YAP prevents senescence of dermal fibroblast and inhibits melanogenesis via paracrine effect of DKK1.

Senile skin hyperpigmentation displays remarkable histopathological features of dermal aging. The crosstalk between melanocytes and dermal fibroblasts plays crucial roles in aging-related pigmentation. While senescent fibroblasts can upregulate pro-melanogenic factors, the role of anti-melanogenic factors, such as dickkopf1 (DKK1), and the upstream regulatory mechanism during aging remain obscure. This study investigated the roles of yes-associated protein (YAP) and DKK1 in the regulation of dermal fibroblast senescence and melanogenesis. Our findings demonstrated decreased YAP activity and DKK1 levels in intrinsic and extrinsic senescent fibroblasts. YAP depletion induced fibroblast senescence and downregulated the expression and secretion of DKK1, whereas YAP overexpression partially reversed the effect. The transcriptional regulation of DKK1 by YAP was supported by dual-luciferase reporter and chromatin immunoprecipitation assays. Moreover, YAP depletion in fibroblasts upregulated Wnt/ß-catenin in melanocytes and stimulated melanogenesis, which was partially rescued by the re-supplementation of DKK1. Conversely, overexpression of YAP in senescent fibroblasts decreased Wnt/ß-catenin levels in melanocytes and inhibited melanogenesis. Additionally, reduced levels of YAP and DKK1 were verified in the dermis of solar lentigines. These findings suggest that, during skin aging, epidermal pigmentation may be influenced by YAP in the dermal microenvironment via the paracrine effect of DKK1.

Jun/Fos promotes migration and invasion of hepatocellular carcinoma cells by enhancing BORIS promoter activity.

The Brother of the Regulator of Imprinted Sites (BORIS), as a specific indicator of hepatocellular carcinoma, exhibits a significant increase in expression. However, its upstream regulatory network remains enigmatic. Previous research has indicated a strong correlation between the Hippo pathway and the progression of hepatocellular carcinoma. It is well established that the Activator Protein-1 (AP-1) frequently engages in interactions with the Hippo pathway. Thus, we attempt to prove whether Jun and Fos, a major member of the AP-1 family, are involved in the regulation of BORIS expression. Bioinformatics analysis revealed the existence of binding sites for Jun and Fos within the BORIS promoter. Through a series of overexpression and knockdown experiments, we corroborated that Jun and Fos have the capacity to augment BORIS expression, thereby fostering the migration and invasion of hepatocellular carcinoma cells. Moreover, Methylation-Specific PCR and Bisulfite Sequencing PCR assays revealed that Jun and Fos do not have a significant impact on the demethylation of the BORIS promoter. However, luciferase reporter and chromatin immunoprecipitation experiments substantiated that Jun and Fos could directly bind to the BORIS promoter, thereby enhancing its transcription. In conclusion, these results suggest that Jun and Fos can promote the development of hepatocellular carcinoma by directly regulating the expression of BORIS. These findings may provide experimental evidence positioning BORIS as a novel target for the clinical intervention of hepatocellular carcinoma.

BORIS variant SF2(C2/A4) promotes the malignant development of liver cancer by activating epithelial-mesenchymal transition and hepatic stellate cells.

The underlying mechanisms of metastasis and recurrence of liver cancer remain largely unknown. Here, we found that Brother of the Regulator of Imprinted Sites (BORIS) variant SF2(C2/A4) was highly expressed in high metastatic potential hepatocellular carcinoma (HCC) cells and clinical tumor samples, related to the formation of satellite nodules. Its over expression promoted self-renewal, the expression of tumor stem cell markers, chemoresistance, wound healing rate, invasion and metastasis of HepG2 and Hep3B cells; reinforced epithelial-mesenchymal transition (EMT), decreased the expression of E-cadherin and increased N-cadherin and Vimentin. Subcellular localization experiment showed that BORIS SF2(C2/A4) was localized in nucleus and cytoplasm. Further double luciferase reporter gene experiment confirmed that it bound to TWIST1 gene promoter and significantly increased latter expression. BORIS SF2(C2/A4) knock down induced apoptosis of HCCLM3 and PLC/PRF/5 cells, and increased the protein content of cleaved caspase 3. Additionally, BORIS SF2(C2/A4) over expression increased the expression of fibroblast growth factor 2 (FGF2) in HepG2 and Hep3B cells. FGF2 expressed higher in HCC tumor tissues than in paired peri-tumor tissues, and its expression was positively correlated with BORIS SF2(C2/A4). Interestingly, high expression of FGF2 is also associated with the formation of satellite nodules. Moreover, using the medium from BORIS SF2(C2/A4) overexpressed cell lines to coculture hepatic stellate cell (HSCs) line LX-2, the latter could be activated and increased the expression of CD90 and PIGF, which is consistent with the effect of adding bFGF alone. These results indicate that BORIS SF2(C2/A4) plays a role in deterioration of liver cancer by regulating TWIST1 to induce EMT, and by FGF2 to activate HSCs.

AMPKα2/HNF4A/BORIS/GLUT4 pathway promotes hepatocellular carcinoma cell invasion and metastasis in low glucose microenviroment.

Increasing evidence has revealed that the invasion and metastasis of HCC are intimately related to the low-glucose microenvironment, but the intrinsic regulatory mechanism remains unclear. It has been well documented that AMPK regulates the transcriptional expression of GLUT4 and its catalytic subunit AMPKα2 can negatively regulate the downstream target molecule HNF4A. Meanwhile, BORIS (Brother of the Regulator of Imprinted Sites) is able to modulate the Warburg effect by regulating the splicing of pyruvate kinase M2 (PKM2), a critical enzyme in glycolysis. Through bioinformatic analysis and a series of overexpression, knockdown, and complementation experiments, we demonstrated that HNF4A can directly act on BORIS and negatively regulate its expression, thereby inhibiting hepatoma cell motility and tumor metastasis, whereas BORIS can directly act on GLUT4 and positively regulate its expression to enhance hepatoma cell motility and tumor metastasis. We also found that HNF4A agonist (Benfluorex) and GLUT4 inhibitor (antiviral drug Ritonavir) can suppress HCC cell proliferation and glucose uptake. Taken together, these results all suggest that activation of the AMPKα2/HNF4A/BORIS/GLUT4 signaling pathway in a low-glucose microenvironment can significantly promote the invasion and metastasis of HCC cells, while HNF4A and GLUT4 may have important potential applications as prognostic or drug target molecules.

Establishment and evaluation of cell and animal models expressing BORIS subfamily 2 variant.

Background: The possibility of a cancer vaccine aimed at stimulating or mobilizing the body's immune system to control and kill tumor cells is emerging as a potential new strategy for tumor immunological therapy. CCCTC-binding Factor Like (CTCFL)/Brother of the Regulator of Imprinted Sites (BORIS), a cancer-testis antigen (CTA), has 23 mRNA splice variants classified into six subfamilies (sfs) and potentially encodes 17 distinct polypeptides. Based on our previous long-term research on hepatocellular carcinoma (HCC), we were particularly interested in whether BORIS sf2 could be a promising candidate for immunotherapy targeting liver cancer cells. Therefore, in this study, we aimed to construct an animal model to study the immunogenicity of human BORIS sf2 in murine hepatoma cells. Methods: We established a hepatoma cell line expressing human BORIS sf2/C68 by inserting the sequences into a lentiviral vector pLVX-EF1α-IRES-Puro carrying the puromycin resistance gene. We achieved the stabilized expression of BORIS sf2/C68 in the oncogenic Hepa1c1c7 cells through lentivirus-mediated approach. The Hepa1c1c7 cells expressing the BORIS sf2/C68 (5×106/mouse) were inoculated subcutaneously into 6-week-old C57BL/6 mice to induce the formation of tumors. Results: In the tumor formation experiment, the murine hepatoma cells expressing human BORIS sf2/C68 showed progressive growth in C57BL/6 mice. The animal model we constructed could be used to study the in vivo immunogenicity of the human BORIS sf2 in murine hepatoma cells. Conclusions: The animals bearing BORIS sf2/C68-positive tumors may serve as an animal model for studying the therapeutic potency and safety of HCC vaccine directed at the CT-antigen BORIS sf2.