title: Impact of CTLA-4 blockade in conjunction with metronomic chemotherapy on preclinical breast cancer growth.
abstract: Although there are reports that metronomic cyclophosphamide (CTX) can be immune stimulating, the impact of its combination with anti-CTLA-4 immunotherapy for the treatment of cancer remains to be evaluated.
  
  
  
  Murine EMT-6/P breast cancer, or its cisplatin or CTX-resistant variants, or CT-26 colon, were implanted into Balb/c mice. Established tumours were monitored for relative growth following treatment with anti-CTLA-4 antibody alone or in combination with; (a) metronomic CTX (ldCTX; 20 mg kg-1day-1), b) bolus (150 mg kg-1) plus ldCTX, or (c) sequential treatment with gemcitabine (160 mg kg-1every 3 days).
  
  
  
  EMT-6/P tumours responded to anti-CTLA-4 therapy, but this response was less effective when combined with bolus plus ldCTX. Anti-CTLA-4 could be effectively combined with either ldCTX (without a bolus), or with regimens of either sequential or concomitant gemcitabine, including in orthotopic EMT-6 tumours, and independently of the schedule of drug administration. Tumour responses were confirmed with CT-26 tumours but were less pronounced in drug-resistant EMT-6/CTX or EMT-6/DDP tumour models than in the parent tumour. A number of tumour bearing mice developed spontaneous metastases under continuous therapy. The majority of cured mice rejected tumour re-challenges.
  
  
  
  Metronomic CTX can be combined with anti-CTLA-4 therapy, but this therapy is impaired by concomitant bolus CTX. Sequential therapy of anti-CTLA-4 followed by gemcitabine is effective in chemotherapy-naive tumours, although tumour relapses can occur, in some cases accompanied by the development of spontaneous metastases.
authors.affiliation: Department of Biological Sciences, University of Texas at El Paso (UTEP), El Paso, TX, USA.
authors.forename: Karla
authors.initials: K
authors.lastname: Parra
authors.affiliation: Department of Biological Sciences, University of Texas at El Paso (UTEP), El Paso, TX, USA.
authors.forename: Paloma
authors.initials: P
authors.lastname: Valenzuela
authors.affiliation: Department of Biological Sciences, University of Texas at El Paso (UTEP), El Paso, TX, USA.
authors.forename: Natzidielly
authors.initials: N
authors.lastname: Lerma
authors.affiliation: Department of Biological Sciences, University of Texas at El Paso (UTEP), El Paso, TX, USA.
authors.forename: Alejandra
authors.initials: A
authors.lastname: Gallegos
authors.affiliation: Department of Biological Sciences, University of Texas at El Paso (UTEP), El Paso, TX, USA.
authors.forename: Luis C
authors.initials: LC
authors.lastname: Reza
authors.affiliation: Department of Biological Sciences, University of Texas at El Paso (UTEP), El Paso, TX, USA.
authors.forename: Georgialina
authors.initials: G
authors.lastname: Rodriguez
authors.affiliation: Odette Cancer Centre, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Canada.
authors.forename: Urban
authors.initials: U
authors.lastname: Emmenegger
authors.affiliation: Division of Pharmacology, Department of Clinical and Experimental Medicine, University of Pisa, Pisa, Italy.
authors.forename: Teresa
authors.initials: T
authors.lastname: Di Desidero
authors.affiliation: Division of Pharmacology, Department of Clinical and Experimental Medicine, University of Pisa, Pisa, Italy.
authors.forename: Guido
authors.initials: G
authors.lastname: Bocci
authors.affiliation: William Beaumont Army Medical Center, Department of Neurology, El Paso, TX, USA.
authors.forename: Mitchell S
authors.initials: MS
authors.lastname: Felder
authors.affiliation: Department of Physics, UTEP, TX, USA.
authors.forename: Marian
authors.initials: M
authors.lastname: Manciu
authors.affiliation: Department of Biological Sciences, University of Texas at El Paso (UTEP), El Paso, TX, USA.
authors.forename: Robert A
authors.initials: RA
authors.lastname: Kirken
authors.affiliation: Department of Biological Sciences, University of Texas at El Paso (UTEP), El Paso, TX, USA.
authors.forename: Giulio
authors.initials: G
authors.lastname: Francia
mesh_terms: D059250:Administration, Metronomic; D000818:Animals; D000911:Antibodies, Monoclonal / Q000008:administration & dosage*; D018906:Antineoplastic Agents, Alkylating / Q000008:administration & dosage*; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use*; D060908:CTLA-4 Antigen / Q000037:antagonists & inhibitors / Q000276:immunology; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects*; D003520:Cyclophosphamide / Q000008:administration & dosage*; D004354:Drug Screening Assays, Antitumor; D005260:Female; D000074324:Ipilimumab; D008325:Mammary Neoplasms, Experimental / Q000188:drug therapy* / Q000473:pathology; D051379:Mice; D008807:Mice, Inbred BALB C; D009368:Neoplasm Transplantation
chemical_list: D000911:Antibodies, Monoclonal; D018906:Antineoplastic Agents, Alkylating; D060908:CTLA-4 Antigen; D000074324:Ipilimumab; D003520:Cyclophosphamide