Automated imaging and quantitation of tumor cells and CFU-GM colonies in microcapillary cultures: toward therapeutic index-based drug screening.

Human colony forming units (CFUs) from both malignant and hematopoietic tissues can be assayed in vitro in microcapillary cultures, an alternative cloning system to the Petri dish methodology. For technical reasons, microcapillary culture may be ideally suited for new drug screening by therapeutic index. To achieve the high output required by screening programs, automated quantitation of CFUs is required. Toward this end, this paper reports the development of a prototype CapScan, an image analysis system that uses a novel axial laser illumination system to detect tumor cell colonies and, with technical modifications, CFU-granulocyte-macrophage (CFU-GM) colonies in microcapillary cultures. As currently configured, the CapScan can quantify colonies grown in a rack of 18 microcapillary cultures in 30 minutes or less. The sensitivity and detection specificity of tumor cell colonies is >90% with a coefficient of variance of 5-40%, dependent upon colony number. Over a range of colony numbers, CapScan and manual colony counts showed a linear correlation > -0.9, and yielded identical results in assays of doxorubicin inhibition of clonogenic P388 cells. As an additional advantage, the growth kinetics of individual colonies can also be monitored with the CapScan, making distinctions between cytotoxic and cytostatic drugs possible; colonies of freshly isolated human tumor cells can also be quantified. Thus, a microcapillary-based human tumor cloning assay that tests for resistance and/or sensitivity to chemotherapeutic agents may be useful in drug development programs and may also facilitate the development of chemotherapy for individual patient tumors, especially when tumor availability is limited.