93 research outputs found
Control of chromosome stability by the β-TrCP–REST–Mad2 axis
No full textREST/NRSF (repressor-element-1-silencing transcription factor/ neuron-restrictive silencing factor) negatively regulates the tran- scription of genes containing RE1 sites1,2. REST is expressed in non-neuronal cells and stem/progenitor neuronal cells, in which it inhibits the expression of neuron-specific genes. Overexpression of REST is frequently found in human medulloblastomas and neuroblastomas3–7, in which it is thought to maintain the stem character of tumour cells. Neural stem cells forced to express REST and c-Myc fail to differentiate and give rise to tumours in the mouse cerebellum3. Expression of a splice variant of REST that lacks the carboxy terminus has been associated with neuronal tumours and small-cell lung carcinomas8–10, and a frameshift mutant (REST-FS), which is also truncated at the C terminus, has oncogenic properties11. Here we show, by using an unbiased screen, that REST is an interactor of the F-box protein b-TrCP. REST is degraded by means of the ubiquitin ligase SCFb-TrCP dur- ing the G2 phase of the cell cycle to allow transcriptional derepres- sion of Mad2, an essential component of the spindle assembly checkpoint. The expression in cultured cells of a stable REST mutant, which is unable to bind b-TrCP, inhibited Mad2 expres- sion and resulted in a phenotype analogous to that observed in Mad21/2 cells. In particular, we observed defects that were con- sistent with faulty activation of the spindle checkpoint, such as shortened mitosis, premature sister-chromatid separation, chro- mosome bridges and mis-segregation in anaphase, tetraploidy, and faster mitotic slippage in the presence of a spindle inhibitor. An indistinguishable phenotype was observed by expressing the oncogenic REST-FS mutant11, which does not bind b-TrCP. Thus, SCFb-TrCP-dependent degradation of REST during G2 permits the optimal activation of the spindle checkpoint, and consequently it is required for the fidelity of mitosis. The high levels of REST or its truncated variants found in certain human tumours may contri- bute to cellular transformation by promoting genomic instability
N-Methyl-N'-nitro-N-nitrosoguanidine-induced senescence-like growth arrest in colon cancer cells is associated with loss of adenomatous polyposis coli protein, microtubule organization, and telomeric DNA
No full textAbstract Background Cellular senescence is a state in which mammalian cells enter into an irreversible growth arrest and altered biological functions. The senescence response in mammalian cells can be elicited by DNA-damaging agents. In the present study we report that the DNA-damaging agent N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) is able to induce senescence in the HCT-116 colon cancer cell line. Results Cells treated with lower concentrations of MNNG (0–25 microM) for 50 h showed a dose-dependent increase in G2/M phase arrest and apoptosis; however, cells treated with higher concentrations of MNNG (50–100 microM) showed a senescence-like G0/G1 phase arrest which was confirmed by increased expression of β-galactosidase, a senescence induced marker. The G2/M phase arrest and apoptosis were found to be associated with increased levels of p53 protein, but the senescence-like G0/G1 phase arrest was dissociated with p53 protein levels, since the p53 protein levels decreased in senescence-like arrested cells. We further, determined whether the decreased level of p53 was a transcriptional or a translational phenomenon. The results revealed that the decreased level of p53 protein in senescence-like arrested cells was a transcriptional phenomenon since p53 mRNA levels simultaneously decreased after treatment with higher concentrations of MNNG. We also examined the effect of MNNG treatment on other cell cycle-related proteins such as p21, p27, cyclin B1, Cdc2, c-Myc and max. The expression levels of these proteins were increased in cells treated with lower concentrations of MNNG, which supported the G2/M phase arrest. However, cells treated with higher concentrations of MNNG showed decreased levels of these proteins, and hence, may not play a role in cell cycle arrest. We then examined a possible association of the expression of APC protein and telomeric DNA signals with cellular senescence in MNNG-treated cells. We found that protein and mRNA levels of APC were drastically reduced in cells treated with higher concentrations of MNNG. The loss of APC expression might lead to chromosomal instability as well as microtubular disorganization through its dissociation with tubulin. In fact, the protein level of α-tubulin was also drastically decreased in senescence-like arrested cells treated with higher concentrations of MNNG. The levels of telomeric DNA also decreased in cells treated with higher concentrations of MNNG. Conclusions These results suggest that in response to DNA alkylation damage the senescence-like arrest of HCT-116 cells was associated with decreased levels of APC protein, microtubular organization, and telomeric DNA.</p
Fragility in the 14q21q translocation region
No full textAphidicolin (APC)-induced chromosomal breakage was analyzed for women representing three generations of a single family and carrying a Robertsonian translocation rob(14q21q). Fluorescence in situ hybridization (FISH) analysis confirmed the dicentric constitution of the derived chromosome and indicated the absence of beta-satellite signal at the translocation region. Per-individual analysis of metaphases from APC-treated peripheral blood lymphocyte cultures identified significantly nonrandom chromosomal breakage at the translocation region in all three individuals examined. The APC-inducible fragility at the 14q21q translocation region suggests that this rearrangement was the result of chromosomal mutation at fragile site(s) in the progenitor chromosomes, or that this fragility was the result of the fusion of nonfragile progenitor chromosomes
Androgen receptor-negative human prostate cancer cells induce osteogenesis in mice through FGF9-mediated mechanisms
No full textIn prostate cancer, androgen blockade strategies are commonly used to treat osteoblastic bone metastases. However, responses to these therapies are typically brief, and the mechanism underlying androgen-independent progression is not clear. Here, we established what we believe to be the first human androgen receptor-negative prostate cancer xenografts whose cells induced an osteoblastic reaction in bone and in the subcutis of immunodeficient mice. Accordingly, these cells grew in castrated as well as intact male mice. We identified FGF9 as being overexpressed in the xenografts relative to other bone-derived prostate cancer cells and discovered that FGF9 induced osteoblast proliferation and new bone formation in a bone organ assay. Mice treated with FGF9-neutralizing antibody developed smaller bone tumors and reduced bone formation. Finally, we found positive FGF9 immunostaining in prostate cancer cells in 24 of 56 primary tumors derived from human organ-confined prostate cancer and in 25 of 25 bone metastasis cases studied. Collectively, these results suggest that FGF9 contributes to prostate cancer-induced new bone formation and may participate in the osteoblastic progression of prostate cancer in bone. Androgen receptor-null cells may contribute to the castration-resistant osteoblastic progression of prostate cancer cells in bone and provide a preclinical model for studying therapies that target these cells.Fil: Zhi, Gang Li. University Of Texas Md Anderson Cancer Center; Estados UnidosFil: Mathew, Paul. University Of Texas Md Anderson Cancer Center; Estados UnidosFil: Yang, Jun. University Of Texas Md Anderson Cancer Center; Estados UnidosFil: Starbuck, Michael W.. University Of Texas Md Anderson Cancer Center; Estados UnidosFil: Zurita, Amado J.. University Of Texas Md Anderson Cancer Center; Estados UnidosFil: Liu, Jie. University Of Texas Md Anderson Cancer Center; Estados UnidosFil: Sikes, Charles. University Of Texas Md Anderson Cancer Center; Estados UnidosFil: Multani, Asha S.. University Of Texas Md Anderson Cancer Center; Estados UnidosFil: Efstathiou, Eleni. University Of Texas Md Anderson Cancer Center; Estados UnidosFil: Lopez, Adriana. University Of Texas Md Anderson Cancer Center; Estados UnidosFil: Wang, Jing. University Of Texas Md Anderson Cancer Center; Estados UnidosFil: Fanning, Tina V.. University Of Texas Md Anderson Cancer Center; Estados UnidosFil: Prieto, Victor G.. University Of Texas Md Anderson Cancer Center; Estados UnidosFil: Kundra, Vikas. University Of Texas Md Anderson Cancer Center; Estados UnidosFil: Vazquez, Elba Susana. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales; ArgentinaFil: Troncoso, Patricia. University Of Texas Md Anderson Cancer Center; Estados UnidosFil: Raymond, Austin K.. University Of Texas Md Anderson Cancer Center; Estados UnidosFil: Logothetis, Christopher J.. University Of Texas Md Anderson Cancer Center; Estados UnidosFil: Lin, Sue-Hwa. University Of Texas Md Anderson Cancer Center; Estados UnidosFil: Maity, Sankar. University Of Texas Md Anderson Cancer Center; Estados UnidosFil: Navone, Nora M.. University Of Texas Md Anderson Cancer Center; Estados Unido
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