Emodinanthrone, a natural precursor of emodin, enhances T-cell anti-tumor via JAK3-STAT1/3 signal and improves anti-PD-1 efficacy against colon cancer.

The macromolecular monoclonal antibodies targeting CTLA-4/PD-1/PD-L1 have revolutionized cancer immunotherapy.

However, their clinical efficacy is limited by poor tissue penetration, strong immunogenicity and frequent cytokine release syndrome (CRS) risk. In contrast, natural small molecules can effectively overcome these challenges due to their strong penetration, minimal immunogenicity and low CRS risk. Developing natural small molecule-mediated immunotherapeutic drugs represents a promising strategy for improving current cancer immunotherapy. A non-traditional T-cell immunomodulatory anti-tumor model was utilized to explore these potential molecules.

LDH release assays and ELISA were used to assess T-cell immune killing activity against tumor cells and cytokine production. The mouse colon cancer lung metastasis model was used to evaluate anti-tumor efficacy in vivo through emodinanthrone monotherapy and combined with anti-PD-1 treatment. Proteomic and phosphoproteomic analyses, combined with blocking and rescue experiments, were employed to investigate the underlying mechanism. The natural product emodinanthrone (EA), a precursor of emodin, was first identified as a potential T-cell immunomodulator.

Mechanistic studies revealed that EA exerts immunomodulatory effects on T cells to eliminate multiple tumor cells, mainly by enhancing the JAK3-STAT1/3 signaling axis, leading to increased expression of granzyme B, perforin, and IFN-γ. In vivo, EA treatment significantly reduced the number of lung metastatic nodules by approximately 72.4% and extended overall survival by approximately 42.8%.

Furthermore, combination treatment with anti-PD-1 antibody markedly decreased the metastasis rate from 59% to 12.8% and improved the survival rate from 30% to 70%.

This study first reveals that emodinanthrone possesses T-cell immunomodulatory anti-tumor activity. In vivo findings further support its development as a promising candidate to improve anti-PD-1 efficacy.