Cyclin E Deregulation Impairs Mitotic Progression through Premature Activation of Cdc25C

Abstract

The cyclin E-cyclin-dependent kinase 2 (CDK2) complex accelerates entry into the S phase of the cell cycle and promotes polyploidy, which may contribute to genomic instability in cancer cells. The effect of low molecular weight isoforms of cyclin E (LMW-E) overexpression on mitotic progression and its link to genomic instability were the focus of this study. Here, we show that full-length cyclin E (EL) and LMW-E overexpression impairs the G 2 -M transition differently by targeting dual-specificity phosphatase Cdc25C activity. We identify Cdc25C as an interaction partner and substrate for cyclin E/CDK2 kinase. Specifically, the cyclin E/CDK2 complex phosphorylates Cdc25C on Ser 214 , leading to its premature activation, which coincides with higher cyclin B/CDK1 and Polo-like kinase 1 (PLK1) activities in an S-phase-enriched population that result in faster mitotic entry. Whereas EL overexpression leads to hyperactivation of Cdc25C, cyclin B/CDK1, and PLK1 in a G 2 -M-enriched population, LMW-E overexpression causes premature inactivation of Cdc25C and PLK1, leading to faster mitotic exit. In addition, LMW-E-overexpressing cells showed a reduction in the mitotic index in the presence of a spindle poison and faster degradation of cyclin B, suggesting an increased rate of mitotic slippage and adaptation to the spindle checkpoint. Lastly, downregulation of Cdc25C inhibits LMW-E-mediated chromosome missegregation, anaphase bridges, and centrosome amplification. These results suggest that the high levels of LMW-E isoforms found in breast cancer may contribute to cellular transformation and genomic instability by impairing mitotic progression involving Cdc25C. Cancer Res; 70(12); 5085-95. ©2010 AACR.

Cdk2 is Required for Breast Cancer Mediated by the Low-Molecular-Weight Isoform of Cyclin E

“…For these experiments we used MCF-7 cells that can inducibly express Flag-tagged LMW cyclin E (T2) upon treatment with doxycycline (7). LMW cyclin E (T2) was induced for 24 hours followed by silencing of Cdk2 expression by transient siRNA transfection (Fig.…”

“…Increase in cell number is detected by augmented MTT metabolization, and decrease in cell number is reflected by decrease in MTT metabolization. MCF-7 cells that can inducibly express Flag-tagged LMW Cyclin E (T2) upon treatment with doxycycline (described in (7)) were plated at a density of 2,500 cells per well in 96-well plates and cultured overnight in MEM supplemented with 10% FBS. Cells were incubated with or without doxycycline (Dox, 1 ug/mL) for 24 h, and cells were then treated with either diluent (DMSO) or CVT-313 (29), or meriolin 5 (30), or roscovitine (31) at 8 different concentrations for 48 hrs.…”

“…One mode of deregulation of cyclin E expression is the generation of low-molecular-weight (LMW) isoforms following cleavage of full length cyclin E by an elastase like protease (5). A consequence for cells with LMW cyclin E expression is increased genomic instability (6) due to premature activation of CDC25C (7) and shortening of the length of mitosis from nuclear envelope breakdown to prometaphase (8). Clinically, the expression of LMW forms of cyclin E correlates strongly with decreased survival in patients with breast cancer (9).…”

Cytoplasmic Cyclin E and Phospho–Cyclin-Dependent Kinase 2 Are Biomarkers of Aggressive Breast Cancer

“…4,26,31 Work from our laboratory has implicated LMW-E in breast cancer oncogenesis. For example, LMW-E i) is biochemically hyperactive because of its increased affinity for cdk2 and resistance to inhibition by the CDK inhibitors p21 and p27 32 ; ii) is resistant to the growth-inhibiting effects of antiestrogens 33 and aromatase inhibitors 34 ; iii) promotes deregulation of cell cycle, 35 centrosome amplification, 13 and genomic instability 33 ; iv) causes premature inactivation of Cdc25C and PLK1, leading to faster mitotic exit 16 ; v) is sufficient to render human mammary epithelial cells tumorigenic and leads to altered acinar morphogenesis 36 ; vi) phosphorylates Hbo1 to mediate a cancer stem cell-like environment 14 ; and vii) is a downstream oncogenic target of protein kinase Ci. 37 Given its unique properties and distinct functions in human cancers, measuring the expression of LMW-E would be instrumental in stratifying patients for targeted therapy against LMW-E/CDK2.…”

Effect of VTCN1 on progression and metastasis of ovarian carcinoma in vitro and vivo

“…Verification of variation of CDK2/CDC25C and JAK/STAT pathways According to previous reports, CDK2/CDK4/CDC25C played an important role in the regulation of cell cycle [17][18][19]. In many tumors, proliferation could be inhibited by the inhibitors of these cell cycle relative proteins [20][21][22].…”