Up-regulation of bone marrow stromal protein 2 (BST2) in breast cancer with bone metastasis - PubMed (original) (raw)

Up-regulation of bone marrow stromal protein 2 (BST2) in breast cancer with bone metastasis

Dongqing Cai et al. BMC Cancer. 2009.

Abstract

Background: Bone metastases are frequent complications of breast cancer. Recent literature implicates multiple chemokines in the formation of bone metastases in breast cancer. However, the molecular mechanism of metastatic bone disease in breast cancer remains unknown. We have recently made the novel observation of the BST2 protein expression in human breast cancer cell lines. The purpose of our present study is to investigate the expression and the role of BST2 in bone metastatic breast cancer.

Methods: cDNA microarray analysis was used to compare the BST2 gene expression between a metastatic to bone human breast cancer cell line (MDA-231BO) and a primary human breast cancer cell line (MDA-231). The BST2 expression in one bone metastatic breast cancer and seven non-bone metastatic breast cancer cell lines were also determined using real-time RT-PCR and Western blot assays. We then employed tissue array to further study the BST2 expression in human breast cancer using array slides containing 20 independent breast cancer tumors that formed metastatic bone lesions, 30 non-metastasis-forming breast cancer tumors, and 8 normal breast tissues. In order to test the feasibility of utilizing BST2 as a serum marker for the presence of bone metastasis in breast cancer, we had measured the BST2 expression levels in human serums by using ELISA on 43 breast cancer patients with bone metastasis, 43 breast cancer patients without bone metastasis, and 14 normal healthy controls. The relationship between cell migration and proliferation and BST2 expression was also studied in a human breast recombinant model system using migration and FACS analysis.

Results: The microarray demonstrated over expression of the BST2 gene in the bone metastatic breast cancer cell line (MDA-231BO) compared to the primary human breast cancer cell line (MDA-231). The expression of the BST2 gene was significantly increased in the bone metastatic breast cancer cell lines and tumor tissues compared to non-bone metastatic breast cancer cell lines and tumor tissues by real time RT-PCR, Western blot and TMA. Furthermore, serum levels of BST2 measured by ELISA were also significantly higher among patients with breast cancer metastatic to bone compared to breast cancer patients without metastatic to bone (P < .0001). Most importantly, the breast cancer cell line that transfected with BST2 demonstrated increased BST2 expressions, which was associated with increased cancer cell migration and cell proliferation.

Conclusion: These results provide novel data indicating the BST2 protein expression is associated with the formation of bone metastases in human breast cancer. We believe that BST2 may be a potential biomarker in breast cancer with bone metastasis.

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Figures

Figure 1

Figure 1

Treeview of differential gene expression data from bone metastatic breast cancer cell line, MDA-231BO vs. primary breast cancer cell line, MDA-231). Treeview demonstrates the differential gene profiles in the bone metastatic breast cancer cell line compared to primary breast cancer cell line. Up-regulation is indicated by red, down-regulation by green, and no significant change by dark. Figure 1 shows 50 genes with greatest differential expression in five cDNA microarray experiments.

Figure 2

Figure 2

Real time RT-PCR demonstrates increased expression of BST2 mRNA in bone metastatic breast cancer cell line: MDA-231BO compared to non-bone metastatic breast cancer cell lines: TB-121, UACC812, MCF-7, T47D, MDA-468, BC-701, MDA-231 and normal breast cell line: MCF-10A. β-Actin was used to as a loading control.

Figure 3

Figure 3

Western blot demonstrates increased expression of the BST2 protein in bone metastatic breast cancer cell line: MDA-231BO compared to non-bone metastatic breast cancer cell lines: TB-121, UACC812, MCF-7, T47D, MDA-468, BC-701, MDA-231 and normal breast cell line: MCF-10A. β-Actin was used to as a loading control.

Figure 4

Figure 4

This figure shows the BST2 expression in human breast cancer samples as determined by tissue array. The bone metastatic breast cancer tissue (B) show the robust level of the BST2 expression, whereas the BST2 expression is absent in the non-bone metastatic breast cancer tissues (A). The brown staining in bone metastatic breast cancer cells demonstrates the significantly increased expression of BST2.

Figure 5

Figure 5

A: Before performing the cell migration and proliferation assays, protein expression of BST2 were measured by Western blot in MDA-231 cell line after transfection at 24, 36 and 48 hours with pcDNA3-BST2 (0.5 and 3 μg) and pcDNA3 empty vector (0.5 and 3 μg), respectively. Figure 5A shows that the BST2 protein expression is significantly increased by transfection with pcDNA3-BST2. β-Actin was used as a loading control. B: The graph shows that the migration activities of breast cancer cells (MDA-231) were measured at the 48-hour post-transfection with pcDNA3-BST2 (0.5 and 3 μg) and pcDNA3 empty vector (0.5 and 3 μg), respectively. Figure 5B indicates significantly increased the pcDNA3-BST2-treated cell line (MDA-231) compared to the cells treated with the empty vector (P < 0.01) (5B). C: The graph shows a FACS quantitative assessment of cells in the S phase of cell cycles in the MDA-231 cell line. Figure 5C represents the MDA-231 cell line at 24, 36 and 48-hour post-transfection with pcDNA3-BST2 (0.5 and 3 μg) and pcDNA3 empty vector (0.5 and 3 μg), respectively. The S-phase cell population significantly increased in the pcDNA3-BST2-treated cell line (MDA-231) compared to the cells treated with the empty vector (P < 0.01) (5C). These graphs show the mean values from three independent experiments.

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