Werbajh S E, Urtreger A J, Puricelli L I, de Lustig E S, Bal de Kier Joffé E, Kornblihtt A R
Departamento de Ciencias Biológicas, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Argentina.
FEBS Lett. 1998 Dec 4;440(3):277-81. doi: 10.1016/s0014-5793(98)01473-2.
Silencing of fibronectin (FN) expression seems to be one of the key mechanisms underlying metastatic behaviour. An inverse correlation exists between FN expression levels and the metastatic potential of two related murine mammary adenocarcinomas, M3 and MM3. Primary cultures of M3 tumour, which is moderately metastatic to lung (40% incidence), show a conspicuous FN extracellular matrix (ECM) and high levels of FN mRNA, while primary cultures of the highly metastatic MM3 tumour (95% lung incidence) are negative for FN in immunofluorescence and show at least 40-fold lower levels of FN mRNA, only detectable by RT-PCR, with a different pattern of alternatively spliced EDI isoforms compared to M3 cells. We show that the FN promoter sequence is not altered in MM3 cells. Transfection experiments with CAT constructs indicate that silencing occurs at the transcriptional level, involving the 220-bp proximal promoter region.
纤维连接蛋白（FN）表达的沉默似乎是转移行为背后的关键机制之一。在两种相关的小鼠乳腺腺癌M3和MM3中，FN表达水平与转移潜能之间存在负相关。M3肿瘤原发培养物对肺有中度转移（发生率为40%），显示出明显的FN细胞外基质（ECM）和高水平的FN mRNA，而高转移性MM3肿瘤（肺转移发生率为95%）的原发培养物在免疫荧光中对FN呈阴性，且FN mRNA水平至少低40倍，仅通过逆转录聚合酶链反应（RT-PCR）可检测到，与M3细胞相比，其可变剪接的EDI亚型模式不同。我们表明，MM3细胞中FN启动子序列未改变。用氯霉素乙酰转移酶（CAT）构建体进行的转染实验表明，沉默发生在转录水平，涉及220 bp的近端启动子区域。
