Overcoming drug resistance in ovarian carcinoma

Yolk-Shell-Type Gold Nanoaggregates for Chemo- and Photothermal Combination Therapy for Drug-Resistant Cancers

Epithelial ovarian cancer is a gynecological cancer with the highest mortality rate, and it exhibits resistance to conventional drugs. Gold nanospheres have gained increasing attention over the years as photothermal therapeutic nanoparticles, owing to their excellent biocompatibility, chemical stability, and ease of synthesis; however, their practical application has been hampered by their low colloidal stability and photothermal effects. In the present study, we developed a yolk-shell-structured silica nanocapsule encapsulating aggregated gold nanospheres (aAuYSs) and examined the photothermal effects of aAuYSs on cell death in drug-resistant ovarian cancers both in vitro and in vivo. The aAuYSs were synthesized using stepwise silica seed synthesis, surface amino functionalization, gold nanosphere decoration, mesoporous organosilica coating, and selective etching of the silica template. Gold nanospheres were agglomerated in the confined silica interior of aAuYSs, resulting in the red-shifting of absorbance and enhancement of the photothermal effect under 808 nm laser irradiation. The efficiency of photothermal therapy was first evaluated by inducing aAuYS-mediated cell death in A2780 ovarian cancer cells, which were cultured in a two-dimensional culture and a three-dimensional spheroid culture. We observed that photothermal therapy using aAuYSs together with doxorubicin treatment synergistically induced the cell death of doxorubicin-resistant A2780 cancer cells in vitro. Furthermore, this type of combinatorial treatment with photothermal therapy and doxorubicin synergistically inhibited the in vivo tumor growth of doxorubicin-resistant A2780 cancer cells in a xenograft transplantation model. These results suggest that photothermal therapy using aAuYSs is highly effective in the treatment of drug-resistant cancers.

P-glycoprotein antagonists confer synergistic sensitivity to short-chain ceramide in human multidrug-resistant cancer cells

P-glycoprotein (P-gp) antagonists inhibit ceramide metabolism at the juncture of glycosylation. The purpose of this study was to test whether targeting P-gp would be a viable alternative to targeting glucosylceramide synthase (GCS) for enhancing ceramide cytotoxicity. A2780 wild-type, and multidrug-resistant 2780AD and NCI/ADR-RES human ovarian cancer cell lines and the cell-permeable ceramide analog, C6-ceramide (C6-cer), were employed. Compared to P-gp-poor A2780 cells, P-gp-rich 2780AD cells converted 3.7-fold more C6-cer to nontoxic C6-glucosylceramide (C6-GC), whereas cell-free GCS activities were equal. 2780AD cells displayed resistance to C6-cer (10 μM) that was reversed by inclusion of the P-gp antagonist tamoxifen (5 μM) but not by inclusion of a GCS inhibitor. Co-administration of C6-cer and P-gp antagonists was also effective in NCI/ADR-RES cells. For example, C6-cer, VX-710 (Biricodar), and cyclosporin A (cyc A) exposure resulted in viabilities of ~90% of control; however, C6-cer/VX-710 and C6-cer/cyc A additions were synergistic and resulted in viabilities of 22% and 17%, respectively. Further, whereas C6-ceramide and cyc A imparted 1.5- and 0-fold increases in caspase 3/7 activity, the combination produced a 3.5-fold increase. Although the upstream elements of cell death have not been elucidated, the novel C6-ceramide/P-gp antagonist combination merits further study and assessment of clinical translational potential.

Vitamin E prevents buthionine sulfoximine-induced biochemical disorders in the rat

Antioxidant therapy can improve the protection and metabolic activity of cells and tissues. In this study, the effect of vitamin E administration on buthionine sulfoximine (BSO)-induced glutathione (GSH) depletion in the rat lung and liver was investigated. Hepatic GSH was depleted by intraperitoneal administration of BSO (4 mmol kg−1), twice a day, for 30 days to rats. We also investigated whether the lung and liver mitochondrial GSH contents were influenced by BSO administration and whether an extracellular supply of vitamin E could prevent the changes caused by BSO-mediated GSH depletion. Glutathione levels in lung and liver tissues were depleted by 47% and 60%, respectively. Depletion of hepatic and pulmonary GSH in turn causes decline in the levels of mitochondrial GSH, leading to impaired antioxidant defence function of mitochondria. Both the cytosolic and mitochondrial glutathione disulfides (GSSG) were altered during BSO treatment, and led to drastic increase in GSSG/GSH redox status. One of the experimental groups was given vitamin E (65 mg (kg diet)−1) mixed with rat feed. The rats fed with vitamin E were found to have partially restored GSH levels in liver and lung, diminished levels of TBARS and minimized tissue damage. The current findings suggest that the impaired glutathione and glutathione-dependent enzyme status may be correlated with the elevated lipid peroxidation and mitochondrial membrane damage and that vitamin E therapy to the BSO-administered rats prevents the above changes. However, vitamin E did not have any effect on the activity of γ-glutamyl cysteine synthetase (γ-GCS).

Ovarian carcinoma cells with low levels of beta-F1-ATPase are sensitive to combined platinum and 2-deoxy-D-glucose treatment

We have here examined chemopotentiating effects of glycolysis inhibitor 2-deoxy-d-glucose (DG) in two epithelial ovarian carcinoma (EOC) cell lines and 17 freshly isolated ascitic EOC cell samples, and we identify low expression of the beta-F1-ATPase involved in mitochondrial ATP production as a candidate marker for sensitivity to this strategy. Although in the majority of samples, DG per se did not induce apoptosis, cotreatment with DG potentiated apoptosis and total antiproliferative effects of cisplatin and, to a lesser degree, carboplatin. In the cell lines, combination treatment with DG and cisplatin or carboplatin at noninhibitory concentrations prevented posttreatment regrowth in drug-free medium over a total of 5 days. DG per se allowed complete recuperation in drug-free medium. The more platinum-resistant a cell line was, the more sensitive it was to potentiation by DG and showed higher glucose uptake, DG-sensitive lactate production, and lower beta-F1-ATPase levels. In the ascitic samples, DG reduced the median IC(50) for cisplatin by 68% and, in the most sensitive samples, up to 90%, and DG-mediated potentiation correlated with low expression of beta-F1-ATPase. By contrast, cisplatin sensitivity did not correlate with beta-F1-ATPase levels. The findings validate targeting cancer cell glucose metabolism for potentiating platinum chemotherapy in EOC and indicate that reduced beta-F1-ATPase/oxidative phosphorylation distinguishes cells that are amenable to this strategy.

Phase III study of valspodar (PSC 833) combined with paclitaxel and carboplatin compared with paclitaxel and carboplatin alone in patients with stage IV or suboptimally debulked stage III epithelial ovarian cancer or primary peritoneal cancer

PURPOSE

To compare the safety and efficacy of carboplatin and paclitaxel administered with or without the multidrug resistance modulator valspodar (PSC 833) in untreated patients with advanced ovarian or primary peritoneal cancer.

PATIENTS AND METHODS

Seven hundred sixty-two patients with stage IV or suboptimally debulked stage III ovarian or primary peritoneal cancer were randomly assigned to receive either valspodar 5 mg/kg every 6 hours for 12 doses, paclitaxel 80 mg/m(2), and carboplatin area under the curve (AUC) 6 (PC-PSC; n = 381) or paclitaxel 175 mg/m(2) and carboplatin AUC 6 (PC; n = 381). Time to disease progression (TTP) was the primary end point. Secondary end points were overall survival time (OS), response rate (RR), safety, and tolerability.

RESULTS

With a median follow-up of 736 days (range, 1 to 2,280 days), the median TTP was 13.2 and 13.5 months in the PC-PSC and PC groups, respectively (P = .67); the median OS was 32 and 28.9 months, respectively (P = .94). The overall RR was higher in the PC group (41.5% v 33.6%; P = .02). Central and peripheral nervous system and GI toxicities were more common in the PC-PSC group. Ataxia occurred in 53.5% and 3.2% of PC-PSC-and PC-treated patients, respectively. Febrile neutropenia occurred more frequently in the PC-PSC group. More PC-PSC-treated patients discontinued therapy because of adverse events (AEs), experienced serious AEs, and required paclitaxel dose reductions.

CONCLUSION

The addition of valspodar to PC did not improve TTP or OS and was more toxic compared with PC in untreated patients with advanced ovarian or primary peritoneal cancer.

Availability and applications of ATP-binding cassette (ABC) transporter blockers

ATP-binding cassette (ABC) transporters encompass membrane transport proteins that couple the energy derived from ATP hydrolysis to the translocation of solutes across biological membranes. The functions of these proteins include ancient and conserved mechanisms related to nutrition and pathogenesis in bacteria, spore formation in fungi, and signal transduction, protein secretion and antigen presentation in eukaryotes. Furthermore, one of the major causes of drug resistance and chemotherapeutic failure in both cancer and anti-infective therapies is the active movement of compounds across membranes carried out by ABC transporters. Thus, the clinical relevance of ABC transporters is enormous, and the membrane transporters related to chemoresistance are among the best-studied members of the ABC transporter superfamily. As ABC transporter blockers can be used in combination with current drugs to increase their efficacy, the (possible) impact of efflux pump inhibitors is of great clinical interest. The present review summarizes the progress made in recent years in the identification, design, availability, and applicability of ABC transporter blockers in experimental scenarios oriented towards improving the treatment of infectious diseases caused by microorganisms including parasites.

Anticancer drugs induce mdr1 gene expression in recurrent ovarian cancer

Ovarian cancer is currently the most lethal gynecologic malignancy in Europe and the US. Platin analogues and paclitaxel demonstrate high remission rates, but unfortunately the efficacy of cytostatic agents is limited by the development of multidrug resistance (mdr). Clinical paclitaxel resistance is often associated with mdr1 overexpression. In a recent study, we introduced a highly specific quantitative real-time reverse transcriptase polymerase chain reaction for the quantification of mdr1 transcripts. In the present study, we demonstrate that primary tumor cells from patients with recurrent ovarian cancer overexpress mdr1. To evaluate mdr1 expression, we collected tumor cells from 77 ovarian cancer patients (13 chemotherapy-naive ovarian cancer, 64 recurrent ovarian cancer). Cancer cells were aspirated from 49 solid specimens (63%) and 28 ascitic fluids (37%). Subsequently, cancer cells were exposed in 221 short-term cultures either to blank medium (control) or to a single anticancer drug, cisplatin, doxorubicin or paclitaxel. The drug concentrations applied referred to clinical relevant doses. mdr1 mRNA expression was significantly higher in specimens from recurrent ovarian cancer incubated in paclitaxel than in specimens from chemotherapy-naive ovarian cancer. No significant differences were detectable between the mean value of mdr1 mRNA expression in tumor specimens from recurrent ovarian cancer incubated in cisplatin or doxorubicin. Differences within the untreated patients group were also not statistically significant. The result of this study confirms clinical observations, as well as in-vitro studies based on tumor cell lines, that paclitaxel resistance is correlated with mdr1 overexpression.

Epigallocatechin-3-gallate delivers hydrogen peroxide to induce death of ovarian cancer cells and enhances their cisplatin susceptibility

The green tea polyphenol epigallocatechin-3-gallate (EGCG) has cancer chemopreventive properties against various types of cancers. The compound is known to attack various targets in transformed cells. In this report, we examined the action of EGCG on ovarian cancer cells. Eight ovarian cancer cell lines were tested (SKOV3, CAOV3, OVCAR3, OVCAR10, A2780, CP70, C30, and C200) and showed IC50s for EGCG at the micromolar range, including ones that are resistant to the chemotherapeutic drug cisplatin. The ovarian cancer cells were sensitive to H2O2 at similar concentrations, and EGCG treatment led to enhanced intracellular H2O2. Neutralization with pyruvate, a scavenger of H2O2, suggests that the toxicity of EGCG may be mediated by oxidative stress from the free radical. Addition of Tempol, a superoxide dismutase mimetic, demonstrates that H2O2 might be generated endogenously from superoxide. The toxicity of cisplatin and the development of cisplatin resistance are major obstacles in treatment of ovarian cancer. We found that addition of EGCG amplified the toxicity of cisplatin. EGCG increased cisplatin potency by three to six-fold in SKOV3, CAOV3, and C200 cells, the latter being a cell line induced to have several hundred fold resistant to cisplatin above the parental line. Our findings suggest that EGCG may accentuate oxidative stress to inhibit growth of ovarian cancer cells and sensitize them to cisplatin.

Chronic depletion of glutathione (GSH) and minimal modification of LDL in vivo: its prevention by glutathione mono ester (GME) therapy

A decline in reduced glutathione (GSH) level is associated with aging and free radical mediated diseases. The objective of this study was to determine whether the chronic depletion of extra cellular GSH causes oxidative damage to the circulating macromolecules such as lipoproteins. Decreased concentrations of plasma glutathione, vitamin E and ascorbic acid were recorded in the rats treated with buthionine sulfoximine (BSO), a selective GSH inhibitor. In LDL isolated from BSO-treated animals, the concentration of malondialdehyde (MDA) and conjugated dienes were significantly increased (P<0.01), whereas the levels of vitamin E were decreased (P<0.01). The analysis of total and LDL cholesterol revealed significant changes between the control and experimental groups. Of interest, altered concentrations of lyso-phosphatidyl choline (Lyso-PC) and phosphatidyl choline (PC) were recorded from the BSO mediated minimally modified LDL. A negative correlation between LDL-BDC/MDA and its antioxidant capacity was noted. Upon in vitro oxidation with CuSO(4), the electrophoretic behavior of purified LDL-apoprotein-B on agarose gel showed an increased mobility in BSO-treated rats, indicative of in vivo modification of LDL to become susceptible for in vitro oxidation. The increased mobility of LDL (after in vitro oxidation) isolated from the BSO-treated animals correlates with a decrease in its amino groups, as determined by the trinitrobenzene sulfonic acid (TNBS) reactants. However, the mobility of LDL molecule was not altered due to BSO treatment in vivo. Interestingly, the minimal modification on LDL does not lead to any vascular damage in the dorsal aorta of the rats injected with BSO. The administration of glutathione monoester (GME), at a dose of 5 mmol/kg body weight, twice a day, for 30 days, to animals treated with l-buthionine-SR-sulfoximine (BSO, 4 mmol/kg body weight, twice a day, for 30 days) normalized the antioxidant status and prevented the minimal modifications on LDL. Thus, increasing the cellular GSH levels may trigger beneficial effects against oxidative stress.

Cisplatin, doxorubicin and paclitaxel induce mdr1 gene transcription in ovarian cancer cell lines

The clinical observation of the multidrug resistance (MDR) phenotype is often associated with overexpression of the mdrl gene, in particular with respect to ovarian cancer. However, until now the mdrl-inducing potential of commonly used antineoplastics has been only incompletely explored. We performed short-term cultures of six ovarian cancer cell lines (MZOV4, EF027, SKOV3, OAW42, OTN14, MZOV20) exposed to either blank medium or cisplatin, doxorubicin or paclitaxel at concentrations related to the clinically achievable plasma peak concentration. A highly specific quantitative real-time RT-PCR was used to detect the Mdr1 transcripts. Mdrl mRNA contents were calibrated in relation to coamplified GAPDH mRNA. Mdrl mRNA was detectable in each cell line. In 13 out of 18 assays (72%) the specific anticancer drug being tested induced mdr1 transcription. No decrease in mdr1 mRNA concentration was observed. Our data suggest that mdr1 induction by antineoplastics is one of the reasons for failure of ovarian cancer therapy but may vary individually.

A phase II study of the MDR inhibitor biricodar (INCEL, VX-710) and paclitaxel in women with advanced ovarian cancer refractory to paclitaxel therapy

PURPOSE

Incel (biricodar, VX-710) restores drug sensitivity to P-glycoprotein (MDR1) and multidrug-resistance-associated protein (MRP1) expressing cells. This phase II study evaluated the safety/tolerability, pharmacokinetics, and efficacy of VX-710 plus paclitaxel in women with advanced ovarian cancer refractory to prior paclitaxel therapy.

EXPERIMENTAL DESIGN

Eligible patients had paclitaxel-refractory disease defined as progressive disease after a minimum of two cycles of paclitaxel (weekly or 3-week schedule) or relapsed disease within 4 months of prior paclitaxel therapy. Patients received 80 mg/m(2) paclitaxel over 3 h starting 4 h after initiation of a 24-h continuous intravenous infusion of 120 mg/m(2)/h VX-710. Cycles were repeated every 3 weeks.

RESULTS

Fifty patients received treatment and 45 were evaluable for response. VX-710 + paclitaxel therapy was generally well tolerated. Myelosuppression was the principal toxicity, with a median Cycle 1 nadir absolute neutrophil count of 0.27 x 10(9) cells/L and a 47% overall incidence of Grade 4 neutropenia. Mild to moderate peripheral neuritis or neuropathy was the primary nonhematologic toxicity, affecting 62% of patients. Other nonhematologic toxicities were generally mild to moderate and reversible. Paclitaxel area under the concentration-versus-time curve (AUC) (16 +/- 5.3 microg x h/mL) during the first treatment cycle was comparable to standard 175 mg/m(2) paclitaxel administered over 3 h. Of the 3 patients who achieved partial responses, 2 had progressed during prior paclitaxel therapy. Twelve patients maintained stable disease and 14/45 (31%) of patients had CA-125 reductions of 50-90% for up to 24 weeks. The median time-to-disease progression was 10 weeks for the intent-to-treat population and 20.7 weeks for the CA-125 responders.

CONCLUSIONS

The results suggest that VX-710 with paclitaxel has modest activity in paclitaxel-resistant ovarian cancer. Further research is warranted in less heavily treated patients.

The effect of glutathione monoester (GME) on glutathione (GSH) depleted rat liver

The effect of glutathione monoester (GME) on buthionine sulfoximine (BSO) mediated glutathione (GSH) depletion in rats was studied to understand the defensive role of intraperitoneally supplemented GSH. Administration of glutathione mono ester (GME) (at a dose of 5 mmole/kg body weight, twice a day for 30 days) significantly prevented the buthionine sulfoximine (at a dose of 4 mmole/kg body weight, twice a day for 30 days) induced alterations. This study suggests that glutathione mono ester is hepatoprotective and plays an important role in preventing lipid peroxidation, which leads to cytotoxic effects.

Phase II study of paclitaxel and valspodar (PSC 833) in refractory ovarian carcinoma: a gynecologic oncology group study

PURPOSE

A phase II study was conducted to determine the efficacy of paclitaxel and valspodar (PSC 833) in patients with advanced epithelial ovarian cancer. Valspodar, a nonimmunosuppressive cyclosporine D analogue that reverses P-glycoprotein-mediated multidrug resistance, in combination with paclitaxel might be active in paclitaxel-resistant and refractory ovarian cancer.

PATIENTS AND METHODS

Patients received valspodar 5 mg/kg orally qid x 12 doses. Paclitaxel (70 mg/m(2) intravenously for 3 hours) was administered on day 2, 2 hours after the fifth or sixth dose of valspodar. This treatment was repeated every 21 days. One blood sample was collected before the sixth dose of valspodar for the first three cycles to evaluate valspodar trough concentration. Tumor tissue was obtained from patients for immunohistochemical staining of P-glycoprotein.

RESULTS

Of 60 patients entered, 58 were assessable for response. There were five partial responses (8.6%; 90% confidence interval [CI], 3.8 to 20.0; median duration of response, 5.0 months [range, 1.9 to 10.5 months]). Median progression-free survival was 1.5 months (90% CI, 1.4 to 2.4). Grade 3 or 4 toxicities observed were neutropenia, anemia, nausea and vomiting, peripheral neuropathy, and cerebellar ataxia. The trough concentrations of valspodar were > or = 1,000 ng/mL in all but two of 40 patients in the first cycle. Immunohistochemical staining for P-glycoprotein was positive for one of two responding patients.

CONCLUSION

Valspodar in combination with paclitaxel has limited activity in patients with paclitaxel-resistant ovarian carcinoma. An international randomized clinical trial of paclitaxel and carboplatin with or without valspodar as first-line therapy in advanced ovarian cancer is underway.