Phosphorylation of caspase 9 (CASP9) may contribute to the suppression of apoptosis. A major inhibitory phosphorylation site in CASP9 is Thr412, which forms part of a Thr‑Pro motif (Allan LA & Clarke PR 2007; Martin MC et al. 2008). This motif is targeted by multiple proline‑directed kinases such as ERK1/2 in response to extracellular growth/survival signals or CDK1‑cyclin B1 during mitosis (Allan LA et al. 2003; Allan LA & Clarke PR 2007; Martin MC et al. 2008). Thr412 is also phosphorylated by DYRK1A, which regulates apoptosis during development (Seifert A et al. 2008).