Deregulation of lysophosphatidic acid metabolism in oral cancer promotes cell migration via the up-regulation of COX-2

The Emerging Role of LPA as an Oncometabolite

Lysophosphatidic acid (LPA) is a phospholipid that displays potent signalling activities that are regulated in both an autocrine and paracrine manner. It can be found both extra- and intracellularly, where it interacts with different receptors to activate signalling pathways that regulate a plethora of cellular processes, including mitosis, proliferation and migration. LPA metabolism is complex, and its biosynthesis and catabolism are under tight control to ensure proper LPA levels in the body. In cancer patient specimens, LPA levels are frequently higher compared to those of healthy individuals and often correlate with poor responses and more aggressive disease. Accordingly, LPA, through promoting cancer cell migration and invasion, enhances the metastasis and dissemination of tumour cells. In this review, we summarise the role of LPA in the regulation of critical aspects of tumour biology and further discuss the available pre-clinical and clinical evidence regarding the feasibility and efficacy of targeting LPA metabolism for effective anticancer therapy.

E2F7 drives autotaxin/Enpp2 transcription via chromosome looping: Repression by p53 in murine but not in human carcinomas

Dysregulation of the autotaxin (ATX, Enpp2)-lysophosphatidic acid (LPA) signaling in cancerous cells contributes to tumorigenesis and therapy resistance. We previously found that ATX activity was elevated in p53-KO mice compared to wild-type (WT) mice. Here, we report that ATX expression was upregulated in mouse embryonic fibroblasts from p53-KO and p53R172H mutant mice. ATX promoter analysis combined with yeast one-hybrid testing revealed that WT p53 directly inhibits ATX expression via E2F7. Knockdown of E2F7 reduced ATX expression and chromosome immunoprecipitation showed that E2F7 promotes Enpp2 transcription through cooperative binding to two E2F7 sites (promoter region -1393 bp and second intron 996 bp). Using chromosome conformation capture, we found that chromosome looping brings together the two E2F7 binding sites. We discovered a p53 binding site in the first intron of murine Enpp2, but not in human ENPP2. Binding of p53 disrupted the E2F7-mediated chromosomal looping and repressed Enpp2 transcription in murine cells. In contrast, we found no disruption of E2F7-mediated ENPP2 transcription via direct p53 binding in human carcinoma cells. In summary, E2F7 is a common transcription factor that upregulates ATX in human and mouse cells but is subject to steric interference by direct intronic p53 binding only in mice.

Identification and validation of transcription factor-driven enhancers of genes related to lipid metabolism in metastatic oral squamous cell carcinomas

Background

The role and mechanisms of lipid metabolism in oral squamous cell carcinomas (OSCC) metastasis have not been clarified. This study aims to identify lipid metabolism-related genes and transcription factors regulated by metastasis-associated enhancers (MAEs) in OSCC.

Methods

Gene Set Enrichment Analysis (GSEA) and Gene Set Variation Analysis (GSVA) were performed for lipid metabolism enrichment. TCGA data were used to analyze the differentially expressed lipid metabolism-related genes. MAEs were analyzed using GSE120634. Overlapping analysis was used to screen the MAE-regulated lipid metabolism-related genes, and the prognosis of these genes was analyzed. Transcription factor prediction was performed for the MAE-regulated lipid metabolism-related genes with prognostic value. Validation of the metastatic specificity of MAEs at ACAT1, OXSM and VAPA locus was performed using GSE88976 and GSE120634. ChIP-qPCR, qRT-PCR and Western blotting were used to verify the regulation of ACAT1, OXSM and VAPA expression by CBFB. Effects of CBFB knockdown on proliferation, invasion and lipid synthesis in metastatic OSCC cells were analyzed.

Results

Lipid metabolism was significantly enhanced in metastatic OSCC compared to non-metastatic OSCC. The expression of 276 lipid metabolism-related genes was significantly upregulated in metastatic OSCC, which were functionally related to lipid uptake, triacylglycerols, phospholipids and sterols metabolism. A total of 6782 MAEs and 176 MAE-regulated lipid metabolism-related genes were filtered. Three MAE-regulated lipid metabolism-related genes, ACAT1, OXSM and VAPA, were associated with a poor prognosis in OSCC patients. Enhancers at ACAT1, OXSM and VAPA locus were metastasis-specific enhancers. CBFB regulated ACAT1, OXSM and VAPA expression by binding to the enhancers of these genes. Knockdown of CBFB inhibited proliferation, invasion and lipid synthesis in metastatic OSCC cells.

Conclusion

The MAE-regulated lipid metabolism-related genes (ACAT1, OXSM and VAPA) and the key transcription factor (CBFB) were identified. CBFB knockdown inhibited proliferation, invasion and lipid synthesis of OSCC cells. These findings provide novel candidates for the development of therapeutic targets for OSCC.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12903-022-02157-7.

Design and Development of Autotaxin Inhibitors

Autotaxin (ATX) is the only enzyme of the ecto-nucleotide pyrophosphatase/phosphodiesterase (ENPP2) family with lysophospholipase D (lysoPLD) activity, which is mainly responsible for the hydrolysis of extracellular lysophosphatidylcholine (LPC) into lysophosphatidic acid (LPA). LPA can induce various responses, such as cell proliferation, migration, and cytokine production, through six G protein-coupled receptors (LPA1-6). This signaling pathway is associated with metabolic and inflammatory disorder, and inhibiting this pathway has a positive effect on the treatment of related diseases, while ATX, as an important role in the production of LPA, has been shown to be associated with the occurrence and metastasis of tumors, fibrosis and cardiovascular diseases. From mimics of ATX natural lipid substrates to the rational design of small molecule inhibitors, ATX inhibitors have made rapid progress in structural diversity and design over the past 20 years, and three drugs, GLPG1690, BBT-877, and BLD-0409, have entered clinical trials. In this paper, we will review the structure of ATX inhibitors from the perspective of the transformation of design ideas, discuss the advantages and disadvantages of each inhibitor type, and put forward prospects for the development of ATX inhibitors in the future.