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Xiyong Liu,
Hang Zhang,
Lily Lai, Xiaochen Wang,
Sofia Loera,
Lijun Xue,
Huiyin He,
Keqiang Zhang,
Shuya Hu,
Yasheng Huang,
Rebecca A Nelson,
Bingsen Zhou,
Lun Zhou,
Peiguo Chu,
Suzhan Zhang,
Shu Zheng,
Yun Yen
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ABSTRACT: The overexpression of ribonucleotide reductase small subunit M2 (RRM2) dramatically enhances the ability of the cancer cell to proliferate and to invade. To further investigate the relevance of RRM2 and colorectal cancers (CRC), we correlated the expression of RRM2 with the clinical outcome of CRCs. A retrospective outcome study was conducted on CRCs collected from City of Hope National Medical Center (COH, 217 cases) and Zhejiang University (ZJU, 220 cases). The immunohistochemistry (IHC) was employed to determine the protein expression level of RRM2, and the quantitative real-time PCR was employed to validate. Multivariate Logistic analysis indicated that the adjusted odds ratios (ORs) of RRM2-high for distant metastases were 2.06(95% CI 1.01-4.30) and 5.89(95% CI 1.51-39.13) in the COH and ZJU sets respectively. The Kaplan-Meier analysis displayed that highly expression of RRM2 negatively impacted the overall (OS) and progress-free survival (PFS) of CRC in both sets significantly. The multivariate COX analysis further demonstrated that hazard ratios (HRs) of RRM2-high for OS were 1.88(95% CI 1.03-3.36) and 2.06(95% CI 1.10-4.00) in the COH and ZJU set respectively. Stratification analysis demonstrated that the HR of RRM2-high dramatically increased to 12.22(95% CI 1.62-258.31) in MMR-deficient subgroup in COH set. Meanwhile, a real-time study demonstrated that down-regulation of RRM2 by siRNA could significantly and specifically reduce the cell growth and adhesion ability in HT-29 and HCT-8 cells. Therefore, RRM2 is an independent prognostic factor and prognoses poor survival of CRCs. It is also a potential predictor for identifying good responders to chemotherapy for CRCs.
Clinical Science 11/2012; · 4.61 Impact Factor
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ABSTRACT: Ribonucleotide reductase (RR) is a rate-limiting enzyme that catalyzes de novo conversion of ribonucleotide 5'-diphosphates to the corresponding 2'-deoxynucleotide, essential for DNA synthesis and replication. The mutations or knockout of RR small subunit, p53R2, results in the depletion of mitochondrial DNA (mtDNA) in human, implying that p53R2 might play a critical role for maintaining mitochondrial homeostasis. In this study, siRNA against p53R2 knockdown approach is utilized to examine the impact of p53R2 depletion on mitochondria and to derive underlying mechanism in KB and PC-3 cancer cells. Our results reveal that the p53R2 expression not only positively correlates with mtDNA content, but also partakes in the proper mitochondria function, such as ATP synthesis, cytochrome c oxidase activity and membrane potential maintenance. Furthermore, overexpression of p53R2 reduces intracellular ROS and protects the mitochondrial membrane potential against oxidative stress. Unexpectedly, knockdown of p53R2 has a modest, if any, effect on mitochondrial and total cellular dNTP pools. Taken together, our study provides functional evidence that mitochondria is one of p53R2-targeted organelles and suggests an unexpected function of p53R2, which is beyond known RR function on dNTP synthesis, in mitochondrial homeostatic control.
Biochemical and Biophysical Research Communications 06/2011; 410(1):102-7. · 2.48 Impact Factor
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Xiyong Liu,
Lily Lai, Xiaochen Wang,
Lijun Xue,
Sofia Leora,
Jun Wu,
Shuya Hu,
Keqiang Zhang,
Mei-Ling Kuo,
Lun Zhou,
Hang Zhang,
Yafan Wang,
Yan Wang,
Bingsen Zhou,
Rebecca A Nelson,
Shu Zheng,
Suzhan Zhang,
Peiguo Chu,
Yun Yen
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ABSTRACT: Ribonucleotide reductase subunit RRM2B (p53R2) has been reported to suppress invasion and metastasis in colorectal cancer (CRC). Here, we report that high levels of RRM2B expression are correlated with markedly better survival in CRC patients. In a fluorescence-labeled orthotopic mouse xenograft model, we confirmed that overexpression of RRM2B in nonmetastatic CRC cells prevented lung and/or liver metastasis, relative to control cells that did metastasize. Clinical outcome studies were conducted on a training set with 103 CRCs and a validation set with 220 CRCs. All participants underwent surgery with periodic follow-up to determine survivability. A newly developed specific RRM2B antibody was employed to carry out immunohistochemistry for determining RRM2B expression levels on tissue arrays. In the training set, the Kaplan-Meier and multivariate Cox analysis revealed that RRM2B is associated with better survival of CRCs, especially in stage IV patients (HR = 0.40; 95% CI = 0.18-0.86, P = 0.016). In the validation set, RRM2B was negatively related to tumor invasion (OR = 0.45, 95% CI = 0.19-0.99, P = 0.040) and lymph node involvement (OR = 0.48, 95% CI = 0.25-0.92, P = 0.026). Furthermore, elevated expression of RRM2B was associated with better prognosis in this set as determined by multivariate analyses (HR = 0.48, 95% CI = 0.26-0.91, P = 0.030). Further investigations revealed that RRM2B was correlated with better survival of CRCs with advanced stage III and IV tumors rather than earlier stage I and II tumors. Taken together, our findings establish that RRM2B suppresses invasiveness of cancer cells and that its expression is associated with a better survival prognosis for CRC patients.
Cancer Research 03/2011; 71(9):3202-13. · 7.86 Impact Factor
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Keqiang Zhang,
Jun Wu,
Xiwei Wu, Xiaochen Wang,
Yan Wang,
Ning Zhou,
Mei-ling Kuo,
Xiyong Liu,
Bingsen Zhou,
Lufen Chang,
David Ann,
Yun Yen
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ABSTRACT: Deregulation of the expression of p53R2, a p53-inducible homologue of the R2 subunit of ribonucleotide reductase, has been found in various human cancer tissues; however, the roles p53R2 plays in cancer progression and malignancy remain controversial. In the present study, we examined changes in gene expression profiles associated with p53R2 in cancer cells, using the analysis of cDNA microarray. Gene set enrichment analysis identified that the gene set regulating cell-cycle progression was significantly enriched in p53R2-silencing human oropharyngeal carcinoma KB cells. Attenuation of p53R2 expression significantly reduced p21 expression and moderately increased cyclin D1 expression in both wild-type p53 cancer cells (KB and MCF-7) and mutant p53 cancer cells (PC3 and MDA-MB-231). Conversely, overexpression of p53R2-GFP resulted in an increase in the expression of p21 and decrease in the expression of cyclin D1, which correlated with reduced cell population in S-phase in vitro and suppressed growth in vivo. Furthermore, the MAP/ERK kinase inhibitor PD98059 partially abolished modulation of p21 and cyclin D1 expression by p53R2. Moreover, under the conditions of nonstress and adriamycin-induced genotoxic stress, attenuation of p53R2 in KB cells significantly increased phosphorylated H2AX, which indicates that attenuation of p53R2 may enhance DNA damage induced by adriamycin. Overall, our study shows that p53R2 may suppress cancer cell proliferation partially by upregulation of p21 and downregulation of cyclin D1; p53R2 plays critical roles not only in DNA damage repair but also in proliferation of cancer cells.
Molecular Cancer Therapeutics 02/2011; 10(2):269-78. · 5.23 Impact Factor
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Xiaochen Wang,
Xiyong Liu,
Angela Ying-Jian Li,
Lirong Chen,
Lily Lai,
Her Helen Lin,
Shuya Hu,
Lifang Yao,
Jiaping Peng,
Sofia Loera,
Lijun Xue,
Bingsen Zhou,
Lun Zhou,
Shu Zheng,
Peiguo Chu,
Suzhan Zhang,
David Kong Ann,
Yun Yen
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ABSTRACT: This study aims to address the hypothesis that the high-mobility group A2 (HMGA2), an oncofetal protein, relates to survivability and serves as a prognostic biomarker for colorectal cancer (CRC).
This is a retroprospective multiple center study. The HMGA2 expression level was determined by performing immunohistochemistry on surgical tissue samples of 89 CRCs from a training set and 191 CRCs from a validation set. The Kaplan-Meier analysis and COX proportional hazard model were employed to analyze the survivability.
Multivariate logistic analysis indicated that the expression of HMGA2 significantly correlates with distant metastasis in training set (odds ratio, OR = 3.53, 95% CI: 1.37-9.70) and validation set (OR = 6.38, 95% CI: 1.47-43.95). Survival analysis revealed that the overexpression of HMGA2 is significantly associated with poor survival of CRC patients (P < 0.05). The adjusted HRs for overall survival were 2.38 (95% CI: 1.30-4.34) and 2.14 (95% CI: 1.21-3.79) in training and validation sets, respectively. Further investigation revealed that HMGA2 delays the clearance of γ-H2AX in HCT-116 and SW480 cells post γ-irradiation, which supports our finding that CRC patients with HMAG2-positive staining in primary tumors had augmented the efficacy of adjuvant radiotherapy (HR = 0.18, 95% CI: 0.04-0.63).
Overexpression of HMGA2 is associated with metastasis and unequivocally occurred in parallel with reduced survival rates of patients with CRC. Therefore, HMGA2 may potentially serve as a biomarker for predicting aggressive CRC with poor survivability and as an indicator for better response of radiotherapy.
Clinical Cancer Research 01/2011; 17(8):2570-80. · 7.74 Impact Factor
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ABSTRACT: In addition to its essential role in ribonucleotide reduction, ribonucleotide reductase (RNR) small subunit, RRM2, has been known to play a critical role in determining tumor malignancy. Overexpression of RRM2 significantly enhances the invasive and metastatic potential of tumor. Angiogenesis is critical to tumor malignancy; it plays an essential role in tumor growth and metastasis. It is important to investigate whether the angiogenic potential of tumor is affected by RRM2.
We examined the expression of antiangiogenic thrombospondin-1 (TSP-1) and proangiogenic vascular endothelial growth factor (VEGF) in two RRM2-overexpressing KB cells: KB-M2-D and KB-HURs. We found that TSP-1 was significantly decreased in both KB-M2-D and KB-HURs cells compared to the parental KB and mock transfected KB-V. Simultaneously, RRM2-overexpressing KB cells showed increased production of VEGF mRNA and protein. In contrast, attenuating RRM2 expression via siRNA resulted in a significant increased TSP-1 expression in both KB and LNCaP cells; while the expression of VEGF by the two cells was significantly decreased under both normoxia and hypoxia. In comparison with KB-V, overexpression of RRM2 had no significant effect on proliferation in vitro, but it dramatically accelerated in vivo subcutaneous growth of KB-M2-D. KB-M2-D possessed more angiogenic potential than KB-V, as shown in vitro by its increased chemotaxis for endothelial cells and in vivo by the generation of more vascularized tumor xenografts.
These findings suggest a positive role of RRM2 in tumor angiogenesis and growth through regulation of the expression of TSP-1 and VEGF.
Molecular Cancer 03/2009; 8:11. · 3.99 Impact Factor
