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 P071: Gemcitabine augments HLA class I expression in pancreatic cancer cells through alterations in transcript production and surface stability

Background: Pancreatic adenocarcinoma, or PDAC, is the fourth leading cause of cancer-related deaths in the United States. Gemcitabine, a nucleoside analog, is a primary standard of care in pancreatic cancer. In addition to its normative cytotoxic function, evidence suggests that this chemotherapy drug also harnesses immunomodulatory capabilities in the form of increasing human leukocyte antigen (HLA) class I expression in lung, breast, colon, and cholangiocarcinoma cells. HLA class I is a complex (alpha heavy chain and beta 2-microglobulin light chain) located at the surface of nearly all cells where it presents peptides, including cancer-associated peptides, to cytotoxic T cells. Recognition of these peptides as atypical leads to T-cell mediated lysis of the presenting cell. Subsequently, understanding the ability of gemcitabine and the mechanisms by which it influences the HLA class I complex are of great importance.

Methods: To investigate the effect of gemcitabine treatment on HLA class I expression in pancreatic cancer, alterations in HLA class I protein levels were monitored via western blot analysis, flow cytometry, and quantitative polymerase chain reaction (qPCR) in three pancreatic cancer cell lines. Changes in surface stability of the HLA class I complex were evaluated through brefeldin A (BFA) assays at the 72-hour time point. For western blot and flow cytometry experiments, impacts on the alpha heavy chain were further assessed for all three types of alpha heavy chains (HLA-A, HLA-B/C) at 72 and 96 hours. In qPCR experiments, alterations were analyzed for the HLA-A, HLA-B, and beta 2-microglobulin transcripts after a 48-hour gemcitabine exposure period.

Results: Administration of gemcitabine to pancreatic cancer cell lines (S2-013, Capan-1, PANC-1) increased total protein levels of both HLA class I constituents (alpha heavy chain and beta-2-microglobulin light chain). All PDAC cell lines evaluated demonstrated enhanced surface expression of HLA-A2 and HLA-B/C with maximal increases of 3 and 2.5-fold respectively, as indicated by flow cytometry. Our qPCR analysis of the Capan-1 and S2-013 cell lines revealed increases in the levels of HLA-A, HLA-B, and beta 2-microglobulin transcripts (3-12-fold). BFA assays suggested that gemcitabine treatment also enhances stability of the surface HLA class I in the S2-013 and PANC-1 cell lines.

Conclusion: In summary, gemcitabine exhibits an immunomodulatory ability to stimulate expression of HLA class I in pancreatic cancer cells. We have demonstrated that this increase in HLA class I is seen at the mRNA, total protein, surface, and stability level. Characterizing the ability of gemcitabine to influence the HLA class I complex and defining the mechanisms by which it does so will increase the potential for identification of suitable immunotherapies, including novel peptide-based cancer vaccines with enhanced treatment efficacy for PDAC patients.

Citation Format: Alaina C. Larson, Shelby M. Knoche, Joyce C. Solheim. Gemcitabine augments HLA class I expression in pancreatic cancer cells through alterations in transcript production and surface stability [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 P071.

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.

Abstract 1658: Gemcitabine impacts expression of antigen presentation proteins by pancreatic cancer cells

Background: Pancreatic adenocarcinoma is one of the deadliest type of cancers with a 5-year overall survival rate of 10%. A standard chemotherapy approach for pancreatic cancer is treatment with gemcitabine. Gemcitabine is also considered a potential immunomodulatory agent, capable of increasing human leukocyte antigen (HLA) class I. HLA class I is a heterodimer of a highly polymorphic alpha heavy chain (HLA-A, -B, or -C) and the light chain beta-2-microglobulin (β2m) that is loaded with an endogenous antigen in the endoplasmic reticulum. The pool of antigens available for HLA class I loading is selected by the transporter associated with antigen processing protein (TAP). However, HLA class I peptide loading can occur independently of TAP, causing the HLA class I molecules to present a different antigen pool to cytotoxic T cells. Because many cancers downregulate HLA class I and prevent intracellular tumor antigens from being presented to cytotoxic T cells, understanding more about gemcitabine's capability to increase HLA class I expression is of great importance.

Methods: Alterations in HLA class I and TAP protein levels were monitored via western blot analysis in a pancreatic cancer cell line (S2-013) in both a time and dose-dependent manner. The time points and dosages which solicited the largest increase in HLA class I expression were also examined by flow cytometry.

Results: Administration of gemcitabine to S2-013 pancreatic cancer cells increased total HLA class I α heavy chain protein, with maximal increases of 141% (HLA-A) and 323% HLA-B/C. Flow cytometry revealed a 3-fold increase in HLA-A2 surface expression post-gemcitabine treatment and a maximal 2-fold increase in HLA-B/C expression at the corresponding gemcitabine concentration, but differing time point. Both western blot and flow cytometry analyses indicate HLA-B/C generally has its largest increase in expression at an earlier time point than HLA-A. In addition, high concentrations of gemcitabine that promoted HLA-A,B,C surface expression were associated with a large decrease in TAP total protein.

Conclusion: In summary, gemcitabine demonstrates an ability to stimulate expression of HLA class I in pancreatic cancer cells, with the rate dependent on the HLA class I allele. Because gemcitabine treatment increases HLA class I surface expression with a simultaneous decrease in TAP expression, our findings indicate that gemcitabine may induce TAP-independent peptide loading of HLA class I. These results suggest the potential for gemcitabine treatment as a priming mechanism to enhance immunotherapy efficacy and potentially alter vaccination strategies in pancreatic cancer.

Citation Format: Alaina C. Larson, Shelby M. Knoche, Joyce C. Solheim. Gemcitabine impacts expression of antigen presentation proteins by pancreatic cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1658.

Abstract 1817: Epidermal growth factor receptor alters major histocompatibility complex class I expression on pancreatic cancer cells

Pancreatic cancer is one of the deadliest neoplasms, with a poor 5-year survival rate of just 10%. The ability of pancreatic cancer cells to evade the immune system hinders an anti-tumor response and contributes to the poor survival rate. In some cases, down regulation of major histocompatibility complex (MHC) class I cell-surface expression aids in immune evasion by preventing endogenous tumor antigens from being presented to cytotoxic T cells. The goal of this study is to evaluate the role epidermal growth factor receptor (EGFR) plays in the regulation of MHC class I expression by pancreatic cancer cells. Pancreatic cancer cell lines were treated with epidermal growth factor (EGF) or transforming growth factor alpha (TGF-alpha) to activate EGFR or with the small molecule drug erlotinib to inhibit EGFR. Immunoprecipitation, western blot analysis, and flow cytometry were used to analyze cells' MHC class I expression post treatment. Human pancreatic cancer cell lines (BxPC-3, T3M4, S2-013, Panc-1) were found to decrease MHC class I expression after EGFR activation by EGF. However, activation of EGFR via TGF-alpha led to differential effects on MHC class I expression in a cell line-dependent manner. EGFR inhibition by erlotinib led to increased MHC class I expression by greater than 2.5-fold on both human and mouse pancreatic cancer cells. Mechanistic studies were done to evaluate the role of src homology 2 phosphatase (SHP2) in EGFR's regulation of MHC class I in pancreatic cancer cells, since in head and neck cancer cells SHP2 can be phosphorylated by activated EGFR and subsequently dephosphorylate STAT1 and reduce MHC class I expression. Following SHP2 knockdown by siRNA transfection, a slight increase in MHC class I expression was observed on pancreatic cancer cells, suggesting SHP2 has a minor down-regulatory role in MHC class I expression in these cells. EGFR was found to co-immunoprecipitate with MHC class I, indicating that EGFR might directly affect MHC class I expression by facilitating its endocytosis. However, after EGFR inhibition, no change in the MHC class I cell surface turnover rate was observed. Other potential mechanisms for EGFR regulation of MHC class I expression are currently being evaluated. Our discoveries defining a role for activated EGFR in reducing MHC class I expression and revealing that EGFR inhibitors can boost MHC class I levels on cancer cells could facilitate the adoption of new, more effective therapeutic tactics that combine the use of EGFR inhibitors with immunotherapies to augment patients' immune systems for effective targeting and killing of cancer cells.

Citation Format: Shelby M. Knoche, Joyce C. Solheim. Epidermal growth factor receptor alters major histocompatibility complex class I expression on pancreatic cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1817.

Amyloid Precursor-like Protein 2 Expression Increases during Pancreatic Cancer Development and Shortens the Survival of a Spontaneous Mouse Model of Pancreatic Cancer

Simple Summary

As pancreatic cancer is a disease with a high fatality rate, a better understanding of how it develops and the identification of new potential targets for its treatment are greatly needed. In this current study, we showed that the expression of amyloid precursor-like protein 2 (APLP2) in pancreatic cancer epithelial cells is higher than in precursor lesion epithelial cells, thus indicating that APLP2 increases during human pancreatic cancer development. We also generated a new mouse model that demonstrated the deletion of APLP2 expression specifically within the pancreas prolongs survival and decreases metastasis for mice with pancreatic cancer. Taken together, these findings open a new avenue toward comprehending and treating pancreatic cancer.

Abstract

In the United States, pancreatic cancer is a major cause of cancer-related deaths. Although substantial efforts have been made to understand pancreatic cancer biology and improve therapeutic efficacy, patients still face a bleak chance of survival. A greater understanding of pancreatic cancer development and the identification of novel treatment targets are desperately needed. Our analysis of gene expression data from patient samples showed an increase in amyloid precursor-like protein 2 (APLP2) expression within primary tumor epithelium relative to pancreatic intraepithelial neoplasia (PanIN) epithelial cells. Augmented expression of APLP2 in primary tumors compared to adjacent stroma was also observed. Genetically engineered mouse models of spontaneous pancreatic ductal adenocarcinoma were used to investigate APLP2′s role in cancer development. We found that APLP2 expression intensifies significantly during pancreatic cancer initiation and progression in the LSL-Kras^G12D/+; LSL-Trp53^R172H/+; Pdx-1-Cre (KPC) mouse model, as shown by immunohistochemistry analysis. In studies utilizing pancreas-specific heterozygous and homozygous knockout of APLP2 in the KPC mouse model background, we observed significantly prolonged survival and reduced metastatic progression of pancreatic cancer. These results demonstrate the importance of APLP2 in pancreatic cancer initiation and metastasis and indicate that APLP2 should be considered a potential therapeutic target for this disease.

Nanoformulation of CCL21 greatly increases its effectiveness as an immunotherapy for neuroblastoma

Neuroblastoma is the most commonly diagnosed extracranial solid tumor in children. The patients with aggressive metastatic disease or refractory/relapsed neuroblastoma currently face a dismally low chance of survival. Thus, there is a great need for more effective therapies for this illness. In previous studies, we, as well as others, showed that the immune cell chemoattractant C-C motif chemokine ligand 21 (CCL21) is effective as an intratumoral therapy able to slow the growth of cancers. In this current study, we developed and tested an injectable, slow-release, uniform, and optimally loaded alginate nanoformulation of CCL21 as a means to provide prolonged intratumoral treatment. The alginate-nanoformulated CCL21, when injected intratumorally into mice bearing neuroblastoma lesions, significantly prolonged survival and decreased the tumor growth rate compared to CCL21 alone, empty nanoparticles, or buffer. Notably, we also observed complete tumor clearance and subsequent full protection against tumor rechallenge in 33% of nanoformulated CCL21-treated mice. Greater intratumoral presence of nanoformulated CCL21, compared to free CCL21, at days 1 and 2 after treatment ended was confirmed through fluorescent labeling and tracking. Nanoformulated CCL21-treated tumors exhibited a general pattern of prolonged increases in anti-tumor cytokines and relatively lower levels of pro-tumor cytokines in comparison to tumors treated with CCL21 alone or buffer only. Thus, this novel nanoformulation of CCL21 is an effective treatment for neuroblastoma, and may have potential for the delivery of CCL21 to other types of solid tumors in the future and as a slow-release delivery modality for other immunotherapies.