5-aza-2'-deoxycytidine potentiates anti-tumor immunity in colorectal peritoneal metastasis by modulating ABC A9-mediated cholesterol accumulation in macrophages

Theranostics. 2022 Jan 1;12(2):875-890. doi: 10.7150/thno.66420. eCollection 2022.

Abstract

Background: 5-aza-2'-deoxycytidine (5Aza), a DNA methyltransferase (DNMT) inhibitor, could activate tumor adaptive immunity to inhibit tumor progression. However, the molecular mechanisms by which 5Aza regulates tumor immune microenvironment are still not fully understood. Methods: The role of 5Aza in immune microenvironment of peritoneal carcinomatosis (PC) of colorectal cancer (CRC) was investigated. The effects of 5Aza on macrophage activation were studied by flow cytometry, real-time PCR, Western blotting assays, and Drug Affinity Responsive Target Stability (DARTS). The effects of 5Aza on tumor immunity were validated in stromal macrophages and T cells from CRC patients. Results: 5Aza could stimulate the activation of macrophages toward an M1-like phenotype and subsequent activation of T cells in premetastatic fat tissues, and ultimately suppress CRC-PC in immune-competent mouse models. Mechanistically, 5Aza stimulated primary mouse macrophages toward to a M1-like phenotype characterized by the increase of p65 phosphorylation and IL-6 expression. Furthermore, we screened and identified ATP-binding cassette transporter A9 (ABC A9) as a binding target of 5Aza. 5Aza induced cholesterol accumulation, p65 phosphorylation and IL-6 expression in an ABC A9-dependent manner. Pharmacological inhibition of NF-κB, or genetic depletion of IL-6 abolished the antitumor effect of 5Aza in mice. In addition, the antitumor effect of 5Aza was synergistically potentiated by conventional chemotherapeutic drugs 5-Fu or OXP. Finally, we validated the reprogramming role of 5Aza in antitumor immunity in stromal macrophages and T cells from CRC patients. Conclusions: Taken together, our findings showed for the first time that 5Aza suppressed CRC-PC by regulating macrophage-dependent T cell activation in premetastatic microenvironment, meanwhile uncovered a DNA methylation-independent mechanism of 5Aza in regulating ABC A9-associated cholesterol metabolism and macrophage activation.

Keywords: 5Aza; ABC A9; CRC-PC; IL-6; macrophages.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antimetabolites, Antineoplastic / pharmacology*
  • Cholesterol / metabolism*
  • Colorectal Neoplasms / drug therapy
  • Colorectal Neoplasms / immunology*
  • Colorectal Neoplasms / metabolism
  • Colorectal Neoplasms / pathology
  • DNA Modification Methylases / antagonists & inhibitors
  • Decitabine / pharmacology*
  • Enzyme Inhibitors / pharmacology
  • Humans
  • Macrophages, Peritoneal / drug effects*
  • Macrophages, Peritoneal / metabolism
  • Male
  • Mice
  • Mice, Inbred BALB C
  • Mice, Inbred C57BL
  • Neoplasm Metastasis / immunology*
  • Peritoneal Neoplasms / diet therapy
  • Peritoneal Neoplasms / immunology*
  • Peritoneal Neoplasms / metabolism
  • Peritoneal Neoplasms / secondary
  • Tumor Microenvironment / drug effects
  • Tumor Microenvironment / immunology

Substances

  • Antimetabolites, Antineoplastic
  • Enzyme Inhibitors
  • Decitabine
  • Cholesterol
  • DNA Modification Methylases