title: BRAF Inhibition Stimulates Melanoma-Associated Macrophages to Drive Tumor Growth.
abstract: OBJECTIVE
  To investigate the roles of melanoma-associated macrophages in melanoma resistance to BRAF inhibitors (BRAFi).
  
  
  METHODS
  An in vitro macrophage and melanoma cell coculture system was used to investigate whether macrophages play a role in melanoma resistance to BRAFi. The effects of macrophages in tumor resistance were examined by proliferation assay, cell death assay, and Western blot analyses. Furthermore, two mouse preclinical models were used to validate whether targeting macrophages can increase the antitumor activity of BRAFi. Finally, the number of macrophages in melanoma tissues was examined by immunohistochemistry.
  
  
  RESULTS
  We demonstrate that in BRAF-mutant melanomas, BRAFi paradoxically activate the mitogen-activated protein kinase (MAPK) pathway in macrophages to produce VEGF, which reactivates the MAPK pathway and stimulates cell growth in melanoma cells. Blocking the MAPK pathway or VEGF signaling then reverses macrophage-mediated resistance. Targeting macrophages increases the antitumor activity of BRAFi in mouse and human tumor models. The presence of macrophages in melanomas predicts early relapse after therapy.
  
  
  CONCLUSIONS
  Our findings demonstrate that macrophages play a critical role in melanoma resistance to BRAFi, suggesting that targeting macrophages will benefit patients with BRAF-mutant melanoma.
authors.affiliation: Molecular and Cellular Oncogenesis Program, The Wistar Institute, Philadelphia, Pennsylvania. tao.wang@fda.hhs.gov HerlynM@wistar.org kaufman@wistar.org.
authors.forename: Tao
authors.initials: T
authors.lastname: Wang
authors.affiliation: Molecular and Cellular Oncogenesis Program, The Wistar Institute, Philadelphia, Pennsylvania.
authors.forename: Min
authors.initials: M
authors.lastname: Xiao
authors.affiliation: Department of Physiology, Nanjing Medical University, Nanjing, China.
authors.forename: Yingbin
authors.initials: Y
authors.lastname: Ge
authors.affiliation: Molecular and Cellular Oncogenesis Program, The Wistar Institute, Philadelphia, Pennsylvania.
authors.forename: Clemens
authors.initials: C
authors.lastname: Krepler
authors.affiliation: Molecular and Cellular Oncogenesis Program, The Wistar Institute, Philadelphia, Pennsylvania.
authors.forename: Eric
authors.initials: E
authors.lastname: Belser
authors.affiliation: Graduate Program, The Catholic University of America, Washington, District of Columbia.
authors.forename: Alfonso
authors.initials: A
authors.lastname: Lopez-Coral
authors.affiliation: Department of Pathology and Laboratory Medicine, University of Pennsylvania, Philadelphia, Pennsylvania.
authors.forename: Xiaowei
authors.initials: X
authors.lastname: Xu
authors.affiliation: Molecular and Cellular Oncogenesis Program, The Wistar Institute, Philadelphia, Pennsylvania.
authors.forename: Gao
authors.initials: G
authors.lastname: Zhang
authors.affiliation: Undergraduate Program, University of Pennsylvania, Philadelphia, Pennsylvania.
authors.forename: Rikka
authors.initials: R
authors.lastname: Azuma
authors.affiliation: Molecular and Cellular Oncogenesis Program, The Wistar Institute, Philadelphia, Pennsylvania.
authors.forename: Qin
authors.initials: Q
authors.lastname: Liu
authors.affiliation: Undergraduate Program, University of Pennsylvania, Philadelphia, Pennsylvania.
authors.forename: Rui
authors.initials: R
authors.lastname: Liu
authors.affiliation: Molecular and Cellular Oncogenesis Program, The Wistar Institute, Philadelphia, Pennsylvania.
authors.forename: Ling
authors.initials: L
authors.lastname: Li
authors.affiliation: Department of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania. Abramson Cancer Center, University of Pennsylvania, Philadelphia, Pennsylvania.
authors.forename: Ravi K
authors.initials: RK
authors.lastname: Amaravadi
authors.affiliation: Abramson Cancer Center, University of Pennsylvania, Philadelphia, Pennsylvania.
authors.forename: Wei
authors.initials: W
authors.lastname: Xu
authors.affiliation: Abramson Cancer Center, University of Pennsylvania, Philadelphia, Pennsylvania. Department of Surgery, University of Pennsylvania, Philadelphia, Pennsylvania.
authors.forename: Giorgos
authors.initials: G
authors.lastname: Karakousis
authors.affiliation: Department of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania. Abramson Cancer Center, University of Pennsylvania, Philadelphia, Pennsylvania.
authors.forename: Tara C
authors.initials: TC
authors.lastname: Gangadhar
authors.affiliation: Department of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania. Abramson Cancer Center, University of Pennsylvania, Philadelphia, Pennsylvania.
authors.forename: Lynn M
authors.initials: LM
authors.lastname: Schuchter
authors.affiliation: Undergraduate Program, University of the Sciences, Philadelphia, Pennsylvania.
authors.forename: Melissa
authors.initials: M
authors.lastname: Lieu
authors.affiliation: Biotechnology School of Engineering and Applied Sciences, University of Pennsylvania, Philadelphia, Pennsylvania.
authors.forename: Sanika
authors.initials: S
authors.lastname: Khare
authors.affiliation: Molecular and Cellular Oncogenesis Program, The Wistar Institute, Philadelphia, Pennsylvania.
authors.forename: Molly B
authors.initials: MB
authors.lastname: Halloran
authors.affiliation: Molecular and Cellular Oncogenesis Program, The Wistar Institute, Philadelphia, Pennsylvania. tao.wang@fda.hhs.gov HerlynM@wistar.org kaufman@wistar.org.
authors.forename: Meenhard
authors.initials: M
authors.lastname: Herlyn
authors.affiliation: Molecular and Cellular Oncogenesis Program, The Wistar Institute, Philadelphia, Pennsylvania. tao.wang@fda.hhs.gov HerlynM@wistar.org kaufman@wistar.org.
authors.forename: Russel E
authors.initials: RE
authors.lastname: Kaufman
mesh_terms: D000818:Animals; D015153:Blotting, Western; D018920:Coculture Techniques; D019008:Drug Resistance, Neoplasm / Q000276:immunology*; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D015151:Immunoblotting; D007150:Immunohistochemistry; D008264:Macrophages / Q000187:drug effects / Q000276:immunology / Q000378:metabolism*; D008545:Melanoma / Q000276:immunology / Q000473:pathology*; D051379:Mice; D008807:Mice, Inbred BALB C; D058990:Molecular Targeted Therapy / Q000009:adverse effects; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D048493:Proto-Oncogene Proteins B-raf / Q000037:antagonists & inhibitors*; D034741:RNA, Small Interfering; D015398:Signal Transduction / Q000187:drug effects*; D014162:Transfection; D059016:Tumor Microenvironment / Q000276:immunology; D023041:Xenograft Model Antitumor Assays
chemical_list: D047428:Protein Kinase Inhibitors; D034741:RNA, Small Interfering; D048493:Proto-Oncogene Proteins B-raf