Globally, metastasis, the spread of cancer cells from primary tumors to other organs, accounts for 90% of cancer-related deaths. Despite improvements in cancer treatment, metastatic recurrence remains a risk in the early stage of cancer due to micrometastases. Because of weak immunosuppression, these micrometastases present an opportunity for immune-based anti-metastatic treatments. Aspirin is a cyclooxygenase (COX) inhibitor that reduces metastasis and cancer mortality in non-metastatic patients mainly via an immune modulation mechanism. Aspirin also suppresses the thromboxane A2 (TXA2) production through irreversible inhibition of platelet COX-1.
A recent study published in Nature aimed to investigate how aspirin increases the immune response to cancer metastasis. In particular, this study explores the role of TXA2 in suppressing T cell activity and how COX-1 inhibition can restore T cell function by disrupting this immunosuppressive mechanism. This study also examines the involvement of the Rho Guanine Nucleotide Exchange Factor 1 (ARHGEF1) in TXA2-mediated suppression of T-cell receptor proliferation and signaling along with effector roles.
These animal studies followed UK Home Office guidelines. In this study, mice of the wild-type (C57BL/6) and genetically engineered animals (OT-1 TCRtg, Rag2–/–, MMTV-PyMT, Arhgef1Tm1a, Tbxas1tm1Swl, Tbxa2rtm1Cof, Arhgef1fl/fl, Ncr1tm1.1(icre)Viv, Lyz2tm1(cre)Ifo, Tg(Cd4-cre)1Cwi, Pf4cre Ptgs1fl/fl and mouse metastatic cancer cell lines such as B16-F10 and B78ChOva-mCherry were employed. Various analytic methods like flow cytometry, ex-vivo phosflow assay, Ras Homolog Family Member A (RHOA) pull-down activation assay, RNA-seq analysis, histopathological analysis, and Single-sample gene set enrichment analysis (ssGSEA) were used.
After administration of syngeneic LL/2 Lewis lung melanoma cells, it was observed that there was a reduction in metastasis rate in the Arhgef1-deficient animal compared to control mice. This resulted in the loss of ARHGEF1 expression. Moreover, genes associated with the activation of immune and cytotoxic functions expressions (Gzmb, Ccl4, Klrg1, Gzma, Nkg7, and Cxcl5) were increased in Arhgef1-deficient mice compared to wild-type mice control.
It was found that T cell-specific deletion of ARHGEF1 in Arhgef1fl/fl Cd4cre mice significantly decreased lung metastasis compared to Arhgef1+/+ Cd4cre (cWT) controls. Increased levels of tumor necrosis factor (TNF), interferon gamma (IFNγ), and interleukin-2 (IL-2) were observed in Arhgef1-cKO mice compared to cWT mice. Ovalbumin (OVA)-specific CD8+ T cells in infected Arhgef1-cKO mice showed enhanced expression of the memory marker CD127 compared to cWT mice.
The study demonstrated that 18 Gα12/13-coupled G-protein-coupled receptors (GPCRs) were significantly expressed at mRNA levels in both naïve and activated CD8+ T cells. ARHGEF1 plays a key role in mediating TXA2 signaling in T cells, restricting proliferation and activation, following T Cell Receptor (TCR) signaling.
Additionally, Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)-based genetic disruption of RHOA in primary CRISPR-associated protein 9 (Cas9) expressing CD8+ T cells increased the stimulation-induced ribosomal protein S6 and Extracellular Signal-Regulated Kinase (ERK) phosphorylation.
In-vitro studies revealed that ARHGEF1 and downstream activation of RHOA were needed to suppress TCR-driven kinase phosphorylation mechanism and T cell activation due to TXA2 signaling.
The anti-metastatic activity of aspirin was based on the adaptive immune cells. No variation in the frequency of metastasis was reported in Rag2-deficient mice after aspirin treatment. A decreased frequency of metastasis was reported in ARHGEF1-proficient mice due to genetic loss of the thromboxane synthase pathway.
In conclusion, this research demonstrates that TXA2 regulates the T cell immunity pathway, impacting the prevention and treatment of cancer. This mechanism explains the anti-metastatic properties of aspirin and targeted therapies, leading to the development of new treatment approaches to stop the spread of cancer.
Reference: Yang J, Yamashita-Kanemaru Y, Morris BI, et al. Aspirin prevents metastasis by limiting platelet TXA2 suppression of T cell immunity. Nature. 2025. doi:10.1038/s41586-025-08626-7
