Immunohistochemical detection of somatostatin receptor types 1-5 in medullary carcinoma of the thyroid.
BACKGROUND
We have analysed the distribution of the five somatostatin receptors (sst1-5) by immunohistochemistry in a large retrospective series of 51 medullary carcinoma of the thyroid (MCT) specimens and correlated the pattern of sst expression with expression of somatostatin (SRIF) peptide, tumour pathology and clinical outcome.


METHODS
Immunohistochemistry was performed with rabbit polyclonal antipeptide antibodies directed against the extracellular domains or cytoplasmic tail of human (h) sst1-5. SRIF immunoreactivity was investigated in parallel paraffin sections.


RESULTS
Eighty-five percent of the tumours were positive for one or more sst, localized to both tumour cells as well as surrounding peritumoural structures, especially blood vessels. Forty-nine percent of the tumours were positive for sst1, 43% for sst2, 47% for sst3, 4% for sst4, and 57% for sst5. Fifty-one percent of tumours expressed one or two sst subtypes; 33% were positive for three or more sst isoforms. All five sst receptors were detected in only two cases. Tumours expressing octreotide sensitive subtypes (sst2,3,5) accounted for 75% of the series. 50% of the tumours co-expressed SRIF suggesting tumour cell regulation by endogenous SRIF via paracrine/autocrine circuits. There was no correlation between sst1-5 expression and age, sex, tumour size or stage, histological type or clinical outcome. Simultaneous analysis of primary tumour and lymph node metastases revealed a similar pattern of sst immunoreactivity indicating that sst expression is not modified in the course of disease progression.


CONCLUSIONS
With the exception of sst4, medullary carcinoma of the thyroid display a rich but heterogeneous expression of sst subtypes. Immunohistochemical typing of sst receptor expression using specific antireceptor antibodies represents an ideal approach for characterizing sst subtype expression in medullary carcinoma of the thyroid for optimizing receptor targeted diagnosis and therapy with somatostatin analogs.
Papotti
M
M
Department of Biomedical Sciences and Oncology, University of Turin, Italy.
Kumar
U
U
Volante
M
M
Pecchioni
C
C
Patel
Y C
YC
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D018276:Carcinoma, Medullary / Q000737:chemistry* / Q000473:pathology; D016009:Chi-Square Distribution; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008875:Middle Aged; D017481:Receptors, Somatostatin / Q000032:analysis*; D012189:Retrospective Studies; D013004:Somatostatin / Q000032:analysis; D013961:Thyroid Gland / Q000737:chemistry; D013964:Thyroid Neoplasms / Q000737:chemistry* / Q000473:pathology; D016896:Treatment Outcome
D017481:Receptors, Somatostatin; C103631:somatostatin receptor 3; C101130:somatostatin receptor type 1; D013004:Somatostatin; C094573:somatostatin receptor 5; C093733:somatostatin receptor 2