The present invention relates to a novel method of treating or preventing cancer as well as a novel method for diagnosing or monitoring cancer, wherein the cancer is caused by delayed entry to cellular senescence. More particularly, the present invention relates to a novel method of treating or preventing cancer, comprising a step of administering an agent selected to degrade, inhibit or downregulate Spy1 in a cell. The present invention also relates to a novel method of diagnosing or monitoring cancer, comprising the steps of treating a cell with UV radiation and measuring amounts of a Spy1 protein and a p53 protein, or a ratio thereof.
