New Progress in the Development of Genetically Engineered Macrophages from Human Pluripotent Stem Cells for Cancer Therapy

2024-06-24

The research team led by Dr. Guangjin Pan at the Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, published a paper in Molecular Therapy - Methods & Clinical Development, entitled ‘Large-scale generation of IL-12 secreting macrophages from human pluripotent stem cells for cancer therapy’. The research team offers a novel strategy for large-scale production of genetically engineered macrophages (GEMs) for solid tumor treatment. This research also unveils functional enhanced anti-tumor GEMs, paving the way for further development and application of this technology.

Macrophages play a critical role in tumor development, migrating to and residing in the tumor microenvironment (TME). Compared to other immune cells like T cells and NK cells, macrophages have better tumor infiltration capacity, making them a promising target for solid tumor treatment. However, TME contains numerous immunosuppressive mechanisms, prompting researchers to explore the potential of GEMs for regulating the TME and treating cancer. These GEMs aim to improve the immune environment within the TME. Nevertheless, limitations in macrophage sources and difficulties in genetic modification have hindered the widespread application of macrophage-based therapies. Therefore, it is crucial to develop more effective methods to overcome these limitations for GEMs therapy in solid tumors.

 

This study overcomes these limitations by using human Pluripotent Stem cells (hPSCs) to generate mature macrophages (iMacs) through directed differentiation. Beginning with 10⁶ hPSCs in a single T150 culture flask, researchers can produce over 10⁹ mature macrophages within a month, addressing the issue of limited cell sources. Utilizing the self-renewal capabilities of hPSCs, the team implemented gene editing to integrate the IL12 gene into specific safety loci within hPSCs. This process results in the production of stable IL12-secreting GEMs (iMac_IL12) through the differentiation system. The iMacs and iMac_IL12 express macrophage-related markers and exhibit typical macrophage characteristics, such as phagocytosis and polarization. Their transcriptome profiles closely resemble those of macrophages derived from human peripheral blood mononuclear cells. IL12, known for boosting immunity by stimulating NK cells and T cells, holds immense potential for improving the TME. However, its short half-life and significant side effects when administered systemically pose challenges. This research demonstrates that intravenous transplantation of iMac_IL12 enables their recruitment and stable residence within solid tumor tissues in mice, effectively mitigating side effects.

 

The researchers observed that iMac_IL12 can induce the production of large amounts of IFN-γ from PBMCs, enhancing the immune response. Both in vitro and in vivo experiments revealed that iMac_IL12 positively impacts the maintenance, proliferation, and activation of CD8+ T cells, while suppressing T cell exhaustion. Furthermore, iMac_IL12 significantly promotes T cell-mediated killing of tumor cell lines, including cervical cancer, glioma, and lung cancer. In CDX models using mice, iMac_IL12 combined with T cells effectively inhibited tumor growth and prolonged survival. The same beneficial effect was observed in mouse tumor metastasis models, where iMac_IL12 significantly reduced tumor burden, extended survival, and minimized the spread of tumor cells to major organs.

This study successfully addresses the source barrier faced in clinical application of macrophage products. The differentiated iMacs circumvent the safety and efficiency issues associated with gene editing and viral integration in macrophages. These GEMs exhibit strong T cell-dependent anti-tumor effects, significantly inhibiting tumor growth and systemic metastasis, ultimately leading to increased cancer survival rates.

The first author of this research is Dr. Baoqiang Kang. The corresponding authors are Dr. Guangjin Pan and Dr. Yanling Zhu from the Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences. This research was supported by the National Key Research and Development Program of China, the National Natural Science Foundation of China, the Science and Technology Program of Guangdong Province, and the Guangzhou Key Research and Development Program.