Gemcitabine Modulates HLA-I Regulation to Improve Tumor Antigen Presentation by Pancreatic Cancer Cells

Pancreatic cancer is a lethal disease, harboring a five-year overall survival rate of only 13%. Current treatment approaches thus require modulation, with attention shifting towards liberating the stalled efficacy of immunotherapies. Select chemotherapy drugs which possess inherent immune-modifying behaviors could revitalize immune activity against pancreatic tumors and potentiate immunotherapeutic success. In this study, we characterized the influence of gemcitabine, a chemotherapy drug approved for the treatment of pancreatic cancer, on tumor antigen presentation by human leukocyte antigen class I (HLA-I). Gemcitabine increased pancreatic cancer cells' HLA-I mRNA transcripts, total protein, surface expression, and surface stability. Temperature-dependent assay results indicated that the increased HLA-I stability may be due to reduced binding of low affinity peptides. Mass spectrometry analysis confirmed changes in the HLA-I-presented peptide pool post-treatment, and computational predictions suggested improved affinity and immunogenicity of peptides displayed solely by gemcitabine-treated cells. Most of the gemcitabine-exclusive peptides were derived from unique source proteins, with a notable overrepresentation of translation-related proteins. Gemcitabine also increased expression of select immunoproteasome subunits, providing a plausible mechanism for its modulation of the HLA-I-bound peptidome. Our work supports continued investigation of immunotherapies, including peptide-based vaccines, to be used with gemcitabine as new combination treatment modalities for pancreatic cancer.

The histone deacetylase inhibitor M344 as a multifaceted therapy for pancreatic cancer

The histone deacetylase (HDAC) inhibitor vorinostat, used with gemcitabine and other therapies, has been effective in treatment of experimental models of pancreatic cancer. In this study, we demonstrated that M344, an HDAC inhibitor, is efficacious against pancreatic cancer in vitro and in vivo, alone or with gemcitabine. By 24 hours post-treatment, M344 augments the population of pancreatic cancer cells in G1, and at a later time point (48 hours) it increases apoptosis. M344 inhibits histone H3 deacetylation and slows pancreatic cancer cell proliferation better than vorinostat, and it does not decrease the viability of a non-malignant cell line more than vorinostat. M344 also elevates pancreatic cancer cell major histocompatibility complex (MHC) class I molecule expression, potentially increasing the susceptibility of pancreatic cancer cells to T cell lysis. Taken together, our findings support further investigation of M344 as a pancreatic cancer treatment.

Major histocompatibility complex class I molecule expression by pancreatic cancer cells is regulated by activation and inhibition of the epidermal growth factor receptor

Pancreatic cancer is one of the deadliest neoplasms, with a dismal 5-year survival rate of only 10%. The ability of pancreatic cancer cells to evade the immune system hinders an anti-tumor response and contributes to the poor survival rate. Downregulation of major histocompatibility complex (MHC) class I cell-surface expression can aid in immune evasion by preventing endogenous tumor antigens from being presented to cytotoxic T cells. Earlier studies suggested that epidermal growth factor receptor (EGFR) signaling can decrease MHC class I expression on certain cancer cell types. However, even though erlotinib (a tyrosine kinase inhibitor that targets EGFR) is an approved drug for advanced pancreatic cancer treatment, the impact of EGFR inhibition or stimulation on pancreatic cancer cell MHC class I surface expression has not previously been analyzed. In this current study, we discovered that EGFR affects MHC class I mRNA and protein expression by human pancreatic cancer cell lines. We demonstrated that cell-surface MHC class I expression is downregulated upon EGFR activation, and the MHC class I level at the surface is elevated following EGFR inhibition. Furthermore, we found that EGFR associates with MHC class I molecules. By defining a role in pancreatic cancer cells for activated EGFR in reducing MHC class I expression and by revealing that EGFR inhibitors can boost MHC class I expression, our work supports further investigation of combined usage of EGFR inhibitors with immunotherapies against pancreatic cancer.

Abstract P028: Effects of histone deacetylase inhibition on major histocompatibility compatibility complex (MHC) class I expression, growth, and migration of cancer cells

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.

Abstract P118: Analysis of macrophage function and histone deacetylase inhibition in neuroblastoma

Background: Neuroblastoma is the third most common childhood cancer and accounts for 12% of cancer-associated deaths in children under the age of 15. Treatment of neuroblastoma with the histone deacetylase inhibitor (HDACi) vorinostat induces increased infiltration of macrophages with upregulated immune cell-surface receptors. Neuroblastoma cells release VEGF and M-CSF, which may alter intratumoral macrophage populations. VEGF has also been implicated in alteration of amyloid precursor protein family processing. Our lab demonstrated that amyloid precursor protein 2 (APLP2), a member of the amyloid precursor protein family, plays an important role in the migration of tumor cells. APLP2 is known to be expressed by macrophages, but no studies have previously examined macrophage functions that are impacted by APLP2 in the context of neuroblastoma disease and its treatment by HDACi drugs. Because of the high morbidity and mortality associated with neuroblastoma, studies such as this one that are designed to comprehend the interaction of immunity and treatment in neuroblastoma are clinically significant. Methods: We treated neuroblastoma tumor cells (Neuro-2a) in vitro with M344, an HDACi with structural similarity to vorinostat, and assessed viability through MTT assay. In addition, we generated mice with APLP2 knockout in cells expressing the Csf-1 receptor (a protein characteristically expressed by macrophages and dendritic cells). Polarization of macrophages isolated from the macrophage-targeted APLP2-knockout mice was achieved through treatment with IFN-γ and LPS (M1) or IL-4 (M2). Macrophages were then analyzed through western blotting and flow cytometry for APLP2 expression and polarization markers. Results: Following polarization, macrophages collected from the bone marrow of macrophage-targeted APLP2-knockout mice have an altered distribution of M1 and M2 sub-populations, which are macrophage sub-populations that differ in their migratory capabilities, as well as in their abilities to stimulate or suppress anti-tumor immunity. Furthermore, we showed that M1 and M2 subpopulations of bone marrow-derived macrophages from normal mice differ in their expression of APLP2. We also demonstrated that M344 decreased neuroblastoma cell growth. Thus, APLP2 is influential in macrophage biology, and we have created a novel mouse model for defining its specific contributions in mice treated with HDACi drugs that influence macrophage biology. Conclusions: We have made progress in understanding the impact of the HDACi drug M344 on neuroblastoma cells and are ready to analyze its impact on macrophage/dendritic cell populations in a syngeneic neuroblastoma mouse model, as well as to define the role of APLP2 in the function of these cell populations in the context of neuroblastoma. In addition to their potential contribution to the development of new neuroblastoma therapies, the results from this study are expected to expand our comprehension of macrophage function and regulation, and thus will be of broad value in the immunology and oncology fields.

Citation Format: Gabrielle L. Brumfield, Shelby M. Knoche, Alaina C. Larson, Brittany J. Poelaert, Benjamin T. Goetz, Poomy Pandey, Donald W. Coulter, Joyce C. Solheim. Analysis of macrophage function and histone deacetylase inhibition in neuroblastoma [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2021 Oct 7-10. Philadelphia (PA): AACR; Mol Cancer Ther 2021;20(12 Suppl):Abstract nr P118.