Evaluation of claspin as a proliferation marker in human cancer and normal tissues

National Center for Scientific Research Demokritos, Athínai, Attica, Greece
The Journal of Pathology (Impact Factor: 7.43). 02/2007; 211(3):331-9. DOI: 10.1002/path.2095
Source: PubMed


Claspin is a nuclear protein involved in DNA replication and the DNA damage response. Its structural and functional properties suggest that it may represent a potentially useful proliferation marker. To this end, a monoclonal antibody was generated and the expression of claspin was investigated in normal fibroblasts and various cancer cell lines, as well as in tumour and normal tissues from patients with primary epithelial carcinomas. Immunoblotting analysis confirmed the specificity of the antibody, while immunohistochemistry demonstrated its applicability in archival material. In normal cells and tissues, claspin expression was weak, whereas increased levels were observed in cancer cell lines and tumour specimens. Claspin staining correlated strongly with Ki67 staining in both normal (p < 0.001) and tumour tissues (p < 0.001). However, the labelling index (LI) of claspin was consistently lower than that of Ki67, suggesting that claspin expression may be limited to a narrower part of the cell cycle. Co-localization assays with cyclin A and cell synchronization experiments indicated that claspin expression coincides with the S phase. Interestingly, the relative increase of the claspin LI in tumour samples compared with normal tissues was significantly higher (14-fold) than that of the Ki67 LI (five-fold), suggesting that claspin may be a more sensitive marker of aberrant proliferation.

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Available from: Petros Tsantoulis, Aug 03, 2014
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    • "These alterations may lead to genomic instability triggering cancer development [5,6]. However, the expression of claspin significantly increases in several human solid tumors such as in colon, lung, bladder and breast cancer [7]. Despite these findings, to date no data are available concerning claspin expression in human cervical carcinogenesis which represents a paradigmatic model of cancer development. "
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    ABSTRACT: Claspin is a nuclear protein involved in DNA replication and damage response and is a key mediator for the S-phase checkpoint. Claspin expression is significantly high in several human solid tumors. Furthermore, high levels of claspin have been found in cervical cancer cell lines. Nevertheless, no data are available regarding claspin expression in cervical tissues. In order to investigate whether claspin immunoreactivity is related to the lesion severity and High-Risk (HR) HPV infection, we analyzed claspin expression by immunohistochemistry in a series of cervical biopsies which represent the steps occurring during cervical carcinogenesis (normal tissues, Cervical Intraepithelial Neoplasias 1, 2 and 3, Squamous Cell Carcinomas). All patients also had a cervico-vaginal sample for HPV testing, collected immediately before the colposcopy-guided biopsy. The HR-HPV DNA detection was performed by the HR-HPV Hybrid Capture 2 test. HPV genotyping was performed using the Linear Array HPV Genotyping Test. Our results evidenced a constant and significant increase of the rate of claspin positivity from the normal tissues to carcinomas (pχ2trend < 0.0001). In fact, the normal tissues displayed either no or faint claspin immunoreactivity, whereas a moderate/high positivity was observed in 16% of the CIN1, 76% of the CIN2, 87.5% of the CIN3 and 93.3% of the cancers. Moreover, we found a statistically significant correlation between claspin expression and HR-HPV infection (pχ2 < 0.0001), irrespective of the genotype. Finally, we demonstrated the feasibility of claspin immunostaining in cervical cytology. Our findings indicate that in vivo claspin expression is significantly related to HR-HPV infection and lesion grade both in histological and cytological samples. Therefore, the analysis of claspin expression could be clinically relevant in the diagnosis of HPV-related cervical lesions, in particular when applied to cervico-vaginal cytology. Moreover, giving information on the proliferation rate of each lesion, claspin immunostaining may contribute to the evaluation of progression risk, thus being helpful in patient management. Nevertheless, only large prospective studies may clarify the true clinical usefulness of claspin expression in distinguishing lesions with different progression potential.
    Full-text · Article · Jun 2012 · Journal of Translational Medicine
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    • "Claspin plays a poorly understood, positive role in DNA replication, which appears distinct from its role in checkpoint signaling. In fact, not only does expression of Claspin represent a reliable marker of cell proliferation in both human cancer and normal tissues (Tsimaratou et al., 2007), but Claspin overexpression has also been shown to increase cell proliferation (Lin et al., 2004). Our finding suggests that Claspin represents another substrate that APC/C Cdh1 keeps at low levels during G1 to avoid premature entry into S. "
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    ABSTRACT: In response to DNA damage in G2, mammalian cells must avoid entry into mitosis and instead initiate DNA repair. Here, we show that, in response to genotoxic stress in G2, the phosphatase Cdc14B translocates from the nucleolus to the nucleoplasm and induces the activation of the ubiquitin ligase APC/C(Cdh1), with the consequent degradation of Plk1, a prominent mitotic kinase. This process induces the stabilization of Claspin, an activator of the DNA-damage checkpoint, and Wee1, an inhibitor of cell-cycle progression, and allows an efficient G2 checkpoint. As a by-product of APC/C(Cdh1) reactivation in DNA-damaged G2 cells, Claspin, which we show to be an APC/C(Cdh1) substrate in G1, is targeted for degradation. However, this process is counteracted by the deubiquitylating enzyme Usp28 to permit Claspin-mediated activation of Chk1 in response to DNA damage. These findings define a novel pathway that is crucial for the G2 DNA-damage-response checkpoint.
    Full-text · Article · Aug 2008 · Cell
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    ABSTRACT: We previously showed that checkpoint kinase 1 (Chk1) and Claspin, two DNA-damage checkpoint proteins, were down-regulated by 1,25-dihydroxyvitamin D(3), a known inhibitor of cell proliferation. In the present study, we aimed to investigate the transcriptional regulation of Chk1 and Claspin and to study their expression levels in human breast cancer tissue. Transient transfection experiments in MCF-7 breast cancer cells showed that promoter activities of Chk1 and Claspin were regulated by the E2F family of transcription factors. Subsequently, transcript levels of Chk1, Claspin, and E2F1 were determined by quantitative reverse transcriptase-PCR analysis in 103 primary invasive breast carcinomas and were compared with several clinicopathologic variables in breast cancer. A strong correlation was found between Chk1 and Claspin transcript levels. Transcript levels of Chk1, Claspin, and E2F1 were highest in histologic grade 3 tumors and in tumors in which the expression of estrogen receptor (ER) and progesterone receptor (PR) was lost. Moreover, Chk1 expression was significantly elevated in grade 3 breast carcinomas showing a triple-negative ER-/PR-/HER-2- phenotype compared with other grade 3 tumors. Further research is warranted to validate the use of Chk1 inhibitors in triple-negative breast carcinomas for which treatment strategies are limited at present.
    Full-text · Article · Aug 2007 · Cancer Research
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