Difference in carcinogenicities of two different vapor grown carbon fibers with different physicochemical characteristics induced by intratracheal instillation in rats.

BACKGROUND: Carbon fibers are high aspect ratio structures with diameters on the submicron scale. Vapor grown carbon fibers are contained within multi-walled carbon tubes, with VGCF™-H commonly applied as a conductive additive in lithium-ion batteries. However, several multi-walled carbon fibers, including MWNT-7, have been reported to induce lung carcinogenicity in rats. This study investigated the carcinogenic potential of VGCF™-H fibers in F344 rats of both sexes with the vapor grown carbon fibers VGCF™-H and MWNT-7 over 2 years. The carbon fibers were administered to rats by intratracheal instillation at doses of 0, 0.016, 0.08, and 0.4 mg/kg (total doses of 0, 0.128, 0.64, and 3.2 mg/kg) once per week for eight weeks and the rats were observed for up to 2 years after the first instillation. RESULTS: Histopathological examination showed the induction of malignant mesothelioma on the pleural cavity with dose-dependent increases observed at 0, 0.128, 0.64, and 3.2 mg/kg in rats of both sexes that were exposed to MWNT-7. On the other hand, only two cases of pleural malignant mesothelioma were observed in the VGCF™-H groups; both rats that received 3.2 mg/kg in male. The animals in the MWNT-7 groups either died or became moribund earlier than those in the VGCF™-H groups, which is thought related to the development of malignant mesothelioma. The survival rates were higher in the VGCF™-H group, and more carbon fibers were observed in the pleural lavage fluid (PLF) of the MWNT-7 groups. These results suggest that malignant mesothelioma is related to the transfer of carbon fibers into the pleural cavity. CONCLUSIONS: The intratracheal instillation of MWNT-7 clearly led to carcinogenicity in both male and female rats at all doses. The equivocal evidence for carcinogenic potential that was observed in male rats exposed to VGCF™-H was not seen in the females. The differences in the carcinogenicities of the two types of carbon fibers are thought due to differences in the number of carbon fibers reaching the pleural cavity. The results indicate that the carcinogenic activity of VGCF™-H is lower than that of MWNT-7.

An International Collaborative Animal Study of the Carcinogenicity of Mobile Phone Radiofrequency Radiation: Considerations for Preparation of a Global Project.

Radiofrequency radiation (RFR) was classified as a "possible" human carcinogen in 2011, which caused great public concern. A carcinogenicity study by the National Toxicology Program (NTP) found Code Division Multiple Access-and Global System for Mobile Communications-modulated mobile phone RFR to be carcinogenic to the brain and heart of male rats. As part of an investigation of mobile phone carcinogenesis, and to verify the NTP study results, a 5-year collaborative animal project was started in Korea and Japan in 2019. An international animal study of this type has two prerequisites: use of the same study protocol and the same RF-exposure system. This article discusses our experience in the design of this global study on radiofrequency electromagnetic fields (RF-EMFs).© 2022 The Authors. Bioelectromagnetics published by Wiley Periodicals LLC on behalf of Bioelectromagnetics Society.

Lung toxicity of a vapor-grown carbon fiber in comparison with a multi-walled carbon nanotube in F344 rats.

Carbon fibers have excellent physicochemical and electrical properties. Vapor-grown carbon fibers are a type of carbon fibers that have a multi-walled carbon tube structure with a high aspect ratio. The representative vapor-grown carbon fiber, VGCFTM-H, is extremely strong and stable and has superior thermal and electrical conductivity. Because some high-aspect-ratio multi-walled carbon nanotubes (MWCNTs) have been reported to have toxic and carcinogenic effects in the lungs of rodents, we performed a 13-week lung toxicity study using VGCFTM-H in comparison with one of MWCNTs, MWNT-7, in rats. Male and female F344 rats were intratracheally administered VGCFTM-H at doses of 0.2, 0.4, and 0.8 mg/kg bw or MWNT-7 at doses of 0.4 and 0.8 mg/kg bw once a week for 8 weeks and then up to week 13 without treatment. The lung burden was equivalent in the VGCFTM-H and MWNT-7 groups; however, the lung weight had increased and the inflammatory and biochemical parameters in the broncho-alveolar lavage fluid and histopathological parameters, including inflammatory cell infiltration, alveolar type II cells proliferation, alveolar fibrosis, pleural fibrosis, lung mesothelium proliferation, and diaphragm fibrosis, were milder in the VGCFTM-H group than in the MWNT-7 group. In addition, the proliferating cell nuclear antigen (PCNA)-positive index in the visceral and pleural mesothelium was significantly higher in the MWNT-7 group than in the controls, but not in the VGCFTM-H group. Thus, the results of this study indicate that the lung and pleural toxicities of VGCFTM-H were less than those of MWNT-7.

Establishment and Validation of an Ultra-Short-Term Skin Carcinogenicity Bioassay Using Tg-rasH2 Mice.

After initiation with 7,12-dimethylbenz[a]anthracene (DMBA), the promoting potential of 12-O-tetradecanoylphorbol-13-acetate (TPA) on skin tumor development can be detected by an ultra-short-term skin carcinogenicity bioassay using Tg-rasH2 mice. In the present study, 10 chemicals were assessed using this ultra-short-term bioassay as a first step to validate this practical and easy-to-use skin carcinogenicity bioassay. These chemicals belonged to 4 categories: dermal vehicles (acetone, 99.5% ethanol, anhydrous ethanol, and Vaseline), skin noncarcinogens (oleic acid diethanolamine condensate, benzethonium chloride, and diisopropylcarbodiimide), skin tumor promoters (TPA and benzoyl peroxide), and a skin carcinogen (4-vinyl-1-cyclohexene diepoxide). In a first study, DMBA was used as the initiator at a dose of 50 µg according to previous data, but skin tumors were observed in the no-treatment and vehicle groups. Therefore, the dose of DMBA for skin tumor initiation was reevaluated using 12.5 or 25 µg, with 12.5 µg found to be sufficient for initiation activity. In the ultra-short-term assay, the vehicles and skin noncarcinogens were negative while the skin tumor promoters and the skin carcinogen were positive. The detection of skin tumor promotion and carcinogenicity was feasible in only 8 weeks. In conclusion, this carcinogenicity bioassay may represent a useful tool for the assessment of the carcinogenicity potential of topically applied chemicals.

Effects of administering different vehicles via single intratracheal instillation on responses in the lung and pleural cavity of Crl:CD(SD) rats.

Intratracheal instillation is the introduction of a substance directly into the trachea. Intratracheal instillation has been used to investigate the lung toxicity of several chemicals and requires the suspension or dissolution of test material in a vehicle for even dispersal throughout the lung. Importantly, the toxicities of vehicles used in intratracheal instillation studies are generally considered to be insignificant. Hence, evaluating the influence of different vehicles on the lung due to intratracheal instillation is crucial. We examined the toxic effects of pure water, saline, phosphate buffered saline (PBS), 0.5% Kolliphor® P188 (KP188), 0.1% Tween 20 in saline, and 1.0% BSA in PBS. These vehicles were administered to male Crl:CD(SD) rats by a single intratracheal instillation. On day 3, broncho-alveolar lavage fluid (BALF) from the right lung was collected and processed for cell counting and biochemical analysis, while the left lung was used for histopathological examination. Accumulation of alveolar macrophages was observed in all vehicle-treated groups but was minimal in the group administered saline, somewhat higher in the groups administered pure water, PBS, 0.1% Tween 20, and 1% BSA, and notably higher in the group administered 0.5% KP188. The results from BALF analysis indicated that intratracheal instillation of 0.5% KP188 also induced alveolar damage. Additionally, administering pure water did not appear to cause tissue damage. Eosinophil infiltration in the interstitial regions was histopathologically observed. Altogether, the results of this study are helpful for the selection of appropriate vehicles for use in intratracheal instillation studies.

Central Transient Receptor Potential Vanilloid 4 Contributes to Systemic Water Homeostasis through Urinary Excretion.

Intracerebroventricular (icv) injection of transient receptor potential vanilloid 4 (TRPV4) agonists 4α-phorbol-12, 13-didecanoate (4α-PDD) and GSK101690A increased urinary excretion under the physiological condition. TRPV4 antagonists ruthenium red and HC-067047 significantly blocked increased urinary volume after intragastric administration of water and 4α-PDD-induced diuresis. Administration of the TRPV4 agonists did not significantly change the plasma concentration of vasopressin or atrial natriuretic factor. Pretreatment with indomethacin inhibited the diuresis induced by 4α-PDD. Moreover, icv injection of prostaglandin (PG) F2α produced diuretic effects. These findings indicate that central TRPV4 regulates urine excretion, which contributes to systemic water homeostasis in vivo. The underlying mechanisms are suggested to involve PG synthesis, but not release of vasopressin or atrial natriuretic factor.

Carcinogenicity of intermediate frequency magnetic field in Tg.rasH2 mice.

Although the likelihood of exposure to leaking intermediate frequency magnetic fields (MFs) from electronic devices, such as induction-heating and wireless power transfer systems, has increased, biological data assessing the health risks associated with human exposure remain insufficient. We examined the carcinogenicity of a 20 kHz MF, a typical frequency produced by induction-heating cookers, using a transgenic rasH2 mouse model. Twenty-five male and female CByB6F1-Tg(HRAS)2Jic mice were exposed to a 0.20 mT, 20 kHz MF (22 h/day) or sham-exposed for 26 weeks. As a positive control, 10 male and female rasH2 mice from the same batch were administered a single intraperitoneal injection of 75 mg/kg N-methyl-N-nitrosourea. A blinded histopathological evaluation was performed, and the same experiments were conducted twice, independently, to confirm the reproducibility of the results. Histopathological examination revealed that spontaneous neoplastic lesions, such as splenic hemangiosarcomas and gastric squamous cell papillomas, were less (1-3 per group) in the MF- and sham-exposed groups. The frequency of the neoplastic lesions was not significantly different between the groups. Eight to ten mice in each positive-control group exhibited malignant lymphoma. The outcomes were consistent between duplicated experiments, which indicates lack of carcinogenicity of 20 kHz MF in the rasH2 mouse model. Bioelectromagnetics. © 2019 The Authors. Bioelectromagnetics Published by Wiley Periodicals, Inc.

Progression process and safety assessment adaptation of endometrial lesions in ENU-induced 2-stage uterine carcinogenicity in a Tg-rasH2 mouse model.

Although acotiamide hydrochloride hydrate (acotiamide-HH) has not been reported to have genotoxic findings in any of the genotoxicity studies or treatment-related toxicological findings in reproductive and developmental studies, suspicious uterine tumorigenesis was observed in the results of a long-term rat carcinogenicity study. To clarify the uterine tumorigenesis of acotiamide-HH, we performed a 2-stage uterine carcinogenicity model in the transgenic rasH2 mouse initiated by N-Ethyl-N-nitrosourea (ENU). This model facilitated the short-term detection of uterine carcinogenic potential, and it appears to be a very useful testing method for assessing the safety of chemicals that may affect uterine tumorigenesis. However, there have not been many reports on this model, and accumulation of case studies using this model is recommended to support its usability. In this study, we performed this carcinogenesis model to not only confirm uterine tumorigenesis of acotiamide-HH but also to confirm the reliability of the model. The results of this study revealed that the endometrial adenocarcinoma found in the long-term rat carcinogenicity study possibly arose spontaneously. Also, we confirmed early induction of a uterine tumor as in previous reports and confirmed that 26 weeks is the appropriate treatment period for this rasH2 mouse model according to time-course observations of uterine tumor development.

Lung Tumor Induction by 26-week Dermal Application of 1,2-Dichloroethane in CB6F1-Tg rasH2 Mice.

Short-term alternatives to traditional 2-year carcinogenic studies in rodents are being actively pursued. Recently, a 26-week short-term carcinogenicity study using CB6F1-Tg rasH2@Jcl (rasH2) mice has become a worldwide standard for the evaluation of chemical carcinogenesis. However, an acceptable short-term carcinogenic study model for dermally applied products is still lacking. To investigate the suitability of using the rasH2 mouse to test carcinogenic potential, 1,2-dichloroethane (1,2-DCE) was dermally applied to rasH2 mice: 1,2-DCE is a known carcinogen that causes lung bronchiolo-alveolar adenomas and adenocarcinomas when administered topically, orally, or by inhalation exposure; 1,2-DCE at a dose level of 126 mg/mouse in 200 µl acetone or acetone alone (vehicle control) was applied to the dorsal skin of 10 mice of each sex 3 times a week for 26 weeks. As a positive control, 10 mice of each sex received a single intraperitoneal injection of 75 mg/kg of N-methyl- N-nitrosourea. Bronchiolo-alveolar adenomas and adenocarcinomas were significantly increased in 1,2-DCE-treated rasH2 mice of both sexes, and bronchiolo-alveolar hyperplasias were significantly increased in female mice. Overall, almost all mice of each sex developed adenomas and/or adenocarcinomas with 100% of female rasH2 mice developing bronchiolo-alveolar adenocarcinomas.

Promotion of liver and kidney carcinogenesis by ethyl tertiary-butyl ether (ETBE) in male Wistar rats.

Tumor-promoting effects of ethyl tertiary-butyl ether (ETBE) were investigated in a 2-stage carcinogenesis bioassay with regard to hepatic and renal carcinogenesis in rats. Male 6-week-old Wistar rats were given drinking water containing N-ethyl-N-(2-hydroxyethyl)nitrosamine (EHEN), as an initiator, at a dose of 500 ppm for 2 weeks. Starting one week thereafter, the animals were administered ETBE at dose levels of 0 (control), 100, 300, 500 or 1,000 mg/kg/day by gavage for 19 weeks from week 4 to 22. Necropsy of all rats was performed at week 23, and livers and kidneys were examined histopathologically. Incidences of hepatocellular adenomas, and those of combined hepatocellular adenomas and carcinomas were significantly elevated in rats given 1,000 mg/kg/day ETBE, but not 100‒500 mg/kg/day ETBE, and there was a significant increase in the average numbers of lesions. No significant differences in incidences and average numbers of renal tubule neoplasms were found in rats administered 100‒1,000 mg/kg/day ETBE. However, the average numbers of atypical tubule hyperplasias, considered to be preneoplastic lesions, were significantly increased in rats given ETBE at 1,000 mg/kg/day, but not in rats given 500 mg/kg/day or lower doses. Thus, these results imply that ETBE has hepatic and renal tumor-promoting activities that affect EHEN-induced carcinogenesis in male rats, and the no-observed-effect level is 500 mg/kg/day under the present experimental conditions.

Multigenerational effects of whole body exposure to 2.14 GHz W-CDMA cellular phone signals on brain function in rats.

The present experimental study was carried out with rats to evaluate the effects of whole body exposure to 2.14 GHz band code division multiple access (W-CDMA) signals for 20 h a day, over three generations. The average specific absorption rate (SAR, in unit of W/kg) for dams was designed at three levels: high (<0.24 W/kg), low (<0.08 W/kg), and 0 (sham exposure). Pregnant mothers (4 rats/group) were exposed from gestational day (GD) 7 to weaning and then their offspring (F1 generation, 4 males and 4 females/dam, respectively) were continuously exposed until 6 weeks of age. The F1 females were mated with F1 males at 11 weeks old, and then starting from GD 7, they were exposed continuously to the electromagnetic field (EMF; one half of the F1 offspring was used for mating, that is, two of each sex per dam and 8 males and 8 females/group, except for all offspring for the functional development tests). This protocol was repeated in the same manner on pregnant F2 females and F3 pups; the latter were killed at 10 weeks of age. No abnormalities were observed in the mother rats (F0 , F1 , and F2 ) and in the offspring (F1 , F2 , and F3 ) in any biological parameters, including neurobehavioral function. Thus, it was concluded that under the experimental conditions applied, multigenerational whole body exposure to 2.14 GHz W-CDMA signals for 20 h/day did not cause any adverse effects on the F1 , F2 , and F3 offspring.

No Promoting Effect of Ethyl Tertiary-butyl Ether (ETBE) on Rat Urinary Bladder Carcinogenesis Initiated with N-Butyl-N-(4-hydroxybutyl)nitrosamine.

The effects of ethyl tertiary-butyl ether (ETBE) on two-stage urinary bladder carcinogenesis in male F344 rats initiated with N-butyl-N-(4-hydroxybutyl)nitrosamine (BBN) were investigated at various dose levels with regard to possible promoting activity. Groups of 30 rats were given drinking water containing 500 ppm BBN, as an initiator, for 4 weeks and starting one week thereafter received ETBE by gavage (daily, 7 days/week) at dose levels of 0 (control), 100, 300, 500 or 1000 mg/kg/day until experimental week 36. No statistically significant differences in incidences of preneoplastic lesions, papillomas, and carcinomas of the urinary bladder were evident in rats treated with 100-1000 mg/kg/day ETBE as compared with control values. Furthermore, the average numbers of preneoplastic or neoplastic lesions per unit length of basement membrane in rats given 100-1000 mg/kg/day ETBE were also comparable to control values. However, papillomatosis of the urinary bladder was found in 4 out of 30 rats (13%) in the group given 1000 mg/kg/day ETBE, and soft stones in the urinary bladder were found in 3 out of these 4 rats. The results thus demonstrated that ETBE did not exert promotional activity on urinary bladder carcinogenesis. However, papillomatosis of the urinary bladder developed in small numbers of the rats given ETBE at 1000 mg/kg/day but not in rats given 500 mg/kg/day or lower doses.

Intratumoral IL-12 gene therapy results in the crosspriming of Tc1 cells reactive against tumor-associated stromal antigens.

HLA-A2 transgenic mice bearing established HLA-A2(neg) B16 melanomas were effectively treated by intratumoral (i.t.) injection of syngeneic dendritic cells (DCs) transduced to express high levels of interleukin (IL)-12, resulting in CD8(+) T cell-dependent antitumor protection. In this model, HLA-A2-restricted CD8(+) T cells do not directly recognize tumor cells and therapeutic benefit was associated with the crosspriming of HLA-A2-restricted type-1 CD8(+) T cells reactive against antigens expressed by stromal cells [i.e., pericytes and vascular endothelial cells (VEC)]. IL-12 gene therapy-induced CD8(+) T cells directly recognized HLA-A2(+) pericytes and VEC flow-sorted from B16 tumor lesions based on interferon (IFN)-γ secretion and translocation of the lytic granule-associated molecule CD107 to the T cell surface after coculture with these target cells. In contrast, these CD8(+) T effector cells failed to recognize pericytes/VEC isolated from the kidneys of tumor-bearing HHD mice. The tumor-associated stromal antigen (TASA)-derived peptides studied are evolutionarily conserved and could be recognized by CD8(+) T cells harvested from the blood of HLA-A2(+) normal donors or melanoma patients after in vitro stimulation. These TASA and their derivative peptides may prove useful in vaccine formulations against solid cancers, as well as, in the immune monitoring of HLA-A2(+) cancer patients receiving therapeutic interventions, such as IL-12 gene therapy.

Enhancement in specific CD8+ T cell recognition of EphA2+ tumors in vitro and in vivo after treatment with ligand agonists.

The EphA2 receptor tyrosine kinase is an attractive therapeutic target that is commonly overexpressed on solid tumors, with the degree of overexpression associated with disease progression, metastatic potential, and poor prognosis. Agonistic mAbs or ligand (ephrinA1)-Fc fusion protein are capable of inducing EphA2 internalization and degradation, thereby (at least transiently) eliminating the influence of this oncoprotein. We and others have also shown that EphA2 contains multiple peptide epitopes that can be recognized by effector CD4(+) and CD8(+) T cells isolated from tumor-bearing patients. Herein, we show that "agonist" reagents that trigger the proteasome-dependent degradation of tumor cell EphA2 result in the improved presentation of peptides derived from (both the extracellular and intracellular domains of) EphA2 in MHC class I complexes expressed on the tumor cell membrane for at least 48 h, as manifested by increased recognition by EphA2-specific CD8(+) T cells in vitro. We also observed that while delivery of ephrinA1-Fc fusion protein or agonist mAb into EphA2(+) tumor lesions promotes EphA2 degradation in situ, this single administration of agent does not dramatically alter tumor progression in a humanized SCID model. However, when combined with the adoptive transfer of normally nontherapeutic (human) anti-EphA2 CD8(+) CTL, this dual-agent regimen results in complete tumor eradication. These results suggest that strategies targeting the conditional proteasome-mediated destruction of tumor cell EphA2 may enable EphA2-specific CD8(+) T cells (of modest functional avidity) to realize improved therapeutic potential.

Inter-laboratory comparison of pulmonary lesions induced by intratracheal instillation of NiO nanoparticle in rats: Histopathological examination results.

OBJECTIVE: In this study, in order to investigate the usefulness of intratracheal instillation in assessing the pulmonary toxicity of nanomaterials, intratracheal instillation of nickel oxide-nanoparticles (NiO-NP) was performed. METHODS: In this study, rats were administered test materials by intratracheal instillation at five different research institutions in order to assess the validity of using intratracheal instillation for hazard identification of nanomaterials. Eight-week-old male SD rats were administered NiO-NP dispersed in deionized water by a single intratracheal instillation at doses of 0 (vehicle control), 0.2, 0.67, and 2 mg/kg BW. Three days after instillation, histopathological examination of the lungs was performed. RESULTS: NiO-NP was distributed in the vicinity of hilus of the lung and in the alveoli around the bronchioles. Histopathological changes such as degeneration/necrosis of macrophages, inflammation, and proliferation of type II pneumocyte in the lung were observed, and their severity corresponded with increasing dose. The histopathological observations of pulmonary toxicity were almost similar at each institution. CONCLUSION: The similarity of the histopathological changes observed by five independent groups indicates that intratracheal instillation can be a useful screening method to detect the pulmonary toxicity of nanomaterials.

Maternal exposure to anti-androgenic compounds, vinclozolin, flutamide and procymidone, has no effects on spermatogenesis and DNA methylation in male rats of subsequent generations.

To verify whether anti-androgens cause transgenerational effects on spermatogenesis and DNA methylation in rats, gravid Crl:CD(SD) female rats (4 or 5/group, gestational day (GD) 0=day sperm detected) were intraperitoneally treated with anti-androgenic compounds, such as vinclozolin (100 mg/kg/day), procymidone (100 mg/kg/day), or flutamide (10 mg/kg/day), from GD 8 to GD 15. Testes were collected from F1 male pups at postnatal day (PND) 6 for DNA methylation analysis of the region (210 bp including 7 CpG sites) within the lysophospholipase gene by bisulfite DNA sequencing method. F0 and F1 males underwent the sperm analysis (count, motility and morphology), followed by DNA methylation analysis of the sperm. Remaining F1 males were cohabited with untreated-females to obtain F2 male pups for subsequent DNA methylation analysis of the testes at PND 6. These analyses showed no effects on spermatogenesis and fertility in F1 males of any treatment group. DNA methylation status in testes (F1 and F2 pups at PND 6) or sperms (F1 males at 13 weeks old) of the treatment groups were comparable to the control at all observation points, although DNA methylation rates in testes were slightly lower than those in sperm. In F0 males, no abnormalities in the spermatogenesis, fertility and DNA methylation status of sperm were observed. No transgenerational abnormalities of spermatogenesis and DNA methylation status caused by anti-androgenic compounds were observed.

Effects of gestational exposure to 1.95-GHz W-CDMA signals for IMT-2000 cellular phones: Lack of embryotoxicity and teratogenicity in rats.

The present study was designed to evaluate whether gestational exposure to an EMF targeting the head region, similar to that from cellular phones, might affect embryogenesis in rats. A 1.95-GHz wide-band code division multiple access (W-CDMA) signal, which is one applied for the International Mobile Telecommunication 2000 (IMT-2000) system and used for the freedom of mobile multimedia access (FOMA), was employed for exposure to the heads of four groups of pregnant CD(SD) IGS rats (20 per group) for gestational days 7-17. The exposure was performed for 90 min/day in the morning. The spatial average specific absorption rate (SAR) for individual brains was designed to be 0.67 and 2.0 W/kg with peak brain SARs of 3.1 and 7.0 W/kg for low (group 3) and high (group 4) exposures, respectively, and a whole-body average SAR less than 0.4 W/kg so as not to cause thermal effects due to temperature elevation. Control and sham exposure groups were also included. At gestational day 20, all dams were killed and fetuses were taken out by cesarean section. There were no differences in maternal body weight gain. No adverse effects of EMF exposure were observed on any reproductive and embryotoxic parameters such as number of live (243-271 fetuses), dead or resorbed embryos, placental weights, sex ratios, weights or external, visceral or skeletal abnormalities of live fetuses.

Improving immunotherapy by conditionally enhancing MHC class I presentation of tumor antigen-derived Peptide epitopes.

Tumors represent an altered self cell type that can be recognized by both the host humoral (B cells, antibodies) and cellular (T cells) adaptive immune systems. Because most known tumor-associated antigens (TAA) recognized by T cells represent overexpressed or aberrantly expressed proteins, which are not mutated and to which tolerance has been developed, the anti-TAA T-cell repertoire available to the cancer patient is of moderate-to-low avidity. Specific vaccinations typically amplify the absolute number of such T cells, but may have little consequence on improving their functional avidity, which may fall below a critical threshold required for effective recognition of tumor cells in situ. This review will discuss methods to improve low-avidity T-cell recognition of cancer cells by manipulating the tumor cells themselves to conditionally express higher levels of TAA-derived peptide epitopes presented in major histocompatibility (MHC) complexes. This may facilitate the design and performance of novel combinational therapies for the effective treatment of a broad range of cancer types.

Modifying effects of chitin, chitosan and their related compounds on 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) in a rat medium-term hepatocarcinogenesis model, and their post-initiation effects in a female rat 2-stage multi-organ carcinogenesis model.

The modifying effects of chitin, chitosan, chitin-oligo sugar, chitosan-oligo sugar and chlorophyllin-chitosan on 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) was investigated in a rat medium-term hepatocarcinogenesis model. Male F344 rats were injected with diethylnitrosamine (DEN) and starting 2 weeks later, received 0.03% MeIQx alone, MeIQx plus each chemical (0.4%), or each chemical alone (0.1%) in diet for 6 weeks. Three weeks after the DEN injection, animals were subjected to 2/3 partial hepatectomy. The numbers and areas of glutathione S-transferase placental form (GST-P) positive foci given MeIQx plus test chemicals were similar to the MeIQx alone values. In a second experiment, post-initiation effects of chitin and chitosan on major organs were examined in female F344 rats after initiation with 1,2-dimethylhydrazine (DMH), 7,12-dimethylbenz[a]anthracene (DMBA) and 2,2'-dihydroxy-di-n-propylnitrosamine (DHPN). In rats fed a diet containing 1.0% chitin for 36 weeks, the development of palpable mammary tumors tended to be delayed and the final incidence and multiplicity of adenocarcinomas, were significantly lowered. However, in the colon, the number of aberrant crypt foci (ACF) in the chitin and chitosan groups was significantly increased. These results indicate that chitin, chitosan and related compounds do not exert unequivocal chemopreventive effects on heterocyclic amine-induced hepatocarcinogenesis, and that effects in other organs may be tissue specific with possible inhibitory action in the mammary gland being offset by promotion of colon lesion development.

A 90-day oral toxicity study of purple corn color, a natural food colorant, in F344 rats.

A subchronic oral toxicity study of purple corn color (PCC), a natural food colorant, was performed with groups of 10 male and 10 female F344 rats fed the agent at dietary levels of 0%, 0.5%, 1.5% and 5.0% for 90 days. No mortalities occurred during the treatment period. No treatment-related changes in the body weight, food and water consumption, ophthalmology, hematology, organ weight data and histopathology were observed. Regarding general conditions and gross pathology, staining of fur and black feces were noted in rats of the 1.5% and 5.0% diet groups. Moreover, brown urine and black material in the stomach, small and large intestine were evident in rats receiving 5.0%. These changes were considered due to the anthocyanin content. On clinical chemistry analysis, total cholesterol, phospholipid and triglyceride were significantly lowered in both sexes of the 5.0% group, but these were not considered to be toxicologically significant. Thus, the No-observed-adverse-effect-level (NOAEL) was judged to be 5.0% in diet for both sexes (male: 3542 mg/kg/day, female: 3849 mg/kg/day) for PCC under the present experimental conditions.