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 proliferation. The presence of ODC protein in individual cells was quantitatively detected by an immunofluorescence assay using an ACAS 570 computerized fluorescence microscope. ODC was detected in KB-3-1 human epithelial carcinoma cells grown in the absence of any drug. Vinblastine, which inhibits cell growth, caused the disappearance of ODC. On the other hand, ODC was detected in multidrug- resistant cells grown in the absence or in the presence of vinblastine. NIH 3T3 fibroblasts transformed by the c-Ha-ras-oncogene also contained ODC protein. This protein disappeared 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 used for in vitro chemosensitivity tests remains to be studied.