Abstract 26: MiR-205 targets integrin-α5 and inhibits triple-negative breast cancer metastasis
Authors: Xiao Yajuan , Wang Zhishan , Li Yunfei , Wu Jianjun , Tao Hua , Li Aimin , Luo Rongcheng , Yang Chengfeng 
Published: August 2018

Abstract
Triple negative breast cancer (TNBC) is the most aggressive subtype of breast cancer, lacking effective target therapy compared to ER/PR+ or HER2+ breast cancer. Micro-RNAs are small non-coding RNAs playing a significant role in cancer stemness maintenance, tumor growth, and metastasis. Studies showed that miR-205 plays an important role in regulating EMT, cell proliferation and migration, tumor growth and metastasis, and drug-resistance of cancers, such as lung, renal, prostate and breast cancer. However, whether miR-205 plays a role in TNBC tumor growth and metastasis remains to be determined. We found that higher miR-205 expression level was strongly correlated with breast cancer patient better overall survival. The expression level of miR-205 was prominently downregulated in basal mesenchymal-like highly migratory and invasive TNBC cell lines, compared to basal epithelial-like TNBC and other breast cancer cell lines. Bioinformatics analysis identified that integrin- α5 (ITGA5) is a potential target of miR-205. Western blot analysis revealed that the expression level of integrin-α5 is significantly higher in basal mesenchymal-like TNBC cell lines than other breast cancer cell lines. Two miR-205 overexpression cell lines were established by transfecting TNBC LM2 and SUM-159 cell lines with miR-205 precursor expressing lentivirus. The expression level of ITGA5 was downregulated in miR-205 overexpressing LM2 and SUM-159 cells. Wound healing assay and transwell cell migration assay revealed that miR-205 overexpression reduced migration of TNBC cells, although no difference of cell proliferation was observed between miR-205 overexpression and vectors control cells as determined by the MTT assay. The cancer stem cell-like property of TNBC cells was inhibited by miR-205 overexpression as demonstrated by the mammary sphere formation assay. In in vivo experiments, mammary tumor growth and lung metastasis were inhibited by miR-205 overexpression using mammary fat pad xenograft tumor models. When ITGA5 was re-expressed in miR-205 overexpression cell lines, the migratory ability of TNBCs was rescued. The metastatic capability of TNBC mammary xenograft tumors was also restored. Further mechanistic studies proved that miR-205 can reduce the formation of lamellipodium, a hallmark of Rac1/cdc42 activation and cell migration, by targeting ITGA5. Rac1/cdc42 pull-down assay showed that miR-205 inhibited Rac1/cdc42 activation, while ITGA5 overexpression restored the activation of Rac1/cdc42. For uncovering the upstream regulator of Rac1/cdc42, several Rac inhibitors were scanned and it was found that inhibition of vav2 by EHop-016 reduced the downstream effects from ITGA5 signaling. CoIP revealed that Src/Vav2 pathway was activated by ITGA5. In conclusion, miR-205 suppresses TNBC cell migration and tumor metastasis by targeting ITGA5 and inhibits Src/vav-2/Rac1/cdc42 pathway.
Citation Format: Yajuan Xiao, Zhishan Wang, Yunfei Li, Jianjun Wu, Hua Tao, Aimin Li, Rongcheng Luo, Chengfeng Yang. MiR-205 targets integrin-α5 and inhibits triple-negative breast cancer metastasis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 26.