Abstract P028: Effects of histone deacetylase inhibition on major histocompatibility compatibility complex (MHC) class I expression, growth, and migration of cancer cells
Authors: Knoche Shelby M. , Brumfield Gabrielle L. , Goetz Benjamin T. , Sliker Bailee H. , Barbosa Cecilia , Romanova Svetlana , Bronich Tatiana , Coulter Donald W. , Solheim Joyce C. 
Published: January 2022

Abstract
Background: Cancer is a devastating scourge, causing morbidity and mortality in both adult and pediatric populations. In this study, we analyzed the effects of histone deacetylase (HDAC) inhibitors on the MHC class I expression, growth, and migration of cancer cells. Within cancer cells, MHC class I molecules bind to fragments of tumor-associated peptides, and then migrate to the cell surface to present the peptides to T lymphocytes and induce lysis of the tumor cells, thereby preventing further spread of the malignancy. Pancreatic cancer, a disease afflicting older adults, is now the third most common cause of cancer-related death overall in the U.S. Neuroblastoma is the third most common childhood cancer and results in 12% of cancer-associated deaths in children less than 15 years of age. In both of these cancers, HDAC expression has been shown to be dysregulated and abnormally high. Although several HDAC inhibitors have been extensively investigated in preclinical studies and have entered clinical trials, the two HDAC inhibitors that we are evaluating in our research (M344 and RGFP966) have been the focus of only a few prior studies, and much remains to be discovered about their therapeutic effects. Methods: We treated cancer cell lines with HDAC inhibitors over a range of concentrations for multiple timepoints. Our investigations included analysis of MHC class I expression by immunoblotting for total subunit protein levels and flow cytometric monitoring of MHC class I levels at the cell surface, immunoblotting for the co-inhibitory protein PD-L1, transwell assays for migration, and MTT assays for cell growth. New collaborative studies have been initiated to develop two varieties of nanoformulations for optimization of the delivery of these HDAC inhibitors to tumors. Results: Our flow cytometry analysis demonstrated that the expression of the cell-surface human MHC class I molecules detected by antibodies recognizing HLA-A and both HLA-B and –C was elevated on S2-013 cells following M344 treatment. Increased total MHC class I heavy chain protein expression was induced in S2-013 cells by both M344 and RGFP966, and RGFP966 also increased PD-L1 expression. In addition, M344 and RGFP966 reduced S2-013 pancreatic cancer cell growth, and M344 slowed S2-013 migration and Neuro2a neuroblastoma cell growth. Analysis of M344 efficacy in an S2-013 orthotopic xenograft mouse model showed significant reduction of the tumor growth rate. Novel nanoparticles have been generated for M344 delivery using block copolymer and hyaluronic acid formulation strategies. Conclusions: Our evidence indicates that the HDAC inhibitors M344 and RGFP966 have anti-tumor potential via boosting MHC class I molecule expression to improve T cell recognition, as well as by tumor-intrinsic effects (i.e., down-regulation of proliferation and migration). Thus, both of these HDAC inhibitors warrant further analysis in adult and pediatric tumor mouse models, and may have potential for future clinical testing in patients.
Citation Format: Shelby M. Knoche, Gabrielle L. Brumfield, Benjamin T. Goetz, Bailee H. Sliker, Cecilia Barbosa, Svetlana Romanova, Tatiana Bronich, Donald W. Coulter, Joyce C. Solheim. Effects of histone deacetylase inhibition on major histocompatibility compatibility complex (MHC) class I expression, growth, and migration of cancer cells [abstract]. In: Abstracts: AACR Virtual Special Conference: Tumor Immunology and Immunotherapy; 2021 Oct 5-6. Philadelphia (PA): AACR; Cancer Immunol Res 2022;10(1 Suppl):Abstract nr P028.