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Updated: Jun 15, 2025
Flow Cytometry-Based Isolation and Therapeutic Evaluation of Tumor-Infiltrating Lymphocytes in a Mouse Model of Pancreatic Cancer
Published on: January 17, 2025
Oncolytic adenovirus encoding variant interleukin-2 combined with chemotherapy enables PD-L1 inhibition in pancreatic
Santeri A Pakola1, Nea Ojala1, Tatiana V Kudling1
1Cancer Gene Therapy Group, Translational Immunology Research Program, Faculty of Medicine, University of Helsinki, Helsinki, Finland.
Abstract:
Pancreatic ductal adenocarcinoma (PDAC) is a cancer with dismal prognosis due to resistance to most current therapies. Although immunotherapy has improved the treatment of many solid cancers, pancreatic cancer remains resistant to immunotherapy due to immunosuppressive tumor microenvironment, limited lymphocyte infiltration and lack of neoantigens. Oncolytic adenoviruses are a possible solution to treatment resistance in PDAC due to their ability to elicit lymphocyte trafficking and epitope spreading. Herein, we tested if an oncolytic adenovirus encoding a variant interleukin-2 molecule (Ad5/3-E2F-d24-vIL2), could enable immune checkpoint inhibitor (ICI) therapy in PDAC when combined with chemotherapy. Rationale for Ad5/3-E2F-d24-vIL2 was tested in vitro, where increase in programmed death ligand 1 (PD-L1) expression was seen after virotherapy and chemotherapy. Expression of other B7 family proteins was characterized in mono- and co-culture settings of cancer cells, fibroblasts, and macrophages. The combination therapy of virotherapy, chemotherapy and ICI was characterized in freshly resected ex vivo pancreatic tumor samples. Combination of ICI with virotherapy showed increased interferon and chemokine production in samples, with expansion of cytotoxic CD8 + T cells seen by flow cytometry. In vivo evaluation of the triple combination therapy in a Syrian hamster model showed improved tumor growth control and overall survival, with concurrent increase in intratumoral lymphocytes during therapy. Animals cured with the therapy showed resistance to re-challenge with the same cell line, supportive of successful generation of anti-tumor immunity in the animals. The combination treatment of Ad5/3-E2F-d24-vIL2, chemotherapy, and checkpoint inhibition is a promising treatment modality to tackle treatment resistance in PDAC.
Insights
This study shows that combining oncolytic adenovirus (Ad5/3-E2F-d24-vIL2), chemotherapy, and immune checkpoint inhibitors can overcome treatment resistance in pancreatic cancer (PDAC) by boosting anti-tumor immunity.
Area of Science:
- Oncology
- Immunotherapy
- Virology
Background:
- Pancreatic ductal adenocarcinoma (PDAC) exhibits resistance to current therapies, including immunotherapy, due to an immunosuppressive tumor microenvironment.
- Limited lymphocyte infiltration and a lack of neoantigens contribute to PDAC's resistance to immunotherapy.
- Oncolytic adenoviruses offer a potential strategy to overcome PDAC treatment resistance by promoting lymphocyte trafficking and epitope spreading.
Purpose of the Study:
- To evaluate the efficacy of combining an oncolytic adenovirus (Ad5/3-E2F-d24-vIL2) with chemotherapy and immune checkpoint inhibitors (ICI) for treating PDAC.
- To investigate the in vitro and ex vivo effects of this combination therapy on immune responses and tumor cell characteristics.
- To assess the in vivo therapeutic potential and immune-generating capacity of the triple combination therapy in a preclinical model.
Main Methods:
- In vitro studies assessed programmed death ligand 1 (PD-L1) and other B7 family protein expression following virotherapy and chemotherapy.
- Ex vivo analysis of resected pancreatic tumor samples evaluated the combination of virotherapy, chemotherapy, and ICI for immune mediator production and T cell expansion.
- In vivo studies in a Syrian hamster model tested the triple combination therapy for tumor growth control, survival, and induction of anti-tumor immunity.
Main Results:
- In vitro and ex vivo studies demonstrated increased PD-L1 expression, interferon, and chemokine production with combination therapy.
- Flow cytometry confirmed the expansion of cytotoxic CD8+ T cells in treated tumor samples.
- In vivo triple combination therapy significantly improved tumor growth control and overall survival in a hamster model, inducing intratumoral lymphocyte increase and resistance to tumor re-challenge.
Conclusions:
- The combination of Ad5/3-E2F-d24-vIL2, chemotherapy, and ICI shows promise in overcoming treatment resistance in PDAC.
- This triple therapy approach effectively enhances anti-tumor immune responses, including lymphocyte infiltration and activity.
- The findings support the development of this combination therapy as a potential new treatment modality for pancreatic cancer.
