MTOR and cancer: While Cdkn2a and Trp53 usually rise in tumor cells unless mutated, in malignant neoplasms, there is commonly observed a severe downregulation of the phosphatase and tensin homolog deleted on chromosome 10 (Pten), which is one of the key suppressors of the pro-oncogenic PI3K/AKT/mTOR pathway and a pivotal marker of tumor malignancy grade.