Vital cell labelling for the detection of invasive growth in the chick embryo skin invasion assay.
Of the various in vitro invasion assays described, only a few use tissues as substrates, for example, the chick heart fragment assay and the chick embryo skin (CES) invasion assay (Noguchi et al., 1978). We have improved culture conditions for the CES invasion assay (Schlage, 1989). A suspension of neoplastically transformed cells is incubated on an explanted piece of skin from a 9-10-day-old chick embryo. After 1, 2 and 3 days, the explants are fixed and cross-sectioned. As a measure of invasiveness, the number of invading cells and their mitotic activity should be evaluated. We tested the suitability of the vital fluorescence dye PKH-2 (Horan and Slezak, 1989) for improving discrimination between CES cells and invading cells; human cervical carcinoma (HeLa), 3-methylcholanthrene (MCA)-transformed mouse embryo fibroblasts (10T1/2-MCA7), and MNNG-transformed rat tracheal epithelial cells (RTE-MNNG). The three cell lines formed distinct infiltrates on days 2 and 3, but on day 1, only 10T1/2-MCA7 and RTE-MNNG cells formed infiltrates. Although PKH-2 labelling was found suitable for the detection of invasion, cellular resolution and dye stability in cryosections is still unsatisfactory. To overcome this for routine work, we suggest improving the histological processing and using PKH-26, which is a more stable dye.
Schlage
W K
WK
INBIFO Institut für biologische Forschung, Fuggerstr. 3, 51149 Köln, Germany.
Bülles
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H
Kurkowsky
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