| Primary liver cancer is a highly prevalent malignant tumor of the digestive system worldwide and is one of the most common malignant tumors in China.Hepatocellular carcinoma(HCC)is the most common type of primary liver cancer,accounting for approximately 75%-85% of newly diagnosed liver cancer cases,with a high mortality rate.Despite significant progress in the diagnosis and treatment of liver cancer,the prognosis for HCC remains grim.The overall 5-year survival rate for HCC is still less than 12%,and the postoperative 5-year overall survival rate is less than 40%.Recurrence and metastasis of HCC are the main factors hindering patients from achieving long-term survival.Therefore,there is an urgent need to further study the carcinogenic mechanisms of HCC and develop innovative or alternative treatments for HCC.Hepatocellular carcinoma(HCC)is a typical highly vascularized tumor,characterized by rapid growth,high invasiveness,and insensitivity to systemic chemotherapy due to tumor angiogenesis.In clinical practice,monoclonal drugs targeting vascular endothelial growth factor(VEGF)and its receptors are used to treat liver cancer patients who cannot undergo surgical resection.However,only a portion of patients achieve satisfactory results.Therefore,investigating the molecular mechanisms of angiogenesis in HCC can help provide new drug targets and treatment strategies.Recent studies have reported that mi RNA expression levels are abnormal during hypoxia,exhibiting a strong gene-driving effect on tumor angiogenesis.However,the role of mi RNA in regulating angiogenesis in the hypoxic microenvironment of liver cancer is not yet fully understood.Micro RNA(mi RNA)is a class of small non-coding RNA,usually composed of approximately 19-25 nucleotides.Mi RNAs can regulate the translation of target m RNAs by binding to the 3’UTR of target m RNAs through complete or incomplete complementary pairing,or degrade target m RNAs through complete complementary pairing recognition in any region of the target gene m RNA.Therefore,as a dynamic and reversible post-transcriptional regulatory factor,mi RNA plays an important role in many biological processes and is a research focus in cancer biology.Reports have shown that mi R-155-5p is an oncogenic mi RNA,encoded by three exons within a 13 kb region of the B-cell integration cluster gene.mi R-155-5p is highly expressed in various malignant tumors,such as HCC,lung cancer,breast cancer,and colorectal cancer,and is closely related to the occurrence and development of tumors.However,in HCC,the mechanism of mi R-155-5p regulating angiogenesis mediated by the HIF-1α signaling pathway is not yet fully understood.The aim of this study is to investigate the mechanism of mi R-155-5p promoting angiogenic phenotype transformation and tumor development in liver cancer cells.In this study,mi R-155-5p mimics were transfected into Hep G2 liver cancer cells,and through colony formation and cell viability(MTT)assays,it was found that mi R-155-5p could promote colony formation and cell viability in Hep G2 cells.Using human umbilical vein endothelial cell(HUVEC)angiogenesis assays,it was found that the supernatant of Hep G2 cells transfected with mi R-155-5p significantly promoted HUVEC cell migration,pseudopodia formation,and angiogenesis.These results indicate that overexpression of mi R-155-5p can induce proliferation and vitality of Hep G2 liver cancer cells,secrete pro-angiogenic factors,and promote tumor-associated angiogenesis.Conversely,after transfecting Hep G2 cells with mi R-155-5p inhibitor,colony formation assays,MTT assays,and angiogenesis experiments showed that mi R-155-5p inhibitor significantly inhibited Hep G2 cell proliferation and angiogenesis,suggesting that mi R-155-5p is a potential drug target.Inhibiting its expression or oncogenic function in cancer cells may become a novel strategy for treating HCC.To further explore the mechanism of mi R-155-5p in liver cancer cells,after transfecting mi R-155-5p into Hep G2 cells,this study used q PCR and western blot experiments to detect the expression levels of various proteins.Compared to the control group,the m RNA and protein levels of vascular endothelial growth factor A(VEGFA)were significantly increased,the protein level of hypoxia-inducible factor-1α(HIF-1α)was elevated,and the expression level of Von Hippel Lindau(VHL)protein was reduced.However,after transfecting the mi R-155-5p inhibitor,the expression levels of VEGFA m RNA/protein,HIF-1α,and VHL protein showed reversed changes,indicating that mi R-155-5p’s effect on Hep G2 cell proliferation is related to the angiogenesis mechanism regulated by the VHL/HIF-1α/VEGFA signaling pathway.Bromodomain-containing Protein 4 short isoform(BRD4S)is one of the important functional proteins in the BET family.Studies have reported that BRD4 S protein can bind to RNA.In this study,through EMSA experiments,it was found that recombinant BRD4 S protein can interact with biotin-labeled Biotin-mi R-155-5p in vitro.In addition,after transfecting BRD4 S into Hep G2 cells,RNA pulldown and RNA-IP experiments showed that BRD4 S can also bind to Biotin-mi R-155-5p in cells and form RNA-protein complexes.To investigate the molecular mechanism of BRD4 S binding to mi R-155-5p,this study established a Hep G2 sh BRD4 S knockdown cell line and found that knocking down BRD4 S significantly promoted Hep G2 cell proliferation and angiogenesis.However,after transfecting BRD4 S into Hep G2 cells,overexpression of BRD4 S inhibited liver cancer cell growth and angiogenesis.Furthermore,when co-transfecting mi R-155-5p and BRD4 S into Hep G2 liver cancer cells,it was found that BRD4 S could still weaken the oncogenic effect of mi R-155-5p on Hep G2 cells,suggesting that BRD4 S can inhibit the function of mi R-155-5p by binding to it.This study explored the expression of mi R-155-5p in liver cancer and its underlying oncogenic mechanisms,making it a potential biomarker for liver cancer.mi R-155-5p promotes tumor angiogenesis and growth through the VHL/HIF-1α/VEGFA signaling pathway,while BRD4 S can inhibit its function by binding to mi R-155-5p.This suggests that the inhibitory effect of BRD4 binding to mi R-155-5p on Hep G2 cell proliferation and tumor angiogenesis plays a crucial role in the process. |
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