Limits...
Inhibition of Akt activity induces the mesenchymal-to-epithelial reverting transition with restoring E-cadherin expression in KB and KOSCC-25B oral squamous cell carcinoma cells.

Hong KO, Kim JH, Hong JS, Yoon HJ, Lee JI, Hong SP, Hong SD - J. Exp. Clin. Cancer Res. (2009)

Bottom Line: Inhibition of Akt activity by PIA decreased NF-kappaB signaling, but did not affect phosphorylation of ERK, JNK, and p38 in KB and KOSCC-25B cells.In contrast, inhibition of Akt activity by PIA did not induce any changes in SIP-1/ZEB-2 expression.All of these findings suggest that Akt inhibition could induce the MErT through decreased NF-kappaB signaling and downregulation of Snail and Twist in OSCC cells.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Oral Pathology, School of Dentistry and Dental Research Institute, Seoul National University, Seoul, Korea. hongko95@hanmail.net

ABSTRACT

Background: The Akt/PKB family of kinases is frequently activated in human cancers, including oral squamous cell carcinoma (OSCC). Akt-induced epithelial-to-mesenchymal transition (EMT) involves downregulation of E-cadherin, which appears to result from upregulation of the transcription repressor Snail. Recently, it was proposed that carcinoma cells, especially in metastatic sites, could acquire the mesenchymal-to-epithelial reverting transition (MErT) in order to adapt the microenvironments and re-expression of E-cadherin be a critical indicator of MErT. However, the precise mechanism and biologic or clinical importance of the MErT in cancers have been little known. This study aimed to investigate whether Akt inhibition would restore the expression of E-cadherin and beta-catenin, reduce that of Vimentin, and induce the MErT in OSCC cells with low or negative expression of E-cadherin. We also investigate whether inhibition of Akt activity would affect the E-cadherin repressors and signaling molecules like NF-kappaB, ERK, and p38.

Methods: We screened several OSCC cell lines in order to select suitable cell line models for inducing MErT, using immunoblotting and methylation specific-PCR. We examined whether Akt inhibitor phosphatidylinositol ether lipid analogues (PIA) treatment would restore the expression of E-cadherin and beta-catenin, reduce that of Vimentin, and induce the MErT in KB and KOSCC-25B cells using RT-PCR, immunoblotting, immunofluorescence analysis, and in vitro migration assay. We also investigated whether inhibition of Akt activity would affect the E-cadherin repressors, including Snail, Twist, and SIP-1/ZEB-2 and signaling molecules like NF-kappaB, ERK, JNK, and p38 using RT-PCR, immunoblotting, and immunofluorescence analysis.

Results: Of the 7 OSCC cell lines, KB and KOSCC-25B showed constitutively activated phosphorylated Akt and low or negative expression of E-cadherin. Inhibition of Akt activity by PIA decreased NF-kappaB signaling, but did not affect phosphorylation of ERK, JNK, and p38 in KB and KOSCC-25B cells. Akt inhibition led to downregulation of Snail and Twist expression. In contrast, inhibition of Akt activity by PIA did not induce any changes in SIP-1/ZEB-2 expression. PIA treatment induced the expression of E-cadherin and beta-catenin, reduce that of Vimentin, restored their epithelial morphology of a polygonal shape, and reduced tumor cell migration in KB and KOSCC-25B cells, which was the corresponding feature of MErT.

Conclusion: All of these findings suggest that Akt inhibition could induce the MErT through decreased NF-kappaB signaling and downregulation of Snail and Twist in OSCC cells. A strategy involving Akt inhibition might be a useful therapeutic tool in controlling cancer dissemination and metastasis in oral cancer patients.

Show MeSH

Related in: MedlinePlus

A schematic representation of the proposed signaling mechanism that promotes MErT through the inhibition of Akt activity in oral cancer cells.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC2651854&req=5

Figure 7: A schematic representation of the proposed signaling mechanism that promotes MErT through the inhibition of Akt activity in oral cancer cells.

Mentions: Akt signaling has been deeply studied because Akt plays critical roles in regulating growth, proliferation, survival, metabolism, and other cellular activities [21,35]. Chua et al. [36] showed that NF-κB suppresses the expression of epithelial specific genes E-cadherin and desmoplakin and induces the expression of the mesenchymal specific gene vimentin in breast carcinoma cells. Similarly, Julian et al. [37] reported that activation of NF-κB by Akt upregulates Snail expression and induces EMT in OSCC cells, and expression of the NF-κB subunit p65 is sufficient for EMT induction. We investigated whether it could be possible in the reverse direction, which have been little known. In the present study, inhibition of Akt activity induced the MErT through interaction with NF-κB. Downregulation of NF-κB contributed to MErT. Huber et al. [38] showed that inhibition of NF-κB signaling prevents EMT in Ras-transformed epithelial cells, while activation of this pathway promotes the transition to a mesenchymal phenotype. Fig. 7 shows a schematic representation of the proposed signaling mechanism that promotes MErT through the inhibition of Akt activity in KB and KOSCC-25B cells. Additional study using NF-κB inhibitors could be needed in order to verify this proposed pathway.


Inhibition of Akt activity induces the mesenchymal-to-epithelial reverting transition with restoring E-cadherin expression in KB and KOSCC-25B oral squamous cell carcinoma cells.

Hong KO, Kim JH, Hong JS, Yoon HJ, Lee JI, Hong SP, Hong SD - J. Exp. Clin. Cancer Res. (2009)

A schematic representation of the proposed signaling mechanism that promotes MErT through the inhibition of Akt activity in oral cancer cells.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2651854&req=5

Figure 7: A schematic representation of the proposed signaling mechanism that promotes MErT through the inhibition of Akt activity in oral cancer cells.
Mentions: Akt signaling has been deeply studied because Akt plays critical roles in regulating growth, proliferation, survival, metabolism, and other cellular activities [21,35]. Chua et al. [36] showed that NF-κB suppresses the expression of epithelial specific genes E-cadherin and desmoplakin and induces the expression of the mesenchymal specific gene vimentin in breast carcinoma cells. Similarly, Julian et al. [37] reported that activation of NF-κB by Akt upregulates Snail expression and induces EMT in OSCC cells, and expression of the NF-κB subunit p65 is sufficient for EMT induction. We investigated whether it could be possible in the reverse direction, which have been little known. In the present study, inhibition of Akt activity induced the MErT through interaction with NF-κB. Downregulation of NF-κB contributed to MErT. Huber et al. [38] showed that inhibition of NF-κB signaling prevents EMT in Ras-transformed epithelial cells, while activation of this pathway promotes the transition to a mesenchymal phenotype. Fig. 7 shows a schematic representation of the proposed signaling mechanism that promotes MErT through the inhibition of Akt activity in KB and KOSCC-25B cells. Additional study using NF-κB inhibitors could be needed in order to verify this proposed pathway.

Bottom Line: Inhibition of Akt activity by PIA decreased NF-kappaB signaling, but did not affect phosphorylation of ERK, JNK, and p38 in KB and KOSCC-25B cells.In contrast, inhibition of Akt activity by PIA did not induce any changes in SIP-1/ZEB-2 expression.All of these findings suggest that Akt inhibition could induce the MErT through decreased NF-kappaB signaling and downregulation of Snail and Twist in OSCC cells.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Oral Pathology, School of Dentistry and Dental Research Institute, Seoul National University, Seoul, Korea. hongko95@hanmail.net

ABSTRACT

Background: The Akt/PKB family of kinases is frequently activated in human cancers, including oral squamous cell carcinoma (OSCC). Akt-induced epithelial-to-mesenchymal transition (EMT) involves downregulation of E-cadherin, which appears to result from upregulation of the transcription repressor Snail. Recently, it was proposed that carcinoma cells, especially in metastatic sites, could acquire the mesenchymal-to-epithelial reverting transition (MErT) in order to adapt the microenvironments and re-expression of E-cadherin be a critical indicator of MErT. However, the precise mechanism and biologic or clinical importance of the MErT in cancers have been little known. This study aimed to investigate whether Akt inhibition would restore the expression of E-cadherin and beta-catenin, reduce that of Vimentin, and induce the MErT in OSCC cells with low or negative expression of E-cadherin. We also investigate whether inhibition of Akt activity would affect the E-cadherin repressors and signaling molecules like NF-kappaB, ERK, and p38.

Methods: We screened several OSCC cell lines in order to select suitable cell line models for inducing MErT, using immunoblotting and methylation specific-PCR. We examined whether Akt inhibitor phosphatidylinositol ether lipid analogues (PIA) treatment would restore the expression of E-cadherin and beta-catenin, reduce that of Vimentin, and induce the MErT in KB and KOSCC-25B cells using RT-PCR, immunoblotting, immunofluorescence analysis, and in vitro migration assay. We also investigated whether inhibition of Akt activity would affect the E-cadherin repressors, including Snail, Twist, and SIP-1/ZEB-2 and signaling molecules like NF-kappaB, ERK, JNK, and p38 using RT-PCR, immunoblotting, and immunofluorescence analysis.

Results: Of the 7 OSCC cell lines, KB and KOSCC-25B showed constitutively activated phosphorylated Akt and low or negative expression of E-cadherin. Inhibition of Akt activity by PIA decreased NF-kappaB signaling, but did not affect phosphorylation of ERK, JNK, and p38 in KB and KOSCC-25B cells. Akt inhibition led to downregulation of Snail and Twist expression. In contrast, inhibition of Akt activity by PIA did not induce any changes in SIP-1/ZEB-2 expression. PIA treatment induced the expression of E-cadherin and beta-catenin, reduce that of Vimentin, restored their epithelial morphology of a polygonal shape, and reduced tumor cell migration in KB and KOSCC-25B cells, which was the corresponding feature of MErT.

Conclusion: All of these findings suggest that Akt inhibition could induce the MErT through decreased NF-kappaB signaling and downregulation of Snail and Twist in OSCC cells. A strategy involving Akt inhibition might be a useful therapeutic tool in controlling cancer dissemination and metastasis in oral cancer patients.

Show MeSH
Related in: MedlinePlus