[Human tumor stem cell assay]

Human tumor stem cell assay is an in vitro colony-forming technique. Double soft agar layers are used for culture tumor cells and cell lethality is judged by the numbers of colony formation in this assay. Single-cell suspension made from various malignant materials in cancer patients is placed in culture after exposing to various anticancer agents for one hour and incubated for two weeks. Antitumor effects of various anticancer agents against individual patients are evaluated by % inhibition of colony formation. Of 57 tumor specimens 42 (74%) formed at least five colonies per plate (per 0.5 x 10(6) cells). The colony-forming rates of various malignancies are as follows: breast cancer 14/15 (93%), ovarian cancer 8/10 (80%), stomach cancer 5/13 (38%), sarcoma 4/5 (80%), lung cancer 1/4 (25%), colon cancer 3/3, each of pancreas cancer, leukemia and primary unknown adenocarcinoma 2/2, malignant lymphoma 1/1. The median plating efficiency (number of colonies/number of nucleated cells plated) is 0.02% (range: 0.001-0.3%). High correlation between human tumor stem cell assay results and response of an individual patient's tumor to chemotherapy is reported by Salmon and Von Hoff. Human tumor stem cell assay is useful tool for the high prediction of chemosensitivity response.