CDKN1B and cancer: A major consequence of the anti-apoptotic properties of p27Kip1 appeared that high levels of p27Kip1 in tumor cells might not be always good news for cancer patients: high levels of active p27Kip1 within tumor cells might indicate that although less aggressive and more slowly growing, this tumor might be more difficult to be attacked by treatment with proteasome inhibitors or other chemotherapeutic drugs.