BIRC5 and neoplasm: Thus, it is a possibility that the metastasizing tumor cell has a low PGC1α expression, which might be compensated by elevated levels of ClpXP that would allow respiration in metastasizing tumor cells.91 Intriguingly, a small molecule Sirt3 activator, honokiol,92 has several similar activities to knockdown of ClpXP, including decreased metastatic ability, induction of AMP kinase, decreased survivin, induction of succinate dehydrogenase, and decrease in PGC1α expression.73, 93–95 It is thus likely that tumor cell respiration requires ClpXP.