P2Y11 impairs cell proliferation by induction of cell cycle arrest and sensitizes endothelial cells to cisplatin-induced cell death

Extracellular ATP mediates a wide range of physiological effects, including cell proliferation, differentiation, maturation, and migration. However, the effect of ATP on cell proliferation has been contradictory, and the mechanism is not fully understood. In the current study, we found that extracellular ATP significantly inhibited the proliferation of human umbilical vein endothelial cells (HUVECs) and human aortic endothelial cells (HAECs). Treatment with ATP did not induce cell apoptosis but instead induced cell cycle arrest in S phase. ATP induced the phosphorylation of ERK1/2, but the ERK inhibitors, U0126 and PD9809, did not regulate the inhibition of cell proliferation induced by ATP. However, ATP-induced inhibition of cell proliferation was blocked by suramin, a nonspecific antagonist of the P2Y receptors, and endothelial cells expressed P2Y11, a P2Y receptor that specifically binds ATP. Moreover, the down-regulation of P2Y11 by RNA interference not only reversed the inhibition of cell proliferation but also ameliorated cell cycle arrest in S phase. In addition, P2Y11 sensitized endothelial cells to cisplatin-induced cell death by down-regulation of the expression of Bcl-2. Taken together, these results suggest that extracellular ATP impairs cell proliferation by triggering signaling to induce cell cycle arrest and sensitizes cell to death via P2Y11 in endothelial cells.     

Phthalocyanine-mediated photodynamic therapy induces cell death and a G0/G1 cell cycle arrest in cervical cancer cells

We have developed a series of novel photosensitizers which have potential for anticancer photodynamic therapy (PDT). Photosensitizers include zinc phthalocyanine tetra-sulphonic acid and a family of derivatives with amino acid substituents of varying alkyl chain length and degree of branching. Subcellular localization of these photosensitizers at the phototoxic IC(50) concentration in human cervical carcinoma cells (SiHa Cells) was similar to that of the lysosomal dye Lucifer Yellow. Subsequent nuclear relocalization was observed following irradiation with 665nm laser light. The PDT response was characterized using the Sulforhodamine B cytotoxicity assay. Flow cytometry was used for both DNA cell cycle and dual Annexin V-FITC/propidium iodide analysis. Phototoxicity of the derivatives was of the same order of magnitude as for tetrasulphonated phthalocyanine but with an overall trend of increased phototoxicity with increasing amino acid chain length. Our results demonstrate cell death, inhibition of cell growth, and G(0)/G(1) cell cycle arrest during the phthalocyanine PDT-mediated response.     

ALG-2 knockdown in HeLa cells results in G2/M cell cycle phase accumulation and cell death

ALG-2 (apoptosis-linked gene-2 encoded protein) has been shown to be upregulated in a variety of human tumors questioning its previously assumed pro-apoptotic function. The aim of the present study was to obtain insights into the role of ALG-2 in human cancer cells. We show that ALG-2 downregulation induces accumulation of HeLa cells in the G2/M cell cycle phase and increases the amount of early apoptotic and dead cells. Caspase inhibition by the pan-caspase inhibitor zVAD-fmk attenuated the increase in the amount of dead cells following ALG-2 downregulation. Thus, our results indicate that ALG-2 has an anti-apoptotic function in HeLa cells by facilitating the passage through checkpoints in the G2/M cell cycle phase.     

Polycystin-1 induced apoptosis and cell cycle arrest in G0/G1 phase in cancer cells

Studies have shown that polycystin-1, encoded by PKD1, the major ADPKD, may have a central role in regulating both apoptosis and proliferation, which could prevent the malignant transformation of affected cells. However, as a putative tumor suppressor, direct studies on the possibility that polycystin-1 may play a role in cancer cells' biological properties have not yet been reported. We have demonstrated that the apoptosis of cancer cells was induced by overexpression of polycystin-1. After transfection with polycystin-1, three cancer cell lines, HepG2, A549, and SW480, showed significantly increased apoptosis compared with the respective control groups. This was accompanied by cell cycle arrest at G(0)/G(1) phase, whereas cell proliferation was not significantly affected. Overexpression of polycystin-1 induces apoptosis in cancer cells, at least partially, through Wnt and a caspase-dependent pathway.     

A synthetic 2,3-diarylindole induces microtubule destabilization and G2/M cell cycle arrest in lung cancer cells

The anticancer potential of a synthetic 2,3-diarylindole (PCNT13) has been demonstrated in A549 lung cancer cells by inducing both apoptosis and autophagic cell death. In this report, we designed to connect a fluorophore to the compound via a hydrophilic linker for monitoring intracellular localization. The best position for linker attachment was identified from cytotoxicity and effect on cell morphology of newly synthesized PCNT13 derivatives bearing hydrophilic linker. Cytotoxicity and effect on cell morphology related to the parental compound were used to identify the optimum position for linker attachment in the PCNT13 chemical structure. The fluorophore-PCNT13 conjugate was found to localize in the cytoplasm. Microtubules were found to be one of the cytosolic target proteins of PCNT13, as the compound could inhibit tubulin polymerization in vitro. A molecular docking study revealed that PCNT13 binds at the colchicine binding site on the α/β-tubulin heterodimer. The effect of PCNT13 on microtubule dynamics caused cell cycle arrest in the G2/M phase as analyzed by flow cytometric analysis.     

Ras-dependent cell cycle commitment during G2 phase

Synchronization used to study cell cycle progression may change the characteristics of rapidly proliferating cells. By combining time-lapse, quantitative fluorescent microscopy and microinjection, we have established a method to analyze the cell cycle progression of individual cells without synchronization. This new approach revealed that rapidly growing NIH3T3 cells make a Ras-dependent commitment for completion of the next cell cycle while they are in G2 phase of the preceding cell cycle. Thus, Ras activity during G2 phase induces cyclin D1 expression. This expression continues through the next G1 phase even in the absence of Ras activity, and drives cells into S phase.     

Acyldepsipeptides inhibit the growth of renal cancer cells through G1 phase cell cycle arrest

Acyldepsipeptides are a group of potent antibiotics discovered in the secondary metabolites of Streptomyces species. However, besides the function of antibiotics, no other activities have been reported about these important compounds so far. In the course of searching the natural products as chemotherapeutic agents for renal cell carcinoma, we found that ADEP1, a major metabolic component of Streptomyces hawaiiensis NRRL 15010, could effectively inhibit the growth of 786-O, 769-P, and ACHN renal carcinoma cells in MTT assay. Flow cytometric analysis demonstrated that ADEP1 could block the cell cycle arrested at G1 phase. Moreover, it was found that ADEP1 down-regulated the expressions of cyclin D1, CDK4 and PCNA and inhibited activity of MAPK–ERK pathway by detection of decreased expression of phosphorylated ERK1/2 and c-Fos in 786-O and 769-P cells by Western blotting. To our knowledge, this is the first report concerning to the antitumor activities of acyldepsipeptides. Based on these results, ADEP1 may become a promising lead compound to be developed a novel chemotherapeutic agent for treatment of renal carcinoma.     

G1 cell cycle arrest due to the inhibition of erbB family receptor tyrosine kinases does not require the retinoblastoma protein

The erbB receptor family (EGFr, erbB-2, erbB-3, and erbB-4) consists of transmembrane glycoproteins that transduce extracellular signals to the nucleus when activated. erbB family members are widely expressed in epithelial, mesenchymal, and neuronal cells and contribute to the proliferation, differentiation, migration, and survival of these cell types. The present study evaluates the effects of erbB family signaling on cell cycle progression and the role that pRB plays in regulating this process. ErbB family RTK activity was inhibited by PD 158780 in the breast epithelial cell line MCF10A. PD 158780 (0.5 microM) inhibited EGF-stimulated and heregulin-stimulated autophosphorylation and caused a G1 cell cycle arrest within 24 h, which correlated with hypophosporylation of pRB. MCF10A cells lacking functional pRB retained the ability to arrest in G1 when treated with PD 158780. Both cell lines showed induction of p27(KIP1) protein when treated with PD 158780 and increased association of p27(KIP1) with cyclin E-CDK2. Furthermore, CDK2 kinase activity was dramatically inhibited with drug treatment. Changes in other pRB family members were noted with drug treatment, namely a decrease in p107 and an increase in p130. These findings show that the G1 arrest induced through inhibition of erbB family RTK activity does not require functional pRB.     

蛋白激酶C抑制剂staurosporine对HeLa细胞周期的影响

蛋白激酶Ｃ抑制剂ｓｔａｕｒｏｓｐｏｒｉｎｅ对ＨｅＬａ细胞周期的影响石法武＊任洪波张兆山＊＊王会信周廷冲（军事医学科学院基础医学研究所,＊＊生物工程研究所,北京１００８５０ＴｈｅｅｆｅｃｔｏｆｓｔａｕｒｏｓｐｏｒｉｎｅｏｎｔｈｅｃｅｌｃｙｃｌｅｏｆＨｅ...     

SOCS3 regulates p21 expression and cell cycle arrest in response to DNA damage

Genotoxic agents such as ionizing radiation trigger cell cycle arrest at the G1/S and G2/M checkpoints, allowing cells to repair damaged DNA before entry into mitosis. DNA damage-induced G1 arrest involves p53-dependent expression of p21 (Cip1/Waf-1), which inhibits cyclin-dependent kinases and blocks S phase entry. While much of the core DNA damage response has been well-studied, other signaling proteins that intersect with and modulate this response remain uncharacterized. In this study, we identify Suppressor of Cytokine Signaling (SOCS)-3 as an important regulator of radiation-induced G1 arrest. SOCS3-deficient fibroblasts fail to undergo G1 arrest and accumulate in the G2/M phase of the cell cycle. SOCS3 knockout cells phosphorylate p53 and H2AX normally in response to radiation, but fail to upregulate p21 expression. In addition, STAT3 phosphorylation is elevated in SOCS3-deficient cells compared to WT cells. Normal G1 arrest can be restored in SOCS3 KO cells by retroviral transduction of WT SOCS3 or a dominant-negative mutant of STAT3. Our results suggest a novel function for SOCS3 in the control of genome stability by negatively regulating STAT3-dependent radioresistant DNA synthesis, and promoting p53-dependent p21 expression.     

Selective inhibition of bleomycin-induced G2 cell cycle checkpoint by simaomicin alpha

Human T-cell leukemia-derived Jurkat cells are known to be defective in the G1 checkpoint. DNA-damaging agent bleomycin arrests the cell cycle at G2 phase of Jurkat cells, and microtubule-acting colchicine arrests it at the M phase. Simaomicin alpha, an actinomycete metabolite, itself showed no effect on the cell cycle status of Jurkat cells at least up to 6.0 nM. However, the compound (0.6-6.0 nM) was found to abrogate the bleomycin-induced G2 arrest, yielding a drastic decrease in cells at the G2 phase and increase in cells at the subG1 and G1 phases. On the other hand, the compound did not show any effect on the colchicine-induced M phase arrest in Jurkat cells. Furthermore, the compound showed almost no effect on the cell cycle status of the bleomycin-treated or -untreated normal cell line HUVEC. These data suggested that simaomicin alpha disrupts the cell cycle G2 checkpoint of cancer cells selectively, leading to sensitization of cancer cells to anti-cancer reagents.     

Heme controls the expression of cell cycle regulators and cell growth in HeLa cells

Heme plays a central role in oxygen utilization and in the generation of cellular energy. Here we examined the effect of heme and heme deficiency on cell cycle progression and the expression of key regulators in HeLa cells. We found that inhibition of heme synthesis causes cell cycle arrest and induces the expression of molecular markers associated with senescence and apoptosis, such as increased formation of PML nuclear bodies. Our data show that succinyl acetone-induced heme deficiency increases the protein levels of the tumor suppressor gene product p53 and CDK inhibitor p21, and decreases the protein levels of Cdk4, Cdc2, and cyclin D2. Further, we found that heme deficiency diminishes the activation/phosphorylation of Raf, MEK1/2, and ERK1/2-components of the MAP kinase signaling pathway. Our results show that heme is a versatile molecule that can effectively control cell growth and survival by acting on multiple regulators.     

Oridonin effectively reverses the drug resistance of cisplatin involving induction of cell apoptosis and inhibition of MMP expression in human acute myeloid leukemia cells

Cisplatin is the first generation platinum-based chemotherapy agent. However, the extensive application of cisplatin inevitably causes drug resistance, which is a major obstacle to cancer chemotherapy. Oridonin is a diterpenoid isolated from Rabdosia rubescens with potent anticancer activity. The aim of our study is to investigate the role of oridonin to reverse the cisplatin-resistance in human acute myeloid leukemia (AML) cells. The effect of oridonin on human AML cell proliferation was evaluated by MTT assay, cell migration and invasion were evaluated by transwell migration and invasion assays in cisplatin-resistant human AML cells. Furthermore, cell apoptosis was examined by flow cytometry. The inhibitive effect of oridonin in vivo was determined using xenografted nude mice. In addition, the expressions of MMP2 and MMP9 were detected by Western blot. There was a synergistic antitumor effect between cisplatin and oridonin on cisplatin-resistant human AML cells in vitro and in vivo. In addition, the combination of cisplatin and oridonin synergistically induced cell apoptosis. Furthermore, the combination treatment not only inhibited AML cell migration and invasion, but more significantly, decreased the expressions of MMP2 and MMP9 proteins. Our results suggest that the synergistic effect between both agents is likely to be driven by the inhibition of MMP expression and the resulting increased apoptosis.     

Molecular mechanisms of luteolin-7-O-glucoside-induced growth inhibition on human liver cancer cells: G2/M cell cycle arrest and caspase-independent apoptotic signaling pathways

Luteolin-7-O-glucoside (LUT7G), a flavone subclass of flavonoids, has been found to increase anti-oxidant and anti-inflammatory activity, as well as cytotoxic effects. However, the mechanism of how LUT7G induces apoptosis and regulates cell cycles remains poorly understood. In this study, we examined the effects of LUT7G on the growth inhibition of tumors, cell cycle arrest, induction of ROS generation, and the involved signaling pathway in human hepatocarcinoma HepG2 cells. The proliferation of HepG2 cells was decreased by LUT7G in a dose-dependent manner. The growth inhibition was due primarily to the G2/M phase arrest and ROS generation. Moreover, the phosphorylation of JNK was increased by LUT7G. These results suggest that the anti-proliferative effect of LUT7G on HepG2 is associated with G2/M phase cell cycle arrest by JNK activation. [BMB Reports 2013; 46(12): 611-616]     

Vanadyl bisacetylacetonate induced G1/S cell cycle arrest via high-intensity ERK phosphorylation in HepG2 cells

In recent years the anticancer properties of vanadium compounds have been noticed, but the underlying mechanisms are not well understood. In the present work, we found that vanadyl bisacetylacetonate ([VO(acac)(2)]) blocked cell cycle progression permanently at G1 phase in a dose- and time-dependent manner in HepG2 cells. This was further evidenced by the growth regulatory signals during the G1 stage. After the treatment with [VO(acac)(2)], the level of phosphorylation of retinoblastoma tumor suppressor protein (pRb) and the expressions of cyclin D1, cyclin E and cyclin A were reduced, while the expression of a cyclin-dependent kinase inhibitor p21 was increased dose-dependently. In the meantime, neither O(2)(*-) nor H(2)O(2) level was observed to increase. Interestingly, the levels of phosphorylated extracellular signal-regulated protein kinase (ERK) and Akt were highly activated. After 1-h pretreatment with a lower concentration of MEK inhibitor U0126, the level of phosphorylated pRb was restored, indicating a release of cell cycle arrest. Taken together, we suggested that [VO(acac)(2)]-induced proliferation inhibition was caused by G1/S cell cycle arrest, which resulted from the decreased level of phosphorylated pRb in its active hypophosphorylated form via a highly activated ERK signal in HepG2 cells. The results presented here provided new insight into the development of vanadium compounds as potential anticancer agents.     

Caveolin-2 regulation of the cell cycle in response to insulin in Hirc-B fibroblast cells

The regulatory function of caveolin-2 in cell cycle regulation by insulin was investigated in human insulin receptor-overexpressed rat 1 fibroblast (Hirc-B) cells. Insulin increased induction of the caveolin-2 gene in a time-dependent manner. Direct interaction between ERK and caveolin-2 was confirmed by immunoprecipitation and phosphorylated ERK increased the specific interaction in response to insulin. That insulin induced their nuclear co-localization over time was demonstrated by immunofluorescence microscopy. Insulin increased the S phase in the cell cycle by 6-fold. When recombinant caveolin-1 was transiently expressed, a decrease in the S phase was detected by flow-cytometry. The results indicate that the up-regulation of caveolin-2 in response to insulin activates the downstream signal cascades in the cell cycle, chiefly the increased phosphorylation of ERK, the nuclear translocation of phosphorylated ERK, and the subsequent activation of G0/G1 to S phase transition of the cell cycle. The results also suggest that DNA synthesis and the activation of the cell cycle by insulin are achieved concomitantly with an increase in the interaction between caveolin-2 and phosphorylated ERK, and the nuclear translocation of that complex. Taken together, we conclude that caveolin-2 positively regulates the insulin-induced cell cycle through activation of and direct interaction with ERK in Hirc-B cells.     

Thymidine nucleotide synthesis and catabolism by CHO cells and their changes during the cell cycle

At 0°C, CHO cells efficiently incorporated [³H]thymidine into the nucleotide fraction, but not into DNA. Upon reincubation of asynchronous cultures at 37°C, 15–25% of the radioactivity contained in the cellular nucleotide fraction was released, in the form of thymidine, into the culture medium. At 0°C, however, radioactivity of the nucleotide fraction was retained within the cells. Similarly, dTMP phosphatase (EC 3.1.3.35) in cell extracts was active at 37°C, but not at 0°C, whereas thymidine kinase (EC 2.7.1.21) was active at both temperatures. If synchronous cultures in Gl phase were prelabeled at 0°C and reincubated at 37°C, almost all radioactivity in the nucleotide fraction was released into the medium, whereas in S-phase cultures nearly all radioactivity of the nucleotide fraction was incorporated into DNA. In synchronous S-phase cultures treated with hydroxyurea, radioactivity in the nucleotide fraction was released into the medium at a rate considerably lower than that observed for Gl-phase cells. Rates of endogenous synthesis of thymidine nucleotides were calculated from changes of cellular thymidine nucleotide content, incorporation of thymidine nucleotides into DNA and release of thymidine into the medium during reincubation of prelabeled cultures in thymidine-free medium. The results obtained (see Table III) reveal marked differences between Gl and S phases with respect to the determinants of thymidine nucleotide metabolism.     

G2 arrest of cell cycle ensures a determination process of sensory mother cell formation in Drosophila

 In Drosophila, the sensory mother cells of macrochaetes are chosen from among the mitotically quiescent clusters of cells in wing imaginal discs, where other cells are proliferating. The pattern of cyclin A, one of the G2 cyclins, reveals that mitotically quiescent clusters of cells are arrested in G2. When precocious mitoses are induced during sensory mother cell determination by the ectopic expression of string, a known G2/M transition regulator, the formation of sensory mother cells is disturbed, resulting in the loss of macrochaetes in the adult notum. This suggests that G2 arrest of the cell cycle ensures the proper determination of sensory mother cells. Received: 16 December 1996 / Accepted: 14 March 1997     

Aurora-A kinase-inactive mutants disrupt the interaction with Ajuba and cause defects in mitotic spindle formation and G2/M phase arrest in HeLa cells

Aurora-A is a centrosome-localized serine/threonine kinase that is overexpressed in multiple human cancers. We previously reported an intramolecular inhibitory regulation of Aurora-A between its N-terminal regulatory domain (Nt, amino acids [aa] 1-128) and the C-terminal catalytic domain (Cd, aa 129-403). Here, we demonstrate that although both Aurora-A mutants (AurA-K250G and AurA-D294G/Y295G) lacked interactions between the Nt and Cd, they also failed to interact with Ajuba, an essential activator of Aurora-A, leading to loss of kinase activity. Additionally, overexpression of either of the mutants resulted in centrosome amplification and mitotic spindle formation defects. Both mutants were also able to cause G2/M arrest and apoptosis. These results indicate that both K250 and D294/Y295 are critical for direct interaction between Aurora-A and Ajuba and the function of the Aurora-A complex in cell cycle progression. [BMB Reports 2014; 47(11): 631-636]