CD44 alternative splicing and hnRNP A1 expression are associated with the metastasis of breast cancer
CD44 alternative splicing and hnRNP A1 expression are associated with the metastasis of breast cancer
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DOI：
10.3892/or.2015.4110
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发表时间：
2015-09-01
期刊：
影响因子：
4.2
通讯作者：
Shen, Haihong
中科院分区：
文献类型：
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作者：
Loh, Tiing Jen;Moon, Heegyum;Shen, Haihong
CD44是透明质酸的跨膜受体。CD44 pre-mRNA包含19个外显子，其中9个是选择性剪接的。在CD44剪接变异体中，v4-7变异体（v6外显子之一，包含可变外显子4,5,6和7）赋予非转移细胞转移潜力。CD44的剪接和CD44亚型的功能在乳腺癌细胞中是不同的。hnRNP A1是一种普遍表达的蛋白，在mrna前剪接中具有抑制功能。我们发现，与转移性乳腺癌细胞（MDA-MB-231）和正常乳腺细胞（MCF10A）相比，CD44v6亚型（包括所有含有v6的mRNA亚型）在非转移性乳腺癌细胞（MCF7）中的表达水平最高。此外，我们发现hnRNP A1敲低对乳腺癌细胞中CD44剪接的调节不同。我们在这里发现CD44亚型在MDA-MB-231细胞中的表达与MCF7和MCF10A细胞中的表达完全不同，而MCF7和MCF10A细胞具有相似的CD44亚型表达模式。CD44v6的RT-PCR分析显示MCF7和MCF10A细胞主要表达c5v6v7v8v9v10c6亚型。然而，除了这种异构体外，MDA-MB-231细胞还表达c5v6v8v9v10c6和c5v6c6异构体。我们还发现，敲低hnRNP A1可显著降低c5v6v7v8v9v10c6和c5v6v8v9v10c6的表达，促进c5v6c6的表达。hnRNP A1敲低显著诱导细胞死亡。此外，hnRNP A1敲低诱导MDA-MB-231细胞的细胞侵袭减少。我们的研究结果表明，hnRNP A1的敲低对乳腺癌细胞中CD44的剪接具有特异性功能。
CD44 is a transmembrane receptor for hyaluronic acid. CD44 pre-mRNA contains 19 exons, 9 of which are alternatively spliced. Among the CD44 spliced variants, the v4-7 variant, one of the v6 exon-containing isoforms that contains variable exon 4, 5, 6 and 7, confers metastatic potential to non-metastatic cells. Splicing of CD44 and the function of CD44 isoforms are different in breast cancer cells. hnRNP A1 is a ubiquitously expressed protein with an inhibitory function in pre-mRNA splicing. We showed that CD44v6 isoform, which includes all of the v6-containing mRNA isoforms, had the highest expression level in non-metatatic breast cancer cells (MCF7) when compared to the level in metastatic breast cancer cells (MDA-MB-231) and normal breast cells (MCF10A). Furthermore we showed that hnRNP A1 knockdown regulated splicing of CD44 differently in breast cancer cells. We showed here that CD44 isoform expression is completely different in MDA-MB-231 cells than that in MCF7 and MCF10A cells, whereas MCF7 and MCF10A cells had a similar expression pattern of CD44 isoforms. RT-PCR analysis of CD44v6 showed that MCF7 and MCF10A cells predominantly expressed the c5v6v7v8v9v10c6 isoform. However, in addition to this isoform, MDA-MB-231 cells also expressed the c5v6v8v9v10c6 and c5v6c6 isoforms. We also found that knockdown of hnRNP A1 significantly reduced the expression of c5v6v7v8v9v10c6 and c5v6v8v9v10c6, and promoted the expression of c5v6c6. hnRNP A1 knockdown significantly induced cell death. In addition, hnRNP A1 knockdown induced a decrease in cell invasion in the MDA-MB-231 cells. Our results indicate that the knockdown of hnRNP A1 has a specific function on the splicing of CD44 in breast cancer cells.