CDKN1B and ovarian carcinoma: also reported phosphorylation at the serine 10 (S10) residue of CDKN1B as an important event in mediating a role of CDKN1B in ATRA‐induced growth arrest in ovarian carcinoma cell lines.30 Phosphorylation at S10 increases the stability of CDKN1B and signals the nuclear export of CDKN1B to the cytoplasm upon cell cycle re‐entry.