Only recently the puzzle was partly solved, by showing that p27 serves as a safeguard tumor suppressor in malignancies where the axis pRB/p53, responsible for most anti-tumor mechanisms, is lacking.86 Although in these tumors p27 is unable to prevent S phase onset, it can inhibit cell division and, potentially, centrosome over-replication. The gene discussed is CDKN1B; the disease is neoplasm.