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DACT1, an antagonist to Wnt/β-catenin signaling, suppresses tumor cell growth and is frequently silenced in breast cancer.

Yin X, Xiang T, Li L, Su X, Shu X, Luo X, Huang J, Yuan Y, Peng W, Oberst M, Kelly K, Ren G, Tao Q - Breast Cancer Res. (2013)

Bottom Line: We found that DACT1 expression was silenced in eight (88.9%) of nine breast cancer cell lines, and its protein levels were obviously reduced in breast tumors compared with paired surgical-margin tissues.Functional assays showed that ectopic expression of DACT1 could inhibit breast tumor cell proliferation in vivo and in vitro through inducing apoptosis, and further suppress tumor cell migration through antagonizing the Wnt/β-catenin signaling pathway.Our study demonstrates that DACT1 could function as a tumor suppressor but was frequently downregulated in breast cancer.

View Article: PubMed Central - HTML - PubMed

ABSTRACT

Introduction: Aberrant activation of Wnt/β-catenin signaling plays an important role in the pathogenesis of breast cancer. DACT1 (Dapper/Frodo) has been identified as involved in antagonizing Wnt/β-catenin signaling through interacting with Dishevelled (Dvl), a central mediator of Wnt signaling, whereas its role in breast tumorigenesis remains unclear.

Methods: We examined DACT1 expression in breast cancer cell lines and primary tumors with semiquantitative or quantitative RT-PCR and immunochemistry, and further evaluated the promoter methylation of DACT1 with methylation-specific PCR (MSP). We also explored the tumor-suppressive functions of DACT1 in vivo and in vitro, and its related mechanism in breast cancer.

Results: We identified DACT1 as a methylated target in our breast cancer epigenome study. Here, we further investigated DACT1 expression in multiple breast cell lines and primary tumors, and further studied its function and molecular mechanisms. We found that DACT1 expression was silenced in eight (88.9%) of nine breast cancer cell lines, and its protein levels were obviously reduced in breast tumors compared with paired surgical-margin tissues. Promoter CpG methylation of DACT1 was detected in five (55.6%) of nine breast cancer cell lines and 40 (29.9%) of 134 primary tumors, but not in surgical-margin tissues and normal breast tissues. Demethylation treatment of breast cancer cell lines restored DACT1 expression along with promoter demethylation, suggesting that an epigenetic mechanism mediates DACT1 silencing in breast cancer. Functional assays showed that ectopic expression of DACT1 could inhibit breast tumor cell proliferation in vivo and in vitro through inducing apoptosis, and further suppress tumor cell migration through antagonizing the Wnt/β-catenin signaling pathway.

Conclusions: Our study demonstrates that DACT1 could function as a tumor suppressor but was frequently downregulated in breast cancer.

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DACT1 was downregulated in primary breast tumors. (A) Analysis of DACT1 expression in normal breast tissues and primary breast tumors by using real-time PCR. (B) Representative immunohistochemical (IHC) staining for DACT1 in paired breast tumors and surgical-margin tissues. Magnification, 400×. (C) The mean optical density of DACT1 expression in each case (left panel). Quantitative analysis of DACT1 expression density is shown as values of mean ± SD (right panel). ***P < 0.001. (D, E) GSA-tumor analysis of DACT1 by using the 1,881-sample breast cancer data set. Box plot of DACT1 expression for tumor samples stratified according to Hu subtypes, ER status, and histologic grade.
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Figure 2: DACT1 was downregulated in primary breast tumors. (A) Analysis of DACT1 expression in normal breast tissues and primary breast tumors by using real-time PCR. (B) Representative immunohistochemical (IHC) staining for DACT1 in paired breast tumors and surgical-margin tissues. Magnification, 400×. (C) The mean optical density of DACT1 expression in each case (left panel). Quantitative analysis of DACT1 expression density is shown as values of mean ± SD (right panel). ***P < 0.001. (D, E) GSA-tumor analysis of DACT1 by using the 1,881-sample breast cancer data set. Box plot of DACT1 expression for tumor samples stratified according to Hu subtypes, ER status, and histologic grade.

Mentions: DACT1 expression in primary breast tumors was further examined at the RNA and protein levels. We found that DACT1 mRNA was obviously downregulated in breast cancer tissues, compared with normal breast tissues (*P < 0.01), as measured with qPCR (Figure 2A). IHC was then performed to examine DACT1 expression in 30 cases of primary tumors and paired surgical-margin tissues (Figure 2B). An IPP system showed that the mean optical density of DACT1 protein expression was significantly decreased in primary breast tumors (0.222 ± 0.060), compared with that in surgical-margin tissues (0.287 ± 0.054) (***P < 0.001) (Figure 2C).


DACT1, an antagonist to Wnt/β-catenin signaling, suppresses tumor cell growth and is frequently silenced in breast cancer.

Yin X, Xiang T, Li L, Su X, Shu X, Luo X, Huang J, Yuan Y, Peng W, Oberst M, Kelly K, Ren G, Tao Q - Breast Cancer Res. (2013)

DACT1 was downregulated in primary breast tumors. (A) Analysis of DACT1 expression in normal breast tissues and primary breast tumors by using real-time PCR. (B) Representative immunohistochemical (IHC) staining for DACT1 in paired breast tumors and surgical-margin tissues. Magnification, 400×. (C) The mean optical density of DACT1 expression in each case (left panel). Quantitative analysis of DACT1 expression density is shown as values of mean ± SD (right panel). ***P < 0.001. (D, E) GSA-tumor analysis of DACT1 by using the 1,881-sample breast cancer data set. Box plot of DACT1 expression for tumor samples stratified according to Hu subtypes, ER status, and histologic grade.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3672711&req=5

Figure 2: DACT1 was downregulated in primary breast tumors. (A) Analysis of DACT1 expression in normal breast tissues and primary breast tumors by using real-time PCR. (B) Representative immunohistochemical (IHC) staining for DACT1 in paired breast tumors and surgical-margin tissues. Magnification, 400×. (C) The mean optical density of DACT1 expression in each case (left panel). Quantitative analysis of DACT1 expression density is shown as values of mean ± SD (right panel). ***P < 0.001. (D, E) GSA-tumor analysis of DACT1 by using the 1,881-sample breast cancer data set. Box plot of DACT1 expression for tumor samples stratified according to Hu subtypes, ER status, and histologic grade.
Mentions: DACT1 expression in primary breast tumors was further examined at the RNA and protein levels. We found that DACT1 mRNA was obviously downregulated in breast cancer tissues, compared with normal breast tissues (*P < 0.01), as measured with qPCR (Figure 2A). IHC was then performed to examine DACT1 expression in 30 cases of primary tumors and paired surgical-margin tissues (Figure 2B). An IPP system showed that the mean optical density of DACT1 protein expression was significantly decreased in primary breast tumors (0.222 ± 0.060), compared with that in surgical-margin tissues (0.287 ± 0.054) (***P < 0.001) (Figure 2C).

Bottom Line: We found that DACT1 expression was silenced in eight (88.9%) of nine breast cancer cell lines, and its protein levels were obviously reduced in breast tumors compared with paired surgical-margin tissues.Functional assays showed that ectopic expression of DACT1 could inhibit breast tumor cell proliferation in vivo and in vitro through inducing apoptosis, and further suppress tumor cell migration through antagonizing the Wnt/β-catenin signaling pathway.Our study demonstrates that DACT1 could function as a tumor suppressor but was frequently downregulated in breast cancer.

View Article: PubMed Central - HTML - PubMed

ABSTRACT

Introduction: Aberrant activation of Wnt/β-catenin signaling plays an important role in the pathogenesis of breast cancer. DACT1 (Dapper/Frodo) has been identified as involved in antagonizing Wnt/β-catenin signaling through interacting with Dishevelled (Dvl), a central mediator of Wnt signaling, whereas its role in breast tumorigenesis remains unclear.

Methods: We examined DACT1 expression in breast cancer cell lines and primary tumors with semiquantitative or quantitative RT-PCR and immunochemistry, and further evaluated the promoter methylation of DACT1 with methylation-specific PCR (MSP). We also explored the tumor-suppressive functions of DACT1 in vivo and in vitro, and its related mechanism in breast cancer.

Results: We identified DACT1 as a methylated target in our breast cancer epigenome study. Here, we further investigated DACT1 expression in multiple breast cell lines and primary tumors, and further studied its function and molecular mechanisms. We found that DACT1 expression was silenced in eight (88.9%) of nine breast cancer cell lines, and its protein levels were obviously reduced in breast tumors compared with paired surgical-margin tissues. Promoter CpG methylation of DACT1 was detected in five (55.6%) of nine breast cancer cell lines and 40 (29.9%) of 134 primary tumors, but not in surgical-margin tissues and normal breast tissues. Demethylation treatment of breast cancer cell lines restored DACT1 expression along with promoter demethylation, suggesting that an epigenetic mechanism mediates DACT1 silencing in breast cancer. Functional assays showed that ectopic expression of DACT1 could inhibit breast tumor cell proliferation in vivo and in vitro through inducing apoptosis, and further suppress tumor cell migration through antagonizing the Wnt/β-catenin signaling pathway.

Conclusions: Our study demonstrates that DACT1 could function as a tumor suppressor but was frequently downregulated in breast cancer.

Show MeSH
Related in: MedlinePlus