microRNA-449a(miR-449a)已被鉴定为几种类型的癌症中的肿瘤抑制剂。然而,miR-449a在神经母细胞瘤中的作用尚未得到深入研究.我们最近发现miR-449a的过表达显著诱导神经母细胞瘤细胞分化,提示其在神经母细胞瘤中潜在的肿瘤抑制功能。在这项研究中,我们进一步研究了miR-449a在神经母细胞瘤中的肿瘤抑制功能的潜在机制.我们观察到miR-449a通过两种机制抑制神经母细胞瘤细胞的存活和生长-诱导细胞分化和细胞周期阻滞。我们对miR-449a靶基因解剖的全面研究表明,3个新的靶标-MFAP4,PKP4和TSEN15-在介导其分化诱导功能中起重要作用。此外,我们进一步发现其诱导细胞周期停滞的功能涉及下调其直接靶标CDK6和LEF1.确定miR-449a介导的肿瘤抑制机制的临床意义,我们研究了这5个靶基因在神经母细胞瘤肿瘤标本中的表达与神经母细胞瘤患者生存的相关性。值得注意的是,我们注意到所有参与调节细胞分化的3个miR-449a靶基因的高肿瘤表达水平,但不是调控细胞周期的靶基因,与神经母细胞瘤患者的不良生存率显着相关。这些结果表明miR-449a的分化诱导功能在决定神经母细胞瘤进展中的关键作用。总的来说,我们的研究首次全面描述了miR-449a在神经母细胞瘤中的肿瘤抑制功能,并揭示miR-449a介导的肿瘤抑制通路在神经母细胞瘤预后中的潜在临床意义。
microRNA-449a (miR-449a) has been identified to function as a tumor suppressor in several types of cancers. However, the role of miR-449a in neuroblastoma has not been intensively investigated. We recently found that the overexpression of miR-449a significantly induces neuroblastoma cell differentiation, suggesting its potential tumor suppressor function in neuroblastoma. In this study, we further investigated the mechanisms underlying the tumor suppressive function of miR-449a in neuroblastoma. We observed that miR-449a inhibits neuroblastoma cell survival and growth through 2 mechanisms--inducing cell differentiation and cell cycle arrest. Our comprehensive investigations on the dissection of the target genes of miR-449a revealed that 3 novel targets- MFAP4, PKP4 and TSEN15 -play important roles in mediating its differentiation-inducing function. In addition, we further found that its function in inducing cell cycle arrest involves down-regulating its direct targets CDK6 and LEF1. To determine the clinical significance of the miR-449a-mediated tumor suppressive mechanism, we examined the correlation between the expression of these 5 target genes in neuroblastoma tumor specimens and the survival of neuroblastoma patients. Remarkably, we noted that high tumor expression levels of all the 3 miR-449a target genes involved in regulating cell differentiation, but not the target genes involved in regulating cell cycle, are significantly correlated with poor survival of neuroblastoma patients. These results suggest the critical role of the differentiation-inducing function of miR-449a in determining neuroblastoma progression. Overall, our study provides the first comprehensive characterization of the tumor-suppressive function of miR-449a in neuroblastoma, and reveals the potential clinical significance of the miR-449a-mediated tumor suppressive pathway in neuroblastoma prognosis.