Inhibition of the cancer stem cell immune checkpoint SOAT1 suppresses regulatory T cell functions through a...

Area of Science:

• Oncology
• Immunology
• Cell Biology

Background:

• Cancer immunotherapy, including immune checkpoint blockade (ICB), has advanced cancer treatment but faces limitations due to low response rates.
• Identifying novel druggable targets is crucial for improving therapeutic efficacy and overcoming resistance.

Purpose of the Study:

• To investigate the role of SOAT1 in cancer stem cells (CSCs) and evaluate its potential as a therapeutic target.
• To explore the anti-tumor effects and underlying mechanisms of SOAT1 pharmacological inhibition using STK.

Main Methods:

• SOAT1 expression analysis in CSCs.
• Pharmacological inhibition of SOAT1 using STK in preclinical mouse models of various cancers (colon, liver, lung, breast, melanoma).
• Mechanistic studies involving 20(S)-Hydroxycholesterol (20SOHC) release, GPR132 pathway activation in regulatory T cells (Tregs), and immune cell profiling (dendritic cells, CD8+ T cells).
• Combination therapy studies with anti-PD-1 and anti-CTLA-4 ICB.

Main Results:

• SOAT1 is selectively expressed in CSCs.
• Pharmacological inhibition of SOAT1 with STK demonstrated robust anti-tumor effects across multiple cancer types with low toxicity.
• STK treatment led to 20SOHC release, activating the tumor-Treg GPR132 pathway, suppressing Treg function, and enhancing anti-tumor immune responses (dendritic cells and CD8+ T cells).
• STK synergized effectively with anti-PD-1 and anti-CTLA-4 ICB therapies.

Conclusions:

• SOAT1 acts as a CSC metabolism checkpoint that promotes immune evasion.
• SOAT1 inhibition represents a promising therapeutic strategy to enhance cancer immunotherapy efficacy, particularly in combination with ICB.