Abstract 6825: Epigenetic dysregulation in well-differentiated pancreatic neuroendocrine tumor (PNET): An immunohistochemistry (IHC) analysis

Abstract

Abstract Epigenetic dysregulation through DNA Methyltransferase 1 (DNMT1) is integral to pancreatic neuroendocrine tumorigenesis. We aim to investigate the interplay between epigenetic modifiers and pathogenetic markers in the PNET microenvironment. 12 paraffin-embedded PNET specimens and 12 benign adjacent tissue specimens, used as controls, were obtained from Cooper University Hospital Pathology Department (IRB 23-130). IHC was performed using epigenetic markers, including DNMT1, DNMT3A, DNMT3B, and 5-Hydroxymethylcytosine (5-HMC), and pathogenic markers, including Multiple Endocrine Neoplasia 1 (MEN1), Protein-Tyrosine Phosphatase (PTEN), and Ras Association Domain Family 1 (RASSF1). Image J software was utilized for IHC scoring under the guidance of a board-certified pathologist. DNMT1 was upregulated in PNET tumor specimens with a mean density score of 72.02 +/- 31 versus 16.02 +/- 17 in adjacent benign tissue (p<.001). Grade 2 tumors displayed increased DNMT1 expression compared to Grade 1 tumors with a mean score of 37 +/-21 versus 71 +/- 23 (p<.05). Decreased expression of 5-HMC was noted in tumor specimens in comparison to benign tissue with a mean score of 3.92 +/- 5.05 versus 19.37 +/- 5.05 (p<.05). Loss of 5-HMC was observed in higher tumor grades with a mean score of .79 +/- 2 versus 8.2+/-2 (p<.01). DNMT3B was upregulated in PNET tumor specimens with a mean score of 13.16 +/- 3.94 versus 7.02+/- 2.553 (p<.01) in adjacent benign tissue and was positively correlated to DNMT1 expression. DNMT3A was not found to have a difference in expression between tumor and benign tissue. MEN1 was downregulated in PNET, with 45% of tumor specimens displaying loss of MEN1 expression. Mean MEN1 density in tumor tissue was 4.47 +/- 5.95 versus 11.41 +/- 3.53 in adjacent benign (p<.01). Increased expression of DNMT1 found to negatively correlate with MEN1 expression (R2=.23). Loss of RASSF1 expression was present in 70% of tumor specimens with a mean score of 1.32 +/- 1.99 versus 9.50+/- 6.89 (p<.001) in adjacent benign tissue. RASSF1 expression correlated negatively with DNMT1 (R2=.21). PTEN expression showed intratumoral homogeneity to benign tissue, and its expression was not correlated with any epigenetic markers. Our work provides a framework of epigenetic regulators involved in the pathobiology of PNET, and can refine prognostic evaluation while providing therapeutic benefits for patients with PNET. Citation Format: Zena Saleh, Yazid Ghanem, Hansa Joshi, Mathew C. Moccia, Helen Toma, Yahui Li, Upsana Joneja, Tao Gao, Young Hong. Epigenetic dysregulation in well-differentiated pancreatic neuroendocrine tumor (PNET): An immunohistochemistry (IHC) analysis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6825.