Dual source hybrid spectral micro-CT using an energy-integrating and a photon-counting detector.

Preclinical micro-CT provides a hotbed in which to develop new imaging technologies, including spectral CT using photon counting detector (PCD) technology. Spectral imaging using PCDs promises to expand x-ray CT as a functional imaging modality, capable of molecular imaging, while maintaining CT's role as a powerful anatomical imaging modality. However, the utility of PCDs suffers due to distorted spectral measurements, affecting the accuracy of material decomposition. We attempt to improve material decomposition accuracy using our novel hybrid dual-source micro-CT system which combines a PCD and an energy integrating detector. Comparisons are made between PCD-only and hybrid CT results, both reconstructed with our iterative, multi-channel algorithm based on the split Bregman method and regularized with rank-sparse kernel regression. Multi-material decomposition is performed post-reconstruction for separation of iodine (I), gold (Au), gadolinium (Gd), and calcium (Ca). System performance is evaluated first in simulations, then in micro-CT phantoms, and finally in an in vivo experiment with a genetically modified p53fl/fl mouse cancer model with Au, Gd, and I nanoparticle (NP)-based contrasts agents. Our results show that the PCD-only and hybrid CT reconstructions offered very similar spatial resolution at 10% MTF (PCD: 3.50 lp mm-1; hybrid: 3.47 lp mm-1) and noise characteristics given by the noise power spectrum. For material decomposition we note successful separation of the four basis materials. We found that hybrid reconstruction reduces RMSE by an average of 37% across all material maps when compared to PCD-only of similar dose but does not provide much difference in terms of concentration accuracy. The in vivo results show separation of targeted Au and accumulated Gd NPs in the tumor from intravascular iodine NPs and bone. Hybrid spectral micro-CT can benefit nanotechnology and cancer research by providing quantitative imaging to test and optimize various NPs for diagnostic and therapeutic applications.

Checkpoint blockade immunotherapy reshapes the high-dimensional phenotypic heterogeneity of murine intratumoural neoantigen-specific CD8+ T cells.

The analysis of neoantigen-specific CD8+ T cells in tumour-bearing individuals is challenging due to the small pool of tumour antigen-specific T cells. Here we show that mass cytometry with multiplex combinatorial tetramer staining can identify and characterize neoantigen-specific CD8+ T cells in mice bearing T3 methylcholanthrene-induced sarcomas that are susceptible to checkpoint blockade immunotherapy. Among 81 candidate antigens tested, we identify T cells restricted to two known neoantigens simultaneously in tumours, spleens and lymph nodes in tumour-bearing mice. High-dimensional phenotypic profiling reveals that antigen-specific, tumour-infiltrating T cells are highly heterogeneous. We further show that neoantigen-specific T cells display a different phenotypic profile in mice treated with anti-CTLA-4 or anti-PD-1 immunotherapy, whereas their peripheral counterparts are not affected by the treatments. Our results provide insights into the nature of neoantigen-specific T cells and the effects of checkpoint blockade immunotherapy.Immune checkpoint blockade (ICB) therapies can unleash anti-tumour T-cell responses. Here the authors show, by integrating MHC tetramer multiplexing, mass cytometry and high-dimensional analyses, that neoantigen-specific, tumour-infiltrating T cells are highly heterogeneous and are subjected to ICB modulations.

Eliminating roles for T-bet and IL-2 but revealing superior activation and proliferation as mechanisms underpinning dominance of regulatory T cells in tumors.

Foxp3(+) regulatory T cells (Tregs) are often highly enriched within the tumor-infiltrating T cell pool. Using a well-characterised model of carcinogen-induced fibrosarcomas we show that the enriched tumor-infiltrating Treg population comprises largely of CXCR3(+) T-bet(+) 'TH1-like' Tregs which are thymus-derived Helios(+) cells. Whilst IL-2 maintains homeostatic ratios of Tregs in lymphoid organs, we found that the perturbation in Treg frequencies in tumors is IL-2 independent. Moreover, we show that the TH1 phenotype of tumor-infiltrating Tregs is dispensable for their ability to influence tumor progression. We did however find that unlike Tconvs, the majority of intra-tumoral Tregs express the activation markers CD69, CD25, ICOS, CD103 and CTLA4 and are significantly more proliferative than Tconvs. Moreover, we have found that CD69(+) Tregs are more suppressive than their CD69- counterparts. Collectively, these data indicate superior activation of Tregs in the tumor microenvironment, promoting their suppressive ability and selective proliferation at this site.

Adaptations of Arginine's Intestinal-Renal Axis in Cachectic Tumor-Bearing Rats.

Malignancies induce disposal of arginine, an important substrate for the immune system. To sustain immune function, the tumor-bearing host accelerates arginine's intestinal-renal axis by glutamine mobilization from skeletal muscle and this may promote cachexia. Glutamine supplementation stimulates argi-nine production in healthy subjects. Arginine's intestinal-renal axis and the effect of glutamine supplementation in cancer cach-exia have not been investigated. This study evaluated the long-term adaptations of the interorgan pathway for arginine production following the onset of cachexia and the metabolic effect of glutamine supplementation in the cachectic state. Fischer-344 rats were randomly divided into a tumor-bearing group (n = 12), control group (n = 7) and tumor-bearing group receiving a glutamine-enriched diet (n = 9). Amino acid fluxes and net fractional extractions across intestine, kidneys, and liver were studied. Compared to controls, the portal-drained viscera of tumor-bearing rats took up significantly more glutamine and released significantly less citrulline. Renal metabolism was unchanged in the cachectic tumor-bearing rats compared with controls. Glutamine supplementation had no effects on intestinal and renal adaptations. In conclusion, in the cachectic state, an increase in intestinal glutamine uptake is not accompanied by an increase in renal arginine production. The adaptations found in the cachectic, tumor-bearing rat do not depend on glutamine availability.

[Effect of epsilon-aminocaproic acid, cyclophosphamide and their combination on the growth of autochthonous sarcomas of mice induced by benzo(a)pyrene].

Antifibrinolytic drug epsilon-aminocaproic acid as a therapeutic form (5% solution in saline) was tested for antitumor activity in the autochthonous subcutaneous tumors of mice, induced by benzo (a) pyrene, in monotherapy mode (instead animals received drinking water) and in combination with cyclophosphamide, which was administered once intraperitoneally in the dose of 200 mg/kg. In the control groups, treated with drinking water and saline solution instead of water, there was no stabilization and reduction in tumor volume, while in the groups receiving epsilon-aminocaproic acid, cyclophosphamide and their combination statistically significantly in comparison with the control groups there was increased the proportion of tumors with not changed or reduced volume; epsilon-aminocaproic acid enhanced the antitumor effect of cyclophosphamide. The data obtained are for further study of the antitumor effect of epsilon-aminocaproic acid.

Proteomic profiling of the hypothalamus in a mouse model of cancer-induced anorexia-cachexia.

BACKGROUND: Anorexia-cachexia is a common and severe cancer-related complication but the underlying mechanisms are largely unknown. Here, using a mouse model for tumour-induced anorexia-cachexia, we screened for proteins that are differentially expressed in the hypothalamus, the brain's metabolic control centre. METHODS: The hypothalamus of tumour-bearing mice with implanted methylcholanthrene-induced sarcoma (MCG 101) displaying anorexia and their sham-implanted pair-fed or free-fed littermates was examined using two-dimensional electrophoresis (2-DE)-based comparative proteomics. Differentially expressed proteins were identified by liquid chromatography-tandem mass spectrometry. RESULTS: The 2-DE data showed an increased expression of dynamin 1, hexokinase, pyruvate carboxylase, oxoglutarate dehydrogenase, and N-ethylmaleimide-sensitive factor in tumour-bearing mice, whereas heat-shock 70 kDa cognate protein, selenium-binding protein 1, and guanine nucleotide-binding protein Gα0 were downregulated. The expression of several of the identified proteins was similarly altered also in the caloric-restricted pair-fed mice, suggesting an involvement of these proteins in brain metabolic adaptation to restricted nutrient availability. However, the expression of dynamin 1, which is required for receptor internalisation, and of hexokinase, and pyruvate carboxylase were specifically changed in tumour-bearing mice with anorexia. CONCLUSION: The identified differentially expressed proteins may be new candidate molecules involved in the pathophysiology of tumour-induced anorexia-cachexia.

Immune microenvironment profiles of tumor immune equilibrium and immune escape states of mouse sarcoma.

Cancer immunoediting consists of three distinct phases: elimination, equilibrium and escape. Here, for the first time, we investigated the immune microenvironment profiles of tumor immune equilibrium and immune escape states in 3'-methylcholanthrene-induced murine sarcoma model. Our study indicates the relative balance of monocytic MDSCs and antitumor immunity cells (especially CTLs, NK cells and γδT cells) may involve in maintaining tumor cells in a state of immune-mediated dormancy. In addition, high percentages of Treg cells and PMN-MDSCs are associated with the tumor immune escape state - mice with progressing sarcomas. In summary, the relative balance of immune effector cells and suppressive populations in the tumor microenvironment may involve in determining the fate of tumors.

Modulation of antitumour immune responses by intratumoural Stat1 expression.

Signal transducer and activator of transcription 1 (Stat1) mediates anti-viral responses and cytokine-driven anti-proliferative, apoptotic and immunomodulatory activities. As de-regulated Stat1 function can affect tumour progression we sought to elucidate the effects of tumour cell-intrinsic Stat1 expression on immunosurveillance. Knockout of Stat1 enhanced the development of sarcomas induced by the chemical carcinogen 3-methylcholanthrene (MCA). Growth of transplanted MCA-induced Stat1⁻/⁻ sarcomas was suppressed in wild-type mice compared to growth in Stat1⁻/⁻ and immunocompromised recipients. Co-depletion of NK and CD8⁺ T cells from wild-type mice facilitated Stat1-deficient tumour growth whereas depletion of CD4⁺ T cells and CD8⁺ T cells did not. In vitro and in vivo analysis of the tumours implicated a role for NK cell-mediated, perforin-dependent killing of Stat1-deficient tumours. Interestingly, restoration of Stat1 expression in Stat1⁻/⁻ tumours resulted in diminished involvement of NK cells and increased contribution of CD8⁺ T cells in anti-tumour responses. Therefore, Stat1 expression within tumour cells modulated anti-tumour immune responses by altering the dominant immune effector cell involvement from NK cells to CD8⁺ T cells in the absence or presence of Stat1 respectively.

Inflammation- and tumor-induced anorexia and weight loss require MyD88 in hematopoietic/myeloid cells but not in brain endothelial or neural cells.

Loss of appetite is a hallmark of inflammatory diseases. The underlying mechanisms remain undefined, but it is known that myeloid differentiation primary response gene 88 (MyD88), an adaptor protein critical for Toll-like and IL-1 receptor family signaling, is involved. Here we addressed the question of determining in which cells the MyD88 signaling that results in anorexia development occurs by using chimeric mice and animals with cell-specific deletions. We found that MyD88-knockout mice, which are resistant to bacterial lipopolysaccharide (LPS)-induced anorexia, displayed anorexia when transplanted with wild-type bone marrow cells. Furthermore, mice with a targeted deletion of MyD88 in hematopoietic or myeloid cells were largely protected against LPS-induced anorexia and displayed attenuated weight loss, whereas mice with MyD88 deletion in hepatocytes or in neural cells or the cerebrovascular endothelium developed anorexia and weight loss of similar magnitude as wild-type mice. Furthermore, in a model for cancer-induced anorexia-cachexia, deletion of MyD88 in hematopoietic cells attenuated the anorexia and protected against body weight loss. These findings demonstrate that MyD88-dependent signaling within the brain is not required for eliciting inflammation-induced anorexia. Instead, we identify MyD88 signaling in hematopoietic/myeloid cells as a critical component for acute inflammatory-driven anorexia, as well as for chronic anorexia and weight loss associated with malignant disease.

The pharmacologic inhibition of the xc- antioxidant system improves the antitumor efficacy of COX inhibitors in the in vivo model of 3-MCA tumorigenesis.

The chemopreventive and therapeutic efficacy of the cyclooxygenase (COX) inhibitor ibuprofen (IB) and of sulfasalazine (SASP), a drug that targets the antioxidant xc- system, were exploited in the experimental model of 3-methylcholantrene (3-MCA)-induced mouse sarcoma. The chemopreventive treatments gave unsatisfactory results because administration of IB one day after the 3-MCA injection only slightly delayed the tumor development, whereas SASP dispensed under the same conditions resulted in accelerated tumorigenesis. Similarly, the therapeutic treatment with either drug, administrated daily from the tumor detection, decreased the proliferation rate of tumor cells and increased the survival of treated mice only at a low extent. Remarkably, the combined chemopreventive treatment with IB and therapeutic treatment with SASP displayed a better efficacy, with strong delay of sarcoma growth, reduced tumor size and increased survival of treated mice. The two drugs target not only tumor cells but also tumor-associated macrophages that were dramatically decreased in the tumor infiltrate of mice subjected to the combined treatment. The synergistic effects of the association between a broad anti-inflammatory compound, such as IB, and a redox-directed drug, such as SASP, shed new light in the role of inflammation and of the redox response in chemical tumorigenesis and point to the combined chemopreventive plus therapeutic treatment with IB and SASP as a promising novel approach for antitumor therapy.

The essential role of PIM kinases in sarcoma growth and bone invasion.

PIM kinases are a family of serine/threonine kinases composed of three different isoforms (PIM1, PIM 2 and PIM 3) that are highly homologous. Their expression is mediated by the JAK/STAT signalling pathway, providing survival and cell cycle transition signals. PIM kinases are heavily targeted for anticancer drug discovery. However, very little is known about the relative contribution of the different isoforms to the tumourigenesis process in vivo, and how their individual inhibition might affect tumour growth. Taking advantage of genetically modified mice, we explored whether the inhibition of specific isoforms is required to prevent sarcomas induced by 3-methylcholanthrene carcinogenic treatment. We found that absence of Pim2 and Pim3 greatly reduced sarcoma growth to a similar extent to the absence of all three isoforms. This model of sarcoma generally produces bone invasion by the tumour cells. Lack of Pim2 and Pim3 reduced tumour-induced bone invasion by 70%, which is comparable with the reduction of tumour-induced bone invasion in the absence of all three isoforms. Similar results were obtained in mouse embryonic fibroblasts (MEFs) derived from these knockout (KO) mice, where double Pim2/3 KO MEFs already showed reduced proliferation and were resistant to oncogenic transformation by the RAS oncogene. Our data also suggest an important role of Gsk3ß phosphorylation in the process of tumourigenesis.

Tumor-derived autophagosome vaccine: induction of cross-protective immune responses against short-lived proteins through a p62-dependent mechanism.

PURPOSE: Tumor-specific antigens of 3-methylcholanthrene (MCA)-induced sarcomas were defined by the narrow immune responses they elicited, which uniquely rejected the homologous tumor, with no cross-reactions between independently derived syngeneic MCA-induced tumors. This study examines whether an autophagosome-enriched vaccine derived from bortezomib-treated sarcomas can elicit an immune response that cross-reacts with other unique sarcomas. EXPERIMENTAL DESIGN: Mice were vaccinated with either MCA-induced sarcomas or autophagosomes derived from those tumors and later challenged with either homologous or nonhomologous sarcomas. In addition, 293 cells expressing a model antigen were used to understand the necessity of short-lived proteins (SLiP) in this novel vaccine. These findings were then tested in the sarcoma model. Autophagosomes were characterized by Western blotting and fluorescent microscopy, and their ability to generate immune responses was assessed in vitro by carboxyfluorescein succinimidyl ester dilution of antigen-specific T cells and in vivo by monitoring tumor growth. RESULTS: In contrast to a whole-cell tumor vaccine, autophagosomes isolated from MCA-induced sarcomas treated with a proteasome inhibitor prime T cells that cross-react with different sarcomas and protect a significant proportion of vaccinated hosts from a nonhomologous tumor challenge. Ubiquitinated SLiPs, which are stabilized by proteasome blockade and delivered to autophagosomes in a p62/sequestosome-dependent fashion, are a critical component of the autophagosome vaccine, as their depletion limits vaccine efficacy. CONCLUSION: This work suggests that common short-lived tumor-specific antigens, not physiologically available for cross-presentation, can be sequestered in autophagosomes by p62 and used as a vaccine to elicit cross-protection against independently derived sarcomas.

Present at the beginning: a personal reminiscence on the history of teriparatide.

The ability of parathyroid glandular extracts to stimulate bone acquisition in rodents was established in the 1920s, but interest in this action lay dormant for almost 50 years until application of contemporary laboratory methods permitted the large-scale production of an amino-terminal fragment of PTH, (1-34) hPTH (teriparatide), which was capable of carrying out all known actions of the full-length (1-84) PTH molecule. In the 1970s, largely stimulated by the efforts of a British pharmacologist, Dr. John Parsons, the scientific community began to revisit these anabolic actions and showed that single daily injections of teriparatide dramatically increased bone mass in several mammalian species and restored bone in oöphorectomized rats. Shortly thereafter, human studies confirmed a striking increase in trabecular bone mass and showed also that an important part of teriparatide's action is to increase cortical bone. Eli Lilly and Company conducted a formal registration trial in postmenopausal women with osteoporosis. The unexpected occurrence of osteosarcomas in Fisher 344 rats treated long-term with teriparatide provoked an abrupt cessation of that trial, but ambiguity concerning the relevance of this rat finding to human disease, combined with significant anti-fracture efficacy, led to FDA approval of teriparatide for men and postmenopausal women with osteoporosis "at high risk for fracture" in 2002. Subsequently, teriparatide has been approved also for treatment of patients with glucocorticoid-associated osteoporosis, and papers indicating utility of this agent for dental and orthopedic applications have begun to appear.

Indigofera aspalathoides protection against 20-methylcholanthrene-induced experimental fibrosarcoma growth after transplantation in rats - role of xenobiotic drug metabolizing enzymes.

A large number of active principles from traditional medicinal plants have been reported to have chemopreventive properties. In the present study, therapeutic efficacy of an aqueous extract of Indigofera aspalathoides against growth of transplanted experimental fibrosarcomas in Wistar strain male albino rats was tested. Tumors which appeared about six weeks after implantation were highly localized and were maintained by serial transplantation. Rats were divided into four groups. Group I served as normal control animals. Group II were fibrosarcoma bearing animals. Group III were animals with fibrosarcoma treated with Indigofera aspalathoides aqueous extracts at a dose of 250 mg/kg. b. w. per day for 30 days. Group IV animals were treated with aqueous extract of Indigofera aspalathoides alone. Reduction in tumor weight was noted in Group III as compared to II. The levels of cytochrome C in liver and kidney, the levels of cytochrome P450 and cytochrome b5 in liver microsomes, phase I biotransformation enzymes NADPH-cytochrome P450, NADPH-cytochrome b5, and aniline hydroxylase, and the phase II enzymes glutathione-S-transferase and UDP glucuronyl transferase indicated that their modulation played a role in the therapeutic efficacy of Indigofera aspalathoides against experimental fibrosarcoma.

Effects of IL-1 molecules on growth patterns of 3-MCA-induced cell lines: an interplay between immunogenicity and invasive potential.

The balance between inflammation and immunity is cardinal for the outcome of the malignant process. Local attenuated inflammatory responses mediated by innate cells may provide accessory signals for the development of acquired immunity against malignant cells. In contrast, excessive inflammatory responses accompany tumorigenesis and tumor invasiveness, by the induction of immunosuppression. In the present study, we have assessed the role of tumor cell-derived IL-1 in determining the invasive versus immunostimulatory potential of tumor cells. For this purpose, we have used 3-MCA-induced fibrosarcoma cell lines from IL-1 knockout (KO) versus control mice. Cell lines with no IL-1 failed to establish tumors in intact mice, while lines obtained from control mice were invasive and induced a potent angiogenic response. In contrast, cell lines from IL-1KO mice were more immunogenic. SDF-1 and IL-6, each induced by IL-1, were the two major cytokines whose levels differed in cell lines with or without IL-1. We could not detect differences in cell surface markers related to immunogenicity, such as MHC Class I, co-stimulatory, or adhesion molecules between both types of cells. However, more T-cells were observed at the inoculation site of tumor cells devoid of IL-1 and more pronounced parameters related to anti-tumor immunity were observed in the spleen (IL-12 and IFNgamma) of these mice, compared to mice bearing tumors derived from control mice, where host-derived IL-1 is present. In addition, injection of tumor cells devoid of IL-1, which failed to grow in mice, induced an anti-tumor cell immune memory, while in mice injected with tumor cells from control mice; no immune memory could be detected. From the results, it seems that IL-1 is a crucial factor in determining the balance between immunity and inflammation in tumor-bearing mice. This suggests that manipulation of IL-1 could be useful in anti-tumor therapy, by reducing invasiveness and promoting immunity against the malignant cells.

A critical analysis of the tumour immunosurveillance controversy for 3-MCA-induced sarcomas.

The cancer immunoediting hypothesis has gained significant footing over the past decade as a result of work performed using sarcomas induced by 3-methylcholanthrene (3-MCA) in mice. Despite the progress made by several groups in establishing evidence for the three phases of immunoediting (elimination, equilibrium and escape), there continues to be active controversy on the nature of interaction between spontaneously formed tumour cells and the immune system during the early phases of tumourigenesis. At the root of this controversy is conflicting and unresolved evidence spanning back to the 1970s regarding the incidence and frequency of 3-MCA-induced sarcomas in immunocompetent mice as compared to immunodeficient mice. In this mini review we provide a critical analysis of both sides of this controversy.

IFN-gamma-dependent type 1 immunity is crucial for immunosurveillance against squamous cell carcinoma in a novel mouse carcinogenesis model.

3-Methylcholanthrene (MCA)-induced sarcomas have been used as conventional tools for investigating immunosurveillance against tumor development. However, MCA-induced sarcoma is not always an ideal model for the study of the human cancer system because carcinomas and not sarcomas are the dominant types of human cancers. To resolve this problem, we established a novel and simple method to induce mouse squamous cell carcinomas (SCCs). As well known, the subcutaneous injection of MCA caused the formation of sarcomas at 100% incidence. However, we here first succeeded at inducing SCC at 60% of incidence within 2 months by a single intra-dermal injection of MCA. Using this primary SCC model, we demonstrated the critical role of interferon (IFN)-gamma-dependent type 1 immunity in immunosurveillance against SCC from the following results: (i) The incidence of SCC was accelerated in IFN-gamma-deficient mice compared with that in wild-type mice; (ii) In vivo injection of CpG-oligodeoxynucleotides (CpG-ODN) caused a marked reduction in the incidence of SCC in parallel with the activation of type 1-dependent antitumor immunity and (iii) The antitumor activity of CpG-ODN was significantly decreased in IFN-gamma-deficient mice. Thus, our established MCA-induced mouse SCC model could be a powerful tool for evaluating immunosurveillance mechanisms during the development of SCC and might result in a novel strategy to address immunosurveillance mechanisms of human cancer.

Differences in DNA damage and repair produced by systemic, hepatocarcinogenic and sarcomagenic dibenzocarbazole derivatives in a model of rat liver progenitor cells.

Liver progenitor (oval) cells are a potential target cell population for hepatocarcinogens. Our recent study showed that the liver carcinogens 7H-dibenzo[c,g]carbazole (DBC) and 5,9-dimethyldibenzo[c,g]carbazole (DiMeDBC), but not the sarcomagen N-methyldibenzo[c,g]carbazole (N-MeDBC), induced several cellular events associated with tumor promotion in WB-F344 cells, an in vitro model of liver oval cells [J. Vondracek, L. Svihalkova-Sindlerova, K. Pencikova, P. Krcmar, Z. Andrysik, K. Chramostova, S. Marvanova, Z. Valovicova, A. Kozubik, A. Gabelova, M. Machala, 7H-Dibenzo[c,g]carbazole and 5,9-dimethyldibenzo[c,g]carbazole exert multiple toxic events contributing to tumor promotion in rat liver epithelial 'stem-like' cells, Mutat. Res. Fundam. Mol. Mech. Mutagen. 596 (2006) 43-56]. In this study, we focused on the genotoxic effects generated by these dibenzocarbazoles in WB-F344 cells to better understand the cellular and molecular mechanisms involved in hepatocarcinogenesis. Lower IC(50) values determined for DBC and DiMeDBC, as compared with N-MeDBC, indicated a higher sensitivity of WB-F344 cells towards hepatocarcinogens. Accordingly, DBC produced a dose-dependent DNA-adduct formation resulting in substantial inhibition of DNA replication and transcription. In contrast, DNA-adduct number detected in DiMeDBC-exposed cells was almost negligible, whereas N-MeDBC produced a low level of DNA adducts. Although all dibenzocarbazoles significantly increased the level of strand breaks (p<0.05) and micronuclei (p<0.001) after 2-h treatment, differences in the kinetics of strand break rejoining were found. The strand break level in DiMeDBC- and N-MeDBC-exposed cells returned to near the background level within 24h after treatment, whereas a relatively high DNA damage level was detected in DBC-treated cells up to 48h after exposure. Additional breaks detected after incubation of DiMeDBC-exposed WB-F344 cells with a repair-specific endonuclease, along with a nearly 3-fold higher level of reactive oxygen species found in these cells as compared with control, suggest a possible role of oxidative stress in DiMeDBC genotoxicity. We demonstrated qualitative differences in the DNA damage profiles produced by hepatocarcinogens DBC and DiMeDBC in WB-F344 cells. Different lesions may trigger distinct cellular pathways involved in hepatocarcinogenesis. The low amount of DNA damage, together with an efficient repair, may explain the lack of hepatocarcinogenicity of N-MeDBC.

HER-2/neu mediated down-regulation of MHC class I antigen processing prevents CTL-mediated tumor recognition upon DNA vaccination in HLA-A2 transgenic mice.

To study DNA vaccination directed against human HER-2 in the HHD mouse Tg strain, we created a novel HER-2-expressing syngeneic tumor transplantation model. We found that a DNA vaccine encoding the full length HER-2 DNA protected HHD mice from HER-2(+) tumor challenge by a CTL independent mechanism. A more efficient approach to induce HLA-A2 restricted CTLs, through immunization with a multi-epitope DNA vaccine expressing the HLA-A2 restricted HER-2 369-377, 435-443 and 689-697 epitopes, resulted in high numbers of peptide specific T cells but failed to induce tumor protection. Subsequently we discovered that HER-2 transfected tumor cells down-regulated MHC class I antigen expression and exhibited a series of defects in the antigen processing pathway which impaired the capacity to produce and display MHC class I peptide-ligands to specific CTLs. Our data demonstrate that HER-2 transfection is associated with defects in the MHC class I presentation pathway, which may be the underlying mechanism behind the inability of CTLs to recognize tumors in this HLA-A2 transgenic model. As defective MHC class I presentation may be a common characteristic of HER-2 expressing tumors, vaccines targeting HER-2 should aim at inducing an integrated immune response where also CD4(+) T cells and antibodies are important components.

Early development of histiocytic sarcomas in p53 knockout mice treated with N-bis(2-hydroxypropyl)nitrosamine.

p53 knockout mice have been utilized for the functional analysis of p53 in carcinogenic processes and for the evaluation of the carcinogenic potential of chemicals. In this study, we established that p53 knockout mice have an elevated susceptibility to the induction of histiocytic sarcoma (HS) by N-bis(2-hydroxy-propyl)nitrosamine (BHP). p53 heterozygous (+/-) and wild-type (+/+) mice were treated with 20 or 200 ppm BHP in their drinking water for 15 weeks or with 20 ppm BHP for 40 weeks. An additional group of p53 nullizygous (-/-) mice were treated with 20 ppm BHP for 15 weeks. In a 15-week experiment, hepatic HSs were unexpectedly observed in BHP-treated p53 (-/-) mice (30.8%) but not in p53 (+/-) and (+/+) mice and untreated (-/-) mice, indicating that a complete loss of p53 dramatically accelerates the genesis of HS. In a 40-week experiment, HSs were significantly increased in female p53 (+/-) mice (37.5%) as compared with female (+/+) mice (5.0%). Additionally, PCR-SSCP and sequencing analysis revealed a high frequency of p53 gene mutations in HSs, demonstrating the involvement of p53 gene mutations in HS development. Our data add to the understanding of the carcinogenic susceptibility of p53 knockout mice, and may help to elucidate the pathogenesis of HS development.