Therapeutic response to taxol of six human tumors xenografted into nude mice

Bioequivalence of paclitaxel protein-bound particles in patients with breast cancer: determining total and unbound paclitaxel in plasma by rapid equilibrium dialysis and liquid chromatography-tandem mass spectrometry

Background and objective: Paclitaxel protein-bound particles for injectable suspension (nab-paclitaxel) showed many advantages in safety, effectiveness, and convenience. Different from conventional formulations, the bioequivalence evaluation of nab-paclitaxel formulations requires to determine the total amount of paclitaxel in plasma and the unbound paclitaxel to reflect their in vivo disposition. This study aimed to develop an analytical method to quantify the total and unbound paclitaxel in plasma and evaluate the bioequivalence of two formulations of nab-paclitaxel in patients with breast cancer. Materials and methods: An open-label, randomized, two-period crossover study was completed among 24 Chinese patients with breast cancer. The patients were randomized to receive either the test formulation on cycle 1 day 1 and after 21 days in cycle 2 day 1 by the reference formulation (Abraxane®), or vice versa. Rapid equilibrium dialysis was adopted to separate the unbound paclitaxel in human plasma. Total and unbound paclitaxel concentrations were measured by the validated liquid chromatography-tandem mass spectrometry methods over the range of 5.00-15,000 and 0.200-200 ng/mL, respectively. The bioequivalence of the test formulation to the reference formulation was assessed using the Food and Drug Administration and European Medicines Agency guidelines. Results: All the 90% confidence intervals (CIs) of the geometric mean ratios fell within the predetermined acceptance range. The 90% CIs for the area under the concentration-time curve (AUC) from 0 h to 72 h (AUC0-t), AUC from time zero to infinity (AUC0-∞), and peak plasma concentrations (Cmax) for total paclitaxel were 92.03%-98.05%, 91.98%-99.37%, and 91.37%-99.36%, respectively. The 90% CIs of AUC0-t, AUC0-∞, and Cmax for unbound paclitaxel were 86.77%-97.88%, 86.81%-97.88%, and 87.70%-98.86%, respectively. Conclusion: Bioequivalence between the two nab-paclitaxel formulations was confirmed for total and unbound paclitaxel at the studied dose regimen.

Evaluating the cytotoxic effects of the water extracts of four anticancer herbs against human malignant melanoma cells

Malignant melanoma (MM) is the most dangerous type of skin cancer, killing more than 1,100 people each year in Canada. Prognosis for late stage and recurrent MM is extremely poor due to insensitivity to chemotherapy drugs, and thus many patients seek complementary and alternative medicines. In this study, we examined four commonly used anticancer herbs in traditional Chinese medicine, Hedyotis diffusa, Scutellaria barbata, Lobelia chinensis, and Solanum nigrum, for their in vitro antitumor effects toward human MM cell line A-375. The crude water extract of S. nigrum (1 g of dry herb in 100 mL water) and its 2-fold dilution caused 52.8%±13.0% and 17.3%±2.7% cytotoxicity in A-375 cells, respectively (P<0.01). The crude water extract of H. diffusa caused 11.1%±12.4% cytotoxicity in A-375 cells with no statistical significance (P>0.05). Higher concentrated formulation might be needed for H. diffusa to exert its cytotoxic effect against A-375 cells. No cytotoxicity was observed in A-375 cells treated with crude water extract of S. barbata and L. chinensis. Further high performance liquid chromatography-tandem mass spectroscopy analysis of the herbal extracts implicated that S. nigrum and H. diffusa might have adopted the same bioactive components for their cytotoxic effects in spite of belonging to two different plant families. We also showed that the crude water extract of S. nigrum reduced intracellular reactive oxygen species generation in A-375 cells, which may lead to a cytostatic effect. Furthermore, synergistic effect was achieved when crude water extract of S. nigrum was coadministered with temozolomide, a chemotherapy drug for skin cancer.

Mathematical models of breast and ovarian cancers

Women constitute the majority of the aging United States (US) population, and this has substantial implications on cancer population patterns and management practices. Breast cancer is the most common women's malignancy, while ovarian cancer is the most fatal gynecological malignancy in the US. In this review, we focus on these subsets of women's cancers, seen more commonly in postmenopausal and elderly women. In order to systematically investigate the complexity of cancer progression and response to treatment in breast and ovarian malignancies, we assert that integrated mathematical modeling frameworks viewed from a systems biology perspective are needed. Such integrated frameworks could offer innovative contributions to the clinical women's cancers community, as answers to clinical questions cannot always be reached with contemporary clinical and experimental tools. Here, we recapitulate clinically known data regarding the progression and treatment of the breast and ovarian cancers. We compare and contrast the two malignancies whenever possible in order to emphasize areas where substantial contributions could be made by clinically inspired and validated mathematical modeling. We show how current paradigms in the mathematical oncology community focusing on the two malignancies do not make comprehensive use of, nor substantially reflect existing clinical data, and we highlight the modeling areas in most critical need of clinical data integration. We emphasize that the primary goal of any mathematical study of women's cancers should be to address clinically relevant questions. WIREs Syst Biol Med 2016, 8:337-362. doi: 10.1002/wsbm.1343 For further resources related to this article, please visit the WIREs website.

Nanotechnology for the delivery of phytochemicals in cancer therapy

The aim of this review is to summarize advances that have been made in the delivery of phytochemicals for cancer therapy by the use of nanotechnology. Over recent decades, much research effort has been invested in developing phytochemicals as cancer therapeutic agents. However, several impediments to their wide spread use as drugs still have to be overcome. Among these are low solubility, poor penetration into cells, high hepatic disposition, and narrow therapeutic index. Rapid clearance or uptake by normal tissues and wide tissue distribution result in low drug accumulation in the target tumor sites can result in undesired drug exposure in normal tissues. Association with or encapsulation in nanoscale drug carriers is a potential strategy to address these problems. This review discussed lessons learned on the use of nanotechnology for delivery of phytochemicals that been tested in clinical trials or are moving towards the clinic.

The effectiveness of nano chemotherapeutic particles combined with mifepristone depends on the PR isoform ratio in preclinical models of breast cancer

There is clinical and experimental evidence suggesting that antiprogestins might be used for the treatment of selected breast cancer patients. Our aim was to evaluate the effect of albumin-bound paclitaxel (Nab-paclitaxel) and pegylated doxorubicin liposomes (PEG-LD) in combination with mifepristone (MFP) in experimental breast cancer models expressing different ratios of progesterone receptor (PR) isoforms A and B. We used two antiprogestin-responsive (PRA>PRB) and two resistant (PRA<PRB) murine mammary carcinomas growing in BALB/c, GFP-BALB/c or nude mice, along with human T47D-YA and T47D-YB xenografts growing in immunocompromised NSG mice. MFP improved the therapeutic effects of suboptimal doses of Nab-paclitaxel or PEG-LD in murine and human carcinomas with higher levels of PRA than PRB. MFP induced tissue remodeling in PRA-overexpressing tumors, increasing the stromal/tumor cell ratio and the number of functional vessels. Accordingly, an increase in nanoparticles and drug accumulation was observed in stromal and tumor cells in MFP-treated tumors. We conclude that MFP induces an increase in vessels during tissue remodeling, favoring the selective accumulation of nanoparticles inside the tumors. We propose that antiprogestins have the potential to enhance the efficacy of chemotherapy in breast tumors with a high PRA/PRB ratio.

Carrier-free, functionalized pure drug nanorods as a novel cancer-targeted drug delivery platform

A one-dimensional drug delivery system (1D DDS) is highly attractive since it has distinct advantages such as enhanced drug efficiency and better pharmacokinetics. However, drugs in 1D DDSs are all encapsulated in inert carriers, and problems such as low drug loading content and possible undesirable side effects caused by the carriers remain a serious challenge. In this paper, a novel, carrier-free, pure drug nanorod-based, tumor-targeted 1D DDS has been developed. Drugs are first prepared as nanorods and then surface functionalized to achieve excellent water dispersity and stability. The resulting drug nanorods show enhanced internalization rates mainly through energy-dependent endocytosis, with the shape-mediated nanorod (NR) diffusion process as a secondary pathway. The multiple endocytotic mechanisms lead to significantly improved drug efficiency of functionalized NRs with nearly ten times higher cytotoxicity than those of free molecules and unfunctionalized NRs. A targeted drug delivery system can be readily achieved through surface functionalization with targeting group linked amphipathic surfactant, which exhibits significantly enhanced drug efficacy and discriminates between cell lines with high selectivity. These results clearly show that this tumor-targeting DDS demonstrates high potential toward specific cancer cell lines.

Synergistic Effects of the Green Tea Extract Epigallocatechin-3-gallate and Taxane in Eradication of Malignant Human Prostate Tumors

We have examined whether epigallocatechin-3-gallate (EGCG), and extract of green tea, in combination with taxane (i.e., paclitaxel and docetaxel), exerts a synergistic activity in blocking human prostate PC-3ML tumor cell growth in vitro and in vivo. Growth assays in vitro revealed that the IC(50) values were ∼30 µM, ∼3 nM, and ∼6 nM, for EGCG, paclitaxel and docetaxel, respectively. Isobolograms generated from the data clearly indicated that EGCG in combination with paclitaxel or docetaxel had an additive effect in blocking tumor cell growth. EGCG combined with taxane also had an additive effect to increase the expression of apoptotic genes, (p53, p73, p21, and caspase 3) and the percent apoptosis observed in vitro and in tumor modeling studies in severe combined immunodeficient mice. The tumor modeling studies clearly showed that EGCG plus taxane injected intraperitoneally (i.p.) induced a significant increase in apoptosis rates (TUNEL assays) and eliminated preexisting tumors generated from PC-3ML cells implanted i.p., increasing disease-free survival rates to greater than 90%. More importantly, the combination therapy (i.p. biweekly) blocked metastases after intravenous injection of PC-3ML cells through the tail vein. In mice treated with EGCG plus taxane, the disease-free survival rates increased from 0% (in untreated mice) to more than 70% to 80% in treated mice. Taken together, these data demonstrate for the first time that EGCG in combination with taxane may provide a novel therapeutic treatment of advanced prostate cancer.

Albumin-bound formulation of paclitaxel (Abraxane ABI-007) in the treatment of breast cancer

Breast cancer is the most common type of malignancy diagnosed in women. In the metastatic setting this disease is still uncurable. Taxanes represent an important class of antitumor agents which have proven to be fundamental in the treatment of advanced and early-stage breast cancer, but the clinical advances of taxanes have been limited by their highly hydrophobic molecular status. To overcome this poor water solubility, lipid-based solvents have been used as a vehicle, and new systemic formulations have been developed, mostly for paclitaxel, which are Cremophor-free and increase the circulation time of the drug. ABI-007 is a novel, albumin-bound, 130-nm particle formulation of paclitaxel, free from any kind of solvent. It has been demonstrated to be superior to an equitoxic dose of standard paclitaxel with a significantly lower incidence of toxicities in a large, international, randomized phase III trial. The availability of new drugs, such as Abraxane, in association with other traditional and non-traditional drugs (new antineoplastic agents and targeted molecules), will give the oncologist many different effective treatment options for patients in this setting.

Effects of Taxol on the Macrophage Function. Interactions with Some Immunological Parameters

The effects of Taxol on some immunological parameters were investigated, in vitro, in the murine macrophage cell line J774.1. Mitochondrial dehydrogenase activity and (3H) TdR incorporation were shown to be increased in Taxol treated cells. Likewise, Taxol induced TNF alpha secretion. But Taxol seemed to be a weak inducer of the two interleukins IL-1 and IL-2, since their detection occurred late in the cell culture supernatants.

Using nanotechnology to improve the characteristics of antineoplastic drugs: Improved characteristics of nab-paclitaxel compared with solvent-based paclitaxel

Nanotechnology refers to the use of very small pieces of matter, typically < or =200 nm in diameter. Nanoparticle albumin-bound (nab) paclitaxel, a soluble form of the cytotoxin paclitaxel that has demonstrated utility in the setting of cancer chemotherapy, is produced by nab technology using the protein albumin. nab-Paclitaxel targets tumors, enhances tumor penetration by the novel mechanism of albumin receptor-mediated (gp60) endothelial transcytosis, and avoids the use of surfactants and solvents such as Cremophor and Tween. nab-Paclitaxel minimizes the toxicities associated with Cremophor and eliminates the need for premedication for hypersensitivity reactions caused by Cremophor. The albumin coating that surrounds the active drug assists in the transport of the nanoparticles to the interior of the tumor cell that preferentially takes in albumin as a nutrient through the gp60 pathway. In nonclinical studies, nab-paclitaxel achieved higher intratumoral concentrations compared with solvent-based paclitaxel and increased the bioavailability of paclitaxel by eliminating the entrapment of paclitaxel in the plasma. Compared with solvent-based paclitaxel, at equitoxic doses, the nab-paclitaxel produced more complete regressions, longer time to recurrence, longer doubling times, and prolonged survival. nab-Paclitaxel has been shown to have superior efficacy compared with solvent-based paclitaxel without the need for premedication in clinical trials of patients with advanced solid tumors. nab-Paclitaxel has been effective in patients for whom previous chemotherapy has not been helpful. nab Technology has the potential to be applied to other insoluble drugs.

p27kip1 overexpression promotes paclitaxel-induced apoptosis in pRb-defective SaOs-2 cells

p27kip1 is a cyclin-dependent kinase (CDK) inhibitor, which controls several cellular processes in strict collaboration with pRb. We evaluated the role of p27kip1 in paclitaxel-induced apoptosis in the pRb-defective SaOs-2 cells. Following 48 h of exposure of SaOs-2 cells to 100 nM paclitaxel, we observed an increase in p27kip1 expression caused by the decrease of the ubiquitin-proteasome activity. Such increase was not observed in SaOs-2 cells treated with the caspase inhibitors Z-VAD-FMK, suggesting that p27kip1 enhancement at 48 h is strictly related to apoptosis. Finally, we demonstrated that SaOs-2 cells transiently overexpressing the p27kip1 protein are more susceptible to paclitaxel-induced apoptosis than SaOs-2 cells transiently transfected with the empty vector. Indeed, after 48 h of paclitaxel treatment, 41.8% of SaOs-2 cells transiently transfected with a pcDNA3-p27kip1 construct were Annexin V-positive compared to 30.6% of SaOs-2 cells transfected with the empty vector (P < 0.05). In conclusion, we demonstrated that transfection of the pRb-defective SaOs-2 cells with the p27kip1 gene via plasmid increases their susceptibility to paclitaxel-induced apoptosis. The promoting effect of p27kip1 overexpression on apoptosis makes p27kip1 and proteasomal inhibitors interesting tools for therapy in patients with pRb-defective cancers.

Inhibition of Restenosis With a Paclitaxel-Eluting, Polymer-Free Coronary Stent

BACKGROUND

The use of a stent to deliver a drug may reduce in-stent restenosis. Paclitaxel interrupts the smooth muscle cell cycle by stabilizing microtubules, thereby arresting mitosis.

METHODS AND RESULTS

On the basis of prior animal studies, the European evaLUation of the pacliTaxel Eluting Stent (ELUTES) pilot clinical trial (n=190) investigated the safety and efficacy of V-Flex Plus coronary stents (Cook Inc) coated with escalating doses of paclitaxel (0.2, 0.7, 1.4, and 2.7 microg/mm2 stent surface area) applied directly to the abluminal surface of the stent in de novo lesions compared with bare stent alone. The primary efficacy end point was angiographic percent diameter stenosis at 6 months. At angiographic follow-up, percent diameter stenosis was 33.9+/-26.7% in controls (n=34) and 14.2+/-16.6% in the 2.7-microg/mm2 group (n=31; P=0.006). Late loss decreased from 0.73+/-0.73 to 0.11+/-0.50 mm (P=0.002). Binary restenosis (> or =50% at follow-up) decreased from 20.6% to 3.2% (P=0.056), with no significant benefit from intermediate paclitaxel doses. Freedom from major adverse cardiac events in the highest (effective) dose group was 92%, 89%, and 86% at 1, 6, and 12 months, respectively (P=NS versus control). No late stent thromboses were seen in any treated group despite clopidogrel treatment for 3 months only.

CONCLUSIONS

Paclitaxel applied directly to the abluminal surface of a bare metal coronary stent, at a dose density of 2.7 microg/mm2, reduced angiographic indicators of in-stent restenosis without short- or medium-term side effects.

Population pharmacokinetics of low-dose paclitaxel in patients with brain tumors

Our aim was to assess the pharmacokinetics of a low-dose schedule of paclitaxel in combination with radiation therapy in patients with brain tumors. Eighteen patients received 20-50 mg/m2 paclitaxel as a 1-h infusion 18-24 h before radiation with 2 Gy on 5 consecutive days. In total, 156 plasma samples from 13 patients and 38 urine samples from nine patients were collected and analyzed by a validated capillary electrophoresis method. Data analysis was done using NONMEM with a two-compartmental model and proportional error model. No signs of non-linearity in the pharmacokinetic parameters were observed in this dosing range. The median cumulative urinary excretion was 2.4% (range 0.86-7.72%) of the given dose. Plasma clearance was found to be 6.71 l/h+/-70% and central volume of distribution was 3.64 l+/-79% (population mean +/- interindividual variability, respectively). At the time of the radiation, i.e. 24 h after administration with the lowest dose of 20 mg/m2, the mean concentration of paclitaxel was 0.038 mg/l (0.045 microM) in plasma. We conclude that even with the lowest dose of 20 mg/m2 paclitaxel, plasma concentrations at the time of radiation are achieved which are radiosensitizing in vitro.

Evaluation of the potential cancer chemotherapeutic efficacy of natural product isolates employing in vivo hollow fiber tests

The hollow fiber test has been developed for the preliminary in vivo assessment of cancer chemotherapeutic efficacy of selected natural products. Using this model, we have established growth conditions for HL-60, HUVEC, Ishikawa, KB, KB-V1, LNCaP, Lu1, MCF-7, Mel2, P-388, and SW626 cells implanted at the intraperitoneal (i.p.) and subcutaneous (s.c.) compartments of athymic mice. Five cytotoxic natural product isolates (2-6) were tested in this model, along with paclitaxel (taxol) (1). Among the compounds tested, dioscin (2) and 13-methoxy-15-oxozoapatlin (3) were found to be active, indicating their potential to function as cancer chemotherapeutic agents. On the other hand, ochraceolide A (4), alpha-lapachone (5), and 2-(1-hydroxyethyl)naphtha[2,3-b]furan-4,9-quinone (6), all of which were significantly cytotoxic to cultured mammalian cells, did not mediate significant responses with the hollow fiber model. In further xenograft studies using KB cells implanted at the subcutaneous site, compound 3 mediated a statistically significant response which was consistent with the response observed at the subcutaneous compartment in the hollow fiber tests. In sum, these studies illustrate the usefulness of the hollow fiber model in natural product drug discovery programs. Preliminary indications of potential therapeutic efficacy can be provided quickly at relatively low expense. Agents capable of mediating a response at the subcutaneous site would appear to warrant greatest attention.

Growth-inhibiting effects of taxol on human liver cancer in vitro and in nude mice

AIM: To investigate the effects of taxol on SMMC-7721 human hepatoma and its mechanisms.

METHODS: In vitro cell growth was assessed by trypan blue exclusion method. Experimental hepatoma model was established by seeding SMMC-7721 cells subcutaneously into Balb/c (nu/nu) nude mice. In vivo tumor growth was determined by measurement of tumor diameter with Vernier calipers. The syntheses of DNA, RNA and protein were analyzed by incorporation of ³H-thymidine, ³H-uridine and ³H-leucine respectively. Using light and electron microscopes to observe the morphological changes of cells including mitosis and apoptosis.

RESULTS: Taxol was effective against SMMC-7721 human hepatoma cell growth in the ranges of 2.5 nmol/L-10 nmol/L- with mitotic arrest and apoptosis in vitro. DNA, RNA and protein syntheses in cells were also obviously suppressed by in vitro treatment of taxol for 72 h. Taxol at 2.5 nmol/L reduced ³H-thymidine uptake to about 34% of the control value (P ＜ 0.05). Increasing the dose of taxol to 20 nmol/L resulted in a greater decrease in ³H-thymidine incorporation to 60% of the control value (P ＜ 0.01). At a concentration of 20 nmol/L, the ³H-uridine and ³H-leucine uptakes were reduced to 52% (P ＜ 0.05) and 63% (P ＜ 0.01), respectively. In vivo, taxol significantly inhibited SMMC-7721 tumor growth at 10 mg/kg, i.p. once daily for 10 d. A more than 90% decrease in tumor volume was observed by day 11 (P ＜ 0.01) similarly with mitotic arrest and cell apoptosis.

CONCLUSION: Taxol has a marked anticancer activity in SMMC-7721 human hepatoma both in vitro and in nude mice. Its mechanisms might be associated with mitotic arrest, subsequently, apoptosis of the hepatoma cells. No obvious toxicity was observed with in vivo administration of taxol.

Paclitaxel induces apoptosis in Saos-2 cells with CD95L upregulation and Bcl-2 phosphorylation

We examined the effect of paclitaxel on human osteoblastic cells Saos-2 to determine if paclitaxel can affect proliferation and apoptosis. We used a p53-negative cell line in order to mimic the loss of function frequently observed at the clinical level. Paclitaxel induced cell death in a dose- and time-dependent manner. Marked nuclear condensation and fragmentation of chromatin were observed by Hoechst 33258 stain, DNA ladder formation, electron microscopy, and flow cytometry at concentrations as low as 100 nM, a concentration which can be achieved by infusion in human plasma. At 100 nM, paclitaxel induced a G2 arrest at 8 h of treatment. The cells then continued to accumulate in G2 until 72 h when the percentage of apoptotic events reached 54%. At the molecular level, Bcl-2 protein was phosphorylated at 16 h and PARP protein was cleaved, indicating the activation of caspase-3-like proteases. Caspase inhibitors Z-VAD-FMK and Z-DEVD-FMK rescued Saos-2 cells from paclitaxel-induced apoptosis. CD95 expression was constantly high, while CD95L showed a threefold increase in expression. This suggests that, following the G2 arrest, apoptosis is induced through the CD95/CD95L system.

Paclitaxel: an effective antineoplastic agent in the treatment of xenotransplanted hepatoblastoma

BACKGROUND

Hepatoblastoma is an uncommon liver tumor of infancy and early childhood. Though most patients with nonmetastatic hepatoblastomas can be cured by defining surgical strategies and chemotherapy regimes, new drugs are needed for children with advanced hepatoblastomas. The activity of paclitaxel as a new antineoplastic agent with limited experience in pediatric oncology was studied in a xenograft model.

PROCEDURE

Hepatoblastoma cell suspensions from three children were transplanted subcutaneously into nude mice NMRI (nu/nu). One of the primary tumors was an embryonal multifocal hepatoblastoma, whereas the other tumors were embryonal/fetal hepatoblastomas localized on a liver lobe. After 4 weeks, xenografted tumor sizes reached 50-100 mm3. The xenografted tumors resembled their originals histologically and produced high levels of alpha-fetoprotein. The efficiency of paclitaxel at equitoxic doses was analyzed.

RESULTS

Paclitaxel produced an effect in all three hepatoblastomas. There was a significant reduction of tumor volume (P < 0.001) and alpha-fetoprotein levels after chemotherapy (P < 0.0001). The proliferation activity of the tumor cells corresponded with these results. Histologically, after treatment with paclitaxel the tumor regression was 35%-49%. The mechanism of paclitaxel action could be demonstrated by light microscopy immunohistochemistry and electron microscopy.

CONCLUSIONS

The preliminary results in phase I trials of solid tumors in children and the results of this study suggest that paclitaxel in phase II studies can now be entertained for patients with hepatoblastoma.

Effectiveness of cisplatin, paclitaxel, and suramin against human malignant mesothelioma xenografts in athymic nude mice

BACKGROUND AND OBJECTIVES

Malignant mesothelioma has a poor prognosis and is refractory to many agents. The antitumor effectiveness of cisplatin, paclitaxel, and suramin as single agents and in combination was evaluated in vivo against four lines of human pleural malignant mesothelioma xenografts in athymic nude mice, including one epithelial type and three fibrosarcomatous.

METHODS

After growth of tumors occurred by day 54 or 55, mice were randomized in groups of four each to receive either cisplatin 4 mg/kg intraperitoneally weekly x5, or paclitaxel (Taxol) 12.5 mg/kg subcutaneously daily 5 days/week for 3 consecutive weeks, or suramin 60 mg/kg intraperitoneally daily x4,versus controls treated with normal saline.

RESULTS

Cisplatin was very effective against one line and also to a lesser degree against another line. Paclitaxel showed antitumor effects similar to cisplatin, being very effective in one line, and also showed good activity in another line. Suramin was basically inactive in all four lines. Following the results obtained with these single agents, it was decided to evaluate the combination of cisplatin and paclitaxel, which resulted in more pronounced antitumor effect in all four cell lines.

CONCLUSIONS

These results indicate that the combination of cisplatin and paclitaxel is superior to each agent alone in this model, and that it deserves to be evaluated in patients with malignant mesothelioma.

A mathematical model of breast and ovarian cancer treated with paclitaxel

A mathematical model that describes the effects of cell-cycle-specific drugs on cancer and normal tissue is developed. The model takes into account the proliferating cells, which are sensitive to the treatment, and the quiescent cells, which are resistant to the treatment. With the use of information from the medical literature, model parameters are estimated for breast and ovarian cancer as well as for bone marrow. Then, with the use of the model and the estimated parameters, some acceptable treatment strategies are discussed in terms of treatment period, drug-infusion time, and proliferative fraction of cancer mass. Finally, these results are compared with current clinical practices for treatment with Taxol, and possible improvements on current treatment strategies are suggested.

Anti-tumor efficacy of paclitaxel against human lung cancer xenografts

We examined paclitaxel for anti-tumor activity against human lung cancer xenografts in nude mice and compared its efficacy with that of cisplatin, currently a key drug for lung cancer chemotherapy. Five non-small cell lung cancers (A549, NCI-H23, NCI-H226, NCI-H460 and NCI-H522) and 2 small cell lung cancers (DMS114 and DMS273) were chosen for this study, since these cell lines have been well characterized as regards in vitro and in vivo drug sensitivity. These cells were exposed to graded concentrations of paclitaxel (0.1 to 1000 nM) for 48 h. The 50% growth-inhibitory concentrations (GI50) for the cell lines ranged from 4 to 24 nM, which are much lower than the achievable peak plasma concentration of paclitaxel. In the in vivo study, 4 cell lines (A549, NCI-H23, NCI-H460, DMS-273) were grown as subcutaneous tumors xenografts in nude mice. Paclitaxel was given intravenously as consecutive daily injections for 5 days at the doses of 24 and 12 mg/kg/day. Against every xenograft, paclitaxel produced a statistically significant tumor growth inhibition compared to the saline control. Paclitaxel at 24 mg/kg/day was more effective than cisplatin at 3 mg/kg/day with the same dosing schedule as above, although the toxicity of paclitaxel was similar to or rather lower than that of cisplatin, in terms of body weight loss. In addition, paclitaxel showed potent activity against 2 other lung cancer xenografts (NCI-H226 and DMS114). Therefore, paclitaxel showed more effective, wider-spectrum anti-tumor activity than cisplatin in this panel of 6 lung cancer xenografts. These findings support the potential utility of paclitaxel in the treatment of human lung cancer.

p53-independent apoptosis induced by paclitaxel through an indirect mechanism

The efficacy of chemotherapeutic agents may be determined by a number of different factors, including the genotype of the tumor cell. The p53 tumor suppressor gene frequently is mutated in human tumors, and this may contribute to chemotherapeutic resistance. We tested the requirement for wild-type p53 in the response of tumor cells to treatment with paclitaxel (trade name Taxol), an antineoplastic agent that stabilizes cellular microtubules. Although paclitaxel is broadly effective against human tumor xenografts in mice, including some known to carry p53 mutations, we found that p53-containing mouse tumor cells were significantly more sensitive to direct treatment with this drug than were p53-deficient tumor cells. In an attempt to reconcile this apparent discrepancy, we examined the requirement for p53 in the cytotoxic effects of tumor necrosis factor alpha (TNF-alpha), a cytokine released from murine macrophages upon paclitaxel treatment. Conditioned medium from paclitaxel-treated macrophages was capable of inducing p53-independent apoptosis when applied to transformed mouse embryonic fibroblasts and was inhibitable by antibodies against TNF-alpha. Furthermore, in response to direct treatment with TNF-alpha, both wild-type and p53-deficient tumor cells underwent apoptosis to similar extents and with similar kinetics. Our results suggest that the efficacy of paclitaxel in vivo may be due not only to its microtubule-stabilizing activity, but its ability to activate local release of an apoptosis-inducing cytokine.

Drug delivery systems: water soluble taxol 2'-poly(ethylene glycol) ester prodrugs-design and in vivo effectiveness

Water soluble 2'-taxol poly(ethylene glycol) (PEG) esters have been synthesized and shown to function in vitro as prodrugs. However, in vivo experiments clearly establish that in order for these prodrugs to behave in a predictable fashion, the molecular weight of PEG must be of such magnitude so as to maintain a t1/2(circulation) > t1/2(hydrolysis). When PEG derivatives of molecular weight approximately 40 kDa were employed with paclitaxel, ca. 4% by weight of paclitaxel was carried by the water soluble prodrug form, and equivalent in vivo toxicity and increased life expectancy in the P388-treated mouse was observed. An effective method for prescreening prodrugs was found to be the acute murine lethality, which reflects the equivalency of the solubilized transport form and the native drug.

Influence of various concentrations of taxol on cell survival, micronuclei induction, and LDH activity in cultured V79 cells

The clastogenic effect of various concentrations of taxol, namely 0, 10, 25, 50, 100, 250 and 500 nM was evaluated in V79 cells grown in vitro. Treatment of V79 cells with different concentrations of taxol reduced the survival in a concentration dependent manner. However, the frequency of micronuclei increased in a concentration dependent manner and the dose response was linear quadratic. Similarly, lactate dehydrogenase also increased with the increase in taxol concentration. The micronuclei and lactate dehydrogenase showed an inverse relationship with the cell survival.

High-performance liquid chromatographic procedures for the quantitative determination of paclitaxel (Taxol) in human urine

A reversed-phase high-performance liquid chromatographic (RP-HPLC) method has been developed and validated for the quantitative determination of paclitaxel in human urine. A comparison is made between solid-phase extraction (SPE) and liquid-liquid extraction (LLE) as sample pretreatment. The HPLC system consists of an APEX octyl analytical column and acetonitrile-methanol-0.2 microM ammonium acetate buffer pH 5 (4:1:5, v/v) as the mobile phase. Detection is performed by UV absorbance measurement at 227 nm. The SPE procedure involves extraction on Cyano Bond Elut columns. n-Butylchloride is the organic extraction fluid used for the LLE. The recoveries of paclitaxel in human urine are 79 and 75% for SPE and LLE, respectively. The accuracy for the LLE and SPE sample pretreatment procedures is 100.4 and 104.9%, respectively, at a 5 micrograms/ml drug concentration. The lower limit of quantitation is 0.01 microgram/ml for SPE and 0.25 microgram/ml for LLE. Stability data of paclitaxel in human urine are also presented.

Antioxidant status and lipid peroxidation in athymic mice xenografted with two types of human tumors

Antioxidants and reactive oxygen species are considered to play an important role in experimental in vivo carcinogenesis studies. We attempted in this study to evaluate the repercussions on the antioxidant and lipid peroxide status of the growth of human malignant tumors xenografted into athymic mice. We selected three tumor models: two urothelial carcinomas (bladder tumors stage 3) and one brain tumor (glioblastoma stage 4). All these tumors exhibited a fast growth pattern when xenografted into athymic mice. Tumoral tissue was implanted subcutaneously. After growth establishment each tumor size was measured at regular intervals: every 2 d for bladder tumor and twice a week for glioblastoma. The period of observation was 3 wk for bladder tumors and 5 wk for glioblastoma. At the end of the observation period, all mice were sacrificed; tumoral tissue was taken and blood collected. Superoxide dismutase activity (SOD), glutathione peroxidase activity (GSH-Px), zinc (Zn), selenium (Se), and thiobarbituric acid reactive substances (TBARS) were measured in blood. TBARS alone were measured into tumoral tissue. A modification of the antioxidant blood status was observed in mice xenografted with bladder tumors with decrease in Se status and GSH-Px activities, and increase in TBARS. Such an effect was absent in mice xenografted with glioblastoma. It would appear that an oxygen-mediated stress exists in the animal bearing an implanted tumor compared with the control group, and that tumoral tissue itself is able to induce an oxidative stress into its host. All this leads to a disturbance of the antioxidant defense system.

Taxanes: a new class of antitumor agents

Taxanes belong to a new group of antineoplastic agents with a novel mechanism of action for a cytotoxic drug. They promote microtubule assembly and stabilize the microtubules. Paclitaxel, the first agent in this group to become available, was isolated from the Pacific yew, Taxus brevifolia, in 1971. In preclinical and clinical studies, paclitaxel and its semisynthetic analog docetaxel exhibit significant antitumor activity. This review deals with the physicochemical properties, pharmacology, and results of preclinical and clinical trials of the taxanes.

Paclitaxel (Taxol) concentrations in brain tumor tissue

BACKGROUND

Paclitaxel (Taxol) is a novel chemotherapeutic agent, active against a variety of tumors. It is not known whether the drug penetrates brain tumor tissue.

PATIENTS AND METHODS

Three patients with a recurrent glioma received paclitaxel (175 mg/m2) in a 3-hour i.v. infusion prior to surgery. Paclitaxel concentrations were measured in the tumor tissue, cerebrospinal fluid, cyst fluid, plasma and, in one patient, normal brain tissue.

RESULTS

Tumor tissue concentrations were in the therapeutic range in all three patients. Brain tissue concentration, however, was below the detection limit of the trial.

CONCLUSIONS

These findings suggest that paclitaxel may have a place in brain tumor therapy. The low concentration in normal brain tissue, as observed in one patient, may suggest, however, that the drug does not cross the intact bloodbrain barrier.

Paclitaxel. A review of its pharmacodynamic and pharmacokinetic properties and therapeutic potential in the treatment of cancer

Paclitaxel is a new anticancer agent with a novel mechanism of action. It promotes polymerisation of tubulin dimers to form microtubules and stabilises microtubules by preventing depolymerisation. In noncomparative trials, continuous infusion of paclitaxel 110 to 300 mg/m2 over 3 to 96 hours every 3 to 4 weeks produced a complete or partial response in 16 to 48% of patients with ovarian cancer and 25 to 61.5% of patients with metastatic breast cancer, many of whom were refractory to treatment with cisplatin or doxorubicin, respectively. 23 to 100% of patients with ovarian cancer achieved complete or partial responses with paclitaxel in combination with cisplatin, carboplatin, cyclophosphamide, altretamine and/or doxorubicin. Similarly, response rates of 30 to 100% were observed with paclitaxel plus doxorubicin, cisplatin, mitoxantrone and/or cyclophosphamide in patients with metastatic breast cancer. Comparative trials in patients with advanced ovarian cancer showed paclitaxel therapy to produce greater response rates than treatment with parenteral hydroxyurea (71 vs 0%) or cyclophosphamide (when both agents were combined with cisplatin) [79 vs 63%]. Paclitaxel was also more effective than mitomycin in 50 patients with previously untreated breast cancer (partial response in 20 vs 4% of patients). Paclitaxel therapy also produced promising results in patients with advanced squamous cell carcinoma of the head and neck, malignant melanoma, advanced non-small cell lung cancer (NSCLC), small cell lung cancer (SCLC), germ cell cancer, urothelial cancer, oesophageal cancer, non-Hodgkin's lymphoma or multiple myeloma, and was successfully combined with cisplatin, carboplatin and/or etoposide in patients with NSCLC, SCLC or advanced squamous cell carcinoma of the head and neck. Hypersensitivity reactions were initially a concern with administration of paclitaxel, although current dosage regimens have reduced the incidence of these events to less than 5%. The major dose-limiting adverse effects of paclitaxel are leucopenia (neutropenia) and peripheral neuropathy. Other haematological toxicity was generally mild. Cardiac toxicity was reported in small numbers of patients and most patients developed total alopecia. Several aspects of paclitaxel use remain to be clarified, including the optimal treatment schedule and infusion time, confirmation of the tolerability profile and efficacy of combination regimens in an expanded range of malignancies. Long term follow-up of paclitaxel recipients will also allow the effects of the drug on patient survival to be determined. Nevertheless, paclitaxel is a promising addition to the current therapies available, with significant activity reported in patients with advanced ovarian or breast cancer or other types of tumors.(ABSTRACT TRUNCATED AT 400 WORDS)

Comparison of paclitaxel and docetaxel activity on human ovarian carcinoma xenografts

The antitumour activity of paclitaxel (NSC 125973) and docetaxel (RP 56976, NSC 628503) was evaluated and compared against human ovarian carcinoma (HOC) xenografts in nude mice. Paclitaxel and docetaxel were given intravenously (i.v.) at a dose range of 16.6-34.5 mg/kg, once every 4 days for three consecutive doses to nude mice with HOC xenografts, transplanted subcutaneously (s.c.) (HOC18 and HOC22-S) or intraperitoneally (i.p.) (HOC8 and HOC22). Paclitaxel and docetaxel, at the highest dosage, induced complete tumour regression in 80-100% and 67% of mice bearing HOC22-S and HOC18 s.c., respectively. Both drugs cured 100% of mice bearing early stage HOC22 tumour in the peritoneal cavity, while treatment at an advanced stage significantly increased the survival time of all the mice. Both induced a 57% cure rate in mice bearing HOC8 in the peritoneal cavity. Paclitaxel and docetaxel were more effective than cisplatin (4 mg/kg, same dosing regime as above) used as a reference compound. These findings indicate that paclitaxel and docetaxel were highly active on four HOC xenograft models. No significant difference between them was detected in ovarian cancer xenografts.

Cytotoxic studies of paclitaxel (Taxol) in human tumour cell lines

The cytotoxicity of paclitaxel against eight human tumour cell lines has been studied with in vitro clonogenic assays. The fraction of surviving cells fell sharply after exposure for 24 h to paclitaxel concentrations ranging from 2 to 20 nM; the paclitaxel IC50 was found to range between 2.5 and 7.5 nM. Increasing the paclitaxel concentration above 50 nM, however, resulted in no additional cytotoxicity after a 24 h drug exposure. Cells incubated in very high concentrations of paclitaxel (10,000 nM) had an increase in survival compared with cells treated with lower concentrations of the drug. Prolonging the time of exposure of cells to paclitaxel from 24 to 72 h increased cytotoxicity from 5 to 200 fold in different cell lines. Exponentially growing cells were more sensitive to paclitaxel than were cells in the plateau phase of growth. Cremophor EL, the diluent in which the clinical preparation of paclitaxel is formulated, antagonised paclitaxel at concentrations of 0.135% (v/v). These data suggest that paclitaxel will be most effective clinically when there is prolonged exposure of tumour to the drug. Further, it appears that modest concentrations (i.e., 50 nM) should be as effective as higher concentrations of paclitaxel. Finally, we have noted that Cremophor EL is a biologically active diluent and, at high concentrations (0.135% v/v), can antagonise paclitaxel cytotoxicity.

Antitumor activity of taxol (NSC-125973) in human ovarian carcinomas growing in the peritoneal cavity of nude mice

BACKGROUND

The unique mechanism of action of taxol (NSC-125973) as microtubule stabilizing agent and its potential activity in clinical trials have generated considerable interest in the development of this agent. As taxol was reported to be active on advanced and refractory ovarian carcinomas we focused our studies on the xenograft model of human ovarian carcinoma that develops ascites and tumor dissemination in the peritoneal cavity of nude mice.

METHODS

The antitumor activity of taxol was evaluated on two human ovarian carcinoma xenografts (HOC8 and HOC22) transplanted i.p. in nude mice. Drug was given i.v. at doses of 20-34.5 mg/kg every four days three times (Q4 x 3) and the increment of life span (%ILS) was evaluated. Cisplatin at the dosage of 4mg/kg, Q4 x 3 was used as reference drug in each experiment.

RESULTS

Taxol given at doses of 20 mg/kg and 34.5 mg/kg to early-stage HOC22 (treatment starting 3 days after tumor transplant) cured all the mice, while the same dose regimens given to advanced HOC22 (treatment starting 14 days after tumor transplant) significantly prolonged the survival time of the mice (ILS = 197% and 300%). Taxol given 3 days after HOC8 transplant significantly prolonged the survival time of tumor-bearing nude mice, inducing complete responses in 50% and 25% of mice receiving, respectively, 34.5 mg/kg/injection and 20 mg/kg/injection. On both ovarian carcinoma xenografts taxol was more active than equitoxic doses of the reference drug cisplatin.

CONCLUSIONS

The therapeutic activity against ovarian carcinoma xenografts supports the potential of taxol in the treatment of this neoplasia and forms the basis for future investigations aimed at optimizing the therapeutic activity of taxol given alone or in combination with other drugs.

Steady-state plasma concentrations and effects of taxol for a 250 mg/m2 dose in combination with granulocyte-colony stimulating factor in patients with ovarian cancer

Taxol, a natural product initially isolated from the stem bark of the western yew Taxus brevifolia, is undergoing phase II and III evaluation due to its reported activity against a variety of tumors. Previous studies have described correlations between plasma concentrations and toxicity when taxol is given (a) at lower doses, (b) for shorter infusion times, and (c) without granulocyte-colony-stimulating factor. Because the 24-h infusion schedule is most commonly used in current clinical trials, we attempted to correlate steady-state plasma concentrations of taxol achieved with a 24-h continuous i.v. infusion with toxicities and responses. Plasma samples from 48 refractory ovarian cancer patients were obtained 1-2 h prior to the end of the first taxol infusion. Taxol concentrations were measured by high-performance liquid chromatography (HPLC). Interpatient variation of taxol plasma concentrations was small (mean +/- SD, 0.85 +/- 0.21 microM. Total taxol body clearance was 256 +/- 72 ml min-1 m-2 (mean +/- SD). Taxol plasma protein binding was 88.4% +/- 1.3% (mean +/- SD, n = 9). Grade 3-4 hematologic toxicity, mainly leukopenia, occurred in 92% of the patients. The leukopenia was transient and did not warrant a reduction in the dose of taxol. Grade 3-4 nonhematologic toxicity occurred in 8% of the patients. No severe hypersensitivity reaction or grade 3-4 neurotoxicity was observed. Correlations of plasma concentrations and toxicities were not feasible due to the high frequency of hematologic effects and the low frequency of nonhematologic toxicity. The low degree of interpatient variation in plasma concentrations hindered the development of correlations with response.

The clinical pharmacology and use of antimicrotubule agents in cancer chemotherapeutics

Although there has been a rapid expansion of the number of classes of compounds with antineoplastic activity, few have played a more vital role in the curative and palliative treatment of cancers than the antimicrotubule agents. Although the vinca alkaloids have been the only subclass of antimicrotubule agents that have had broad experimental and clinical applications in oncologic therapeutics over the last several decades, the taxanes, led by the prototypic agent taxol, are emerging as another very active class of antimicrotubule agents. After briefly reviewing the mechanisms of antineoplastic action and resistance, this article comprehensively reviews the clinical pharmacology, therapeutic applications, and clinical toxicities of selected antimicrotubule agents.

New natural products in cancer chemotherapy

Four new and clinically relevant antineoplastic natural products are reviewed. Taxol is derived from the bark of the western yew. It promotes the formation of microtubule bundles which deform the cytoskeleton and interfere with mitosis. Although phase II efficacy testing is incomplete, taxol is effective in the treatment of patients with ovarian carcinoma and has some activity in patients with non-small cell lung cancer and melanoma. It remains untested against several other neoplasms. The chief toxicities of taxol are myelosuppression, mucositis, anaphylactoid reactions, and peripheral neuropathy. Homoharringtonine is the most active and abundant of the cephalotaxine esters derived from the genus Cephalotaxus. This agent appears to act at the ribosome to inhibit protein synthesis and has clinical activity in patients with acute myelogenous leukemia. The dose limiting toxicities of homoharringtonine are hypotension and myelosuppression. SKF 104864 and CPT-11 are derivatives of camptothecin which are still in early clinical trials. They are cytotoxic in vitro, acting through an interaction with topoisomerase I to induce DNA fragmentation. The spectra of activity and toxicity of SKF 104864 and CPT-11 are still undefined. All four of these new natural products offer possibilities for clinical activity for patients with a variety of malignancies.

In vitro and in vivo antitumoral activity of free, and encapsulated taxol

The anti-tumoral activity of taxol encapsulated either in liposomes or in nanocapsules was compared with that of free taxol, using the P388 and L1210 leukaemia test systems. The in vitro inhibition of cell growth was measured after 48 h and 96 h exposure to various concentrations of taxol. With P388 cells, the inhibitory activities of the three forms of the drug were similar. With the L1210 cells, however, the concentrations required for a 50 per cent inhibition of cell growth (IC50) after 48 h exposure to the drug were greater for nanocapsules than for liposomes or free taxol, the values being 0.060, 0.043 and 0.035 micrograms ml-1, respectively. However, a greater efficiency of nanocapsules was observed after 96 h exposure. Using cytomorphometric analysis, no difference was found between L1210 cells treated either with free or encapsulated taxol. In vivo, mice bearing P388 leukaemia, and treated either with taxol solubilized with 5 per cent DMSO + 5 per cent cremophor in saline solution, or with taxol encapsulated in liposomes (IP daily dose of 12.5 mg Kg-1 body weight x 4 days) showed ILS values of 65.8% and 67.9% respectively. Nanocapsules proved to be toxic, apparently due to their composition: this problem is currently under investigation.