Quantitative analysis of cancer invasion in vitro: comparison of two new assays and of tumour sublines with different metastatic capacity.

Various murine tumour sublines which differed considerably in their in vivo metastatic capacity were tested in vitro for their ability to invade normal tissue. For this purpose we developed two quantitative tests, a Boyden chamber endothelial cell invasion assay and a brain tissue microsphere invasion assay. The invasion of [75Se]methionine-prelabelled tumour cells into the normal tissues was followed by measuring the percentage of tumour-associated label in the brain microspheres or the endothelial monolayers after 12-48 h of co-cultivation. Clear and comparable differences existed in both assays between the amount of radiolabel found in the normal tissues after a co-cultivation with the different tumour lines. In three of the four tumour lines invasiveness correlated with metastatic capacity. The fourth line, a plastic adherent variant, was highly invasive but low metastatic. The ability of tumour cells to invade normal tissue, therefore, while necessary for the generation of metastases, is not in itself sufficient. Since both assays are independent of time-consuming histological sectioning and staining and allow a quantitative determination of invasive capacity of tumour cells grown as single cell suspensions they appear well suited for experimental manipulation and for screening of anti-invasive drugs.