Direct immunoperoxidase staining for regan isoenzyme of alkaline phosphatase in human tumor tissues

: Immunoperoxidase staining for Regan isoenzyme of alkaline phosphatase was performed on cryostat sections of five human tumor tisssues. With a direct immunoperoxidase staining for the localization of Regan isoenzyme at the light and electron microscope levels, sections previously fixed with 0.05 M phosphate-buffered 4% paraformaldehyde were reacted with rabbit antisera to human placenta alkaline phosphatase conjugated to horseradish peroxidase. Comparison of conventional histochemistry and immunohistochemistry for Regan isoenzyme indicated that strong specific immunoperoxidase staining appeared on the cell membrane surface, and a diffuse one, in the cytoplasm of lung and colon cancer tissue cells showing L-phenylalanine-sensitive alkaline phosphatase. No immunoperoxidase reaction was obtained in tumor cells showing sensitivity to L-homoarginine or lacking aklaline phosphatase activity.