Kallikrein gene expression in human pituitary tissues

Area of Science:

• Biochemistry
• Molecular Biology
• Endocrinology

Background:

• Glandular kallikreins (KLKs) are enzymes crucial for polypeptide processing.
• Human kallikreins include KLK1, KLK2 (hGK1), and KLK3 (prostate-specific antigen/PSA).
• KLK1 has been detected in rat pituitary and human prolactinomas.

Purpose of the Study:

• To investigate the expression of KLK1 and other KLK genes in human pituitary tumors.
• To determine if KLK gene expression correlates with pituitary hormone production.

Main Methods:

• Retrospective analysis of pituitary tissue from 11 patients with pituitary syndromes and 3 normal pituitaries.
• Northern blot analysis and KLK-specific reverse transcriptase-polymerase chain reaction (RT-PCR) were used to detect KLK gene expression.
• Sequencing confirmed the identity of KLK1 and KLK2 PCR products.

Main Results:

• No KLK1 gene expression was detected by Northern blot, but RT-PCR revealed expression of KLK1, KLK2, and KLK3 in many pituitary tumors.
• KLK1 was the most abundant, while KLK3 was the least abundant KLK gene detected.
• KLK1 expression showed no clear correlation with hormone gene expression (PRL, GH, POMC) and was present in normal pituitary tissue.

Conclusions:

• This study demonstrates low-level expression of KLK1, KLK2, and KLK3 in the human pituitary, with KLK2 and KLK3 expression being a novel finding.
• The lack of correlation between prolactin (PRL) and KLK1 gene expression suggests a more complex interaction in human pituitary function than observed in rodent models.
• These findings open new avenues for understanding the role of kallikreins in pituitary physiology and pathology.