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A new cell culture modality had already been established in our laboratory. Using this model, living KB and GBM 8401 tumor cells grew and proliferated exponentially in semipermeable microcapsules, implanted in vivo. The culture method was designed as a modality for a predictive anticancer drug sensitivity test. Its advantages included providing a three-dimensional growth and in vivo supply of nutrients. Tumor cell sensitivity to drugs can be assessed in vivo. The assay is applicable to virtually all histological types of human tumor cells. Using this technique, anticancer drug sensitivity tests of KB and GBM 8401 cells were evaluated. The results showed that such encapsulated cells grew and proliferated rapidly. In addition, the proliferation of KB cells was more rapid than that of GBM 8401 cells under conventional monolayer and in vivo microcapsule culture states. They were very sensitive to adriamycin and fluorouracil, and relatively resistant to cyclophosphamide while cultured in vitro. The viability percentage of microencapsulated KB cells cultured in vivo for two weeks was around 80-90%, roughly similar to that of the same cells conventionally cultured in vitro. However, the proliferation rates of encapsulated KB and GBM 8401 cells in vivo were significantly inhibited by all the drugs tested, with KB cells inhibited more significantly than GBM 8401. These results also suggest that some anticancer drugs needing to be bioactivated in vivo had better test results by this technique, and thus false negative results could be excluded. Also, the good repair capacity of microcapsules implanted in vivo, for damaged tumor cells previously incubated with chemotherapeutic drugs, appears to provide a much better environment for cell growth because much essential nourishment can be supplied. The inhibition percentage of fluorouracil to encapsulated cancer cells from patients with adenocarcinoma of the colon was also tested; they were 69.8% in vivo and 76.5% in vitro. This fast, relatively inexpensive in vivo model can be used to screen various anticancer drugs and help clinical oncologists to select the most effective agents for individual patients.

A rapid colorimetric microtiter assay was used in this study to analysis drug cytotoxicity. Through the reduction of tetrazolium salt, MTT [3-(4, 5-dimethyl-thiazol-2-yl) 2,5-diphenyl tetrazolium bromide], by living cells to form a blue formazan product. The level of MTT cleavage by viable cells of various origins was found to be in direct proportion to the number of cells (between 500-10,000 cells/well). By MTT methods, the growth profile and chemosensitivity of 4 human tumor cell lines (KB, Hep-2, HA22T, and CoLo205) to 4 anticancer drugs (adriamycin, 5-fluorouracil, 6-mercaptopurine and cyclophosphamide) were assessed. Results from this assay were compared with data assimilated simultaneously by dye exclusion and clonogenic assay. In general, good correlation was observed among the clonogenic, dye exclusion and MTT assays for continuous drug exposures, yet the MTT assay was more rapid in testing in vitro chemosensitivity against human tumor cell lines. The dye exclusion assay was the most sensitive, followed by the clonogenic and then the MTT assays. The ID50 values obtained from the MTT assay were approximately 3 to 5 times lower than those from the other two methods. Based on these studies, MTT assay appears to be a rapid, convenient, economical and reasonable tool in the initial-stage screening of large number of the in vitro anticancer drugs.