ABSTRACT
Oncometabolites, such as D/L-2-hydroxyglutarate (2HG), have directly been implicated in carcinogenesis; however, the underlying molecular mechanisms remain poorly understood. Here, we showed that the levels of the L-enantiomer of 2HG (L2HG) were specifically increased in colorectal cancer (CRC) tissues and cell lines compared with the D-enantiomer of 2HG (D2HG). In addition, L2HG increased the expression of ATF4 and its target genes by activating the mTOR pathway, which subsequently provided amino acids and improved the survival of CRC cells under serum deprivation. Downregulating the expression of L-2-hydroxyglutarate dehydrogenase (L2HGDH) and oxoglutarate dehydrogenase (OGDH) increased L2HG levels in CRC, thereby activating mTOR-ATF4 signaling. Furthermore, L2HGDH overexpression reduced L2HG-mediated mTOR-ATF4 signaling under hypoxia, whereas L2HGDH knockdown promoted tumor growth and amino acid metabolism in vivo. Together, these results indicate that L2HG ameliorates nutritional stress by activating the mTOR-ATF4 axis and thus could be a potential therapeutic target for CRC.
Subject(s)
Colorectal Neoplasms , TOR Serine-Threonine Kinases , Humans , TOR Serine-Threonine Kinases/genetics , TOR Serine-Threonine Kinases/metabolism , Signal Transduction , Colorectal Neoplasms/pathology , Amino Acids , Activating Transcription Factor 4/genetics , Activating Transcription Factor 4/metabolism , Alcohol Oxidoreductases/metabolismABSTRACT
Epithelial-mesenchymal transition (EMT)-a fundamental process in embryogenesis and wound healing-promotes tumor metastasis and resistance to chemotherapy. While studies have identified signaling components and transcriptional factors responsible in the TGF-ß-dependent EMT, whether and how intracellular metabolism is integrated with EMT remains to be fully elucidated. Here, we showed that TGF-ß induces reprogramming of intracellular amino acid metabolism, which is necessary to promote EMT in non-small cell lung cancer cells. Combined metabolome and transcriptome analysis identified prolyl 4-hydroxylase α3 (P4HA3), an enzyme implicated in cancer metabolism, to be upregulated during TGF-ß stimulation. Further, knockdown of P4HA3 diminished TGF-ß-dependent changes in amino acids, EMT, and tumor metastasis. Conversely, manipulation of extracellular amino acids induced EMT-like responses without TGF-ß stimulation. These results suggest a previously unappreciated requirement for the reprogramming of amino acid metabolism via P4HA3 for TGF-ß-dependent EMT and implicate a P4HA3 inhibitor as a potential therapeutic agent for cancer.
