Abstract B054: Histone lysine methyltransferase NSD3 governs transcriptional programs that drive pancreatic neuroendocrine tumors
Authors: Fuentes Mary E. , Hausmann Simone C. , Flores Natasha M. , Lu Xiaoyin , Mazur Pawel K. 
Published: November 2022

Abstract
Pancreatic Neuroendocrine Tumors (PanNETs) are the most common and lethal neuroendocrine malignancies. For decades, standard chemotherapeutic regimens and targeted therapeutics have been used in advanced patients with little to no avail. Thus, there is a critical unmet need to develop novel and effective precision therapeutics. Additionally, pre-clinical models that faithfully recapitulate disease are urgently needed for translational studies. Here, we directly address these challenges by characterizing a novel genetically engineered mouse model of PanNETs as well as identifying histone lysine methyltransferase (KMT) NSD3 as a critical oncogenic driver. We identified KMT NSD3 to be upregulated through a meta-analysis of human PanNET RNA-Seq data. Previous literature indicates that NSD3 canonically di-methylates Histone H3 lysine residue 36 (H3K36me2) selecting transcriptional and gene expression programs with potential cancer implications. Thus, we sought to identify the role of NSD3 and H3K36 di-methylation dynamics in PanNET tumorigenesis. Our initial findings indicate that loss of NSD3 decreases proliferation and di-methylation of H3K36 in vitro using PanNET PDX cell lines. Additionally, we generated a novel in vivo model focusing on the pancreatic islet-specific loss of conditional Men1Lox/Lox, AtrxLox/Lox, and PtenLox/Lox alleles, alterations of which are representative of human disease. Proof-of-concept studies were done comparing time-matched wild-type and our PanNET model, revealing that our model has increased islet hyperplasia and proliferation. Additionally, to analyze the role of NSD3 in vivo, we generated a conditional Nsd3Lox/Lox knockout mouse which I have crossed to our PanNET model. Preliminary studies suggest that Nsd3 depletion significantly attenuates tumor growth in vivo. Furthermore, our lab conducted in vitro methylation assays that identified a gain-of-function point mutation NSD3T1232A that increases the catalytic activity of NSD3 at H3K36me2. Thus, to understand the role of the enzymatic activity of NSD3 in PanNET tumorigenesis, we conducted studies in vitro where we reconstituted NSD3 wild-type, NSD3Y1174A enzymatically deficient, and NSD3T1232A in NSD3 depleted cells. Preliminary findings indicate that NSD3T1232A increases H3K36me2 and significantly increases proliferation, while NSD3WT rescues H3K36me2 and proliferation, and NSD3Y1174A does not rescue H3K36me2 and the phenotype observed. Lastly, to leverage NSD3 hyperactivity in vivo, we generated an NSD3T1232A mouse (Rosa26LSL-NSD3T1232A) and crossed with our initial PanNET model. Our results demonstrate that NSD3T1232A significantly decreases survival, accelerates tumor burden, and proliferation when compared to time-matched control and NSD3 deficient mice. Together, these studies provide insights into the role of NSD3 in PanNET tumorigenesis. Future portions of testing will establish the specific cellular and molecular modes of action of NSD3 and establish a potential therapeutic target.
Citation Format: Mary E. Fuentes, Simone C. Hausmann, Natasha M. Flores, Xiaoyin Lu, Pawel K. Mazur. Histone lysine methyltransferase NSD3 governs transcriptional programs that drive pancreatic neuroendocrine tumors [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer; 2022 Sep 13-16; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2022;82(22 Suppl):Abstract nr B054.