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ABSTRACT: BACKGROUND: Ascites may affect the progression of ovarian cancer (OC). In particular, soluble factors present in OC ascites can create a protective environment for tumor cells that promote de novo resistance to drug- and death receptor-induced apoptosis. However, the underlying molecular mechanisms responsible for ascites-induced drug resistance are not well characterized. METHODS: Using human OC cell lines and tissues microarrays of human OC biopsies, we assessed the mechanism by which OC ascites increase Mcl-1 expression using Western blots, chemical inhibitors of ERK and small-inhibitory RNA treatments. RESULTS: In the present study, we found that both Mcl-1 mRNA and protein levels were upregulated within 2 h upon treatment of OC cells with ascites obtained from women with advanced OC. In contrast, the expression of other Bcl-2 family antiapoptotic members such as Bcl-2 and Bcl-XL was not affected by ascites. An increase of Mcl-1 expression was consistently observed across different ascites from women with advanced serous OC. The knockdown of Mcl-1 significantly blocked ascites-induced Mcl-1 upregulation and ascites-mediated inhibition of TRAIL-induced apoptosis. Ascites induced a rapid phosphorylation of ERK1/2 and Elk-1 transcription factor. Furthermore, we found that ERK1/2 inhibition or Elk-1 knockdown was sufficient to block ascites-induced Mcl-1 expression. In high grade serous OC, we found a positive correlation between phosphorylated ERK1/2 and Mcl-1 expression. CONCLUSIONS: These results indicate that ascites-induced ERK1/2/Elk-1 signaling is critical for Mcl-1 expression and for the ascites-mediated attenuation of TRAIL-induced apoptosis. The ERK1/2/Elk-1/Mcl-1 pathway represents a novel mechanism by which ascites induce de novo TRAIL resistance in OC cells.
Molecular Cancer 11/2012; 11(1):84. · 3.99 Impact Factor
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ABSTRACT: BACKGROUND: Resistance to apoptosis is a major problem in ovarian cancer and correlates with poor prognosis. Osteoprotegerin (OPG) is a secreted factor in malignant ascites and acts as a decoy receptor for receptor activator of NF-kappaB ligand (RANKL) and tumor necrosis factor-related apoptosis-inducing ligand (TRAIL). TRAIL promotes apoptosis in ovarian cancer cells. Ovarian cancer ascites attenuate TRAIL-induced apoptosis raising the possibility that OPG contained in ascites may abrogate the anti-tumor activity of TRAIL. METHODS: Determination of OPG levels in ascites was measured by ELISA. Effect of OPG on TRAILinduced cell death was determined by XTT and colony forming assays in ovarian cancer cell lines and primary tumor cells. Apoptosis was assessed by ELISA. RESULTS: We found that recombinant OPG and malignant ascites attenuates TRAIL-induced cell death and apoptosis in a dose-dependent manner in ovarian cancer cell lines and primary ovarian tumor cells. OPG is present at high levels in the ascites of patients with ovarian cancer. We found a positive correlation between the levels of OPG in ascites and the ability of the ascites to attenuate TRAIL-induced cell death. The anti-apoptotic effect of ascites was not reversed by co-incubation with an OPG blocking antibody. CONCLUSIONS: OPG and malignant ascites protect ovarian cancer cells from TRAIL-induced apoptosis. Although malignant ascites contain high levels of OPG, OPG is not a critical component that contributes to ascites-mediated attenuation of TRAIL-induced apoptosis.
Journal of Ovarian Research 11/2012; 5(1):34. · 2.57 Impact Factor
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ABSTRACT: Ovarian cancer (OC) is the leading cause of death from gynecological malignancies. Although most patients respond to the initial therapy when presenting with advanced disease, only 10-15% maintain a complete response following first-line therapy. Recurrence defines incurable disease in most cases. Despite improvements with conventional chemotherapy combinations, the overall cure rate remained mostly stable over the years. Increased long-term survival in OC patients will only be achieved through a comprehensive understanding of the basic mechanisms of tumor cell resistance. Such knowledge will translate into the development of new targeted strategies. In addition, because OC is considered to be a heterogeneous group of diseases with distinct gene expression profiles, it is likely that different approaches to treatment for distinct sub-types will be required to optimize response. One of the new promising anti-cancer therapies is the tumor necrosis factor-related apoptosis-inducing ligand (TRAIL). TRAIL has the ability to selectively induce apoptosis in tumor cells with little toxicity to normal cells. Death receptor ligands such as TRAIL rely on the activation of the apoptotic signaling pathway to destroy tumor cells. TRAIL induces the formation of a pro-apoptotic death-inducing signaling complex (DISC) via its death receptors, TRAIL receptor 1 (TRAIL R1) and TRAIL receptor 2 (TRAIL R2). The formation of the DISC activates caspase-8 which requires further signal amplification through the mitochondrial pathway for an efficient activation of effector caspases in OC cells. The initial enthusiasm for TRAIL has been hampered by accumulating data demonstrating TRAIL resistance in various tumor types including OC cells. There is, therefore, a need to identify markers of TRAIL resistance, which could represent new hits for targeted therapy that will enhance TRAIL efficacy. In addition, the identification of patients that are more likely to respond to TRAIL therapy would be highly desirable. In this review, we discuss the different molecular and cellular mechanisms leading to TRAIL resistance in OC. In particular, we address the mechanisms involved in intrinsic, acquired and environment-mediated TRAIL resistance, and their potential implication in the clinical outcome.
American journal of cancer research. 01/2012; 2(1):75-92.
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ABSTRACT: The behavior of tumor cells is influenced by the composition of the surrounding tumor environment. The importance of ascites in ovarian cancer (OC) progression is being increasingly recognized. The characterization of soluble factors in ascites is essential to understand how this environment affects OC progression. The development of cytokine arrays now allows simultaneous measurement of multiple cytokines per ascites using a single array.
We applied a multiplex cytokine array technology that simultaneously measures the level of 120 cytokines in ascites from 10 OC patients. The ascites concentration of a subset (n = 5) of cytokines that was elevated based on the multiplex array was validated by commercially available ELISA. The ascites level of these 5 cytokines was further evaluated by ELISA in a cohort of 38 patients. Kaplan-Meier analysis was used to assess the association of cytokine expression with progression-free survival (PFS) in this cohort.
We observed a wide variability of expression between different cytokines and levels of specific cytokines also varied in the 10 malignant ascites tested. Fifty-three (44%) cytokines were not detected in any of the 10 ascites. The level of several factors including, among others, angiogenin, angiopoietin-2, GRO, ICAM-1, IL-6, IL-6R, IL-8, IL-10, leptin, MCP-1, MIF NAP-2, osteprotegerin (OPG), RANTES, TIMP-2 and UPAR were elevated in most malignant ascites. Higher levels of OPG, IL-10 and leptin in OC ascites were associated with shorter PFS. IL-10 was shown to promote the anti-apoptotic activity of malignant ascites whereas OPG did not.
Our data demonstrated that there is a complex network of cytokine expression in OC ascites. Characterization of cytokine profiles in malignant ascites may provide information from which to prioritize key functional cytokines and understand the mechanism by which they alter tumor cells behavior. A better understanding of the cytokine network is essential to determine the role of ascites in OC progression.
American journal of cancer research. 01/2012; 2(5):566-80.
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ABSTRACT: MUC16 (CA125) protein is a high molecular weight mucin overexpressed in the majority of epithelial ovarian cancers (EOC) but not in the epithelium of normal ovaries suggesting that it might play a role in EOC pathogenesis. Here, we explored the phenotypic consequences of MUC16 knockdown and expression of its C-terminal domain with the aim of establishing a role for MUC16 in tumorigenesis.
MUC16 was down-regulated by stably expressing an anti-MUC16 endoplasmic reticulum-targeted single-chain antibody which prevented MUC16 cell surface localization in NIH:OVCAR3 cells. In addition, we generated epitope tagged, N-terminal region-deleted MUC16 constructs with (MUC16TMU) and without (MUC16CTD) cytoplasmic tail deletions and stably expressed them in SKOV3 cells.
Although MUC16 knockdown did not affect the cell growth rate, knockdown cells reached a stationary growth phase after 4 days whereas control cells continued to grow for up to 7 days. Colony formation assays in soft agar demonstrated that MUC16 knockdown cells had >8-fold reduction in their ability to form colonies. Importantly, MUC16 knockdown completely prevents the formation of subcutaneous tumors in nude mice. Conversely, we show that ectopic expression of the MUC16CTD enhances SKOV3 tumor cell growth, colony formation in soft agar and enhances tumor growth and metastases in SCID mice. In addition, MUC16CTD expression increases cell motility, invasiveness, and metastatic property. Deletion of the cytoplasmic tail from the MUC16CTD completely abolished its ability to enhance tumor cell growth, cell motility and invasiveness. Furthermore, the increased invasive properties of MUC16CTD-expressing cells correlated with decreased expression of E-cadherin and increased expression of N-cadherin and vimentin.
These findings provide the first evidence for a critical role of MUC16 in tumor cell growth, tumorigenesis and metastases.
Gynecologic Oncology 03/2011; 121(3):434-43. · 3.89 Impact Factor
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ABSTRACT: The acellular fraction of epithelial ovarian cancer (EOC) ascites promotes de novo resistance of tumor cells and thus supports the idea that tumor cells may survive in the surrounding protective microenvironment contributing to disease recurrence. Levels of the pro-inflammatory cytokines IL-6 and IL-8 are elevated in EOC ascites suggesting that they could play a role in tumor progression.
We measured IL-6 and IL-8 levels in the ascites of 39 patients with newly diagnosed EOC. Commercially available enzyme-linked immunosorbent assay (ELISA) was used to determine IL-6 and IL-8 ascites levels. Ascites cytokine levels were correlated with clinicopathological parameters and progression-free survival.
Mean ascites levels for IL-6 and IL-8 were 6419 pg/ml (SEM: 1409 pg/ml) and 1408 pg/ml (SEM: 437 pg/ml) respectively. The levels of IL-6 and IL-8 in ascites were significantly lower in patients that have received prior chemotherapy before the surgery (Mann-Whitney U test, P = 0.037 for IL-6 and P = 0.008 for IL-8). Univariate analysis revealed that high IL-6 ascites levels (P = 0.021), serum CA125 levels (P = 0.04) and stage IV (P = 0.009) were significantly correlated with shorter progression-free survival. Including these variables in a multivariate analysis revealed that elevated IL-6 levels (P = 0.033) was an independent predictor of shorter progression-free survival.
Elevated IL-6, but not IL-8, ascites level is an independent predictor of shorter progression-free survival.
BMC Cancer 01/2011; 11:210. · 3.01 Impact Factor
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ABSTRACT: The production of ascites is a common complication of ovarian cancer. Ascites constitute a unique tumor microenvironment that may affect disease progression. In this context, we recently showed that ovarian cancer ascites may protect tumor cells from TRAIL-induced apoptosis. In this study, we sought to determine whether the prosurvival effect of ascites affects disease-free intervals.
Peritoneal fluids were obtained from 54 women undergoing intra-abdominal surgery for suspected ovarian cancer (44 cancers and 10 benign diseases). The ability of peritoneal fluids to protect from TRAIL was assessed in the ovarian cancer cell line CaOV3, and IC(50 )were determined. The anti-apoptotic activity of 6 ascites against cisplatin, paclitaxel, doxorubicin, etoposide and vinorelbine was also assessed in CaOV3 cells, and the prosurvival activity of two ascites was assessed in 9 primary ovarian cancer cultures.
Among the 54 peritoneal fluids tested, inhibition of TRAIL cytotoxicity was variable. Fluids originating from ovarian cancer were generally more protective than fluids from non-malignant diseases. Most of the 44 ovarian cancer ascites increased TRAIL IC(50 )and this inhibitory effect did not correlate strongly with the protein concentration in these ascites or the levels of serum CA125, a tumor antigen which is used in the clinic as a marker of tumor burden. The effect of ascites on cisplatin- and paclitaxel-induced cell death was assessed with 4 ascites having inhibitory effect on TRAIL-induced cell death and 2 that do not. The four ascites with prosurvival activity against TRAIL had some inhibitory on cisplatin and/or paclitaxel. Two ovarian cancer ascites, OVC346 and OVC509, also inhibited TRAIL cytotoxicity in 9 primary cultures of ovarian tumor and induced Akt activation in three of these primary cultures. Among a cohort of 35 patients with ascites, a threshold of TRAIL IC(50 )with ascites/IC(50 )without ascites > 2 was associated with shorter disease-free interval.
The prosurvival activity of ascites against TRAIL is associated with shorter disease-free interval, which may be explained, at least in part, by ascites-induced cisplatin/paclitaxel resistance. Our findings suggest that ascites may contain prosurvival factors that protect against TRAIL and chemotherapy and consequently affect disease progression.
Journal of Ovarian Research 01/2010; 3:1. · 2.57 Impact Factor
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ABSTRACT: Little is known about the biological functions of CA125/MUC16 tumor antigen. Here, we examined the role of CA125/MUC16 in regulating the sensitivity of epithelial ovarian carcinoma (EOC) cells to different drugs.
An endoplasmic reticulum targeted single-chain antibody (scFv) was used to down-regulate cell surface expression of CA125/MUC16 in NIH:OVCAR3 cells and the C-terminal domain (CTD) of MUC16 was ectopically expressed in CA125-negative SKOV3 cells. Sensitivity to genotoxic agents and to inhibitors of microtubule depolymerization was examined in NIH:OVCAR3 and SKOV3 cell sublines. Cell viability was determined by XTT assay, apoptosis by propidium iodide staining and caspase activation by Western blot and fluorogenic assay.
Down-regulation of cell surface MUC16 decreases cisplatin IC(50) by 5-fold in NIH:OVCAR3 cells but does not affect paclitaxel IC(50). We found that the sensitivity to other genotoxic agents such as cyclophosphamide, doxorubicine and etoposide was also increased by down-regulation of MUC16. Caspase-9 and caspase-3 activation also significantly augmented in cisplatin-treated NIH:OVCAR3 cells expressing the anti-MUC16 scFv. Ectopic expression of MUC16 CTD has the opposite effect. Cisplatin sensitivity and caspases activation are decreased by the ectopic expression of MUC16 CTD in SKOV3 cells.
CA125/MUC16 selectively modulates the sensitivity of EOC cells to genotoxic agents. The MUC16 CTD appears to be sufficient to promote cisplatin resistance.
Gynecologic Oncology 09/2009; 115(3):407-13. · 3.89 Impact Factor
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ABSTRACT: It has been well established that Clostridium difficile toxin A (TcdA) induces cell death in human epithelial cells. However, the mechanism of TcdA-induced cell death remains to be fully characterized. Here, we show that TcdA induces dose-dependent cell death in ovarian carcinoma and colonic carcinoma cell lines. TcdA-mediated cell death, as well as caspase 8 and caspase 3 activation, were specifically abrogated by anti-toxin antibodies. Although caspase 8 and caspase 3 were activated by TcdA in OVCAR3 ovarian carcinoma and T84 colonic cancer cells, pancaspase and caspase 8, 3, and 9 inhibitors did not block TcdA-induced cell death. In contrast, tumor necrosis factor-related apoptosis-inducing ligand-induced cell death was nearly completely blocked by caspase inhibitors in OVCAR3 cells. In these cells, TcdA induces the mitochondrial pathway of apoptosis, as demonstrated by changes in mitochondrial outer membrane permeabilization (MOMP). Furthermore, overexpression of the antiapoptotic proteins Bcl-2 and Bcl-X(L) significantly inhibited TcdA-induced cell death, as well as TcdA-induced MOMP. Conversely, small interfering RNA-mediated inhibition of Bcl-X(L) in TcdA-resistant SKOV3ip1 cells enhanced TcdA-induced cell death. Overexpression of the antiapoptotic proteins Bcl-2 and Bcl-X(L) in T84 cells also inhibited TcdA-induced cell death. Altogether, our data demonstrate that TcdA induces cell death in both ovarian and colonic cancer cells preferentially via the mitochondrial pathway of apoptosis by a death receptor-independent and a caspase-independent mechanism. This process is regulated by antiapoptotic members of the Bcl-2 family.
Infection and immunity 09/2009; 77(12):5400-10. · 4.21 Impact Factor
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ABSTRACT: Ascites are commonly found in ovarian cancer patients with advanced disease and are rich in cellular components and growth-promoting factors. The purpose of this study was to assess the effect of malignant ascites on TRAIL-induced apoptosis. We demonstrate that malignant ascites obtained from women with advanced ovarian cancer protect tumor cells from TRAIL- and FasL-induced apoptosis but not against cisplatin-induced apoptosis. This antiapoptotic effect was consistently found among different malignant ascites while nonmalignant peritoneal fluids or conditioned medium from TRAIL-resistant cells failed to protect tumor cells against TRAIL killing. Malignant ascites strongly inhibits TRAIL-induced caspase-3 activation and PARP cleavage. Furthermore, ascites activate PI3K and its downstream target Akt and increases c-FLIP(S) protein levels without affecting ERK phosphorylation status. The antiapoptotic effect of malignant ascites is abrogated by the inhibition of PI3K with LY294002, by a specific inhibitor of Akt and by Akt siRNA. We further show that the pro-survival effect of ascites can be suppressed by down-regulation of c-FLIP(S). Our data indicate that malignant effusions protect against TRAIL-induced apoptosis by activating the PI3K/Akt pathway. These findings demonstrate that the tumor microenvironment may contribute to the resistance of ovarian cancer cells to death receptor-induced apoptosis.
International Journal of Cancer 10/2007; 121(6):1227-37. · 5.44 Impact Factor
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ABSTRACT: Little is known on how cancer cells can acquire resistance to tumor necrosis factor-related apoptosis-inducing ligand (TRAIL). In this study, we established TRAIL-resistant cells from the TRAIL-sensitive human ovarian carcinoma cell line OVCAR3 to evaluate the potential mechanisms of acquired resistance to TRAIL. The selected resistant cells were cross-resistant to Fas ligand but remained sensitive to drug-induced apoptosis. Expression of TRAIL receptors was not altered in TRAIL-resistant OVCAR3 cells. Cleavage of caspase-8 and caspase-3 occurred in both TRAIL-resistant and TRAIL-sensitive cells. However, mature caspase-3 fragments were not detected by immunoblot in TRAIL-resistant cells and caspase-3 activity was significantly inhibited in these cells. The addition of proteasome inhibitors significantly increased TRAIL-induced apoptosis in resistant cells and enhanced the accumulation of mature caspase-3 fragments. Pretreatment with cycloheximide showed that active caspase-3 fragments have a high turnover rate in OVCAR3 R350 cells. X-linked inhibitor of apoptosis down-regulation by RNA interference also increased the accumulation of cleaved caspase-3 intermediates and resensitized TRAIL-resistant cells. Our findings show that altered turnover of mature caspase-3 may lead to acquired TRAIL resistance in ovarian cancer cells. Proteasome and X-linked inhibitor of apoptosis inhibitors could have a role in clinical situations to potentiate the cytotoxic effects of TRAIL in resistant tumor cells.
Molecular Cancer Therapeutics 04/2006; 5(3):509-21. · 5.23 Impact Factor
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ABSTRACT: To investigate the role of Bcl-X(L) on the growth and survival of human ovarian carcinoma cells.
In this study, we enforced down-regulation of Bcl-X(L) by RNA interference in ovarian carcinoma cell lines CaOV3, SKOV3ip1 and OVCAR3 cell lines expressing various levels of Bcl-X(L). We also established stable transfectants of OVCAR3 cells overexpressing Bcl-X(L). We recently showed that Bcl-2 regulates cell cycle progression in ovarian cancer cells. Thus, the effect of Bcl-X(L) modulation on the rate of cell growth was determined by XTT assay. To evaluate the role of Bcl-X(L) in drug-induced apoptosis, cisplatin- and paclitaxel-induced apoptosis were determined in vitro for each of the three cell lines. Ovarian tumor cells must acquire the ability to survive in non-adherent conditions to grow in ascetic fluids. To mimic loss of anchorage and investigate the role of Bcl-X(L) in this process, cells were cultured on Hydrogel-coated plates and nuclear fragmentation, caspase-3 activation and nuclear propidium iodide staining were used to determine apoptosis.
We show that enforced down-regulation of Bcl-X(L) protein significantly affected the growth rates of CaOV3 whereas it had only minimal effect on the other two cell lines. Down-regulation of Bcl-X(L) enhanced the sensitivity of CaOV3, OVCAR3 and SKOV3ip1 to cisplatin and paclitaxel. The susceptibility to apoptosis induced by loss of anchorage was also increased but in a cell line-dependent manner. Overexpression of Bcl-X(L) slowed the growth of OVCAR3 cells and conferred resistance to drug-induced apoptosis and apoptosis induced by loss of anchorage.
Altogether, these findings demonstrate that modulation of Bcl-X(L) provokes changes in ovarian cancer cell growth and survival that are cell line-specific. Consequently, therapeutic strategy for treatment of ovarian cancer that target Bcl-X(L) will likely yield variable responses.
Gynecologic Oncology 03/2006; 100(2):254-63. · 3.89 Impact Factor
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ABSTRACT: The Bcl-2 protein is an important regulator of the apoptotic cascade and promotes cell survival. Bcl-2 can also delay entry into the cell cycle from quiescence. In the present study, we used two isogenic human ovarian carcinoma cell lines, which expressed differential levels of Bcl-2 proteins, to demonstrate that Bcl-2 may regulate the growth rates of adenocarcinoma cells.
The growth rates of two isogenic ovarian cancer cell lines were determined by XTT assays and flow cytometry combined with PI staining. Bcl-2-overexpressing SKOV3 cells were modified to express a doxycycline-inducible anti-Bcl-2 single-chain antibody and the effects of Bcl-2 protein inhibition on cell proliferation and apoptosis were assessed.
We demonstrate that Bcl-2 promotes the accumulation of proliferating carcinoma cells in S phase. The Bcl-2-overexpressing SKOV3 cell line proliferates markedly faster and shows delayed progression to G2M phase compared to its low Bcl-2-expressing counterpart SKOV3.ip1 cell line. Single-chain antibody-mediated inhibition of Bcl-2 in SKOV3 cells was associated with increased growth rates and more rapid cell cycle progression. Treatment with cisplatin resulted in more cells accumulating in S phase in Bcl-2-overexpressing SKOV3 cells, while the inhibition of Bcl-2 abolished delayed entry into G2M phase without affecting cisplatin-induced apoptosis.
Our results suggest that, in ovarian cancer cells, Bcl-2 delays cell cycle progression by promoting accumulation of cells in S phase without affecting the rate of apoptosis. Thus, in addition to its known role at the G0/G1 checkpoint, we demonstrate for the first time that Bcl-2 also regulates the S phase.
Gynecologic Oncology 07/2005; 97(3):796-806. · 3.89 Impact Factor
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ABSTRACT: BAG-1 is a multi-functional protein that exists in three major isoforms, BAG-1 p50, p46, and p36. A fourth isoform of 29 kDa also exists but its function remains mostly unknown. To further understand the role of this smaller isoform in ovarian cancer cells, the SKOV3 cell line was transfected with a doxycycline-inducible human BAG-1 p29 isoform or control plasmid. Ovexpression of BAG-1 p29 promotes protection from apoptosis in the presence of EGF as shown by decreased cell death measured by XTT assay and caspase-3 activity. Unexpectedly, however, BAG-1 p29 does not associate with the EGF receptor. When BAG-1 p29 transfectants were incubated in hydrogel-coated plates, BAG-1 p29-expressing SKOV3 cells were significantly more resistant to anoikis as compared to controls, and this correlated with decreased activation of caspase-3. The results of this study implicate BAG-1 p29 in the regulation of both the EGF signaling cascade and the apoptotic cascade induced by loss of anchorage.
Biochemical and Biophysical Research Communications 04/2005; 328(4):874-84. · 2.48 Impact Factor
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ABSTRACT: In this study, we examine the sensitivity of a panel of ovarian carcinoma cells, which includes four primary ovarian cancer cell samples, and four normal ovarian epithelium samples to tumor necrosis factor-related apoptosis-inducing ligand (TRAIL). We also examine the intracellular regulation of TRAIL-mediated apoptosis.
The sensitivity to TRAIL was determined by short-term survival assays on seven ovarian carcinoma cell lines, four primary samples of ovarian cancer, and four normal ovarian epithelium samples. We assessed the activation of the apoptotic pathway in TRAIL-resistant and -sensitive tumor cells. The expression of TRAIL receptors was determined by flow cytometry. The protein expression of FADD, XIAP, caspase-8, caspase-3, BAX, and c-FLIP were determined by immunoblot analyses.
We show that ovarian cancer cells display variable sensitivity to TRAIL-induced apoptosis although most cell lines have similar sensitivity to cisplatin. Normal ovarian epithelium samples were mostly sensitive to TRAIL. In sensitive cells, TRAIL induced caspase-8-dependent apoptosis, which subsequently led to activation of caspase-3. Both sensitive and resistant cells expressed caspase-8, caspase-3, FADD, XIAP, and c-FLIP at similar levels. A significant enhancement in cell death was observed in TRAIL-resistant cells when c-FLIP(L) levels were downregulated by RNA interference.
These data suggest that sensitivity to TRAIL and chemotherapy does not necessarily correlate in human ovarian cancer cells. Cancerous cells isolated from patients with ovarian cancer show variable sensitivity to TRAIL but most normal ovarian epithelial cells are sensitive. In human ovarian cancer cells, c-FLIP(L) may participate to the regulation of the TRAIL signaling cascade.
Gynecologic Oncology 07/2004; 93(3):594-604. · 3.89 Impact Factor
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ABSTRACT: Objective.To investigate the role of Bcl-XL on the growth and survival of human ovarian carcinoma cells.Methods.In this study, we enforced down-regulation of Bcl-XL by RNA interference in ovarian carcinoma cell lines CaOV3, SKOV3ip1 and OVCAR3 cell lines expressing various levels of Bcl-XL. We also established stable transfectants of OVCAR3 cells overexpressing Bcl-XL. We recently showed that Bcl-2 regulates cell cycle progression in ovarian cancer cells. Thus, the effect of Bcl-XL modulation on the rate of cell growth was determined by XTT assay. To evaluate the role of Bcl-XL in drug-induced apoptosis, cisplatin- and paclitaxel-induced apoptosis were determined in vitro for each of the three cell lines. Ovarian tumor cells must acquire the ability to survive in non-adherent conditions to grow in ascetic fluids. To mimic loss of anchorage and investigate the role of Bcl-XL in this process, cells were cultured on Hydrogel-coated plates and nuclear fragmentation, caspase-3 activation and nuclear propidium iodide staining were used to determine apoptosis.Results.We show that enforced down-regulation of Bcl-XL protein significantly affected the growth rates of CaOV3 whereas it had only minimal effect on the other two cell lines. Down-regulation of Bcl-XL enhanced the sensitivity of CaOV3, OVCAR3 and SKOV3ip1 to cisplatin and paclitaxel. The susceptibility to apoptosis induced by loss of anchorage was also increased but in a cell line-dependent manner. Overexpression of Bcl-XL slowed the growth of OVCAR3 cells and conferred resistance to drug-induced apoptosis and apoptosis induced by loss of anchorage.Conclusion.Altogether, these findings demonstrate that modulation of Bcl-XL provokes changes in ovarian cancer cell growth and survival that are cell line-specific. Consequently, therapeutic strategy for treatment of ovarian cancer that target Bcl-XL will likely yield variable responses.
Gynecologic Oncology.
