title: PIK3R1 targeting by miR-21 suppresses tumor cell migration and invasion by reducing PI3K/AKT signaling and reversing EMT, and predicts clinical outcome of breast cancer.
abstract: We have previously shown that dysregulation of miR-21 functioned as an oncomiR in breast cancer. The aim of the present study was to elucidate the mechanisms by which miR-21 regulate breast tumor migration and invasion. We applied pathway analysis on genome microarray data and target-predicting algorithms for miR-21 target screening, and used luciferase reporting assay to confirm the direct target. Thereafter, we investigated the function of the target gene phosphoinositide-3-kinase, regulatory subunit 1 (α) (PIK3R1), and detected PIK3R1 coding protein (p85α) by immunohistochemistry and miR-21 by RT-qPCR on 320 archival paraffin-embedded tissues of breast cancer to evaluate the correlation of their expression with prognosis. First, we found that PIK3R1 suppressed growth, invasiveness, and metastatic properties of breast cancer cells. Next, we identified the PIK3R1 as a direct target of miR-21 and showed that it was negatively regulated by miR-21. Furthermore, we demonstrated that p85α overexpression phenocopied the suppression effects of antimiR-21 on breast cancer cell growth, migration and invasion, indicating its tumor suppressor role in breast cancer. On the contrary, PIK3R1 knockdown abrogated antimiR‑21-induced effect on breast cancer cells. Notably, antimiR-21 induction increased p85α, accompanied by decreased p-AKT level. Besides, antimiR-21/PIK3R1-induced suppression of invasiveness in breast cancer cells was mediated by reversing epithelial-mesenchymal transition (EMT). p85α downregulation was found in 25 (7.8%) of the 320 breast cancer patients, and was associated with inferior 5-year disease-free survival (DFS) and overall survival (OS). Taken together, we provide novel evidence that miR-21 knockdown suppresses cell growth, migration and invasion partly by inhibiting PI3K/AKT activation via direct targeting PIK3R1 and reversing EMT in breast cancer. p85α downregulation defined a specific subgroup of breast cancer with shorter 5-year DFS and OS, which may require more aggressive treatment.
authors.affiliation: Department of Pathology, Guangdong General Hospital, Guangdong Academy of Medical Science, Guangzhou, Guangdong, P.R. China.
authors.forename: Li-Xu
authors.initials: LX
authors.lastname: Yan
authors.affiliation: Department of Pathology, Guangdong General Hospital, Guangdong Academy of Medical Science, Guangzhou, Guangdong, P.R. China.
authors.forename: Yan-Hui
authors.initials: YH
authors.lastname: Liu
authors.affiliation: Guangdong Provincial Hospital of Chinese Medicine, Guangzhou, Guangdong, P.R. China.
authors.forename: Jian-Wen
authors.initials: JW
authors.lastname: Xiang
authors.affiliation: The First Affiliated Hospital of Guangzhou Medical University, Guangzhou, Guangdong, P.R. China.
authors.forename: Qi-Nian
authors.initials: QN
authors.lastname: Wu
authors.affiliation: Sun Yat-sen Memorial Hospital, SunYat-sen University, Guangzhou, Guangdong, P.R. China.
authors.forename: Lei-Bo
authors.initials: LB
authors.lastname: Xu
authors.affiliation: Department of Pathology, Guangdong General Hospital, Guangdong Academy of Medical Science, Guangzhou, Guangdong, P.R. China.
authors.forename: Xin-Lan
authors.initials: XL
authors.lastname: Luo
authors.affiliation: Department of Pathology, Guangdong General Hospital, Guangdong Academy of Medical Science, Guangzhou, Guangdong, P.R. China.
authors.forename: Xiao-Lan
authors.initials: XL
authors.lastname: Zhu
authors.affiliation: Department of Pathology, Guangdong General Hospital, Guangdong Academy of Medical Science, Guangzhou, Guangdong, P.R. China.
authors.forename: Chao
authors.initials: C
authors.lastname: Liu
authors.affiliation: Department of Pathology, Guangdong General Hospital, Guangdong Academy of Medical Science, Guangzhou, Guangdong, P.R. China.
authors.forename: Fang-Ping
authors.initials: FP
authors.lastname: Xu
authors.affiliation: Department of Pathology, Guangdong General Hospital, Guangdong Academy of Medical Science, Guangzhou, Guangdong, P.R. China.
authors.forename: Dong-Lan
authors.initials: DL
authors.lastname: Luo
authors.affiliation: Department of Pathology, Guangdong General Hospital, Guangdong Academy of Medical Science, Guangzhou, Guangdong, P.R. China.
authors.forename: Ping
authors.initials: P
authors.lastname: Mei
authors.affiliation: Department of Pathology, Guangdong General Hospital, Guangdong Academy of Medical Science, Guangzhou, Guangdong, P.R. China.
authors.forename: Jie
authors.initials: J
authors.lastname: Xu
authors.affiliation: Department of Pathology, Guangdong General Hospital, Guangdong Academy of Medical Science, Guangzhou, Guangdong, P.R. China.
authors.forename: Ke-Ping
authors.initials: KP
authors.lastname: Zhang
authors.affiliation: Department of Pathology, Guangdong General Hospital, Guangdong Academy of Medical Science, Guangzhou, Guangdong, P.R. China.
authors.forename: Jie
authors.initials: J
authors.lastname: Chen
mesh_terms: D001943:Breast Neoplasms / Q000235:genetics*; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000235:genetics*; D049109:Cell Proliferation / Q000235:genetics; D058543:Class Ia Phosphatidylinositol 3-Kinase; D018572:Disease-Free Survival; D015536:Down-Regulation / Q000235:genetics; D058750:Epithelial-Mesenchymal Transition / Q000235:genetics*; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000235:genetics; D006801:Humans; D061986:MCF-7 Cells; D035683:MicroRNAs / Q000235:genetics*; D009361:Neoplasm Invasiveness / Q000235:genetics*; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics*; D011379:Prognosis; D051057:Proto-Oncogene Proteins c-akt / Q000235:genetics*; D015398:Signal Transduction / Q000235:genetics
chemical_list: D058543:Class Ia Phosphatidylinositol 3-Kinase; D035683:MicroRNAs; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt; C524940:MIRN21 microRNA, human; C588001:PIK3R1 protein, human