Hypoxia drives HIF2-dependent reversible macrophage cell cycle entry.

Area of Science:

• Immunology
• Cell Biology
• Cancer Research

Background:

• Low-oxygen conditions (hypoxia) typically cause cell-cycle arrest in dividing cells.
• Macrophages are usually quiescent but can proliferate when stimulated by tissue signals.

Purpose of the Study:

• To investigate the effect of hypoxia on macrophage cell cycle progression.
• To elucidate the molecular mechanisms driving hypoxia-induced cell cycle entry in macrophages.
• To assess the relevance of these findings in the context of tumor-associated macrophages (TAMs).

Main Methods:

• Exposure of macrophages to hypoxic conditions (1% oxygen tension).
• Analysis of cell cycle progression using flow cytometry and molecular markers.
• Investigation of the role of HIF2α and prolyl hydroxylase (PHD) inhibitors.
• Single-cell transcriptomic analysis of tumor-associated macrophages (TAMs) in lung cancer.

Main Results:

• Hypoxia induces reversible entry into the cell cycle in macrophages, mainly transitioning from G0-G1 to S phase.
• This process is mediated by an HIF2α-dependent transcriptional program, upregulating cell-cycle proteins like CDK1.
• PHD inhibitors mimic HIF2α-dependent cell cycle entry.
• TAMs in lung cancers show transcriptomic evidence of hypoxia response and cell cycle progression.

Conclusions:

• Hypoxia promotes macrophage cell cycle entry via HIF2α, impacting their function.
• The findings suggest a role for hypoxia-driven macrophage proliferation in inflammation and tumor progression.
• This research highlights potential therapeutic targets related to oxygen sensing and cell cycle regulation in cancer.