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MUC4 overexpression augments cell migration and metastasis through EGFR family proteins in triple negative breast cancer cells.

Mukhopadhyay P, Lakshmanan I, Ponnusamy MP, Chakraborty S, Jain M, Pai P, Smith LM, Lele SM, Batra SK - PLoS ONE (2013)

Bottom Line: Moreover, our studies also showed that knockdown of MUC4 in TNBC cells induced molecular changes suggestive of mesenchymal to epithelial transition.We further demonstrate that MUC4 is differentially over-expressed in invasive TNBC tissues compared to normal breast tissue.MUC4 mucin expression is associated with TNBC pathobiology, and its knockdown reduced aggressiveness in vitro, and tumorigenesis and metastasis in vivo.

View Article: PubMed Central - PubMed

Affiliation: Department of Biochemistry and Molecular Biology, University of Nebraska Medical Center, Omaha, Nebraska, USA.

ABSTRACT

Introduction: Current studies indicate that triple negative breast cancer (TNBC), an aggressive breast cancer subtype, is associated with poor prognosis and an early pattern of metastasis. Emerging evidence suggests that MUC4 mucin is associated with metastasis of various cancers, including breast cancer. However, the functional role of MUC4 remains unclear in breast cancers, especially in TNBCs.

Method: In the present study, we investigated the functional and mechanistic roles of MUC4 in potentiating pathogenic signals including EGFR family proteins to promote TNBC aggressiveness using in vitro and in vivo studies. Further, we studied the expression of MUC4 in invasive TNBC tissue and normal breast tissue by immunostaining.

Results: MUC4 promotes proliferation, anchorage-dependent and-independent growth of TNBC cells, augments TNBC cell migratory and invasive potential in vitro, and enhances tumorigenicity and metastasis in vivo. In addition, our studies demonstrated that MUC4 up-regulates the EGFR family of proteins, and augments downstream Erk1/2, PKC-γ, and FAK mediated oncogenic signaling. Moreover, our studies also showed that knockdown of MUC4 in TNBC cells induced molecular changes suggestive of mesenchymal to epithelial transition. We also demonstrated in this study, for the first time, that knockdown of MUC4 was associated with reduced expression of EGFR and ErbB3 (EGFR family proteins) in TNBC cells, suggesting that MUC4 uses an alternative to ErbB2 mechanism to promote aggressiveness. We further demonstrate that MUC4 is differentially over-expressed in invasive TNBC tissues compared to normal breast tissue.

Conclusions: MUC4 mucin expression is associated with TNBC pathobiology, and its knockdown reduced aggressiveness in vitro, and tumorigenesis and metastasis in vivo. Overall, our findings suggest that MUC4 mucin promotes invasive activities of TNBC cells by altering the expression of EGFR, ErbB2, and ErbB3 molecules and their downstream signaling.

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A schematic diagram showing the contribution of MUC4 in the overall aggressiveness of TNBC cells.MUC4 maintains the sustained expression of EGFR family proteins and thereby potentiates downstream signaling events mediated through the PKC-γ and Erk1/2 signaling. MUC4 maintains sustained expression of β-catenin, which induces proliferation, tumorigenesis, migration, invasion, and metastasis.
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pone-0054455-g008: A schematic diagram showing the contribution of MUC4 in the overall aggressiveness of TNBC cells.MUC4 maintains the sustained expression of EGFR family proteins and thereby potentiates downstream signaling events mediated through the PKC-γ and Erk1/2 signaling. MUC4 maintains sustained expression of β-catenin, which induces proliferation, tumorigenesis, migration, invasion, and metastasis.

Mentions: The expression of S100A4, PDGFR, CAV1, CAV2, and many other genes was down-regulated in MUC4 knockdown cells. The S100A4 protein functions in motility, invasion, and tubulin polymerization of many cell types [59]. Chromosomal abnormalities and altered expression of S100A4 have been implicated in tumor metastasis [60]. The binding of ligands (PDGF-α, -β, -γ, and –δ) activates the intracellular kinase activity of PDGFR, and initiates intracellular signaling through the MAPK, PI3-K, and PKC-γ pathways. The down-regulation of PKC-γ upon MUC4 knockdown is in agreement with our western blot data (Figure 2C). Caveolin expression is elevated in breast cancer and associated with both primary and metastatic breast cancer [61]. CAV1 (caveolin-1), has been identified as a marker associated with a basal-like phenotype in both hereditary and sporadic breast cancer [62], and has been proposed to play a role in intracellular cholesterol trafficking [63]. A schematic of the overall study performed indicates several pathways of involvement of MUC4 in the pathogenesis of invasive TNBCs (Figure 8). Altogether, these results suggest that MUC4 modulates multiple signaling pathways that confer aggressiveness to MDA-MB-231 cells.


MUC4 overexpression augments cell migration and metastasis through EGFR family proteins in triple negative breast cancer cells.

Mukhopadhyay P, Lakshmanan I, Ponnusamy MP, Chakraborty S, Jain M, Pai P, Smith LM, Lele SM, Batra SK - PLoS ONE (2013)

A schematic diagram showing the contribution of MUC4 in the overall aggressiveness of TNBC cells.MUC4 maintains the sustained expression of EGFR family proteins and thereby potentiates downstream signaling events mediated through the PKC-γ and Erk1/2 signaling. MUC4 maintains sustained expression of β-catenin, which induces proliferation, tumorigenesis, migration, invasion, and metastasis.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3569463&req=5

pone-0054455-g008: A schematic diagram showing the contribution of MUC4 in the overall aggressiveness of TNBC cells.MUC4 maintains the sustained expression of EGFR family proteins and thereby potentiates downstream signaling events mediated through the PKC-γ and Erk1/2 signaling. MUC4 maintains sustained expression of β-catenin, which induces proliferation, tumorigenesis, migration, invasion, and metastasis.
Mentions: The expression of S100A4, PDGFR, CAV1, CAV2, and many other genes was down-regulated in MUC4 knockdown cells. The S100A4 protein functions in motility, invasion, and tubulin polymerization of many cell types [59]. Chromosomal abnormalities and altered expression of S100A4 have been implicated in tumor metastasis [60]. The binding of ligands (PDGF-α, -β, -γ, and –δ) activates the intracellular kinase activity of PDGFR, and initiates intracellular signaling through the MAPK, PI3-K, and PKC-γ pathways. The down-regulation of PKC-γ upon MUC4 knockdown is in agreement with our western blot data (Figure 2C). Caveolin expression is elevated in breast cancer and associated with both primary and metastatic breast cancer [61]. CAV1 (caveolin-1), has been identified as a marker associated with a basal-like phenotype in both hereditary and sporadic breast cancer [62], and has been proposed to play a role in intracellular cholesterol trafficking [63]. A schematic of the overall study performed indicates several pathways of involvement of MUC4 in the pathogenesis of invasive TNBCs (Figure 8). Altogether, these results suggest that MUC4 modulates multiple signaling pathways that confer aggressiveness to MDA-MB-231 cells.

Bottom Line: Moreover, our studies also showed that knockdown of MUC4 in TNBC cells induced molecular changes suggestive of mesenchymal to epithelial transition.We further demonstrate that MUC4 is differentially over-expressed in invasive TNBC tissues compared to normal breast tissue.MUC4 mucin expression is associated with TNBC pathobiology, and its knockdown reduced aggressiveness in vitro, and tumorigenesis and metastasis in vivo.

View Article: PubMed Central - PubMed

Affiliation: Department of Biochemistry and Molecular Biology, University of Nebraska Medical Center, Omaha, Nebraska, USA.

ABSTRACT

Introduction: Current studies indicate that triple negative breast cancer (TNBC), an aggressive breast cancer subtype, is associated with poor prognosis and an early pattern of metastasis. Emerging evidence suggests that MUC4 mucin is associated with metastasis of various cancers, including breast cancer. However, the functional role of MUC4 remains unclear in breast cancers, especially in TNBCs.

Method: In the present study, we investigated the functional and mechanistic roles of MUC4 in potentiating pathogenic signals including EGFR family proteins to promote TNBC aggressiveness using in vitro and in vivo studies. Further, we studied the expression of MUC4 in invasive TNBC tissue and normal breast tissue by immunostaining.

Results: MUC4 promotes proliferation, anchorage-dependent and-independent growth of TNBC cells, augments TNBC cell migratory and invasive potential in vitro, and enhances tumorigenicity and metastasis in vivo. In addition, our studies demonstrated that MUC4 up-regulates the EGFR family of proteins, and augments downstream Erk1/2, PKC-γ, and FAK mediated oncogenic signaling. Moreover, our studies also showed that knockdown of MUC4 in TNBC cells induced molecular changes suggestive of mesenchymal to epithelial transition. We also demonstrated in this study, for the first time, that knockdown of MUC4 was associated with reduced expression of EGFR and ErbB3 (EGFR family proteins) in TNBC cells, suggesting that MUC4 uses an alternative to ErbB2 mechanism to promote aggressiveness. We further demonstrate that MUC4 is differentially over-expressed in invasive TNBC tissues compared to normal breast tissue.

Conclusions: MUC4 mucin expression is associated with TNBC pathobiology, and its knockdown reduced aggressiveness in vitro, and tumorigenesis and metastasis in vivo. Overall, our findings suggest that MUC4 mucin promotes invasive activities of TNBC cells by altering the expression of EGFR, ErbB2, and ErbB3 molecules and their downstream signaling.

Show MeSH
Related in: MedlinePlus