Amifostine: chemotherapeutic and radiotherapeutic protective effects

Opaganib Protects against Radiation Toxicity: Implications for Homeland Security and Antitumor Radiotherapy

Exposure to ionizing radiation (IR) is a lingering threat from accidental or terroristic nuclear events, but is also widely used in cancer therapy. In both cases, host inflammatory responses to IR damage normal tissue causing morbidity and possibly mortality to the victim/patient. Opaganib, a first-in-class inhibitor of sphingolipid metabolism, has broad anti-inflammatory and anticancer activity. Opaganib elevates ceramide and reduces sphingosine 1-phosphate (S1P) in cells, conditions that increase the antitumor efficacy of radiation while concomitantly suppressing inflammatory damage to normal tissue. Therefore, opaganib may suppress toxicity from unintended IR exposure and improve patient response to chemoradiation. To test these hypotheses, we first examined the effects of opaganib on the toxicity and antitumor activity of radiation in mice exposed to total body irradiation (TBI) or IR with partial bone marrow shielding. Oral treatment with opaganib 2 h before TBI shifted the LD75 from 9.5 Gy to 11.5 Gy, and provided substantial protection against gastrointestinal damage associated with suppression of radiation-induced elevations of S1P and TNFα in the small intestines. In the partially shielded model, opaganib provided dose-dependent survival advantages when administered 4 h before or 24 h after radiation exposure, and was particularly effective when given both prior to and following radiation. Relevant to cancer radiotherapy, opaganib decreased the sensitivity of IEC6 (non-transformed mouse intestinal epithelial) cells to radiation, while sensitizing PAN02 cells to in vitro radiation. Next, the in vivo effects of opaganib in combination with radiation were examined in a syngeneic tumor model consisting of C57BL/6 mice bearing xenografts of PAN02 pancreatic cancer cells and a cross-species xenograft model consisting of nude mice bearing xenografts of human FaDu cells. Mice were treated with opaganib and/or IR (plus cisplatin in the case of FaDu tumors). In both tumor models, the optimal suppression of tumor growth was attained by the combination of opaganib with IR (± cisplatin). Overall, opaganib substantially protects normal tissue from radiation damage that may occur through unintended exposure or cancer radiotherapy.

Resveratrol as an Adjuvant for Normal Tissues Protection and Tumor Sensitization

Cancer is one of the most complicated diseases in present-day medical science. Yearly, several studies suggest various strategies for preventing carcinogenesis. Furthermore, experiments for the treatment of cancer with low side effects are ongoing. Chemotherapy, targeted therapy, radiotherapy and immunotherapy are the most common non-invasive strategies for cancer treatment. One of the most challenging issues encountered with these modalities is low effectiveness, as well as normal tissue toxicity for chemo-radiation therapy. The use of some agents as adjuvants has been suggested to improve tumor responses and also alleviate normal tissue toxicity. Resveratrol, a natural flavonoid, has attracted a lot of attention for the management of both tumor and normal tissue responses to various modalities of cancer therapy. As an antioxidant and anti-inflammatory agent, in vitro and in vivo studies show that it is able to mitigate chemo-radiation toxicity in normal tissues. However, clinical studies to confirm the usage of resveratrol as a chemo-radioprotector are lacking. In addition, it can sensitize various types of cancer cells to both chemotherapy drugs and radiation. In recent years, some clinical studies suggested that resveratrol may have an effect on inducing cancer cell killing. Yet, clinical translation of resveratrol has not yielded desirable results for the combination of resveratrol with radiotherapy, targeted therapy or immunotherapy. In this paper, we review the potential role of resveratrol for preserving normal tissues and sensitization of cancer cells in combination with different cancer treatment modalities.

The efficacy and safety of amifostine for the acute radiation syndrome

Introduction: A radiation countermeasure that can be used prior to radiation exposure to protect the population from the harmful effects of radiation exposure remains a major unmet medical need and is recognized as an important area for research. Despite substantial advances in the research and development for finding nontoxic, safe, and effective prophylactic countermeasures for the acute radiation syndrome (ARS), no such agent has been approved by the United States Food and Drug Administration (FDA). Area covered: Despite the progress made to improve the effectiveness of amifostine as a radioprotector for ARS, none of the strategies have resolved the issue of its toxicity/side effects. Thus, the FDA has approved amifostine for limited clinical indications, but not for non-clinical uses. This article reviews recent strategies and progress that have been made to move forward this potentially useful countermeasure for ARS. Expert opinion: Although the recent investigations have been promising for fielding safe and effective radiation countermeasures, additional work is needed to improve and advance drug design and delivery strategies to get FDA approval for broadened, non-clinical use of amifostine during a radiological/nuclear scenario.

Therapeutic targeting of CPT-11 induced diarrhea: a case for prophylaxis

CPT-11 (irinotecan), a DNA topoisomerase I inhibitor is one of the main treatments for colorectal cancer. The main dose limiting toxicities are neutropenia and late onset diarrhea. Though neutropenia is manageable, CPT-11 induced diarrhea is frequently severe, resulting in hospitalizations, dose reductions or omissions leading to ineffective treatment administration. Many potential agents have been tested in preclinical and clinical studies to prevent or ameliorate CPT-11 induced late onset diarrhea. It is predicted that prophylaxis of CPT-11 induced diarrhea will reduce sub-therapeutic dosing as well as hospitalizations and will eventually lead to dose escalations resulting in better response rates. This article reviews various experimental agents and strategies employed to prevent this debilitating toxicity. Covered topics include schedule/dose modification, intestinal alkalization, structural/chemical modification, genetic testing, anti-diarrheal therapies, transporter (ABCB1, ABCC2, BCRP2) inhibitors, enzyme (β-glucuronidase, UGT1A1, CYP3A4, carboxylesterase, COX-2) inducers and inhibitors, probiotics, antibiotics, adsorbing agents, cytokine and growth factor activators and inhibitors and other miscellaneous agents.

Improving therapeutic ratio in head and neck cancer with adjuvant and cisplatin-based treatments

Advanced head and neck cancers are difficult to manage despite the large treatment arsenal currently available. The multidisciplinary effort to increase disease-free survival and diminish normal tissue toxicity was rewarded with better locoregional control and sometimes fewer side effects. Nevertheless, locoregional recurrence is still one of the main reasons for treatment failure. Today, the standard of care in head and neck cancer management is represented by altered fractionation radiotherapy combined with platinum-based chemotherapy. Targeted therapies as well as chronotherapy were trialled with more or less success. The aim of the current work is to review the available techniques, which could contribute towards a higher therapeutic ratio in the treatment of advanced head and neck cancer patients.

Systematic review of amifostine for the management of oral mucositis in cancer patients

PURPOSE

The aim of this study was to review the available literature from 1966 until December 31, 2010 and define clinical practice guidelines for the use of amifostine for the prevention and treatment of oral mucositis in cancer patients.

METHODS

A systematic review was conducted by the Mucositis Study Group of the Multinational Association of Supportive Care in Cancer/International Society of Oral Oncology. The body of evidence for the use of amifostine, in each cancer treatment setting was assigned an evidence level. Based on the evidence level, one of the following three guideline determinations was possible: recommendation, suggestion, or no guideline possible.

RESULTS

Thirty papers were reviewed for evidence on amifostine as an intervention for oral mucositis. No guideline was possible for amifostine in any cancer treatment setting due to inadequate and conflicting evidence.

CONCLUSION

Review of the amifostine studies for the prevention and treatment of oral mucositis has found insufficient evidence to support its use in any cancer treatment setting for this purpose. Additional well-designed research is needed to clarify the role of amifostine as an intervention for oral mucositis.

Xanthoria elegans (Link) (lichen) extract counteracts DNA damage and oxidative stress of mitomycin C in human lymphocytes

Several lichen species have been used for medicinal purposes throughout the ages, and they are reported to be effective in the treatment of different disorders including ulcer and cancer. It is revealed that lichens may be easily accessible sources of natural drugs and possible food supplements after their safety evaluations. The main objective in this study was to evaluate the roles of aqueous extracts of Xanthoria elegans (at 25, 50 and 100 μg/ml) upon mitomycin C (MMC; at 10(-7) M) induced genotoxic and oxidative damages in cultured human lymphocytes. X. elegans were collected from the Erzurum and Artvin provinces (in Turkey) during August 2010. After the application of MMC and X. elegans extract (XEE), separate and together, human whole blood cultures were assessed by four genotoxicity end-points including chromosomal aberration, micronucleus, sister chromatid exchange (SCE) and 8-oxo-2-deoxyguanosine (8-OH-dG) assays. In addition, biochemical parameters [total antioxidant capacity (TAC) and total oxidative stress (TOS)] were examined to determine oxidative effects. According to our results, the frequencies of cytogenetic endpoints and 8-OH-dG levels were significantly increased by MMC compared with controls in human peripheral lymphocytes. MMC caused oxidative stress by altering TAC and TOS levels. On the contrary, XEE led to increases of TAC level without changing TOS level. XEE had no genotoxic effect. Furthermore, our findings revealed that MMC induced increases in the mean frequencies of four genotoxic indices were diminished by XEE in dose dependent manner, indicating its protective role towards cells from MMC exerted injury. In conclusion, the results obtained in the present study indicate for the first time that XEE is a potential source of natural antigenotoxicants.

ICRP publication 118: ICRP statement on tissue reactions and early and late effects of radiation in normal tissues and organs--threshold doses for tissue reactions in a radiation protection context

This report provides a review of early and late effects of radiation in normal tissues and organs with respect to radiation protection. It was instigated following a recommendation in Publication 103 (ICRP, 2007), and it provides updated estimates of 'practical' threshold doses for tissue injury defined at the level of 1% incidence. Estimates are given for morbidity and mortality endpoints in all organ systems following acute, fractionated, or chronic exposure. The organ systems comprise the haematopoietic, immune, reproductive, circulatory, respiratory, musculoskeletal, endocrine, and nervous systems; the digestive and urinary tracts; the skin; and the eye. Particular attention is paid to circulatory disease and cataracts because of recent evidence of higher incidences of injury than expected after lower doses; hence, threshold doses appear to be lower than previously considered. This is largely because of the increasing incidences with increasing times after exposure. In the context of protection, it is the threshold doses for very long follow-up times that are the most relevant for workers and the public; for example, the atomic bomb survivors with 40-50years of follow-up. Radiotherapy data generally apply for shorter follow-up times because of competing causes of death in cancer patients, and hence the risks of radiation-induced circulatory disease at those earlier times are lower. A variety of biological response modifiers have been used to help reduce late reactions in many tissues. These include antioxidants, radical scavengers, inhibitors of apoptosis, anti-inflammatory drugs, angiotensin-converting enzyme inhibitors, growth factors, and cytokines. In many cases, these give dose modification factors of 1.1-1.2, and in a few cases 1.5-2, indicating the potential for increasing threshold doses in known exposure cases. In contrast, there are agents that enhance radiation responses, notably other cytotoxic agents such as antimetabolites, alkylating agents, anti-angiogenic drugs, and antibiotics, as well as genetic and comorbidity factors. Most tissues show a sparing effect of dose fractionation, so that total doses for a given endpoint are higher if the dose is fractionated rather than when given as a single dose. However, for reactions manifesting very late after low total doses, particularly for cataracts and circulatory disease, it appears that the rate of dose delivery does not modify the low incidence. This implies that the injury in these cases and at these low dose levels is caused by single-hit irreparable-type events. For these two tissues, a threshold dose of 0.5Gy is proposed herein for practical purposes, irrespective of the rate of dose delivery, and future studies may elucidate this judgement further.

Effects of potential dietary inhibitors of endogenous DNA damage on mutagenesis and lipid peroxidation in lacZ mice

The effects of a nine month administration of dietary: (1) 3H-1,2-dithiole-3-thione (D3T), (2) N-acetylcysteine (NAC), (3) antioxidant vitamin mix, (vitamin C+E), (4) free radical scavenger, amifostine, and (5) calorie restriction, (CR), on mutagenesis and lipid peroxidation in lung, kidney, spleen and liver of lacZ transgenic mice were examined. These agents/diets were chosen because they might inhibit certain proposed mechanisms of endogenous damage to DNA. The agents were added to a high fat, reduced antioxidant AIN-76 diet, to better approximate a Western style diet than the conventional AIN-76 diet. As the lacZ gene is not expressed, mutations in that gene are neutral, and simply accumulate over time. The mutant fractions in control mice increased about 50-100%. Most of the agents inhibited to various extents the age-related increase in mutagenesis in lung, kidney, and/or spleen, but no inhibition was observed in liver. There was no significant effect of age on lipid peroxidation levels in controls, possibly reflecting steady state turnover of lipid peroxidation products. Almost all of the treatments except D3T inhibited lipid peroxidation in most organs to different degrees. The vitamin C+E mix was the most effective at inhibiting lipid peroxidation, but a single most effective inhibitor of mutagenesis could not be discerned. Some associations were observed between the reduction in lipid peroxidation and the inhibition of mutagenesis. The results are consistent with a partial role for oxidative stress in the age-related increase in mutagenesis. These observations may have implications for chemoprevention of carcinogenesis.

Protective effect of melatonin against mitomycin C-induced genotoxic damage in peripheral blood of rats

Mitomycin C (MMC) generates free radicals when metabolized. We investigated the effect of melatonin against MMC-induced genotoxicity in polychromatic erythrocytes and MMC-induced lipid peroxidation in brain and liver homogenates. Rats (N = 36) were classified into 4 groups: control, melatonin, MMC, and MMC + melatonin. Melatonin and MMC doses of 10 mg/kg and 2 mg/kg, respectively, were injected intraperitoneally. Peripheral blood samples were collected at 0, 24, 48, 72, and 96 hours posttreatment and homogenates were obtained at 96 hours posttreatment. The number of micronucleated polychromatic erythrocytes (MN-PCE) per 1000 PCE was used as a genotoxic marker. Malondialdehyde (MDA) plus 4-hydroxyalkenal (4-HDA) levels were used as an index of lipid peroxidation. The MMC group showed a significant increase in MN-PCE at 24, 48, 72, and 96 hours that was significantly reduced with melatonin begin coadministrated. No significant differences were found in lipid peroxidation. Our results indicate that MMC-induced genotoxicity can be reduced by melatonin.

H4 histamine receptors mediate cell cycle arrest in growth factor-induced murine and human hematopoietic progenitor cells

The most recently characterized H4 histamine receptor (H4R) is expressed preferentially in the bone marrow, raising the question of its role during hematopoiesis. Here we show that both murine and human progenitor cell populations express this receptor subtype on transcriptional and protein levels and respond to its agonists by reduced growth factor-induced cell cycle progression that leads to decreased myeloid, erythroid and lymphoid colony formation. H4R activation prevents the induction of cell cycle genes through a cAMP/PKA-dependent pathway that is not associated with apoptosis. It is mediated specifically through H4R signaling since gene silencing or treatment with selective antagonists restores normal cell cycle progression. The arrest of growth factor-induced G1/S transition protects murine and human progenitor cells from the toxicity of the cell cycle-dependent anticancer drug Ara-C in vitro and reduces aplasia in a murine model of chemotherapy. This first evidence for functional H4R expression in hematopoietic progenitors opens new therapeutic perspectives for alleviating hematotoxic side effects of antineoplastic drugs.

Amifostine (WR2721) confers DNA protection to in vivo cisplatin-treated murine peripheral blood leukocytes

Amifostine [S-2-3-aminopropyl amino ethyl phosphorotioic acid], a modulator agent for antineoplastic drugs involved in free radicals generation has given controversial results in cisplatin treated leukocytes in vitro. We have evaluated the amifostine protection over leukocytes in vivo, using comet assay. Groups of five OF1 male mice were given one of three doses of amifostine (56, 105 and 200 mg/Kg) after a cisplatin single injection (10 mg/Kg). Serum malonyldialdehyde levels, catalase and superoxide dismutase activity were also evaluated. Amifostine showed significant DNA protection (p< 0.01) at the two lower doses evaluated. Malonyldialdehyde decreased in all amifostine treatments with respect to cisplatin while antioxidant enzyme activities remained unchanged. However, DNA migration increased with the highest amifostine dose; in fact highest dose of amifostine did no protect damage caused by cisplatin this result have implications on amifostine treatment schedules in clinical practice.

Pharmacologic normal tissue protection in clinical radiation oncology: focus on amifostine

BACKGROUND

Radiation toxicity is an important problem that limits treatment intensity and adversely affects patients' quality of life. Amifostine is a cytoprotector that can reduce toxicity and potentially improve the therapeutic ratio of radiotherapy.

OBJECTIVE

To discuss the role of amifostine in modern radiotherapy and compare and contrast with alternative approaches to reducing radiation toxicity.

METHODS

We conducted a literature search through Medline to identify randomized clinical trials pertaining to keyword 'amifostine'. We also consulted reviews, book chapters and selected articles regarding amifostine and normal tissue protection.

RESULTS/CONCLUSION

Amifostine is an effective normal tissue protector with level I evidence supporting its use in head and neck and gynecologic cancers but studies in other disease sites, although promising, are inconclusive. Further study is needed to demonstrate conclusively the benefits of wider amifostine use.

A review on oxaliplatin-induced peripheral nerve damage

Platinum compounds are a class of chemotherapy agents that posses a broad spectrum of activity against several solid malignancies. Oxaliplatin (OXL) is a third-generation organoplatinum compound with significant activity mainly against colorectal cancer (CRC). Peripheral neuropathy is a well recognized toxicity of OXL, usually resulting in dose modification. OXL induces two types of peripheral neuropathy; acute and chronic. The acute oxaliplatin-induced peripheral neuropathy (OXLIPN) may be linked to the rapid chelation of calcium by OXL-induced oxalate and OXL is capable of altering the voltage-gated sodium channels through a pathway involving calcium ions. On the other hand, decreased cellular metabolism and axoplasmatic transport resulting from the accumulation of OXL in the dorsal root ganglia cells is the most widely accepted mechanism of chronic oxaliplatin-induced peripheral neuropathy (OXLIPN). As a result, OXL produces a symmetric, axonal, sensory distal primary neuronopathy without motor involvement. The incidence of OXLIPN is usually related to various risk factors, including treatment schedule, dosage, cumulative dose and time of infusion. The assessment of OXLIPN is primarily based on neurologic clinical examination and quantitative methods, such as nerve conduction study. To date, several neuroprotective agents including thiols, neurotrophic factors, anticonvulsants and antioxidants have been tested for their ability to prevent OXLIPN. However, the clinical data are still controversial. We herein review and discuss the pathogenesis, incidence, risk factors, diagnosis, characteristics and management of OXLIPN. We also highlight areas of future research.

Effect of radioprotector indralin on carboplatinum hemotoxicity

A decrease in carboplatinum hemotoxicity was detected in experiments on C57B1 mice treated with the drug in combination with indralin (urgent radioprotector). Carboplatinum in a dose of 125 mg/kg, injected intraperitoneally, caused 80-100% death; the median term of death was 6 days (3-17). Single oral dose of indralin (100 mg/kg) during the 1st min or 15 min after carboplatinum injection (125 mg/kg) increased animal survival by 40.0-46.7% by day 20 of the experiment primarily during the period of manifest hemotoxicity (days 7-17), indralin injected 1, 2, or 4 h after carboplatinum exhibited no chemoprotective effect.

Peripheral neuropathy induced by microtubule-stabilizing agents

Microtubule-stabilizing agents (MTSAs), including the taxanes and epothilones, are effective chemotherapeutic agents for the treatment of many cancers. Neuropathy is a major adverse effect of MTSA-based chemotherapy, with severe peripheral neuropathy (grade 3 or 4) occurring in as many as 30% of patients treated with a MTSA. MTSA-induced neuropathy usually resolves gradually after cessation of the treatment. The most reliable method to accurately assess MTSA-induced neuropathy is by clinical evaluation, although additional techniques are being developed and evaluated. Among MTSA-induced neuropathy, the most extensively studied is that induced by taxanes; such a neuropathy usually presents as sensory neuropathy and is more common with paclitaxel than docetaxel. The incidence of MTSA-induced neuropathy seems to depend on the MTSA dose per treatment cycle, the schedule of treatment, and the duration of the infusion. Although there have been several small clinical trials with neuroprotective agents, early recognition and supportive care are the best approaches for prevention and management of MTSA-induced neuropathy. In the future, research should focus on elucidating the mechanism of MTSA-induced neuropathy, developing reliable in vivo and in vitro preclinical models to study MTSA-induced neuropathy, developing a more reliable grading system for MTSA-induced neuropathy, developing more reliable methods for evaluating MTSA-induced neuropathy, and evaluating the efficacy of potential neuroprotective agents in clinical trials.

The effects of amifostine and dexamethasone on brain tissue lipid peroxidation during oxygen treatment of carbon monoxide-poisoned rats

The mechanisms of injury of, and methods of treating patients with, carbon monoxide (CO) poisoning are poorly understood. Besides the hypoxic degenerative effects of CO, reoxygenation injury may play an important role. Amifostine (Ami), which is most often used in radiotherapy for its tissue protective characteristics, may offer benefits. In this study, investigators evaluated the effectiveness of various treatments in a CO-poisoned rat model. A total of 36 Wistar rats were randomly assigned to 1 of 6 groups (n=6 each), including control and poisoned groups exposed to CO at 2000 ppm (v/v) for 1 h, followed by various 1-h treatments: group C (control), group COair (ambient air), group CO-NBO (normobaric 100% oxygen), group CO-HBO (hyperbaric oxygen with 3 atmospheres absolute [3 ATA]), group CO-NBO-Ami (normobaric oxygen with intraperitoneal [i.p.] injection of amifostine 250 mg/kg body weight [bw]), and group CO-70O (70% O2 and 5% CO2 with dexamethasone 10 mg/kg bw, i.p.). Blood gas analysis, carboxyhemoglobin determination, brain tissue lipid peroxidation, and glutathione peroxidase (GSHPx), superoxide dismutase (SOD), lactate dehydrogenase (LDH), and creatine kinase (CK) activities were evaluated. Carboxyhemoglobin concentration in the air-treated group was 44+/-2%; it decreased to the control level with all oxygen treatments. Brain tissue GSH-Px and SOD measurements did not change. The activity of LDH in group CO-HBO and the activities of LDH and CK in group CO-70O were similar to those of group C. Lipid peroxides were high in ambient air and normobaric oxygen, but HBO, amifostine with oxygen, or 70% O2 reduced these to control levels (P<.05).

Inefficient cleavage of palmitoyl-protein thioesterase (PPT) substrates by aminothiols: implications for treatment of infantile neuronal ceroid lipofuscinosis

Infantile neuronal ceroid lipofuscinosis (INCL, also known as infantile Batten disease) is a devastating neurodegenerative disorder caused by deficiency in the lysosomal enzyme palmitoyl-protein thioesterase (PPT, or CLN1), which functions to remove long-chain fatty acids from cysteine residues in proteins. A previous study suggested that the drug cysteamine, a simple aminothiol used in the treatment of cystinosis, may have utility in the treatment of INCL. In the current study, we compared the catalytic rate constants for the conversion of palmitoyl-CoA (a PPT substrate) and cystine (which accumulates in cystinosis) by cysteamine. We found that while cysteamine can react with palmitoyl-CoA, the rate constant is 10(3)-fold less than the reaction with cystine. Structure-activity studies suggested that it is the thiolate ion that is reactive in the cleavage reaction and that the amino group probably facilitates lysosomal entry. A modest effect of cysteamine (and two related aminothiols, WR 1065 and dimethylaminoethanethiol, DMAET) on PPT substrate accumulation in INCL lymphoblasts was observed. However, at optimum concentration a paradoxical increase in saposin immunoreactivity was seen, indicating possible lysosomal dysfunction. Improvements are needed in the design of small molecules for the treatment of INCL disease.

Checkpoint kinase inhibitors: SAR and radioprotective properties of a series of 2-arylbenzimidazoles

The discovery of a series of novel, potent, and highly selective inhibitors of the DNA damage control kinase chk2 is disclosed. Here we report the first SAR study around inhibitors of this kinase. High-throughput screening of purified human chk2 led to the identification of a novel series of 2-arylbenzimidazole inhibitors of the kinase. Optimization was facilitated using homology models of chk2 and docking of inhibitors, leading to the highly potent 2-arylbenzimidazole 2h (IC(50) 15 nM). Compound 2h is an ATP-competitive inhibitor of chk2 that dose dependently protects human CD4(+) and CD8(+) T-cells from apoptosis due to ionizing radiation. This work suggests that a selective small molecule inhibitor of chk2 could be a useful adjuvant to radiotherapy, increasing the therapeutic window of such treatment.

Radiopharmaceutical model using99mTc-MIBI to evaluate amifostine protection against doxorubicin cardiotoxicity in rats

The aim of our study was to use an in vivo radiopharmaceutical model to investigate the cytoprotective effect of amifostine against doxorubicin-induced cardiotoxicity. Male Wistar rats were randomly divided into four groups (n = 6): 1) Saline (control); 2) Doxorubicin (DOX; 10 mg/ kg(-l) intraperitoneally); 3) Amifostine (AMI; 200 mg/kg(-1) intraperitoneally); 4) Doxorubicin plus amifostine (DOX + AMI). Amifostine was injected 30 minutes before doxorubicin in Group 4. 99mTc-MIBI, 20 MBq/0.2 ml(-1), was injected through the tail vein 72 hours after the drug administration. Rats were killed and samples of myocardium were removed by dissection 60 minutes after the injection of radiopharmaceutical. Radioactivity in each organ sample was counted using a Cd(Te) detector equipped with RAD 501 single-channel analyzer. The percent radioactivity was expressed as a percentage of the injected dose per gram of tissue (%ID/g(-1)). The %ID/g(-1) activity was calculated by dividing the activity in each sample by the total activity injected and mass of each organ. 99mTc-MIBI uptake as %ID/g(-1) was 1.194 +/- 0.502 and 0.980 +/- 0.199 in the control and AMI groups, respectively. Doxorubicin administration resulted in a significant increase in %ID/ g(-1) (3.285 +/- 0.839) (p < 0.05). Amifostine administration 30 minutes before doxorubicin injection resulted a significant decrease in %ID/g(-1) (2.160 +/- 0.791) (p < 0.05) compared with doxorubicin alone. The results showed that amifostine significantly attenuated doxorubicin-induced cardiotoxicity.

Time dependent protection of amifostine from renal and hematopoietic cisplatin induced toxicity

Efficacy of chemotherapy may be maximized and its toxicity can be minimized if drugs would be administered at specified daily times. The present study was aimed to examine if the protection of amifostine against cisplatin toxicity is time dependent. Amifostine is an organic thiophosphate that protects selectively normal tissues, but not tumors, against the cytotoxicity of DNA binding chemotherapeutic agents such as cisplatin. ICR male mice which were entrained to Light:Dark (L:D) 14:10 were injected (intrapritoneal bolus) for 5 consecutive days with either: cisplatin, cisplatin plus amifostine (administered 30 minutes prior to cisplatin). Injections were given at either 08:00, 13:00, 20:00 or 01:00. Five days later, on day 10, each set of mice was sacrificed (at the same hour corresponds to the injection hour), blood count, blood creatinine and blood urea nitrogen (BUN) were assayed. Cisplatin treated mice exhibited nephrotoxicity, as indicated by increased blood urea nitrogen values and by high blood urea nitrogen to creatinine ratios, as well as myelotoxicity that was indicated by low levels of hemoglobin and platelets. Co-administration of amifostine-cisplatin reversed both, the nephrotoxicity of cisplatin, and its myelosuppressive effects. For BUN, hemoglobin and platelets, maximal protections were observed at 08:00, (p <0.05, p <0.01 and p <0.01 respectively). For BUN/Cr ratio (p <0.05), maximal protections was observed at 13:00. These findings show that amifostine exhibits time dependent protection against cisplatin toxicity and thus it is recommended to use the protector when treatments are given during morning hours. The results also further validate the notion that chronochemotherapy is advantageous at least in reducing drug toxicity and thus should be integrated in the design of clinical protocols.

Chemotherapy-induced peripheral neuropathy: pathogenesis and emerging therapies

Peripheral neuropathy is a major dose-limiting side effect of many chemotherapeutic agents. The type and degree of neuropathy depend on the chemotherapy drug, dose-intensity, and cumulative dose. Disabling peripheral neuropathy has a significant negative impact on quality of life. Accordingly, a reliable assessment of chemotherapy-induced peripheral neurotoxicity is necessary, especially if potential neuroprotective agents are to be investigated. Chemoprotectants are agents that have been developed to ameliorate the toxicity associated with cytotoxic drugs. They aim to provide site-specific protection for normal tissues, without compromising antitumor efficacy. Several chemoprotectant compounds have been studied in recent clinical trials. These trials must include sufficient dose-limiting events for study and assessment of both toxicity and antitumor effect. A future avenue of investigation includes the identification of patients at higher risk for the development of peripheral neuropathy based on their genotype. Identification of these higher-risk patients may enable us to devise prevention strategies prior to the onset of this potentially debilitating complication.

Enzyme-catalyzed activation of anticancer prodrugs

The rationale fo the development of prodrugs relies upon delivery of higher concentrations of a drug to target cells compared to administration of the drug itself. In the last decades, numerous prodrugs that are enzymatically activated into anti-cancer agents have been developed. This review describes the most important enzymes involved in prodrug activation notably with respect to tissue distribution, up-regulation in tumor cells and turnover rates. The following endogenous enzymes are discussed: aldehyde oxidase, amino acid oxidase, cytochrome P450 reductase, DT-diaphorase, cytochrome P450, tyrosinase, thymidylate synthase, thymidine phosphorylase, glutathione S-transferase, deoxycytidine kinase, carboxylesterase, alkaline phosphatase, beta-glucuronidase and cysteine conjugate beta-lyase. In relation to each of these enzymes, several prodrugs are discussed regarding organ- or tumor-selective activation of clinically relevant prodrugs of 5-fluorouracil, axazaphosphorines (cyclophosphamide, ifosfamide, and trofosfamide), paclitaxel, etoposide, anthracyclines (doxorubicin, daunorubicin, epirubicin), mercaptopurine, thioguanine, cisplatin, melphalan, and other important prodrugs such as menadione, mitomycin C, tirapazamine, 5-(aziridin-1-yl)-2,4-dinitrobenzamide, ganciclovir, irinotecan, dacarbazine, and amifostine. In addition to endogenous enzymes, a number of nonendogenous enzymes, used in antibody-, gene-, and virus-directed enzyme prodrug therapies, are described. It is concluded that the development of prodrugs has been relatively successful; however, all prodrugs lack a complete selectivity. Therefore, more work is needed to explore the differences between tumor and nontumor cells and to develop optimal substrates in terms of substrate affinity and enzyme turnover rates fo prodrug-activating enzymes resulting in more rapid and selective cleavage of the prodrug inside the tumor cells.

Amifostine has antiangiogenic properties in vitro by changing the redox status of human endothelial cells

Amifostine is a broad-spectrum cytoprotective agent, selective for normal tissues. It is a pro-drug metabolised to the free thiol WR-1065 that may act as a scavenger of free radicals, generated in tissues exposed to chemotherapeutic agents or radiation. WR-1065 can be further oxidized to its symmetric disulfide WR-33278 or degraded to hydrogen peroxide (H2O2). Both WR-1065 and WR-33278 resemble endogenous polyamines. Although amifostine is used in some cases in the clinic, there are only few studies concerning its actions at the cellular level. We have previously shown that amifostine inhibits angiogenesis in vivo, affecting the expression of several angiogenic genes. In the present work, we studied the effect of amifostine on human umbilical vein endothelial cell (HUVEC) functions in vitro, in order to further clarify its mechanism(s) of action. Amifostine increased HUVEC proliferation, an effect that was reversed by the intracellular H2O2 scavenger sodium pyruvate, agents that increase intracellular cAMP levels and L-valine. On the other hand, amifostine decreased HUVEC migration, an effect that was reversed by L-valine or L-arginine but not sodium pyrouvate. The decrease in migration was in line with decreased tube formation on matrigel and decreased amounts of metalloproteinase-2 released into the culture medium of HUVEC. Finally, amifostine reduced tyrosine nitration of the cytoskeletal proteins actin and alpha-tubulin in a time dependent manner. This last action could be due to the reduced production of nitric oxide (NO) or to other not yet identified mechanisms. Collectively, our results suggest that amifostine acts on endothelial cells through pathways that affect the redox status of the cells, either by producing H2O2 or by modulating NO production.

The potential influence of cell protectors for dose escalation in cancer therapy: an analysis of amifostine

The attempt to increase the therapeutic ratio in an effort to improve survival or quality of life is the goal of modern cancer therapy. It is commonly accepted that local and systemic tumor control would increase if the dose intensity of antineoplastic drugs, radiation therapy, or the combination were increased. Radiation dose escalation using intensity-modulated radiation therapy (IMRT), accelerated or hypofractionated radiation schemes, and multidrug chemotherapy regimens are being used to try to increase tumor kill while inflicting minimal injury to normal tissue. Modern chemoradiation techniques have led to improved local regional control and increased cure rates, but the potentially severe and debilitating adverse effects of the therapies prevent them from reaching the ultimate goal of curing the disease while leaving the patient with a good quality of life. Cell protectants such as amifostine function by reducing the effects of therapy on normal cells while maintaining tumor sensitivity to the therapy. In various studies, amifostine has been analyzed and appears to be a potentially powerful adjuvant to current cancer therapy. Administering amifostine may allow dose escalation with less or equal risk to surrounding normal tissues. This could improve therapeutic efficacy, survival, and quality of life for cancer patients.

Targeted therapies in myeloid leukemia

Targeted therapies for hematological malignancies have come of age since the advent of all trans retinoic acid (ATRA) for treating APL and STI571/Imatinib Mesylate/Gleevec for CML. There are good molecular targets for other malignancies and several new drugs are in clinical trials. In this review, we will concentrate on individual abnormalities that exist in the myelodysplastic syndromes (MDS) and myeloid leukemias that are targets for small molecule therapies (summarised in Fig. 1). We will cover fusion proteins that are produced as a result of translocations, including BCR-ABL, the FLT3 tyrosine kinase receptor and RAS. Progression of diseases such as MDS to secondary AML occur as a result of changes in the balance between cell proliferation and apoptosis and we will review targets in both these areas, including reversal of epigenetic silencing of genes such as p15(INK4B).

Amifostine inhibits angiogenesis in vivo

Amifostine (WR-2721) is an inorganic thiophosphate-cytoprotective agent developed to selectively protect normal tissues against the toxicity of chemotherapy and radiation. We have previously shown that amifostine protects both chicken embryo chorioallantoic membrane (CAM) vessels and cells from the effects of X-rays. In the present work, we studied the effect of amifostine on angiogenesis in vivo, using the CAM model. Amifostine decreased the number of CAM vessels in a dose-dependent manner, without being toxic for the tissue. It also decreased the mRNA levels of both vascular endothelial growth factor (VEGF) isoforms VEGF(165) and VEGF(190), 6 and up to 48 h after its application onto the CAM. Similarly, it decreased the mRNA levels of inducible nitric-oxide synthase, 24 and 48 h after drug application. Furthermore, amifostine decreased the deposited amounts of laminin and collagen I 24 h after its application, without affecting the expression of the corresponding genes. The protein amounts and activity of matrix metalloproteinase-2 were not affected, whereas the expression of the corresponding gene was decreased up to 48 h after drug application. Finally, the activity of plasmin was increased 6 h after amifostine application and remained increased at later time points. These findings suggest that amifostine alters the expression of several molecules implicated in the angiogenesis process and affects the composition of the extracellular matrix in a way that leads to inhibition of angiogenesis. Such an antiangiogenic action of amifostine, together with its radioprotective effects, further supports its use in combination with radiotherapy for increased therapeutic efficacy.

Phase I study of fotemustine in pediatric patients with refractory brain tumors

BACKGROUND

Fotemustine is a nitrosourea with theoretic and preclinical advantages over the original analogs, carmustine and lomustine, in the treatment of brain tumors. This is the first pediatric Phase I study of fotemustine.

METHODS

Patients younger than 21 with recurrent/resistant brain tumors were enrolled in a conventional Phase I study. Fotemustine was administered intravenously every 3 weeks at increasing dose levels starting at 100 mg/m(2). Toxicity and response data were monitored closely.

RESULTS

Fifteen evaluable patients entered the study and received a total of 45 courses of fotemustine (dose range, 100-175 mg/m(2)). Myelosuppression was observed, with the dose-limiting toxicity being Grade 4 neutropenia and thrombocytopenia. Toxicity was delayed and cumulative. The maximum tolerated dose was 150 mg/m(2) every 3 weeks. There were three documented radiologic responses (20% of patients) comprising one partial response and two minor responses in patients with a sarcoma, medulloblastoma, and ependymoma, respectively.

CONCLUSIONS

Fotemustine administered at a dose of 150 mg/m(2) every 3 weeks is well tolerated in children and has antitumor activity in several brain tumors. This is the first dedicated Phase I study of a single agent nitrosourea in a pediatric population. More comparative studies should be undertaken to define the optimum nitrosourea analog for use in children with brain tumors.