SIRT4 and prostate cancer: The second hypothesis is based on the observation that atypical activation of serine/threonine kinase in mammalian target of rapamycin complex 1 (mTORC1) controls GDH activity by inhibiting SIRT4 expression, thereby stimulating glutamine uptake, not only in MEFs, but also in human epithelial tumor cell lines [colon cancer (DLD1) and prostate cancer (DU14)].