title: Truncated somatostatin receptor 5 may modulate therapy response to somatostatin analogues--Observations in two patients with acromegaly and severe headache.
abstract: BACKGROUND
  Somatotropinomas have unique "fingerprints" of somatostatin receptor (sst) expression, which are targets in treatment of acromegaly with somatostatin analogues (SSAs). However, a significant expression of sst is not always related to the biochemical response to SSAs. Headache is a common complaint in acromegaly and considered a clinical marker of disease activity. SSAs are reported to have an own analgesic effect, but the sst involved are unknown.
  
  
  METHODS
  We investigated sst expression in two acromegalic patients with severe headache and no biochemical effects of octreotide, but a good response to pasireotide. We searched the literature for determinants of biochemical and analgesic effects of SSAs in somatotropinomas.
  
  
  RESULTS
  Case 1 had no biochemical or analgesic effects of octreotide, a semi-selective SSA, but a rapid and significant effect of pasireotide, a pan-SSA. Case 2 demonstrated discordance between analgesic and biochemical effects of octreotide, in that headache disappeared, but without biochemical improvement. In contrast, pasireotide normalized insulin-like growth factor 1. Both adenomas were sparsely granulated and had strong membranous expressions of sst2a in 50-75% and sst5 in 75-100% of tumor cells. The truncated sst5 variant TMD4 (sst5TMD4) showed expression in 20-57% of tumor cells.
  
  
  CONCLUSIONS
  A poor biochemical response to octreotide may be associated with tumor expression of a truncated sst5 variant, despite abundant sst2a expression, suggesting an influence from variant sst5 on common sst signaling pathways. Furthermore, unrelated analgesic and biochemical effects of SSAs supported a complex pathogenesis of acromegaly-associated headache. Finally, assessment of truncated sst5 in addition to full length sst could be important for a choice of postoperative SSA treatment in somatotropinomas.
authors.affiliation: Department of Medical Endocrinology, Rigshospitalet, Copenhagen University Hospital, Copenhagen, Denmark.
authors.forename: Djordje
authors.initials: D
authors.lastname: Marina
authors.affiliation: Department of Endocrinology, Skånes University Hospital, Malmö, Sweden.
authors.forename: Pia
authors.initials: P
authors.lastname: Burman
authors.affiliation: Department of Medical Endocrinology, Rigshospitalet, Copenhagen University Hospital, Copenhagen, Denmark.
authors.forename: Marianne
authors.initials: M
authors.lastname: Klose
authors.affiliation: Department of Immunology, Genetics and Pathology, Uppsala University, Uppsala, Sweden.
authors.forename: Olivera
authors.initials: O
authors.lastname: Casar-Borota
authors.affiliation: Department of Cell Biology, Physiology and Immunology, University of Córdoba, Instituto Maimónides de Investigación Biomédica de Córdoba (IMIBIC), Hospital Universitario Reina Sofia, 14014 Córdoba, Spain; CIBER Fisiopatología de la Obesidad y Nutrición (CIBERobn), 14014 Córdoba, Spain.
authors.forename: Raúl M
authors.initials: RM
authors.lastname: Luque
authors.affiliation: Department of Cell Biology, Physiology and Immunology, University of Córdoba, Instituto Maimónides de Investigación Biomédica de Córdoba (IMIBIC), Hospital Universitario Reina Sofia, 14014 Córdoba, Spain; CIBER Fisiopatología de la Obesidad y Nutrición (CIBERobn), 14014 Córdoba, Spain.
authors.forename: Justo P
authors.initials: JP
authors.lastname: Castaño
authors.affiliation: Department of Medical Endocrinology, Rigshospitalet, Copenhagen University Hospital, Copenhagen, Denmark. Electronic address: ufeldt@rh.dk.
authors.forename: Ulla
authors.initials: U
authors.lastname: Feldt-Rasmussen
mesh_terms: D000172:Acromegaly / Q000150:complications / Q000188:drug therapy* / Q000378:metabolism*; D000328:Adult; D005260:Female; D049912:Growth Hormone-Secreting Pituitary Adenoma / Q000150:complications / Q000188:drug therapy / Q000378:metabolism; D006261:Headache / Q000188:drug therapy* / Q000209:etiology / Q000378:metabolism; D019382:Human Growth Hormone / Q000031:analogs & derivatives / Q000627:therapeutic use; D006801:Humans; D015282:Octreotide / Q000627:therapeutic use; D010911:Pituitary Neoplasms / Q000150:complications / Q000188:drug therapy / Q000378:metabolism; D017481:Receptors, Somatostatin / Q000378:metabolism*; D013004:Somatostatin / Q000031:analogs & derivatives* / Q000627:therapeutic use; D055815:Young Adult
chemical_list: D017481:Receptors, Somatostatin; C106140:somatostatin receptor sst2A; D019382:Human Growth Hormone; D013004:Somatostatin; C094573:somatostatin receptor 5; C517782:pasireotide; C406545:pegvisomant; D015282:Octreotide
keywords: Acromegaly; Analgesic effect; Headache; Pasireotide; Somatostatin receptors; Truncated sst5