Thymosin α1 promotes the activation of myeloid-derived suppressor cells in a Lewis lung cancer model by upregulating Arginase 1.

Biochem Biophys Res Commun

Cancer Center, Chinese PLA General Hospital and Chinese PLA Medical School, 28 FuXing Road, Beijing 100853, PR China; International Joint Cancer Institute, The Second Military Medical University, 800 Xiang Yin Road, Shanghai 200433, PR China. Electronic address:

Published: August 2015

AI Article Synopsis

  • Thymosin α1 (Tα1) has shown limited anti-tumor effects when used alone in cancer therapy, particularly in melanoma models.
  • Tα1 treatment increased the presence of CD8(+) T cells but did not effectively inhibit tumor growth, as it also stimulated immunosuppressive myeloid-derived suppressor cells (MDSCs).
  • The enhanced suppression of anti-tumor immunity due to MDSCs was linked to Arginase 1 production, which was regulated through TLRs/MyD88 signaling pathways, suggesting that targeting these pathways could improve Tα1’s effectiveness in cancer treatment.

Article Abstract

Thymosin α1 (Tα1) has been tested for cancer therapy for several years, in most cases, the anti-tumor effect of Tα1 was limited, especially when Tα1 was used as a single agent. The role of Tα1 in cancer treatment and the regulatory mechanisms by which Ta1 takes effects are not yet completely understood. Using a Lewis lung caner model, here we report that Tα1 used alone elevated CD8(+) T cells, but failed to inhibit tumor growth. Furthermore, immunosuppressive myeloid-derived suppressor cells (MDSCs) showed heightened Arginase 1 production in response to Tα1 treatment, which led to stronger suppression of anti-tumor immunity. In addition, the upregulation of ARG1 was dependent on TLRs/MyD88 signaling, blocking MyD88 signaling abrogated the enhanced ARG1 expression and restored the anti-tumor efficacy of Tα1. This study provides the first demonstration that Tα1 treatment activates but not expands MDSCs via MyD88 signaling, which indicates better immunotherapeutic strategy of Tα1 against cancer.

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http://dx.doi.org/10.1016/j.bbrc.2015.06.132DOI Listing

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