Bailong Li1, Ying Lu2, Honghai Wang3, Xiaocui Han2, Jun Mao2, Jiazhi Li2, Lihui Yu2, Bo Wang2, Shujun Fan2, Xiaotang Yu2, Bo Song4. 1. Department of Clinical Medicine, Grade 2013, Dalian Medical University, No. 9 West Section, Lvshun Road, Dalian 116044, China. 2. Department of Pathology and Forensics, Dalian Medical University, No. 9 West Section, Lvshun Road, Dalian 116044, China. 3. Academic Affairs Department, Dalian Medical University, No. 9 West Section, Lvshun Road, Dalian 116044, China. 4. Department of Pathology and Forensics, Dalian Medical University, No. 9 West Section, Lvshun Road, Dalian 116044, China. Electronic address: yr0806@hotmail.com.
Abstract
BACKGROUND: The miR-221/222 cluster has been discovered to function as oncogene in human malignancies including breast cancer. However, the role of miR-221/222 in the self-renewal of breast cancer stem cells (BCSCs) is not fully understood. In this study, we examined the impact and mechanism of miR-221/222 on the breast cancer cell viability, migration and invasion, and propagation of BCSCs. METHODS: Human breast cancer cell line MCF-7 was transfected with miR-221/222 mimics or inhibitors to overexpress or knock down miR-221/222 respectively using Lipofactamine 2000. The biological effects of miR-221 and miR-222 were then assessed by cell proliferation assay, colony formation assay and transwell chamber assays. CD44/CD24 staining and mammosphere formation assay were performed to evaluate the ability of BCSCs self-renewal. Potential target gene phosphatase and tensin homolog (PTEN) and its downstream effector, phosphorylated Akt (p-Akt) were identified by Western blot and qRT-PCR methods. RESULTS: PTEN, a tumor suppressor gene, was confirmed as a target of miR-221/222 in breast cancer cell line MCF-7. Downregulation of PTEN by miR-221/222 increased the phosphorylation of Akt. Enforced expression of miR-221/222 promoted breast cancer cell proliferation, migration and invasion via targeting PTEN/Akt pathway. Importantly, ectopic expression of miR-221/222 enriched the proportion of CD44(+)/CD24(-) BCSCs and improved the mammosphere formation capacity through targeting PTEN/Akt pathway. Blocking the endogenous miR-221/222 restored PTEN expression and subsequently decreased Akt phosphorylation, and thereby reversed this phenotype. CONCLUSIONS: Our results suggested that miR-221/222 enhance breast cancer growth, migration and invasion, meanwhile propagate the self-renewal of BCSCs. This is achieved possibly through targeting PTEN/Akt pathway. miR-221/222 might be a novel therapeutic candidate for human breast cancer.
BACKGROUND: The miR-221/222 cluster has been discovered to function as oncogene in humanmalignancies including breast cancer. However, the role of miR-221/222 in the self-renewal of breast cancer stem cells (BCSCs) is not fully understood. In this study, we examined the impact and mechanism of miR-221/222 on the breast cancer cell viability, migration and invasion, and propagation of BCSCs. METHODS:Humanbreast cancer cell line MCF-7 was transfected with miR-221/222 mimics or inhibitors to overexpress or knock down miR-221/222 respectively using Lipofactamine 2000. The biological effects of miR-221 and miR-222 were then assessed by cell proliferation assay, colony formation assay and transwell chamber assays. CD44/CD24 staining and mammosphere formation assay were performed to evaluate the ability of BCSCs self-renewal. Potential target gene phosphatase and tensin homolog (PTEN) and its downstream effector, phosphorylated Akt (p-Akt) were identified by Western blot and qRT-PCR methods. RESULTS:PTEN, a tumor suppressor gene, was confirmed as a target of miR-221/222 in breast cancer cell line MCF-7. Downregulation of PTEN by miR-221/222 increased the phosphorylation of Akt. Enforced expression of miR-221/222 promoted breast cancer cell proliferation, migration and invasion via targeting PTEN/Akt pathway. Importantly, ectopic expression of miR-221/222 enriched the proportion of CD44(+)/CD24(-) BCSCs and improved the mammosphere formation capacity through targeting PTEN/Akt pathway. Blocking the endogenous miR-221/222 restored PTEN expression and subsequently decreased Akt phosphorylation, and thereby reversed this phenotype. CONCLUSIONS: Our results suggested that miR-221/222 enhance breast cancer growth, migration and invasion, meanwhile propagate the self-renewal of BCSCs. This is achieved possibly through targeting PTEN/Akt pathway. miR-221/222 might be a novel therapeutic candidate for humanbreast cancer.
Authors: Luni Emdad; Praveen Bhoopathi; Sarmistha Talukdar; Anjan K Pradhan; Devanand Sarkar; Xiang-Yang Wang; Swadesh K Das; Paul B Fisher Journal: Semin Cancer Biol Date: 2019-07-26 Impact factor: 15.707