Increased susceptibility of cells to inducible apoptosis during growth from early to late log phase: an important caveat for in vitro apoptosis research

The physiologic mode of cell death known as apoptosis has become a major fo cus of scientific research due to its biologic importance. Much of this res earch involves cells grown in culture, where induction of apoptosis is achi eved through a variety of agents. We report that cell cultures in late log growth phase exhibit an increased susceptibility to apoptosis compared with cultures in early log growth phase when apoptosis is induced by sodium deo xycholate (NaDOC), anti-Fas antibody and cytosine-b-D-arabino-furanoside (A ra-C), three agents which induce apoptosis through different upstream mecha nisms. We show that this phenomenon occurs in Jurkat lymphocytes, MT-29 and HCT-116 colon epithelial cells. We also present evidence that cell density alone does not affect NaDOC-induced apoptosis, but rather that the growth media plays a key role in increased susceptibility of cells in late log gro wth phase to NaDOC-induced apoptosis. These results indicate that growth ph ase is a variable that must be controlled in order to obtain reliable apopt osis data. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.