Suppression of Akt1-β-catenin pathway in advanced prostate cancer promotes TGFβ1-mediated epithelial to mesenchymal transition and metastasis.

Akt1 is essential for the oncogenic transformation and tumor growth in various cancers. However, the precise role of Akt1 in advanced cancers is conflicting. Using a neuroendocrine TRansgenic Adenocarcinoma of the Mouse Prostate (TRAMP) model, we first show that the genetic ablation or pharmacological inhibition of Akt1 in mice blunts oncogenic transformation and prostate cancer (PCa) growth. Intriguingly, triciribine (TCBN)-mediated Akt inhibition in 25-week old, tumor-bearing TRAMP mice and Akt1 gene silencing in aggressive PCa cells enhanced epithelial to mesenchymal transition (EMT) and promoted metastasis to the lungs. Mechanistically, Akt1 suppression leads to increased expression of EMT markers such as Snail1 and N-cadherin and decreased expression of epithelial marker E-cadherin in TRAMP prostate, and in PC3 and DU145 cells. Next, we identified that Akt1 knockdown in PCa cells results in increased production of TGFβ1 and its receptor TGFβ RII, associated with a decreased expression of β-catenin. Furthermore, treatment of PCa cells with ICG001 that blocks nuclear translocation of β-catenin promoted EMT and N-cadherin expression. Together, our study demonstrates a novel role of the Akt1-β-catenin-TGFβ1 pathway in advanced PCa.

Gao F ，Alwhaibi A ，Sabbineni H ，Verma A ，Eldahshan W ，Somanath PR ... -  《-》

P21 activated kinase-1 mediates transforming growth factor β1-induced prostate cancer cell epithelial to mesenchymal transition.

Transforming growth factor beta (TGFβ) is believed to play a dual role in prostate cancer. Molecular mechanism by which TGFβ1 suppresses early prostate tumor growth and induces epithelial-to-mesenchymal transition (EMT) in advanced stages is not known. We determined if P21-activated kinase1 (Pak1), which mediates cytoskeletal remodeling is necessary for the TGFβ1 induced prostate cancer EMT. Effects of TGFβ1 on control prostate cancer PC3 and DU145 cells and those with IPA 3 and siRNA mediated Pak1 inhibition were tested for prostate tumor xenograft in vivo and EMT in vitro. TGFβ1 inhibited PC3 tumor xenograft growth via activation of P38-MAPK and caspase-3, 9. Long-term stimulation with TGFβ1 induced PC3 and DU145 cell scattering and increased expression of EMT markers such as Snail and N-cadherin through tumor necrosis factor receptor-associated factor-6 (TRAF6)-mediated activation of Rac1/Pak1 pathway. Selective inhibition of Pak1 using IPA 3 or knockdown using siRNA both significantly inhibited TGFβ1-induced prostate cancer cell EMT and expression of mesenchymal markers. Our study demonstrated that TGFβ1 induces apoptosis and EMT in prostate cancer cells via activation of P38-MAPK and Rac1/Pak1 respectively. Our results reveal the potential therapeutic benefits of targeting TGFβ1-Pak1 pathway for advanced-stage prostate cancer.

Al-Azayzih A ，Gao F ，Somanath PR 《-》

Arenobufagin inhibits prostate cancer epithelial-mesenchymal transition and metastasis by down-regulating β-catenin.

Epithelial-mesenchymal transition (EMT) plays an important role in prostate cancer (PCa) metastasis; thus, developing EMT inhibitors may be a feasible treatment for metastatic PCa. Here, we discovered that arenobufagin and four other bufadienolides suppressed PC3 cell EMT. These compounds modulated EMT marker expression with elevating E-cadherin and reducing ZEB1, vimentin and slug expression, and attenuated the migration and invasion of PC3 cells. Among these five compounds, arenobufagin exhibited the most potent activity. We found that the mRNA and protein expression of β-catenin and β-catenin/TCF4 target genes, which are related to tumor invasion and metastasis, were down-regulated after arenobufagin treatment. Overexpression of β-catenin in PC3 cells antagonized the EMT inhibition effect of arenobufagin, while silencing β-catenin with siRNA enhanced the inhibitory effect of arenobufagin on EMT. In addition, arenobufagin restrained xenograft tumor EMT, as demonstrated by decreased mesenchymal marker expression and increased epithelial marker expression, and reduced the tumor metastatic foci in lung. This study demonstrates a novel anticancer activity of arenobufagin, which inhibits PC3 cell EMT by down-regulating β-catenin, thereby reducing PCa metastasis. In addition, it also provides new evidence for the development of arenobufagin as a treatment for metastatic prostate cancer.

Chen L ，Mai W ，Chen M ，Hu J ，Zhuo Z ，Lei X ，Deng L ，Liu J ，Yao N ，Huang M ，Peng Y ，Ye W ，Zhang D ... -  《-》

Endothelial Akt1 loss promotes prostate cancer metastasis via β-catenin-regulated tight-junction protein turnover.

Gao F ，Alwhaibi A ，Artham S ，Verma A ，Somanath PR ... -  《-》

Synergistic effects of CD44 and TGF-β1 through AKT/GSK-3β/β-catenin signaling during epithelial-mesenchymal transition in liver cancer cells.

Cancer metastasis is strongly correlated with epithelial-mesenchymal transition (EMT), in which transforming growth factor-β (TGF-β) signaling plays a central role. CD44 has emerged as a cancer stem cell (CSC) marker that strongly induces EMT together with TGF-β1. This study aimed to investigate the link between high CD44 and TGF-β1 levels during EMT in HCC cell lines. FACS analysis showed high expression of CD44 in TGF-β1-positive SNU-368 cells and TGF-β1-negative SNU-354 cells. SNU-368 CD44(+) cells showed EMT through up-regulation of the AKT/GSK-3β/β-catenin pathway. By comparison, SNU-354 CD44(+) cells showed only increased N-cadherin expression, which was not accompanied by a decrease in E-cadherin expression, and also down-regulated the AKT/GSK-3β/β-catenin pathway. However, TGF-β1-stimulated SNU-354 cells (CD44/TGF-β1(+)) exhibited lower E-cadherin and higher N-cadherin expression with increased AKT/GSK-3β/β-catenin pathway activity. CD44/TGF-β1(+) SNU-354 cells also showed enhanced migration and formed larger spheres, while the TGF-β1-induced stem cell properties returned to their original state with the TGF-β1 inhibitor SB431542. SB431542-treated SNU-368 (CD44/TGF-β1(-)) cells also showed diminished N-cadherin and AKT/GSK-3β/β-catenin pathway activity and further decreased cell motility in a wound healing assay. However, CD44 knockdown in SNU-354 cells did not induce EMT even after treatment with TGF-β1. Finally, double inhibition of both CD44 and TGF-β1 further decreased migration and sphere formation more strongly than a single inhibition in SNU-368 cells. In conclusion, the current study demonstrated the synergistic interactions between CD44 and TGF-β1 in EMT induction and CSC properties through the AKT/GSK-3β/β-catenin pathway in HCC cells.

Park NR ，Cha JH ，Jang JW ，Bae SH ，Jang B ，Kim JH ，Hur W ，Choi JY ，Yoon SK ... -  《-》