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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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Related in: MedlinePlus

Expression and promoter methylation of DACT1 in breast cancer. (A) DACT1 expression in human normal adult and fetal tissues as detected by semiquantitative RT-PCR, with GAPDH as a control. (B) Schematic structure of the DACT1 promoter CpG island (CGI). Exon 1 (gray rectangle), CpG sites (short vertical lines), transcription start site (curved arrow), and MSP sites analyzed are indicated. (C) DACT1 was silenced by promoter methylation in breast cancer cell lines, but readily expressed in normal breast tissues. (D) Pharmacologic demethylation with Aza combined with TSA (A+T) restored DACT1 expression in breast cancer cell lines. M, methylated; U, unmethylated.
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Figure 1: Expression and promoter methylation of DACT1 in breast cancer. (A) DACT1 expression in human normal adult and fetal tissues as detected by semiquantitative RT-PCR, with GAPDH as a control. (B) Schematic structure of the DACT1 promoter CpG island (CGI). Exon 1 (gray rectangle), CpG sites (short vertical lines), transcription start site (curved arrow), and MSP sites analyzed are indicated. (C) DACT1 was silenced by promoter methylation in breast cancer cell lines, but readily expressed in normal breast tissues. (D) Pharmacologic demethylation with Aza combined with TSA (A+T) restored DACT1 expression in breast cancer cell lines. M, methylated; U, unmethylated.

Mentions: We first examined DACT1 expression in a panel of human normal adult tissues and fetal tissues, as well as breast cancer cell lines, by using semiquantitative RT-PCR. Results showed that DACT1 was widely expressed in human normal tissues and fetal tissues, including normal breast tissues (Figure 1A, C), but was frequently silenced or downregulated in breast cancer cell lines studied (Figure 1C).


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)

Expression and promoter methylation of DACT1 in breast cancer. (A) DACT1 expression in human normal adult and fetal tissues as detected by semiquantitative RT-PCR, with GAPDH as a control. (B) Schematic structure of the DACT1 promoter CpG island (CGI). Exon 1 (gray rectangle), CpG sites (short vertical lines), transcription start site (curved arrow), and MSP sites analyzed are indicated. (C) DACT1 was silenced by promoter methylation in breast cancer cell lines, but readily expressed in normal breast tissues. (D) Pharmacologic demethylation with Aza combined with TSA (A+T) restored DACT1 expression in breast cancer cell lines. M, methylated; U, unmethylated.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 1: Expression and promoter methylation of DACT1 in breast cancer. (A) DACT1 expression in human normal adult and fetal tissues as detected by semiquantitative RT-PCR, with GAPDH as a control. (B) Schematic structure of the DACT1 promoter CpG island (CGI). Exon 1 (gray rectangle), CpG sites (short vertical lines), transcription start site (curved arrow), and MSP sites analyzed are indicated. (C) DACT1 was silenced by promoter methylation in breast cancer cell lines, but readily expressed in normal breast tissues. (D) Pharmacologic demethylation with Aza combined with TSA (A+T) restored DACT1 expression in breast cancer cell lines. M, methylated; U, unmethylated.
Mentions: We first examined DACT1 expression in a panel of human normal adult tissues and fetal tissues, as well as breast cancer cell lines, by using semiquantitative RT-PCR. Results showed that DACT1 was widely expressed in human normal tissues and fetal tissues, including normal breast tissues (Figure 1A, C), but was frequently silenced or downregulated in breast cancer cell lines studied (Figure 1C).

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