title: A role of ghrelin in canine mammary carcinoma cells proliferation, apoptosis and migration.
abstract: BACKGROUND
  Ghrelin is a natural ligand of the growth hormone secretagogue receptor (GHS-R). They are often co-expressed in multiple human tumors and related cancer cell lines what can indicate that the ghrelin/GHS-R axis may have an important role in tumor growth and progression. However, a role of ghrelin in canine tumors remains unknown. Thus, the aim of our study was two-fold: (1) to assess expression of ghrelin and its receptor in canine mammary cancer and (2) to examine the effect of ghrelin on carcinoma cells proliferation, apoptosis, migration and invasion. The expression of ghrelin and its receptor in canine mammary cancer tissues and cell lines (isolated from primary tumors and their metastases) was examined using Real-time qPCR and immunohistochemistry. For apoptosis analysis the Annexin V and propidium iodide dual staining was applied whereas cell proliferation was evaluated by MTT assay and BrdU incorporation test. The influence of ghrelin on cancer cells migration and invasion was assessed using Boyden chamber assays and wound healing assay.
  
  
  RESULTS
  The highest expression of ghrelin was observed in metastatic cancers whereas the lowest expression of ghrelin receptor was detected in tumors of the 3rd grade of malignancy. Higher expression of ghrelin and its receptor was detected in cancer cell lines isolated from metastases than in cell lines isolated from primary tumors. In vitro experiments demonstrated that exposure to low doses of ghrelin stimulates cellular proliferation, inhibits apoptosis and promotes motility and invasion of canine mammary cancer cells. Growth hormone secretagogue receptor inhibitor ([D-Lys3]-GHRP6) as well as RNA interference enhances early apoptosis.
  
  
  CONCLUSIONS
  The presence of ghrelin and GHS-R in all of the examined canine mammary tumors may indicate their biological role in cancer growth and development. Our experiments conducted in vitro confirmed that ghrelin promotes cancer development and metastasis.
authors.affiliation: Department of Physiological Sciences, Faculty of Veterinary Medicine, Warsaw University of Life Sciences - WULS, Nowoursynowska 159, Warsaw, 02-776, Poland.
authors.forename: Kinga
authors.initials: K
authors.lastname: Majchrzak
authors.forename: Karol M
authors.initials: KM
authors.lastname: Pawłowski
authors.forename: Emilia J
authors.initials: EJ
authors.lastname: Orzechowska
authors.forename: Izabella
authors.initials: I
authors.lastname: Dolka
authors.forename: Joanna
authors.initials: J
authors.lastname: Mucha
authors.forename: Tomasz
authors.initials: T
authors.lastname: Motyl
authors.forename: Magdalena
authors.initials: M
authors.lastname: Król
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D002277:Carcinoma / Q000378:metabolism*; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000502:physiology*; D049109:Cell Proliferation; D004283:Dog Diseases / Q000378:metabolism*; D004285:Dogs; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000502:physiology; D054439:Ghrelin / Q000235:genetics / Q000378:metabolism*; D015674:Mammary Neoplasms, Animal / Q000378:metabolism*; D034622:RNA Interference; D034741:RNA, Small Interfering; D060888:Real-Time Polymerase Chain Reaction; D054440:Receptors, Ghrelin / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism
chemical_list: D054439:Ghrelin; D034741:RNA, Small Interfering; D054440:Receptors, Ghrelin