Аннотация:Amplification and expression status of the CCND1 gene in 12 cell lines derived from esophageal cancer was evaluated and the differences in the cell proliferation and morphology were investigated. Amplification was observed in 6 cell lines, all of which consequently overexpressed the mRNA. Although the amplification of the gene did not contribute to an increase of cell proliferation, an in vitro morphological transformation was observed in the colonies with an amplification of the CCND1 gene. An amplification/overexpression of the CCND1 gene plays an important role in the enhancement of cell transformation in esophageal squamous cell carcinoma cells.