The author present whole exome sequencing data for three murine prostate cancer cell lines that are often used as a model for human prostate cancer. They detect a p53 mutation in the two tumorigenic cell lines that is absent from the third, less tumorigenic cell line. This induces the authors to speculate that this mutation might explain the differential tumorigenicity.
This is certainly an interesting observation. However, the conclusion remains speculative unless it can be shown that this mutation converts the non tumorigenic cell line in a tumorigenic one.