RNF12 is regulated by AKT phosphorylation and promotes TGF-\u03b2 driven breast cancer metastasis

Yongsheng Huang,Wilma E Mesker,Mengjie Shan,Yongmei Song,Lin Wang,Danielle Cohen,Zhangfu Li,Zhi Zheng,Dan Li,Peter Devilee,Sophie C Hagenaars,Long Zhang,Peter Ten Dijke,Rob A E M Tollenaar,Sijia Liu

doi:10.1038/s41419-021-04493-y

Abstract

Transforming growth factor-β (TGF-β) acts as a pro-metastatic factor in advanced breast cancer. RNF12, an E3 ubiquitin ligase, stimulates TGF-β signaling by binding to the inhibitory SMAD7 and inducing its proteasomal degradation. How RNF12 activity is regulated and its exact role in cancer is incompletely understood. Here we report that RNF12 was overexpressed in invasive breast cancers and its high expression correlated with poor prognosis. RNF12 promoted breast cancer cell migration, invasion, and experimental metastasis in zebrafish and murine xenograft models. RNF12 levels were positively associated with the phosphorylated AKT/protein kinase B (PKB) levels, and both displayed significant higher levels in the basal-like subtype compared with the levels in luminal-like subtype of breast cancer cells. Mechanistically, AKT-mediated phosphorylation induced the nuclear localization of RNF12, maintained its stability, and accelerated the degradation of SMAD7 mediated by RNF12. Furthermore, we demonstrated that RNF12 and AKT cooperated functionally in breast cancer cell migration. Notably, RNF12 expression strongly correlated with both phosphorylated AKT and phosphorylated SMAD2 levels in breast cancer tissues. Thus, our results uncovered RNF12 as an important determinant in the crosstalk between the TGF-β and AKT signaling pathways during breast cancer progression.

Highlights

Transforming growth factor-β, (TGF-β), plays a biphasic role in breast cancer progression by acting as a tumor suppressor during the early stages of cancer progression, and a tumor promoter during the late stages [1,2,3]
Aberrant AKT activation and the TGF-β pathway appear to cooperate in promoting breast cancer progression
We found that the E3 ubiquitin ligase, RNF12, plays a pivotal role in the interplay between these two pathways

Summary

INTRODUCTION

Transforming growth factor-β, (TGF-β), plays a biphasic role in breast cancer progression by acting as a tumor suppressor during the early stages of cancer progression, and a tumor promoter during the late stages [1,2,3]. ARKADIA (RNF111) [16] and RNF12 (RLIM) [11] have been identified as E3 ubiquitin ligases acting on SMAD7, which mediate ubiquitination and proteasomal degradation These are negative regulators of SMAD7, and promote TGF-β/SMAD signaling [17]. We tested the activity and inhibits hepatocellular carcinoma cell proliferation role of RNF12 in an experimental breast cancer metastasis model [23, 24]. We show that RNF12 enhances the TGF-β signaling of MCF-7 cells (Supplementary Fig. 3B-C) Together, these results pathway and plays a role in breast cancer cell migration, indicated that RNF12 promotes breast cancer cell migration, invasion, and metastasis. Expression of TGF-β/SMAD-induced target genes that are important for the highly malignant and metastatic phenotype of MDA-

RESULTS

DISCUSSION

Findings

MATERIALS AND METHODS