Ubiquitin ligase RNF8 suppresses Notch signaling to regulate mammary development and tumorigenesis
Li Li, … , Anne Hakem, Razq Hakem
Li Li, … , Anne Hakem, Razq Hakem
Published September 17, 2018
Citation Information: J Clin Invest. 2018;128(10):4525-4542. https://doi.org/10.1172/JCI120401.
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Research Article Cell biology Oncology

Ubiquitin ligase RNF8 suppresses Notch signaling to regulate mammary development and tumorigenesis

Abstract

The E3 ubiquitin ligase RNF8 plays critical roles in maintaining genomic stability by promoting the repair of DNA double-strand breaks (DSBs) through ubiquitin signaling. Abnormal activation of Notch signaling and defective repair of DSBs promote breast cancer risk. Here, we found that low expression of the full-length RNF8 correlated with poor prognosis for breast cancer patients. Our data revealed that in addition to its role in the repair of DSBs, RNF8 regulated Notch1 signaling and cell-fate determination of mammary luminal progenitors. Mechanistically, RNF8 acted as a negative regulator of Notch signaling by ubiquitylating the active NOTCH1 protein (N1ICD), leading to its degradation. Consistent with abnormal activation of Notch signaling and impaired repair of DSBs in Rnf8-mutant mammary epithelial cells, we observed increased risk of mammary tumorigenesis in mouse models for RNF8 deficiency. Notably, deficiency of RNF8 sensitized breast cancer cells to combination of pharmacological inhibitors of Notch signaling and poly(ADP-ribose) polymerase (PARP), suggesting implications for treatment of breast cancer associated with impaired RNF8 expression or function.

Authors

Li Li, Kiran Kumar Naidu Guturi, Brandon Gautreau, Parasvi S. Patel, Amine Saad, Mayako Morii, Francesca Mateo, Luis Palomero, Haithem Barbour, Antonio Gomez, Deborah Ng, Max Kotlyar, Chiara Pastrello, Hartland W. Jackson, Rama Khokha, Igor Jurisica, El Bachir Affar, Brian Raught, Otto Sanchez, Moulay Alaoui-Jamali, Miguel A. Pujana, Anne Hakem, Razq Hakem

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Figure 1

RNF8 deficiency promotes spontaneous mammary tumorigenesis in mouse models.

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RNF8 deficiency promotes spontaneous mammary tumorigenesis in mouse mode...
(A) Kaplan-Meier mammary tumor-free survival curves of cohorts of WT (n = 23), Rnf8–/– (n = 33), WapCre Trp53fl/fl (n = 28), WapCre Trp53fl/WT (n = 12), Rnf8–/– WapCre Trp53fl/WT (n = 16), and Rnf8–/– WapCre Trp53fl/fl (n = 31) females. Log-rank tests indicate statistically significant differences between Rnf8–/– and WT curves (P = 0.005), Rnf8–/– and Rnf8–/– WapCre Trp53fl/fl curves (P < 0.0001), Rnf8–/– WapCre Trp53fl/fl and WapCre Trp53fl/fl curves (P < 0.0001), and Rnf8–/– WapCre Trp53fl/WT and WapCre Trp53fl/WT curves (P < 0.003). (B) Representative H&E and cytokeratin (CK18 and CK14) immunohistochemical staining of Rnf8–/–, WapCre Trp53fl/fl (Trp53Δ/Δ), and Rnf8–/– WapCre Trp53fl/fl (Rnf8–/– Trp53Δ/Δ) mammary adenocarcinomas. At least 3 tumors per genotype were examined. Scale bars: 50 μm. (C) Representative photographs of Rnf8–/– Trp53Δ/Δ mammary tumors, either mock- or RNF8-reconstituted (as indicated), 40 days after orthotopic injection of these tumor cells into inguinal fat pads of NSG mice (n = 10–12 each). (D) Dot plots showing volume of tumors (n = 10–12 each; mean ± SEM) monitored for 40 days using external caliper. ***P < 0.001, 2-way ANOVA followed by Tukey’s test. (E) Dot plots depict average mass (mean ± SEM) of tumors resected from NSG mice (n = 10–12) following 40 days of outgrowth. ***P < 0.001, 2-sided Student’s t test.