TY - JOUR
T1 - 1034 Development of HLA class I expressing humanized patient-derived xenograft (hu-PDX) mouse models for the study of mRNA-based cancer vaccines in triple-negative breast cancer
AU - Chervo, Maria F
AU - Qian, Wei
AU - Ortega Martinez, Karina A
AU - Zhou, Jianying
AU - Shroff, Raghav
AU - Mancino, Chiara
AU - Rojas, Liliana Guzman
AU - Taraballi, Francesca
AU - Cooke, John P
AU - Gollihar, Jimmy D
AU - Chang, Jenny C
PY - 2024/11/1
Y1 - 2024/11/1
N2 - Background Messenger RNA (mRNA)-based cancer vaccines targeting tumor-specific neoantigens represent a promising strategy to treat aggressive, multi-drug resistant tumors such as triple-negative breast cancer (TNBC). The development of more predictive preclinical models are needed to drive the rational design of cancer vaccine candidates and minimize failures in future clinical trials. Here we established a humanized patient-derived xenograft (hu-PDX) mouse model of TNBC that recapitulates interactions between human immune cells and tumors to investigate the effectiveness of mRNA-based cancer vaccines in vivo.Methods Tumor neoantigens were identified in the TNBC PDX model MC1 using a proprietary algorithm that prioritizes vaccine candidates on their likelihood to induce neoantigen-specific T-cell responses. mRNA encoding 20 selected HLA-A2-restricted neoantigens (Neo20 cancer vaccine) was synthesized and encapsulated into lipid nanoparticles (LNPs) for in vivo administration. To assess the Neo20 cancer vaccine in vivo, we developed a hu-PDX mouse model of TNBC expressing human leukocyte antigen (HLA) class I. Briefly, human immunity was reconstituted in female HLA-A2 transgenic NSG mice (NSG-HLA-A2/HHD, The Jaxson Laboratory) through I.V. transplantation of human CD34+ hematopoietic stem cells from HLA-A2+ cord blood donors. Mice showing efficient human CD45+ (hCD45+) cell engraftment were implanted with MC1 tumors into the mammary fat pad. Once the tumors were established, MC1-hu-PDX mice received Neo20 mRNA-LNPs (10 µg mRNA/mouse) or empty LNPs as a control by intramuscular injection. Animals were treated every three days for one week and evaluated for vaccine immunogenicity and tumor growth. To analyze neoantigen-specific T cell responses, splenocytes were harvested 7 days after the last dose and pulsed with vaccine peptides for human interferon (IFN)-γ ELISpot assay.Results Flow cytometry analysis of hCD45+ subpopulations of cells confirmed human reconstitution with T-cells, B-cells, myeloid cells/macrophages, and NK cells in blood, spleen, and bone marrow collected from MC1-hu-PDX mice. Two out of five mice treated with Neo20 vaccine generated functional human T-cell subsets with HLA-A2-restricted immune responses against multiple vaccine peptides as measured by ex vivo IFN-γ production. We observed a small but not significant change in tumor size between the Neo20 vaccine and control group after one week of treatment, suggesting that our treatment protocol should be further optimized to improve neoantigen-specific T cells and associated anti-tumor responses.Conclusions This study provides evidence associated with mRNA-LNP cancer vaccines against TNBC supporting the use of hu-PDX mice as a model to preclinically validate vaccine candidates, mRNA doses, and treatment schedules.Ethics Approval This study was approved by Houston Methodist Research Institute’s Institutional Animal Care and Use Committee (IACUC); approved protocols: IS00007220, IS00006475.
AB - Background Messenger RNA (mRNA)-based cancer vaccines targeting tumor-specific neoantigens represent a promising strategy to treat aggressive, multi-drug resistant tumors such as triple-negative breast cancer (TNBC). The development of more predictive preclinical models are needed to drive the rational design of cancer vaccine candidates and minimize failures in future clinical trials. Here we established a humanized patient-derived xenograft (hu-PDX) mouse model of TNBC that recapitulates interactions between human immune cells and tumors to investigate the effectiveness of mRNA-based cancer vaccines in vivo.Methods Tumor neoantigens were identified in the TNBC PDX model MC1 using a proprietary algorithm that prioritizes vaccine candidates on their likelihood to induce neoantigen-specific T-cell responses. mRNA encoding 20 selected HLA-A2-restricted neoantigens (Neo20 cancer vaccine) was synthesized and encapsulated into lipid nanoparticles (LNPs) for in vivo administration. To assess the Neo20 cancer vaccine in vivo, we developed a hu-PDX mouse model of TNBC expressing human leukocyte antigen (HLA) class I. Briefly, human immunity was reconstituted in female HLA-A2 transgenic NSG mice (NSG-HLA-A2/HHD, The Jaxson Laboratory) through I.V. transplantation of human CD34+ hematopoietic stem cells from HLA-A2+ cord blood donors. Mice showing efficient human CD45+ (hCD45+) cell engraftment were implanted with MC1 tumors into the mammary fat pad. Once the tumors were established, MC1-hu-PDX mice received Neo20 mRNA-LNPs (10 µg mRNA/mouse) or empty LNPs as a control by intramuscular injection. Animals were treated every three days for one week and evaluated for vaccine immunogenicity and tumor growth. To analyze neoantigen-specific T cell responses, splenocytes were harvested 7 days after the last dose and pulsed with vaccine peptides for human interferon (IFN)-γ ELISpot assay.Results Flow cytometry analysis of hCD45+ subpopulations of cells confirmed human reconstitution with T-cells, B-cells, myeloid cells/macrophages, and NK cells in blood, spleen, and bone marrow collected from MC1-hu-PDX mice. Two out of five mice treated with Neo20 vaccine generated functional human T-cell subsets with HLA-A2-restricted immune responses against multiple vaccine peptides as measured by ex vivo IFN-γ production. We observed a small but not significant change in tumor size between the Neo20 vaccine and control group after one week of treatment, suggesting that our treatment protocol should be further optimized to improve neoantigen-specific T cells and associated anti-tumor responses.Conclusions This study provides evidence associated with mRNA-LNP cancer vaccines against TNBC supporting the use of hu-PDX mice as a model to preclinically validate vaccine candidates, mRNA doses, and treatment schedules.Ethics Approval This study was approved by Houston Methodist Research Institute’s Institutional Animal Care and Use Committee (IACUC); approved protocols: IS00007220, IS00006475.
U2 - 10.1136/jitc-2024-SITC2024.1034
DO - 10.1136/jitc-2024-SITC2024.1034
M3 - Article
VL - 12
SP - A1155
JO - J Immunother Cancer
JF - J Immunother Cancer
IS - Suppl 2
ER -