Abstract 5284: Reduced occludin expression is related to unfavorable tumor phenotype and poor prognosis in many different tumor types: a tissue microarray study on 16,870 tumors

Abstract Occludin is a key component of tight junctions. Reduced occludin expression has been linked to cancer progression. To study the role of occludin in cancer, a tissue microarray containing 16, 870 samples from 148 different tumor types and 608 samples of 76 different normal tissue types was analyzed by immunohistochemistry. Occludin immunostaining was observed in 10, 746 (76.6%) of 14, 017 analyzable tumors, including 18.9% with weak, 16.2% with moderate, and 41.6% with strong staining intensity. Occludin positivity was found in 134 of 148 tumor categories and was most frequent in adenocarcinomas (37.5-100%) and neuroendocrine neoplasms (67.9-100%), less common in squamous cell carcinomas (23.8-93%) and in malignant mesotheliomas (up to 48.1%) and rare in Non-Hodgkin’s lymphomas (1-2%) and most mesenchymal tumors. Reduced occludin staining was associated with advanced pT stage (p<0.0001), L1 status (p=0.0384), and absence of microsatellite instability (p<0.0001) in colorectal adenocarcinoma, advanced pT stage in pancreatic adenocarcinoma (p=0.005), high ISUP grade (p<0.0001), advanced pT stage (p<0.0001), high UICC stage (p<0.0001), distant metastasis (p=0.0422), and shortened overall (p=0.0045) or recurrence-free survival (p=0.0116) in clear cell renal cell carcinoma (RCC), high pT stage (p<0.0001) and UICC stage (p=0.0228), distant metastasis (p=0.0338), and shortened recurrence-free survival (p=0.006) in papillary RCC, and advanced pT stage (p=0.0133) in serous high-grade ovarian cancer. Occludin staining was unrelated to parameters of tumor aggressiveness in breast, gastric, endometrial, and thyroidal cancer. Our data demonstrate significant levels of occludin expression in many different tumor entities and identify reduced occludin expression as a potentially useful prognostic feature in several tumor entities. Citation Format: Seyma Büyücek, Florian Viehweger, Viktor Reiswich, Natalia Gorbokon, Viktoria Chirico, Christian Bernreuther, Florian Lutz, Simon Kind, Ria Schlichter, Sören Weidemann, Till S Clauditz, Andrea Hinsch, Ahmed Abdulwahab Bawahab, Frank Jacobsen, Andreas M Luebke, David Dum, Elena Bady, Lisa Hornsteiner, Claudia Hube-Magg, Martina Kluth, Katharina Möller, Anne Menz, Andreas M Marx, Till Krech, Patrick Lebok, Christoph Fraune, Guido Sauter, Ronald Simon, Eike Burandt, Sarah Minner, Stefan Steurer, Maximilian Lennartz, Morton Freytag. Reduced occludin expression is related to unfavorable tumor phenotype and poor prognosis in many different tumor types: a tissue microarray study on 16, 870 tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 5284.