Expression of somatostatin receptor subtypes in human pituitary adenomas -- immunohistochemical studies.
BACKGROUND
The highly variable expression of SSTR subtypes in pituitary adenomas (PA) may partially explain why the subgroup of somatotropinomas or other adenomas do not respond to the therapeutic action of currently used long-acting somatostatin analogues like octreotide or lanreotide.


METHODS
Our study summarizes the data on expression of all somatostatin receptor subtypes (SSTR 1-5), extended for 2A and 2B SSTR isoforms, revealed by means of immunohistochemistry in dependence to different hormonal phenotype of the tumour.


RESULTS
The pattern of SSTR immunostaining (estimated according to the percentage frequency of appearance) was in acromegaly: SSTR 5 > SSTR 1 > SSTR 2A = SSTR 3 > SSTR 2B, in prolactinomas: SSTR 2B = SSTR 3 = SSTR 5 > SSTR 1 = SSTR 2A, in gonadotropinomas: SSTR 3 > SSTR 2B > SSTR 1 = SSTR 2A > SSTR 5, in corticotropinomas: SSTR 2A > SSTR 1 = SSTR 3 > SSTR 5 > SSTR 2B. In PA immunonegative for pituitary hormones, we noticed only a weak staining of all receptor subtypes including SSTR 4. In plurihormonal adenomas with positive GH phenotype the staining pattern was: SSTR 5 > SSTR 1 = SSTR 2B and in plurihormonal PA with negative GH phenotype: SSTR 1 = SSTR 5 > SSTR 2A = SSTR 2B = SSTR 3. In plurihormonal adenoma with ACTH immunopositivity, the staining pattern was: SSTR = SSTR 2A = SSTR 3 = SSTR 5. SSTR 1 and SSTR 5 were the most frequent subtypes of somatostatin receptor in plurihormonal adenomas without ACTH expression.


CONCLUSIONS
Human PA represents a group of tumours with a much more differentiated appearance of somatostatin receptor subtypes. It is very important to determine the SSTR profile individually for each tumour to make an appropriate decision as to therapeutic strategy choice. Apart from applying SSTR 2 and SSTR 5-preferring octreotide and lanreotide - newly synthesized multiligand analogues, such as SOM 230, KE 108, or other SST selective analogues, may represent a further useful approach for the treatment, especially in cases other than somatotropinoma or thyrotropinoma.
Pisarek
Hanna
H
Department of Neuroendocrinology, Chair of Endocrinology, Medical University of Łódź, Poland. h.pisarek@kardio-sterling.lodz.pl
Pawlikowski
Marek
M
Kunert-Radek
Jolanta
J
Radek
Maciej
M
D000236:Adenoma / Q000145:classification / Q000188:drug therapy / Q000378:metabolism*; D000328:Adult; D018931:Antineoplastic Agents, Hormonal / Q000494:pharmacology; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008875:Middle Aged; D015282:Octreotide / Q000494:pharmacology; D010456:Peptides, Cyclic / Q000494:pharmacology; D010641:Phenotype; D010911:Pituitary Neoplasms / Q000145:classification / Q000188:drug therapy / Q000378:metabolism*; D020033:Protein Isoforms; D017481:Receptors, Somatostatin / Q000145:classification / Q000187:drug effects / Q000378:metabolism*; D013004:Somatostatin / Q000031:analogs & derivatives / Q000494:pharmacology; D055815:Young Adult
D018931:Antineoplastic Agents, Hormonal; D010456:Peptides, Cyclic; D020033:Protein Isoforms; D017481:Receptors, Somatostatin; C060347:lanreotide; D013004:Somatostatin; D015282:Octreotide