Downregulation of KDR expression induces apoptosis in breast cancer cells.

Xiao Zhang,Run-Hua Tian,Shu-Ping Zhang,Yin-Lin Ge,Ping Yan

doi:10.2478/s11658-014-0210-8

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.

Highlights

Breast cancer is one of the most common cancers in women, accounting for 23% of the total cancer cases
kinase insert domain receptor (KDR)-Short interfering RNA (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
We previously showed that KDR-siRNA suppressed tumor growth in a xenograft model [13], suggesting that KDR-siRNA might be an effective approach for the treatment of breast cancer

Summary

Introduction

Breast cancer is one of the most common cancers in women, accounting for 23% of the total cancer cases. Vascular endothelial growth factors (VEGFs) and their receptors (VEGFRs) are emerging as the key regulators of tumor angiogenesis. VEGFR-2, known as kinase insert domain receptor (KDR), is a key receptor involved in malignant angiogenesis. Recent studies showed that the monoclonal antibody ramucirumab, which targets KDR, appears to be effective at treating breast cancer. Short interfering RNA (siRNA) is a natural phenomenon of the inhibition of gene expression It provides us with an effective and simple method to downregulate target genes [12]. We previously showed that KDR-siRNA suppressed tumor growth in a xenograft model [13], suggesting that KDR-siRNA might be an effective approach for the treatment of breast cancer. Inducing tumor cell apoptosis has become an effective strategy for cancer treatment [14, 15]. Most previous studies about KDR have centered on its role in cell proliferation

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