Modification of the Tumor Microenvironment Enhances Immunity with Plasmid Gene Therapy

Rheumatology and Immunology Medicine Biochemistry Oncology Life Sciences Immunology
tumor microenvironment plasmid gene therapy immunity MHC-I PD-L1 antitumor effect electroporation

The research team consisting of Guilan Shi, Jody Synowiec, Julie Singh, and Richard Heller published a paper titled “Modification of the tumor microenvironment enhances immunity with plasmid gene therapy” in Cancer Gene Therapy. The background of the study stems from current challenges in the field of tumor immunotherapy, such as tumor cells evading immune surveillance, particularly through regulation of MHC-I molecule and PD-L1 expression, hindering the cytotoxic effects of T cells. Therefore, investigating the mechanisms of upregulation of these molecules and their application potential has important clinical significance.

Research Background and Motivation

Tumor cells often evade immune surveillance by interfering with MHC-mediated antigen presentation and expressing inhibitory receptors like PD-L1. During tumor development and progression, MHC-I molecules present tumor-associated antigens, promoting the cytotoxic effects of T lymphocytes. However, loss of MHC-I expression is commonly observed and is associated with poorer prognosis. PD-L1 expression is also an important biomarker for predicting the efficacy of immune checkpoint inhibitors. Current research mostly focuses on the efficacy of exogenous gene delivery, neglecting the role of plasmid vectors themselves. This study aims to investigate the impact of plasmid vectors on the expression of immunity-related molecules in host cells, especially the regulatory mechanisms of MHC-I and PD-L1.

Source of the Paper and Authors

This study was completed by the team from the University of South Florida, comprising Guilan Shi, Jody Synowiec, Julie Singh, and Richard Heller, and was published in Cancer Gene Therapy. The paper was published online on February 9, 2024.

Research Methods and Procedures

Research Subjects and Experimental Procedures

The study selected three cell lines: 4T1 breast cancer cells, B16F10 melanoma cells, and KPC pancreatic cancer cells. During the experiment, the plasmid vectors pUMVC3 and pVAX1 were introduced into cells and mouse tumor models using electroporation, and changes in tumor growth and expression of immunity molecules were observed.

To test the antitumor effects of plasmid DNA in vivo, the research team constructed mouse models of B16F10 melanoma, 4T1 breast cancer, and KPC pancreatic cancer. Plasmid DNA was injected directly into tumors using electroporation technology. Flow cytometry was employed to detect changes in the expression of MHC-I and PD-L1 on tumor cell surfaces. Additionally, Western blot analysis was used to assess related signaling pathways involved in the expression of MHC-I and PD-L1.

Experimental Results

Results indicated that plasmid vectors pUMVC3 and pVAX1 significantly upregulated the expression of MHC-I and PD-L1 on the surface of tumor cells following electroporation treatment. Flow cytometry confirmed the upregulation of MHC-I and PD-L1 in all three tumor cell lines, and tumor growth inhibition was also observed in tumor-bearing mouse models.

Notably, RNA sequencing and Western blot analysis revealed that IFN-γ, but not IL-12, induced upregulation of MHC-I and PD-L1 at different concentrations, while the p-STAT1 signaling pathway was not involved with the function of plasmid vectors. This suggests that plasmid DNA may act as “danger signals” participating in the regulation of immunity molecules through other pathways.

Conclusion and Research Value

The study concluded that plasmid vectors pUMVC3 and pVAX1, when introduced into tumor cells and animal models via electroporation technology, can upregulate the expression of MHC-I and PD-L1, thereby enhancing antitumor immune responses. This finding holds significant importance for further exploration of tumor gene therapy and its mechanisms, providing a new pathway for regulating the immune microenvironment and enhancing the efficacy of existing immunotherapies.

Research Highlights

  1. Plasmid vectors regulate immune molecules MHC-I and PD-L1, further demonstrating their potential role in gene therapy.
  2. Plasmid vectors are delivered safely and effectively into tumor cells using electroporation technology without causing systemic toxicity.
  3. The study elucidates the mechanisms of upregulation of surface molecules on tumor cells and their contribution to antitumor responses, providing new ideas for tumor gene therapy.

Other Valuable Information

The study suggests that plasmid vectors may also regulate other immunity-related molecules such as CD40, OX40L, 4-1BBL, and tumor-associated antigens (e.g., NY-ESO-1, MAGE family). Future research could further explore the regulatory mechanisms of these molecules, revealing the broad application potential of plasmid gene therapy in cancer and other diseases.

Research Limitations

The current study primarily revealed preliminary results regarding the regulation of MHC-I and PD-L1 expression by plasmid vectors, with specific signal transduction mechanisms remaining unclear, requiring further experimental validation. Additionally, in vivo experiments need to increase sample sizes and evaluate the reliability and reproducibility of the results.

Summary

This study provides a new perspective for plasmid gene therapy, significantly enhancing antitumor immune responses through the immune regulatory roles of plasmid vectors. The research results establish a theoretical foundation for future expansions of plasmid gene therapy applications and provide a research direction for further uncovering the impact of plasmid vectors on the immune microenvironment.