title: Growth hormone and cancer: GH production and action in glioma?
abstract: The hypersecretion of pituitary growth hormone (GH) is associated with an increased risk of cancer, while reducing pituitary GH signaling reduces this risk. Roles for pituitary GH in cancer are therefore well established. The expression of the GH gene is, however, not confined to the pituitary gland and it is now known to occur in many extrapituitary tissues, in which it has local autocrine or paracrine actions, rather than endocrine function. It is, for instance, expressed in cancers of the prostate, lung, skin, endometrium and colon. The oncogenicity of autocrine GH may also be greater than that induced by endocrine or exogenous GH, as higher concentrations of GHR antagonists are required to inhibit its actions. This may reflect the fact that autocrine GH is thought to act at intracellular receptors directly after synthesis, in compartments not readily accessible to endocrine (or exogenous) GH. The roles and actions of extrapituitary GH in cancer may therefore differ from those of pituitary GH. The possibility that GH may be expressed and act in glioma tumors was therefore examined by immunohistochemistry. These results demonstrate, for the first time, the presence of abundant GH- and GH receptor (GHR-) immunoreactivity in glioma, in which they were co-localized in cytoplasmic but not nuclear compartments. These results demonstrate that glioma differs from most cancers in lacking nuclear GHRs, but GH is nevertheless likely to have autocrine or paracrine actions in the induction and progression of glioma.
authors.affiliation: Brain Tumour North West, School of Pharmacy and Biomedical Sciences, University of Central Lancashire, Preston PR1 2HE, UK. Electronic address: RWLea@Uclan.ac.uk.
authors.forename: Robert W
authors.initials: RW
authors.lastname: Lea
authors.affiliation: Royal Preston Hospital, Preston PR2 9H7, UK.
authors.forename: Timothy
authors.initials: T
authors.lastname: Dawson
authors.affiliation: Department of Physiology, University of Alberta, Edmonton T6G 2H7, Canada.
authors.forename: Carlos G
authors.initials: CG
authors.lastname: Martinez-Moreno
authors.affiliation: Department of Physiology, University of Alberta, Edmonton T6G 2H7, Canada.
authors.forename: Nasra
authors.initials: N
authors.lastname: El-Abry
authors.affiliation: Department of Physiology, University of Alberta, Edmonton T6G 2H7, Canada.
authors.forename: Steve
authors.initials: S
authors.lastname: Harvey
mesh_terms: D001932:Brain Neoplasms / Q000209:etiology*; D005260:Female; D005910:Glioma / Q000209:etiology*; D019382:Human Growth Hormone / Q000009:adverse effects* / Q000378:metabolism; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D010902:Pituitary Gland / Q000378:metabolism*
chemical_list: D019382:Human Growth Hormone
keywords: Cancer; Extrapituitary; Glioma; Growth hormone