Abstract
BackgroundY-box binding protein-1 is an evolutionary conserved transcription and translation regulating protein that is overexpressed in various human malignancies, including breast cancer. Despite reports of YB-1 and its association with distant spread of breast cancer, the intrinsic mechanism underlying this observation remains elusive. This study investigates the role of YB-1 in mediating metastasis in highly invasive breast cancer cell lines.MethodsSilencing the YBX1 gene (which encodes the YB-1 protein) by small interfering RNA (siRNA) was performed in MDA-MB-231 and Hs578T breast cancer cell lines, followed by phenotypic assays including cell migration and invasion assays. Gene expression profiling using Affymetrix GeneChip® Human Transcriptome 2.0 array was subsequently carried out in YB-1 silenced MDA-MB-231 cells. Overexpression and silencing of YBX1 were performed to assess the expression of CORO1C, one of the differentially regulated genes from the transcriptomic analysis. A Gaussia luciferase reporter assay was used to determine if CORO1C is a putative YB-1 downstream target. siRNA-mediated silencing of CORO1C and down-regulation of YBX1 in CORO1C overexpressing MDA-MB-231 cells were performed to evaluate cell migration and invasion.ResultsDownregulation of the YB-1 protein inhibited cell migration and invasion in MDA-MB-231 breast cancer cells. Global gene expression profiling in the YBX1 silenced MDA-MB-231 cells identified differential expression of several genes, including CORO1C (which encodes for an actin binding protein, coronin-1C) as a potential downstream target of YB-1. While knockdown of YBX1 gene decreased CORO1C gene expression, the opposite effects were seen in YB-1 overexpressing cells. Subsequent verification using the reporter assay revealed that CORO1C is an indirect downstream target of YB-1. Silencing of CORO1C by siRNA in MDA-MB-231 cells was also observed to reduce cell migration and invasion. Silencing of YBX1 caused a similar reduction in CORO1C expression, concomitant with a significant decrease in migration in Hs578T cells. In coronin-1C overexpressing MDA-MB-231 cells, increased migration and invasion were abrogated by YB-1 knockdown.ConclusionIt would appear that YB-1 could regulate cell invasion and migration via downregulation of its indirect target coronin-1C. The association between YB-1 and coronin-1C offers a novel approach by which metastasis of breast cancer cells could be targeted and abrogated.
Highlights
Y-box binding protein-1 is an evolutionary conserved transcription and translation regulating protein that is overexpressed in various human malignancies, including breast cancer
We show for the first time that Y-box binding protein-1 (YB-1) could regulate cell invasion and migration, possibly via regulation of its downstream target coronin-1C
There was a concomitant and significant decline in cell migration (42.3%) (Fig. 2c), but not cell invasion (Fig. 2d) when compared to siRNA was used as the negative control (siNeg) cells, a downward trend was observed for cell invasion upon YBX1 silencing
Summary
Y-box binding protein-1 is an evolutionary conserved transcription and translation regulating protein that is overexpressed in various human malignancies, including breast cancer. Breast cancer is the leading cancer that affects women around the world, where the majority of deaths due to this dreaded disease could be attributed to metastasis. The World Health Organisation (WHO) has ranked breast cancer as the most common cause of cancerrelated deaths in women in 2012, accounting for approximately 14.3% of cancer-related mortality in less developed countries [1]. It is estimated that approximately 10–15% of breast cancer patients, show evidence of distant metastasis within 3 years from the initial detection of the primary tumour [3]. In some breast cancer patients, metastasis occurs after 10 years from the initial presentation of the primary tumour [4]. The heterogeneous nature of breast cancer makes it difficult for identification of patients who are at risk of developing metastasis
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