SF2523: Dual PI3K/BRD4 Inhibitor Blocks Tumor Immunosuppression and Promotes Adaptive Immune Responses in Cancer

Mol Cancer Ther. 2019 Jun;18(6):1036-1044. doi: 10.1158/1535-7163.MCT-18-1206. Epub 2019 Apr 24.


Macrophages (MΘs) are key immune infiltrates in solid tumors and serve as major drivers behind tumor growth, immune suppression, and inhibition of adaptive immune responses in the tumor microenvironment (TME). Bromodomain and extraterminal (BET) protein, BRD4, which binds to acetylated lysine on histone tails, has recently been reported to promote gene transcription of proinflammatory cytokines but has rarely been explored for its role in IL4-driven MΘ transcriptional programming and MΘ-mediated immunosuppression in the TME. Herein, we report that BET bromodomain inhibitor, JQ1, blocks association of BRD4 with promoters of arginase and other IL4-driven MΘ genes, which promote immunosuppression in TME. Pharmacologic inhibition of BRD4 using JQ1 and/or PI3K using dual PI3K/BRD4 inhibitor SF2523 (previously reported by our group as a potent inhibitor to block tumor growth and metastasis in various cancer models) suppresses tumor growth in syngeneic and spontaneous murine cancer models; reduces infiltration of myeloid-derived suppressor cells; blocks polarization of immunosuppressive MΘs; restores CD8+ T-cell activity; and stimulates antitumor immune responses. Finally, our results suggest that BRD4 regulates the immunosuppressive myeloid TME, and BET inhibitors and dual PI3K/BRD4 inhibitors are therapeutic strategies for cancers driven by the MΘ-dependent immunosuppressive TME.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Adaptive Immunity / drug effects*
  • Animals
  • Azepines / pharmacology
  • Azepines / therapeutic use
  • Cell Line, Tumor
  • Cell Polarity / drug effects
  • Disease Models, Animal
  • Female
  • Immune Tolerance / drug effects*
  • Macrophages / immunology
  • Male
  • Mice
  • Mice, Inbred BALB C
  • Mice, Inbred C57BL
  • Mice, Nude
  • Morpholines / pharmacology
  • Morpholines / therapeutic use*
  • Neoplasms / drug therapy*
  • Nuclear Proteins / antagonists & inhibitors*
  • Phosphoinositide-3 Kinase Inhibitors / pharmacology
  • Phosphoinositide-3 Kinase Inhibitors / therapeutic use*
  • Pyrans / pharmacology
  • Pyrans / therapeutic use*
  • Transcription Factors / antagonists & inhibitors*
  • Triazoles / pharmacology
  • Triazoles / therapeutic use
  • Tumor Burden / drug effects
  • Tumor Microenvironment / drug effects
  • Tumor Microenvironment / immunology


  • (+)-JQ1 compound
  • Azepines
  • Brd4 protein, mouse
  • Morpholines
  • Nuclear Proteins
  • Phosphoinositide-3 Kinase Inhibitors
  • Pyrans
  • SF2523
  • Transcription Factors
  • Triazoles