Timing of immune checkpoint blockade shapes anti-tumor immunity via a clock-dependent chemokine axis

Area of Science:

• Immunology
• Chronobiology
• Cancer Research

Background:

• Circadian clocks are known to regulate immune functions.
• The impact of circadian rhythms on the tumor immune microenvironment and cancer immunotherapy efficacy is not well understood.

Purpose of the Study:

• To investigate the role of intrinsic biological clocks in immune cells within the tumor microenvironment.
• To determine how time-of-day influences tumor immune infiltration and the effectiveness of cancer immunotherapy.

Main Methods:

• Utilized mouse models to assess tumor immune infiltration and immunotherapy response at different times of day.
• Investigated the function of dendritic cell and CD8+ T cell clocks.
• Analyzed the expression of Cx3cl1 and the recruitment of CX3CR1+CD8+ T cells.

Main Results:

• Tumor immune infiltration and immunotherapy efficacy demonstrated significant time-of-day variations in mice.
• Intrinsic clocks in dendritic cells and CD8+ T cells were identified as key drivers of these temporal differences.
• Dendritic cell clocks regulate Cx3cl1 expression, which is crucial for recruiting CX3CR1+CD8+ T cells and enhancing immunotherapy outcomes.

Conclusions:

• Circadian clocks in immune cells critically shape the tumor immune microenvironment.
• A novel circadian mechanism for immune cell recruitment to tumors was identified.
• These findings provide mechanistic insights into the clinical observation that treatment timing affects immunotherapy success.