Mutated p53 genes have been identified in more than one-half of all human tumor cells.
This discovery is not surprising in light of the multiple roles that the p53 protein plays at the G1 checkpoint.
A cell with a faulty p53 may fail to detect errors present in the genomic DNA .
Even if a partially-functional p53 does identify the mutations, it may no longer be able to signal the necessary DNA repair enzymes. Either way, damaged DNA will remain uncorrected.
At this point, a functional p53 will deem the cell unsalvageable and trigger programmed cell death (apoptosis).
The damaged version of p53 found in cancer cells, however, cannot trigger apoptosis.