Par-4 mediated Smad4 induction in PDAC cells restores canonical TGF-β/ Smad4 axis driving the cells towards lethal EMT.
Eur J Cell Biol 2020;
99:151076. [PMID:
32439219 DOI:
10.1016/j.ejcb.2020.151076]
[Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2019] [Revised: 03/20/2020] [Accepted: 03/20/2020] [Indexed: 12/22/2022] Open
Abstract
Deregulation of TGF-β signaling is intricately engrossed in the pathophysiology of pancreatic adenocarcinomas (PDACs). The role of TGF-β all through pancreatic cancer initiation and progression is multifarious and somewhat paradoxical. TGF-β plays a tumor suppressive role in early-stage pancreatic cancer by promoting apoptosis and inhibiting epithelial cell cycle progression, but incites tumor promotion in late-stage by modulating genomic instability, neo-angiogenesis, immune evasion, cell motility, and metastasis. Here, we provide evidences that Par-4 acts as one of the vital mediators to regulate TGF-β/Smad4 pathway, wherein, Par-4 induction/over-expression induced EMT which was later culminated in to apoptosis in presence of TGF-β via positive regulation of Smad4. Intriguingly, Par-4-/- cells were devoid of significant Smad4 induction compared to Par-4+/+ cells in presence of TGF-β and ectopic Par-4 steadily augmented Smad4 expression by restoring TGF-β/Smad4 axis in Panc-1 cells. Further, our FACS and western blotting results unveiled that Par-4 dragged the PDAC cells to G1 arrest in presence of TGF-β byelevating p21 and p27 levels while attenuating Cyclin E and A levels and augmenting caspase 3 cleavage triggering lethal EMT. Through restoration of Smad4, we further establish that in BxPC3 cell line (Smad4-/-), Smad4 is essential for Par-4 to indulge TGF-β dependent lethal EMT program. The mechanistic relevance of Par-4 mediated Smad4 activation was additionally validated by co-immunoprecipitation wherein disruption of NM23H1-STRAP interaction by Par-4 rescues TGF-β/Smad4 pathway in PDAC and mediates the tumor suppressive role of TGF-β, therefore serving as a vital cog to restore the apoptotic functions of TGF-β pathway.
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