Antiproliferative effect of urolithin A, the ellagic acid-derived colonic metabolite, on hepatocellular carcinoma HepG2.2.15 cells by targeting Lin28a/let-7a axis

An abnormality in the Lin28/let-7a axis is relevant to the progression of hepatitis B virus (HBV)-positive hepatocellular carcinoma (HCC), which could be a novel therapeutic target for this malignant tumor. The present study aimed to investigate the antiproliferative and anti-invasive effects of urolithin A in a stable full-length HBV gene integrated cell line HepG2.2.15 using CCK-8 and transwell assays. The RNA and protein expressions of targets were assessed by quantitative PCR and western blot, respectively. Results revealed that urolithin A induced cytotoxicity in HepG2.2.15 cells, which was accompanied by the cleavage of caspase-3 protein and down-regulation of Bcl-2/Bax ratio. Moreover, urolithin A suppressed the protein expressions of Sp-1, Lin28a, and Zcchc11, and elevated the expression of microRNA let-7a. Importantly, urolithin A also regulated the Lin28a/let-7a axis in transient HBx-transfected HCC HepG2 cells. Furthermore, urolithin A decelerated the HepG2.2.15 cell invasion, which was involved in suppressing the let-7a downstream factors HMGA2 and K-ras. These findings indicated that urolithin A exerted the antiproliferative effect by regulating the Lin28a/let-7a axis and may be a potential supplement for HBV-infected HCC therapy.

Lin28/let-7a轴（Lin28/let-7a axis）的异常与乙型肝炎病毒（hepatitis B virus, HBV）阳性肝细胞癌（hepatocellular carcinoma, HCC）的进展密切相关，或可成为该恶性肿瘤的新型治疗靶点。本研究旨在采用CCK-8实验与Transwell实验，探究尿石素A（urolithin A）在稳定整合全长HBV基因的细胞系HepG2.2.15中的抗增殖与抗侵袭效应。通过定量聚合酶链反应（quantitative PCR）与蛋白质免疫印迹（Western Blot）分别检测靶标的RNA与蛋白质表达水平。结果显示，尿石素A可诱导HepG2.2.15细胞产生细胞毒性，伴随半胱氨酸天冬氨酸蛋白酶-3（caspase-3）的剪切活化以及Bcl-2/Bax比值的下调。此外，尿石素A可抑制Sp-1、Lin28a以及Zcchc11的蛋白质表达，并上调微小RNA let-7a（microRNA let-7a）的表达水平。值得注意的是，尿石素A还可在瞬时转染HBx的HCC HepG2细胞中调控Lin28a/let-7a轴。进一步研究表明，尿石素A可减缓HepG2.2.15细胞的侵袭能力，该效应与抑制微小RNA let-7a的下游因子HMGA2与K-ras的表达密切相关。上述研究结果证实，尿石素A可通过调控Lin28a/let-7a轴发挥抗增殖作用，有望成为HBV感染相关HCC治疗的潜在补充手段。