Somatostatin receptor expression in Merkel cell carcinoma: correlation with clinical data

Abstract

Background

Merkel cell carcinoma (MCC) is a rare, high-grade neuroendocrine neoplasm (NEN) of the skin. Somatostatin receptors (SSTRs) are G protein-linked receptors that regulate cell proliferation and growth. SSTRs are expressed in many NENs; however, scant information is available on their expression in MCCs or their association with clinical parameters and patient outcomes.

Material and methods

This retrospective study was conducted at Helsinki University Hospital and the University of Helsinki. Using a tissue microarray, we investigated SSTR1-5 expression by immunohistochemistry in 99 MCC tissue samples. Samples were collected between 1983 and 2017 and coupled with the patients’ clinical data.

Results

SSTR2-SSTR5 were detected in 69%, 6%, 4%, and 1% of the tumours, respectively. However, SSTR1 expression was not observed. Cytoplasmic SSTR2 positivity was associated with metastatic disease at the time of diagnosis (p = 0.009), but it did not correlate with disease-specificity or overall survival.

Conclusion

SSTR2-5 expression was observed in MCCs. In particular, SSTR2 expression is clinically valid because it is associated with metastatic disease at the time of diagnosis and can thus serve as a prognostic marker. Moreover, SSTR2 overexpression provides a molecular basis for tumour imaging and treatment with somatostatin analogues.

Keywords:

• Merkel cell carcinoma
• somatostatin receptor
• immunohistochemistry

Acknowledgments

We would like to acknowledge Jenni Niinimäki and Eija Heiliö for excellent technical assistance.

Ethical statement

The study protocol was approved by the Ethics Committee of the Helsinki University Hospital. The Ministry of Health and Social Affairs approved the data collection. The National Supervisory Authority for Welfare and Health granted permission to collect tissue samples.

Disclosure statement

The authors report no conflicts of interest.

Data availability statement

Due to the nature of the research, clinical data is not available. The original scores adjoined to the TMA is available at request.

Additional information

Funding

This research was funded by the Jane and Aatos Erkko Foundation (4706174), the Cancer Foundation Finland (no grant number to J. Arola), Liv Och Hälsa (no grant number to J. Arola), and the Helsinki University Hospital Research Fund (TYH2021204).