Cucurbitacin B suppresses hepatocellular carcinoma progression through inducing DNA damage-dependent cell cycle arrest.

BACKGROUND: The mortality rate of liver cancer ranks third in the world, and hepatocellular carcinoma (HCC) is a malignant tumor of the digestive tract. Cucurbitacin B (CuB), a natural compound extracted from Cucurbitaceae spp., is the main active component of Chinese patent medicine the Cucurbitacin Tablet, which has been widely used in the treatment of various malignant tumors in clinics, especially HCC. PURPOSE: This study explored the role and mechanism of CuB in the suppression of liver cancer progression. METHODS: Cell Counting Kit-8 (CCK-8) and colony formation assays were used to detect the inhibitory function of CuB in Huh7, Hep3B, and Hepa1/6 hepatoma cells. Calcein-AM/propidium iodide (PI) staining and lactate dehydrogenase (LDH) measurement assays were performed to determine cell death. Mitochondrial membrane potential (Δψm) was measured, and flow cytometry was performed to evaluate cell apoptosis and cell cycle. Several techniques, such as proteomics, Western blotting (WB), and ribonucleic acid (RNA) interference, were utilized to explore the potential mechanism. The animal experiment was performed to verify the results of in vitro experiments. RESULTS: CuB significantly inhibited the growth of Huh7, Hep3B, and Hepa1/6 cells and triggered the cell cycle arrest in G2/M phage without leading to cell death, especially apoptosis. Knockdown of insulin-like growth factor 2 mRNA-binding protein 1 (IGF2BP1), a target of CuB, did not reverse CuB elicited cell cycle arrest. CuB enhanced phosphorylated ataxia telangiectasia mutated (p-ATM) and phosphorylated H2A histone family member X (γ-H2AX) levels. Moreover, CuB increased p53 and p21 levels and decreased cyclin-dependent kinase 1 (CDK1) expression, accompanied by improving phosphorylated checkpoint kinase 1 (p-CHK1) level and suppressing cell division cycle 25C (CDC25C) protein level. Interestingly, these phenomena were partly abolished by a deoxyribonucleic acid (DNA) protector methylproamine (MPA). Animal studies showed that CuB also significantly suppressed tumor growth in BALB/c mice bearing Hepa1/6 cells. In tumor tissues, CuB reduced the expression levels of proliferating cell nuclear antigen (PCNA) and γ-H2AX but did not change the terminal deoxynucleotidyl transferase deoxyuridine triphosphate (dUTP) nick-end labeling (TUNEL) level. CONCLUSION: This study demonstrated for the first time that CuB could effectively impede HCC progression by inducing DNA damage-dependent cell cycle arrest without directly triggering cell death, such as necrosis and apoptosis. The effect was achieved through ataxia telangiectasia mutated (ATM)-dependent p53-p21-CDK1 and checkpoint kinase 1 (CHK1)-CDC25C signaling pathways. These findings indicate that CuB may be used as an anti-HCC drug, when the current findings are confirmed by independent studies and after many more clinical phase 1, 2, 3, and 4 testings have been done.

YY1-mediated up-regulation of lncRNA LINC00466 facilitates glioma progression via miR-508/CHEK1.

BACKGROUND: The abnormal expression of lncRNA LINC00466 (LINC00466) has been demonstrated in several tumor types. However, the expression pattern and functions of LINC00466 in glioma remain uninvestigated. METHODS: A reverse transcriptase-polymerase chain reaction (RT-PCR) was utilized to analyze LINC00466 in human glioma tissues and cell lines. Luciferase reporter assays were performed to explore whether YY1 could bind to the promoter region of LINC00466. Cell counting kit-8, flow cytometry, colony-formation, transwell migration and invasion assays were carried out to determine the involvement of INC00466 in glioma. Luciferase assays and pulldown assays were conducted to verify the binding sites. RESULTS: We report that LINC00466 expression is increased in glioma cells and tissues. YY1 transcription factor (YY1) can bind directly to the LINC00466 promoter region. Clinical studies revealed that the elevated expression of LINC00466 is closely correlated with an advanced World Health Organization grade (p = 0.008), Karnofsky Performance Status score (p = 0.004) and a short overall survival (p = 0.0035) of glioma patients. Functional assays revealed that LINC00466 knockdown distinctly suppresses glioma cell proliferation, migration, invasion and epithelial-mesenchymal progress, and also promotes apoptosis. Moreover, dual-luciferase reporter assays indicated that LINC00466 acts as an endogenous sponge via binding to miR-508 and decreasing its expression. Luciferase assays and RT-PCR assays demonstrated that checkpoint kinase 1 (CHEK1) is a target of miR-508, and LINC00466 modulates CHEK1 levels by competing for miR-508. LINC00466 may exhibit its anti-oncogenic roles through targeting the miR-508/CHEK1 axis. CONCLUSIONS: Our findings identified a novel glioma-related long non-coding RNA, LINC00466, which may provide a potential novel prognostic and therapeutic target for glioma.