# In Vitro Maturation of Bone Marrow-Derived Dendritic Cells via STING Activation for T Cell Priming

## TL;DR

This study shows that dendritic cells activated via the STING pathway can effectively stimulate T cells, offering a new approach for cancer immunotherapy.

## Contribution

A novel in vitro method for generating STING-activated dendritic cells that efficiently prime CD8+ T cells is presented.

## Key findings

- STING agonist-stimulated dendritic cells showed enhanced maturation and functionality.
- These dendritic cells effectively primed naïve CD8+ T cells in vitro.
- Optimized culture conditions improved dendritic cell yield and T cell activation.

## Abstract

Dendritic cells (DCs) are crucial for activating the immune system and have great potential in cancer immunotherapy. This study aimed to generate DCs from mouse bone marrow, activate them through the STING signaling pathway, and evaluate their ability to stimulate T cells. Optimized culture conditions and a STING agonist promoted the formation of mature and functional DCs capable of triggering strong CD8+ T cell responses. These findings highlight the potential of STING-activated DCs to enhance anti-tumor immunity and pave the way for developing personalized and effective cancer treatment strategies.

Objective: Dendritic cells (DCs) are the most potent antigen-presenting cells, serving as a bridge between innate and adaptive immunity. Activation of the stimulator of interferon genes (STING) pathway by pathogen-derived DNA induces type I interferon responses and promotes CD8+ cytotoxic T cell activity. This study aimed to establish a protocol for generating immature DCs from murine bone marrow, optimize their maturation in vitro with a STING agonist, and evaluate their ability to prime naïve T cells for potential use in cancer immunotherapy. Methods: Bone marrow cells from C57BL/6 mice were differentiated into immature DCs under growth factor–supplemented conditions. Maturation was induced using a STING agonist and B16 tumor-derived DNA. Naïve CD4+ and CD8+ T cells were isolated via magnetic-activated cell sorting (MACS) and co-cultured with the stimulated DCs. Culture conditions were optimized to enhance DC maturation efficiency, and T cell proliferation was assessed following co-culture. Results: Optimization of the culture system markedly increased the yield of mature DCs. Importantly, co-culture of STING agonist-stimulated DCs with naïve T cells resulted in strong CD8+ T cell proliferation, indicating effective priming. Conclusions: These findings demonstrate the feasibility of generating functional DCs in vitro and highlight their capacity to prime T cells through STING pathway activation. This proof-of-concept supports the development of DC-based platforms as a promising strategy for novel cancer immunotherapies.