The Hippo pathway is crucial in organ size control and tissue homeostasis, with deregulation leading to cancer. An extracellular nutrition signal, such as glucose, regulates the Hippo pathway activation. However, the mechanisms are still not clear. Here, we found that the Hippo pathway is directly regulated by the hexosamine biosynthesis pathway (HBP) in response to metabolic nutrients. Mechanistically, the core component of Hippo pathway (YAP) is O-GlcNAcylated by O-GlcNAc transferase (OGT) at serine 109. YAP O-GlcNAcylation disrupts its interaction with upstream kinase LATS1, prevents its phosphorylation, and activates its transcriptional activity. And this activation is not dependent on AMPK. We also identified OGT as a YAP-regulated gene that forms a feedback loop. Finally, we confirmed that glucose-induced YAP O-GlcNAcylation and activation promoted tumorigenesis. Together, our data establish a molecular mechanism and functional significance of the HBP in directly linking extracellular glucose signal to the Hippo-YAP pathway and tumorigenesis.

Background/Amis: Long non-coding RNAs (lncRNAs), a novel class of transcripts, have been shown to play critical roles in diverse cellular biological processes, including tumorigenesis. Small nucleolar RNA host gene 6 (SNHG6) regulates various biological processes in cancer cells. However, the biological role of SNHG6 in gastric cancer still remains to be explored. The aim of this study is to investigate the characteristic of the SNHG6 in gastric cancer. Methods: Quantitative real-time polymerase chain reaction (qRT-PCR) was used to measure the expression of SNHG6 in gastric cancer tissues and cell lines. MTT assays, colony formation assays were used to determine the impact of SNHG6 on tumorigenesis . Flow cytometric analysis of cell cycle and apoptosis was performed to measure the effect of SNHG6 on cell cycle and apoptosis rate. Transwell assay was performed to measure the effect of SNHG6 on cell migration. Western blotting and immunofuorescence were utilized to examine the effect of SNHG6 on epithelial-mesenchymal transition (EMT) of GC cells. Chromatin immunoprecipitation (ChIP), RNA immunoprecipitation (RIP), RNA-pulldown and luciferase reporter assays were employed to dissect molecular mechanisms. Results: In this study, we revealed that SNHG6 was overexpressed in gastric cancer tissues and cell lines. High expression levels of SNHG6 wereassociated with invasion depth, lymph node metastasis, distant metastasis and tumor/node/metastasis (TNM) stage, and predicted poor prognosis. Loss-of-function assays revealed that silenced SNHG6 obviously inhibited gastric cancer cell growth, weakened cell migration capacity and suppressed the EMT processes of gastric cancer cells. Additionally, ChIP, RIP, RNA-pulldown and luciferase reporter assays evidenced that SNHG6 could epigenetically silenced p27 and could competitively sponging miR-101-3p thereby regulating zinc finger E-box-binding homeobox 1 (ZEB1). Conclusion: In summary, our findings demonstrated that SNHG6 acted as an oncogene in gastric cancer cells through regulating miR-101-3p/ZEB1 at a post-transcriptional level and silencing expression at a transcriptional level by recruiting enhancer of zeste homolog 2 (EZH2) to the promoter of p27. SNHG6 might serve as a candidate prognostic biomarker and a target for novel therapies of gastric cancer patients.

SREBPs are key transcriptional regulators of lipid metabolism and cellular growth. It has been proposed that SREBP signaling regulates cellular growth through its ability to drive lipid biosynthesis. Unexpectedly, we find that loss of SREBP activity inhibits cancer cell growth and viability by uncoupling fatty acid synthesis from desaturation. Integrated lipid profiling and metabolic flux analysis revealed that cancer cells with attenuated SREBP activity maintain long-chain saturated fatty acid synthesis, while losing fatty acid desaturation capacity. We traced this defect to the uncoupling of Fatty Acid Synthase activity from SCD1-mediated desaturation. This deficiency in desaturation drives an imbalance between the saturated and monounsaturated fatty acid pools resulting in severe lipotoxicity. Importantly, replenishing the monounsaturated fatty acid pool restored growth to SREBP-inhibited cells. These studies highlight the importance of fatty acid desaturation in cancer growth and provide a novel mechanistic explanation for the role of SREBPs in cancer metabolism.