Immunohistochemistry analysis of checkpoint kinase 2 in oral squamous cell carcinoma

Background: Oral squamous cell carcinoma (OSCC) is the most frequently occurring malignant tumor of the head and neck region. Chk2 (Checkpoint kinase 2) is considered a tumor suppressor gene that acts on the cellular response to DNA damage. However, the role of Chk2 in OSCC prognosis is not yet fully understood. The objective of this study was to evaluate Chk2 immunoexpression in OSCC and to elucidate the association between its expression and clinicopathological parameters of prognostic importance, including overall survival, disease-free survival, and metastasis-free survival. Methods: Chk2 expression was analyzed in 101 samples from patients with OSCC using immunohistochemistry. We stratified the patients into high expression (> 66% of cells positive for Chk2) and low expression (< 66%) groups. Results: Chk2 showed high expression in 57.43% of OSCC. In our study, the expression of Chk2 did not correlate with any of the prognostic parameters evaluated. There was no difference between overall survival, metastasis-free survival, and disease-free survival according to Chk2 expression. Conclusion: Despite the great importance of Chk2 in the development of different types of cancer, our findings do not favor Chk2 as a prognostic marker in oral squamous cell carcinoma.

DNA-PKcs functions in cellular hyper-radiosensitivity / 中华放射医学与防护杂志

Objective@#To explore the functions of DNA-PKcs in cellular low dose hyper-radiosensitivity.@*Methods@#Colony-formation assay was used to detect the survival fractions of M059K and M059J cell lines treated by X-ray irradiation. Micronucleus assay and γ-H2AX foci assay were used to measure the radiation-induced DNA damage. Western blot was used to detect the relative expression levels of phospho-Chk1, total Chk1, phospho-Chk2 and total Chk2 of M059K and M059J cells.@*Results@#The hyper-radiosensitivity was observed in M059K cells irradiated with X-ray of doses lower than 1 Gy. DNA damage levels did not show HRS/IRR in the cell lines we used. pChk1/Chk1 in M059K cells was significantly increased during 20 min to 60 min after 0.2 Gy X-ray irradiation (t=14.157, 13.661, 14.177, 11.317, 14.512, P<0.05); pChk2/Chk2 in M059K cells was markedly increased during 20 min to 50 min after 0.2 Gy X-ray irradiation (t=13.182, 13.868, 14.155, 14.477, P<0.05).@*Conclusions@#M059K cells show the phenomenon of low dose hyper-radiosensitivity, which may be related to activation of proteins in G2/M phase checkpoints regulated by DNA-PKcs.

Impacts of Chk1 and Chk2 gene expressions on sperm concentration and motility / 中华男科学杂志

Objective@#To study the correlation of the gene expressions of Chk1 and Chk2 with sperm concentration and motility.@*METHODS@#According to sperm concentration and motility (percentage of progressively motile sperm), we divided 80 semen samples into four groups of equal number: normal control, oligozoospermia (OS), asthenospermia (AS), and oligoasthenozoospermia (OAS). We detected the sperm DNA fragmentation index (DFI) and viability and determined the expressions of Chk1 and Chk2 in the sperm by RT-PCR and Western blot.@*RESULTS@#Statistically significant differences were not found in sperm DFI among the control, OS, AS, and OAS groups (21.24±6.93, 19.67±7.64, 21.52±6.92, and 19.28±11.55, P>0.05), but observed in sperm concentration, progressive motility, and viability between the DFI >30% and DFI ≤30% groups (P<0.01). Compared with the normal control, sperm viability was remarkably decreased in the OS, AS, and OAS groups (［83.48±9.87］% vs ［63.86±9.16］%, ［50.45±16.99］%, and ［39.21±15.74］%, P<0.05). RT-PCR showed remarkable differences among the control, OS, AS, and OAS groups in the relative expression level of Chk1 mRNA (0.73±0.22, 0.62±0.14, 1.03±0.39, and 0.92±0.071, P<0.01), which was correlated positively with sperm concentration (b = 80.661, P<0.01) but negatively with sperm motility (b = －19.275, P < 0.01), as well as in that of Chk2 mRNA (0.66±0.30, 0.27±0.09, 0.59±0.19, and 0.42 ± 0.11, P<0.01), which was correlated negatively with sperm concentration (b = －90.809, P<0.01) but positively with sperm motility (b = 27.507, P <0.01). The relative expression levels of the Chk1 protein were significantly different among the four groups (0.63±0.05, 0.42±0.03, 1.13±0.08, and 0.87±0.07, P<0.01), which was correlated positively with sperm concentration (b = 55.74, P<0.01) but negatively with sperm motility (b =－22.649, P<0.01), and so were those of the Chk2 protein (1.23±0.36, 0.37±0.16, 0.87±0.08, and 0.68±0.12, P<0.01), which was correlated negatively with sperm concentration (b =－53.001, P<0.01) but positively with sperm motility (b = 16.676, P < 0.01).@*CONCLUSIONS@#Chk1 and Chk2 are significantly expressed in human sperm. In case of sperm DNA damage, up-regulated Chk1 expression may enhance sperm apoptosis and lead to asthenospermia, while increased Chk2 expression may inhibit spermatogenesis and result in oligospermia.

TBX2 gene mutation and the clinical significance of related proteins expression in ma-lignant peripheral nerve sheath tumor / 中国肿瘤临床

Objective:To detect genomic aberrations and investigate the expression and clinical significance of TBX2,CHK2, and p53 in malignant peripheral nerve sheath tumor (MPNST) tissues. Methods:We collected 63 cases of MPNST tissue samples, which were re-moved by resection and were confirmed by pathology, from January 1991 to December 2011 in Department of Bone and Sofer Tissue Tumor, Tianjin Medical University Cancer Institute and Hospital. Twelve fresh tumor samples with qualified DNA quality were selected from the above 63 cases of tissue samples. Genome abnormalities of 12 MPNST tissues were detected by next-generation sequencing. The protein expression levels of TBX2, CHK2, and p53 in 63 MPNST tissue samples were assessed by immunohistochemistry staining. Results:One case of TBX2 gene mutation was observed out of the 12 MPNST tissue samples. In 63 MPNST tissue samples, the protein expression rates of TBX2, CHK2, and p53 were 60.3%(38/63), 47.6%(30/63), and 30.2%(19/63), respectively. TBX2 expression was sig-nificantly correlated with AJCC (American Joint Committee on Cancer, AJCC) stage, recurrence, and metastasis (P<0.05). TBX2 expres-sion was directly correlated with that of CHK2 (r=0.254, P=0.045), and CHK2 expression was directly correlated with that of p53 (r=0.343, P=0.006). In terms of the disease-free survival and overall survival time, patients with high expression levels of TBX2, CHK2, and p53 had significantly worse prognosis than patients with low expression levels of TBX2, CHK2, and p53(all P<0.05). TBX2, CHK2, and p53 were independent prognostic factors of MPNST. Conclusion:TBX2 and its associated proteins may play important roles in MPNST development and progression. Detecting TBX2 expression may provide the theoretical basis for estimating the prognosis of patients with MPNST.

Changes of the cell cycle regulators and cell cycle arrest in cervical cancer cells after cisplatin therapy / 西安交通大学学报·英文版

Objective: To investigate the changes of the cell cycle regulators ATM, Chk2 and p53 and cell cycle arrest in HeLa cells after cisplatin therapy. Methods: The proliferation-inhibiting rates of HeLa cells induced by cisplatin of different concentrations were measured by MTT assays. The mRNA and protein expressions of ATM, Chk2 and p53 of HeLa cells with and without cisplatin were detected by RT-PCR and Western blot, respectively. The cell cycle analysis was conducted by flow cytometric analysis. Results: Cisplatin inhibited the proliferation of HeLa cells in a dose- and time-dependent manner. The mRNA and protein expressions of ATM, Chk2 and p53 were increased in HeLa cells treated with cisplatin. The cell cycle was arrested in G2/M phase in HeLa cells treated with cisplatin. Conclusion: Activation of ATM, Chk2 and p53 might be critical in determining whether cells survive or undergo apoptosis. Targeting ATM, Chk2 and p53 pathway might be a promising strategy for reversing chemoresistance to cisplatin in cervical cancer.

Changes of the cell cycle regulators and cell cycle arrest in cervical cancer cells after cisplatin therapy / 药物分析学报

Objective To investigate the changes of the cell cycle regulators ATM, Chk2 and p53 and cell cycle arrest in HeLa cells after cisplatin therapy. Methods The proliferation-inhibiting rates of HeLa cells induced by eisplatin of different concentrations were measured by MTT assays. The mRNA and protein expressions of ATM, Chk2 and p53 of HeLa cells with and withont cisplatin were detected by RT-PCR and Western blot, respectively. The cell cycle analysis was conducted by flow cytometric analysis. Results Cisplatin inhibited the proliferation of HeLa cells in a dose- and time-dependent manner. The mRNA and protein expressions of ATM, Chk2 and p53 were increased in HeLa cells treated with cisplatin. The cell cycle was arrested in G2/M phase in HeLa cells treated with cisplatin. Conclusion Activation of ATM, Chk2 and p53 might be critical in determining whether cells survive or undergo apoptesis. Targeting ATM, Chk2 and p53 pathway might he a promising strategy for reversing chemoresistance to clsplatin in cervical cancer.

Expression of Chk2 and P53 in Sporadic Breast Cancer / 한국유방암학회지

PURPOSE: In response to DNA damage, Chk2 (CHEK2) is involved in cell cycle checkpoint. Chk2 is activated by the upstream ATM kinase and then directly phosphorylate p53 at serine 20. Other substrates for Chk2 are BRCA1, Cdc25A, Cdc25C, mdm2. Germ line mutations of Chk2 have been identified in Li-Fraumeni syndrome with normal p53 alleles. There are few reports on somatic mutations of Chk2 in osteosarcoma, lung cancer, breast cancer, testicular germ cell tumor, ovarian cancer. In this study, we have analyzed 30 breast cancer specimens to understand the relationship of Chk2 and P53 in the pathogenesis of sporadic breast cancer. METHODS: We performed an immunohistochemical studies for Chk2, P53 in the specimens from 30 breast cancer patients. We designed entire intronic primers and searched for Chk2mutations in 7 cases by DNA sequence analysis of the entire coding region. RESULTS: Seven of 30 (23.3%) breast cancers had reduced immuno-expression of Chk2, one of them (1/7, 14.3%) showed a p53 immuno-expression and all of them revealed no Chk2 mutation. CONCLUSION: Expression of Chk2 protein more reduced in breast cancer with no abnormal p53 immuno-expression. No Chk2 mutation was found in all of Chk2 reduced expression, we hypothesize that there may be a posttranscriptional/ posttranslational mechanism (s) in breast caner to downregulate Chk2 protein expression.