The expression of somatostatin receptors 1 and 2 in benign, pre-malignant and malignant laryngeal lesions

Somatostatin receptor2 (SSTR2) expression, prognostic implications, modifications and potential therapeutic strategies associates with head and neck squamous cell carcinomas

Head and neck squamous cell carcinomas (HNSCC) constitute a heterogeneous cluster of tumors celebrated for their predisposition to metastasize and exhibit local recurrence. Recent explorations have illuminated the intricate involvement of Somatostatin Receptor 2 (SSTR2), a growth-regulatory receptor traditionally classified as a tumor suppressor, yet concurrently implicated in bolstering specific tumor phenotypes. Advances in the realm of SSTR2 investigation within HNSCC, with a specific spotlight on laryngeal squamous cell carcinomas (LSCC), tongue squamous cell carcinomas (TSCC), and nasopharyngeal carcinomas (NPC), have been established. This study aims to provide a comprehensive overview of SSTR2 expression patterns, prognostic implications, distinctive signaling pathways, epigenetic modifications, and potential therapeutic strategies associated with SSTR2 in HNSCC.

18 F-fludeoxyglucose positron emission computed tomography (18 F-FDG-PET/CT) versus 68 Ga-DOTATATE-PET/CT in patients with head and neck cancer: Comparisons and implications for treatment

BACKGROUND

Tumor-specific molecular imaging in head and neck squamous cell carcinoma (HNSCC) is not well established. Somatostatin receptors (SSTRs) are found in solid tumors, including HNSCC. ⁶⁸ Ga-DOTATATE, a commercially available radionuclide that binds SSTRs, may have utility in imaging HNSCC.

METHODS

Patients with HNSCC received pretreatment imaging with ¹⁸ F-FDG-PET/CT and ⁶⁸ Ga-DOTATATE. Imaging was compared for concordance. When available, surgical resection specimens were compared to pretreatment imaging findings. Historic HNSCC tumor specimens were assessed for both SSTR and p16/human papilloma virus (HPV) expression.

RESULTS

Twenty patients were imaged. Fifteen had oropharyngeal cancer. Primary tumor site was concordant between imaging modalities for all patients. One of 45 lymph nodes was discordant. Retrospective specimen review showed a significant correlation with SSTR expression and HPV/p16 expression. No adverse events occurred.

CONCLUSIONS

⁶⁸ Ga-DOTATATE imaging is safe and effective in HNSCC. SSTR expression may be increased in HPV-mediated tumors. Targeted therapies to SSTR should be explored.

Advances in nuclear medicine-based molecular imaging in head and neck squamous cell carcinoma

Head and neck squamous cell carcinomas (HNSCCs) are often aggressive, making advanced disease very difficult to treat using contemporary modalities, such as surgery, radiation therapy, and chemotherapy. However, targeted therapy, e.g., cetuximab, an epidermal growth factor receptor inhibitor, has demonstrated survival benefit in HNSCC patients with locoregional failure or distant metastasis. Molecular imaging aims at various biomarkers used in targeted therapy, and nuclear medicine-based molecular imaging is a real-time and non-invasive modality with the potential to identify tumor in an earlier and more treatable stage, before anatomic-based imaging reveals diseases. The objective of this comprehensive review is to summarize recent advances in nuclear medicine-based molecular imaging for HNSCC focusing on several commonly radiolabeled biomarkers. The preclinical and clinical applications of these candidate imaging strategies are divided into three categories: those targeting tumor cells, tumor microenvironment, and tumor angiogenesis. This review endeavors to expand the knowledge of molecular biology of HNSCC and help realizing diagnostic potential of molecular imaging in clinical nuclear medicine.

Molecular and Clinical Implications of Somatostatin Receptor Profile and Somatostatin Analogues Treatment in Oral Cavity Squamous Cell Carcinoma

Simple Summary

The treatment of oral squamous cell carcinoma (OSCC) represents a significant problem worldwide. Among cancers with the highest incidence, OSCC renders one of the worst prognoses. Therefore, novel prognostic biomarkers and therapeutic tools to tackle OSCC are urgently needed. Somatostatin-analogues (SSA) are an invaluable therapeutic option in the treatment of several cancers. We aimed to determine the expression levels of all somatostatin-receptors (SSTs) in OSCC, compared to adjacent healthy control tissues, to analyze the relationship of SSTs expression with key clinical and histopathological data, and to explore the direct in vitro effect of different SSAs on OSCC cancer cells. Our findings highlight a potential role of SST₂ as a good prognostic biomarker for recurrence and metastasis in OSCC and unveil that SSA exerts antitumoral effects on OSCC cells, providing a relevant clinical conclusion, which should be soon tested for their use in humans.

Abstract

Oral squamous cell carcinoma (OSCC) incidence has increased by 50% over the last decade. Unfortunately, surgery and adjuvant radiotherapy and chemotherapy are still the mainstream modality of treatment, underscoring the need for alternative therapies. Somatostatin-analogues (SSA) are efficacious and safe treatments for a variety of tumors, but the presence of somatostatin-receptors (SSTs) and pharmacological effects of SSA on OSCC are poorly known. In this study, we demonstrated that SST₂ and SST₃ levels were significantly higher in OSCC, compared to adjacent healthy control tissues. SST₂ expression was associated with less regional metastasis and a lower recurrence rate. Moreover, SST₂ was elevated in OSCC and associated with histopathological good prognosis factors, such as high peritumoral inflammation, smaller depth of invasion, and expansive vs. infiltrative front of tumor invasion. Importantly, treatment with different SSA (octreotide, lanreotide, and pasireotide) significantly reduced cell-proliferation in OSCC primary cell cultures. Altogether, this study demonstrated that SST₂ is overexpressed in OSCC vs. healthy tissues and could represent a novel prognostic biomarker, since its expression is associated with tumors that show better prognostic factors and less recurrent rate. Moreover, our data unveil clear antitumoral effects of SSAs on OSCC, opening new avenues to explore their potential as targeting therapy to OSCC.

Epigenetic regulation of somatostatin and somatostatin receptors in neuroendocrine tumors and other types of cancer

Both somatostatin (SST) and somatostatin receptors (SSTRs) are proteins with important functions in both physiological tissue and in tumors, particularly in neuroendocrine tumors (NETs). NETs are frequently characterized by high SSTRs expression levels. SST analogues (SSAs) that bind and activate SSTR have anti-proliferative and anti-secretory activity, thereby reducing both the growth as well as the hormonal symptoms of NETs. Moreover, the high expression levels of SSTR type-2 (SSTR2) in NETs is a powerful target for therapy with radiolabeled SSAs. Due to the important role of both SST and SSTRs, it is of great importance to elucidate the mechanisms involved in regulating their expression in NETs, as well as in other types of tumors. The field of epigenetics recently gained interest in NET research, highlighting the importance of this process in regulating the expression of gene and protein expression. In this review we will discuss the role of the epigenetic machinery in controlling the expression of both SSTRs and the neuropeptide SST. Particular attention will be given to the epigenetic regulation of these proteins in NETs, whereas the involvement of the epigenetic machinery in other types of cancer will be discussed as well. In addition, we will discuss the possibility to target enzymes involved in the epigenetic machinery to modify the expression of the SST-system, thereby possibly improving therapeutic options.

Incidental Finding of Squamous Cell Carcinoma on a 68Ga-DOTATATE PET Scan

Neuroendocrine tumors (NETs) are a relatively rare entity; however, the incidence and prevalence of these tumors are increasing, likely attributed to improved diagnostic accuracy. The diagnosis of suspected NETs is facilitated by clinical symptoms, laboratory test abnormalities such as elevated chromogranin-A, and other diagnostic modalities such as the use of computed tomography scans, magnetic resonance imaging scans, positron emission tomography (PET) scans, and biopsy. The expression of high levels of somatostatin receptors in NETs enables the use of a specialized PET scan using the radiolabeled somatostatin analogues 68Ga-DOTATATE. The sensitivity and specificity of 68Ga-DOTATATE PET is very high for the diagnosis of NETs, but the specificity decreases especially with no clear symptoms and with only borderline elevated tumor markers. We present a case of a suspected NET, which was initially diagnosed as a metastatic NET by virtue of a positive 68Ga-DOTATATE PET scan; however, on biopsy it was revealed to be a squamous cell carcinoma originating from the head and neck.

SSTR2 promoter hypermethylation is associated with the risk and progression of laryngeal squamous cell carcinoma in males

Background

Somatostatin receptor 2 (SSTR2) encodes somatostatin receptor that can inhibit the cell proliferation of solid tumors. Promoter hypermethylation is likely to silence the expression of SSTR2. The goal of our study was to investigate the association between SSTR2 promoter methylation and the risk and progression of laryngeal carcinoma.

Methods

In the current study, tumor tissues and their adjacent non-tumor tissues were collected from a total of 87 laryngeal squamous cell carcinoma (LSCC) male patients. DNA methylation levels of nine SSTR2 promoter CpGs were measured using the bisulphite pyrosequencing technology.

Results

Our results revealed that there was a significantly increased SSTR2 promoter methylation in LSCC tissues than in their adjacent non-cancerous tissues (adjusted P = 0.003). Breakdown analysis by age indicated that the significant association was mainly contributed by patients younger than 60 (adjusted P = 0.039) but not in patients older than 60. Meanwhile, the significant association was observed in the patients with moderately (adjusted P = 0.037) and well differentiated tissues (adjusted P = 0.028), as well as the patients with histological stage IV (adjusted P = 0.031). Multivariate Cox analysis suggested that SSTR2 promoter methylation was an independent prognostic factor of LSCC (HR = 1.127, 95 % CI = 1.034–1.228).

Conclusions

In conclusion, SSTR2 promoter hypermethylation might be associated with the risk and progression of LSCC in males.

Aberrant methylation inactivates somatostatin and somatostatin receptor type 1 in head and neck squamous cell carcinoma

PURPOSE

The aim of this study was to define somatostatin (SST) and somatostatin receptor type 1 (SSTR1) methylation profiles for head and neck squamous cell carcinoma (HNSCC) tumors at diagnosis and follow up and to evaluate their prognostic significance and value as a biomarker.

METHODS

Gene expression was measured by quantitative RT-PCR. Promoter methylation status was determined by quantitative methylation-specific PCR (Q-MSP) in HNSCC.

RESULTS

Methylation was associated with transcription inhibition. SST methylation in 81% of HNSCC tumor specimens significantly correlated with tumor size (P = 0.043), stage (P = 0.008), galanin receptor type 2 (GALR2) methylation (P = 0.041), and tachykinin-1 (TAC1) (P = 0.040). SSTR1 hypermethylation in 64% of cases was correlated with tumor size (P = 0.037), stage (P = 0.037), SST methylation (P < 0.001), and expression of galanin (P = 0.03), GALR2 (P = 0.014), TAC1 (P = 0.023), and tachykinin receptor type 1 (TACR1) (P = 0.003). SST and SSTR1 promoter hypermethylation showed highly discriminating receiver operator characteristic curve profiles, which clearly distinguished HNSCC from adjacent normal mucosal tissues. Concurrent hypermethylation of galanin and SSTR1 promoters correlated with reduced disease-free survival (log-rank test, P = 0.0001). Among patients with oral cavity and oropharynx cancer, methylation of both SST and SSTR1 promoters correlated with reduced disease-free survival (log-rank test, P = 0.028). In multivariate logistic-regression analysis, concomitant methylation of galanin and SSTR1 was associated with an odds ratio for recurrence of 12.53 (95% CI, 2.62 to 59.8; P = 0.002).

CONCLUSIONS

CpG hypermethylation is a likely mechanism of SST and SSTR1 gene inactivation, supporting the hypothesis that SST and SSTR1 play a role in the tumorigenesis of HNSCC and that this hypermethylation may serve as an important biomarker.

Neuroendocrine differentiation in head and neck squamous cell carcinoma

OBJECTIVE

Tumours with neuroendocrine differentiation frequently express chromogranin A, synaptophysin and somatostatin receptors. The role of neuroendocrine differentiation in head and neck squamous cell carcinoma is not yet clear.

METHOD

The presence of chromogranin A, synaptophysin and somatostatin receptors was studied immunohistochemically in 78 head and neck squamous cell carcinoma specimens.

RESULTS

Sparse chromogranin A expression was found in 41 per cent, associated with high chromogranin A messenger RNA expression and the presence of dense core granules. Low synaptophysin expression was found in 18 per cent. The highest staining scores were found for somatostatin receptor 5 (82 per cent), followed by somatostatin receptor 1 (69 per cent) and somatostatin receptor 2 (54 per cent), whereas somatostatin receptors 3 and 4 expression was low. Expression was not correlated with tumour stage or survival.

CONCLUSION

Cells with neuroendocrine differentiation are sparsely scattered in some head and neck squamous cell carcinomas. Their pathophysiological role is elusive. In contrast, somatostatin receptor and particularly somatostatin receptor 5 expression is frequent in head and neck squamous cell carcinoma. Somatostatin receptor expression is not considered to indicate neuroendocrine differentiation in head and neck squamous cell carcinoma.

Preliminary study of proteomic shift from normal to premalignant laryngeal lesions and to laryngeal squamous cell carcinoma

CONCLUSIONS

The malignant shift was discovered to begin even in the premalignant stage in the comparison of premalignant laryngeal lesions (PMLLs) with laryngeal squamous cell carcinoma (LSCC) and healthy controls. The differential expression of proteins among normal, PMLL, and cancer cells might provide the prediction for the changes from normal to PMLL and to malignant disease.

OBJECTIVES

To study the serum proteomic shift from normal control to PMLL and progression to LSCC.

MATERIALS AND METHODS

A total of 211 serum samples from patients with LSCC (n = 89 at stage I-II) or PMLL (n = 57), or normal controls (n = 65) were obtained with informed consent. Serum protein profiles on weak cationic exchange (WCX2) were performed by surface-enhanced laser desorption/ionization mass spectrometry (SELDI-TOF MS) and then analyzed by Biomarker Wizard software.

RESULTS

Peak intensities of serum from PMLLs were compared to normal controls and serum from patients with LSCC. Mean intensity differed significantly only for one peak (4532 Da, p = 0.032) between LSCC and precancerous diseases, while 13 peaks differed significantly between precancerous diseases and normal controls. Eighteen biomarkers were selected to separate stage I- II LSCC patients and healthy controls.

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.