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1.
Glioblastoma (GBM) remains one of the most challenging solid cancers to treat due to its highly proliferative, angiogenic and invasive nature. The small molecule CDK inhibitor, flavopiridol, has demonstrated antitumor activity in human xenograft models and is currently in clinical trials showing efficacy in patients with advanced disease. We have developed an experimental animal model using the murine glioma GL261 cells as a novel in vivo system to screen potential therapeutic agents for GBM. Results of in vitro testing demonstrate that flavopiridol has several relevant clinical characteristics such as its ability to: 1. inhibit cell growth; 2. inhibit cell migration; 3. decrease expression of cyclin D1, CDK4 and p21; 4. induce apoptosis in cells with high levels of p27 expression; and 5. decrease the expression of the anti-apoptotic protein Bcl-2. The mechanism by which flavopiridol induces apoptosis is mitochondrial-mediated. We demonstrate by electron microscopy and immunohistochemistry that drug treatment induces mitochondrial damage that was accompanied by the release of cytochrome c into the cytosol together with the translocation of apoptosis inducing factor (AIF) into the nucleus. This finding in murine glioma cells differs from the mechanism of flavopiridolinduced cell death reported by us for human glioma cells (Alonso et al., Mol Cancer Ther 2003; 2:139) where drug treatment induced a caspase- and cytochrome c-independent pathway in the absence of detectable damage to mitochondria. In apoptotic human glioma cells only translocation of AIF into the nucleus occurred. Thus, the same drug kills different types of glioma cells by different mitochondrial-dependent pathways.  相似文献   

2.
We have examined the effects of the CDK1 inhibitor CGP74514A on cell cycle- and apoptosis-related events in human leukemia cells. An 18-hr exposure to 5 mM CGP74514A induced mitochondrial damage (i.e., loss of Dym) and apoptosis in multiple human leukemia cell lines (e.g., U937, HL-60, KG-1, CCRF-CEM, Raji, and THP; range 30-95%). In U937 cells, CGP74514A- induced apoptosis (5 mM) became apparent within 4 hr and approached 100% by 24 hr. The pan- caspase inhibitor Boc-fmk and the caspase-8 inhibitor IETD-fmk opposed CGP74514A-induced caspase-9 activation and PARP degradation, but not cytochrome c or Smac/DIABLO release. CGP74514A-mediated apoptosis was substantially blocked by ectopic expression of full-length Bcl- 2, a loop-deleted mutant Bcl-2, and Bcl-xL. CGP74514A treatment (5 mM; 18 hr) resulted in increased p21CIP1 expression, p27KIP1 degradation, diminished E2F1 expression, and dephosphorylation of p34cdc2. It also induced early (i.e., within 2 hr) inhibition of CDK1 activity and dephosphorylation of pRb, followed by pRb degradation, but did not block pRb phosphorylation at CDK2- and CDK4- specific sites. These findings indicate that the selective CDK1 inhibitor, CGP74514A, induces complex changes in cell cycle-related proteins in human leukemia cells accompanied by extensive mitochondrial damage, caspase activation, and apoptosis.

Key Words:

Leukemia, CDK1 Inhibitor, Apoptosis, CGP74514A  相似文献   

3.
We have recently shown that curcumin induces apoptosis in prostate cancer cells through Bax translocation to mitochondria and caspase activation, and enhances the therapeutic potential of TRAIL. However, the molecular mechanisms by which it causes growth arrest are not well-understood. We studied the molecular mechanism of curcumin-induced cell cycle arrest in prostate cancer androgen-sensitive LNCaP and androgen-insensitive PC-3 cells. Treatment of both cell lines with curcumin resulted in cell cycle arrest at G1/S phase and that this cell cycle arrest is followed by the induction of apoptosis. Curcumin induced the expression of cyclin-dependent kinase (CDK) inhibitors p16/INK4a, p21/WAF1/CIP1 and p27/KIP1, and inhibited the expression of cyclin E and cyclin D1, and hyperphosphorylation of retinoblastoma (Rb) protein. Lactacystin, an inhibitor of 26 proteasome, blocks curcumin-induced down-regulation of cyclin D1 and cyclin E proteins, suggesting their regulation at level of posttranslation. The suppression of cyclin D1 and cyclin E by curcumin may inhibit CDK-mediated phosphorylation of pRb protein. The inhibition of p21/WAF1/CIP1 by siRNA blocks curcumin-induced apoptosis, thus establishing a link between cell cycle and apoptosis. These effects of curcumin result in the proliferation arrest and disruption of cell cycle control leading to apoptosis. Our study suggests that curcumin can be developed as a chemopreventive agent for human prostate cancer.  相似文献   

4.
The mechanism of action of many chemotherapeutic agents targets the cell cycle. Recently, we demonstrated cytotoxic and other anti-tumor effects of flavopiridol, the first synthetic cyclin dependent kinase (CDK) inhibitor to enter clinical trials, on the murine GL261 glioma cell line in vitro (Newcomb et al., Cell Cycle 2003; 2:243). Given that flavopiridol has demonstrated anti-tumor activity in several human xenograft models, we wanted to evaluate it for anti-glioma activity in vivo in our established subcutaneous and intracranial GL261 experimental tumor models. In particular, the intracranial animal model recapitulates many of the histopathological and biological features of human high-grade glioma including both necrosis with pseudopalisading and invasion of the brain adjacent to tumor. Here we tested the activity of flavopiridol against tumors formed by GL261 cells, first as subcutaneous implants, and then in the intracranial model. We demonstrate efficacy of flavopiridol as a single modality treatment in delaying tumor growth in both animal models. We hypothesize that flavopiridol treatment induced tumor growth delay by two possible mechanisms involving growth arrest combined with recruitment of tumor cells to S-phase. Based on our findings, flavopiridol should be considered as a treatment approach for patients with high-grade glioma.  相似文献   

5.
The mechanism of action of many chemotherapeutic agents targets the cell cycle. Recently, we demonstrated cytotoxic and other anti-tumor effects of flavopiridol, the first synthetic cyclin dependent kinase (CDK) inhibitor to enter clinical trials, on the murine GL261 glioma cell line in vitro (Newcomb et al., Cell Cycle 2003; 2:243). Given that flavopiridol has demonstrated anti-tumor activity in several human xenograft models, we wanted to evaluate it for anti-glioma activity in vivo in our established subcutaneous and intracranial GL261 experimental tumor models. In particular, the intracranial animal model recapitulates many of the histopathological and biological features of human high-grade glioma including both necrosis with pseudopalisading and invasion of the brain adjacent to tumor. Here we tested the activity of flavopiridol against tumors formed by GL261 cells, first as subcutaneous implants, and then in the intracranial model. We demonstrate efficacy of flavopiridol as a single modality treatment in delaying tumor growth in both animal models. We hypothesize that flavopiridol treatment induced tumor growth delay by two possible mechanisms involving growth arrest combined with recruitment of tumor cells to S-phase. Based on our findings, flavopiridol should be considered as a treatment approach for patients with high-grade glioma.  相似文献   

6.
Isoegomaketone (IK) is an essential oil component of Perilla frutescens (L.), but the mechanism by which IK induces apoptosis has never been studied. The purpose of this study was to elucidate the IK-induced apoptotic pathway in DLD1 human colon cancer cells. We observed that IK treatment over 24 h significantly inhibited cell viability in a dose-dependent manner. We also found that IK triggered cleavage of PARP. Moreover, IK treatment resulted in cleavage of caspase-8, -9, and -3 in a dose- and time-dependent manner. IK treatment also resulted in cleavage of Bid and translocation of Bax, and triggered the release of cytochrome c from the mitochondria to the cytoplasm. Furthermore, it resulted in the translocation of apoptosis inducing factor (AIF), a caspase-independent mitochondrial apoptosis factor, from the mitochondria into the nucleus. Overall, these results suggest that IK induces apoptosis through caspase-dependent and capase-independent pathways in DLD1 cells.  相似文献   

7.
Maduramicin, a polyether ionophore antibiotic derived from the bacterium Actinomadura yumaensis, is currently used as a feed additive against coccidiosis in poultry worldwide. It has been clinically observed that maduramicin can cause skeletal muscle and heart cell damage, resulting in skeletal muscle degeneration, heart failure, and even death in animals and humans, if improperly used. However, the mechanism of its toxic action in myoblasts is not well understood. Using mouse myoblasts (C2C12) and human rhabdomyosarcoma (RD and Rh30) cells as an experimental model for myoblasts, here we found that maduramicin inhibited cell proliferation and induced cell death in a concentration-dependent manner. Further studies revealed that maduramicin induced accumulation of the cells at G0/G1 phase of the cell cycle, and induced apoptosis in the cells. Concurrently, maduramicin downregulated protein expression of cyclin D1, cyclin-dependent kinases (CDK4 and CDK6), and CDC25A, and upregulated expression of the CDK inhibitors (p21Cip1 and p27Kip1), resulting in decreased phosphorylation of Rb. Maduramicin also induced expression of BAK, BAD, DR4, TRADD and TRAIL, leading to activation of caspases 8, 9 and 3 as well as cleavage of poly ADP ribose polymerase (PARP). Taken together, our results suggest that maduramicin executes its toxicity in myoblasts at least by inhibiting cell proliferation and inducing apoptotic cell death.  相似文献   

8.
Fusarochromanone (FC101), a mycotoxin produced by the fungus Fusarium equiseti, is frequently observed in the contaminated grains and feedstuffs, which is toxic to animals and humans. However, the underlying molecular mechanism remains to be defined. In this study, we found that FC101 inhibited cell proliferation and induced cell death in COS7 and HEK293 cells in a concentration-dependent manner. Flow cytometric analysis showed that FC101 induced G1 cell cycle arrest and apoptosis in the cells. Concurrently, FC101 downregulated protein expression of cyclin D1, cyclin-dependent kinases (CDK4 and CDK6), and Cdc25A, and upregulated expression of the CDK inhibitors (p21Cip1 and p27Kip1), resulting in hypophosphorylation of Rb. FC101 also inhibited protein expression of Bcl-2, Bcl-xL, Mcl-1 and survivin, and induced expression of BAD, leading to activation of caspase 3 and cleavage of PARP, indicating caspase-dependent apoptosis. However, Z-VAD-FMK, a pan-caspase inhibitor, only partially prevented FC101-induced cell death, implying that FC101 may induce cell death through both caspase-dependent and -independent mechanisms. Our results support the notion that FC101 executes its toxicity at least by inhibiting cell proliferation and inducing cell death.  相似文献   

9.
Fu YR  Yi ZJ  Yan YR  Qiu ZY 《Mitochondrion》2006,6(4):211-217
The camptothecin (CPT) derivative hydroxycamptothecin (HCPT) containing 10-hydroxy represents one of the most potent topoisomerase I inhibitors described. This anticancer agent, currently undergoing clinical trials on gastric tumours, has been shown more active and less toxic than conventional camptothecins. To shed light on the mechanism of action of HCPT at the cellular level, we examined cell growth, apoptosis, changes of mitochondrial membrane potential, cytochrome c and AIF translocation in cancer cells by exposing these cells to HCPT for indicated time. The effect of HCPT on cell proliferation was measured by MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromid) assay and apoptosis was measured using flow cytometry, fluorescence microscopy and electron microscopy. Changes of mitochondrial membrane potential were monitored by fluorescence microscope. Western blot analysis was used to evaluate the release of mitochondrial cytochrome c and AIF; On the other hand, translocation of cytochrome c and AIF from mitochondria to cytosol during apoptosis were confirmed by confocal microscopy. HCPT could noticeably inhibit the proliferation of SMMC-7721cells and the IC(50) dose was about 0.22muM; SMMC-7721 cells treated with HCPT showed typical characteristics of apoptosis rather than necrotic including phosphatidylserine (PS) exposed from the inner to the outer leaflet of the plasma membrane, abnormal cell morphology, chromatin condensation and nuclear fragmentation; On the other hand, during process of cell apoptosis, mitochondrial transmembrane potential was reduced; Compared with the control group, the mRNA and protein expression of cytochrome c and AIF in treated and untreated SMMC-7721 cells were not significantly changed (not shown). However, when cells were treated with HCPT, the massive translocation of cytochrome c and AIF to the nucleus was evident. Our results indicate that HCPT can inhibit proliferation and induce apoptosis of human hepatoma SMMC-7721 cells. Mitochondrial pathway of apoptosis, especially for cytochrome c and AIF translocation, may play an important role in apoptosis induced by HCPT.  相似文献   

10.
11.
Cordycepin, an adenosine analog derived from Cordyceps militaris has been shown to exert anti-tumor activity in many ways. However, the mechanisms by which cordycepin contributes to the anti-tumor still obscure. Here our present work showed that cordycepin inhibits cell growth in NB-4 and U937 cells by inducing apoptosis. Further study showed that cordycepin increases the expression of p53 which promotes the release of cytochrome c from mitochondria to the cytosol. The released cytochrome c can then activate caspase-9 and trigger intrinsic apoptosis. Cordycepin also blocks MAPK pathway by inhibiting the phosphorylation of ERK1/2, and thus sensitizes the apoptosis. In addition, our results showed that cordycepin inhibits the expression of cyclin A2, cyclin E, and CDK2, which leads to the accumulation of cells in S-phase. Moreover, our study showed that cordycepin induces DNA damage and causes degradation of Cdc25A, suggesting that cordycepin-induced S-phase arrest involves activation of Chk2-Cdc25A pathway. In conclusion, cordycepin-induced DNA damage initiates cell cycle arrest and apoptosis which leads to the growth inhibition of NB-4 and U937 cells.  相似文献   

12.

Objective

This research aimed to investigate whether glutamate induced spiral ganglion neurons (SGNs) apoptosis through apoptosis inducing factor (AIF) pathway. And verify whether PD150606, a calpain inhibitor could prevent apoptosis by inhibiting cleaving and releasing AIF in mitochondrion.

Methods

SGNs of postnatal days 0-3 were harvested and cultured in dishes. 20 mM Glu, the caspase inhibitor Z-VAD-FMK and calpain inhibitor PD150606 were added into cultured dishes separately. We used optical microscope and immunofluoresence staining to observe cell morphology and AIF distribution, RT-PCR and Westernblot to analyse AIF and calpain expression in SGNs. TUNEL assay was used to test cell apoptosis.

Results

Cell morphology and nuclear translocation of AIF were altered in SGNs by 20 mM Glu treated in vitro. The axon of SGN shortened, more apoptosis SGN were observed and the expression of AIF and calpain were up-regulated in Glu-treated group than the normal one (P<0.05). The same experiments were conducted in 20 mM+PD150606 treated group and 20 mM+Z-VAD-FMK group. Obviously AIF were located from cytoplasm to the nuclear and the expressions of AIF and calpain were down-regulated by PD150606 (P<0.05). Positive cells in TUNEL staining decreased after PD150606 treating. However, Z-VAD-FMK had no influence on AIF, calpain expression or cell apoptosis.

Conclusion

The AIF-related apoptosis pathway is involved in the process of Glu-induced SGN injury. Furthermore, the inhibition of calpain can prevent AIF from releasing the nuclear or inducing SGN apoptosis.  相似文献   

13.
Most of the chemotherapy treatments for bladder cancer aim to kill the cancer cells, but a high recurrence rate after medical treatments is still occurred. Bufalin from the skin and parotid venom glands of toad has been shown to induce apoptotic cell death in many types of cancer cell lines. However, there is no report addressing that bufalin induced cell death in human bladder cancer cells. The purpose of this study was investigated the mechanisms of bufalin-induced apoptosis in a human bladder cancer cell line (T24). We demonstrated the effects of bufalin on the cell growth and apoptosis in T24 cells by using DAPI/TUNEL double staining, a PI exclusion and flow cytometric analysis. The effects of bufalin on the production of reactive oxygen species (ROS), the level of mitochondrial membrane potential (ΔΨ(m)), and DNA content including sub-G1 (apoptosis) in T24 cells were also determined by flow cytometry. Western blot analysis was used to examine the expression of G(0)/G(1) phase-regulated and apoptosis-associated protein levels in bufalin-treated T24 cells. The results indicated that bufalin significantly decreased the percentage of viability, induced the G(0)/G(1) phase arrest and triggered apoptosis in T24 cells. The down-regulation of the protein levels for cyclin D, CDK4, cyclin E, CDK2, phospho-Rb, phospho-AKT and Bcl-2 with the simultaneous up-regulation of the cytochrome c, Apaf-1, AIF, caspase-3, -7 and -9 and Bax protein expressions and caspase activities were observed in T24 cells after bufalin treatment. Based on our results, bufalin induces apoptotic cell death in T24 cells through suppressing AKT activity and anti-apoptotic Bcl-2 protein as well as inducing pro-apoptotic Bax protein. The levels of caspase-3, -7 and -9 are also mediated apoptosis in bufalin-treated T24 cells. Therefore, bufalin might be used as a therapeutic agent for the treatment of human bladder cancer in the future.  相似文献   

14.
We have previously found that bone morphogenetic protein-2 (BMP-2), a member of the transforming growth factor-beta family, induces cell-cycle arrest in the G1 phase and apoptotic cell death of HS-72 mouse hybridoma cells. In this study, we show that BMP-2 did not alter expression of cyclin D, cyclin E, cyclin-dependent kinase 2 (CDK2), CDK4, p27KIP1, p16INK4a, or p15INK4b, but enhanced expression of p21(CIP1/WAF1). Accumulation of p21(CIP1/WAF1) resulted in increased binding of p21(CIP1/WAF1) to CDK4 and concomitantly caused a profound decrease in the in vitro retinoblastoma protein (Rb) kinase activity of CDK4. Furthermore, the ectopic expression of human papilloma virus type-16 E7, an inhibitor of p21(CIP1/WAF1) and Rb, reverted G1 arrest induced by BMP-2. Expression of E6/E7, without increasing the p53 level, blocked inhibition of Rb phosphorylation and G1 arrest, but did not attenuate cell death in BMP-treated HS-72 cells. Taken together, these results suggest that inhibition of Rb phosphorylation by p21(CIP1/WAF1) is responsible for BMP-2-mediated G1 arrest and that BMP-2-induction of apoptosis might be independent of Rb hypophosphorylation.  相似文献   

15.
Flavokawain C (FKC) is a naturally occurring chalcone which can be found in Kava (Piper methysticum Forst) root. The present study evaluated the effect of FKC on the growth of various human cancer cell lines and the underlying associated mechanisms. FKC showed higher cytotoxic activity against HCT 116 cells in a time- and dose-dependent manner in comparison to other cell lines (MCF-7, HT-29, A549 and CaSki), with minimal toxicity on normal human colon cells. The apoptosis-inducing capability of FKC on HCT 116 cells was evidenced by cell shrinkage, chromatin condensation, DNA fragmentation and increased phosphatidylserine externalization. FKC was found to disrupt mitochondrial membrane potential, resulting in the release of Smac/DIABLO, AIF and cytochrome c into the cytoplasm. Our results also revealed that FKC induced intrinsic and extrinsic apoptosis via upregulation of the levels of pro-apoptotic proteins (Bak) and death receptors (DR5), while downregulation of the levels of anti-apoptotic proteins (XIAP, cIAP-1, c-FlipL, Bcl-xL and survivin), resulting in the activation of caspase-3, -8 and -9 and cleavage of poly(ADP-ribose) polymerase (PARP). FKC was also found to cause endoplasmic reticulum (ER) stress, as suggested by the elevation of GADD153 protein after FKC treatment. After the cells were exposed to FKC (60μM) over 18hrs, there was a substantial increase in the phosphorylation of ERK 1/2. The expression of phosphorylated Akt was also reduced. FKC also caused cell cycle arrest in the S phase in HCT 116 cells in a time- and dose-dependent manner and with accumulation of cells in the sub-G1 phase. This was accompanied by the downregulation of cyclin-dependent kinases (CDK2 and CDK4), consistent with the upregulation of CDK inhibitors (p21Cip1 and p27Kip1), and hypophosphorylation of Rb.  相似文献   

16.
Butylene fipronil (BFPN) is a phenylpyrazole insecticide, acting at the γ‐aminobutyric acid (GABA) receptor. Here, we show that BFPN inducedcytotoxicity in PC12 murinenervous cells, which lacks GABA receptor. Treatment with BFPN for 48 hours significantly enhanced G0/G1 arrest and induced apoptosis. BFPN decreased the expression of cyclin‐dependent kinase (CDK4 and CDK6) and increased P16 and cyclin D1. Simultaneously, Bcl‐2 protein was declined while Bax and cytochrome c were significantly enhanced in BFPN‐treated groups. The apoptotic enzymes caspase‐8, ‐9, and ‐3 were also activated by BFPN. Furthermore, treatment with BFPN significantly stimulated reactive oxygen species (ROS) generation, and pretreatment with antioxidant diphenyleneiodonium, substantially reduced cell death. Overall, these results suggest that BFPN is effective to induce G0/G1‐phase arrest and apoptosis in PC12 murine nervous cell. Stimulating ROS generation and activation of P16‐CDK4/6‐cyclin D1 and mitochondrial apoptotic pathway may participate in the cytotoxicity of BFPN.  相似文献   

17.
sp2-Iminosugar-type castanospermine analogues have been shown to exhibit anti-tumor activity. However, their effects on cell proliferation and apoptosis and the molecular mechanism at play are not fully understood. Here, we investigated the effect of two representatives, namely the pseudo-S- and C-octyl glycoside 2-oxa-3-oxocastanospermine derivatives SO-OCS and CO-OCS, on MCF-7 and MDA-MB-231 breast cancer and MCF-10A mammary normal cell lines. We found that SO-OCS and CO-OCS inhibited breast cancer cell viability in a concentration- and time-dependent manner. This effect is specific to breast cancer cells as both molecules had no impact on normal MCF-10A cell proliferation. Both drugs induced a cell cycle arrest. CO-OCS arrested cell cycle at G1 and G2/M in MCF-7 and MDA-MB-231cells respectively. In MCF-7 cells, the G1 arrest is associated with a reduction of CDK4 (cyclin-dependent kinase 4), cyclin D1 and cyclin E expression, pRb phosphorylation, and an overexpression of p21Waf1/Cip1. In MDA-MB-231 cells, CO-OCS reduced CDK1 but not cyclin B1 expression. SO-OCS accumulated cells in G2/M in both cell lines and this blockade was accompanied by a decrease of CDK1, but not cyclin B1 expression. Furthermore, both drugs induced apoptosis as demonstrated by the increased percentage of annexin V positive cells and Bax/Bcl-2 ratio. Interestingly, in normal MCF-10A cells the two drugs failed to modify cell proliferation, cell cycle progression, cyclins, or CDKs expression. These results demonstrate that the effect of CO-OCS and SO-OCS is triggered by both cell cycle arrest and apoptosis, suggesting that these castanospermine analogues may constitute potential anti-cancer agents against breast cancer.  相似文献   

18.
Prognosis of patients with glioblastoma (GBM) remains very poor, thus making the development of new drugs urgent. Resveratrol (Rsv) is a natural compound that has several beneficial effects such as neuroprotection and cytotoxicity for several GBM cell lines. Here we evaluated the mechanism of action of Rsv on human GBM cell lines, focusing on the role of autophagy and its crosstalk with apoptosis and cell cycle control. We further evaluated the role of autophagy and the effect of Rsv on GBM Cancer Stem Cells (gCSCs), involved in GBM resistance and recurrence. Glioma cells treated with Rsv was tested for autophagy, apoptosis, necrosis, cell cycle and phosphorylation or expression levels of key players of these processes. Rsv induced the formation of autophagosomes in three human GBM cell lines, accompanied by an upregulation of autophagy proteins Atg5, beclin-1 and LC3-II. Inhibition of Rsv-induced autophagy triggered apoptosis, with an increase in Bax and cleavage of caspase-3. While inhibition of apoptosis or autophagy alone did not revert Rsv-induced toxicity, inhibition of both processes blocked this toxicity. Rsv also induced a S-G2/M phase arrest, accompanied by an increase on levels of pCdc2(Y15), cyclin A, E and B, and pRb (S807/811) and a decrease of cyclin D1. Interestingly, this arrest was dependent on the induction of autophagy, since inhibition of Rsv-induced autophagy abolishes cell cycle arrest and returns the phosphorylation of Cdc2(Y15) and Rb(S807/811), and levels of cyclin A, and B to control levels. Finally, inhibition of autophagy or treatment with Rsv decreased the sphere formation and the percentage of CD133 and OCT4-positive cells, markers of gCSCs. In conclusion, the crosstalk among autophagy, cell cycle and apoptosis, together with the biology of gCSCs, has to be considered in tailoring pharmacological interventions aimed to reduce glioma growth using compounds with multiple targets such as Rsv.  相似文献   

19.
Mechanism of taxol-induced apoptosis in human SKOV3 ovarian carcinoma cells   总被引:4,自引:0,他引:4  
Taxol is extensively used clinically for chemotherapy of patients with ovarian, breast, and lung cancer. Although taxol induces apoptosis of cancer cells, its exact mechanism of action is not yet known. To determine the mechanism of action of taxol in ovarian cancer, we tested the effects of the drug, on the human ovarian carcinoma cell line, SKOV3. We observed that taxol-induced apoptosis of these cells by phosphatidylserine (PS) externalization and DNA fragmentation. While treatment of cells with taxol resulted in bcl-2 phosphorylation and mitochondrial depolarization, cytochrome c was not released and pro-caspase-3 was not activated. Treatment of SKOV3 cells with taxol, however, resulted in the translocation of AIF from the mitochondria to the nucleus via the cytosol. Taken together, these findings suggest that in SKOV3 cells, taxol induces caspase-independent AIF-dependent apoptosis.  相似文献   

20.
Alphavirus, a genus of arthropod-borne togavirus, is well-known for its pro-apoptotic capability. However, the underlying mechanism remains to be further clarified. Here, we have identified that M1, an alphavirus isolated in 1960s, targeted C6 malignant glioma cells for apoptosis. Flow cytometry analysis showed that more cells enter S-phase post M1 infection, and subsequently undergo a classic apoptosis. To elucidate the mechanism of S-phase arrest and its relationship to apoptosis, we tested the expression of several critical cell cycle regulatory proteins and found elevated phosphorylation of cyclin-dependent kinase 2 (CDK2), decreased expression of cyclin A and proliferating cell nuclear antigen (PCNA). Notably, the protein level of p21WAF1/CIP1 was downregulated earliest and most effectively among all tested changes of cell cycle regulators, though its mRNA level was strongly upregulated. To evaluate the role of p21WAF1/CIP1 in S-phase accumulation and subsequent apoptosis, we confirmed that exogenous p21WAF1/CIP1 overexpression or treatment with roscovitine (a selective chemical inhibitor of CDK2) efficiently protected against apoptosis with a reduced S-phase accumulation Thus, it is indicated that the downregulation of p21WAF1/CIP1 mediated C6 apoptosis via overactivation of CDK2. In addition, confocal microscopy showed that p21WAF1/CIP1 totally translocated to nucleolus during M1-induced C6 apoptosis. Altogether, downregulation and nucleolar translocation of the p21WAF1/CIP1 protein played an active role in M1-induced C6 apoptosis.  相似文献   

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