FKBP10-inhibited β-catenin ubiquitination in the malignant transformation of breast epithelial cells.

Abstract

e12580 Background: Current model of breast cancer (BCa) progression suggests a linear and three-stage process from normal epithelial tissue to ductal carcinoma in situ (DCIS), and then invasive ductal carcinoma (IDC). Since the detailed mechanisms for BCa oncogenesis remain largely unclear and there is still a lack of root-cause level interventions, exploring the underlying molecular alterations during three-stage process of BCa carcinogenesis is urgently needed. Methods: Three-stage specimens from the very same patients were collected. High-throughput sequencing was applied to obtain the differentially expressed genes among normal, DCIS, and IDC samples. Expression level and prognostic value of the selected gene were evaluated by PCR, western blot, tissue chip, and bioinformatics analysis. MCF10DCIS and MCF10Ca cell lines were respectively used to establish DCIS and IDC tumor models in breast epithelial cell-specific gene knockout mice. Patient-matched DCIS and IDC organoids were also constructed. Signaling pathways associated with malignant transformation of breast epithelial cells were detected by using high-throughput sequencing in mouse models and organoids. Protein binding was evaluated by protein mass spectrometry and co-immunoprecipitation. Results: By using high-throughput sequencing, we found that FKBP10 levels were gradually increased in three-stage specimens from the very same patients and were associated with poor prognosis. By establishing DCIS and IDC models in FKBP10flox/floxCre+/- and FKBP10flox/floxCre-/- control mice, we confirmed that FKBP10 deficiency could suppress BCa formation. Besides, FKBP10 knockdown could reduce oncogenic potentials in patient-matched DCIS and IDC organoids. Wnt/β-catenin signaling pathway was related to malignant transformation of breast epithelial cells, when MCF10DCIS+FKBP10flox/floxCre+/- model, MCF10Ca+FKBP10flox/floxCre+/- model, FKBP10-knockdown DCIS and IDC organoids, and their corresponding controls were comprehensively compared. Moreover, FKBP10 was found to inhibit β-catenin ubiquitination with the help of deubiquitinase Trim13, thus activating Wnt/β-catenin signaling pathway and accelerating malignant transformation of breast epithelial cells. Increased level of β-catenin was able to promote FKBP10 expression in a feedback loop. We also confirmed that exosome-loaded FKBP10-targeting peptide could suppress tumor growth both in vitro and in vivo. Conclusions: FKBP10-inhibited β-catenin ubiquitination was responsible in the malignant transformation from normal tissue to DCIS, and then IDC. Our study would uncover novel regulatory mechanisms of FKBP10 in three-stage process of BCa carcinogenesis and provide a new therapeutic approach for clinical treatment.