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Abstract：
Breast cancer is one of the most common malignant tumors with high mortality due to metastases. SCRIB, a scaffold protein mainly distributed in the cell membrane, is a potential tumor suppressor. Mislocalization and aberrant expression of SCRIB stimulate the EMT pathway and promote tumor cell metastasis. SCRIB has two isoforms (with or without exon 16) produced by alternative splicing. In this study we investigated the function of SCRIB isoforms in breast cancer metastasis and their regulatory mechanisms. We showed that in contrast to the full-length isoform (SCRIB-L), the truncated SCRIB isoform (SCRIB-S) was overexpressed in highly metastatic MDA-MB-231 cells that promoted breast cancer metastasis through activation of the ERK pathway. The affinity of SCRIB-S for the catalytic phosphatase subunit PPP1CA was lower than that of SCRIB-L and such difference might contribute to the different function of the two isoforms in cancer metastasis. By conducting CLIP, RIP and MS2-GFP-based experiments, we revealed that the heterogeneous nuclear ribonucleoprotein A1 (hnRNP A1) promoted SCRIB exon 16 skipping by binding to the \"AG\"-rich sequence \"caggauggaggccccccgugccgag\" on intron 15 of SCRIB. Transfection of MDA-MB-231 cells with a SCRIB antisense oligodeoxynucleotide (ASO-SCRIB) designed on the basis of this binding sequence, not only effectively inhibited the binding of hnRNP A1 to SCRIB pre-mRNA and suppressed the production of SCRIB-S, but also reversed the activation of the ERK pathway by hnRNP A1 and inhibited the metastasis of breast cancer. This study provides a new potential target and a candidate drug for treating breast cancer.
摘要：
乳腺癌是最常见的恶性肿瘤之一，由于转移而导致高死亡率。SCRIB,一种主要分布在细胞膜上的支架蛋白,是一种潜在的肿瘤抑制因子.SCRIB的错误定位和异常表达刺激EMT通路并促进肿瘤细胞转移。SCRIB具有通过可变剪接产生的两个同种型(具有或不具有外显子16)。在这项研究中，我们研究了SCRIB亚型在乳腺癌转移中的功能及其调节机制。我们表明，与全长同工型(SCRIB-L)相比，截短的SCRIB亚型(SCRIB-S)在高转移性MDA-MB-231细胞中过度表达,通过激活ERK途径促进乳腺癌转移.SCRIB-S对催化磷酸酶亚基PPP1CA的亲和力低于SCRIB-L，这种差异可能导致两种同工型在癌症转移中的不同功能。通过进行CLIP，基于RIP和MS2-GFP的实验，我们发现，异质核核糖核蛋白A1（hnRNPA1）通过与SCRIB内含子15上的富含“AG”的序列“caggauggaggcccccccgugcgag”结合来促进SCRIB外显子16的跳跃。用基于该结合序列设计的SCRIB反义寡脱氧核苷酸（ASO-SCRIB）转染MDA-MB-231细胞，不仅有效抑制hnRNPA1与SCRIB前mRNA的结合，而且抑制SCRIB-S的产生，而且还逆转了hnRNPA1对ERK通路的激活，抑制了乳腺癌的转移。本研究为乳腺癌的治疗提供了新的潜在靶点和候选药物。
