Taxanes in combined modality therapy for solid tumors

Effect of Switching the Histamine-1 Receptor Antagonist Clemastine to Cetirizine in Paclitaxel Premedication Regimens: The H1-Switch Study

PURPOSE

Premedication, including a histamine-1 receptor (H1) antagonist, is recommended to all patients treated with paclitaxel chemotherapy to reduce the incidence of hypersensitivity reactions (HSRs). However, the scientific basis for this premedication is not robust, which provides opportunities for optimization. Substitution of intravenously administered first-generation H1 antagonist for orally administered second-generation H1 antagonist could reduce side effects, and improve efficiency and sustainability. This study investigates the efficacy and safety of substituting intravenous clemastine for oral cetirizine as prophylaxis for paclitaxel-induced HSRs.

METHODS

This single-center, prospective, noninferiority study compares a historic cohort receiving a premedication regimen with intravenous clemastine to a prospective cohort receiving oral cetirizine. Primary end point of the study is HSR grade ≥3. The difference in incidence was calculated together with the 90% CI. We determined that the two-sided 90% CI of HSR grade ≥3 incidence in the oral cetirizine cohort should not be more than 4% higher (ie, the noninferiority margin) compared with the intravenous clemastine cohort.

RESULTS

Two hundred and twelve patients were included in the oral cetirizine cohort (June 2022 and May 2023) and 183 in the intravenous clemastine cohort. HSR grade ≥3 incidence was 1.6% (n = 3) in the intravenous clemastine cohort and 0.5% (n = 1) in the oral cetirizine cohort, resulting in a difference of -1.2% (90% CI, -3.4 to 1.1).

CONCLUSION

Premedication containing oral cetirizine is as safe as premedication containing intravenous clemastine in preventing paclitaxel-induced HSR grade ≥3. These findings could contribute to optimization of care for patients and improve efficiency and sustainability.

Indol-3-ylglyoxylamide as Privileged Scaffold in Medicinal Chemistry

In recent years, indolylglyoxylamide-based derivatives have received much attention due to their application in drug design and discovery, leading to the development of a wide array of compounds that have shown a variety of pharmacological activities. Combining the indole nucleus, already validated as a "privileged structure," with the glyoxylamide function allowed for an excellent template to be obtained that is suitable to a great number of structural modifications aimed at permitting interaction with specific molecular targets and producing desirable therapeutic effects. The present review provides insight into how medicinal chemists have elegantly exploited the indolylglyoxylamide moiety to obtain potentially useful drugs, with a particular focus on compounds exhibiting activity in in vivo models or reaching clinical trials. All in all, this information provides exciting new perspectives on existing data that can be useful in further design of indolylglyoxylamide-based molecules with interesting pharmacological profiles. The aim of this report is to present an update of collection data dealing with the employment of this moiety in the rational design of compounds that are able to interact with a specific target, referring to the last 20 years.

Cancer therapy's impact on lipid metabolism: Mechanisms and future avenues

Atherosclerotic cardiovascular disease is a growing threat among cancer patients. Not surprisingly, cancer-targeting therapies have been linked to metabolic dysregulation including changes in local and systemic lipid metabolism. Thus, tumor development and cancer therapeutics are intimately linked to cholesterol metabolism and may be a driver of increased cardiovascular morbidity and mortality in this population. Chemotherapeutic agents affect lipid metabolism through diverse mechanisms. In this review, we highlight the mechanistic and clinical evidence linking commonly used cytotoxic therapies with cholesterol metabolism and potential opportunities to limit atherosclerotic risk in this patient population. Better understanding of the link between atherosclerosis, cancer therapy, and cholesterol metabolism may inform optimal lipid therapy for cancer patients and mitigate cardiovascular disease burden.

CK1 Is a Druggable Regulator of Microtubule Dynamics and Microtubule-Associated Processes

Protein kinases of the Casein Kinase 1 family play a vital role in the regulation of numerous cellular processes. Apart from functions associated with regulation of proliferation, differentiation, or apoptosis, localization of several Casein Kinase 1 isoforms to the centrosome and microtubule asters also implicates regulatory functions in microtubule dynamic processes. Being localized to the spindle apparatus during mitosis Casein Kinase 1 directly modulates microtubule dynamics by phosphorylation of tubulin isoforms. Additionally, site-specific phosphorylation of microtubule-associated proteins can be related to the maintenance of genomic stability but also microtubule stabilization/destabilization, e.g., by hyper-phosphorylation of microtubule-associated protein 1A and RITA1. Consequently, approaches interfering with Casein Kinase 1-mediated microtubule-specific functions might be exploited as therapeutic strategies for the treatment of cancer. Currently pursued strategies include the development of Casein Kinase 1 isoform-specific small molecule inhibitors and therapeutically useful peptides specifically inhibiting kinase-substrate interactions.

Mechanisms of influence of the microtubule over-stabilizing ligands on the structure and intrinsic dynamics of α,β-Tubulin

The intervention into the cell cycle progression by administering microtubule over-stabilizing ligands that arrest the mitotic cell division by preventing spindle dissociation, is a promising strategy to fight against cancers. The building blocks of the microtubules and the spindles, i.e. the α,β-tubulin dimer, upon binding of such ligands, stay more comfortably in the microtubular multimeric form; the phenomenon of which is the key to the said over-stabilization. Using two such over-stabilizing ligands, Taxol and Taxotere, the present work reports the collective changes that these ligands induce on the structure and dynamics of the α,β-tubulin dimer which could be reconciled as the molecular basis of the over-stabilization of the microtubules; the trends have been found to be statistically significant across all independent calculations on them. The ligand binding increases the coherence between the residue communities of the two opposite faces of the β-subunit, which in a periodic arrangement in microtubule are knwon to form intermolecular contact with each other. This is likely to create an indirect cooperativity between those structural regions and this is a consequence of the reshuffling of the internal network of interactions upon ligand binding. Such reorganizations are also complemented by the increased contributions of the softer modes of the intrinsic dynamics more, which is likely to increase the plasticity of the system favourable for making structural adjustments in a multimer. Further, the ligands are able to compensate the drawback of lacking one phosphate group in protein-GDP interactions compared to the same for protein-GTP and this is in agreement with the hints form the earlier reports. The findings form a mechanistic basis of the enhanced capacity of the α,β-tubulin dimer to get more favourably accommodated into the microtubule superstructure upon binding either of Taxol and Taxotere.

The added value of H2 antagonists in premedication regimens during paclitaxel treatment

BACKGROUND

Ranitidine, a histamine 2 blocker, is the standard of care to prevent hypersensitivity reactions (HSRs) caused by paclitaxel infusion. However, the added value of ranitidine in this premedication regimen is controversial. Therefore, we compared the incidence of HSRs during paclitaxel treatment between a standard regimen including ranitidine and a regimen without ranitidine.

METHODS

This prospective, pre-post interventional, non-inferiority study compared the standard premedication regimen (N = 183) with dexamethasone, clemastine and ranitidine with a premedication regimen without ranitidine (N = 183). The primary outcome was the incidence of HSR grade ≥3. Non-inferiority was determined by checking whether the upper bound of the two-sided 90% confidence interval (CI) for the difference in HSR rates excluded the +6% non-inferiority margin.

RESULTS

In both the pre-intervention (with ranitidine) and post-intervention (without ranitidine) group 183 patients were included. The incidence of HSR grade ≥3 was 4.4% (N = 8) in the pre-intervention group and 1.6% (N = 3) in the post-intervention group: difference -2.7% (90% CI: -6.2 to 0.1).

CONCLUSIONS

As the upper boundary of the 90% CI does not exceed the predefined non-inferiority margin of +6%, it can be concluded that a premedication regimen without ranitidine is non-inferior to a premedication regimen with ranitidine.

CLINICAL TRIAL REGISTRATION

www.trialregister.nl ; NL8173.

Combining Gold Nanoparticles with Other Radiosensitizing Agents for Unlocking the Full Potential of Cancer Radiotherapy

About half of cancer patients (50%) receive radiotherapy (RT) for the treatment of local tumors. However, one of the main obstacles in RT is the close proximity of adjacent organs at risk, resulting in treatment doses being limited by significant tissue toxicity, hence preventing the necessary dose escalation that would guarantee local control. Effective local cancer therapy is needed to avoid progression of tumors and to decrease the development of systemic metastases which may further increase the possibility of resection. In an effort to do so, radiosensitizing agents are introduced to further increase damage to the tumor while minimizing normal tissue toxicity. Cisplatin and docetaxel (DTX) are currently being used as radiation dose enhancers in RT. Recent research shows the potential of gold nanoparticles (GNPs) as a radiosensitizing agent. GNPs are biocompatible and have been tested in phase I clinical trials. The focus will be on exploring the effects of adding other radiosensitizing agents such as DTX and cisplatin to the GNP-RT platform. Therefore, a combined use of local radiosensitizing agents, such as GNPs, with currently available radiosensitizing drugs could make a significant impact in future RT. The ultimate goal is to develop treatments that have limited or nonexistent side effects to improve the quality of life of all cancer patients.

Docetaxel and nedaplatin twice a week with concurrent definitive radiotherapy in inoperable esophageal squamous cell carcinoma: A phase I trial (GASTO-1021)

PURPOSE

This phase I trial aimed to determine the maximal tolerated dose (MTD) of incorporating a twice-weekly docetaxel and nedaplatin regimen into definitive concurrent chemoradiotherapy (CCRT) as radiosensitizers in patients with inoperable esophageal squamous cell carcinoma (ESCC).

METHODS

The CCRT regimen included docetaxel (5 mg/m², 10 mg/m², or 15 mg/m²) and nedaplatin (5 mg/m², 10 mg/m², or 15 mg/m²) twice-weekly based on the traditional 3 + 3 dose escalation strategy, and radiotherapy (64 Gy in 32 fractions). The primary goals were to determine the MTD of concurrent chemotherapy and the dose limiting toxicities (DLTs). In-field objective response rate (ORR) was investigated.

RESULTS

Fifteen patients had been recruited and analyzed. DLT involving persistent grade 3 esophagitis over 1 week was observed in all three patients (3/3) at dose level 3 (15 mg/m²), and two patients (2/6) experienced DLTs in the dose level 2 (10 mg/m²) due to esophageal fistula and persistent grade 3 esophagitis over 1 week, while one patient (1/6) treated at dose level 1 (5 mg/m²) exhibited DLT owing to Grade 3 increased liver enzymes, suggesting a MTD of 5 mg/m². The in-filed ORR was both 100% in all patients and those receiving MTD. The 1-year loco-regional recurrence-free survival rate was 83.3%, 83.3% and 66.7% in dose level 1, 2, and 3, respectively.

CONCLUSIONS

The MTD of twice-weekly docetaxel and nedaplatin regimen was 5 mg/m² in inoperable ESCC patients treated with definitive CCRT. Low dose concurrent docetaxel and nedaplatin showed promising radiosensitizing effect on in-filed disease control and good tolerability.

Intrinsic and Extrinsic Factors Affecting Microtubule Dynamics in Normal and Cancer Cells

Microtubules (MTs), highly dynamic structures composed of α- and β-tubulin heterodimers, are involved in cell movement and intracellular traffic and are essential for cell division. Within the cell, MTs are not uniform as they can be composed of different tubulin isotypes that are post-translationally modified and interact with different microtubule-associated proteins (MAPs). These diverse intrinsic factors influence the dynamics of MTs. Extrinsic factors such as microtubule-targeting agents (MTAs) can also affect MT dynamics. MTAs can be divided into two main categories: microtubule-stabilizing agents (MSAs) and microtubule-destabilizing agents (MDAs). Thus, the MT skeleton is an important target for anticancer therapy. This review discusses factors that determine the microtubule dynamics in normal and cancer cells and describes microtubule-MTA interactions, highlighting the importance of tubulin isoform diversity and post-translational modifications in MTA responses and the consequences of such a phenomenon, including drug resistance development.

Microtubule-targeting agents and their impact on cancer treatment

Microtubule-targeting agents (MTAs) constitute a diverse group of chemical compounds that bind to microtubules and affect their properties and function. Disruption of microtubules induces various cellular responses often leading to cell cycle arrest or cell death, the most common effect of MTAs. MTAs have found a plethora of practical applications in weed control, as fungicides and antiparasitics, and particularly in cancer treatment. Here we summarize the current knowledge of MTAs, the mechanisms of action and their role in cancer treatment. We further outline the potential use of MTAs in anti-metastatic therapy based on inhibition of cancer cell migration and invasiveness. The two main problems associated with cancer therapy by MTAs are high systemic toxicity and development of resistance. Toxic side effects of MTAs can be, at least partly, eliminated by conjugation of the drugs with various carriers. Moreover, some of the novel MTAs overcome the resistance mediated by both multidrug resistance transporters as well as overexpression of specific β-tubulin types. In anti-metastatic therapy, MTAs should be combined with other drugs to target all modes of cancer cell invasion.

Modulation of nanoparticle uptake, intracellular distribution, and retention with docetaxel to enhance radiotherapy

OBJECTIVE

One of the major issues in current radiotherapy (RT) is the normal tissue toxicity. A smart combination of agents within the tumor would allow lowering the RT dose required while minimizing the damage to healthy tissue surrounding the tumor. We chose gold nanoparticles (GNPs) and docetaxel (DTX) as our choice of two radiosensitizing agents. They have a different mechanism of action which could lead to a synergistic effect. Our first goal was to assess the variation in GNP uptake, distribution, and retention in the presence of DTX. Our second goal was to assess the therapeutic results of the triple combination, RT/GNPs/DTX.

METHODS

We used HeLa and MDA-MB-231 cells for our study. Cells were incubated with GNPs (0.2 nM) in the absence and presence of DTX (50 nM) for 24 h to determine uptake, distribution, and retention of NPs. For RT experiments, treated cells were given a 2 Gy dose of 6 MV photons using a linear accelerator.

RESULTS

Concurrent treatment of DTX and GNPs resulted in over 85% retention of GNPs in tumor cells. DTX treatment also forced GNPs to be closer to the most important target, the nucleus, resulting in a decrease in cell survival and increase in DNA damage with the triple combination of RT/ GNPs/DTX vs RT/DTX. Our experimental therapeutic results were supported by Monte Carlo simulations.

CONCLUSION

The ability to not only trap GNPs at clinically feasible doses but also to retain them within the cells could lead to meaningful fractionated treatments in future combined cancer therapy. Furthermore, the suggested triple combination of RT/GNPs/DTX may allow lowering the RT dose to spare surrounding healthy tissue.

ADVANCES IN KNOWLEDGE

This is the first study to show intracellular GNP transport disruption by DTX, and its advantage in radiosensitization.

A Novel Resveratrol Based Tubulin Inhibitor Induces Mitotic Arrest and Activates Apoptosis in Cancer Cells

Resveratrol is one of the most widely studied bioactive plant polyphenols which possesses anticancer properties. Previously we have reported synthesis, characterization and identification of a novel resveratrol analog, SS28. In the present study, we show that SS28 induced cytotoxicity in several cancer cell lines ex vivo with an IC₅₀ value of 3–5 μM. Mechanistic evaluation of effect of SS28 in non-small cell lung cancer cell line (A549) and T-cell leukemic cell line (CEM) showed that it inhibited Tubulin polymerization during cell division to cause cell cycle arrest at G2/M phase of the cell cycle at 12–18 h time period. Immunofluorescence studies confirmed the mitotic arrest upon treatment with SS28. Besides, we show that SS28 binds to Tubulin with a dissociation constant of 0.414 ± 0.11 μM. Further, SS28 treatment resulted in loss of mitochondrial membrane potential, activation of Caspase 9 and Caspase 3, leading to PARP-1 cleavage and finally cell death via intrinsic pathway of apoptosis. Importantly, treatment with SS28 resulted in regression of tumor in mice. Hence, our study reveals the antiproliferative activity of SS28 by disrupting microtubule dynamics by binding to its cellular target Tubulin and its potential to be developed as an anticancer molecule.

Effect of Solvent Water Molecules on Human Serum Albumin Complex-Docked Paclitaxel by MM-PBSA Method

Molecular modeling on solvation effect and interaction mechanism of the water molecules in the active site of protein affect significantly the interaction between protein and ligand. Detailed influence of water molecules in the active site of human serum albumin (HSA) on its paclitaxel complex as well as their interaction is essential for clinical studies. Molecular docking of both crystal-HSA and solvated-HSA with paclitaxel was performed in the present work. The docking result shows that paclitaxel is inserted more deeply in the binding pocket of crystal-HSA than in the same site of solvated-HSA, and more intermolecular H-bonds are formed in the shrunken binding site of solvated-HSA. The favorable docking energies also reflect that solvated-HSA model is more tightly integrated with paclitaxel than crystal-HSA. According to the MD results of solvated-HSA-paclitaxel, six intermolecular H-bonds have formed at the binding site, two of them linking with the water molecules. It proves that water molecules in the binding site have affected the interaction between protein and ligand significantly. The MD results for the two complexes also suggest that the solvated protein model will lead to a rather different binding complex.

PRP4K is a HER2-regulated modifier of taxane sensitivity

The taxanes are used alone or in combination with anthracyclines or platinum drugs to treat breast and ovarian cancer, respectively. Taxanes target microtubules in cancer cells and modifiers of taxane sensitivity have been identified in vitro, including drug efflux and mitotic checkpoint proteins. Human epidermal growth factor receptor 2 (HER2/ERBB2) gene amplification is associated with benefit from taxane therapy in breast cancer yet high HER2 expression also correlates with poor survival in both breast and ovarian cancer. The pre-mRNA splicing factor 4 kinase PRP4K (PRPF4B), which we identified as a component of the U5 snRNP also plays a role in regulating the spindle assembly checkpoint (SAC) in response to microtubule-targeting drugs. In this study, we found a positive correlation between PRP4K expression and HER2 status in breast and ovarian cancer patient tumors, which we determined was a direct result of PRP4K regulation by HER2 signaling. Knock-down of PRP4K expression reduced the sensitivity of breast and ovarian cancer cell lines to taxanes, and low PRP4K levels correlated with in vitro-derived and patient acquired taxane resistance in breast and ovarian cancer. Patients with high-grade serous ovarian cancer and high HER2 levels had poor overall survival; however, better survival in the low HER2 patient subgroup treated with platinum/taxane-based therapy correlated positively with PRP4K expression (HR = 0.37 [95% CI 0.15-0.88]; p = 0.03). Thus, PRP4K functions as a HER2-regulated modifier of taxane sensitivity that may have prognostic value as a marker of better overall survival in taxane-treated ovarian cancer patients.

Concentration-dependent radiosensitizing effect of docetaxel in esophageal squamous cell carcinoma cells

Taxanes, paclitaxel and docetaxel (DTX) are anticancer agents that exhibit cytotoxicity by inhibiting microtubule polymerization. They enhance the radiosensitivity of various cancers by blocking the cell cycle in the most radiosensitive G2/M phase. Recently, taxanes have been reported to have different mechanisms of action depending on dose intensity. However, the mechanism of the radio-enhancing effect of DTX in relation to the drug dose intensity is not clearly understood. In the present study, we experimentally investigated the radio-enhancing effects of various concentrations of DTX against esophageal squamous cell cancer (ESCC); KES cells were used for in vitro confirmation of the effective administration schedule for DTX in chemoradiotherapy involving ESCC. DTX enhanced radiation cell killing in a concentration-dependent manner in KES cells. High cytotoxic concentrations (>10 nM) of DTX strongly enhanced radiosensitivity. Low concentrations (<1 nM) of DTX that did not have a cytotoxic effect showed a radio-enhancing effect by inducing DNA double strand breaks and apoptosis after irradiation. Low and high concentrations of DTX induced radiosensitive G0/G1 and G2/M phase arrest, respectively in KES cells. Cells treated with high concentrations of DTX exhibited nuclear aggregation associated with apoptotic change. In contrast, cells treated with low concentrations of DTX displayed multi-nucleation or unequal division. In conclusion, enhancement of the radiosensitivity of ESCC cells by DTX was demonstrated, even using nanomolar concentrations that did not have a cytotoxic effect. DTX has different radio-enhancing mechanisms depending on its concentration. Therefore, weekly administration of DTX might effectively enhance radiation cytotoxicity in the treatment of ESCC.

Radiosensitization of malignant gliomas following intracranial delivery of paclitaxel biodegradable polymer microspheres

OBJECT

The aim of this study was to demonstrate that paclitaxel could function as a radiosensitizer for malignant glioma in vitro and in vivo.

METHODS

The radiosensitizing effect of paclitaxel was tested in vitro using the human U373MG and rat 9L glioma cell lines. Cell cycle arrest in response to paclitaxel exposure was quantified by flow cytometry. Cells were subsequently irradiated, and toxicity was measured using the clonogenic assay. In vivo studies were performed in Fischer 344 rats implanted with intracranial 9L gliosarcoma. Rats were treated with control polymer implants, paclitaxel controlled-release polymers, radiotherapy, or a combination of the 2 treatments. The study end point was survival.

RESULTS

Flow cytometry demonstrated G2-M arrest in both U373MG and 9L cells following 6-12 hours of paclitaxel exposure. The order in which the combination treatment was administered was significant. Exposure to radiation treatment (XRT) during the 6-12 hours after paclitaxel treatment resulted in a synergistic reduction in colony formation. This effect was greater than the effect from either treatment alone and was also greater than the effect of radiation exposure followed by paclitaxel. Rats bearing 9L gliosarcoma tumors treated with paclitaxel polymer administration followed by single-fraction radiotherapy demonstrated a synergistic improvement in survival compared with any other treatment, including radiotherapy followed by paclitaxel treatment. Median survival for control animals was 13 days; for those treated with paclitaxel alone, 21 days; for those treated with XRT alone, 21 days; for those treated with XRT followed by paclitaxel, 45 days; and for those treated with paclitaxel followed by XRT, more than 150 days (p < 0.0001).

CONCLUSIONS

These results indicate that paclitaxel is an effective radiosensitizer for malignant gliomas because it renders glioma cells more sensitive to ionizing radiation by causing G2-M arrest, and induces a synergistic response to chemoradiotherapy.

Taxanes in combination with biologic agents for ovarian and breast cancers

Taxane-based cytotoxic therapy is commonly prescribed for breast and ovarian cancers. Although these cancers are often sensitive to such therapy, clinical benefit and overall survival are limited owing to the development of chemoresistance and recurrence. Biologic agents that specifically target proteins of growth factor signaling pathways, which are hyperactivated in cancers, offer attractive targets for cancer therapeutics and may work synergistically with standard taxane-based chemotherapy to improve patient outcomes. We review clinical trials of biologic agents--angiogenic, tyrosine kinase, and antibody inhibitors--in combination with taxane-based therapy for ovarian and breast cancers. Many clinical trials have shown promising results. However, some biologic agents still need larger trials to assess safety and efficacy. As research into the heterogeneity and complexity of ovarian and breast cancers improves our understanding of the molecular pathways involved, there is no question that targeted therapies with biologic agents will expand the future array of available cancer therapeutics.

Caspase-2 is involved in cell death induction by taxanes in breast cancer cells

BACKGROUND

We studied the role of caspase-2 in apoptosis induction by taxanes (paclitaxel, novel taxane SB-T-1216) in breast cancer cells using SK-BR-3 (nonfunctional p53, functional caspase-3) and MCF-7 (functional p53, nonfunctional caspase-3) cell lines.

RESULTS

Both taxanes induced apoptosis in SK-BR-3 as well as MCF-7 cells. Caspase-2 activity in SK-BR-3 cells increased approximately 15-fold within 48 h after the application of both taxanes at the death-inducing concentration (100 nM). In MCF-7 cells, caspase-2 activity increased approximately 11-fold within 60 h after the application of taxanes (300 nM). Caspase-2 activation was confirmed by decreasing levels of procaspase-2, increasing levels of cleaved caspase-2 and the cleavage of caspase-2 substrate golgin-160. The inhibition of caspase-2 expression using siRNA increased the number of surviving cells more than 2-fold in MCF-7 cells, and at least 4-fold in SK-BR-3 cells, 96 h after the application of death-inducing concentration of taxanes. The inhibition of caspase-2 expression also resulted in decreased cleavage of initiator caspases (caspase-8, caspase-9) as well as executioner caspases (caspase-3, caspase-7) in both cell lines after the application of taxanes. In control cells, caspase-2 seemed to be mainly localized in the nucleus. After the application of taxanes, it was released from the nucleus to the cytosol, due to the long-term disintegration of the nuclear envelope, in both cell lines. Taxane application led to some formation of PIDDosome complex in both cell lines within 24 h after the application. After taxane application, p21WAF1/CIP1 expression was only induced in MCF-7 cells with functional p53. However, taxane application did not result in a significant increase of PIDD expression in either SK-BR-3 or MCF-7 cells. The inhibition of RAIDD expression using siRNA did not affect the number of surviving SK-BR-3 and MCF-7 cells after taxane application at all.

CONCLUSION

Caspase-2 is required, at least partially, for apoptosis induction by taxanes in tested breast cancer cells. We suggest that caspase-2 plays the role of an apical caspase in these cells. Caspase-2 seems to be activated via other mechanism than PIDDosome formation. It follows the release of caspase-2 from the nucleus to the cytosol.

Vascular disrupting activity and the mechanism of action of EHT 6706, a novel anticancer tubulin polymerization inhibitor

Tumor blood vessels are an important emerging target for anticancer therapy. Here, we characterize the in vitro antiproliferative and antiangiogenic properties of the synthetic small molecule, 7-ethoxy-4-(3,4,5-trimethoxybenzyl)isoquinolin-8-amine dihydrochloride, EHT 6706, a novel microtubule-disrupting agent that targets the colchicine-binding site to inhibit tubulin polymerization. At low nM concentrations, EHT 6706 exhibits highly potent antiproliferative activity on more than 60 human tumor cell lines, even those described as being drug resistant. EHT 6706 also shows strong efficacy as a vascular-disrupting agent, since it prevents endothelial cell tube formation and disrupts pre-established vessels, changes the permeability of endothelial cell monolayers and inhibits endothelial cell migration. Genome-wide transcriptomic analysis of EHT 6706 effects on human endothelial cells shows that the antiangiogenic activity elicits gene deregulations of antiangiogenic pathways. These findings indicate that EHT 6706 is a promising tubulin-binding compound with potentially broad clinical antitumor efficacy.

The prospective role of plant products in radiotherapy of cancer: a current overview

Treatment of cancer often requires exposure to radiation, which has several limitations involving non-specific toxicity toward normal cells, reducing the efficacy of treatment. Efforts are going on to find chemical compounds which would effectively offer protection to the normal tissues after radiation exposure during radiotherapy of cancer. In this regard, plant-derived compounds might serve as “leads” to design ideal radioprotectors/radiosensitizers. This article reviews some of the recent findings on prospective medicinal plants, phytochemicals, and their analogs, based on both in vitro and in vivo tumor models especially focused with relevance to cancer radiotherapy. Also, pertinent discussion has been presented on the molecular mechanism of apoptotic death in relation to the oxidative stress in cancer cells induced by some of these plant samples and their active constituents.

Characterization of the apoptotic response of human leukemia cells to organosulfur compounds

BACKGROUND

Novel therapeutic agents that selectively induce tumor cell death are urgently needed in the clinical management of cancers. Such agents would constitute effective adjuvant approaches to traditional chemotherapy regimens. Organosulfur compounds (OSCs), such as diallyl disulfide, have demonstrated anti-proliferative effects on cancer cells. We have previously shown that synthesized relatives of dysoxysulfone, a natural OSC derived from the Fijian medicinal plant, Dysoxylum richi, possess tumor-specific antiproliferative effects and are thus promising lead candidates.

METHODS

Because our structure-activity analyses showed that regions flanking the disulfide bond mediated specificity, we synthesized 18 novel OSCs by structural modification of the most promising dysoxysulfone derivatives. These compounds were tested for anti-proliferative and apoptotic activity in both normal and leukemic cells.

RESULTS

Six OSCs exhibited tumor-specific killing, having no effect on normal bone marrow, and are thus candidates for future toxicity studies. We then employed mRNA expression profiling to characterize the mechanisms by which different OSCs induce apoptosis. Using Gene Ontology analysis we show that each OSC altered a unique set of pathways, and that these differences could be partially rationalized from a transcription factor binding site analysis. For example, five compounds altered genes with a large enrichment of p53 binding sites in their promoter regions (p < 0.0001).

CONCLUSIONS

Taken together, these data establish OSCs derivatized from dysoxysulfone as a novel group of compounds for development as anti-cancer agents.

Cell death induced by novel fluorinated taxanes in drug-sensitive and drug-resistant cancer cells

The aim of this study is to compare the effects of new fluorinated taxanes SB-T-12851, SB-T-12852, SB-T-12853, and SB-T-12854 with those of the classical taxane paclitaxel and novel non-fluorinated taxane SB-T-1216 on cancer cells. Paclitaxel-sensitive MDA-MB-435 and paclitaxel-resistant NCI/ADR-RES human cancer cell lines were used. Cell growth and survival evaluation, colorimetric assessment of caspases activities, flow cytometric analyses of the cell cycle and the assessment of mitochondrial membrane potential, reactive oxygen species (ROS) and the release of cytochrome c from mitochondria were employed. Fluorinated taxanes have similar effects on cell growth and survival. For MDA-MB-435 cells, the C(50) of SB-T-12851, SB-T-12852, SB-T-12853 and SB-T-12854 was 3 nM, 4 nM, 3 nM and 5 nM, respectively. For NCI/ADR-RES cells, the C(50) of SB-T-12851, SB-T-12852, SB-T-12853, and SB-T-12854 was 20 nM, 20 nM, 10 nM and 10 nM, respectively. Selected fluorinated taxanes, SB-T-12853 and SB-T-12854, at the death-inducing concentrations (30 nM for MDA-MB-435 and 300 nM for NCI/ADR-RES) were shown to activate significantly caspase-3, caspase-9, caspase-2 and also slightly caspase-8. Cell death was associated with significant accumulation of cells in the G(2)/M phase. Cytochrome c was not released from mitochondria and other mitochondrial functions were not significantly impaired. The new fluorinated taxanes appear to use the same or similar mechanisms of cell death induction as compared with SB-T-1216 and paclitaxel. New fluorinated and non-fluorinated taxanes are more effective against drug-resistant cancer cells than paclitaxel. Therefore, new generation of taxanes, either non-fluorinated or fluorinated, are excellent candidates for further and detailed studies.

beta'-Hydroxy-alpha,beta-unsaturated ketones: A new pharmacophore for the design of anticancer drugs. Part 2

Novel antiproliferative beta'-acyloxy-alpha,beta-unsaturated ketones were obtained by means of an iron(III)-catalyzed multicomponent domino process (ABB' 3CR). The most active derivatives displayed GI(50) values in the range of 0.5-3.9 muM against a panel of representative human solid tumor cell lines: A2780, SW1573, HBL-100, T-47D and WiDr. Analysis of cells following 24 h exposure to these drugs showed cell cycle arrest in the S and G(2)/M phase, in a dose-dependent manner. Our data indicate that the beta'-acyloxy-alpha,beta-unsaturated ketones cause permanent damage to the cells and induce apoptosis.

Pharmacokinetic analysis of two different docetaxel dose levels in patients with non-small cell lung cancer treated with docetaxel as monotherapy or with concurrent radiotherapy

Background

Previous pharmacokinetic studies with docetaxel have mostly used 3-weekly (75 mg/m² and 100 mg/m²) or weekly regimens (35–40 mg/m²). The pharmacokinetics and radiosensitizing efficacy of weekly 20 mg/m² docetaxel, has however not been well characterized. We examined the pharmacokinetics of weekly docetaxel when administered with concurrent radiotherapy and compared the results with a 3-weekly 100 mg/m² regimen.

Methods

Thirty-four patients with non small cell lung cancer (NSCLC) were included in this study, 19 receiving 100 mg/m² docetaxel 3-weekly as single therapy, and 15 receiving 20 mg/m² docetaxel weekly with concurrent radiotherapy. A newly developed HPLC method was used for measuring docetaxel levels, capable of quantifying docetaxel in plasma down to the nanomolar level.

Results

The HPLC method showed detectable concentrations of docetaxel in plasma even after 72 hours. In the present study we have demonstrated that median docetaxel plasma levels of 3 nM can be obtained 72 hours after a dose of 20 mg/m².

Conclusion

The pharmacokinetics of docetaxel is characterized by great inter-individual variability and at some time points plasma concentrations for 20 mg/m² and 100 mg/m² docetaxel were overlapping. Extrapolation of these results indicates that radio sensitizing docetaxel concentrations may be present for as long as 1 week, thus supporting the use of 20 mg/m² weekly docetaxel.

Drug target interaction of tubulin-binding drugs in cancer therapy

Microtubules and their component protein, tubulin, constitute a popular target for the treatment of cancer. Many drugs that are presently used in clinics or in clinical trials and drugs that show promise as anticancer drugs bind to tubulin and microtubules. There are three conventional binding sites on beta-tubulin where many of these drugs bind. The binding properties, conformational changes upon binding, association constants and thermodynamic parameters for the drug-tubulin interaction on these three sites are discussed. The antiproliferative activities of these drugs and the possible correlation with the binding properties are also described.

Anti-angiogenic drugs: from bench to clinical trials

Angiogenesis, the generation of new capillaries through a process of pre-existing microvessel sprouting, is under stringent control and normally occurs only during embryonic and post-embryonic development, reproductive cycle, and wound repair. However, in many pathological conditions (solid tumor progression, metastasis, diabetic retinopathy, hemangioma, arthritis, psoriasis and atherosclerosis among others), the disease appears to be associated with persistent upregulated angiogenesis. The development of specific anti-angiogenic agents arises as an attractive therapeutic approach for the treatment of cancer and other angiogenesis-dependent diseases. The formation of new blood vessels is a complex multi-step process. Endothelial cells resting in the parent vessels are activated by an angiogenic signal and stimulated to synthesize and release degradative enzymes allowing endothelial cells to migrate, proliferate and finally differentiate to give rise to capillary tubules. Any of these steps may be a potential target for pharmacological intervention. In spite of the disappointing results obtained initially in clinical trials with anti-angiogenic drugs, recent reports with positive results in phases II and III trials encourage expectations in their therapeutic potential. This review discusses the current approaches for the discovery of new compounds that inhibit angiogenesis, with emphasis on the clinical developmental status of anti-angiogenic drugs.

Radiosensitization of colorectal carcinoma cell lines by histone deacetylase inhibition

Background

The tumor response to preoperative radiotherapy of locally advanced rectal cancer varies greatly, warranting the use of experimental models to assay the efficacy of molecular targeting agents in rectal cancer radiosensitization. Histone deacetylase (HDAC) inhibitors, agents that cause hyperacetylation of histone proteins and thereby remodeling of chromatin structure, may override cell cycle checkpoint responses to DNA damage and amplify radiation-induced tumor cell death.

Methods

Human colorectal carcinoma cell lines were exposed to ionizing radiation and HDAC inhibitors, and cell cycle profiles and regulatory factors, as well as clonogenicity, were analyzed.

Results

In addition to G₂/M phase arrest following irradiation, the cell lines displayed cell cycle responses typical for either intact or defective p53 function (the presence or absence, respectively, of radiation-induced expression of the cell cycle inhibitor p21 and subsequent accumulation of G₁ phase cells). In contrast, histone acetylation was associated with complete depletion of the G₁ population of cells with functional p53 but accumulation of both G₁ and G₂/M populations of cells with defective p53. The cellular phenotypes upon HDAC inhibition were consistent with the observed repression of Polo-like kinase-1, a regulatory G₂/M phase kinase. Following pre-treatment with HDAC inhibitors currently undergoing clinical investigation, the inhibitory effect of ionizing radiation on clonogenicity was significantly amplified.

Conclusion

In these experimental models, HDAC inhibition sensitized the tumor cells to ionizing radiation, which is in accordance with the concept of increased probability of tumor cell death when chromatin structure is modified.

Microtubule interactions with chemically diverse stabilizing agents: thermodynamics of binding to the paclitaxel site predicts cytotoxicity

The interactions of microtubules with most compounds described as stabilizing agents have been studied. Several of them (lonafarnib, dicumarol, lutein, and jatrophane polyesters) did not show any stabilizing effect on microtubules. Taccalonolides A and E show paclitaxel-like effects in cells, but they were not able to modulate in vitro tubulin assembly or to bind microtubules, which suggests that other factors are involved in their cellular effects. The binding constants of epothilones, eleutherobin, discodermolide, sarcodictyins, 3,17beta-diacetoxy-2-ethoxy-6-oxo-B-homo-estra-1,3,5(10)-triene, and dictyostatin to the paclitaxel site; the critical concentrations of ligand-induced assembly; and their cytotoxicity in carcinoma cells have been measured, and correlations between these parameters have been determined. The inhibition of cell proliferation correlates better with the binding enthalpy change than with the binding constants, suggesting that large, favorable enthalpic contribution to the binding is desired to design paclitaxel site drugs with higher cytotoxicity.

Radiation Modifiers: Treatment Overview and Future Investigations

Many radiosensitizers are in current clinical use. In addition, a myriad of potential new targeted therapies, which may also interact with radiation, are in clinical development. The clinical utility of new targeted therapies, in combination with existing radiation sensitizers (chemotherapies) requires further evaluation, as does the understanding of their acute and late radiation effects. Free radical scavengers appear to show promise as radioprotectors, but data for mucoprotection are less convincing.

Prospective evaluation of concurrent paclitaxel and radiation therapy after adjuvant doxorubicin and cyclophosphamide chemotherapy for Stage II or III breast cancer

PURPOSE

To evaluate the safety and feasibility of concurrent radiation therapy and paclitaxel-based adjuvant chemotherapy, given either weekly or every 3 weeks, after adjuvant doxorubicin and cyclophosphamide (AC).

METHODS AND MATERIALS

After definitive breast surgery and AC chemotherapy, 40 patients with operable Stage II or III breast cancer received protocol-based treatment with concurrent paclitaxel and radiation therapy. Paclitaxel was evaluated on 2 schedules, with treatment given either weeklyx12 weeks (60 mg/m2), or every 3 weeksx4 cycles (135-175 mg/m2). Radiation fields and schedules were determined by the patient's surgery and pathology. The tolerability of concurrent therapy was evaluated in cohorts of 8 patients as a phase I study.

RESULTS

Weekly paclitaxel treatment at 60 mg/m2 per week with concurrent radiation led to dose-limiting toxicity in 4 of 16 patients (25%), including 3 who developed pneumonitis (either Grade 2 [1 patient] or Grade 3 [2 patients]) requiring steroids. Efforts to eliminate this toxicity in combination with weekly paclitaxel through treatment scheduling and CT-based radiotherapy simulation were not successful. By contrast, dose-limiting toxicity was not encountered among patients receiving concurrent radiation with paclitaxel given every 3 weeks at 135-175 mg/m2. However, Grade 2 radiation pneumonitis not requiring steroid therapy was seen in 2 of 24 patients (8%) treated in such a fashion. Excessive radiation dermatitis was not observed with either paclitaxel schedule.

CONCLUSIONS

Concurrent treatment with weekly paclitaxel and radiation therapy is not feasible after adjuvant AC chemotherapy for early-stage breast cancer. Concurrent treatment using a less frequent paclitaxel dosing schedule may be possible, but caution is warranted in light of the apparent possibility of pulmonary injury.

A phase I and pharmacokinetic study of novel taxane BMS-188797 and cisplatin in patients with advanced solid tumours

This phase I study investigated the maximum tolerated dose and pharmacokinetics of a 3-weekly administration of BMS-188797, a paclitaxel derivate, at three dose levels (DLs) (80, 110 and 150 mg m(-2) DL), combined with cisplatin (standard dose 75 mg m(-2)). In 16 patients with advanced malignancies treated, one patient experienced dose-limiting febrile neutropenia, sepsis and severe colitis at the 150 mg m(-2) DL; at the 110 mg m(-2) DL one episode of dose-limiting grade 3 diarrhoea/nausea occurred. Grade 3/4 haematological toxicities were leucopenia/neutropenia; grade 3 nonhaematological toxicities were neuropathy, nausea, diarrhoea and stomatits. Objective response was seen in four patients, with three complete remissions in ovarian and cervical cancer patients. Pharmacokinetics of BMS-188797 appeared linear through the 110 mg m(-2), but not through the 150 mg m(-2) DL. The mean+/-SD values for clearance, distribution volume at steady state and terminal half-life during cycle 1 were 317+/-60 ml min(-1) m(-2), 258+/-96 l m(-2) and 30.8+/-7.7 h, respectively. The maximum tolerated and recommended phase II dose for BMS-188797 was 110 mg m(-2) (1-h infusion, every 3 weeks) combined with cisplatin 75 mg m(-2).

Cell cycle checkpoint signaling involved in histone deacetylase inhibition and radiation-induced cell death

In breast cancer, radiation has a central role in the treatment of brain metastasis, although tumor sensitivity might be limited. The tumor cell defense response to ionizing radiation involves activation of cell cycle checkpoint signaling. Histone deacetylase (HDAC) inhibitors, agents that cause hyperacetylation of histone proteins and thereby aberrations in the chromatin structure, may also override the DNA damage defense response and facilitate the radiation-induced mitotic cell death. In experimental metastasis models, the human breast carcinoma cell line MA-11 invariably disseminates to the central nervous system. We compared profiles of in vitro MA-11 cell cycle response to ionizing radiation and HDAC inhibition. After radiation exposure, the G2-M phase accumulation and the preceding repression of the G2 phase regulatory factors Polo-like kinase-1 and cyclin B1 required intact G2 checkpoint signaling through the checkpoint kinase CHK1, whereas the similar phenotypic changes observed with HDAC inhibition did not. MA-11 cells did not show radiation-induced expression of the G1 cell cycle inhibitor p21, indicative of a defective G1 checkpoint and consistent with a point mutation detected in the tumor suppressor TP53 gene. Increase in the p21 level, however, was observed with HDAC inhibition. Following pretreatment with the HDAC inhibitor, the efficiency of clonogenic regrowth after irradiation was reduced, which is in accordance with the concept of increased probability of mitotic cell death when the chromatin structure is disrupted. Among molecular cell cycle-targeted drugs currently in the pipeline for testing in early-phase clinical trials, HDAC inhibitors may have therapeutic potential as radiosensitizers.

Investigation of antitumor effects of synthetic epothilone analogs in human myeloma models in vitro and in vivo

26-Trifluoro-(E)-9,10-dehydro-12,13-desoxyepothilone B [Fludelone (Flu)] has shown broad antitumor activity in solid tumor models. In the present study, we showed, in vitro, that Flu significantly inhibited multiple myeloma (MM) cell proliferation (with 1-15 nM IC50), whereas normal human bone marrow stromal cells (HS-27A and HS-5 lines) were relatively resistant (10- to 15-fold higher IC50). Cell-cycle analysis demonstrated that Flu caused G2/M phase arrest and induced cell apoptosis. After Flu treatment, caspase-3, -8, and -9 were activated, cytochrome c and second mitochondrial-derived activator of caspase were released to the cytosol, and c-Jun N-terminal kinase was activated, indicating that mitochondria were involved in the apoptosis. Flu toxicity to human hematopoietic stem cells was evaluated by CD34+ cell-apoptosis measurements and hematopoietic-progenitor assays. There was no significant toxicity to noncycling human CD34+ cells. We compared the efficacy of Flu with the epothilone analog 12,13-desoxyepothilone B (dEpoB) in xenograft nonobese diabetic/severe combined immunodeficient mouse models with subcutaneous or disseminated MM. Flu caused tumor disappearance in RPMI 8226 subcutaneous xenografts after only five doses of the drug (20 mg/kg of body weight), with no sign of relapse after 100 d of observation. In a disseminated CAG MM model, mice treated with Flu had a significantly decreased tumor burden, as determined by bioluminescence imaging, and prolonged overall survival vs. mice treated with dEpoB or vehicle control, indicating that Flu may be a promising agent for MM therapy.

Amplification loop cascade for increasing caspase activity induced by docetaxel

The hierarchy of events accompanying induction of apoptosis by the microtubule inhibitor docetaxel was investigated in HL-60 human leukemia cells. Treatment of HL-60 cells with docetaxel resulted in the production of reactive oxygen species (ROS), activation of caspase-3 (-like) protease, c-Jun N-terminal kinase/stress-activated protein kinase (JNK/SAPK) activation, bcl-2 phosphorylation and apoptosis. Docetaxel elicited ROS production from NADPH oxidase as demonstrated by specific oxidase inhibitor diphenylene iodonium (DPI). ROS mediated the caspase-3 activation and apoptosis in HL-60 cells. The caspase inhibitor acetyl-Asp-Glu-Val-Asp-aldehyde (Ac-DEVD-CHO) effectively inhibited JNK/SAPK activation, bcl-2 phosphorylation and partially attenuated the ROS production induced by docetaxel. Docetaxel-induced bcl-2 phosphorylation was completely blocked by expression of dominant negative JNK or the JNK/SAPK inhibitor SP600125. Overexpression of bcl-2 partially prevented docetaxel-mediated ROS production and subsequent caspase-3 activation, thereby inhibiting apoptotic cell death. It is thus conferred that such sequent events as ROS production, caspase activation, JNK/SAPK activation, bcl-2 phosphorylation and the further generation of ROS should be parts of an amplification loop to increase caspase activity, thereby facilitating the apoptotic cell death process.

Interaction of epothilone analogs with the paclitaxel binding site: relationship between binding affinity, microtubule stabilization, and cytotoxicity

The interactions of epothilone analogs with the paclitaxel binding site of microtubules were studied. The influence of chemical modifications in the C15 side chain and in C12 on binding affinity and microtubule elongation was characterized. Modifications favorable for binding affinity are (1). a thiomethyl group at C21 of the thiazole side chain, (2). a methyl group at C12 in S configuration, (3). a pyridine side chain with C15 in S configuration, and (4). a cyclopropyl moiety between C12 and C13. The same modification in different ligands has similar effect on affinity, allowing good structure-affinity characterization. The correlation between binding, microtubule stabilization, and cytotoxicity of the compounds has been determined, showing differential effects of the modifications. The binding constants correlate well with IC(50) values, demonstrating that affinity measurements are a useful tool for drug design.

Macromolecular accessibility of fluorescent taxoids bound at a paclitaxel binding site in the microtubule surface

The macromolecular accessibility of the paclitaxel binding site in microtubules has been investigated using a fluorescent taxoid and antibodies against fluorescein, which cannot diffuse into the microtubule lumen. The formation of a specific ternary complex of microtubules, Hexaflutax (7-O-{N-[6-(fluorescein-4'-carboxamido)-n-hexanoyl]-l-alanyl}paclitaxel) and 4-4-20 IgG (a monoclonal antibody against fluorescein) has been observed by means of sedimentation and electron microscopy methods. The kinetics of binding of the antibody to microtubule-bound Hexaflutax has been measured. The quenching of the observed fluorescence is fast (k+ 2.26 +/- 0.25 x 10(6) m(-1) s(-1) at 37 degrees C), indicating that the fluorescein groups of Hexaflutax are exposed to the outer solvent. The velocity of the reaction is linearly dependent on the antibody concentration, indicating that a bimolecular reaction is being observed. Another fluorescent taxoid (Flutax-2) bound to microtubules has also been shown to be rapidly accessible to polyclonal antibodies directed against fluorescein. A reduced rate of Hexaflutax quenching by the antibody is observed in microtubule-associated proteins containing microtubules or in native cellular cytoskeletons. It can be concluded that the fluorescent taxoids bind to an outer site on the microtubules that is shared with paclitaxel. Paclitaxel would be internalized in a further step of binding to reach the known luminal site, this step being blocked in the case of the fluorescent taxoids. Because the fluorescent ligands are able to induce microtubule assembly, binding to the outer site should be enough to induce assembly by a preferential binding mechanism.

Human serum albumin: spectroscopic studies of the paclitaxel binding and proximity relationships with cisplatin and adriamycin

The interactions of anti-cancer drugs with blood constituents, particularly with serum albumin (HSA) may have a major influence on drug pharmacology and efficacy. In the present work the binding of paclitaxel (trade name Taxol) to human serum albumin and its effect on cisplatin and adriamycin interactions has been investigated through UV/visible, CD, fluorescence spectroscopy and the inductively couplet plasma atomic emission spectroscopy method. Displacement studies with use of bilirubin, as a competitive agent provided relevant information about the location of the binding site in HSA as well as the possible multidrug interactions.

Is extended volume external beam radiation therapy covering the anastomotic site beneficial in post-esophagectomy high risk patients?

BACKGROUND AND PURPOSE

To assess the impact of extended volume radiation therapy (RT) with anastomotic coverage on local control in high risk post-operative esophageal cancer patients.

PATIENTS AND METHODS

This is a retrospective study of high risk (T(3), T(4), nodes positive, with or without margin involvement) post-operative esophageal cancer patients treated at London Regional Cancer Centre from 1989 to 1999. After esophagectomy, all patients received adjuvant combined modality therapy consisting of four cycles of fluorouracil-based chemotherapy, and loco-regional RT with or without coverage of the anastomotic site. RT dose ranged from 45 to 60 Gy at 1.8-2.0 Gy/fraction with treatment fields tailored to the pathologic findings and location of the anastomosis. CT planning was used in all patients to design spinal cord sparing beam arrangements. First relapse rate (first incidence of an event), disease specific survival and overall survival were calculated by Chi-Square, Log-Rank, and Kaplan-Meier (K-M) methods.

RESULTS

During the study period, 72 patients had underwent esophagectomy and were considered for adjuvant chemoradiation therapy. Three patients were excluded due to disease progression prior to therapy. The 69 remaining patients formed the study cohort for the present analysis. The median age of the study group was 60 years (range 35-82 years). Pathologic stage distribution (AJCC 1997 staging) was T(2,3) N(1) in 94% patients, 65% of the cases were adenocarcinoma and had undergone transhiatal esophagectomy (86%) with positive/close margins in 34 (49%) patients. Median follow-up was 30.5 months (range 3.4-116.3 months). Two- and 5-year actuarial overall survivals rates were 50 and 31%, respectively. First relapse rate after adjuvant therapy was 63.7% (n = 44) and median time to relapse was 27.2 months. Anastomosis recurrence rates were 29% with small volume and 0% with extended volume RT (P = 0.041). Local and regional relapse occurred in 74.2% of patients treated with small volume RT compared to 15.4% in patients treated with extended volume RT (P < 0.001). After adjusting for resection margin status, the local control benefit of extended volume RT remained significant (P = 0.003). Treatment interruptions and late gastrointestinal toxicity were not significantly increased with the use of extended volume RT.

CONCLUSIONS

A significant decrease in local and regional relapse without added late toxicity was achieved with the use of extended volume RT encompassing the anastomotic site post-operatively in high risk esophageal cancer patients.

Paclitaxel–HSA interaction. Binding sites on HSA molecule

Paclitaxel (trade name Taxol) is one of the world's most effective anticancer drugs. It is used to treat several cancers including tumours of the breast, ovary and lung. In the present work the interaction of paclitaxel with human serum albumin (HSA) in aqueous solution at physiological pH has been investigated through CD, fluorescence spectroscopy and by the antibody precipitate test. Binding of paclitaxel to albumin impact on protein structure and it influences considerably albumin binding of other molecules like warfarin, heme or bilirubin. The paclitaxel-HSA interaction causes the conformational changes with the loss of helical stability of protein and local perturbation in the domain IIA binding pocket. The relative fluorescence intensity of the paclitaxel-bound HSA decreased, suggesting that perturbation around the Trp 214 residue took place. This was confirmed by the destabilization of the warfarin binding site, which includes Trp 214, and high affinity bilirubin binding site located in subdomain IIA.

Comparative pharmacokinetics of weekly and every-three-weeks docetaxel

PURPOSE

Weekly administration of docetaxel has demonstrated comparable efficacy together with a distinct toxicity profile with reduced myelosuppression, although pharmacokinetic data with weekly regimens are lacking. The comparative pharmacokinetics of docetaxel during weekly and once every 3 weeks (3-weekly) administration schedules were evaluated.

EXPERIMENTAL DESIGN

Forty-six patients received weekly docetaxel (35 mg/m(2)) as a 30-min infusion alone (n = 8) or in combination with irinotecan (n = 12), or in 3-weekly regimens, as a 1-h infusion at 60 mg/m(2) with doxorubicin (n = 10), 75 mg/m(2) alone (n = 9), or 100 mg/m(2) alone (n = 7). Serial blood samples were obtained immediately before and up to 21 days after the infusion. Plasma concentrations were measured by liquid chromatography-mass spectrometry and analyzed by compartmental modeling.

RESULTS

Mean +/- SD docetaxel clearance values were similar with weekly and 3-weekly schedules (25.2 +/- 7.7 versus 23.7 +/- 7.9 liter/h/m(2)); half-lives were also similar with both schedules of administration (16.5 +/- 11.2 versus 17.6 +/- 7.4 h). With extended plasma sampling beyond 24 h post-infusion, docetaxel clearance was 18% lower and the terminal half-life was 5-fold longer. At 35 mg/m(2), the mean +/- SD docetaxel concentration on day 8 was 0.00088 +/- 0.00041 microg/ml (1.08 +/- 0.51 nM) at 75 mg/m(2), concentrations on day 8, 15, and 22 were 0.0014 +/- 0.00043 microg/ml (1.79 +/- 0.53 nM), 0.00067 +/- 0.00025 microg/ml (0.83 +/- 0.31 nM), and 0.00047 +/- 0.00008 microg/ml (0.58 +/- 0.099 nM), respectively.

CONCLUSION

Docetaxel pharmacokinetics are similar for the weekly and 3-weekly regimens. Prolonged circulation of low nanomolar concentrations of docetaxel may contribute to the mechanism of action of docetaxel through suppression of microtubule dynamics and tumor angiogenesis and enhanced cell radiosensitivity in combined modality therapy.

Modulation of drug and radiation resistance in small cell lung cancer cells by paclitaxel

Small cell lung cancer (SCLC) responds to treatment with cisplatin and etoposide, but relapse is rapid and survival rates are low. Our aims were to determine the mechanisms of resistance and the potential for paclitaxel (Taxol) to overcome any drug or radiation resistance. To mimic clinical treatment, H69 SCLC cells, representative of the classic form of the disease, and H82 cells, with the phenotype of the more resistant variant disease, were treated intermittently with 100 ng/ml cisplatin or 500 ng/ml etoposide (approximate IC50 drug doses) to produce stable sublines. Drug and radiation resistance were determined using the MTT assay. Protein expression was determined by Western blot. The effect of paclitaxel on drug resistance was determined by cytotoxicity assays. Intermittent 4-day treatment with 100 ng/ml cisplatin caused 2- to 3-fold resistance to cisplatin (n=5; p<0.05), and 2- to 5-fold cross resistance to etoposide, alkylating drugs, the Vinca drugs and radiation. Resistance was mediated primarily by changes in glutathione metabolism and was not associated with changes in MRP2 transport protein. Treatment with etoposide (500 ng/ml) produced cells with 2-fold resistance to etoposide (n=5; p<0.05). Cross-resistance was limited and mediated by decreased topoisomerase IIalpha. Treatment of both drug-resistant sublines with a maximal non-cytotoxic dose of paclitaxel sensitized them to other drugs and to radiation, although this treatment had no effect on the parental H69 or H82 cells. We conclude that paclitaxel may play an important role in the treatment of refractory SCLC.

The national practice for patients receiving radiation therapy for carcinoma of the esophagus: results of the 1996-1999 Patterns of Care Study

PURPOSE

A Patterns of Care Study (PCS) was conducted to evaluate the standards of practice for patients receiving radiation therapy for esophageal cancer from 1996 to 1999. This study examined the evaluation and treatment schemes used during this time and compared these results to the PCS data obtained between 1992 and 1994 to identify any fundamental changes in national practice.

METHODS

A national survey was conducted using a two-stage cluster sampling technique. Specific information was collected on 414 patients with esophageal cancer who received radiotherapy (RT) as part of definitive or adjuvant management at 59 institutions. Patients were staged according to the 1983 AJCC. Eligibility criteria for case review included RT between 1996 and 1999, no evidence of distant metastasis (including CT evidence of either supraclavicular or celiac nodes >1 cm), squamous cell or adenocarcinoma histology, Karnofsky performance status >60, tumors in the thoracic esophagus with <2 cm extension into the stomach, and no prior malignancies within the last 5 years. Statistical analysis was performed on the database using SUDAAN software to accurately reflect the type of sampling technique used by PCS. For the purpose of this analysis, institutions were stratified as either large or small based on the number of new cases seen each year. For the purposes of comparison, the 1992-1994 PCS esophageal survey results were subjected to the same statistical procedures and tests.

RESULTS

The median age of patients was 64 years. Seventy-seven percent were male, and 23% were female. Karnofsky performance status was >or=80% in 85% of patients. The racial profile mirrors the previous survey with 75% Caucasian, 21% African-American, 3% Asian, and <1% Hispanic. A review of the histology revealed a nearly 50:50 split between squamous cell and adenocarcinoma. Sixteen percent were clinical Stage I, 39% clinical Stage II, and 33% clinical Stage III according to the 1983 AJCC system. Workup included endoscopy (96%), CT of the chest (87%), CT of the abdomen (75%), and esophagram (64%). Endoscopic ultrasound (EUS) was used in 18% of cases as compared to <2% in the original survey (p < 0.0001). Patients treated at large centers were more likely to undergo EUS than those treated at small centers (23% vs. 12%, p = 0.047). Fifty-six percent of patients received concurrent chemoradiation as definitive treatment. There was a significant increase in the use of concurrent chemoradiation before planned surgical resection as compared to the original survey (27% vs. 10%, p = 0.007). Other schemes included RT alone (10%), postoperative RT (1%), and postoperative chemoradiation (5%). Forty-six percent of patients with adenocarcinoma underwent trimodality therapy as compared to 19% with squamous cell carcinomas (p = 0.0002). Patients undergoing preoperative chemoradiation were more likely to have had an EUS. The median total dose of external RT was 50.4 Gy, and the median dose per fraction was 1.8 Gy. Brachytherapy was used in 6% of cases. The chemotherapy agents most commonly used included 5-fluorouracil (82%), cisplatin (67%), and paclitaxel (22%). Paclitaxel was more commonly employed as part of a preoperative chemoradiation regimen than in the setting of definitive chemoradiation (46% vs. 12%, p = 0.03). Compared to the original survey, paclitaxel use significantly increased between 1996 and 1999 (0.2% vs. 22%, p = 0.001).

CONCLUSIONS

The Patterns of Care Survey confirms the use of concurrent chemoradiation as part of the national standards of practice for the management of esophageal cancer patients. A comparison with the previous study documents the significant rise in the use of EUS, preoperative chemoradiation followed by surgery, and the increasing use of paclitaxel as part of a combined modality regimen.