Anti-PD-1/PD-L1 therapies represent significant advancements in cancer treatment. However, tumor growth has been observed in some patients following treatment with anti-PD-1/PD-L1 agents, leading to disease progression. In this article, authors found that PD-1 deficiency enhance Treg suppressive function and provide comprehensive data to explain the mechanism how anti-PD-1 treatment cause tumor growth.
Changes in Treg phenotypes were observed after PD-1 inhibition
In animal model, it was found that the absolute number of Treg increased in Pd1-/- mouse and in Pd1fl/flFoxp3ERT2Cre mouse treated with tamoxifen. These Pd1-/-Tregs exhibited enhanced suppressive phenotypes, characterized by the upregulation of coinhibitory receptors, including CD30, CTLA4, GARP, GITR.
p.s. Tamoxifen can target ERT and activate Cre/loxp systems, leading to PD1 knockout.
The role of CD30+Tregs was confirmed at the transcriptional and functional levels
At the transcriptional level, differential gene expression analysis showed that Tnfrsf8 was significantly upregulated in Pd1-/-Tregs. In co-culture assays, Pd1-/-Tregs exhibited enhanced suppressive function on Teff prolification compared to WT Tregs. These Treg promoted tumor growth in adoptive transfer (AT) experiments, suggesting that their enhanced suppressive function was maintained within the tumor microenvironment (TME). Notably, the promotion of tumor growth can be inhibited by blocking the CD30 signaling pathway.
Based on previous findings, we found that PD-1 inhibition led to CD30 upregulation, which in turn increased the suppressive function of CD30+Treg. Furthermore, CD30 expression was regulated via the IL-2-STAT5 signaling. In cell culture, CD30 could not be induced by PD-1 antibodies in the absence of IL-2. Upon PD-1 antibody treatment, STAT5 phosphorylation was induced in Treg cells. Chromatin immunoprecipitation followed by sequencing (ChIP-seq) further demonstrated that STAT5 bound to the Tnfrsf8 locus after IL-2 stimulation.
What is the driving factor?
Here arises an important qestion: does CD30 upregulation in Treg cells results from the tumor microenvironment (TME) or from exogenous anti-PD-1 therapy? To investigate this, the researchers analyzed both peripheral blood mononuclear cells (PBMCs) and tumor-infiltrating lymphocytes (TILs) from melanoma patients. No alteration in CD30 mRNA expression was observed in either cell population, suggesting that the TME alone does not drive CD30 upregulation in Treg cells. On the other hand, TNFRSF8 mRNA expression was significantly upregulated in melanoma patients after anti-PD1 treatment. In addition, it was also found that CD30 predominantly expressed in non-responders to PD-1 therapy and was associated with poor survival outcomes.
Reference
- Lim, J.X., McTaggart, T., Jung, S.K. et al. PD-1 receptor deficiency enhances CD30+ Treg cell function in melanoma. Nat Immunol (2025). https://doi.org/10.1038/s41590-025-02172-0
