Prohaptoglobin inhibits the transforming growth factor-β-induced epithelial-to-mesenchymal transition in vitro by increasing Smad1/5 activation and suppressing the Smad2/3 signaling pathway in SK-Hep1 liver cancer cells.

Abstract

Transforming growth factor-β (TGF-β) is an important inducer of the epithelial-to-mesenchymal transition (EMT) in various cancers. Our previous study demonstrated that prohaptoglobin (proHp) stimulates Smad1/5 activation via ALK1, a TGF-β type I receptor, in endothelial cells, suggesting that proHp plays a role in TGF-β signaling. However, the function of proHp in cellular events downstream of Smads remains unclear. The current study investigated the effects of proHp on TGF-β-mediated Smad-dependent EMT induction and cell invasion in vitro using proHp-overexpressing SK-Hep1 liver cancer cells. The results of Western blotting, quantitative real-time RT-PCR, and immunocytochemistry indicated that proHp downregulated expression of mesenchymal marker and EMT regulator such as N-cadherin, vimentin, and twist, and upregulated expression of the epithelial marker E-cadherin. Compared with control cells, proHp-overexpressing cells exhibited high levels of ALK1/2/3 receptors and markedly increased Smad1/5 phosphorylation. Interestingly, proHp attenuated TGF-β-induced expression of mesenchymal markers and Smad2/3 phosphorylation. It also significantly suppressed cell invasion and migration. Knockdown of Smad1/5 abolished the inhibitory effects of proHp on TGF-β-stimulated Smad2/3 phosphorylation and mesenchymal marker expression. These findings indicate that proHp suppresses the TGF-β-induced EMT and cell invasion in vitro by enhancing Smad1/5 activation via ALK1/2/3 receptors and thus suppressing the Smad2/3 signaling pathway in SK-Hep1 cells. This study suggests that proHp may prevent a de-differentiation of hepatic cells and induce a cell differentiation by regulating the Smad signaling pathway.

• Authors: Mi-Kyung Oh, Hansol Joo, In-Sook Kim
• Journal: PloS one (PLoS One) Vol. 17 Issue 5 Pg. e0266409 ( 2022) ISSN: 1932-6203 [Electronic] United States
• PMID: 35580109 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Haptoglobins
• Protein Precursors
• SMAD1 protein, human
• SMAD2 protein, human
• SMAD3 protein, human
• SMAD5 protein, human
• Smad Proteins
• Smad1 Protein
• Smad3 Protein
• Smad5 Protein
• Transforming Growth Factor beta
• prohaptoglobin

Topics

• Cell Line, Tumor
• Cell Movement
• Endothelial Cells (metabolism)
• Epithelial-Mesenchymal Transition
• Haptoglobins (metabolism)
• Humans
• Liver Neoplasms (genetics, metabolism, pathology)
• Protein Precursors (metabolism)
• Signal Transduction
• Smad Proteins (metabolism)
• Smad1 Protein (metabolism)
• Smad3 Protein (metabolism)
• Smad5 Protein (metabolism)
• Transforming Growth Factor beta (metabolism)