SiRNA-Based Targeting of Cyclin E Overexpression Inhibits Breast Cancer Cell Growth and Suppresses Tumor Development in Breast Cancer Mouse Model

Yulong Liang,Shiaw-Yih Lin,Francis C Brunicardi,Hong Gao,John A Goss,Kaiyi Li,Roger Chammas

doi:10.1371/journal.pone.0012860

SiRNA-Based Targeting of Cyclin E Overexpression Inhibits Breast Cancer Cell Growth and Suppresses Tumor Development in Breast Cancer Mouse Model

Yulong Liang, Shiaw-Yih Lin + Show 5 more

Open Access

https://doi.org/10.1371/journal.pone.0012860

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Abstract

Cyclin E is aberrantly expressed in many types of cancer including breast cancer. High levels of the full length as well as the low molecular weight isoforms of cyclin E are associated with poor prognosis of breast cancer patients. Notably, cyclin E overexpression is also correlated with triple-negative basal-like breast cancers, which lack specific therapeutic targets. In this study, we used siRNA to target cyclin E overexpression and assessed its ability to suppress breast cancer growth in nude mice. Our results revealed that cyclin E siRNA could effectively inhibit overexpression of both full length and low molecular weight isoforms of cyclin E. We found that depletion of cyclin E promoted apoptosis of cyclin E-overexpressing cells and blocked their proliferation and transformation phenotypes. Significantly, we further demonstrated that administration of cyclin E siRNA could inhibit breast tumor growth in nude mice. In addition, we found that cyclin E siRNA synergistically enhanced the cell killing effects of doxorubicin in cell culture and this combination greatly suppressed the tumor growth in mice. In conclusion, our results indicate that cyclin E, which is overexpressed in 30% of breast cancer, may serve as a novel and effective therapeutic target. More importantly, our study clearly demonstrates a very promising therapeutic potential of cyclin E siRNA for treating the cyclin E-overexpressing breast cancers, including the very malignant triple-negative breast cancers.

Highlights

Cyclin E, encoded by cyclin E/CCNE1, is an important cell cycle regulator, which promotes G1/S transition by activation of Cdk2 kinase activity [1,2]
CycE overexpression is suppressed in breast cancer cells by siRNA targeting To address if cyclin E (cycE) can serve as a novel therapeutic target for breast cancer, we first used siRNA oligos to deplete cycE expression in breast cancer cells
High levels of the wild-type and low molecular weight (LMW) isoforms of cycE are associated with poor prognosis of breast cancer patients [14]

Summary

Introduction

Cyclin E (cycE), encoded by cyclin E/CCNE1, is an important cell cycle regulator, which promotes G1/S transition by activation of Cdk kinase activity [1,2]. The accumulated cycE at G1/S boundary simultaneously forms complex with Cdk and subsequently promotes initiation of DNA replication and centrosome duplication. CycE is overexpressed in ,30% patients [11], including overexpression of both the full length (50 kDa) and several low molecular weight (LMW) isoforms (ranging in size from 33 to 45 kD) of cycE protein [12,13]. Total levels of cycE (both full length and LMW isoforms) in tumor tissues are inversely correlated with survival in patients with breast cancer [14]. The patients whose cancers show high levels of cycE at stage I die within five years of diagnosis, while in contrast, cycE-low expressing patients have a much longer survival, indicating that overexpressed cycE may be an important cause for breast cancer mortality, and cycE may serve as an important therapeutic target for the development of anticancer drugs

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