Three-dimensional, but not two-dimensional, culture results in tumor growth enhancement after exposure to anticancer drugs.

Previously, we have adapted a recently developed three-dimensional chemosensitivity test, the collagen gel droplet embedded culture drug sensitivity test (CD-DST), for evaluation of chemosensitivity of 12 anticancer drugs against colorectal adenocarcinoma, and surprisingly, it was found that tumor growth enhancement was occasionally observed even after exposure to anticancer drugs. In this study, the CD-DST was applied for human cervical carcinoma cell line HeLa-Ohio (HeLa) cells and its MDR1/P-glycoprotein-overexpressing subline, Hvr100-6 cells, and 12 anticancer drugs were assessed in terms of chemosensitivity and deterioration of tumor, and the results were compared with those by two-dimensional WST-1 assay. Growth enhancement was observed in Hvr100-6 cells, not in HeLa cells, for mitomycin C with the ratio of total volume of colonies in the treated group to that in the untreated group (T/C%) of 135.0%, doxorubicin with T/C% of 162.5% and cyclophosphamide with T/C% of 122.0%, and this was not observed in WST-1 assay. Multidrug resistance was detected both for CD-DST and WST-1 assay. The values of T/C% in CD-DST were comparable with or higher than those of the survival fraction (%) in WST-1 assay, and modification of WST-1 assay procedure gave similar results, suggesting a higher resistance in three-dimensional than in two-dimensional culture. Further investigations should be addressed to the association of MDR1/P-glycoprotein with tumor growth enhancement.