Department of Pathology and Laboratory Medicine, UNC Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-7295, USA.
Cancer Res. 2010 Mar 1;70(5):1854-65. doi: 10.1158/0008-5472.CAN-09-1922. Epub 2010 Feb 23.
Loss of hSNF5 function is usually observed in malignant rhabdoid tumor (MRT), a highly aggressive pediatric neoplasm. Previous studies have shown that reexpression of hSNF5 in MRT cell lines causes G1 cell cycle arrest with p16(INK4A), p21(CIP1/WAF1), and cyclin D1 playing key roles in MRT cell growth control. However, we have shown that reexpression of hSNF5 induced cell cycle arrest in the absence of p16(INK4A) expression. These results indicate that the mechanism of hSNF5-induced cell cycle arrest is context dependent. Here, we investigated the relationship between p21(CIP1/WAF1) and hSNF5 in the regulation of growth using several MRT cell lines. We found that G1 cell cycle arrest occurred concomitant with an increase in p21(CIP1/WAF1) mRNA and protein levels and preceded p16(INK4A) mRNA and protein upregulation. Chromatin immunoprecipitation data confirmed that hSNF5 appeared at both p21(CIP1/WAF1) and p16(INK4A) promoters after reexpression. We further showed that p21(CIP1/WAF1) induction showed both p53-dependent and p53-independent mechanisms. We also showed that reduction of p21(CIP1/WAF1) expression by RNAi significantly inhibited hSNF5-induced G(1) arrest. Our results show that both p21(CIP1/WAF1) and p16(INK4A) are targets for hSNF5 and that p21(CIP1/WAF1) upregulation during hSNF5-induced G(1) arrest precedes p16(INK4A) upregulation. These findings indicate that SNF5 mediates a temporally controlled program of cyclin-dependent kinase inhibition to restrict aberrant proliferation in MRT cells.
hSNF5 功能丧失通常发生在恶性横纹肌样肿瘤（MRT）中，这是一种高度侵袭性的儿科肿瘤。先前的研究表明，在 MRT 细胞系中重新表达 hSNF5 会导致 G1 细胞周期停滞，p16(INK4A)、p21(CIP1/WAF1)和细胞周期蛋白 D1 在 MRT 细胞生长控制中发挥关键作用。然而，我们已经表明，在没有 p16(INK4A)表达的情况下，重新表达 hSNF5 会诱导细胞周期停滞。这些结果表明，hSNF5 诱导的细胞周期停滞的机制是上下文相关的。在这里，我们使用几种 MRT 细胞系研究了 p21(CIP1/WAF1)和 hSNF5 在生长调节中的关系。我们发现，G1 细胞周期停滞伴随着 p21(CIP1/WAF1)mRNA 和蛋白水平的增加，并且早于 p16(INK4A)mRNA 和蛋白的上调。染色质免疫沉淀数据证实，重新表达后，hSNF5 出现在 p21(CIP1/WAF1)和 p16(INK4A)启动子上。我们进一步表明，p21(CIP1/WAF1)诱导具有 p53 依赖性和 p53 非依赖性机制。我们还表明，通过 RNAi 降低 p21(CIP1/WAF1)表达显著抑制了 hSNF5 诱导的 G1 期停滞。我们的结果表明，p21(CIP1/WAF1)和 p16(INK4A)都是 hSNF5 的靶标，并且在 hSNF5 诱导的 G1 期停滞期间，p21(CIP1/WAF1)的上调早于 p16(INK4A)的上调。这些发现表明，SNF5 介导了一个受时间控制的细胞周期蛋白依赖性激酶抑制程序，以限制 MRT 细胞中的异常增殖。
