Synergistic induction of apoptosis by the combination of trail and chemotherapy in chemoresistant ovarian cancer cells

Synergistic induction of tumor cell apoptosis by death receptor antibody and chemotherapy agent through JNK/p38 and mitochondrial death pathway

Using two agonistic monoclonal antibodies specific for each death receptor of TRAIL, 2E12 (anti-human DR4) and TRA-8 (anti-human DR5), we examined the signal transduction of the death receptors in combination with or without chemotherapy agents such as Adriamycin (doxorubicin hydrochloride) and Cisplatin. Our results demonstrated that chemotherapy agents were able to enhance apoptosis-inducing activity of these antibodies against several different types of tumor cell lines through enhanced caspase activation. The combination of the antibodies and chemotherapy agents led to a synergistical activation of the JNK/p38 MAP kinase, which was mediated by MKK4. The combination also caused an increased release of cytochrome c and Smac/DIABLO from mitochondria in parallel with the profound loss of mitochondrial membrane potential. These results suggest that the enhanced activation of the JNK/p38 kinase and the mitochondrial apoptosis pathways play a crucial role in synergistic induction of the death receptor-mediated apoptosis by chemotherapy agents. Thus, the simultaneous targeting of cell surface death receptors with agonistic antibodies and the intracellular JNK/p38 and the mitochondrial death pathways with chemotherapy agents would enhance the efficacy and selectivity of both agents in cancer therapy.

Molecular determinants of epothilone B derivative (BMS 247550) and Apo-2L/TRAIL-induced apoptosis of human ovarian cancer cells

OBJECTIVE

We determined the cytotoxic effects BMS 247550 (Epo B), a derivative of epothilone B, on cisplatinum- or paclitaxel-sensitive or -resistant human ovarian cancer cells. Additionally, we determined the effect of Epo B on Apo-2L/TRAIL-induced apoptosis of ovarian cancer cells.

METHODS

Epo B-induced cytotoxic and cell cycle effects were evaluated by the MTT assay and flow cytometry, respectively. Epo B-induced apoptosis was assessed by immunoblot analyses of the processing and proteolytic activity of caspases, flow cytometric measurement of annexin V staining, and the TUNEL assay. The effects of Epo B and/or Apo-2L/TRAIL on the protein expressions of the death receptors DR4 and DR5 as well as of XIAP and survivin were determined by immunoblot analyses.

RESULTS

In the cell cycle-synchronized ovarian cancer cells, Epo B induced tubulin polymerization and mitotic arrest, followed by apoptosis. This was associated with the cytosolic accumulation of cytochrome (cyt) c and Smac/DIABLO as well as PARP cleavage activity of caspase-3. Epo B was able to exert cytotoxic effects against cisplatinum- and paclitaxel-resistant ovarian cancer cells. Epo B increased the expressions of DR4 and DR5, as well as augmented Apo-2L/TRAIL-induced processing of caspase-8 and Bid. This was associated with more caspase-3 activity, a decline in the intracellular levels of XIAP, cIAP, and survivin, and apoptosis of ovarian cancer cells.

CONCLUSIONS

These data support the in vivo testing of Epo B against cisplatinum- and paclitaxel-resistant ovarian cancers, and suggest that a pretreatment with Epo B may sensitize human ovarian cancers to the cytotoxic effects of Apo-2L/TRAIL.

Physiological and molecular effects of Apo2L/TRAIL and cisplatin in ovarian carcinoma cell lines

Combining of tumor necrosis factor-related apoptosis-inducing ligand (Apo2L/TRAIL) with a chemotherapeutic drug, cisplatin, in ovarian carcinoma cell lines exerted potent anti-tumor effects that exceeded the effects of each drug alone. In order to investigate mechanisms of anti-tumor activity of cisplatin/Apo2L/TRAIL combination, we assessed in detail the molecular effects of cisplatin and Apo2L/TRAIL-activated cell death in two ovarian carcinoma cell lines, OVCAR3 and SKOV3, using cDNA array hybridization, Western blot and flow cytometry. We observed differential induction of apoptosis-related molecules by cisplatin and Apo2L/TRAIL. Cisplatin upregulated the expression of both death and decoy TRAIL receptors, as well as of TRAF5 and -6, downregulated the anti-apoptotic proteins, Bcl-2, and induced activation of caspases-3, -8 and -9. Apo2L/TRAIL induced the expression of pro-apoptotic proteins, Bad and Bax; downregulated the anti-apoptotic proteins, Bcl-2 and Bcl-xL; and activated caspases-3, -7, -8, -9 and -10. Cisplatin/Apo2L/TRAIL combination resulted in further downregulation of expression of anti-apoptotic proteins, Bcl-2 and Bcl-xL, as well as an increase in mitochondrial permeability transition and activation of caspases-3, -8, and -10. These data demonstrate positive cooperation of cisplatin and Apo2L/TRAIL and emphasize the potential clinical usefulness of cisplatin/Apo2L/TRAIL combination therapy.

Synergistic induction of apoptosis in human myeloid leukemia cells by phorbol 12-myristate 13-acetate and flavopiridol proceeds via activation of both the intrinsic and tumor necrosis factor-mediated extrinsic cell death pathways

Previous studies have shown that coexposure to marginally toxic concentrations of phorbol 12-myristate 13-acetate (PMA; 10 nM) and the cyclin-dependent kinase inhibitor flavopiridol (FP; 100-200 nM) synergistically induces apoptosis in human myeloid leukemia cells U937 and HL-60 (i.e., >50% apoptotic at 24 h). Attempts have now been made to characterize the cell death pathway(s) involved in this phenomenon. In contrast to cytochrome c release and caspase-3 activation, which occur within 2.5 h of PMA/FP coexposure, caspase-8 activation and Bid cleavage appeared as later events. Such findings implicate the mitochondria-dependent pathway in the initial induction of apoptosis by PMA/FP. However, U937 cells ectopically expressing CrmA, dominant-negative caspase-8, or dominant-negative Fas-associated death domain that were highly resistant to tumor necrosis factor (TNF)/cycloheximide-induced lethality displayed significant, albeit incomplete, resistance to PMA/FP-induced apoptosis after 24 h. Furthermore, coadministration of TNF soluble receptor significantly attenuated PMA/FP-induced apoptosis in U937 (p < 0.02) and HL-60 (p < 0.03) cells at 24 h. PMA/FP coadministration also triggered substantial increases in TNFalpha mRNA and protein secretion compared with the effects of PMA administered alone. The protein kinase C (PKC) inhibitor bisindolylmaleimide (1 microM) completely blocked PMA/FP-induced TNFalpha secretion in U937 cells and attenuated apoptosis. Taken together, these results suggest that coadministration of PMA with FP in myeloid leukemia cells initially triggers mitochondrial damage, an event followed by the PKC-dependent induction and release of TNFalpha, supporting a model in which the synergistic induction of leukemic cell apoptosis by this drug combination proceeds via both mitochondrial- and TNF receptor-related apoptotic pathways.

Increased expression of dihydrodiol dehydrogenase induces resistance to cisplatin in human ovarian carcinoma cells

We employed cDNA microarrays to identify the differentially expressed genes in a cisplatin-sensitive parental (2008) human ovarian carcinoma cell line and its cisplatin-resistant variant (2008/C13*). Differential expression of five genes was found in the 2008/C13* cells, a result confirmed by semi-quantitative reverse transcription-PCR. The five genes were identified as fibroblast muscle-type tropomyosin and skeletal muscle-type tropomyosin, dihydrodiol dehydrogenase, apolipoprotein J and glucose-6-phosphate dehydrogenase variant-A. Treatment of the 2008 cells with cisplatin (at its IC(50) concentration of 2 microm) induced expression of these genes, as determined by semi-quantitative reverse transcription-PCR analysis using gene-specific primers. In contrast, treatment of the drug-resistant 2008/C13* cells with cisplatin (at its IC(50) concentration of 20 microm) did not lead to the induction of any of the aforementioned genes. Most importantly, constitutive overexpression of dihydrodiol dehydrogenase (but not the other genes) in the 2008 cells led to induction of cisplatin resistance, clearly indicating its role in the development of the resistance phenotype in the 2008/C13* cells. The development of cisplatin resistance in the transfected cells was associated with an increase in the dihydrodiol dehydrogenase enzyme activity. Although at present it is not clear how dihydrodiol dehydrogenase is involved in cisplatin resistance, the identification of this gene as a causal factor suggests the existence of a hitherto undefined pathway resulting in cisplatin resistance.

Inositol hexakisphosphate kinase 2 sensitizes ovarian carcinoma cells to multiple cancer therapeutics

We recently identified inositol hexakisphosphate kinase 2 (IP6K2) as a positive regulator of apoptosis. Overexpression of IP6K2 enhances apoptosis induced by interferon-beta (IFN-beta) and cytotoxic agents in NIH-OVCAR-3 ovarian carcinoma cells. In this study, we contrast and compare IFN-beta and radiation-induced death, and show that IP6K2 expression sensitizes tumor cells. Unirradiated NIH-OVCAR-3 cells transfected with IP6K2 formed fewer colonies compared to unirradiated vector-expressing cells. IP6K2 overexpression caused increased radiosensitivity, evidenced by decreased colony forming units (CFU). Both IFN-beta and radiation induced caspase 8. IFN-beta, but not gamma-irradiation, induced TRAIL in NIH-OVCAR-3 cells. Gamma irradiation, but not IFN-beta, induced DR4 mRNA. Apoptotic effects of IFN-beta or gamma-irradiation were blocked by expression of a dominant negative mutant death receptor 5 (DR5Delta) or by Bcl-2. Caspase-8 mRNA induction was more pronounced in IP6K2-expressing cells compared to vector-expressing cells. These data suggest that overexpression of IP6K2 enhances sensitivity of some ovarian carcinomas to radiation and IFN-beta. IP6K2 may function to enhance the expression and/or function of caspase 8 and DR4 following cell injury. Both IFN-beta and gamma-irradiation induce apoptosis through the extrinsic, receptor-mediated pathway, IFN-beta through TRAIL, radiation through DR4, and both through caspase 8. The function of both death inducers is positively regulated by IP6K2.

Insights into cancer therapeutic design based on p53 and TRAIL receptor signaling

Knowledge of the emerging pathways of cell death downstream of the p53 tumor suppressor and the TRAIL death-inducing ligand is suggesting ways to improve therapeutic design in cancer. In contrast to its unique G1 cell cycle arresting mechanism that is maintained by p21(WAF1), there are signals transduced by p53 to multiple apoptotic effectors perhaps due to the importance of apoptosis in suppressing tumors. There is evidence for cytoplasmic as well as mitochondrial activation of caspases downstream of p53, although in some cell lineages the signal ultimately involves the mitochondria. The TRAIL signaling pathway appears promising for therapeutic development despite sharing some similarities with the toxic Fas and TNF pathways, in terms of effector molecules and downstream signals. One of the key findings is the tissue specificity of cell death responses, a feature that could be exploited in strategies to widen the therapeutic window of combination cancer therapies. Efforts continue to develop p53-targeted cancer therapy, and novel clues to enhance or block specific effectors may improve therapeutic design.

Caspase 8-dependent sensitization of cancer cells to TRAIL-induced apoptosis following reovirus-infection

TRAIL (TNF-related apoptosis-inducing ligand) induces apoptosis in susceptible cells by binding to death receptors 4 (DR4) and 5 (DR5). TRAIL preferentially induces apoptosis in transformed cells and the identification of mechanisms by which TRAIL-induced apoptosis can be enhanced may lead to novel cancer chemotherapeutic strategies. Here we show that reovirus infection induces apoptosis in cancer cell lines derived from human breast, lung and cervical cancers. Reovirus-induced apoptosis is mediated by TRAIL and is associated with the release of TRAIL from infected cells. Reovirus infection synergistically and specifically sensitizes cancer cell lines to killing by exogenous TRAIL. This sensitization both enhances the susceptibility of previously resistant cell lines to TRAIL-induced apoptosis and reduces the amount of TRAIL needed to kill already sensitive lines. Sensitization is not associated with a detectable change in the expression of TRAIL receptors in reovirus-infected cells. Sensitization is associated with an increase in the activity of the death receptor-associated initiator caspase, caspase 8, and is inhibited by the peptide IETD-fmk, suggesting that reovirus sensitizes cancer cells to TRAIL-induced apoptosis in a caspase 8-dependent manner. Reovirus-induced sensitization of cells to TRAIL is also associated with increased cleavage of PARP, a substrate of the effector caspases 3 and 7.

Potential and caveats of TRAIL in cancer therapy

Induction of apoptosis in tumor cells is a major goal for chemotherapy and radiation treatment strategies. However, disordered gene expression often leads to apoptosis resistance rendering tumor cells insensitive to various conventional treatments. TNF-related apoptosis-inducing ligand (TRAIL) is a recently identified cytokine of the TNF superfamily that induces apoptosis in tumor cells upon binding to different receptors. Remarkably, the majority of tumor cell lines are sensitive to TRAIL-induced apoptosis, while most nontransformed cell types are TRAIL-resistant. Furthermore, a combination treatment of TRAIL with ionizing irradiation or chemotherapeutic agents induces apoptosis in a highly synergistic manner, particularly in those cells that are otherwise resistant to a sole treatment. In contrast to other TNF members, TRAIL apparently does not exert overt systemic toxicity in murine and primate models, although unexpected concerns about a potential hepatotoxicity of TRAIL have been recently raised. While the molecular mechanisms of TRAIL sensitivity and resistance are poorly understood, TRAIL seems to be a promising biological agent for combination therapy with chemotherapeutic drugs or irradiation.

[Haptoglobin and orosomucoid in the blood in a case of congenital afibrinogenemia and in the family of the patient]

Background

TRAIL (tumor necrosis factor related apoptosis inducing ligand) is an apoptosis inducing ligand with high specificity for malignant cell systems. Combined treatment modalities using TRAIL and cytotoxic drugs revealed highly additive effects in different tumour cell lines. Little is known about the efficacy and underlying mechanistic effects of a combined therapy using TRAIL and ionising radiation in solid tumour cell systems. Additionally, little is known about the effect of TRAIL combined with radiation on normal tissues.

Methods

Tumour cell systems derived from breast- (MDA MB231), lung- (NCI H460) colorectal- (Colo 205, HCT-15) and head and neck cancer (FaDu, SCC-4) were treated with a combination of TRAIL and irradiation using two different time schedules. Normal tissue cultures from breast, prostate, renal and bronchial epithelia, small muscle cells, endothelial cells, hepatocytes and fibroblasts were tested accordingly. Apoptosis was determined by fluorescence microscopy and western blot determination of PARP processing. Upregulation of death receptors was quantified by flow cytometry.

Results

The combined treatment of TRAIL with irradiation strongly increased apoptosis induction in all treated tumour cell lines compared to treatment with TRAIL or irradiation alone. The synergistic effect was most prominent after sequential application of TRAIL after irradiation. Upregulation of TRAIL receptor DR5 after irradiation was observed in four of six tumour cell lines but did not correlate to tumour cell sensitisation to TRAIL. TRAIL did not show toxicity in normal tissue cell systems. In addition, pre-irradiation did not sensitise all nine tested human normal tissue cell cultures to TRAIL.

Conclusions

Based on the in vitro data, TRAIL represents a very promising candidate for combination with radiotherapy. Sequential application of ionising radiation followed by TRAIL is associated with an synergistic induction of cell death in a large panel of solid tumour cell lines. However, TRAIL receptor upregulation may not be the sole mechanism by which sensitation to TRAIL after irradiation is induced.