Induction of apoptosis in the centre of multicellular tumour spheroids of colorectal adenocarcinomas--involvement of CD95 pathway and differentiation.

Multicellular tumour spheroids (MCTS) are three-dimensional cell culture systems which are widely used in cancer research. They are characterized by an outer zone of proliferating cells, an inner region of differentiating quiescent cells and an area of so-called necrotic cell death in their centre. The exact cause of this cell death, a controversy for many years, was the aim of the present study.