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Metabolic reprogramming is a hallmark of cancer, including hepatocellular carcinoma (HCC). However, its role in HCC remains to be elucidated. Herein, we identified GTP cyclohydrolase 1 (GCH1), the first rate-limiting enzyme in tetrahydrobiopterin (BH4) de novo biosynthesis, as a novel metabolic regulator of HCC. GCH1 was frequently down-regulated in HCC tissues and cell lines by promoter methylation. Low GCH1 expression was associated with larger tumor size, increased tumor number, and worse prognosis in two independent cohorts of HCC patients. Functionally, GCH1 silencing promoted HCC growth in vitro and in vivo, while GCH1 overexpression exerted an opposite effect. The metabolite BH4 inhibited HCC growth in vitro and in vivo. GCH1 silencing exerted its growth-promoting effect through directly inhibiting BH4 de novo biosynthesis. Mechanistically, GCH1 silencing activated ASK1/p38 signaling; pharmacological or genetic inhibition of ASK1 or p38 abolished GCH1 silencing-induced growth-promoting effect. Further mechanistic studies found that GCH1 silencing-induced BH4 reduction resulted in an increase of intracellular superoxide anion levels in a dose-dependent manner, which mediated the activation of ASK1/p38 signaling. Collectively, our study reveals that epigenetic silencing of GCH1 promotes HCC growth by activating superoxide anion-mediated ASK1/p38 signaling via inhibiting BH4 de novo biosynthesis, suggesting that targeting GCH1/BH4 pathway may be a promising therapeutic strategy to combat HCC.

Hepatocellular carcinoma (HCC) is one of the most prevalent cancers and currently the second leading cause of cancer-related mortality worldwide. One recent study reported that lncRNA-LALR1 promotes liver regeneration, the role and underlying mechanisms of lncRNA-LALR1 in HCC remain largely unknown. In this study, we demonstrated that lncRNA-LALR1 was significantly upregulated in HCC tissues compared with adjacent tissues and high expression of lncRNA-LALR1 was associated with advanced TNM stage, poor differentiation, and distant metastasis. RNA Fluorescence in situ hybridization analysis showed lncRNA-LALR1 was expressed not only in cytoplasm but also in nucleolus. Knockdown of lncRNA-LALR1 obviously inhibited HCC cells growth and invasion in vivo and in vitro. Besides, transcriptomic analysis and subsequent confirmation revealed that lncRNA-LALR1 upregulated small nucleolar RNA SNORD72 via binding with SNORD72 and stabilized ID2 mRNA. SNORD72 was overexpressed in HCC tissues and enhanced HCC cells proliferation, colony formation and invasion. Overexpression of SNORD72 could also stabilize ID2 mRNA and rescue the inhibitory effect of silencing lncRNA-LALR1. In conclusion, lncRNA-LALR1 is highly expressed in HCC and promotes tumor growth and invasion by upregulating SNORD72 to stabilize ID2 mRNA, implying that lncRNA-LALR1 might be a novel target for intervention of HCC.

The acidic extracellular microenvironment, namely acidosis, is a biochemical hallmark of solid tumors. However, the tumorigenicity, metastatic potential, gene expression profile and chromatin accessibility of acidosis-adapted colorectal cancer cells remain unknown. The colorectal cancer cell SW620 was cultured in acidic medium (pH 6.5) for more than 3 months to be acidosis-adapted (SW620-AA). In comparison to parental cells, SW620-AA cells exhibit enhanced tumorigenicity and liver metastatic potential in vivo. Following mRNA and lncRNA expression profiling, we validated that OLMF1, NFIB, SMAD9, DGKB are upregulated, while SESN2, MAP1B, UTRN, PCDH19, IL18, LMO2, CNKSR3, GXYLT2 are downregulated in SW620-AA cells. The differentially expressed mRNAs were significantly enriched in DNA remodeling-associated pathways including HDACs deacetylate histones, SIRT1 pathway, DNA methylation, DNA bending complex, and RNA polymerase 1 chain elongation. Finally, chromatin accessibility evaluation by ATAC-sequencing revealed that the differentially opened peaks were enriched in pathways such as small cell lung cancer, pathways in cancer, ErbB signaling, endometrial cancer, and chronic myeloid leukemia, which were mainly distributed in intergenic regions and introns. These results suggest that the chromatin accessibility changes are correlated with enhanced growth and liver metastasis capacity of acid-adapted colorectal cancer cells.