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<p>Activation of the T cell receptor (TCR) complex is fundamental to initiating adaptive immune responses, particularly in CD8⁺ cytotoxic T lymphocytes that mediate anti-tumor immunity. However, the immunosuppressive tumor microenvironment often impairs TCR signaling, limiting the efficacy of T cell-based cancer immunotherapies. Here, we report the identification of rosmarinic acid (RA), a naturally occurring polyphenolic compound, as a potent small molecule enhancer of TCR signaling. RA significantly augments IL-2 and IFN-γ production, promotes T cell proliferation, and enhances cytotoxicity of CD8⁺ T cells in vitro. Mechanistically, RA directly binds to MEK1, a key kinase in the MAPK/ERK pathway, with high affinity, leading to reduced MEK1 phosphorylation and downstream signaling activation. Transcriptomic and metabolic profiling of RA-treated CD8⁺ T cells revealed upregulation of genes associated with TCR signaling, calcium flux, PPAR signaling, and oxidative phosphorylation, indicating a broad remodeling of T cell effector function and metabolism. In vivo, RA treatment significantly suppressed tumor growth, increased tumor-infiltrating lymphocyte (TIL) frequency, and improved survival in MC38 tumor-bearing mice. These effects were abrogated upon CD8⁺ T cell depletion, confirming their central role. Furthermore, RA synergized with anti-PD-1 therapy and enhanced the efficacy of adoptively transferred OT-I T cells in colorectal&#xa0;tumor-bearing hosts. Collectively, our findings reveal RA as a novel immunomodulatory agent that boosts CD8⁺ T cell responses via MEK1-mediated TCR signaling enhancement, providing a promising strategy for drug repurposing in cancer immunotherapy.</p>

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Repurposing rosmarinic acid as an anti-colorectal cancer agent through bolstering T cell anti-tumor immunity by enhancing activation of MEK1-mediated TCR signaling

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年4月2日

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  • Zhengchun Kang,
  • Xu Li,
  • Xiuzhu Ma,
  • Feihu Yan,
  • Zhen Wang

摘要

Activation of the T cell receptor (TCR) complex is fundamental to initiating adaptive immune responses, particularly in CD8⁺ cytotoxic T lymphocytes that mediate anti-tumor immunity. However, the immunosuppressive tumor microenvironment often impairs TCR signaling, limiting the efficacy of T cell-based cancer immunotherapies. Here, we report the identification of rosmarinic acid (RA), a naturally occurring polyphenolic compound, as a potent small molecule enhancer of TCR signaling. RA significantly augments IL-2 and IFN-γ production, promotes T cell proliferation, and enhances cytotoxicity of CD8⁺ T cells in vitro. Mechanistically, RA directly binds to MEK1, a key kinase in the MAPK/ERK pathway, with high affinity, leading to reduced MEK1 phosphorylation and downstream signaling activation. Transcriptomic and metabolic profiling of RA-treated CD8⁺ T cells revealed upregulation of genes associated with TCR signaling, calcium flux, PPAR signaling, and oxidative phosphorylation, indicating a broad remodeling of T cell effector function and metabolism. In vivo, RA treatment significantly suppressed tumor growth, increased tumor-infiltrating lymphocyte (TIL) frequency, and improved survival in MC38 tumor-bearing mice. These effects were abrogated upon CD8⁺ T cell depletion, confirming their central role. Furthermore, RA synergized with anti-PD-1 therapy and enhanced the efficacy of adoptively transferred OT-I T cells in colorectal tumor-bearing hosts. Collectively, our findings reveal RA as a novel immunomodulatory agent that boosts CD8⁺ T cell responses via MEK1-mediated TCR signaling enhancement, providing a promising strategy for drug repurposing in cancer immunotherapy.