Effect of confluence state and passaging on global cancer gene expression pattern in oral carcinoma cell lines.

BACKGROUND After establishment of a cell culture, inhomogenous growth and cell selection takes place at early passages. Reproducing the same confluence state among experiments might be difficult. MATERIALS AND METHODS Here we used cDNA arrays to compare the global gene expression pattern of two oral cancer cell lines at 80%, 100% and super-confluence stages. Also, the stability of the global gene expression pattern during culture was assessed in two cell lines at passages 10 and 53 (early and late passage). An intraclass correlation coefficient test was used for comparisons. RESULTS The consistency between the different confluence states was almost perfect (> 0.8) and substantial (0.6-0.8). Also the consistency between early and late passages was almost perfect in the cell lines used. CONCLUSION Our results indicate that neither the state of confluence nor passage have significant effects on the global gene expression profile, despite the variability in expression levels of individual genes.