NAMPT-Driven M2 Polarization of Tumor-Associated Macrophages Leads to an Immunosuppressive Microenvironment in...

Area of Science:

• Immunology
• Oncology
• Metabolic enzymes

Background:

• Nicotinamide phosphoribosyltransferase (NAMPT) is crucial in inflammation, but its role in colorectal cancer (CRC) tumor microenvironment (TME) cells is understudied.
• NAMPT is highly expressed in immunosuppressive SPP1+ tumor-associated macrophages (TAMs) in CRC.
• A NAMPThigh gene signature in these TAMs correlates with poor patient prognosis.

Purpose of the Study:

• To investigate the role of NAMPT in myeloid cells during colorectal cancer development.
• To explore the impact of NAMPT deficiency on TAM polarization and function.
• To assess the therapeutic potential of targeting NAMPT in CRC.

Main Methods:

• Single-cell RNA sequencing (scRNA-seq) analysis of CRC TME.
• Genetic deletion of Nampt in the myeloid compartment of mice during CRC.
• Assessment of macrophage polarization, efferocytosis, and immune signaling pathways (HIF-1α, STING, type I IFN).
• Analysis of cytotoxic T cell activity in the TME.

Main Results:

• NAMPT deficiency in macrophages destabilized HIF-1α, reducing M2-like TAM polarization.
• Macrophage NAMPT deficiency decreased efferocytosis, enhancing STING signaling and type I IFN responses.
• These immune responses promoted anti-tumoral immunity by potentiating cytotoxic T cell activity.

Conclusions:

• NAMPT expression in SPP1+ TAMs predicts poor CRC outcomes.
• Targeting NAMPT in TAMs can reprogram the TME towards an immunostimulatory state.
• Strategies targeting NAMPT offer a potential therapeutic avenue for CRC treatment.