EXPRESSION OF THE INTESTINAL-TYPE ALKALINE PHOSPHATASE (IAPH) IN NORMAL AND MALIGNANT HUMAN TISSUES

Abstract

Aim: Alkaline phosphatases (APh) are enzymes that are actively involved in important biological processes, including cell proliferation, cell-cell and cell-matrix interactions, and cell differentiation.

Materials and Methods: We studied the expression of the intestinal type AP (I-APh) in a series of normal and malignant human tissues of breast, lung, colon, head and neck, uterus, cervix, urinary bladder and prostate origin.

Results: The enzyme was strongly expressed in all cellular constituents, i.e, the epithelium, the stromal fibroblasts and the endothelial cells, of all normal tissues studied, save glandular endometrial cells. Such a consistent I-APh expression, however, was not seen in malignant tumours. In these tissues, an apparent down-regulation of I-APh expression was a feature for tumor cells, stroma fibroblasts and vessels.

Conclusions: The reason for this enzymatic suppression is far from clear. Nonetheless, the discordant I-APh phosphohydrolytic activity between normal and tumor tissues could be useful for the development of cytoprotective and/or cytotoxic compounds of high selectivity.