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DEAD-box protein p68 is regulated by β-catenin/transcription factor 4 to maintain a positive feedback loop in control of breast cancer progression.

Guturi KK, Sarkar M, Bhowmik A, Das N, Ghosh MK - Breast Cancer Res. (2014)

Bottom Line: Protein and mRNA expressions were determined by immunoblotting and quantitative RT-PCR respectively.Promoter activity of p68 was checked using luciferase assay.Furthermore, we have also established a positive feedback regulation for the expression of TCF4 by p68.

View Article: PubMed Central - PubMed

Affiliation: Signal Transduction in Cancer and Stem Cells Laboratory, Cancer Biology and Inflammatory Disorder Division, Council of Scientific and Industrial Research-Indian Institute of Chemical Biology (CSIR-IICB), 4 Raja S C Mullick Road, Jadavpur, Kolkata, 700032, India. kirankumarndkm@gmail.com.

ABSTRACT

Introduction: Nuclear accumulation of β-catenin is important for cancer development and it is found to overlap with p68 (DDX5) immunoreactivity in most breast cancers, as indicated by both clinical investigations and studies in cell lines. In this study, we aim to investigate the regulation of p68 gene expression through β-catenin/transcription factor 4 (TCF4) signaling in breast cancer.

Methods: Formalin-fixed paraffin-embedded sections derived from normal human breast and breast cancer samples were used for immunohistochemical analysis. Protein and mRNA expressions were determined by immunoblotting and quantitative RT-PCR respectively. Promoter activity of p68 was checked using luciferase assay. Occupancy of several factors on the p68 promoter was evaluated using chromatin immunoprecipitation. Finally, a syngeneic mouse model of breast cancer was used to assess physiological significance.

Results: We demonstrated that β-catenin can directly induce transcription of p68 promoter or indirectly through regulation of c-Myc in both human and mouse breast cancer cells. Moreover, by chromatin immunoprecipitation assay, we have found that both β-catenin and TCF4 occupy the endogenous p68 promoter, which is further enhanced by Wnt signaling. Furthermore, we have also established a positive feedback regulation for the expression of TCF4 by p68. To the best of our knowledge, this is the first report on β-catenin/TCF4-mediated p68 gene regulation, which plays an important role in epithelial to mesenchymal transition, as shown in vitro in breast cancer cell lines and in vivo in an animal breast tumour model.

Conclusions: Our findings indicate that Wnt/β-catenin signaling plays an important role in breast cancer progression through p68 upregulation.

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Related in: MedlinePlus

Schematic representation of β-catenin/TCF4-dependent p68 gene regulation for enhanced tumourigenesis in cancer. Based on the previous reports and data from the current study, we propose this model. β-catenin can be stabilized and activated by aberrant Wnt signaling that upregulates p68 gene expression, which in turn is involved in increasing transcription factor 4 (TCF4) gene expression and forms a positive feedback loop that ultimately leads to enhanced expression of β-catenin target genes for enhanced tumourigenesis.
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Fig8: Schematic representation of β-catenin/TCF4-dependent p68 gene regulation for enhanced tumourigenesis in cancer. Based on the previous reports and data from the current study, we propose this model. β-catenin can be stabilized and activated by aberrant Wnt signaling that upregulates p68 gene expression, which in turn is involved in increasing transcription factor 4 (TCF4) gene expression and forms a positive feedback loop that ultimately leads to enhanced expression of β-catenin target genes for enhanced tumourigenesis.

Mentions: Our study further suggests that β-catenin/TCF4 along with c-Myc upregulate p68 in breast cancer cells favouring EMT. Thus, β-catenin/TCF4 and p68 constitute a positive feedback loop essential for β-catenin-mediated processes involved in breast cancer progression. Here, we propose a model (Figure 8) indicating regulation of p68 gene expression in cancer cells by Wnt signaling through a positive feedback mechanism involving β-catenin and TCF4.Figure 8


DEAD-box protein p68 is regulated by β-catenin/transcription factor 4 to maintain a positive feedback loop in control of breast cancer progression.

Guturi KK, Sarkar M, Bhowmik A, Das N, Ghosh MK - Breast Cancer Res. (2014)

Schematic representation of β-catenin/TCF4-dependent p68 gene regulation for enhanced tumourigenesis in cancer. Based on the previous reports and data from the current study, we propose this model. β-catenin can be stabilized and activated by aberrant Wnt signaling that upregulates p68 gene expression, which in turn is involved in increasing transcription factor 4 (TCF4) gene expression and forms a positive feedback loop that ultimately leads to enhanced expression of β-catenin target genes for enhanced tumourigenesis.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4308923&req=5

Fig8: Schematic representation of β-catenin/TCF4-dependent p68 gene regulation for enhanced tumourigenesis in cancer. Based on the previous reports and data from the current study, we propose this model. β-catenin can be stabilized and activated by aberrant Wnt signaling that upregulates p68 gene expression, which in turn is involved in increasing transcription factor 4 (TCF4) gene expression and forms a positive feedback loop that ultimately leads to enhanced expression of β-catenin target genes for enhanced tumourigenesis.
Mentions: Our study further suggests that β-catenin/TCF4 along with c-Myc upregulate p68 in breast cancer cells favouring EMT. Thus, β-catenin/TCF4 and p68 constitute a positive feedback loop essential for β-catenin-mediated processes involved in breast cancer progression. Here, we propose a model (Figure 8) indicating regulation of p68 gene expression in cancer cells by Wnt signaling through a positive feedback mechanism involving β-catenin and TCF4.Figure 8

Bottom Line: Protein and mRNA expressions were determined by immunoblotting and quantitative RT-PCR respectively.Promoter activity of p68 was checked using luciferase assay.Furthermore, we have also established a positive feedback regulation for the expression of TCF4 by p68.

View Article: PubMed Central - PubMed

Affiliation: Signal Transduction in Cancer and Stem Cells Laboratory, Cancer Biology and Inflammatory Disorder Division, Council of Scientific and Industrial Research-Indian Institute of Chemical Biology (CSIR-IICB), 4 Raja S C Mullick Road, Jadavpur, Kolkata, 700032, India. kirankumarndkm@gmail.com.

ABSTRACT

Introduction: Nuclear accumulation of β-catenin is important for cancer development and it is found to overlap with p68 (DDX5) immunoreactivity in most breast cancers, as indicated by both clinical investigations and studies in cell lines. In this study, we aim to investigate the regulation of p68 gene expression through β-catenin/transcription factor 4 (TCF4) signaling in breast cancer.

Methods: Formalin-fixed paraffin-embedded sections derived from normal human breast and breast cancer samples were used for immunohistochemical analysis. Protein and mRNA expressions were determined by immunoblotting and quantitative RT-PCR respectively. Promoter activity of p68 was checked using luciferase assay. Occupancy of several factors on the p68 promoter was evaluated using chromatin immunoprecipitation. Finally, a syngeneic mouse model of breast cancer was used to assess physiological significance.

Results: We demonstrated that β-catenin can directly induce transcription of p68 promoter or indirectly through regulation of c-Myc in both human and mouse breast cancer cells. Moreover, by chromatin immunoprecipitation assay, we have found that both β-catenin and TCF4 occupy the endogenous p68 promoter, which is further enhanced by Wnt signaling. Furthermore, we have also established a positive feedback regulation for the expression of TCF4 by p68. To the best of our knowledge, this is the first report on β-catenin/TCF4-mediated p68 gene regulation, which plays an important role in epithelial to mesenchymal transition, as shown in vitro in breast cancer cell lines and in vivo in an animal breast tumour model.

Conclusions: Our findings indicate that Wnt/β-catenin signaling plays an important role in breast cancer progression through p68 upregulation.

Show MeSH
Related in: MedlinePlus