Aurora A Kinase Plays a Key Role in Mitosis Skip during Senescence Induced by Ionizing Radiation / 生物医学与环境科学（英文）

OBJECTIVE@#To investigate the fate and underlying mechanisms of G2 phase arrest in cancer cells elicited by ionizing radiation (IR).@*METHODS@#Human melanoma A375 and 92-1 cells were treated with X-rays radiation or Aurora A inhibitor MLN8237 (MLN) and/or p21 depletion by small interfering RNA (siRNA). Cell cycle distribution was determined using flow cytometry and a fluorescent ubiquitin-based cell cycle indicator (FUCCI) system combined with histone H3 phosphorylation at Ser10 (pS10 H3) detection. Senescence was assessed using senescence-associated-β-galactosidase (SA-β-Gal), Ki67, and γH2AX staining. Protein expression levels were determined using western blotting.@*RESULTS@#Tumor cells suffered severe DNA damage and underwent G2 arrest after IR treatment. The damaged cells did not successfully enter M phase nor were they stably blocked at G2 phase but underwent mitotic skipping and entered G1 phase as tetraploid cells, ultimately leading to senescence in G1. During this process, the p53/p21 pathway is hyperactivated. Accompanying p21 accumulation, Aurora A kinase levels declined sharply. MLN treatment confirmed that Aurora A kinase activity is essential for mitosis skipping and senescence induction.@*CONCLUSION@#Persistent p21 activation during IR-induced G2 phase blockade drives Aurora A kinase degradation, leading to senescence via mitotic skipping.

Advances in live-imaging aging reporter mice / 生理学报

Aging is an independent risk factor for chronic diseases in the elderly, and understanding aging mechanisms is one of the keys to achieve early prevention and effective intervention for the diseases. Aging process is dynamic and systemic, making it difficult for mechanistic study. With recent advances in aging biomarkers and development of live-imaging technologies, more and more reporter mouse models have been generated, which can live monitor the aging process, and help investigate aging mechanisms at systemic level and develop intervention strategies. This review summarizes recent advances in live-imaging aging reporter mouse models based on widely used aging biomarkers (p16Ink4a, p21Waf1/Cip1, p53 and Glb1), and discusses their applications in aging research.

The effect of 5-aminoimidazole-4-carboxamide-ribonucleoside was mediated by p38 mitogen activated protein kinase signaling pathway in FRO thyroid cancer cells

BACKGROUND/AIMS: 5'-Adenosine monophosphate (AMP)-activated protein kinase (AMPK) is a cellular energy sensor that monitors intracellular AMP/adenosine triphosphate (ATP) ratios and is a key regulator of the proliferation and survival of diverse malignant cell types. In the present study, we investigated the effect of activating AMPK by 5-aminoimidazole-4-carboxamide-ribonucleotide (AICAR) in thyroid cancer cells. METHODS: We used FRO thyroid cancer cells harboring the BRAF(V600E) mutation to examine the effect of AICAR on cell proliferation and cell survival. We also evaluated the involvement of mitogen-activated protein kinase (MAPK) pathways in this effect. RESULTS: We found that AICAR treatment promoted AMPK activation and suppressed cell proliferation and survival by inducing p21 accumulation and activating caspase-3. AICAR significantly induced activation of p38 MAPK, and pretreatment with SB203580, a specific inhibitor of the p38 MAPK pathway, partially but significantly rescued cell survival. Furthermore, small interfering RNA targeting AMPK-alpha1 abolished AICAR-induced activation of p38 MAPK, p21 accumulation, and activation of caspase-3. CONCLUSIONS: Our findings demonstrate that AMPK activation using AICAR inhibited cell proliferation and survival by activating p38 MAPK and proapoptotic molecules in FRO thyroid cancer cells. These results suggest that the AMPK and p38 MAPK signaling pathways may be useful therapeutic targets to treat thyroid cancer.

Growth Inhibition of Hepatocellular Carcinoma Huh7 Cells by Lactobacillus casei Extract

PURPOSE: Lactobacillus casei (L. casei) is known to exert anti-proliferation effects on many types of cancer cells. However, the effect of L. casei on liver cancer has not been reported. Accordingly, the aim of this study was to determine the anti-cancer effect of L. casei extract on Huh7 cells. MATERIALS AND METHODS: L. casei ATCC393 extract was prepared and purified. After the treatment of L. casei extract on Huh7 cells, cell viability, cell cycle arrest and cell death were analyzed by flow cytometry. The expression levels of tumor necrosis factor-alpha receptor 1 (TNFR1) and death receptor 3 (DR3) mRNA related with extrinsic apoptosis were assessed by reverse transcription polymerase chain reaction. Additionally, P21 and P27 cell cycle proteins as well as Caspase-3, -8, -9, phospho-Bad and Bcl-2 apoptosis proteins were analyzed by western blot analysis. To determine the effect of L. casei extract on cancer stem-like cells, we analyzed changes in side population fraction through flow cytometry. RESULTS: The cell viability of Huh7 cells treated with L. casei extract was decreased by 77%, potentially owing to increases in the rates of Huh7 cells arrested in the G2/M phase (3% increase) and that underwent apoptosis (6% increase). The expression levels of TNFR1 and DR3 mRNA, as well as P21 and P27 cell cycle proteins, were increased. Meanwhile, the expressions of caspase-8, -9, phospho-Bad and Bcl-2 proteins decreased. However, in the case of side population cells, no remarkable changes were observed. CONCLUSION: L. casei extract exerts a potent anti-tumor effect on the viability of liver cancer cells, although not on cancer stem-like cells.

Effects of Chromosomal Polyploidy on Survival of Colon Cancer Cells / 대한소화기학회지

BACKGROUND/AIMS: Tetraploid cells are frequently observed in the inflamed mucosal epithelial cells of the patients with Barrett's esophagus or chronic ulcerative colitis. Polyploidy often occurs during cell fusion, abortive cell cycle, and endoreplication. Most tetraploid cells are engaged to apoptotic pathway, but some remaining stable tetraploid cells consequently cause aneuploidization and chromosomal instability. We investigated whether tetraploid cells could acquire survival advantage and hold a dominant position for natural selection. METHODS: We established tetraploid cell line (HCT116GH) from parental diploid colorectal cancer cell line (HCT116) via PEG-mediated cell fusion and compared its cell viability, cell cycle response and apoptotic fractions responded to H2O2 with diploid HCT116 and p53 suppressed HCT116/H6 cell lines. RESULTS: Using MTT assay, plating efficiency and clonogenicity, we evaluated the survival of each cell line. Tetraploid cell line HCT116GH demonstrated an 83 fold greater resistance to 100 microM H2O2 than the parental diploid HCT116, and 6 fold greater than even the p53 negative diploid HCT116/E6. Cellular sensitivity, G2/M arrests, and apoptotic proportion were observed less in response to H2O2 in HCT116GH compared with HCT116 and HCT116/E6. HCT116GH expressed lower level of p53 and p21 than diploid HCT116. CONCLUSIONS: Stable tetraploid cell lines showed enhanced viability in comparison to parental diploid cell lines. The enhanced viability observed in tetraploidization surpassed that from downregulation of p53. Frequent appearance of tetraploid cells in stressful condition can be caused by natural selection owing to their enhanced viability and may consequently contribute to cancer cell transformation.

Expression of G1 Cell Cycle Regulators in Rat Liver upon Repeated Exposure to Thioacetamide / 대한간학회지

BACKGROUND/AIMS: Eukaryotic cell cycle is regulated by signal transduction pathways mediated by complexes of cyclin dependent kinases (CDKs) and their partner cyclins, or by interaction with CDK inhibitors. Thioacetamide (TA) is a weak hepatocarcinogen causing several types of liver damage in a dose dependent manner and ultimately producing malignant transformation. We investigated alterations of expression of cell cycle regulators in the rat liver, involved in G1 entry and progression during TA administration. METHODS: We studied expression patterns of cyclin D1, CDK4, CDK6, p21(CIP1) and p16(INK4a) during daily intraperitoneal injection of low dose TA (50 mg/kg) till 7 day. We used western blot and immunohistochemistry for detection. RESULTS: Expression of cyclin D1, CDK4, CDK6 and p21(CIP1) increased from 6 hour and peaked at 2, 3 day, then decreased next 2 days, and re-increased at 6 day. Cytoplasmo-nuclear translocation of cyclin D1 and p21(CIP1) was evident within 1 day and prominent at 2 and 7 day. Expression of p16(INK4a) increased immediately after TA treatment and remarkably increased from 3 day and progressed till 7 day, showing cytoplasmic location, suggestive of inactive form. Most of in situ immunoreactions occurred at the centrilobular hepatocytes. Concomitant nuclear translocation of p21(CIP1) and cyclin D1, different with p16(INK4a) suggests that p21(CIP1) might be a transporter for nuclear translocation rather than cell cycle inhibitor. CONCLUSIONS: Daily administration of low dose TA makes cell cycle open and G1 progress, possibly due to cyclin D1, CDK4 and CDK 6, their transporter p21(CIP1), and inactive p16(INK4a), which occur at quiescent hepatocytes, not stem cells.

Expression of Cyclin Dependent Kinase Inhibitors of KIP Family in Gastric Cancer / 대한소화기학회지

BACKGROUND/AIMS: The cyclin-dependent kinase inhibitors (CDKI) including p21, p27, and p57 of the kinase inhibitor protein (KIP) family are negative regulators of cell cycle progression and potentially act as tumor suppressor. Tumor behavior and growth are influenced by the extent of tumor cell proliferation. The aim of this study was to evaluate the expression of KIP family CDKI in gastric cancer tissue, and to examine the relationship between these expression and various clinicopathological parameters including tumor cell proliferation. METHODS: We conducted an immunohistochemical analysis of p21, p27, and p57 expression in 109 gastric cancer tissues. Tumor cell proliferation was assessed by immunohistochemistry with antibody against Ki-67. RESULTS: Negative expression of p21, p27, and p57 was demonstrated in 45.9%, 65.1%, and 57.8% of cancer tissues, respectively. Negative expression of p21 correlated with larger tumor size, poor differentiation, depth of invasion, lymph node metastasis and advanced TNM stage (p=0.048, 0.041, 0.001, 0.005, and 0.001 respectively). Negative expression of p21 correlated with poor survival (p=0.037). Tumors with negative p21 expression had higher Ki-67 expression than those with positive p21 expression (p=0.024). No significant correlation could be observed between status of p27 and p57 expression and various clinicopathological parameters including survival and tumor cell proliferation. CONCLUSIONS: These results suggest that negative expression of p21 may play an important role in carcinogenesis by stimulating tumor cell proliferation, and may help in predicting the prognosis of gastric cancer.