For example, the invention provides methods for inducing apoptosis comprising exposing a mammalian cell, such as a cancer cell, to CPT-11 and one or more Apo-2 ligand receptor agonists wherein CPT-11 is administered prior to the Apo-2 ligand receptor agonist(s) to pre-treat the cells. [0021] The cells may be in cell culture or in a mammal, e.g. a mammal suffering from cancer or a condition in whic