Capillary cloning of primary human tumor cells: assay miniaturization for drug efficacy testing

The conventional double-layer agar method of cloning human tumor cells requires a substantial number of viable tumor cells and 14-21 days of culture. These prerequisites frequently limit its utility as an assay. In an attempt to circumvent these limitations and to reduce the amount of drug that is needed in the assay, we have further developed and miniaturized the assay in which human tumor cells are cloned in glass microcapillary tubes. Cultures consisted of 50 microliters containing 15,000 nucleated cells in 975 mm capillary tubes which were incubated for seven days. The results from 50 consecutive tumor biopsies resulted in cloning efficiencies, ranging from 0.007% to 1.0% with an overall successful cloning of 88% of all tumors tested and a good linear growth relationship and chemotherapy sensitivity. This miniaturized assay offers distinct advantages for drug efficacy testing including high cloning efficiencies, small tumor sample and drug requirements, quicker assay turnaround time and a general conservancy of reagents and incubator space.