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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.

Abbreviations

Apaf-1:

apoptotic protease-activating factor-1

BSA:

bovine serum albumin

DMEM:

Dulbecco’s modified Eagle’s medium

KDR:

kinase domain receptor

MTT:

3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazo-liumbromide

SDS:

sodium dodecyl sulphate

siRNA:

short interfering RNA

VEGF:

vascular endothelial growth factor

VEGFR:

vascular endothelial growth factor receptor

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Correspondence to Xiao Zhang or Yin-Lin Ge.

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Zhang, X., Ge, YL., Zhang, SP. et al. Downregulation of KDR expression induces apoptosis in breast cancer cells. Cell Mol Biol Lett 19, 527–541 (2014). https://doi.org/10.2478/s11658-014-0210-8

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  • DOI: https://doi.org/10.2478/s11658-014-0210-8

Keywords

  • Apoptosis
  • Breast cancer
  • MCF-7 cells
  • Cytochrome c
  • caspase-3
  • Mitochondrial pathway
  • KDR
  • VEGF
  • Short interfering RNA
  • siRNA