title: Synergy of topical toll-like receptor 7 agonist with radiation and low-dose cyclophosphamide in a mouse model of cutaneous breast cancer.
abstract: OBJECTIVE
  This study tested the hypothesis that topical Toll-like receptor (TLR) 7 agonist imiquimod promotes antitumor immunity and synergizes with other treatments in a model of skin-involving breast cancer.
  
  
  METHODS
  TSA mouse breast carcinoma cells were injected s.c. into syngeneic mice. Imiquimod 5% or placebo cream was applied topically on the shaved skin overlying tumors three times/wk. In some experiments, local ionizing radiation therapy (RT) was delivered to the tumor in three fractions of 8 Gy, given on consecutive days. Cyclophosphamide was given intraperitoneally (i.p.) in one dose of 2 mg/mouse. Mice were followed for tumor growth and survival.
  
  
  RESULTS
  Treatment with imiquimod significantly inhibited tumor growth, an effect that was associated with increased tumor infiltration by CD11c(+), CD4(+), and CD8(+) cells, and abolished by depletion of CD8(+) cells. Administration of imiquimod in combination with RT enhanced significantly tumor response compared with either treatment alone (P < 0.005), and 11% to 66% of irradiated tumors completely regressed. Importantly, the addition of topical imiquimod also resulted in growth inhibition of a secondary tumor outside of the radiation field. Low-dose cyclophosphamide given before start of treatment with imiquimod and RT further improved tumor inhibition and reduced tumor recurrence. Mice that remained tumor-free rejected a tumorigenic inoculum of TSA cells, showing long-term immunologic memory.
  
  
  CONCLUSIONS
  Topical imiquimod inhibits tumor growth and synergizes with RT. Addition of cyclophosphamide further increases the therapeutic effect and induces protective immunologic memory, suggesting that this combination is a promising strategy for cutaneous breast cancer metastases.
authors.affiliation: Department of Pathology, Radiology, Radiation Oncology, and Medicine, New York University School of Medicine, and NYU Langone Medical Center, New York, New York 10016, USA.
authors.forename: M Zahidunnabi
authors.initials: MZ
authors.lastname: Dewan
authors.forename: Claire
authors.initials: C
authors.lastname: Vanpouille-Box
authors.forename: Noriko
authors.initials: N
authors.lastname: Kawashima
authors.forename: Sara
authors.initials: S
authors.lastname: DiNapoli
authors.forename: James S
authors.initials: JS
authors.lastname: Babb
authors.forename: Silvia C
authors.initials: SC
authors.lastname: Formenti
authors.forename: Sylvia
authors.initials: S
authors.lastname: Adams
authors.forename: Sandra
authors.initials: S
authors.lastname: Demaria
mesh_terms: D000287:Administration, Topical; D000634:Aminoquinolines / Q000008:administration & dosage; D000818:Animals; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000009:adverse effects / Q000494:pharmacology / Q000627:therapeutic use*; D045744:Cell Line, Tumor; D059248:Chemoradiotherapy; D003520:Cyclophosphamide / Q000008:administration & dosage; D016207:Cytokines / Q000378:metabolism; D019583:Dose Fractionation, Radiation; D004357:Drug Synergism; D015395:Histocompatibility Antigens Class I / Q000235:genetics / Q000378:metabolism; D006801:Humans; D000077271:Imiquimod; D007156:Immunologic Memory; D007274:Injections, Intraperitoneal; D018799:Intercellular Adhesion Molecule-1 / Q000235:genetics / Q000378:metabolism; D008198:Lymph Nodes / Q000187:drug effects / Q000276:immunology; D008325:Mammary Neoplasms, Experimental / Q000188:drug therapy* / Q000276:immunology / Q000473:pathology / Q000532:radiotherapy; D008562:Membrane Glycoproteins / Q000819:agonists*; D051379:Mice; D008807:Mice, Inbred BALB C; D009364:Neoplasm Recurrence, Local / Q000517:prevention & control; D009368:Neoplasm Transplantation; D012878:Skin Neoplasms / Q000188:drug therapy* / Q000276:immunology / Q000532:radiotherapy / Q000556:secondary; D013601:T-Lymphocytes / Q000187:drug effects / Q000276:immunology / Q000378:metabolism; D051199:Toll-Like Receptor 7 / Q000819:agonists*; D047368:Tumor Burden / Q000187:drug effects / Q000528:radiation effects
chemical_list: D000634:Aminoquinolines; D016207:Cytokines; D015395:Histocompatibility Antigens Class I; C573420:ICAM1 protein, human; D008562:Membrane Glycoproteins; C477038:Tlr7 protein, mouse; D051199:Toll-Like Receptor 7; D018799:Intercellular Adhesion Molecule-1; D003520:Cyclophosphamide; D000077271:Imiquimod