Dual blockade of GSTK1 and CD47 improves macrophage-mediated phagocytosis on cancer cells

Area of Science:

• Immunology
• Cancer Biology
• Molecular Biology

Background:

• CD47 acts as an anti-phagocytic signal, crucial for regulating macrophage responses.
• CD47 blockade is a promising cancer immunotherapy, but often requires additional stimuli for maximal efficacy.
• Unidentified factors can counteract macrophage activity during CD47-targeted therapies.

Purpose of the Study:

• To screen for novel phagocytosis-regulating factors in the context of CD47 blockade.
• To identify new therapeutic targets that enhance the efficacy of CD47-based cancer immunotherapy.
• To investigate the mechanism by which GSTK1 influences macrophage-mediated phagocytosis.

Main Methods:

• Genome-wide human CRISPR-Cas9 library screening was employed to identify phagocytosis regulators.
• Functional assays were performed to assess the impact of GSTK1 disruption on cancer cell phagocytosis by macrophages.
• siGSTK1-loaded nanoparticles (siGSTK1-LNPs) were developed to suppress GSTK1 expression.

Main Results:

• GSTK1 was identified as an anti-phagocytic signal that diminishes the effectiveness of CD47-based therapies.
• Disrupting GSTK1 significantly enhanced cancer cell phagocytosis by macrophages when combined with anti-CD47 antibodies.
• GSTK1 blockade led to increased membrane exposure of calreticulin on cancer cells, a key mechanism for enhanced phagocytosis.
• siGSTK1-LNPs combined with anti-CD47 antibodies demonstrated comparable phagocytosis efficacy.

Conclusions:

• GSTK1 blockade represents a novel and effective strategy to enhance anti-CD47 antibody immunotherapy.
• Targeting GSTK1 offers a promising combination approach for improving cancer treatment outcomes.
• This study introduces a new method to overcome resistance in CD47-based cancer immunotherapies.