Methionine Supplementation Affects Metabolism and Reduces Tumor Aggressiveness in Liver Cancer Cells.

Liver cancer is one of the most common cancer worldwide with a high mortality. Methionine is an essential amino acid required for normal development and cell growth, is mainly metabolized in the liver, and its role as an anti-cancer supplement is still controversial. Here, we evaluate the effects of methionine supplementation in liver cancer cells. An integrative proteomic and metabolomic analysis indicates a rewiring of the central carbon metabolism, with an upregulation of the tricarboxylic acid (TCA) cycle and mitochondrial adenosine triphosphate (ATP) production in the presence of high methionine and AMP-activated protein kinase (AMPK) inhibition. Methionine supplementation also reduces growth rate in liver cancer cells and induces the activation of both the AMPK and mTOR pathways. Interestingly, in high methionine concentration, inhibition of AMPK strongly impairs cell growth, cell migration, and colony formation, indicating the main role of AMPK in the control of liver cancer phenotypes. Therefore, regulation of methionine in the diet combined with AMPK inhibition could reduce liver cancer progression.

Effectiveness of Vigna unguiculata seed extracts in preventing colorectal cancer.

Colorectal cancer (CRC) is one of the most common types of cancer, especially in Western countries, and its incidence rate is increasing every year. In this study, for the first time Vigna unguiculata L. Walp. (cowpea) water boiled seed extracts were found to reduce the viability of different colorectal cancer (CRC) cell lines, such as E705, DiFi and SW480 and the proliferation of Caco-2 line too, without affecting CCD841 healthy cell line. Furthermore, the extracts showed the ability to reduce the level of Epidermal Growth Factor Receptor (EGFR) phosphorylation in E705, DiFi and SW480 cell lines and to lower the EC50 of a CRC common drug, cetuximab, on E705 and DiFi lines from 161.7 ng mL-1 to 0.06 ng mL-1 and from 49.5 ng mL-1 to 0.2 ng mL-1 respectively. The extract was characterized in its protein and metabolite profiles by tandem mass spectrometry and 1H-NMR analyses. A Bowman-Birk protease inhibitor was identified within the protein fraction and was supposed to be the main active component. These findings confirm the importance of a legume-based diet to prevent the outbreak of many CRC and to reduce the amount of drug administered during a therapeutic cycle.

On the catalytic role of the active site residue E121 of E. coli L-aspartate oxidase.

L-aspartate oxidase (LASPO) is a flavoenzyme catalyzing the first step in the de novo biosynthesis of NAD+. The enzyme oxidizes L-aspartate both under aerobic and anaerobic conditions using oxygen as well as fumarate as electron acceptor. In accordance with its catalytic activities, LASPO displays strong primary and tertiary structure similarity with the flavin containing subunit of the proteins belonging to the succinate dehydrogenase/fumarate reductase family. The similarity extends to the active site residues, with LASPO differing from the other enzymes of the family only for the presence of a conserved glutamate (E121), which is substituted by apolar amino acids in the other enzymes. Three complementary approaches have been used to define the role of E121 in LASPO: characterization of mutants (E121A, E121Q, E121D and E121K), investigation of the catalytic activities of WT and mutants towards substrates and substrate analogues and molecular docking studies. All mutants retain fumarate reductase activity. On the contrary, all mutants lack L-aspartate oxidase activity, although retaining the ability to bind L-aspartate (except for E121K). These results and investigations on the oxidase activity towards substrate analogues suggest that the roles of E121 in catalysis include orienting L-aspartate in a productive binding mode and favouring proton abstraction from C2 by an active site base. Molecular docking studies of the substrate (L-aspartate), inhibitor (D-aspartate) and product (imino aspartate) in the active site of LASPO confirm that (a) the substrate/product energetically favoured orientation in the active site supports the conclusions reported above, (b) E121 interacts favourably with the charged amino group of the substrate and (c) different ligands might assume different orientations in the active site of the enzyme.