In vitro search for synergy and antagonism: evaluation of docetaxel combinations in breast cancer cell lines

Targeting cuproplasia and cuproptosis in cancer

Copper, an essential trace element that exists in oxidized and reduced forms, has pivotal roles in a variety of biological processes, including redox chemistry, enzymatic reactions, mitochondrial respiration, iron metabolism, autophagy and immune modulation; maintaining copper homeostasis is crucial as both its deficiency and its excess are deleterious. Dysregulated copper metabolism has a dual role in tumorigenesis and cancer therapy. Specifically, cuproplasia describes copper-dependent cell growth and proliferation, including hyperplasia, metaplasia and neoplasia, whereas cuproptosis refers to a mitochondrial pathway of cell death triggered by excessive copper exposure and subsequent proteotoxic stress (although complex interactions between cuproptosis and other cell death mechanisms, such as ferroptosis, are likely and remain enigmatic). In this Review, we summarize advances in our understanding of copper metabolism, the molecular machineries underlying cuproplasia and cuproptosis, and their potential targeting for cancer therapy. These new findings advance the rapidly expanding field of translational cancer research focused on metal compounds.

Disulfiram in glioma: Literature review of drug repurposing

Gliomas are the most common malignant brain tumors. High-grade gliomas, represented by glioblastoma multiforme (GBM), have a poor prognosis and are prone to recurrence. The standard treatment strategy is tumor removal combined with radiotherapy and chemotherapy, such as temozolomide (TMZ). However, even after conventional treatment, they still have a high recurrence rate, resulting in an increasing demand for effective anti-glioma drugs. Drug repurposing is a method of reusing drugs that have already been widely approved for new indication. It has the advantages of reduced research cost, safety, and increased efficiency. Disulfiram (DSF), originally approved for alcohol dependence, has been repurposed for adjuvant chemotherapy in glioma. This article reviews the drug repurposing method and the progress of research on disulfiram reuse for glioma treatment.

Potential cancer treatment effects of brusatol or eriodictyol combined with 5-fluorouracil (5-FU) in colorectal cancer cell

Colorectal cancer is among the most frequently diagnosed cancers in patients today. In the treatment of this disease, combination or multicomponent therapy has been identified as a potential method to improve patient response and delay side effects. The aim of this study was to determine the effects on cell viability of commercial Bru and Erio used together with the anticancer drug 5-FU in the human colorectal cancer (CRC) cell line (HT-29 cell line) for the first time, as far as can be determined from available literature at this time. Additionally, the research seeks to study any potential effects on apoptosis. For this purpose, the effects of independent and combined treatments of the aforementioned agents on cell viability were investigated through the MTT experiment. Apoptotic effects were determined by Annexin V/PI and real-time PCR methods. In addition, a cell cycle analysis was used to determine the distribution of cells in the cycle. Data from experiments for 48 h showed that Bru, alone or in combination with 5-FU, is capable of causing an increase in the percentage of apoptotic cells in HT-29 cells compared to those of Erio alone or in combination with 5-FU. A significant increase in the level of bax and caspase-3 apoptotic genes was also detected in combinations of IC₅₀ concentrations of Bru and 5-FU. These findings suggest that unlike Erio, Bru alone or in combination with 5-FU may be useful for increasing the effects of 5-FU used in the treatment of CRC and to provide data on alternative treatment approaches.

Surface-engineered nanostructured lipid carrier systems for synergistic combination oncotherapy of non-small cell lung cancer

Nanoparticle-aided combination chemotherapy offers several advantages like ratiometric drug delivery, dose reduction, multi-targeted therapy, synergism, and overcoming multi-drug resistance. The current research was instigated to facilitate targeted and ratiometric co-delivery of docetaxel (DT) and curcumin (CR) through the development of folate (FA)-appended nanostructured lipid carriers (NLCs), i.e., FA-DTCR-NLCs to lung cancer cells. The FA-DTCR-NLCs were formulated by employing a scaleable and solvent-free high-pressure homogenization approach. The FA-DTCR-NLCs were evaluated for in vitro and in vivo characteristics using suitable analytical and statistical techniques. The FA-DTCR-NLCs demonstrated physicochemical properties and particokinetics suitable for targeted, ratiometric co-delivery of the anticancer agents. This was further affirmed by significantly better in vivo relative bioavailability of DT (24.85 fold) with FA-DTCR-NLCs as compared with Taxotere^® (p < 0.05) and cell line studies. A significant tumor regression was observed from the results of tumor staging in a murine model of lung carcinoma (p < 0.05). Immunostaining of the tumor sections with tumor differentiation biomarkers suggested considerably higher apoptotic, anti-proliferative, anti-angiogenic, and anti-metastatic potential of FA-DTCR-NLCs compared with Taxotere^®. In vivo toxicity assessment of the FA-DTCR-NLCs demonstrated a noteworthy reduction in DT associated side effects. The in vitro and in vivo pre-clinical findings prove the therapeutic and safety pre-eminence of FA-DTCR-NLCs for the treatment of NSCLC.

Co-encapsulation of thymoquinone with docetaxel enhances the encapsulation efficiency into PEGylated liposomes and the chemosensitivity of MCF7 breast cancer cells to docetaxel

Combinatorial therapeutic strategies to eradicate tumors can be superior to a single therapeutic modality. Docetaxel (DT) has been approved for the treatment of local or metastasized breast cancer alone or in combination with other chemotherapeutic agents. Thymoquinone (TQ) originated from the seeds of Nigella Sativa plant has been reported to possess in vitro and in vivo antitumor activity against variety of tumors. In the current study, we have investigated the synergistic anticancer efficacy of a novel combination of DT and TQ on MCF7 breast cancer cell line using MTT cell viability assay. Moreover, this study describes for the first time the co-encapsulation of DT and TQ into PEGylated liposomes. The results showed that the combination of DT and TQ resulted in significant synergistic cytotoxicity compared to DT and TQ alone. Moreover, DT and TQ have been successfully co-encapsulated into PEGylated liposomes with higher encapsulation efficiency compared to DT and TQ alone. In conclusion, DT and TQ combination poses a synergistic effect and may aid in decreasing the required doses of DT. Also, the co-encapsulation of DT and TQ into PEGylated liposomes can provide a promising DT and TQ delivery system into cancer cells.

Synergistic Chemotherapy Drug Response Is a Genetic Trait in Lymphoblastoid Cell Lines

Lymphoblastoid cell lines (LCLs) are a highly successful model for evaluating the genetic etiology of cancer drug response, but applications using this model have typically focused on single drugs. Combination therapy is quite common in modern chemotherapy treatment since drugs often work synergistically, and it is an important progression in the use of the LCL model to expand work for drug combinations. In the present work, we demonstrate that synergy occurs and can be quantified in LCLs across a range of clinically important drug combinations. Lymphoblastoid cell lines have been commonly employed in association mapping in cancer pharmacogenomics, but it is so far untested as to whether synergistic effects have a genetic etiology. Here we use cell lines from extended pedigrees to demonstrate that there is a substantial heritable component to synergistic drug response. Additionally, we perform linkage mapping in these pedigrees to identify putative regions linked to this important phenotype. This demonstration supports the premise of expanding the use of the LCL model to perform association mapping for combination therapies.

Synergistic antitumor activity of camptothecin-doxorubicin combinations and their conjugates with hyaluronic acid

Combinations of topoisomerase inhibitors I and II have been found to synergistically inhibit cancer cell growth in vitro, yet clinical studies of these types of combinations have not progressed beyond phase II trials. The results of clinical combinations of topoisomerase (top) I and II inhibitors typically fall within one of two categories: little to no improvement in therapeutic efficacy, or augmented toxicity compared to the single drug counterparts. Hence, despite the promising activity of top I and II inhibitor combinations in vitro, their clinical applicability has not been realized. Here, we report the use of polymer-drug conjugates as a means to co-deliver synergistic doses of top I and II inhibitors camptothecin (CPT) and doxorubicin (DOX) to tumors in vivo in a 4T1 breast cancer model. At specific molar ratios, DOX and CPT were found to be among the most synergistic combinations reported to date, with combination indices between 0.01 and 0.1. The identified optimal ratios were controllably conjugated to hyaluronic acid, and elicited significant tumor reduction of murine 4T1 breast cancer model when administered intravenously. This study elucidates a method to identify synergistic drug combinations and translate them to in vivo by preserving the synergistic ratio via conjugation to a carrier polymer, thus opening a promising approach to translate drug combinations to clinically viable treatment regimens.

Inference of synergy/antagonism between anticancer drugs from the pooled analysis of clinical trials

BACKGROUND

Drug interactions can have a significant impact on the response to combinatorial therapy for anticancer treatment. In some instances these interactions can be anticipated based on pre-clinical models. However, the anticipation of drug interactions in the clinical context is in general a challenging task.

METHODS

Here we propose the pooled analysis of clinical trials as a mean to investigate drug interactions in anticancer therapy. To this end we collected 1,163 Phase II clinical trials with response data on over 53,745 subjects.

RESULTS

We provide statistical definitions of drugs resulting in clinical synergy and antagonism and identify drug combinations in each group. We also quantify the possibility of inferring interactions between three or more drugs from parameters characterizing the action of single and two-drugs combinations.

CONCLUSIONS

Our analysis provides a statistical methodology to track the performance of drug combinations in anticancer therapy and to quantify drug interactions in the clinical context.

A conceptually new treatment approach for relapsed glioblastoma: coordinated undermining of survival paths with nine repurposed drugs (CUSP9) by the International Initiative for Accelerated Improvement of Glioblastoma Care

To improve prognosis in recurrent glioblastoma we developed a treatment protocol based on a combination of drugs not traditionally thought of as cytotoxic chemotherapy agents but that have a robust history of being well-tolerated and are already marketed and used for other non-cancer indications. Focus was on adding drugs which met these criteria: a) were pharmacologically well characterized, b) had low likelihood of adding to patient side effect burden, c) had evidence for interfering with a recognized, well-characterized growth promoting element of glioblastoma, and d) were coordinated, as an ensemble had reasonable likelihood of concerted activity against key biological features of glioblastoma growth. We found nine drugs meeting these criteria and propose adding them to continuous low dose temozolomide, a currently accepted treatment for relapsed glioblastoma, in patients with recurrent disease after primary treatment with the Stupp Protocol. The nine adjuvant drug regimen, Coordinated Undermining of Survival Paths, CUSP9, then are aprepitant, artesunate, auranofin, captopril, copper gluconate, disulfiram, ketoconazole, nelfinavir, sertraline, to be added to continuous low dose temozolomide. We discuss each drug in turn and the specific rationale for use- how each drug is expected to retard glioblastoma growth and undermine glioblastoma's compensatory mechanisms engaged during temozolomide treatment. The risks of pharmacological interactions and why we believe this drug mix will increase both quality of life and overall survival are reviewed.

Disulfiram, a drug widely used to control alcoholism, suppresses the self-renewal of glioblastoma and over-rides resistance to temozolomide

Glioblastomas (GBM) are associated with high rates of relapse. These brain tumors are often resistant to chemotherapies like temozolomide (TMZ) and there are very few treatment options available to patients. We recently reported that polo-like kinase-1 (PLK1) is associated with the proliferative subtype of GBM; which has the worst prognosis. In this study, we addressed the potential of repurposing disulfiram (DSF), a drug widely used to control alcoholism for the past six decades. DSF has good safety profiles and penetrates the blood-brain barrier. Here we report that DSF inhibited the growth of TMZ resistant GBM cells, (IC90=100 nM), but did not affect normal human astrocytes. At similar DSF concentrations, self-renewal was blocked by ~100% using neurosphere growth assays. Likewise the drug completely inhibited the self-renewal of the BT74 and GBM4 primary cell lines. Additionally, DSF suppressed growth and self-renewal of primary cells from two GBM tumors. These cells were resistant to TMZ, had unmethylated MGMT, and expressed high levels of PLK1. Consistent with its role in suppressing GBM growth, DSF inhibited the expression of PLK1 in GBM cells. Likewise, PLK1 inhibition with siRNA, or small molecules (BI-2536 or BI-6727) blocked growth of TMZ resistant cells. Our studies suggest that DSF has the potential to be repurposed for treatment of refractory GBM.

Aldehyde dehydrogenase and HSP90 co-localize in human glioblastoma biopsy cells

The concept of a stem cell subpopulation as understood from normal epithelial tissue or bone marrow function has been extended to our understanding of cancer tissue and is now the target of treatment efforts specifically directed to this subpopulation. In glioblastoma, as well as in other cancers, increased expression of aldehyde dehydrogenase (ALDH) has been found localized within a minority sub-population of tumor cells which demonstrate stem cell properties. A separate body of research associated increased expression of heat-shock protein-90 (HSP90) with stem cell attributes. We present here results from our initial immunohistochemistry study of human glioblastoma biopsy tissue where both ALDH and HSP90 tended to be co-expressed in high amounts in the same minority of cells. Since 12% of all cells in the six biopsies studied were ALDH positive and 17% were HSP90 positive, by chance alone 2% would have been expected to be positive for both. In fact 7% of all cells simultaneously expressed both markers-a significant difference (p = 0.037). That two previously identified proteins associated with stem cell attributes tend to be co-expressed in the same individual glioblastoma cells might have clinical utility. Disulfiram, used to treat alcoholism for half-a century now, is a potent ALDH inhibitor and the old anti-viral drug ritonavir inhibits HSP90. These should be explored for the potential to retard aspects of glioblastoma stem cells' function subserved by ALDH and HSP90.

Dexrazoxane ameliorates doxorubicin-induced injury in mouse ovarian cells

Doxorubicin (DXR) is a frontline chemotherapy agent implicated in unintended ovarian failure in female cancer survivors. The fertility preservation techniques currently available for cancer patients are often time and cost prohibitive and do not necessarily preserve endocrine function. There are no drug-based ovary protection therapies clinically available. This study provides the first investigation using dexrazoxane (Dexra) to limit DXR insult in ovarian tissue. In KK-15 granulosa cells, a 3-h DXR treatment increased double-strand (ds) DNA breaks 40%-50%, as quantified by the neutral comet assay, and dose-dependent cytotoxicity. Dexra exhibited low toxicity in KK-15 cells, inducing no DNA damage and less than 20% cell loss. Cotreating KK-15 cells with Dexra prevented acute DXR-induced dsDNA damage. Similarly, Dexra attenuated the DXR-induced 40%-65% increase in dsDNA breaks in primary murine granulosa cells and cells from in vitro cultured murine ovaries. DXR can cause DNA damage either through a topoisomerase II-mediated pathway, based on DXR intercalation into DNA, or through oxidative stress. Cotreating KK-15 cells with 2 μM Dexra was sufficient to prevent DXR-induced, but not H(2)O(2)-induced, DNA damage. These data indicated the protective effects are likely due to Dexra's inhibition of topoisomerase II catalytic activity. This putative protective agent attenuated downstream cellular responses to DXR, preventing H2AFX activation in KK-15 cells and increasing viability as demonstrated by increasing the DXR lethal dose in KK-15 cells 5- to 8-fold (LD(20)) and primary murine granulosa cells 1.5- to 2-fold (LD(50)). These data demonstrate Dexra protects ovarian cells from DXR insult and suggest that it is a promising tool to limit DXR ovarian toxicity in vivo.

Enhanced survival in locoregionally confined anaplastic thyroid carcinoma: a single-institution experience using aggressive multimodal therapy

BACKGROUND

Historical outcomes in anaplastic thyroid carcinoma (ATC) are poor, with a median survival of only 5 months and <20% of patients surviving 1 year from diagnosis. We hypothesized that survival in newly diagnosed patients with stages IVA and IVB locoregionally confined ATC might be improved by utilizing an aggressive therapeutic approach, prioritizing both the eradication of disease in the neck and preemptive treatment of occult metastatic disease.

METHODS

Between January 1, 2003, and December 31, 2007, 25 new ATC patients were evaluated at our institution. Of these 25 patients, 10 (40%) had metastatic disease at diagnosis and therefore underwent palliative treatment, whereas 5 (20%) had regionally confined disease and desired treatment at their local medical facilities. The remaining 10 consecutive patients (40%) had regionally confined ATC and elected aggressive therapy combining individualized surgery (where feasible), intensity-modulated radiation therapy (IMRT), and radiosensitizing + adjuvant chemotherapy intending four cycles of docetaxel + doxorubicin. Outcomes were assessed on an intention to treat basis.

RESULTS

There were no deaths from therapy, but hospitalization was required in two patients (20%) because of treatment-related adverse events. Five patients (50%) are alive and cancer-free, all having been followed >32 months (range: 32-89 months; median: 44 months) with a median overall Kaplan-Meier survival of 60 months. Overall survival at 1 and 2 years was 70% and 60%, respectively, compared to <20% historical survival at 1 year in analogous patients previously treated with surgery and conventional postoperative radiation at our and other institutions.

CONCLUSIONS

Although based upon a small series of consecutively treated patients, an aggressive approach combining IMRT and radiosensitizing plus adjuvant chemotherapy appears to improve outcomes, including survival in stages IVA and IVB regionally confined ATC, but remains of uncertain benefit in patients with stage IVC (metastatic) disease. Also uncertain is the optimal chemotherapy regimen to use in conjunction with IMRT. Further multicenter randomized trials are required to define optimal therapy in this rare but deadly cancer.

Synergistic interactions between peloruside A and other microtubule-stabilizing and destabilizing agents in cultured human ovarian carcinoma cells and murine T cells

PURPOSE

Microtubule-stabilizing agents are an important class of anticancer compounds. Peloruside A and laulimalide bind to a different site on the microtubule to taxoid site drugs such as paclitaxel (Taxol(®)), docetaxel (Taxotere(®)), ixabepilone (Ixempra(®)), the epothilones, and discodermolide. The purpose of this study was to examine the synergistic interactions of these drugs when given in combination in relation to the differences in their binding sites on the microtubule.

METHODS

Human ovarian carcinoma cells (1A9 cells) and murine T cells were treated with different combinations of microtubule-stabilizing or destabilizing agents. The compounds were given individually and in combination, and the antiproliferative activity was assessed to calculate a combination index (CI) from the equation: CI = D(1)/Dx(1) + D(2)/Dx(2) in which D(1) and D(2) are the concentrations of drug 1 and drug 2 that when given together give the same response as drug 1 and 2 alone (Dx(1) and Dx(2)). Thus, a CI value of less than 1.0 indicates a synergistic effect between the two drugs in which the response to the two drugs given together is greater than the additive response of the two drugs if given on their own.

RESULTS

As anticipated from previous in vitro studies, peloruside A and laulimalide did not synergize with each other. They also failed to synergize with the microtubule-destabilizing agents vinblastine and 2-methoxyestradiol. Peloruside A and laulimalide did, however, synergize with the epothilones, as had been previously shown, but not with docetaxel or discodermolide.

CONCLUSIONS

Combining two microtubule-targeting agents with different binding sites does not guarantee a synergistic interaction in cells, and additional factors are likely to be involved. This study highlights the importance of preclinical testing of actual combinations of drugs before proceeding into clinical trials.

Phase II study of vinorelbine and docetaxel in the treatment of advanced non-small-cell lung cancer as frontline and second-line therapy

OBJECTIVES

Combination chemotherapy with third-generation, nonplatinum agents (ie, gemcitabine, vinorelbine, taxanes, or camptothecins) represents a well-tolerated frontline treatment option for metastatic non-small-cell lung cancer and might play a role as salvage therapy as well. The aim of this phase 2 study was to investigate the use of docetaxel and vinorelbine in the frontline and second-line setting in patients with incurable non-small-cell lung cancer.

PATIENTS AND METHODS

Seventy-eight patients (42 untreated, 36 previously treated) were administered vinorelbine (20 mg/m) on days 1 and 8 and docetaxel (75 mg/m for untreated patients; 60 mg/m for previously treated patients for cycle 1, increased to 75 mg/m for the subsequent cycles in the absence of grade 3 fever/neutropenia) on day 8, repeated every 21 days, with routine filgrastim support.

RESULTS

The most common grade 3 to 4 nonhematologic toxicities were diarrhea, dyspnea, fatigue, and nausea/vomiting (5% each). Grade 3 to 4 granulocytopenia occurred in 55% of the patients, however only 5% experienced febrile neutropenia. Response rates were 13% in the chemotherapy-naive cohort and 9% in previously treated patients. Median time to progression was 2.9 and 3.0 months and median overall survival was 15.0 and 6.2 months, for the frontline and second-line patients, respectively.

CONCLUSIONS

Compared with historical controls, in the first-line setting, the combination of docetaxel and vinorelbine did not demonstrate increased efficacy advantages over platinum- or other nonplatinum-based doublets. In the second-line setting, single agent chemotherapy is as effective as, and less toxic than the docetaxel-vinorelbine combination, and the former remains the cytotoxic treatment of choice.

The vitamin A family can significantly decrease the expression of ERbeta of ERs positive breast cancer cells in the presence or absence of ER ligands and paclitaxel

Taxanes have high activity against breast cancer cells either as the single agent or in combination with other anticancer compounds. The aim of the study was to determine the effects of vitamin A compounds on the cytotoxic action of paclitaxel and on the expression of ERs in the MCF-7 breast cancer cells. Retinol and beta-carotene, but not retinoids, added to the culture exerted an effect on paclitaxel activity. However, only beta-carotene significantly reduced the percentage of proliferating cells (40.36% +/- 5.64, p < 0.01). We observed that vitamin A and its derivatives combined with paclitaxel and estradiol decreased the percentage of proliferating cells, but only in comparison to estradiol group, whereas retinol and lycopene administered together with paclitaxel and tamoxifen decrease significantly the percentage of proliferatin cells (36.85% +/- 4.71, p < 0.0001 and 37.22% +/- 1.59, p < 0.0001 respectively, compared with paclitaxel group). We have shown that paclitaxel increases the expression of ERalpha and ERbeta mRNA in MCF-7 line. The strongest effect of transcription inhibition ERalpha (2.5 times) and especially ERbeta (10 times) was observed after addition of 9-cis retinoic acid and paclitaxel. This data suggests a synergistic effect of the compounds on ERbeta down-regulation. Our results support the use of retinoid is treatment of ER positive breast cancer patients.

Salvage chemotherapy with docetaxel and epirubicin for advanced/metastatic gastric cancer

BACKGROUND

We conducted a phase II study to assess the efficacy and tolerability of docetaxel and epirubicin as salvage chemotherapy in advanced/metastatic gastric cancer patients with documented progression after 5-fluorouracil/platinum-based combination chemotherapy.

METHODS

Docetaxel 75 mg/m(2) and epirubicin 50 mg/m(2) were administered on days 1 and 2, respectively, every 3 weeks. Treatment continued until progression of disease or until a life-threatening adverse event occurred. The primary objectives of this study were to evaluate the safety profile and response rate to this treatment regimen.

RESULTS

Thirty-four patients were enrolled in the study. Twenty-six patients had locally advanced or metastatic disease at the time of diagnosis, and 8 patients had recurrent disease after surgical resection of the primary tumor. A total of 157 chemotherapy cycles were administered. Seven (21.8%) patients had a partial response and 12 (37.5%) patients had stable disease. The median time to progression and overall survival were 4.1 and 13.4 months, respectively. Grade III/IV hematologic toxicities included neutropenia in 16 patients (47%) and febrile neutropenia in 8 patients (24%). Nonhematologic toxicities were rare.

CONCLUSION

A combination of chemotherapy with docetaxel and epirubicin showed moderate activity as salvage treatment in advanced/metastatic gastric cancer, especially in patients who had responded to prior chemotherapy.

Peloruside A synergizes with other microtubule stabilizing agents in cultured cancer cell lines

The microtubule stabilizing agent peloruside A binds to a unique site on the tubulin alpha,beta-heterodimer compared to taxoid site drugs such as paclitaxel (Taxol), docetaxel (Taxotere), epothilone A, and discodermolide. Because the binding sites differ, peloruside A may be able to synergize with these taxoid site drugs when added in combination to cultured cells. Ovarian carcinoma cells (1A9) and myeloid leukemic cells (HL-60) were treated with different concentrations of peloruside A and taxoid site drugs, both compounds given singly and in combination in the nanomolar range, and the antiproliferative activity, G2/M blocking potency, and microtubule stabilizing activity of the treatments assessed. Cell proliferation was monitored using the MTT cell proliferation assay, cell cycle block was determined by flow cytometry, and stabilization of the tubulin polymer was assessed by Western blotting for beta-tubulin distributions in supernatant and pellet fractions of cell lysates. A combination index (CI) was calculated from the equation CI = D1/Dx1 + D2/Dx2 in which D1 and D2 are the concentrations of drug 1 and drug 2 that in combination give the same response as drug 1 alone (Dx1) or drug 2 alone (Dx2). A CI of less than 1 indicates synergy, equal to 1, additivity, and greater than 1, antagonism. Confidence intervals for each CI value were obtained using a bootstrapping procedure. In cell proliferation assays, statistically significant synergy was found between peloruside A and paclitaxel and epothilone A. Combinations of these two taxoid site drugs, however, also showed synergy in their effects on cell proliferation. These results confirm that peloruside A, when added in combination with other microtubule stabilizing agents, acts synergistically to enhance the antimitotic action of the drugs, but also highlight the complexity of drug interactions in intact cells.

A Phase I dose-finding study using an innovative sequential biweekly schedule of irinotecan followed 24 hours later by capecitabine

BACKGROUND

Irinotecan and capecitabine have a broad spectrum of activity in human malignancy and are synergistic in an animal model when irinotecan precedes capecitabine.

PATIENTS AND METHODS

A Phase I design of the combination of irinotecan IV Day 1 with capecitabine on Days 2-8 every 2 weeks was evaluated in 27 adult patients with solid tumors. Two sequential schema were used: Arm A fixed the dose of irinotecan at 100 mg/m(2) and escalated capecitabine in cohorts, and arm B fixed the dose of capecitabine at 750 mg/m(2) PO BID and escalated the dosage of irinotecan.

RESULTS

Neutropenia was dose limiting with nausea and diarrhea as the most common nonhematological toxicities. Significant interpatient variation in toxicity occurred despite uniform dosing. No Grade IV toxicities were encountered. Grade III toxicity occurred in first cycle in 15 percent (3/20) patients in arm A and 29 percent (2/7) of patients in arm B. All toxicities were reversible. Repetitive dosing was feasible with prolonged disease stabilization in 8 patients.

CONCLUSIONS

The suggested Phase II dose of this combination and schedule is irinotecan 100 mg/m(2) and capecitabine 1000 mg/m(2) BID. Some patients tolerated a capecitabine dose as high as 1250 mg/m(2) BID.

Fluvastatin enhancement of trastuzumab and classical cytotoxic agents in defined breast cancer cell lines in vitro

The combination of anticancer drugs used in the clinic has been based upon empiricism, and the potential permutations of currently available drugs overwhelm the clinical trials system. Recently, investigators have suggested that the combination of a blockade of vital signal transduction pathways in combination with more standard therapy might enhance anticancer effect. Using a panel of breast cancer cell lines and isobologram median effect analysis, a method of determining synergism or antagonism of drugs, we have investigated in vitro potentially clinically useful combinations of agents with the human cell lines MCF7/wt, MCF7/adr, BT474, and SK-BR-3 grown in log phase. Results were confirmed by curve shift analysis. Cells were exposed to the agent(s) for 72 h and then analyzed for cytotoxicity using a MTT (3-(4,5-dimethylthiazolyl-2)-2,5-diphenyl-tetrazolium bromide) assay. Fluvastatin, an inhibitor of prenylation with excellent tolerability in man, was chosen to disrupt signal transduction pathways and thus potentially enhance the effect of more traditional anticancer agents. Anticancer agents tested were cytotoxics used in the treatment of breast cancer, trastuzumab, and rapamycin as an inhibitor of the AKT pathway. Fluvastatin combined with trastuzumab demonstrates global synergy of cytotoxic effect that is confirmed by apoptosis assay. These effects could only be partially reversed by adding farnesol or geranylgeraniol to restore prenylation. Epirubicin is also synergistic with fluvastatin in three of the four cell lines. Rapamycin, an inhibitor of MTOR, was synergistic with fluvastatin in two of the four cell lines and antagonistic in two other cell lines. The combination of fluvastatin or another inhibitor of prenylation and trastuzumab may be attractive for clinical development as the effect of trastuzumab in Her2/neu positive breast tumors is incomplete as a single agent.

Identification of potentially useful combinations of epidermal growth factor receptor tyrosine kinase antagonists with conventional cytotoxic agents using median effect analysis

Targeted therapy for breast carcinoma has achieved a major advance with the use of trastuzumab in Her2/neu-positive tumors. The epidermal growth factor receptor superfamily thus becomes an attractive target for therapeutic agents. As the epidermal growth factor receptor tyrosine kinase family has a conformational binding site, which allows small molecules to interfere with its function, we have explored the effects of a dual kinase (epidermal growth factor receptor-1 and epidermal growth factor receptor-2) inhibitor (GW282974X) with a variety of cytotoxic agents looking for synergistic effects in vitro. Using a median effect model in four breast cancer cell lines in vitro, cytotoxic agents commonly used in treatment of human malignant disease were combined with trastuzumab or one of two epidermal growth factor receptor tyrosine kinase inhibitors in a 72-h culture and then analyzed for cytotoxic effect by 3-[26]-2,5-diphenyl-tetrazolium bromide assay. Combination index values within one standard deviation of unity were considered additive, less than unity as synergistic and more than unity as antagonistic. Synergistic results were confirmed by curve shift analysis and by an enzyme-linked immunosorbent assay measuring apoptosis by cytoplasmic histone-associated DNA fragments. Quantitative real-time polymerase chain reaction analysis was used to measure the expression of three of the critical enzymes in 5'-deoxy-5-fluorouridine metabolism and activity: thymidine phosphorylase, dihydropyrimidine dehydrogenase and thymidine synthase. 5'-Deoxy-5-fluorouridine with GW282974X demonstrated global synergy, both in high and low expressing epidermal growth factor receptor breast cancer cell lines. These results were confirmed by apoptosis assay and cell counts. RNA quantification following treatment with the dual kinase inhibitor suggested reduction in thymidine synthase levels to be a potential mechanism of synergy. The triplet of trastuzumab, GW282974X and 5'-deoxy-5-fluorouridine, and the triplet of GW282974X, epirubicin and 5'-deoxy-5-fluorouridine were highly synergistic in low expression cells (MCF7/wt) and high expression cells (MCF7/adr). These experiments suggest further studies of the dual kinase inhibitor with selected cytotoxics such as 5'-deoxy-5-fluorouridine are warranted.

Regulation of survivin by retinoic acid and its role in paclitaxel-mediated cytotoxicity in MCF-7 breast cancer cells

The chemotherapeutic drug paclitaxel induces microtubular stabilization and mitotic arrest associated with increased survivin expression. Survivin is a member of the inhibitor of apoptosis (iap) family which is highly expressed in during G2/M phase where it regulates spindle formation during mitosis. It is also constitutively overexpressed in most cancer cells where it may play a role in chemotherapeutic resistance. MCF-7 breast cancer cells stably overexpressing the sense strand of survivin (MCF-7(survivin-S) cells) were more resistant to paclitaxel than cells depleted of survivin (MCF-7(survivin-AS) despite G2/M arrest in both cell lines. However, survivin overexpression did not protect cells relative to control MCF-7(pcDNA3) cells. Paclitaxel-induced cytotoxicity can be enhanced by retinoic acid and here we show that RA strongly reduces survivin expression in MCF-7 cells and prevents paclitaxel-mediated induction of survivin expression. Mitochondrial release of cytochrome c after paclitaxel alone or in combination with RA was weak, however robust Smac release was observed. While RA/paclitaxel-treated MCF-7 (pcDNA3) cultures contained condensed apoptotic nuclei, MCF-7(survivin-S) nuclei were morphologically distinct with hypercondensed disorganized chromatin and released mitochondrial AIF-1. RA also reduced paclitaxel-associated levels of cyclin B1 expression consistent with mitotic exit. MCF-7(survivin-S) cells displayed a 30% increase in >2N/<4N ploidy while there was no change in this compartment in vector control cells following RA/paclitaxel. We propose that RA sensitizes MCF-7 cells to paclitaxel at least in part through survivin downregulation and the promotion of aberrant mitotic progression resulting in apoptosis. In addition we provide biochemical and morphological data which suggest that RA-treated MCF-7(survivin-S) cells can also undergo catastrophic mitosis when exposed to paclitaxel.

Zoledronic acid (Zometa) enhances the cytotoxic effect of gemcitabine and fluvastatin: in vitro isobologram studies with conventional and nonconventional cytotoxic agents

OBJECTIVES

To identify synergistic combinations of clinically available agents with zoledronic acid which would enhance antitumor activity as measured by median effect isobologram analysis and apoptosis assays in vitro.

METHODS

The interaction of zoledronic acid as a doublet with either carboplatin, cisplatin, 5'DFUR, docetaxel, epirubicin, fluvastatin, gemcitabine, imatinib, paclitaxel, trastuzumab, or vinorelbine was studied in a 72-hour in vitro system using defined human cancer cell lines grown as a monolayer in exponential phase. Drug effect on growth was measured by a standard MTT assay. Median effect isobologram analysis was applied to the results to determine the presence of synergism, additive effects, or antagonism of drug combinations. Synergistic combinations were also assayed by a cytoplasmic histone-associated DNA fragmentation apoptosis assay to verify that the effect was not cytostatic.

RESULTS

Zoledronic acid with gemcitabine demonstrated global cytotoxic synergy across 7 of 8 cell lines. Clinically achievable concentrations of fluvastatin with zoledronic acid also demonstrated synergy in 7 of 8 cell lines. All the breast cancer cell lines were sensitive. Zoledronic acid and epirubicin were antagonistic in all 4 breast cell lines studied.

CONCLUSIONS

Combinations of zoledronic acid with either gemcitabine or fluvastatin may have a therapeutic role in treatment of bone metastasis of selected malignancies.

Late Phase II Clinical Study of Vinorelbine Monotherapy in Advanced or Recurrent Breast Cancer Previously Treated with Anthracyclines and Taxanes

BACKGROUND

At present, it is one of the most important issues for the treatment of breast cancer to develop the standard therapy for patients previously treated with anthracyclines and taxanes. With the objective of determining the usefulness of vinorelbine monotherapy in patients with advanced or recurrent breast cancer after standard therapy, we evaluated the efficacy and safety of vinorelbine in patients previously treated with anthracyclines and taxanes.

METHODS

Vinorelbine was administered at a dose level of 25 mg/m(2) intravenously on days 1 and 8 of a 3 week cycle. Patients were given three or more cycles in the absence of tumor progression. A maximum of nine cycles were administered.

RESULTS

The response rate in 50 evaluable patients was 20.0% (10 out of 50; 95% confidence interval, 10.0-33.7%). Responders plus those who had minor response (MR) or no change (NC) accounted for 58.0% [10 partial responses (PRs) + one MR + 18 NCs out of 50]. The Kaplan-Meier estimate (50% point) of time to progression (TTP) was 115.0 days. The response rate in the visceral organs was 17.3% (nine PRs out of 52). The major toxicity was myelosuppression, which was reversible and did not require discontinuation of treatment.

CONCLUSION

The results of this study show that vinorelbine monotherapy is useful in patients with advanced or recurrent breast cancer previously exposed to both anthracyclines and taxanes.

Studies of synergistic and antagonistic combinations of conventional cytotoxic agents with the multiple eicosanoid pathway modulator LY 293111

The arachidonic acid metabolic pathway is currently under active investigation as a promoter of malignancy and several molecules have been synthesized to block either the cyclooxygenase or lipoxygenase branches. LY 293111 is an oral agent known to be a leukotriene B4 antagonist, a 5-lipoxygenase inhibitor and a peroxisome proliferator-activated receptor (PPAR)-gamma agonist with cytotoxic properties in cell lines. We have studied this agent with classical chemotherapeutic agents in a 72-h culture with cell lines using median-effect analysis as a measure of antagonism or synergy. LY 293111 displays global synergy with the active metabolite of irinotecan, SN-38, in the majority of cell lines, synergistic to additive effects with gemcitabine in bladder cancer cell lines, and synergism with 5'-DFUR (the active metabolite of capecitabine) in two breast cancer and one sarcoma cell line. These effects occur at clinically attainable concentrations. The addition of a proteosome inhibitor to the LY 293111 and SN-38 combination markedly enhanced the cytotoxic effects in the sarcoma cell line. As the toxicity of LY 293111 in man is not hematological, this agent may have a role in combination therapy of selected malignancies.

Laulimalide and paclitaxel: a comparison of their effects on tubulin assembly and their synergistic action when present simultaneously

Previous work has shown that laulimalide, a sponge-derived natural product, resembles paclitaxel in enhancing tubulin assembly and in its effects on cellular microtubules. The two compounds, however, seem to have distinct binding sites on tubulin polymer. Nearly equimolar amounts of tubulin, laulimalide, and paclitaxel are recovered from microtubules formed with both drugs. In the present study, we searched for differences between laulimalide and paclitaxel in their interactions with tubulin polymer. Laulimalide was compared with paclitaxel and epothilone A, a natural product that competes with paclitaxel in binding to microtubules, for assembly properties at different temperatures and for effects of GTP and microtubule-associated proteins on assembly. Although minor differences were observed among the three drugs, their overall effects were highly similar, except that aberrant assembly products were observed more frequently with paclitaxel and that the polymers formed with laulimalide and epothilone A were more stable at 0 degrees C. The most dramatic difference observed between laulimalide and epothilone A was that only laulimalide was able to enhance assembly synergistically with paclitaxel, as would be predicted if the two drugs bound at different sites in polymer. Because stoichiometric amounts of laulimalide and paclitaxel can cause extensive tubulin assembly, maximum synergy was observed at lower temperatures under reaction conditions in which each drug alone is relatively inactive. Laulimalide-induced assembly, like paclitaxel-induced assembly, was inhibited by drugs that inhibit tubulin assembly by binding at either the colchicine- or vinblastine-binding site. When radiolabeled GTP is present in a reaction mixture with either laulimalide or paclitaxel, nucleotide hydrolysis occurs with incorporation of radiolabeled GDP into polymer.