HALO-v3.5 software. After cells were segmented based on nuclear recognition, the presence of TIGIT probe within the cytoplasm of each cell was determined and quantified. Percent positive cell values were then exported for statistical analysis in SPSS. De-identified clinical metadata was obtained from REDCap, a cloud-based HIPAA-compliant database used to compile patient data for research purposes. Gender, survival months, ethnicity, race, tumor histology, stage, cancer history, treatment status, and comorbidities were evaluated. We analyzed a cohort of 29 histologically-confirmed surgically resected PDACs, comprised of 25 primary pancreatic tumor samples and 4 metastatic liver core biopsies. The mean percentage of TIGIT positive cells was 63%. From this, the TIGIT high versus low threshold was determined to be 70%. High TIGIT was associated with significantly lower overall survival (p=.013), suggesting that expression of TIGIT and T cell exhaustion may predict overall worse survival. The median overall survival months for the TIGIT low group was 321 months versus 106 months for the TIGIT high group. This data leads us to hypothesize that expression of TIGIT and T cell exhaustion may predict worse overall survival. Anti-TIGIT medications are currently in clinical trials for metastatic PDAC. Here we demonstrate that high TIGIT expression is associated with an overall worse prognosis and present a novel, automated TIGIT detection protocol that may be used to determine if patients are candidates for anti-TIGIT therapy. In a clinical setting, this novel, automated biomarker TIGIT detection protocol could be used to select candidates for anti-TIGIT therapy. This may lead to improved overall patient survival. Citation Format: Madison George, Julie Clark, Kendyll Gartrelle, Georges Nassif, Donald Rempinski, Daniel Long, Hui-Ju Wen, Simone Benitz, Samuel Zwernik, Rupen Shah, Hakmin Park, David Kwon, Philip Philip, Gazala Khan, Howard Crawford, Brian Theisen, Nina Steele. TIGIT expression correlates to worse overall survival in primary and metastatic pancreatic ductal adenocarcinoma [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Pancreatic Cancer; 2023 Sep 27-30; Boston, Massachusetts. Philadelphia (PA): AACR; Cancer Res 2024;84(2 Suppl):Abstract nr C012.