High-Throughput Heterospheroid-Based Screening Identifies Drugs That Reprogram Tumor-Associated Macrophages

Area of Science:

• Immunology
• Oncology
• Pharmacology

Background:

• The tumor microenvironment (TME) promotes immune evasion and immunotherapy resistance, partly by recruiting pro-tumor M2-like macrophages.
• Tumor-associated macrophages (TAMs) often exhibit an M2-like phenotype within the TME, suppressing anti-tumor immunity.

Purpose of the Study:

• To identify compounds (TAM activators) that can reprogram M2-like TAMs to an anti-tumor M1-like phenotype.
• To establish a novel screening platform for identifying TAM activators using cancer cell-macrophage heterospheroids.

Main Methods:

• Co-culture of liver cancer cells with macrophages to form heterospheroids, mimicking the TME.
• Flow cytometry and fluorescence microscopy to assess macrophage phenotype and infiltration.
• High-content imaging screen to identify TAM-activating compounds.

Main Results:

• Heterospheroids suppressed M1 marker induction in macrophages compared to homospheroids.
• Two compounds, alprostadil and HX531, were identified as TAM activators.
• Alprostadil promoted M1-like TAM polarization, increased CD8+ T cell infiltration, and enhanced anti-PD-1 therapy efficacy in mice.

Conclusions:

• Heterospheroid culture effectively recapitulates the immunosuppressive TME and can be used to screen for TAM activators.
• Alprostadil shows potential as a novel cancer immunotherapeutic agent by reprogramming TAMs and enhancing T cell responses.
• This approach enables the development of new cancer immunotherapies targeting TAMs.