Correlative immunohistochemical and reverse transcriptase polymerase chainreaction analysis of somatostatin receptor type 2 in neuroendocrine tumorsof the lung
P. Papotti et al., Correlative immunohistochemical and reverse transcriptase polymerase chainreaction analysis of somatostatin receptor type 2 in neuroendocrine tumorsof the lung, DIAGN MOL P, 9(1), 2000, pp. 47-57
Citations number
42
Categorie Soggetti
Research/Laboratory Medicine & Medical Tecnology","Medical Research Diagnosis & Treatment
Somatostatin receptors type 2 (sst2) have been frequently detected in neuro
endocrine tumors and bind somatostatin analogues, such as octreotide, with
high affinity. Receptor autoradiography, specific mRNA detection and, more
recently, anti-sst2 polyclonal antibodies are currently employed to reveal
sst2. The aim of the present study was to investigate by three different te
chniques the presence of sst2 in a series of 26 neuroendocrine tumors of th
e lung in which fresh frozen tissue and paraffin sections were available. I
t was possible, therefore, to compare, in individual cases, RNA analysis st
udied by reverse transcriptase polymerase chain reaction (RT-PCR), in situ
hy bridization (ISH), and immunohistochemistry. A series of 20 nonneuroendo
crine lung carcinoma samples served as controls. RT-PCR was positive for ss
t2 in 22 of 26 samples, including 15 of 15 typical carcinoids, 5 of 6 atypi
cal carcinoids, and 2 of 5 small-cell carcinomas. The sst2 mRNA signal obta
ined by RT-PCR was strong in the majority (87%) of typical carcinoids and o
f variable intensity in atypical carcinoids and small-cell carcinomas. A we
akly positive signal was observed in 5 of 20 control samples. In immunohist
ochemistry, two different antibodies (anti-sst2) were employed, including a
monoclonal antibody, generated in the Department of Pathology, University
of Turin. In the majority of samples a good correlation between sst2 mRNA l
as detected by RT-PCR) and sst2 protein expression las detected by immunohi
stochemistry) was observed. However, one atypical carcinoid and one small-c
ell carcinoma had focal immunostaining but no RT-PCR signal. ISH performed
in selected samples paralleled the results obtained with the other techniqu
es. A low sst2 expression was associated with high grade neuroendocrine tum
ors and with aggressive behavior. It is concluded that 1) neuroendocrine tu
mors of the lungs express sst2, and there is a correlation between the mRNA
amount and the degree of differentiation; 2) immunohistochemistry and ISH
are reliable tools to demonstrate sst2 in these tumors; and 3) sst2 identif
ication in tissue sections may provide information on the diagnostic or the
rapeutic usefulness of somatostatin analogues in individual patients with n
euroendocrine tumors.