Human kallikrein 10 in surgically removed human pituitary adenomas

Objective: Human kallikrein-like peptidase 10 (KLK10), a serine protease, plays an important role in the regulation of cell proliferation and tumor growth. In this work, we investigated KLK10 immunoexpression in various types of surgically removed human pituitary tumors. Design: Specimens were fixed in formalin and embedded in paraffin. Immunostaining was performed by the streptavidin-biotin-peroxidase complex protocol using the LSAB+ Kit and a KLK10-specific rabbit polyclonal antibody. Results: Results showed that both treated and untreated prolactin-producing pituitary adenomas and carcinomas as well as TSH-producing pituitary adenomas and carcinomas were conclusively immunopositive for KLK10. Immunostaining was mainly localized in the cytoplasm and was clearly visible in many adenoma cells. In various other tumor types (oncocytoma, gonadotroph, somatotroph adenomas, and carcinomas), cytoplasmic immunopositivity was mild to moderate and seen only in a few unevenly distributed adenoma cells. Immunopositivity in the nuclei of various tumor types, as well as dual cytoplasmic and nuclear localization of KLK10 in some of the tumor types, was an intriguing finding. Immunoexpression in GH-producing adenomas exposed to octreotide, a long-acting somatostatin analog, was significantly increased when compared to unexposed GH-producing tumors. Conclusion: More studies are needed to ascertain the role of KLK10 in pituitary tumor development, prognosis, and progression. The question of whether genetic abnormalities and the microenvironment can affect KLK10 immunoexpression should also be investigated.