Clustered macrophages cooperate to eliminate tumors via coordinated intrudopodia

Area of Science:

• Tumor microenvironment
• Cellular organization
• Immunology

Background:

• Macrophages are abundant in solid tumors.
• Their spatial organization and functions, like phagocytosis, are not fully understood.
• Nearest neighbor interactions are crucial for macrophage-mediated anti-cancer activity.

Purpose of the Study:

• Investigate the formation and function of macrophage clusters in tumors.
• Identify pathways driving macrophage clustering.
• Characterize the role of novel pseudopodia, termed 'intrudopodia', in tumor cell phagocytosis.

Main Methods:

• Observation of dynamic macrophage clusters in tumor models.
• Reductionist approaches to study cluster formation.
• Analysis of M1 and M2 macrophage polarization and behavior on low-adhesion substrates.
• Investigation of cell-cell adhesion receptors and actomyosin contractility.
• Microscopy to visualize intrudopodia and cancer cell interactions.

Main Results:

• Macrophage clusters form over hours on low-adhesion substrates after M1 polarization.
• Clusters are dynamic, reorganizing on minute timescales.
• M1 macrophages upregulate adhesion receptors and suppress contractility, promoting clustering.
• Decreased cortical tension in M1 macrophages facilitates intrudopodia extension.
• Intrudopodia extend between cancer cells, facilitating detachment and phagocytosis.
• M2 macrophages disperse, unlike M1 clusters.

Conclusions:

• Macrophage clustering is a key mechanism for enhancing phagocytosis in solid tumors.
• Intrudopodia are critical for coordinated cancer cell detachment and engulfment.
• M1 macrophage polarization drives cluster formation and cooperative phagocytic activity.
• Understanding these dynamics offers therapeutic potential for cancer treatment.