Role of Plant-Derived Flavonoids in Cancer Treatment.

Flavonoids are polyphenolic phytochemicals, which occur naturally in plants and possess both anti-oxidant and pro-oxidant properties. Flavonoids are gaining increasing popularity in the pharmaceutical industry as healthy and cost-effective compounds. Flavonoids show beneficial pharmacological activities in the treatment and prevention of various types of diseases. They are natural and less toxic agents for cancer chemotherapy and radiotherapy via regulation of multiple cell signaling pathways and pro-oxidant effects. In this review, we have summarized the mechanisms of action of selected flavonoids, and their pharmacological implications and potential therapeutic applications in cancer therapy.

Ellagic Acid Enhances Apoptotic Sensitivity of Breast Cancer Cells to γ-Radiation.

Herbal polyphenols have gained increased significance because of the promises they hold in the prevention and treatment of cancer. There exists an enormous opportunity for the screening and valuation of natural dietary compounds in the development of an effective chemopreventive drug and radiosensitizer that may be of practical use for patients undergoing cancer therapy. This study describes the effect of the flavonoid ellagic acid (EA) on gamma-irradiated human breast cancer MCF-7 cells in vitro when administered alone or in combination with radiation. It was interesting to find the radioprotective effect of EA on NIH3T3, which is a normal cell line. Irradiation of breast tumor cells in the presence of EA (10 µM) to doses of 2 and 4-Gy gamma radiation produced a marked synergistic tumor cytotoxicity while it was found to aid recovery from the radiation damage to NIH3T3 cells. When cells were given a combined treatment of EA and radiation, the cell death increased to 21.7% and 20.7% in the 2 and 4-Gy-treated cells respectively, significantly (P < 0.05) reducing the capacity of MCF-7 cells to form colonies. Even at 24 h, 38 foci/cell were observed in samples that were given the combined treatment, suggesting the cells' inability in repairing the damage. Also, increased apoptosis in EA+ 2Gy (50%) and EA+ 4 Gy (62%)-treated cells was observed in the the sub-G1 phase of the cell cycle. A 6.2-fold decrease in the mitochondrial membrane potential was observed in the combined treatment of EA and IR that facilitated the upregulation of pro-apopttotic Bax and downregulation of Bcl-2, pushing the MCF-7 cells to undergo an apoptotic cell death. It is suggested that EA may be a potential drug adjuvant for improving cancer radiotherapy by increasing tumor toxicity and reducing the normal cell damage caused by irradiation.

Augmentation of radiation-induced apoptosis by ellagic acid.

This study evaluates the potential of ellagic acid (EA) as an enhancer of radiation-induced apoptosis in cancer cells. HeLa cells treated with EA and gamma radiation showed increased superoxide generation, upregulated p53 protein expression, and decreased antioxidant enzymes. We also found that EA and radiation enhance capase-3 activity via oxidative stress, increased intracellular calcium levels, and phospholipase C and cause a drop in mitochondrial potential. These results might provide a basis for prominent reduction of cancer cell using EA as an adjunct to radiotherapy and an opportunity to lower the toxic radiation doses to improve the quality of life.

Flavonoids sensitize tumor cells to radiation: molecular mechanisms and relevance to cancer radiotherapy.

Purpose: Radiobiological research continues to focus on finding newer strategies for enhanced killing of tumor cells by ionizing radiation. In recent years, chemotherapeutic drugs have been found to possess the capabilities to sensitize tumor cells without affecting the normal cells. There have been increasing research efforts to identify novel and nontoxic compounds which cause minimal or no harm to normal cells but maximize tumor toxicity response to radiation exposure. Extensive researches on flavonoids that are compounds derived from plants have shown that these have promising abilities as radioprotectors and radiosensitizers.Conclusions: In this review, we examine the role of flavonoids as potential radiosensitizers, review the underlying molecular mechanisms and discuss their potential usefulness in improving cancer radiotherapy. It is emphasized that obtaining a deeper insight into the molecular mechanisms underlying the combined action of flavonoids and ionizing radiation may provide new directions for radiobiological research applicable to the much needed enhanced selective tumor cytotoxicity to treatment agents.

Thorium-induced neurobehavioural and neurochemical alterations in Swiss mice.

PURPOSE: Thorium ((232)Th), a heavy metal radionuclide that targets the liver and skeleton, has been shown to accumulate in the central nervous system at low levels. The present study was aimed to investigate neurobehavioural and neurochemical changes in mice treated with (232)Th at sub-lethal doses. MATERIALS AND METHODS: Swiss albino mice were administered intraperitoneally with thorium nitrate. The chelation-based therapeutic effect of calcium diethylenetriamine pentaacetate (Ca-DTPA) was tested on the (232)Th-treated mice. (232)Th localisation was determined in brain regions by the Inductively Coupled Plasma-Atomic Emission Spectroscopy (ICP-AES) method. Achetylcholine esterase (AChE) activity in different brain regions was evaluated to assess the cholinergic function of mice CNS. Oxidative damage was evaluated by assessing the activities of antioxidant enzymes (i.e., superoxide dismutase and catalase) and the level of lipid peroxidation. The neurobehavioural alteration in the treated mice was studied by the shuttle box method. RESULTS: (232)Th accumulation found in different brain regions followed the order: Cerebellum (Cbl) > cortex (Ctx) > hippocampus (Hp) > striatum (Str). However, removal of (232)Th by Ca-DTPA was significant from brain regions like Cbl, Ctx and Str but not from Hp. A significant increase in lipid peroxidation and acetylcholine esterase (AChE) activity was observed in the treated mice but activities of superoxide dismutase and catalase was found substantially decreased. (232)Th treatment impaired the learning and memory-based neurobehaviour of the mice. Furthermore, our data suggest that Ca-DTPA injection in (232)Th-treated animals failed to improve the neurobehaviour of the treated mice, perhaps because Ca-DTPA could not decorporate (232)Th or mitigate (232)Th-mediated neurochemical changes effectively from/in hippocampus, a brain region implicated in learning and memory response. CONCLUSION: Administration of (232)Th in mice caused neurobehavioural alteration and impairment of cholinergic function, which might be the consequence(s) of oxidative stress induction in different brain regions.

Correlation of FBX dosimeter and micronucleus assay in radiation dosimetry of gamma chambers.

The aim of the present study is to determine the dose distribution in gamma irradiation chambers by chemical dosimetry and to establish its correlation with biological dosimetry. The dose-distribution studies of these two gamma chambers show that compared to the center point of the chambers, the dose rate was 17%-22% higher at the circumference. Moreover, the dose rate was 12%-18% lower at the bottom and top positions compared to the center point. It was interesting to observe that the dose rate determined by chemical dosimetry was well correlated with the number of micro-nucleus (MN) formations at different positions of the chamber. Our results suggest that the formation of the single MN/cell was better correlated with the dose rate than the double MN/cell, suggesting that the number of single MN/cells could be better biomarkers for determining the dose rate. These results provide a correlation between chemical and biological dosimetry, which may have relevance in the development of better bioassay techniques for radiation exposure.

Thorium-induced oxidative stress mediated toxicity in mice and its abrogation by diethylenetriamine pentaacetate.

PURPOSE: Thorium ((232)Th, IV) preferentially accumulates in the liver, femur and spleen, which necessitates evaluation of its toxic effect in these organs. The present study was aimed at evaluation of liver function, oxidative stress and histological alterations in these organs. MATERIALS AND METHODS: Swiss albino mice were administered either with Thorium nitrate (10 mg/kg body weight/day equivalent to 1,090 pCi/kg body weight/day) for 30 days (1/40th dose of LD(50/30); the dose of thorium required to kill 50% of the test cohort within 30 days) intraperitoneally or with calcium salt of diethylenetriamine pentaacetate (Ca-DTPA, 100 micromole/kg body/weight) intravenously or both. Liver function tests and oxidative damage was assessed. The concentration of Th in the tissues was determined by Inductively Coupled Plasma-Atomic Emission Spectroscopy (ICP-AES) method. RESULTS: Administration of Th prevented the increase in the body and liver weight and altered liver functions. Th treatment to mice showed a decrease in the activities and gene expression of antioxidant enzymes, and increased lipid peroxidation and protein carbonylation. The extent of observed oxidative damage was correlated with accumulation of Th in examined organs and further associated with histological alterations. Furthermore it was found that these effects were significantly lower when the chelating agent, Ca-DTPA, was given 1 h after Th injection. CONCLUSION: Administration of subtoxic concentration of Th to mice markedly altered the liver functions and induced oxidative stress in the liver, femur and spleen of mice. The results further demonstrated that Ca-DTPA significantly protected mice against the toxic effects of Th.

A simple one-step protocol for preparing small-sized doxorubicin-loaded liposomes.

A simple, single-step, extrusion-free protocol for preparing doxorubicin-loaded liposomes (100150 nm), based on the ethanol injection method (EIM), is described. Efficient encapsulation of doxorubicin (up to 98%) was obtained concomitantly with liposome preparation avoiding the need for an additional loading step. Parameters such as stock concentration of phospholipid, injection ratio, lipid composition, and drug-to-phospholipid ratio affected the resultant liposome size and magnitude of doxorubicin encapsulation. A lipid stock concentration (50 mM) and injection ratio (1:10) resulted in 96.0 +/- 2.92% encapsulation efficiency of doxorubicin (drug-to-lipid mole ratio: 0.192) and mean diameter of 135 +/- 2.32 nm for SCOL-2 formulation (DSPC/ cholesterol /oleic acid: 2/2/1; molar ratios). Replacement of phospholipid DSPC with DMPC or DPPC did not affect the mean liposome size and doxorubicin-encapsulation efficiency. These findings offer promise for scale-up and development on a large-scale production of doxorubicin-loaded liposomes for effective cancer therapy.

Studying the in Silico Effect of Ellagic Acid on HIF-2α to Improve Efficacy of Anticancer Therapy.

The hypoxic tumor microenvironment is one of the major causes of the enhanced chemoresistant and radioresistant behavior of cancer cells. Therefore, the hypoxia-induced factor (HIF) pathway can be endorsed, for not only the malignant phenotype of the cells, but also its metastatic potential. Many drugs targeting the HIF pathways have failed in the clinical setting to demonstrate therapeutic efficacy. Such failures occur due to lack of specificity or redundancy in the complexity of tumor signaling/metabolism that can overcome the inhibitory effects. Another important factor is the letdown of the compound that can be accredited to lack of patient selection in the trials. Although many clinical trials have evaluated the efficacy of anticancer therapeutics and examined their effects on HIF levels, patients were not selected based on their HIF expression levels. If patients do not have elevated levels of HIF, then the therapeutics that target the HIF pathway may be less effective. In the present work, we have targeted HIF-2α of the HIF pathway. Ellagic acid (EA), a well-known anticancer compound and radiosensitizer, is used to inhibit the activity of HIF-2α. Our results show a very unique binding of EA with HIF-2α. Such new agents should be used in combination therapy and will hopefully overcome the resistance that may develop during initial treatment if the patient is identified to have enhanced expression of HIF-2α. Molecular dynamics studies followed solvation free energy calculations (molecular mechanics Poisson-Boltzmann surface area) for understanding the binding stability and per residue contribution. Our in silico data look promising and EA should be studied more in in vitro and in vivo for further analysis of its efficacy.

Acute exposure of uranyl nitrate causes lipid peroxidation and histopathological damage in brain and bone of Wistar rat.

Although the kidneys are the main target organs for uranium (U) toxicity, recent studies have shown that U can cross the blood-brain barrier to accumulate in the brain. Uranyl nitrate (U-238)induced oxidative damage was investigated in brain and bone of Wistar rats after intraperitoneal injection of uranyl nitrate at acute doses either nephrotoxic (576 microg of U/kg body weight) or subnephrotoxic (144 microg U/kg body weight). The health effects of U administration at 576 microg of U/kg body weight were seen in terms of decrease in food intake and no gain in body weight compared to respective controls. These alterations were correlated with increased lipid peroxidation as measured by thiobarbituric acid reactive substances in rat brain and bone. However, at lower dosage of U (144 microg U/kg body weight), no significant lipid peroxidation was observed in brain and bone. Histological examination of U-treated (576 microg of U/kg body weight) rat brain tissues showed marked and diffuse cystic degeneration and a similar pattern in histological alterations was observed in kidneys in treated animals; whereas no significant histological change was observed in rat brains and kidney treated with a lower dose of U (144 microg U/kg body weight). It is concluded that administration of U at an acute nephrotoxic dose caused oxidative stress in brain and bone manifested as lipid peroxidation and histopathological damage.

Radiation-induced incidence of thymic lymphoma in mice and its prevention by antioxidants.

Previous reports from our laboratory have shown that in Swiss female mice exposed to an acute dose (3 Gy) of whole body irradiation (WBI), induced thymic lymphoma (TL) resulted after three to four weeks of exposure. The present study was aimed to further evaluate dependency on gender and effect of age of mice at the time of irradiation on TL incidence. A significant decrease in body weight gain was observed in female mice exposed to WBI, which was found to be correlated with the increase in weight and size of thymus, compared to their respective controls. An increase in TL incidence was observed with the increased postirradiation time, which was 47, 80, and 93% after 90, 120, and 150 days of WBI, respectively, in female mice. In irradiated female mice, the TL incidence was significantly higher and the growth of tumor in terms of weight and size was more aggressive than in males of the same age. Moreover, mice with higher age groups at the time of irradiation showed substantial decrease in TL incidence and its aggressiveness; and these effects were more conspicuous in males than in females. In mice irradiated at the age group of three to four weeks, the TL incidence was 83 and 72% in female and male, respectively, which was decreased to 74% in female and 14% in male in the age group of 12-13 weeks. It was further observed that the postirradiation feeding of animals with antioxidants resulted in a significant decrease in TL incidence, and the prevention in TL incidence was more in animals fed with curcumin (55%) than with ascorbic acid and eugenol (20%). These results have provided significant new findings on the phenomenon of radiation-induced TL incidence related to gender and age at the time of irradiation and its prevention by postirradiation antioxidant feeding to mice.

Radioprotection against DNA damage by an extract of Indian green mussel, Perna viridis (L).

This study describes the radioprotective ability of a hydrolysate prepared using an enzyme-acid hydrolysis method from the green mussel Perna viridis in terms of its ability to prevent radiation-induced damage in plasmid DNA, cell death, reactive oxygen species (ROS) formation, and DNA damage in mice lymphocytes. The mussel hydrolysate (MH) present during irradiation showed significant protection from gamma-radiation-induced strand breaks in plasmid DNA as evaluated by gel electrophoresis. Viability studies by trypan blue dye exclusion and MTT assay showed that preincubation of mice splenic lymphocytes with MH protected them from gamma-radiation-mediated killing. Moreover, the presence of MH during irradiation of isolated mice lymphocytes significantly decreased the DNA damage, as measured by comet assay. Measurement of intracellular ROS by dichlorofluorescein fluorescence revealed that the presence of MH effectively reduced the ROS generated in lymphocytes by both chemical method and gamma-irradiation. Prevention of DNA damage both in plasmid and lymphocytes and cell death in lymphocytes appears correlated with reduction of oxidatively generated free radicals. It is concluded that protection against radiation-induced cell death and DNA damage by MH was attributable to reduction of reactive free radical species generated by gamma-radiation.

Comparative evaluation of heating ability and biocompatibility of different ferrite-based magnetic fluids for hyperthermia application.

In this study, lauric acid-coated, superparamagnetic, nanoparticle-based magnetic fluids of different ferrites (Fe(3)O(4), MnFe(2)O(4), and CoFe(2)O(4)) were prepared and compared in terms of heating ability and biocompatibility to evaluate the feasibility of use in hyperthermia treatment of cancer. All the magnetic fluids prepared had particles of average sizes 9-11 nm. Heating ability of these magnetic fluids was evaluated by calorimetric measurement of specific absorption rate (SAR) at 300 kHz frequency and 15 kA/m field. Fe(3)O(4) and MnFe(2)O(4) showed higher SAR (120 and 97 W/g of ferrite, respectively) than CoFe(2)O(4) (37 W/g of ferrite). In vitro study on BHK 21 cell lines showed dose-dependent cell viability for all the magnetic fluids. Threshold-biocompatible ferrite concentration for all the magnetic fluids was 0.1 mg/mL. Above 0.2 mg/mL, CoFe(2)O(4) was more toxic than the other magnetic fluids. On intravenous injection of different doses (50, 200, and 400 mg/kg body weight) of magnetic fluids in mice, no significant changes in hematological and biochemical parameters were observed for Fe(3)O(4) and MnFe(2)O(4). With CoFe(2)O(4), an increase in SGPT levels at a dose rate of 400 mg/kg body weight was observed, indicating its mild hepatotoxic effect. However, histology of different vital organs showed no pathological changes for all the three magnetic fluids. Further, long term in vivo evaluation of biocompatibility of the lauric acid-coated ferrites is warranted. This study shows that lauric acid-coated, superparamagnetic Fe(3)O(4) and MnFe(2)O(4) may be used for hyperthermia treatment and are to be preferred over CoFe(2)O(4).

Aluminum-induced maternal and developmental toxicity and oxidative stress in rat brain: response to combined administration of Tiron and glutathione.

The current study was performed to assess the potential of 4,5-dihydroxy 1,3-benzene disulfonic acid di sodium salt (Tiron) and glutathione (GSH) either individually or in combination against aluminum (Al)-induced developmental toxicity in fetuses and sucklings of Wistar rats. Female rats were exposed to aluminum chloride at a dose of 345 mg/(kg day) oral from days 0 to 16 of gestation and 0 to 16 of post-partum (P.P.). Tiron and GSH were administered at a dose of 471 mg/(kg day) i.p. and 100 mg/(kg day) oral, respectively, on days 5, 7, 9, 11, 13, 15 and 17 of gestation and post-partum. Al caused reduction in number of corpora lutea, number of implantation sites, placental and fetal weight and stunted growth. Skeletal malformations were also observed in fetuses. Maternal toxicity was demonstrated by reduction in body weight gain. Induction of oxidative stress was also recorded in the brain of mother as well as in fetuses and sucklings after Al exposure. Significant decrease was recorded in reduced glutathione, glutathione reductase (GR), glutathione peroxidase (GPx), catalase (CAT), superoxide dismutase (SOD), acetyl cholinesterase (AChE) and increase was observed in TBARS and glutathione-S-transferase (GST) in brain of pregnant mothers, fetuses and sucklings. Most of the above parameters responded positively with individual therapy with Tiron, but more pronounced beneficial effects on the above-described parameters were observed when Tiron was administered in combination with GSH. Inductively coupled plasma-atomic emission spectroscopy (ICP-AES) studies also showed significantly high concentration of Al in suckling's brain and maternal blood, brain, placenta and fetal brain. Treatment with Tiron individually or in combination with glutathione, reduced the accumulation of the Al in almost all the organs studied. It is concluded that chelating agents reduced the Al-induced toxicity and Tiron was more effective in reducing blood Al concentration than glutathione when given individually.

Inhibition of the p53 Y220C Mutant by 1-Hydroxy-2- Methylanthraquinone Derivatives: A Novel Strategy for Cancer Therapy.

Y220C, a substitution mutation in p53, causes major structural changes in the protein and is known to form a new protein cavity. This cavity is reckoned to accommodate small drug candidates that may play a key role in cancer treatment. Present study was aimed at determining a drug candidate that could inhibit the mutant p53 based on structural drug rationale. Docking of mutated p53 was performed to determine the drug of choice from the derivatives of 1-hydroxy-2- methylanthraquinone exhibiting anti-cancer properties. The cavity had been tested for identification of an accurate position vector for molecular docking studies using structure based drug design. The docked structure was validated using discovery studio 3.5. The best choice of two molecules were obtained by docking in specific solvent for 6 nanoseconds at a temperature of 310 K. Out of a library of compounds, acetamido-2-carboxy-4-dimethylamino-2- hydroxybenzophenone satisfied the ADMET and was found to be a potential target for mutant p53. This ligand binds at the active site of the protein. Results of present study offer a rationale of the lead ligands that can rescue oncogenic p53 by targeting the mutation site. Therefore, it is suggestive that small molecules may serve as an effective and novel anti-cancer drug.

Enhancement of radiation-induced oxidative stress and cytotoxicity in tumor cells by ellagic acid.

BACKGROUND: Failure of treatment of cancer in clinic by radio/chemotherapy is generally attributed to tumor resistance. It is, therefore, important to develop strategies to increase the cytotoxicity of tumor cells by radiation in combination with new tumor selective cytotoxic agents. We describe the role of ellagic acid (EA) and gamma radiation on the oxidative stress and subsequent cytotoxicity of tumor cells in vitro as well as in vivo and their sparing effects on normal cells. METHODS: Ehrlich ascites carcinoma (EAC)-transplanted Swiss mice were intraperitoneally injected with EA followed by radiation treatment of 2 Gy for 4 alternate days. Hela cells were used for in vitro studies. Reactive oxygen species (ROS) level was measured by spectrofluorimetric method by using 2, 7-dichlorodihydrofluoresceindiacetate (DCHFDA) fluorescent probe. Cytotoxicity was measured by Trypan blue dye exclusion test and mitochondrial potential was measured using Rhodamine 123 as a probe. Antioxidant enzymes were measured by spectrophotometric methods. RESULTS: EA was found to generate ROS in tumor cells, which increased, by an order of magnitude when cells were treated with EA in combination with gamma radiation. The decrease in mitochondrial potential and the loss of cell viability were remarkably greater in tumor cells from mice treated with EA and radiation than alone treatment with either of them. Moreover, EA was found to protect against radiation-induced oxidative stress in splenic lymphocytes of tumor-transplanted mice. Measurement of antioxidant enzymes such as superoxide dismutase (SOD), catalase, glutathione peroxidase (GSH-Px) and glutathione reductase (GR) in tumor cells showed decrease after treatment with EA and radiation in vivo. Treatment of tumor bearing mice with EA and radiation showed significant decrease in animal's body weight suggesting reduced tumor burden. CONCLUSION: Combined treatment of tumor with EA and radiation enhances oxidative stress and cytotoxicity in tumor cells. EA protects normal cells against radiation damage. This may offer potential therapeutic benefit, which warrants clinical study for application in cancer radiotherapy.

On the mechanism of cellular toxicity in breast cancer by ionizing radiation and chemotherapeutic drugs.

Breast cancer is the second leading cause of cancer mortality and the most frequent cancer found in women around the globe. The development of breast cancer is a multistep and complicated process that includes the development of ductal and lobular cells into atypical hyperplasia, carcinoma in situ, and invasive carcinoma, with an ability to metastasize. The efficacy of radiotherapy in breast cancer seems to be reduced because of a frequently observed lack of cellular sensitivity to apoptosis. Both Bcl-2 and p53 are linked to apoptosis pathways and are known to play a role in the outcome of radiotherapy. Resistance of tumor cells to therapeutic drugs and the undesirable cytotoxicity of normal cells are frequently observed in treatment outcomes in clinics. Research is, therefore, needed to develop strategies for improving the protocols of chemotherapy and radiotherapy in patients with breast cancer. This review focuses on understanding the molecular mechanisms of enhanced tumor cell killing by the combined action of certain anticancer drugs together with gamma radiation in vitro, with possible implications for practical applications in clinics.

Reactive oxygen species as mediator of tumor radiosensitivity.

In normal functioning of the cell, there is a balance between generation and neutralization of reactive oxygen species (ROS) by endogenous cellular defense machinery. Low levels of ROS inside the cells are required for normal functioning of the cell, which regulate signaling mechanisms involved in mitosis and apoptosis; excess of ROS production may cause oxidative stress leading to damage in vital cellular molecules, namely cytosolic lipids, proteins, and DNA. In the situation of intracellular redox imbalance, molecules of cells are altered by ROS leading to pathogenic state. It is to be noted that ROS is not only known to be involved in tumor induction and progression processes but also enhances tumor cell radiosensitivity. The level of ROS-mediated oxidative stress is linked to cellular radiosensitivity. In general, cancer cells exhibit high levels of ROS, which forms a target for selectively killing them by radiation. In this paper, we have reviewed how oxidative stress determines the radiosensitivity of tumor cells involving ROS in the mechanism of radiation induced tumor cell killing. It is suggested that radiation-induced ROS play a key role in the mechanism of tumor cell killing by altering the signaling network and triggering of apoptosis. Furthermore, it is pointed out that combined use of plant-derived antioxidants and radiation enhance overproduction of ROS in tumor cells leading to enhanced radiosensitivity, which may find practical applications in clinic.

Biochanin A enhances the radiotoxicity in colon tumor cells in vitro.

Herbs and other plant-based compounds have increasingly been recognized as useful for the prevention and treatment of cancer. There exists enormous scope for screening and evaluation of herbal/plant products to develop an effective radiosensitizer and radioprotector that is relevant for cancer therapy. Anticancer agents that can effectively trigger the process of cell death in tumor cells need to be developed. This study describes the effect of the flavonoid biochanin A (BCA), administered alone or in combination with gamma radiation, on the growth of radioresistant human colon cancer HT29 cells in vitro. Proliferation studies were carried out using MTT assay with increasing concentration of BCA (1-100 µM) followed by gamma irradiation at a dose of 2 Gy. Induced reactive oxygen species, mitochondrial membrane potential, lipid peroxidation, and caspase-3 activation were measured by fluorescence assays and the magnitude of induced apoptosis in cells was evaluated by flow cytometry. Cellular DNA damage was determined by comet assay. Combined treatment caused a significant decrease in cell proliferation, a substantial increase in the generation of reactive oxygen species, enhanced lipid peroxidation, and increased mitochondrial membrane potential in treated HT29 cells compared with controls. Significantly enhanced apoptosis and DNA damage were found with a combination of drug and radiation treatments. Furthermore, it was found that combined treatment yielded an additive increase of caspase-3 in these cells. Our findings indicate that BCA acts as a remarkable pro-oxidant, significantly enhancing the radiotoxicity of colon cancer cells in vitro.

Decorporation and therapeutic efficacy of liposomal-DTPA against thorium-induced toxicity in the Wistar rat.

PURPOSE: This study examined the effect of liposomal encapsulation of (99m)Tc-labeled diethylenetriaminepentaacetic acid (metastable technetium labeled DTPA) on its organ distribution and therapeutic effect of optimized neutral liposomal-DTPA against thorium ((232)Th)-induced liver toxicity and its accumulation in rat animal model. MATERIALS AND METHODS: (99m)Tc-DTPA was encapsulated in neutral (dipalmitoylphosphatidylcholine:cholesterol) and positively (dipalmitoylphosphatidylcholine:cholesterol:stearylamine) charged liposomes using thin film hydration method. Comparative efficacy of liposomal and free DTPA (11.2 mg/kg) was examined in terms of its effect on (232)Th accumulation and subsequent toxicity in the liver and blood of rat administered with (232)Th-nitrate (600 µg/kg). Organ distribution of free or liposomal (99m)Tc-DTPA was determined by solid scintillation counting and (232)Th accumulation by Inductively Coupled Plasma-Atomic Emission Spectroscopy. RESULTS: Neutral liposomes encapsulated with (99m)Tc-DTPA showed more uptake in liver, spleen and blood than with positively charged liposomal- and free- (99m)Tc-DTPA. Administration of (232)Th-nitrate to rat significantly increased the levels of liver toxicity markers and of oxidative injury, which were found to be restored more significantly by neutral liposomal-DTPA than free-DTPA. The accumulation of (232)Th in liver and blood of contaminated mice was found to be decreased more significantly by neutral liposomal-DTPA than by free-DTPA. CONCLUSIONS: Decorporation and consequent mitigation of (232)Th induced toxicity may be significantly improved by liposomal encapsulation of DTPA, a chelating agent.