Bladder cancer aggressiveness is correlated with abnormal N-cadherin transmembrane glycoprotein expression. This protein is cleaved by the metalloprotease ADAM10 and the γ-secretase complex releasing a pro-angiogenic N-terminal fragment (NTF) and a proliferation-activating soluble C-terminal fragment (CTF2). Tetraspanin 15 (Tspan15) is identified as an ADAM10-interacting protein to induce selective N-cadherin cleavage. We first demonstrated, in invasive T24 bladder cancer cells, that N-cadherin was cleaved by ADAM10 generating NTF in the extracellular environment and leaving a membrane-anchored CTF1 fragment and that Tspan15 is required for ADAM10 to induce the selective N-cadherin cleavage. Targeting N-cadherin function in cancer is relevant to preventing tumor progression and metastases. For antitumor molecules to inhibit N-cadherin function, they should be complete and not cleaved. We first showed that the GW501516, an agonist of the nuclear receptor PPARβ/δ, decreased Tspan15 and prevented N-cadherin cleavage thus decreasing NTF. Interestingly, the drug did not modify ADAM10 expression, which was important because it could limit side effects since ADAM10 cleaves numerous substrates. By targeting Tspan15 to block ADAM10 activity on N-cadherin, GW501516 could prevent NTF pro-tumoral effects and be a promising molecule to treat bladder cancer. More interestingly, it could optimize the effects of the N-cadherin antagonists those such as ADH-1 that target the N-cadherin ectodomain.

Objective: To study the effects of miR-16-5p on proliferation, migration and invasion of osteosarcoma cells and its mechanism. Methods: Quantitative polymerase chain reaction (qPCR) and Western blotting were used to detect the mRNA and protein expression of miR-16-5p and TSPAN15 in human normal osteoblasts hFOB 1.19 and osteosarcoma cells MG63, Saos2 and HOS. The miR-16-5p or si-TSPAN15 was transfected into MG63 cells to observe its role in cell proliferation, migration and invasion. Cell proliferation was measured with MTT assay, cell migration and invasion were examined by Transwell, and the protein expression of CyclinD1, matrix metalloproteinase 2 (MMP-2), MMP-9, tetraspanin 15 (TSPAN15), phospha-tidylinositol3-kinase(p-PI3K) and phospha-protein kinase B(p-AKT) were determined by using Western blotting. The starbase website prediction combined with dual luciferase gene reporter assay was performed to analyze the targeting relationship between miR-16-5p and TSPAN15. miR-16-5p and pcDNA-TSPAN1 were co-transfected to assess the effect of high expression of TSPAN15 on overexpression of miR-16-5p-induced proliferation, migration and invasion of MG63 cells. Data comparison between the two groups was performed by using t test. Results: Compared with hFOB 1.19 cells (1.00±0.12), the expression of miR-16-5p was significantly decreased in MG63, Saos2 and HOS cells (0.32±0.05, 0.40±0.04, 0.45±0.06, respectively)(F=156.204, P<0.05), and TSPAN15 mRNA and protein levels were greatly increased (F=71.718, 110.350, both P<0.05). Overexpression of miR-16-5p obviously reduced the expression of CyclinD1, MMP-2, MMP-9 protein, cell viability, cell migration and invasion (F=150.136,117.228, 154.971, 89.479, 98.373, 130.880, all P<0.05) in MG63 cells. Knockdown of TSPAN15 greatly reduced CyclinD1, MMP-2, MMP-9 protein levels, cell survival rate, cell migration, and invasion number (F=93.206, 107.030, 109.326, 115.625, 146.113, 139.300, all P<0.05). Overexpression of miR-16-5p markedly decreased the expression of p-PI3K and p-AKT protein in MG63 cells (F=156.755, 181.419, both P<0.05). miR-16-5p targeted to regulate the expression of TSPAN15. High expression of TSPAN15 partially reversed the inhibitory effect of miR-16-5p on TSPAN15, CyclinD1, MMP-2, MMP-9, p-PI3K, p-AKT protein expression, cell viability, cell migration number and invasion number in MG63 cells. Conclusion: miR-16-5p inhibits the proliferation, migration and invasion of osteosarcoma cells by targeting the TSPAN15 gene and regulating the PI3K/AKT signaling pathway.
目的： 研究微小RNA-16-5p（miR-16-5p）对骨肉瘤细胞增殖、迁移和侵袭的影响及其作用机制。 方法： 实时荧光定量聚合酶链反应（qPCR）和蛋白质印迹法（Western blotting法）检测人正常成骨细胞hFOB 1.19和骨肉瘤细胞MG63、Saos2、HOS内miR-16-5p、四分子交联体15（TSPAN15）mRNA和蛋白表达。在MG63细胞中转染miR-16-5p或si-TSPAN15，观察其在细胞增殖、迁移和侵袭中的作用。噻唑蓝（MTT）检测细胞增殖，Transwell法检测细胞迁移和侵袭，Western blotting法检测细胞周期蛋白D1（Cyclin D1）、基质金属蛋白酶2（MMP-2）、基质金属蛋白酶9（MMP-9）、TSPAN15、磷酸化磷脂酰肌醇3激酶（p-PI3K）、磷酸化蛋白激酶B（p-AKT）蛋白表达。Starbase网站预测结合双荧光素酶基因报告实验分析miR-16-5p与TSPAN15的靶向关系。将miR-16-5p和pcDNA-TSPAN1共转染，评估高表达TSPAN15对过表达miR-16-5p诱导的MG63细胞增殖、迁移和侵袭的影响。两组间数据的比较采用t检验。 结果： 与hFOB 1.19细胞（1.00±0.12）相比，MG63、Saos2、HOS细胞中miR-16-5p表达量（分别为0.32±0.05、0.40±0.04、0.45±0.06）明显降低（F=156.204，P<0.05），TSPAN15 mRNA和蛋白水平显著提高（F=71.718、110.350，均P<0.05）。过表达miR-16-5p明显减少MG63细胞中CyclinD1、MMP-2、MMP-9蛋白表达量及细胞存活率、细胞迁移数量和侵袭数量（F=150.136、117.228、154.971、89.479、98.373、130.880，均P<0.05）。敲减TSPAN15明显降低MG63细胞中CyclinD1、MMP-2、MMP-9蛋白水平、细胞存活率、细胞迁移数量和侵袭数量（F=93.206、107.030、109.326、115.625、146.113、139.300，均P<0.05）。过表达miR-16-5p显著降低MG63细胞中p-PI3K、p-AKT蛋白表达量（F=156.755、181.419，均P<0.05）。miR-16-5p靶向调控TSPAN15的表达。高表达TSPAN15可部分逆转miR-16-5p对MG63细胞内TSPAN15、CyclinD1、MMP-2、MMP-9、p-PI3K、p-AKT蛋白表达、细胞存活率、细胞迁移数量和侵袭数量的抑制作用。 结论： miR-16-5p通过靶向TSPAN15基因并调控PI3K/AKT信号通路，从而抑制骨肉瘤细胞增殖、迁移和侵袭。.