Cellular distribution of human tissue kallikreins: immunohistochemical localization

We have studied the immunohistochemical expression (IE) of eight non-tissue-specific human kallikreins (hKs) (hK5, 6, 7, 10, 11, 12, 13, and 14) in different normal tissues. The IE was always cytoplasmic, showing a characteristic pattern in some tissues. Comparison of the IE of all hKs studied in the different tissues revealed no major differences, suggesting that they share a common mode of regulation. Furthermore, hKs were immunohistochemically revealed in a variety of tissues, indicating that no protein is tissue-specific (except for hK2 and hK3, which have tissue-restricted expression). In general, our results correspond well with data from RT-PCR and ELISA assays. Glandular epithelia constitute the main kallikrein IE sites, and the staining in their secretions confirms that these proteases are secreted. A variety of other tissues express the proteins as well. We have also immunohistochemically evaluated all the above hKs in several malignant tissues. Tumors arising from tissues expressing kallikreins tested positive. Corresponding to the IE in normal glandular tissues, most hKs were expressed in adenocarcinomas. The prognostic value of several hKs was studied in series of prostate, renal cell, colon and urothelial carcinomas.