S1PR4 ablation reduces tumor growth and improves chemotherapy via CD8+ T cell expansion

Area of Science:

• Immunology
• Oncology
• Molecular Biology

Background:

• Tumor immunosuppression impedes effective cancer treatment.
• Sphingosine-1-phosphate (S1P) and its receptors (S1PR1-5) regulate carcinogenesis.
• S1P's role in immune cell trafficking complicates its therapeutic targeting in cancer.

Purpose of the Study:

• To investigate the role of the immune cell-specific receptor S1PR4 in tumor development and therapy.
• To determine the impact of S1PR4 ablation on anti-tumor immunity, particularly CD8+ T cell responses.
• To elucidate the molecular mechanisms by which S1PR4 influences CD8+ T cell function.

Main Methods:

• Ablation of S1PR4 in murine models of mammary and colitis-associated colorectal cancer.
• Assessment of tumor development, therapy success, and CD8+ T cell abundance.
• Transcriptome analysis to identify S1PR4-regulated genes in CD8+ T cells.
• Correlation of PIK3AP1 expression with CD8+ T cell proliferation and clinical data in human cancers.

Main Results:

• Ablation of S1PR4 delayed tumor development and improved cancer therapy outcomes in mouse models.
• S1PR4 deficiency led to increased CD8+ T cell abundance within tumors.
• Transcriptome analysis identified Pik3ap1 and Lta4h as key mediators of S1PR4's cell-intrinsic effects on CD8+ T cells.
• PIK3AP1 expression correlated positively with CD8+ T cell proliferation and clinical parameters in human breast and colon cancer.

Conclusions:

• S1PR4 plays a previously unrecognized tumor-promoting role by restricting CD8+ T cell expansion.
• Targeting S1PR4 represents a potential therapeutic strategy to enhance anti-tumor immunity and improve cancer treatment efficacy.
• The S1PR4-PIK3AP1 axis is a critical regulator of CD8+ T cell function in the tumor microenvironment.