CHK1 inhibitor SCH900776 suppresses proliferation and migration of U251 cells / 中国病理生理杂志

AIM:To investigate the effect of SCH900776, an inhibitor of checkpoint kinase 1(CHK1), on the proliferation and migration abilities of human glioma U 251 cells.METHODS:The cell viability was detected by MTT assay,and cell proliferation was determined by cell colony formation assay.Cell cycle distribution was analyzed by flow cy-tometry.Wound healing assay was used to determine the cell migration ability.The protein levels were determined by Western blot.RESULTS: SCH900776 inhibited the growth of U251 cells in a dose-dependent manner(P <0.05). SCH900776 treatment substantially induced U251 cell cycle arrest in S and G 2/M phases by decreasing the level of cell di-vision cycle protein 2(Cdc2)and p-Cdc2.Moreover,SCH900776 inhibited the cell migration.Western blot results indi-cated that SCH900776 increased the phosphorylation level of p 38 MAPK and inhibited the activation of Akt.CONCLU-SION:SCH900776 inhibits the proliferation and migration abilities in human U 251 cells by promoting the phosphorylation of p38 MAPK and suppressing the activation of Akt.

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.

Research progress of checkpoint kinase 1 and DNA damage response pathway in tumors / 肿瘤研究与临床

The main reason of recurrence and metastasis in breast cancer is the resistance for the radiotherapy and chemotherapy,and the mechanism of radio-resistance and chemo-resistance may be related to the DNA damage response (DDR).There is a complicated system of the DDR pathway,including cell cycle checkpoint,DNA repair,transcription and apoptosis to maintain the integrity of cell genes.In the cancer treatment,DDR occurs in various kinds of cytotoxic drugs and radiation to cause genetic damage,which limits the curative effect of chemotherapy and radiotherapy.This promotes the targeted therapy of DDR pathway,especially checkpoint kinase 1 (CHK1).Recently,the new viewpoint supports that CHK1 is a main marker of the DDR pathway activation,which shows that CHK1 not only activates the check point but also affects the DNA repair and apoptosis directly.Thus,the role of CHK1 in DDR will promote CHK1 inhibitor to be one of the new treatment strategies for the cancer patients who resist the radiation and chemotherapy.

Validation of a method for the determination of thiocyanate in human plasma by UV/VIS spectrophotometry and application to a Phase I clinical trial of GDC-0425

The development and validation of a method for the determination of concentrations of thiocyanate in human plasma are described here. A modified colorimetric method of Bowler was used with the following alteration in Monica Manual, Part III. In order to obtain the same sensitivity in low amounts of clinical samples, quartz SUPRASIL(R) micro cuvettes have been used. The quantitation range was between 25-500 microM. Accuracy and precision of the quality control samples, linearity of the calibration curve, dilution, spike recovery and stability under various conditions were evaluated in the validation of the method and all demonstrated acceptable results. All validation results met good laboratory practice acceptance and FDA requirements to be acceptable for application in clinical trials. The validated method has been used for a Phase I clinical study in cancer patients orally administered with either 60 mg or 80 mg of GDC-0425 containing a cyanide (CN-) group. The thiocyanate levels from patients before and after drug administration showed no clinically significant differences.

Progress in the study of cell cycle checkpoint kinase 1 inhibitors / 中国药学杂志

To review the recent research advances on the cell cycle checkpoint kinase 1 (Chk1) inhibitors. METHODS: Through searching and summarying literatures of domestic and abroad, the research progress of the Chk1 inhibitors were introduced comprehensively. RESULTS AND CONCLUSION: Chk1 inhibitors combining with DNA damaging agents have better anti-tumor efficacy. With the deepening studies on the Chk1 inhibitors and their structure-activity relationship, Chk1 inhibitors will have broader development prospects and play more important roles in the treatment of cancer.

Growth inhibitory effect and Chk1-dependent signaling involved in G2/M arrest on human gastric cancer cells induced by diallyl disulfide

Diallyl disulfide (DADS) inhibits growth and induces cell cycle G2/M arrest in human gastric cancer MGC803 cells. In this study, 15 mg/L DADS exerted similar effects on growth and cell cycle arrest in human gastric cancer BGC823 cells. Due to the importance of cell cycle redistribution in DADS-mediated anti-carcinogenic effects, we investigated the role of checkpoint kinases (Chk1 and Chk2) during DADS-induced cell cycle arrest. We hypothesized that DADS could mediate G2/M phase arrest through either Chk1 or Chk2 signal transduction pathways. We demonstrated that DADS induced the accumulation of phosphorylated Chk1, but not of Chk2, and that DADS down-regulated Cdc25C and cyclin B1. The expression of mRNA and total protein for Chkl and Chk2 was unchanged. Chk1 is specifically phosphorylated by ATR (ATM-RAD3-related gene). Western blot analysis showed that phospho-ATR was activated by DADS. Taken together, these data suggest that cell cycle G2/M arrest, which was associated with accumulation of the phosphorylated forms of Chk1, but not of Chk2, was involved in the growth inhibition induced by DADS in the human gastric cancer cell line BGC823. Furthermore, the DADS-induced G2/M checkpoint response is mediated by Chk1 signaling through ATR/Chk1/Cdc25C/cyclin B1, and is independent of Chk2.

Identification of novel substrates for human checkpoint kinase Chk1 and Chk2 through genome-wide screening using a consensus Chk phosphorylation motif

Checkpoint kinase 1 (Chk1) and Chk2 are effector kinases in the cellular DNA damage response and impairment of their function is closely related to tumorigenesis. Previous studies revealed several substrate proteins of Chk1 and Chk2, but identification of additional targets is still important in order to understand their tumor suppressor functions. In this study, we screened novel substrates for Chk1 and Chk2 using substrate target motifs determined previously by an oriented peptide library approach. The potential candidates were selected by genome-wide peptide database searches and were examined by in vitro kinase assays. ST5, HDAC5, PGC-1alpha, PP2A PR130, FANCG, GATA3, cyclin G, Rad51D and MAD1alpha were newly identified as in vitro substrates for Chk1 and/or Chk2. Among these, HDAC5 and PGC-1alpha were further analyzed to substantiate the screening results. Immunoprecipitation kinase assay of full-length proteins and site-directed mutagenesis analysis of the target motifs demonstrated that HDAC5 and PGC-1alpha were specific targets for Chk1 and/or Chk2 at least in vitro.