Abstract 1434: MDM2 promotes tumor cell migration through the induction of epithelial to mesenchymal transition
Authors: Zheng Lin , Wu Yeping , Zhou Tianyi , Zhu Hong , He Qiaojun , Yang Bo 
Published: August 2015

Objectives: Epithelial to mesenchymal transition (EMT), which occurs in the initiation of metastasis, offers tumor cells increased invasive properties. MDM2 overexpression has been reported to predict distant metastasis, with mechanisms undefined. The present study will investigate the role of MDM2 in regulating EMT, so as to promote the discovery and development of novel targets for anti-metastasis therapy.

Methods: (1) MDM2 expression in human ovarian adenocarcinoma tissues was examined by immunohistochemical staining; (2) SKOV3 cells were transfected with MDM2 plasmid, then the alteration of cell motility was detected using wound-healing and transwell assays; the protein and mRNA expression of E-cadherin and Slug/Snail were detected by Western Blot and real-time PCR respectively; (3) Smad2, Smad3 or Smad4 was silenced by siRNA, then E-cadherin protein expression affected by MDM2 overexpression was determined by Western Blot; (4) After transfection with MDM2 siRNA, TGF-β-triggered activation EMT and cell migration were observed; (5) The effect of MDM2 inhibitor Nutlin-3 on EMT and cell motility were observed by Western Blot and transwell assays.

Results: MDM2 expression in 123 clinical samples was examined by immunohistochemical staining, which identified a significant correlation between MDM2 expression and clinical staging. The reduction of E-cadherin protein expression, as the indicator of the occurrence of EMT, was observed in SKOV3 cells transfected with MDM2 plasmid, which led to increased cell motility. In addition, evident upregulation of Slug and Snail expression was induced by MDM2 overexpression. Smad complexes directly activate the transcription of Slug and Snail. In our study, after silencing Smad2, Smad3 or Smad4, the inhibitory effect of MDM2 on E-cadherin expression was counteracted, indicating that Smad pathway might be critical for MDM2-promoted EMT. Then we found that TGF-β-Smad-induced EMT and cell migration could be suppressed by silencing MDM2. Further investigation suggested that the MDM2 inhibitor Nutlin-3 could prevent the downregulation of E-cadherin induced by TGF-β or MDM2 overexpression through interrupting Smad activation. Additionally, Nutlin-3 exhibited inhibitory effect on cell migration, which might be owing to its antagonism on the EMT.

Conclusion: In summary, this study explored the molecular mechanisms underlying the role of MDM2 in cancer progression. MDM2 expression has been demonstrated to be closely correlated to human ovarian adenocarcinoma clinical staging, indicating the possible utilization of MDM2 in prognosis. Further study clarified MDM2 promoted tumor cell migration through the induction of EMT, which provides new theoretical evidences for the roles that MDM2 plays in tumor metastasis. Our study implicates that MDM2 may be a potential target for inhibiting metastasis and contributes to the translational research of MDM2 inhibitors as anti-metastatic agents.

Citation Format: Lin Zheng, Yeping Wu, Tianyi Zhou, Hong Zhu, Qiaojun He, Bo Yang. MDM2 promotes tumor cell migration through the induction of epithelial to mesenchymal transition. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1434. doi:10.1158/1538-7445.AM2015-1434