title: Downregulation of KDR expression induces apoptosis in breast cancer cells.
abstract: Angiogenesis plays a crucial role in the growth, invasion and metastasis of breast cancer. Vascular endothelial growth factors (VEGFs) and their receptors (VEGFRs) are the key regulators of tumor angiogenesis. VEGFR-2, known as the kinase insert domain receptor (KDR), is a key receptor involved in malignant angiogenesis. We previously showed that knocking down KDR with short interference RNA (KDR-siRNA) markedly decreased KDR expression and suppressed tumor growth in a xenograft model. However, the mechanisms underlying the anti-cancer effects of KDR-siRNA are not clearly understood. This study aimed to elucidate the molecular mechanisms that induce apoptosis in human breast cancer MCF-7 cells after transfection with KDR-siRNA. We studied the effects of KDR-siRNA on proliferation, apoptosis, antiapoptotic and pro-apoptotic proteins, mitochondrial membrane permeability, cytochrome c release and caspase-3 activity. The results indicated that KDR-siRNA treatment significantly inhibited the proliferation and induced the apoptosis of MCF-7 cells, reduced the levels of the anti-apoptotic proteins, Bcl-2 and Bcl-xl, and increased the level of the pro-apoptotic protein Bax, resulting in a decreased Bcl-2/Bax ratio. KDR-siRNA also enhanced the mitochondrial membrane permeability, induced cytochrome c release from the mitochondria, upregulated apoptotic protease-activating factor-1 (Apaf-1), cleaved caspase-3, and increased caspase-3 activity in MCF-7 cells. Furthermore, KDR-siRNA-induced apoptosis in MCF-7 cells was blocked by the caspase inhibitor Z-VAD-FMK, suggesting a role of caspase activation in the induction of apoptosis. These results indicate that the Bcl-2 family proteins and caspase-related mitochondrial pathways are primarily involved in KDR-siRNAinduced apoptosis in MCF-7 cells and that KDR might be a potential therapeutic target for human breast cancer treatments.
authors.affiliation: Department of Biochemistry and Molecular Biology, Medical College, Qingdao University, 38 Dengzhou Road, Qingdao, China, 266021, zhx7605@126.com.
authors.forename: Xiao
authors.initials: X
authors.lastname: Zhang
authors.forename: Yin-Lin
authors.initials: YL
authors.lastname: Ge
authors.forename: Shu-Ping
authors.initials: SP
authors.lastname: Zhang
authors.forename: Ping
authors.initials: P
authors.lastname: Yan
authors.forename: Run-Hua
authors.initials: RH
authors.lastname: Tian
mesh_terms: D017209:Apoptosis; D051017:Apoptosis Regulatory Proteins / Q000235:genetics / Q000378:metabolism; D001943:Breast Neoplasms; D049109:Cell Proliferation; D015536:Down-Regulation; D005260:Female; D015870:Gene Expression; D006801:Humans; D061986:MCF-7 Cells; D008928:Mitochondria / Q000378:metabolism*; D051336:Mitochondrial Membranes / Q000378:metabolism; D010539:Permeability; D034741:RNA, Small Interfering / Q000235:genetics; D040301:Vascular Endothelial Growth Factor Receptor-2 / Q000235:genetics* / Q000378:metabolism
chemical_list: D051017:Apoptosis Regulatory Proteins; D034741:RNA, Small Interfering; C000588866:KDR protein, human; D040301:Vascular Endothelial Growth Factor Receptor-2