Paclitaxel, interferons and functional reprogramming of tumor-associated macrophages in optimized chemo-immunotherapy

Area of Science:

• Immunology
• Oncology
• Pharmacology

Background:

• Immune checkpoint inhibition (ICI) targeting programmed cell death protein-1 (PD1) is effective in many solid tumors but not "cold" tumors lacking T cell infiltration.
• Metastatic triple-negative breast cancer (TNBC) shows limited response (5-20%) to PD-1 blockade, despite some patients benefiting from chemotherapy-induced PD1 sensitization.
• The mechanisms behind chemotherapy's PD1-sensitizing effect and its limited efficacy in a subset of patients remain unclear.

Purpose of the Study:

• To elucidate the mechanism by which chemotherapy sensitizes "cold" tumors to immune checkpoint inhibition (ICI).
• To investigate the role of paclitaxel, Toll-like receptor 4 (TLR4) signaling, and interferon pathways in mediating chemo-immunotherapy efficacy.
• To identify strategies for enhancing chemo-immunotherapy in metastatic triple-negative breast cancer (TNBC) and other taxane-sensitive cancers.

Main Methods:

• Analysis of paclitaxel-driven Toll-like receptor 4 (TLR4) signaling pathways.
• Investigation of type-1 and type-2 interferon pathway activation in tumor-associated macrophages (TAMs).
• Assessment of M2 to M1 macrophage transition and tumor antigen cross-presentation within the tumor microenvironment (TME).

Main Results:

• Paclitaxel treatment activates TLR4 signaling, leading to type-1 and type-2 interferon pathway activation in TAMs.
• This activation promotes a local M2 to M1 macrophage transition, enhancing tumor antigen cross-presentation.
• The TLR4-activated MyD88-NFκB pathway plays a crucial role in mediating these chemo-immunotherapy effects.

Conclusions:

• Paclitaxel-induced TLR4 signaling and subsequent interferon activation in macrophages are key mechanisms for sensitizing "cold" tumors to ICI.
• This pathway facilitates enhanced tumor antigen presentation and T cell activation, improving anti-tumor immunity.
• Targeting the TLR4-MyD88-NFκB axis offers a promising strategy to enhance chemo-immunotherapy efficacy in TNBC and other taxane-sensitive malignancies.