Comparative Immunohistochemical Detection of Somatostatin Receptor (SSTR)2a and Dopamine Receptor (D2R) in Pituitary Adenomas for New Therapeutic Strategies
C Inomoto, H Hirabayashi, M Takei, A Teramoto, RY Osamura. Tokai University School of Medicine, Isehara, Kanagawa, Japan; Nippon Medical School, Sendagi Bunkyo-ku, Tokyo, Japan
Background: Pituitary adenomas are known to be invasive and sometimes aggressive in behavior. Somatostatin analogue(SA) and dopamine agonist(DA) bind to somatostatin receptor(SSTR)2a and dopamine receptor(D2R) respectively and suppress hormone hypersecretion and tumor cell proliferation. They have been used separately for selected cases of pituitary adenomas. Recent development of chimeric SA-DA compound which binds to both SSTR2 and D2R (Ferone D et al. 2009) is the rationale for our immunohistochemical study to clarify both receptors in the same tumors.
Design: Total 27 cases of pituitary adenomas(5 cases each for the groups of GHomas, PRLomas, TSHomas, ACTHomas, Gnomas and 2 cases of null cell adenomas) were subjected to immunohistochemical staining for SSTR2a and D2R on the same tumors on formalin-fixed paraffin embedded(FFPE) sections. Anti-SSTR2a antibody(Gramsch Co.) and anti-D2R antibody(Gene Tex, Inc.) and polimer method were used. Grading was done as follows; 0-negative, 1+-weakly positive, 2+-strongly positive.
Results: Immunohistochemical staining was interpreted as positive when it was observed on the cell membrane of the tumor cells. Staining results 0, 1+ and 2+ for SSTR2a and D2R were as follows for each tumor group: GHomas-SSTR2a 1+(2cases),2+(3cases), D2R 0(2cases),1+(2cases),2(1case), PRLomas-SSTR2a 0(5),D2R 1+(3cases), 2+(2cases), TSHomas-SSTR2a 2+(5cases), D2R 0(1case) 1+(1case),2+(3cases), ACTHomas-SSTR2a 0(4cases),1+(1case), D2R 0(2cases) 1+(3cases), Gnomas-SSTR2a 0(4cases), 1+(1case), Null adenoma-SSTR 1+(2cases),2+(1case), D2R 0(2cases) 1+(1case).