The loss of epithelial Smad4 drives immune evasion via CXCL1 while displaying vulnerability to combinatorial...

Area of Science:

• Oncology
• Immunology
• Gastroenterology

Background:

• SMAD4 is frequently inactivated in gastric cancer (GC).
• The role of SMAD4 in tumor immunity is not well understood.
• Understanding SMAD4's impact on GC immunity is crucial for developing effective treatments.

Purpose of the Study:

• To investigate how SMAD4 deficiency in GC cells affects tumor immunity.
• To identify mechanisms by which SMAD4-deficient GC cells evade immune surveillance.
• To explore potential therapeutic strategies targeting SMAD4-deficient GC.

Main Methods:

• Utilized Smad4-deficient and proficient stomach organoids and allografts in immunocompetent mice.
• Analyzed immune cell populations including dendritic cells (DCs), cytotoxic T cells, and granulocytic myeloid-derived suppressor cells (G-MDSCs).
• Assessed expression of immune markers such as CD133, CXCL1, PD-L1, and 4-1BBL.
• Evaluated the efficacy of combinatorial immune checkpoint blockade (ICB) therapies.

Main Results:

• Smad4-deficient GC cells evade host immunity and form tumors in mice.
• Smad4 deficiency leads to expanded CD133+ cancer stem-like cells.
• Suppressed dendritic cell differentiation and cytotoxic T cells, with increased G-MDSCs via CXCL1.
• Increased PD-L1 and decreased 4-1BBL expression in Smad4-deficient GC cells.
• Combinatorial ICB (anti-PD-L1/anti-CTLA-4 or anti-4-1BB) effectively treated Smad4-deficient tumors resistant to monotherapy.

Conclusions:

• Loss of SMAD4 in GC promotes immune evasion and tumor growth.
• Smad4 deficiency creates a unique immunosuppressive tumor microenvironment.
• Targeting immune checkpoints offers a promising therapeutic approach for advanced SMAD4-deficient GC.