Survivin is a newly described apoptosis inhibitor that is expressed in many human cancers, but undetectable in terminally differentiated adult tissues. It has been shown that recombinant expression of Survivin counteracts apoptosis of B lymphocyte precursors deprived of interleukin 3 (IL-3), sμggesting a potential role of Survivin in cancer therapy. Survivin is expressed in G2-M phase in a cell cycle-dependent manner and directly associated with mitotic spindle microtubules, sμggesting a role in both apoptosis regulation and cell cycle progression.