ATF3 promotes the serine synthesis pathway and tumor growth under dietary serine restriction.

The serine synthesis pathway (SSP) involving metabolic enzymes phosphoglycerate dehydrogenase (PHGDH), phosphoserine aminotransferase 1 (PSAT1), and phosphoserine phosphatase (PSPH) drives intracellular serine biosynthesis and is indispensable for cancer cells to grow in serine-limiting environments. However, how SSP is regulated is not well understood. Here, we report that activating transcription factor 3 (ATF3) is crucial for transcriptional activation of SSP upon serine deprivation. ATF3 is rapidly induced by serine deprivation via a mechanism dependent on ATF4, which in turn binds to ATF4 and increases the stability of this master regulator of SSP. ATF3 also binds to the enhancers/promoters of PHGDH, PSAT1, and PSPH and recruits p300 to promote expression of these SSP genes. As a result, loss of ATF3 expression impairs serine biosynthesis and the growth of cancer cells in the serine-deprived medium or in mice fed with a serine/glycine-free diet. Interestingly, ATF3 expression positively correlates with PHGDH expression in a subset of TCGA cancer samples.

Somatic mutational landscapes of adherens junctions and their functional consequences in cutaneous melanoma development.

Cell-cell interaction in skin homeostasis is tightly controlled by adherens junctions (AJs). Alterations in such regulation lead to melanoma development. However, mutations in AJs and their functional consequences are still largely unknown. Methods: Cadherin mutations in skin cutaneous melanoma were identified using sequencing data from TCGA dataset, followed by cross-validation with data from non-TCGA cohorts. Mutations with significant occurrence were subjected to structural prediction using MODELLER and functional protein simulation using GROMACS software. Neo-antigen prediction was carried out using NetMHCpan tool. Cell-based fluorescence reporter assay was used to validate ß-catenin activity in the presence of cadherin mutations. Clinical significance was analyzed using datasets from TCGA and other non-TCGA cohorts. Targeted gene exon sequencing and immunofluorescence staining on melanoma tissues were performed to confirm the in silico findings. Results: Highly frequent mutations in type-II classical cadherins were found in melanoma with one unique recurrent mutation (S524L) in the fifth domain of CDH6, which potentially destabilizes Ca2+-binding and cell-cell contacts. Mutational co-occurrence and physical dynamics analyses placed CDH6 at the center of the top-four mutated cadherins (core CDHs; all type-II), suggesting altered heterophilic interactions in melanoma development. Mutations in the intracellular domains significantly disturbed CDH6/ß-catenin complex formation, resulting in ß-catenin translocation into cytosol or nucleus and dysregulation of canonical Wnt/ß-catenin signaling. Although mutations in core CDH genes correlated with advanced cancer stages and lymph node invasion, the overall and disease-free survival times in those patients were longer in patients with wild-type. Peptide/MHC-I binding affinity predictions confirmed overall increased neo-antigen potentials of mutated cadherins, which associated with T-lymphocyte infiltration and better clinical outcomes after immunotherapy. Conclusion: Changes in cell-cell communications by somatic mutations in AJ cadherins function as one of mechanisms to trigger melanoma development. Certain mutations in AJs may serve as potential neo-antigens which conversely benefit patients for longer survival times.

Overexpression of wild type or a Q311E mutant MB21D2 promotes a pro-oncogenic phenotype in HNSCC.

Cadherin-mediated cell-cell contacts regulated by intracellular binders play critical roles in tissue homeostasis and tumorigenesis. Here, we screened mutational profiles of 312 annotated genes involved in cadherin binding in human squamous cell carcinomas and found MB21D2 to carry a unique recurrent Q311E mutation. MB21D2 overexpression was also frequently found in head and neck cancer (HNSCC) and was associated with poor clinical outcomes. Cell-based characterizations revealed pro-oncogenic roles for MB21D2 wild-type (WT) and its Q311E mutant (Q311E) in cell proliferation, colony formation, sphere growth, and migration/invasion by promoting epithelial-mesenchymal transition. Conversely, MB21D2 knockdown in MB21D2-overexpressing cells resulted in cell growth arrest and apoptosis. Xenograft tumor models with Q311E-expressing cells formed larger and more aggressive lesions, compared to models with WT-MB21D2-expressing cells or an empty vector. Transcriptome and protein interactome analyses revealed enrichment of KRAS signaling by MB21D2 expression. Immunoblotting confirmed RAS elevation, along with upregulation/phosphorylation of PI3K, AKT, and CREB. Blocking RAS signaling in MB21D2-expressing cells by manumycin significantly reduced cell growth and survival. Our study thus defined RAS signaling-dependent pro-oncogenic roles for MB21D2 overexpression and Q311E MB21D2 expression in HNSCC development.

Phytochemical Constituents and Antimicrobial Activity of the Ethanol and Chloroform Crude Leaf Extracts of Spathiphyllum cannifolium (Dryand. ex Sims) Schott.

CONTEXT: The study investigated the medicinal properties of Spathiphyllum cannifolium (Dryand. ex Sims) Schott as a possible source of antimicrobial compounds. MATERIALS AND METHODS: The phytochemical constituents were screened using qualitative methods and the antibacterial and antifungal activities were determined using agar well diffusion method. STATISTICAL ANALYSIS: One-way analysis of variance and Fisher's least significant difference test were used. RESULTS: The phytochemical screening showed the presence of sterols, flavonoids, alkaloids, saponins, glycosides, and tannins in both ethanol and chloroform leaf extracts, but triterpenes were detected only in the ethanol leaf extract. The antimicrobial assay revealed that the chloroform leaf extract inhibited Candida albicans, Escherichia coli, Staphylococcus aureus, Bacillus subtilis, and Pseudomonas aeruginosa, whereas the ethanol leaf extract inhibited E. coli, S. aureus, and B. subtilis only. The ethanol and chloroform leaf extracts exhibited the highest zone of inhibition against B. subtilis. The antifungal assay showed that both the leaf extracts have no bioactivity against Aspergillus niger and C. albicans. CONCLUSIONS: Results suggest that chloroform is the better solvent for the extraction of antimicrobial compounds against the test organisms used in this study. Findings of this research will add new knowledge in advancing drug discovery and development in the Philippines.