Cell aggregates in the soft agar “human tumour stem-cell assay”

A comparison of two culture techniques: An in vitro & an in vivo tumour colony-forming assay

“…The plating efficiency is low (usually one colony per 10,000 plated cells) and the number of specimens which result in adequate growth are low: in larger studies usually 40% (Von Hoff, 1983). Clumping of cells is a serious difficulty for any clonogenic cell assay, so that the descriptive term: 'colony-forming assay' is preferred to 'tumour stem cell assay' or 'clonogenic cell assay' (Agrez et al, 1982, Umbach et al, 1983.…”

Soft agarose culture human tumour colony forming assay for drug sensitivity testing: [3H]-thymidine incorporation vs colony counting

“…A 60,um D control (no drug treatment) colony is a 'standard' size used to measure colony formation in the soft agar colony forming assay for cell line, xenograft and primary tumour cells. (Agrez et al, 1982a). The number of cells in such a 60pgm D colony is highly variable from tumour to tumour.…”

“…Primary tumour agarose cultures were considered acceptable if: The number of viable colony counts was <25 on Day 1, the number of viable 60 um D images increased by at least 1N fold (minimum of 36) over that determined on Day 1 of incubation (Agrez et al, 1982a), and the uniformly cytotoxic 'positive control drug' (100ugml-' mercuric chloride) produced a > 70% decrease in 60 gm colony count. plot of data from one xenograft experiment is presented in Figure 3 Figure 5, Table IV).…”

“…Promising reports of good correlation between results of in vitro soft agar colony forming assays and patients' clinical response or resistance to chemotherapeutic agents have been published (Salmon et al, 1978;Alberts et al, 1980;Von Hoff et al, 1981, 1983. Despite this extensive international experience, major questions remain about the biologic significance, technical performance and clinical utility of such assays (Lancet Editorial, 1982;Lieber & Kovach, 1982;Selby et al, 1983;Agrez et al, 1982a;Lieber, 1983).…”

“…This extensive experience has generated concern about technical problems which occur in the performance of soft agar colony forming assays using samples of cells isolated from primary human tumours; publications on this topic have appeared in this journal previously (Agrez et al, 1982a; Alley & Lieber 1984& Lieber , 1985. Consequently, it was of interest to investigate whether the use of a different way of assessing cell proliferation and drug effects in such soft agar tumour colony forming assays might be as effective or more effective than simply optically counting the number of colonies formed.…”