The immunohistochemical localisation of somatostatin receptors 1, 2, 3, and 5 in acoustic neuromas

Ga-68 DOTATATE PET/CT in the Evaluation of Paragangliomas and Other Indeterminate Lesions in the Head and Neck

Background and Purpose

Paragangliomas (PGLs) are rare neuroendocrine tumors with imaging features that can overlap with other entities. This study hypothesizes that given overexpression of somatostatin receptor (SSTR) 2, PGLs can be differentiated on Ga-68 DOTATATE positron emission tomography/computed tomography (PET/CT) from other benign or malignant lesions.

Materials and Methods

Ninety-six patients with known tumors of the head and neck who underwent Ga-68 DOTATATE PET/CT from May 2017 to December 2021 were retrospectively reviewed from a single institution. Of these, 43 patients had histopathological confirmation and 66 positive lesions were discovered on PET/CT. For each lesion, the SUV max, the SUV lesion to liver ratio, and the SUV lesion to spleen ratio were analyzed.

Results

PGLs (n = 37) showed the most intense uptake, and the mean of SUVmax was 69.3 (range 3.7-225.9). Metastatic PGL and metastasis from other neuroendocrine tumors (n = 13) demonstrated intermediate uptake, the mean of SUVmax was 15.16 (range 2.3-40.3). Meningiomas (n = 3) had intermediate uptake, and the mean of SUVmax was 12.37 (range 2.5-19.4). One patient with esthesioneuroblastoma had 5 lesions in the head and neck, and the mean of SUVmax was 18.9 (range 6.9-49.4). Schwannomas (n = 4) had very low uptake, and the mean of SUVmax was 1.75 (range 1.1-2.2). Other rare cases with low uptake included 1 each of osteosarcoma, acinic cell carcinoma, ectopic thyroid tissue, and plasmacytoma, and the mean of SUVmax was 4.75 (range 2.3-6.1).

Conclusions

Ga-68 DOTATATE PET/CT can be a useful adjunct in differentiating tumors in the head and neck. PGLs demonstrate the highest uptake. Meningioma, esthesioneuroblastoma, and neuroendocrine tumor metastasis have intermediate uptake. Schwannomas and other rare tumors exhibit low uptake.

68Ga-DOTATATE Uptake in an Endolymphatic Sac Tumor: Radiologic-Pathologic Correlation

After dedicated CT and MRI, Ga-DOTATATE PET/CT was performed in a patient with a temporal bone mass with primary diagnostic considerations of an endolymphatic sac tumor versus a glomus jugulotympanicum paraganglioma. The Ga-DOTATATE PET showed mild radiotracer uptake in the mass (SUVmax, 10.9). After surgical resection, pathology revealed an endolymphatic sac tumor. Immunohistochemical staining demonstrated somatostatin receptor type 2A expression in the vasculature of the mass, but not in the tumor cells.

Evaluation of expression of somatostatin receptor 1, 2, 3, 5 and dopamine D2 receptor in spindle cell oncocytomas of posterior pituitary

PURPOSE

Spindle cell oncocytomas (SCOs) are very rare tumors of the posterior pituitary with potential for locally aggressive behaviour. Their treatment includes surgery and possibly radiotherapy, however other options are lacking. Somatostatin receptors (SSTs) are a possible therapeutic target for somatostatin analogues and their expression has been demonstrated recently in closely related pituicytomas, but there are no data about their presence in SCOs.

METHODS

We collected five cases of SCO from four patients including one recurrent case. Immunohistochemical detection of TTF1, GFAP, CD68, SST₁, SST₂, SST₃, SST₅ and D2 dopamine receptor (D2DR) was performed. Intensity, percentage of positive cells and pattern of expression was evaluated in semiquantitative fashion. Protein expression of SST_1-5 and D2DR was further evaluated by western blot.

RESULTS

Mean patient age was 61.8 years (range 47-71 years) with male to female ratio 1:1. In one patient, samples from the original tumor and its recurrence 16 years later were assessed. TTF1 was positive in all five cases, no expression of GFAP and CD68 was seen. Immunohistochemical expression of SST₁ was noted in 1/5 cases, SST₂ in 2/5 cases, including recurrent case but not the original case. SST₃ was expressed in 3/5 tumors and D2 dopamine receptor in 4/5 cases. Western blot was successfully performed in four samples. SST₂, SST₃ and D2DR expression was identified in all the samples, including two cases originally negative for SST₂ and one case negative for SST₃ by immunohistochemistry. The number of positive cells and level of expression varied among different areas of the same tumors. No expression of SST₅ was observed. In the patient with the recurrent tumor, intensity of SST₂, SST₃ and D2DR expression varied between original tumor and its recurrence.

CONCLUSIONS

We demonstrated presence of different SST subtypes and D2DR in spindle cell oncocytomas. The most commonly expressed subtype was SST₂ and SST₃, while no expression of SST₅ was observed. Expression showed spatial heterogeneity and temporal changes as seen in the recurrent case. The biological meaning of SSTs expression in SCOs is unclear as well as whether it may be exploited in treatment of selected cases.

Expression of estrogen and progesterone receptors in vestibular schwannomas and their clinical significance

Objective

The objective was to determine the expression of estrogen and progesterone receptors in vestibular schwannomas as well as to determine predictive factors for estrogen and progesterone receptor positivity.

Materials and methods

The study included 100 cases of vestibular schwannomas operated from January 2006 to June 2009. The clinical details were noted from the medical case files. Formaldehyde-fixed parafiin-embedded archival vestibular schwannomas specimens were used for the immunohistochemical assessment of estrogen and progesterone receptors.

Results

Neither estrogen nor progesterone receptors could be detected in any of our cases by means of well known immunohistochemical method using well documented monoclonal antibodies. In the control specimens, a strongly positive reaction could be seen.

Conclusion

No estrogen and progesterone receptor could be found in any of our 100 cases of vestibular schwannomas. Hence our study does not support a causative role of estrogen and progesterone in the growth of vestibular schwannoma as well as hormonal manipulation in the treatment of this tumor.

Expression of somatostatin and somatostatin receptor subtypes 1-5 in human normal and diseased kidney

Somatostatin mediates inhibitory functions through five G protein-coupled somatostatin receptors (sst1-5). We used immunohistochemistry, immunofluorescence, and RT-PCR to determine the presence of somatostatin receptors sst1, sst2A, sst2B, sst3, sst4, and sst5 in normal and IgA nephropathy human kidney. All somatostatin receptors were detected in the thin tubules (distal convoluted tubules and loops of Henle) and thick tubules (proximal convoluted tubules) in the tissue sections from nephrectomy and biopsy samples. Immunopositive sst1 and sst4 staining was more condensed in the cytoplasm of tubular epithelial cells. In normal kidney tissue sections, podocytes and mesangial cells in the glomeruli stained for sst1, sst2B, sst4 and sst5, and stained weakly for sst3. In IgA kidney tissue, the expression of somatostatin receptors was significantly increased with particular immmunopositive staining for sst1, sst2B, sst4, and sst5 within glomeruli. In the epithelial cells, the staining for sst2B and sst4 in proximal tubules and sst1, sst2B, and sst5 in distal tubules was increased. The mRNA expression of sst1-5 was also detected by RT-PCR. Somatostatin and all five receptor subtypes were ubiquitously distributed in normal kidney and IgA nephropathy. The increased expression of somatostatin receptors in IgA nephropathy kidney might be the potential pathogenesis of inflammatory renal disease.

Somatostatin receptor profiling in hepatic metastases from small intestinal and pancreatic neuroendocrine neoplasms: immunohistochemical approach with potential clinical utility

BACKGROUND

The expression of somatostatin receptors (SSTRs) on endocrine tumor (ET) cells forms the basis for somatostatin analog treatment of patients with SSTR-positive, hormonally active ETs. In patients with SSTR-negative ETs, the clinical response is generally absent or suboptimal, while nonfunctioning ETs with SSTR positivity show a variable response to such therapy.

METHODS

We retrospectively studied SSTR subtype expression in hepatic metastases from 14 adult patients with primary endocrine carcinomas (ECAs) of the small intestine and pancreas and compared SSTR subtype expression among the primary and metastatic ECAs. Polyclonal antibodies against the 5 SSTR subtypes were used on formalin-fixed, paraffin sections from each primary and metastatic ECA. Both qualitative and semiquantitative evaluation of the stained ECA sections was carried out.

RESULTS

Eleven (61%) of 18 hepatic metastases from small intestinal and pancreatic ECAs were positive for SSTR-1, 15 (83%) for SSTR-2, 13 (72%) for SSTR-3, 10 (56%) for SSTR-4, and 15 (83%) for SSTR-5. Among 11 hepatic ECA metastases from small intestinal ECAs (carcinoids), 7 (63%) expressed SSTR-1, 9 (81%) expressed SSTR-2, 8 (72%) expressed SSTR-3, 6 (54%) expressed SSTR-4, and 10 (91%) expressed SSTR-5. Of 7 hepatic ECA metastases from pancreatic ECAs, 4 expressed SSTR-1, 6 expressed SSTR-2, and 5 expressed SSTR-3 and SSTR-5 each. We also observed the immunohistochemical evidence of heterogeneity of expression of various SSTR subtypes in the primary enteropancreatic ECAs and their hepatic metastases.

CONCLUSIONS

SSTR subtype expression needs to be correlated to somatostatin analog therapy. Immunohistochemical profiling of various SSTR subtypes as a part of routine surgical pathologic analysis of enteropancreatic ETs may become a useful predictor of responsiveness of ETs to various SSTR analogs.

Expression and Function of Somatostatin Receptors in Peripheral Nerve Sheath Tumors

Although somatostatin receptors have been detected in many normal and neoplastic tissues, little is known of their expression and function in peripheral nerve tumors. In the present study, we examined the expression of all 5 somatostatin receptor subtypes (sst1-5) in 3 normal peripheral nerves, 3 traumatic neuromas, 27 schwannomas, 18 neurofibromas, and 177 malignant peripheral nerve sheath tumors (MPNSTs) by immunohistochemistry as well as by Western blot and reverse transcriptase-polymerase chain reaction investigations in 2 normal peripheral nerves, one neurofibroma, 5 schwannomas, and 5 MPNSTs. Immunoreactive somatostatin receptors were not detectable in normal peripheral nerve and in nonneoplastic Schwann cell proliferations. In contrast, sst2A mRNA and protein was present in 89% of schwannomas. This receptor subtype was less frequently detected in neurofibromas (22%) and MPNSTs (15%). Interestingly, sst4 was seen in 32% of MPNSTs and was almost exclusively expressed in this malignant tumor type. In support of a role in Schwann cell tumor growth control by somatostatin was the observation of induced internalization of sst2A and inhibition of cell proliferation in an NF1-associated MPNST cell line. Moreover, administration of an sst2A-selective agonist resulted in induction of MPNST cell apoptosis. We conclude that peripheral nerve sheath tumors often express at least one functional somatostatin receptor. Furthermore, our findings suggest a potential clinical role for somatostatin receptor agonists in tumor imaging and/or treatment of schwannomas and MPNSTs.

Somatostatin receptors 2 and 5 are preferentially expressed in proliferating endothelium

Angiogenesis is characterised by activation, migration and proliferation of endothelial cells and is central to the pathology of cancer, cardiovascular disease and chronic inflammation. Somatostatin is an inhibitory polypeptide that acts through five receptors (sst 1, 2, 3, 4, 5). Sst has previously been reported in endothelium, but their role remains obscure. Here, we report the expression of sst in human umbilical vein endothelial cells (HUVECs) in vitro, during proliferation and quiescence. A protocol for culturing proliferating and quiescent HUVECs was established, and verified by analysing cell cycle distribution in propidium-iodide-stained samples using flow cytometry. Sst mRNA was then quantified in nine proliferating and quiescent HUVEC lines using quantitative reverse transcriptase–polymerase chain reaction. Sst 2 and 5 were preferentially expressed in proliferating HUVECs. All samples were negative for sst 4. Sst 1 and 3 expression and cell cycle progression were unrelated. Immunostaining for sst 2 and 5 showed positivity in proliferating but not quiescent cells, confirming sst 2 and 5 protein expression. Inhibition of proliferating cells with somatostatin analogues Octreotide and SOM230, which have sst 5 activity, was found (Octreotide 10⁻¹⁰–10⁻⁶ M: 48.5–70.2% inhibition; SOM230 10⁻⁹–10⁻⁶ M: 44.9–65.4% inhibition) in a dose-dependent manner, suggesting that sst 5 may have functional activity in proliferation. Dynamic changes in sst 2 and 5 expression during the cell cycle and the inhibition of proliferation with specific analogues suggest that these receptors may have a role in angiogenesis.