Research Progress on G2/M Arrest in Breast Cancer Cells by Active Compounds of Traditional Chinese Medicine / 中国实验方剂学杂志

The global incidence of breast cancer has increased year by year. Breast cancer has the highest mortality rate in female patients with malignant tumors. Traditional Chinese medicine（TCM） has made great contribution to health of human being， improving the overall curative effect， reducing the patients' pain， improving the quality of life and alleviating adverse reactions in patients. TCM and its active compounds can inhibit the proliferation of breast cancer cells by inducing cell cycle arrest， invasion， metastasis and reversing multidrug resistance. The effect of the compounds in TCM is obvious on inducing the arrest of the breast cancer cells cycle. It′s a novel method to fight against breast cancer by influencing the progress of the breast cancer cell cycle and inducing the cell cycle arrest in breast cancer cells. Lots of studies have shown that the G2/M phase checkpoint which transition from gap-phase （G2 phase） to mitotic phase （M phase） in the cell cycle is the key point for cell survival or death. Many antitumor drugs can inhibit the proliferation of tumor cells through the cell cycle arrest. We summarized the domestic and foreign literatures in recent years， and comprehensively explained the research progress on the related regulatory molecules in G2/M arrest. In addition， we summarized and sorted out the researches on the methods and ways of alkaloids， polysaccharides， terpenes， flavonoids， saponins and other active compounds of TCM in inducing the G2/M arrest of human breast cancer cells. By summarizing the active compounds of various Chinese medicines in inducing G2/M arrest of breast cancer cells， and reviewing the research progress on mechanism of active TCM compounds for inhibiting the proliferation of breast cancer cells， we will， in this paper， investigate the mechanism of active TCM compounds for inhibiting the proliferation of breast cancer cells through inducing G2/M arrest of human breast cancer cells， so as to provide a scientific basis for in-depth research on the anti-breast cancer mechanism of the active compounds in TCM.

RNA-sequencing Profiles of Cell Cycle–Related Genes Upregulated during the G2-Phase in Giardia lamblia

To identify the component(s) involved in cell cycle control in the protozoan Giardia lamblia, cells arrested at the G1/S- or G2-phase by treatment with nocodazole and aphidicolin were prepared from the synchronized cell cultures. RNA-sequencing analysis of the 2 stages of Giardia cell cycle identified several cell cycle genes that were up-regulated at the G2-phase. Transcriptome analysis of cells in 2 distinct cell cycle stages of G. lamblia confirmed previously reported components of cell cycle (PcnA, cyclin B, and CDK) and identified additional cell cycle components (NEKs, Mad2, spindle pole protein, and CDC14A). This result indicates that the cell cycle machinery operates in this protozoan, one of the earliest diverging eukaryotic lineages.

ATM Signaling Pathway Is Implicated in the SMYD3-mediated Proliferation and Migration of Gastric Cancer Cells

PURPOSE: We previously found that the histone methyltransferase suppressor of variegation, enhancer of zeste, trithorax and myeloid-nervy-deformed epidermal autoregulatory factor-1 domain-containing protein 3 (SMYD3) is a potential independent predictive factor or prognostic factor for overall survival in gastric cancer patients, but its roles seem to differ from those in other cancers. Therefore, in this study, the detailed functions of SMYD3 in cell proliferation and migration in gastric cancer were examined. MATERIALS AND METHODS: SMYD3 was overexpressed or suppressed by transfection with an expression plasmid or siRNA, and a wound healing migration assay and Transwell assay were performed to detect the migration and invasion ability of gastric cancer cells. Additionally, an MTT assay and clonogenic assay were performed to evaluate cell proliferation, and a cell cycle analysis was performed by propidium iodide staining. Furthermore, the expression of genes implicated in the ataxia telangiectasia mutated (ATM) pathway and proteins involved in cell cycle regulation were detected by polymerase chain reaction and western blot analyses. RESULTS: Compared with control cells, gastric cancer cells transfected with si-SMYD3 showed lower migration and invasion abilities (P<0.05), and the absence of SMYD3 halted cells in G2/M phase and activated the ATM pathway. Furthermore, the opposite patterns were observed when SMYD3 was elevated in normal gastric cells. CONCLUSIONS: To the best of our knowledge, this study provides the first evidence that the absence of SMYD3 could inhibit the migration, invasion, and proliferation of gastric cancer cells and halt cells in G2/M phase via the ATM-CHK2/p53-Cdc25C pathway. These findings indicated that SMYD3 plays crucial roles in the proliferation, migration, and invasion of gastric cancer cells and may be a useful therapeutic target in human gastric carcinomas.

p53 Prevents Immature Escaping from Cell Cycle G2 Checkpoint Arrest through Inhibiting cdk2-dependent NF-Y Phosphorylation / Journal of the Korean Cancer Association, 대한암학회지

PURPOSE: Recent studies have suggested that p53 regulates the G2 checkpoint in the cell cycle and this function is required for the maintenance of genomic integrity. In this study, we addressed a role of p53 in escaping from cell cycle G2 arrest following DNA damage. MATERIALS AND METHODS: Cell cycle checkpoint arrest in the human colon cancer cell line HCT116 and its derivatives carry p53 or p21 deletions, were examined by FACS analysis, immunoprecipitation, Western blot and IP-kinase assay. RESULTS: While the cells with functional p53 were arrested at both the G1 and G2 checkpoints, the p53-deficient cells failed to arrest at G1, but they were arrested at G2. However, the p53-deficient cells failed to sustain G2 checkpoint arrest and they entered mitosis earlier than did the p53-positive cells and so this resulted in extensive cell death. Cdc2 kinase becomes reactivated in p53-deficient cells in association with entry into mitosis, but not in the p53-positive cells. Upon DNA damage, the p21-deficient cells, like the p53-negative cells, not only failed to repress cdk2- dependent NF-Y phosphorylation, but they also failed to repress the expression of such cell cycle G2-regulatory genes as cdc2, cyclin B, RNR-R2 and cdc25C, which have all been previously reported as targets of NF-Y transcription factor. CONCLUSION: p53 is essential to prevent immature escaping from cell cycle G2 checkpoint arrest through p21-mediated cdk2 inactivation, and this leads to inhibition of cdk2-dependent NF-Y phosphorylation and NF-Y dependent transcription of the cell cycle G2-rgulatory genes, including cdc2 and cyclin B.