Ultrastructural studies on Regan and non-Regan isoenzymes of alkaline phosphatase in human ovarian cancer cells.

Abstract

Summary In order to examine the intracellular localization of the Regan isoenzyme of alkaline phosphatase in human cancer cells, ovarian cancer cells from three selected patients were studied histochemically and electron microscopically. For selection of these cases, the patients9 ascites or tissue tumor cells derived from primary tumors were smeared or sectioned and stained histochemically for alkaline phosphatase by use of a simultaneous azodye coupling technique with or without amino acid inhibitors (d- and l-phenylalanine and l-homoarginine) in the incubation mixtures. These amino acids are able to distinguish the Regan isoenzyme from non-Regan alkaline phosphatases. Kaplow9s scoring technique was applied for evaluation of the respective enzyme activities. Of the three representative cases selected for this paper, alkaline phosphatase of the cells from Case 1 (S. C.) revealed high sensitivity only to l-phenylalanine; Case 2 (T. C.) showed sensitivity to l-phenylalanine and l-homoarginine; Case 3 (H. F.) showed sensitivity only to l-homoarginine. The staining features appeared granular (Cases 1 and 2) and diffuse or membranous (Cases 2 and 3) on light microscopy. The tissue cancer cells obtained by surgical operation were processed for electron microscopic examination in combination with the histochemical reaction for alkaline phosphatase with the metal precipitation method of Hugon and Borgers. l-Phenylalanine-sensitive cases (Cases 1 and 2) showed enzyme activity on mitochondria of the cancer cells in most of the cells and occasionally in other organelles such as Golgi complexes, endoplasmic reticulum, and nuclear membranes, while in l-homoarginine-sensitive cases (Cases 2 and 3), especially in Case 3, deposition of the enzyme product was distinctly confined to the cell membranes. Case 2 also displayed cell membrane activities in addition to the other localizations described. From these results, there seemed to exist a likelihood that mitochondrial alkaline phosphatase is related to l-phenylalanine sensitivity, i.e., Regan alkaline phosphatase, while the cell membrane activities are sensitive to l-homoarginine i.e., non-Regan isoenzyme in ovarian cancer.