Presence of sst5TMD4, a truncated splice variant of the somatostatin receptor subtype 5, is associated to features of increased aggressiveness in pancreatic neuroendocrine tumors.
With the exception of sstr3, NET were highly positive for all receptor subtypes (42, 63, 6, 32 and 65% of tumors were positive for sstr1, sstr2a, sstr3, sstr4 and sstr5, respectively). sstr1, sstr2a and sstr5 were present at the plasma membrane and in the cytoplasm of tumor cells, whereas sstr3 and sstr4 were almost exclusively cytoplasmic.
Analysis of mRNA expression of the SSTR subtypes showed that SSTR2 and SSTR5 were expressed in all of the studied NETs; SSTR1 and SSTR4 in all but 3 tumors (86%); and SSTR3 in only 10 NETs (49%).