Blocking Interleukin (IL)4- and IL13-Mediated Phosphorylation of STAT6 (Tyr641) Decreases M2 Polarization of Macrophages and Protects Against Macrophage-Mediated Radioresistance of Inflammatory Breast Cancer

Int J Radiat Oncol Biol Phys. 2018 Mar 15;100(4):1034-1043. doi: 10.1016/j.ijrobp.2017.11.043. Epub 2017 Dec 7.


Purpose: To determine the role of macrophage polarization on the response of inflammatory breast cancer (IBC) cells to radiation and whether modulation of macrophage plasticity can alter radiation response.

Methods and materials: The human THP-1 monocyte cell line and primary human monocytes isolated from peripheral blood mononuclear cells were differentiated into macrophages and polarized to either an "antitumor" (M1) or a "protumor" (M2) phenotype. These polarized macrophages were co-cultured with IBC cells (SUM149, KPL4, MDA-IBC3, or SUM190) without direct contact for 24 hours, then subjected to irradiation (0, 2, 4, or 6 Gy). Interleukin (IL)4/IL13-induced activation of STAT6 signaling was measured by Western blotting of phospho-STAT6 (Tyr641), and expression of M2 polarization gene markers (CD206, fibronectin, and CCL22) was measured by quantitative polymerase chain reaction.

Results: Expression of M2 polarization markers was higher in M2-polarized macrophages after IL4/IL13 treatment than in control (M0) or M1-polarized macrophages. Co-culture of IBC cell lines with M1-polarized THP-1 macrophages mediated radiosensitivity of IBC cells, whereas co-culture with M2-polarized macrophages mediated radioresistance. Phosphopeptide mimetic PM37, targeting the SH2 domain of STAT6, prevented and reversed IL4/IL13-mediated STAT6 phosphorylation (Tyr641) and decreased the expression of M2 polarization markers. Pretreatment of M2-THP1 macrophages with PM37 reduced the radioresistance they induced in IBC cells after co-culture. Targeted proteomics analysis of IBC KPL4 cells using a kinase antibody array revealed induction of protein kinase C zeta (PRKCZ) in these cells only after co-culture with M2-THP1 macrophages, which was prevented by PM37 pretreatment. KPL4 cells with stable short hairpin RNA knockdown of PRKCZ exhibited lower radioresistance after M2-THP1 co-culture.

Conclusions: These data suggest that inhibition of M2 polarization of macrophages by PM37 can prevent radioresistance of IBC by down-regulating PRKCZ.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Biomimetic Materials / pharmacology
  • Cell Line, Tumor
  • Cell Polarity / drug effects*
  • Cell Polarity / physiology
  • Chemokine CCL22 / genetics
  • Chemokine CCL22 / metabolism
  • Coculture Techniques / methods
  • Enzyme Induction
  • Female
  • Fibronectins / genetics
  • Fibronectins / metabolism
  • Genetic Markers
  • Humans
  • Inflammatory Breast Neoplasms / metabolism
  • Inflammatory Breast Neoplasms / pathology
  • Inflammatory Breast Neoplasms / radiotherapy*
  • Interleukin-13 / antagonists & inhibitors*
  • Interleukin-4 / antagonists & inhibitors*
  • Lectins, C-Type / genetics
  • Lectins, C-Type / metabolism
  • Macrophages / cytology
  • Macrophages / drug effects*
  • Macrophages / physiology
  • Macrophages / radiation effects
  • Mannose Receptor
  • Mannose-Binding Lectins / genetics
  • Mannose-Binding Lectins / metabolism
  • Molecular Mimicry
  • Phenotype
  • Phosphopeptides / pharmacology
  • Phosphorylation / drug effects
  • Protein Kinase C / genetics
  • Protein Kinase C / metabolism*
  • RNA, Small Interfering / genetics
  • Radiation Tolerance*
  • Receptors, Cell Surface / genetics
  • Receptors, Cell Surface / metabolism
  • STAT6 Transcription Factor / antagonists & inhibitors*
  • STAT6 Transcription Factor / metabolism
  • THP-1 Cells
  • Tumor Microenvironment
  • src Homology Domains / drug effects


  • CCL22 protein, human
  • Chemokine CCL22
  • Fibronectins
  • Genetic Markers
  • IL4 protein, human
  • Interleukin-13
  • Lectins, C-Type
  • Mannose Receptor
  • Mannose-Binding Lectins
  • Phosphopeptides
  • RNA, Small Interfering
  • Receptors, Cell Surface
  • STAT6 Transcription Factor
  • STAT6 protein, human
  • Interleukin-4
  • protein kinase C zeta
  • Protein Kinase C