A soft agarose clonogenic assay is presented which has been optimized for the growth of human gastrointestinal adenocarcinomas. Samples from 15 gastric and colonic solid tumors and from 2 noncancerous stomachs (control cultures) were disaggregated by treatment with collagenase at 37° overnight. Colonies appeared 10 to 15 days after plating, with a cloning efficiency between 0 and 0.82%, which was markedly improved by a fibroblastic feeder layer. The results suggest a correlation between cloning efficiency and the degree of differentiation of the initial tumor. Histochemistry, electron microscopy, and a carcinoembryonic antigen immunofluorescence assay showed that the colonies consisted of cells with the same characteristics as those of the original tumor. This colony formation assay appears to be potentially useful for assessing the stem cell pool of gastrointestinal tumors. It will be valuable for studying their response to chemotherapeutic agents in vitro. This clonogenic assay may also permit the establishment of cancer cell lines.

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This investigation was supported in part by a grant from the Faculté Xavier Bichat and in part by a grant from the Ligue Nationale Française contre le Cancer.

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