Blocking M2-like macrophage polarization using decoy oligodeoxynucleotide-based gene therapy prevents immune evasion for pancreatic cancer treatment.

ABSTRACT

M2-like macrophages exhibit immunosuppressive activity and promote pancreatic cancer progression. Reactive oxygen species (ROS) affect macrophage polarization; however, the mechanism remains unclear. This study aimed to elucidate the underlying molecular basis and design a gene therapy to inhibit M2-like polarization. Microarray analysis and IF staining were performed in M1-like and M2-like macrophages to ascertain the expression of CYBB, a major intracellular ROS source. Co-culture assay and syngeneic orthotopic pancreatic cancer mouse models were used to study the mechanism of M2-like skewing. Decoy oligodeoxynucleotides (ODNs) were designed to manipulate CYBB transcription to inhibit M2-like polarization and control tumor growth. Lipopolysaccharide (LPS) treatment polarized U937 cells to M1-like macrophages in which CYBB expression was increased. In contrast, co-culture with PANC-1 cells induced M2-like polarization in U937 cells with CYBB downregulation. High CD204 M2-like expression in combination with low CYBB expression was associated with the worst prognosis in pancreatic cancer patients. STAT6 and HDAC2 in U937 cells were activated by cancer cell-derived IL-4 after coculture and then bound to the CYBB promoter to repress CYBB expression, resulting in M2-like polarization. DPI that inhibits ROS production could block this action. Knockdown of STAT6 and HDAC2 also inhibited M2-like polarization and maintained the M1-like phenotype of U937 cells after coculture. Decoy ODNs interrupting the binding of STAT6 to the CYBB promoter counteracted M2-like polarization and tumor growth and triggered antitumor immunity in vivo. Gene therapy using STAT6-CYBB decoy ODNs can inhibit M2-like polarization, representing a potential therapeutic tool for pancreatic cancer.