IMMUNOHISTOCHEMICAL DETECTION OF ORNITHINE DECARBOXYLASE IN INDIVIDUAL CELLS - POTENTIAL APPLICATION FOR IN-VITRO CHEMOSENSITIVITY ASSAYS

Ornithine decarboxylase (ODC), which catalyzes the rate-limiting step in the biosynthesis of polyamines, can serve as a marker of proliferat ion. The presence of ODC protein in individual cells was quantitativel y detected by an immunofluorescence assay using an ACAS 570 computeriz ed fluorescence microscope. ODC was detected in KB-3-1 human epithelia l carcinoma cells grown in the absence of any drug. Vinblastine, which inhibits cell growth, caused the disappearance of ODC. On the other h and, ODC was detected in multidrug-resistant cells grown in the absenc e or in the presence of vinblastine. NIH 3T3 fibroblasts transformed b y the c-Ha-ras oncogene also contained ODC protein. This protein disap peared when the cells were treated with cycloheximide, which inhibits cell proliferation. These findings suggest that ODC can be detected in individual cells by immunofluorescence. Whether this method can be us ed for in vitro chemosensitivity tests remains to be studied.