SSTR2A Is Highly Expressed in Metastatic Uveal Melanoma
Misti Coronel, Matias E Valsecchi, Takami Sato, Agnieszka K Witkiewicz. Thomas Jefferson University Hospital, Philadelphia, PA
Background: Somatostatin is a neurohormone that is found in both the nervous system and certain peripheral organs. Its biological effects, which include inhibition of cell secretion and regulation of cell proliferation and differentiation, are effected through interaction with the somatostatin receptor (SSTR), of which there are at least five distinct subtypes. SSTRs have been shown to be expressed by several different tumors, including uveal malignant melanoma. Somatostatin receptors represent a potential target for treatment of melanoma, but studies to this date have been inconclusive as to the prognostic significance of SSTR subtype expression. In addition, no prior studies to this date have examined SSTR expression in metastases from uveal melanomas.
Design: Our study consisted of 15 cases of metastases from uveal malignant melanoma. All cases were stained for SSTR2A and SSTR5 (Pierce Antibodies). For SSTR2A, cases were evaluated for positive cytoplasmic, nuclear, and/or membranous staining. Cytoplasmic staining was graded on a three point scale, 0 = no staining, 1 = diffuse weak staining or strong staining in <50%, 2 = diffuse strong staining. Nuclear and membranous staining were evaluated by percentage of cells staining (positive stain, >20%). SSTR5 was evaluated for cytoplasmic staining by percentage of cells staining. The staining pattern was correlated with OctreoScan results.
Results: Cytoplasmic staining for SSTR2A was most common, with 93% of cases staining positive (14/15). 60% (9/60) of cases exhibited nuclear staining for SSTR2A; membranous staining was negligible and was not included in the analysis. 7% (1/15) cases stained positively for SSTR5. Of the cytoplasmic SSTR2A positive cases, 93% were also positive by OctreoScan (13/14). In addition, 45% of these cases were positively correlated in terms of the surgical specimen site and the body site of OctreoScan positivity (5/11; two cases were unable to be determined). The case negative for cytoplasmic SSTR2A was also negative by OctreoScan. 100% (7/7) of cases which positively stained for nuclear SSTR2A were also positive by OctreScan; 57% (4/7) of these had positive site correlation. The SSTR5 positive case was also positive by OctreoScan, with positive site correlation.
Conclusions: Somatostatin receptors are commonly expressed in metastases of uveal melanoma. Staining for SSTR2A is correlated with OctreoScan results for somatostatin receptors. These receptors represent a potential target for treatment of metastatic uveal melanoma.
Wednesday, March 21, 2012 1:00 PM
Poster Session VI # 96, Wednesday Afternoon