SSTR-2 Expression in Solid Tumors: An Immunohistochemistry Analysis

Aman Chauhan; Susanne Arnold; Therese Bocklage; Donglin Yan; Ning Li; Lowell Anthony; Derek Allison

doi:10.1530/endoabs.89.C41

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Endocrine Abstracts (2022) 89 C41 | DOI: 10.1530/endoabs.89.C41

NANETS2022 15th Annual Multidisciplinary NET Medical Symposium NANETS 2022 Clinical – Surgery/Applied Pathology (13 abstracts)

SSTR-2 Expression in Solid Tumors: An Immunohistochemistry Analysis

Aman Chauhan ^1,4 , Susanne Arnold ^1,4 , Therese Bocklage ^2,4 , Donglin Yan ^3,4 , Ning Li ^3,4 , Lowell Anthony ^1,4 & Derek Allison ^2,4

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¹Division of Medical Oncology, University of Kentucky; ²Department of Pathology, University of Kentucky; ³Department of Biostatistics, University of Kentucky; ⁴Markey Cancer Center, University of Kentucky.

Background: Somatostatin receptor (SSTR) expression has been characterized in well-differentiated neuroendocrine tumors (NET). However, the understanding of receptor expression in various non-neuroendocrine solid tumors is limited. This study was performed to evaluate SSTR-2 in various cancers to provide a rational basis for SSTR-2 targeted anti-cancer therapies.

Methods: Formalin-fixed paraffin, paraffin-embedded tissue was obtained from pathology archives after institutional review board approval. Tumor blocks were prospectively stained with an anti-SSTR-2 antibody via immunohistochemistry (IHC). The following tumor types were studied: small cell carcinoma (Code 0; n=14), medullary thyroid cancer (Code 1, n=10), melanoma (Code 2, n=10), merkel cell carcinoma (Code 3, n=10), head and neck p16 positive squamous cell carcinoma (Code 4, n=10), well-differentiated NET (Code 5, n=10), paraganglioma and pheochromocytoma (Code 6, n=20), poorly differentiated neuroendocrine carcinoma (Code 7, n=9), and p16 negative squamous cell cancer (Code 8, n=4). IHC was scored as follows: SSTR2 Intensity (0=none, 1=weak, 2=moderate, 3=strong), SSTR2 Localization (1= membranous; 2=cytoplasmic; 3=mixed), SSTR2 % Positivity (5% increments)

Results: 64% of SCLC samples stained positive for SSTR-2, and 35.7 % of SCLC samples stained strongly positive for SSTR-2. 60% of Head and Neck carcinoma samples stained positive for SSTR-2, and 40% of these were of moderate intensity. As expected, 100% well-differentiated NET samples stained positive for SSTR-2. Only 33% of poorly differentiated neuroendocrine carcinoma samples were stained positive for SSTR-2, out of which only 11 % stained strongly positive for SSTR-2.

Conclusions: As expected, well-differentiated NET expressed very high SSTR-2 positivity with high intensity. However, a subset of small cell carcinoma and head and neck p16 positive squamous cell carcinoma were observed to express SSTR-2. Targeting SSTR-2 in small cell carcinoma and head and neck cancer with the help of radiolabeled somatostatin analog could be a promising therapeutic approach. Based on our SSTR-2 IHC data, a prospective study of SSTR-2 assessment with the help of gallium 68 dotatate PET imaging in small cell lung cancer patients is currently underway at Markey Cancer Center.

Abstract ID 21481