Postconfluent multilayered cell line cultures for selective screening of gemcitabine.

The in vitro cytotoxicity of gemcitabine (dFdC) was tested in ovarian and colon cancer cell lines grown as monolayers and three-dimensional multilayered cell cultures. In our model, dFdC showed slight selectivity in cytotoxicity against ovarian over colon cancer cells, when cell lines were grown as monolayers. However, when cell lines were grown as multilayers, this selectivity was accentuated: A2780 multilayers were 14 times less sensitive than monolayers, but the colon cancer cell lines were more than 1000 times more resistant than their corresponding monolayers. The accumulation of the active metabolite, dFdCTP, after 24 h exposure to 1 microM dFdC varied between 1100 and 1900 pmol/10(6) cells in monolayers. This was 5 times lower in multilayers compared with monolayers of all four cell lines, which can, in part, explain the lower sensitivity of the multilayers. In addition, it appears that the amount of the active metabolite retained is more important than the amount accumulated initially, since the differences between the ovarian and the colon cancer cell lines were more evident in retention experiments. Exposure to dFdC caused a 2-3-fold increase in the levels of several nucleotides, except for the CTP pools in the colon cancer lines, which were reduced by 3-fold at the highest dFdC concentration (10 microM). The findings with the multilayer model are in better agreement with in vivo activity in ovarian cancer and colon cancer than those with the monolayer system. This indicates the potential of the multilayer system to be a better predictive model than the conventionally used monolayer cultures.