The γδ T cell is a promising candidate cell in tumor immunotherapy. However, γδ T cells polarize to CD39 ⁺ γδ Tregs upon colorectal cancer (CRC) induction, and the underlying mechanism remains unclear. Here, we show that the frequency of CD39 ⁺ γδ Tregs, which positively correlated with poor prognosis, was significantly higher in right-sided CRC (RSCRC) than in the left-sided CRC (LSCRC). Interestingly, CD39 ⁺ γδ Tregs from RSCRC showed stronger immunosuppressive phenotype and function than LSCRC. Furthermore, the quantitative mass spectrometry data show that CD39 ⁺ γδ Treg polarization was related to the abnormal activation of the Phospholipase a2-IVa/Arachidonic acid (PLA2G4A/AA) metabolic pathway in RSCRC. Using an in vitro coculture system and an orthotopic murine model of CRC, we show that the overexpression of Pla2g4a in CT26 cells induced CD39 ⁺ γδ Tregs, inhibiting the antitumor immune response. Finally, we found that the overall survival of the PLA2G4A ^hi group was significantly shortened compared with PLA2G4A ^lo RSCRC, while the survival of LSCRC showed the opposite. Collectively, RSCRC with abnormal PLA2G4A expression educates γδ T cells into CD39 ⁺ γδ Tregs to promote tumor progression and metastasis. Our work highlights the interaction between cancer cells and immune cells by distinguishing the primary tumor site and deepens the understanding of the tumor microenvironment and immunosuppression.

Programmed death 1 (PD‑1)‑targeted therapy has benefited patients with microsatellite instability‑high metastatic colorectal cancer (mCRC). However, the efficacy of PD‑1‑targeted therapy is poor in patients with microsatellite‑stable (MSS) mCRC. Therefore, it is imperative to explore additional co‑inhibitory molecular signalling pathways to improve the efficacy of immunotherapy in MSS mCRC treatment. In the present study, the association between cyclin‑dependent kinase 9 (CDK9) expression and the survival of patients with CRC was analysed using RNA sequencing data from 605 patients, including 121 cases of mortality, from human cancer datasets. Furthermore, 35 clinical MSS stage III‑IV CRC specimens were collected to assess CDK9 protein expression by immunohistochemistry, and the frequency of tumor‑infiltrating CD8+ T cells was assessed by flow cytometry. The human cancer datasets demonstrated that upregulation CDK9 significantly shortened the survival of patients with stage II‑IV colon cancer. Additionally, CDK9 mRNA expression was positively correlated with the expression levels of genes associated with immune evasion in the tumor. Notably, CDK9 was expression was upregulated in stage IV CRC compared with para‑cancerous tissues and early‑stage tumors. Interestingly, CDK9 expression was negatively associated with the infiltration of CD8+ T cells at the tumor site. In addition, the expression levels of T‑cell immunoglobulin mucin family member 3 and CD39, proteins associated with exhaustion, on tumor‑infiltrating CD8+ T cells were significantly elevated in patients with abnormal CDK9 expression levels. The present study demonstrated that CDK9 expression was negatively associated with CD8+ T cell infiltration and positively associated with CD8+ T cell exhaustion in MSS mCRC. In conclusion, CDK9 may be utilized to evaluate the prognosis and the immune‑type of the tumor microenvironment in patients with MSS mCRC.

Cancer stem cells (CSCs) are pivotal in tumor resistance to chemotherapy and gastric cancer's rapid proliferation and metastasis. We aimed to explore the CSCs-related genes in gastric cancer epithelial cells. The mRNA expression profile and single-cell sequencing data of gastric cancer were downloaded from the public database. We identified WDR72 as a CSCs-related gene in gastric cancer epithelial cells. WDR72 was highly expressed in gastric cancer tissues, and high expression of WDR72 was associated with inferior prognosis of patients. WDR72 expression had a significant negative correlation with the infiltration of CD8 + T cells and activated memory CD4 + T cells. PD-L1 expression was significantly reduced in gastric cancer patients with high WDR72 expression. WDR72 was correlated with IC50 of multiple small-molecule drugs. We identified a novel CSCs-related gene in gastric cancer epithelial cells, WDR72, which was highly expressed in patients with high stemness scores.