This mechanism does, however, seem unlikely to play a big part in cervical carcinomas, as we show that M-phase cells, and subsequently also cells in early G1, do not contain any cyclin E. In more general terms, our findings that the levels of cyclin E rarely or never are completely free of cell cycle control in vivo in cervical carcinomas raise some questions regarding the applicability of transfection studies in vitro in which cell cycle-regulated proteins are ubiquitously expressed in order to mimic the situation in tumours. Here, CCNE1 is linked to neoplasm.