Tumors In Syrian Hamsters Research Articles

Tumours in 177 pet hamsters.

Even though tumours are considered to occur frequently in pet hamsters, there is only a small number of scientific reports in current literature. Pathological reports from 177 hamsters were evaluated. Of these, 78 were male and 75 were female. Median age of affected hamsters was 12 months (range 2-34). Integumental tumours were the most common neoplasms (62%, 109/177). As far as species was known, the number of Syrian hamsters (52%, 30/58) affected by tumours seemed to be lower than the number of affected dwarf hamsters (85%, 47/55). Tumours of the hematopoietic system were the second most frequently neoplasms (17%, 30/177). Relative number of neoplasms of the endocrine system, tumours of the digestive system (1.7%, 3/177) and other tumours (4%, 7/177 each) was low. The majority of integumental tumours were epithelial (66%; 91/126). This study aimed to analyze data from veterinary surgeries and pathological institutes about the occurrence of spontaneous tumours in Syrian hamsters and dwarf hamsters to give information about the frequency of tumours, prognosis and survival time. This is the first study about tumours in pet hamsters in Germany so far.

The Efficacy of Oncolytic Adenovirus Is Mediated by T-cell Responses against Virus and Tumor in Syrian Hamster Model.

Oncolytic adenoviruses (Ad) represent an innovative approach to cancer therapy. Its efficacy depends on multiple actions, including direct tumor lysis and stimulation of antiviral and antitumor immune responses. In this study, we investigated the roles of T-cell responses in oncolytic adenoviral therapy. An immunocompetent and viral replication-permissive Syrian hamster tumor model was used. The therapeutic mechanisms of oncolytic Ad were investigated by T-cell deletion, immunohistochemical staining, and CTL assay. Deletion of T cells with an anti-CD3 antibody completely demolished the antitumor efficacy of oncolytic Ad. Intratumoral injection of Ad induced strong virus- and tumor-specific T-cell responses, as well as antiviral antibody response. Both antiviral and antitumor T-cell responses contributed to the efficacy of oncolytic Ad. Deletion of T cells increased viral replication and extended the persistence of infectious virus within tumors but almost abrogated the antitumor efficacy. Preexisting antiviral immunity promoted the clearance of injected oncolytic Ad from tumors but had no effect on antitumor efficacy. Strikingly, the repeated treatment with oncolytic Ad has strong therapeutic effect on relapsed tumors or tumors insensitive to the primary viral therapy. These results demonstrate that T cell-mediated immune responses outweigh the direct oncolysis in mediating antitumor efficacy of oncolytic Ad. Our data have a high impact on redesigning the regimen of oncolytic Ad for cancer treatment. Clin Cancer Res; 23(1); 239-49. ©2016 AACR.

Syngeneic Syrian hamster tumors feature tumor-infiltrating lymphocytes allowing adoptive cell therapy enhanced by oncolytic adenovirus in a replication permissive setting

ABSTRACTAdoptive transfer of tumor-infiltrating lymphocytes (TIL) has shown promising yet sometimes suboptimal results in clinical trials for advanced cancer, underscoring the need for approaches improving efficacy and safety. Six implantable syngeneic tumor cell lines of the Syrian hamster were used to initiate TIL cultures. TIL generated from tumor fragments cultured in human interleukin-2 (IL-2) for 10 d were adoptively transferred into tumor-bearing hamsters with concomitant intratumoral injections of oncolytic adenovirus (Ad5-D24) for the assessment of antitumor efficacy. Pancreatic cancer (HapT1) and melanoma (RPMI 1846) TIL exhibited potent and tumor-specific cytotoxicity in effector-to-target (E/T) assays. MHC Class I blocking abrogated the cell killing of RPMI 1846 TIL, indicating cytotoxic CD8+ T-cell activity. When TIL were combined with Ad5-D24 in vitro, HapT1 tumor cell killing was significantly enhanced over single agents. In vivo, the intratumoral administration of HapT1 TIL and Ad5-D24 resulted in improved tumor growth control compared with either treatment alone. Additionally, splenocytes derived from animals treated with the combination of Ad5-D24 and TIL killed autologous tumor cells more efficiently than monotherapy-derived splenocytes, suggesting that systemic antitumor immunity was induced. For the first time, TIL of the Syrian hamster have been cultured, characterized and used therapeutically together with oncolytic adenovirus for enhancing the efficacy of TIL therapy. Our results support human translation of oncolytic adenovirus as an enabling technology for adoptive T-cell therapy of solid tumors.

The effects of radiation on antitumor efficacy of an oncolytic adenovirus vector in the Syrian hamster model

We report that radiation enhances the antitumor efficacy of the oncolytic adenovirus vector VRX-007 in Syrian hamster tumors. We used tumor-specific irradiation of subcutaneous tumors and compared treatment options of radiation alone or combined with VRX-007 and cyclophosphamide (CP). Radiation therapy further augmented the VRX-007-mediated inhibition of tumor growth, in both CP-treated and non-CP-treated hamsters, even though radiation did not lead to increased viral replication in tumors when compared to those treated with VRX-007 alone. Moreover, tumor growth inhibition was similar in tumors irradiated either one week before or after injection with VRX-007, which suggests that radiation exerts its antitumor effect independently from vector therapy. Thus, our results demonstrate that these two therapies do not have to be provided simultaneously to enhance their combined effectiveness against subcutaneous hamster tumors.

The role of cyclophosphamide in enhancing antitumor efficacy of an adenovirus oncolytic vector in subcutaneous Syrian hamster tumors

We have previously reported that intratumoral injection of VRX-007—an Ad5-based vector overexpressing ADP (Adenovirus Death Protein)—can suppress the growth of subcutaneous HaK (hamster renal cancer) tumors. VRX-007 replication and tumor growth inhibition are enhanced when the hamsters are immunosuppressed by a high dose of cyclophosphamide (CP), an immunosuppressive and chemotherapeutic agent. Here we report that continuous immunosuppression with CP was not required for increased oncolytic activity of VRX-007 because short-term dosing or continuous dosing with the drug yielded similar antitumor results. Prolonged viral replication was found only in animals on continuous CP treatment. We used 007-Luc, a replication-competent, luciferase-expressing vector similar to VRX-007 to investigate the replication of the vector over time. Tumor growth inhibition was similar in hamsters given CP treatment either one week before or one week after 007-Luc injection, which suggests that CP exerts its antitumor efficacy independently of vector therapy. 007-Luc did not spread far from the inoculation site, even in immunosuppressed, CP-treated animals. Our results indicate that the enhanced effectiveness that is produced by the combination of VRX-007 and CP therapies is due to their two independent mechanisms and that they do not have to be given simultaneously for the improved outcome shown.

A Novel Therapeutic Regimen to Eradicate Established Solid Tumors with an Effective Induction of Tumor-Specific Immunity

The efficacy of oncolytic viruses depends on multiple actions including direct tumor lysis, modulation of tumor perfusion, and stimulation of tumor-directed immune responses. In this study, we investigated whether a sequential combination of immunologically distinct viruses might enhance antitumor efficacy through the induction of tumor-specific immunity and circumvention or mitigation of antiviral immune responses. The Syrian hamster as an immune-competent model that supports replication of both adenovirus and vaccinia virus was evaluated in vitro and in vivo. The antitumor efficacy of either virus alone or sequential combination of the two viruses was examined in pancreatic and kidney cancer models. The functional mechanism of the regimen developed here was investigated by histopathology, immunohistochemistry staining, CTL assay, and T-cell depletion. The Syrian hamster is a suitable model for assessment of oncolytic adenovirus and vaccinia virus. Three low doses of adenovirus followed by three low doses of vaccinia virus resulted in a superior antitumor efficacy to the reverse combination, or six doses of either virus alone, against pancreatic and kidney tumors in Syrian hamsters. A total of 62.5% of animals bearing either tumor type treated with the sequential combination became tumor-free, accompanied by the induction of effective tumor-specific immunity. This enhanced efficacy was ablated by CD3+ T-cell depletion but was not associated with humoral immunity against the viruses. These findings show that sequential treatment of tumors with oncolytic adenovirus and vaccinia virus is a promising approach for cancer therapy and that T-cell responses play a critical role.

Imaging study of pancreatic ductal adenocarcinomas in Syrian hamsters using X‐ray micro‐computed tomography (CT)

X-ray computed tomography (CT) has been used for diagnoses of human pancreatic cancer. Although micro-CT is a useful approach to evaluate macromorphology of organs/tissue also in animal models, reports on pancreatic tumors are limited. In this study, the utility of micro-CT was assessed in characterizing chemically induced pancreatic tumors in Syrian hamsters. Hamsters treated with or without N-nitrosobis(2-oxopropyl)amine (BOP) were injected with the antispasmodic agent, scopolamine butylbromide, and contrast agents, 5 or 10 mL/kg body weight of iopamidol or Fenestra VC at 18-38 weeks, then examined by micro-CT scanning with a respiratory gating system. Both peristaltic and respiratory movements were substantially suppressed by the combination of scopolamine butylbromide treatment and the respiratory gating system, resulting in improvements of image qualities. Iopamidol clearly visualized the pancreatic parenchyma and contrasted the margins among the pancreas and other abdominal organs/tissue. Meanwhile Fenestra VC predominantly contrasted abdominal vascular systems, but the margins among pancreas and other organs/tissue remained obscure. Six pancreatic tumors of 4-13 mm in diameter were detected in four of 15 animals, but not the five tumors of 1-4 mm in diameter. The inner tumor images were heterogeneously or uniformly visualized by iopamidol and Fenestra VC. Overall, iopamidol could clearly contrast between pancreatic parenchyma and the tumors as compared with Fenestra VC. All tumors confirmed were histopathologically diagnosed as pancreatic ductal adenocarcinomas. Thus, micro-CT could be useful to evaluate the carcinogenic processes and preventive methods of pancreatic cancer in hamsters and to assess the novel contrast agents for detection of small pancreatic cancer in humans.

Aurora A and B Overexpression and Centrosome Amplification in Early Estrogen-Induced Tumor Foci in the Syrian Hamster Kidney: Implications for Chromosomal Instability, Aneuploidy, and Neoplasia

Estrogen-induced Syrian hamster tumors in the kidney represent a useful model to gain insight into the role of estrogens in oncogenic processes. We provided evidence that early tumor foci in the kidney arise from interstitial ectopic uterine-like germinal stem cells, and that early tumor foci and well-established tumors are highly aneuploid (92-94%). The molecular mechanisms whereby estrogens mediate this process are unclear. Here, we report that estrogen treatment induced significant increases in Aurora A protein expression (8.7-fold), activity (2.6-fold), mRNA (6.0-fold), and Aurora B protein expression (4.6-fold) in tumors, compared with age-matched cholesterol-treated kidneys. Immunohistochemistry revealed that this increase in Aurora A and B protein expression was essentially confined to cells within early and large tumor foci at 3.5 and 6 months of estrogen treatment, respectively. Upon estrogen withdrawal or coadministration of tamoxifen for 10 days, a 78% to 79% and 81% to 64% reduction in Aurora A and B expression, respectively, were observed in primary tumors compared with tumors continuously exposed to estrogens. These data indicate that overexpressed Aurora A and B in these tumors are under estrogen control via estrogen receptor alpha. Aurora A coenriched with the centrosome fraction isolated from tumors in the kidney. Centrosome amplification (number and area/cell) was detected in early tumor foci and large tumors but not in adjacent uninvolved or age-matched control kidneys. Taken together, these data indicate that persistent overexpression of Aurora A and B is under estrogen control, and is coincident with centrosome amplification, chromosomal instability, and aneuploidy, and represent an important mechanism driving tumorigenesis.

Targeting Interferon-α Increases Antitumor Efficacy and Reduces Hepatotoxicity of E1A-mutated Spread-enhanced Oncolytic Adenovirus

Novel approaches are needed to improve the antitumor potency and to increase the cancer specificity of oncolytic adenoviruses (Ad). We hypothesized that the combination of interferon-alpha (IFN-α) expression with a specific mutation in the e1a gene of Ad could target vector replication to genetic defects in the IFN-α pathway resulting in both improved antitumor efficacy and reduced toxicity. The conditionally replicative Ad vector KD3-IFN carries the dl1101/1107 mutation in the e1a gene that eliminates binding of E1A proteins to p300/CBP and pRb. KD3-IFN expresses human IFN-α in concurrence with vector replication and overexpresses the adenovirus death protein (ADP; E3-11.6K). The antitumor activity of KD3-IFN was significantly higher than that of a control vector in established human hepatocellular carcinoma tumors in immunodeficient mice and in hamster kidney cancer tumors in immunocompetent Syrian hamsters. The dl1101/1107 mutation rendered Ad replication sensitive to the antiviral effect of IFN-α in normal as opposed to cancer cells. These results translated to reduced vector toxicity upon systemic administration to C57BL/6 mice. The combination of Ad oncolysis, ADP overexpression, and IFN-α-mediated immunotherapy represents a three-pronged approach for increasing the anticancer efficacy of replicative Ads. Exploiting the dl1101/1107 mutation provides a mechanism for additional selectivity of IFN-α-expressing replication-competent Ads.

Reexpression of Reduced VEGF Activity in Liver Metastases of Experimental Pancreatic Cancer

Vascular endothelial growth factor (VEGF) is thought to play a crucial role in the process of cancer growth and metastasis. In this study, the expression of VEGF in liver metastases of pancreatic cancer was investigated using an established hamster model. Pancreatic cancer cells (PGHAM-1, 1 x 10(6)) derived from N-nitrosobis (2-oxopropyl) amine (BOP)-induced pancreatic tumors in Syrian golden hamsters were transplanted into the pancreas of female hamsters. All hamsters were sacrificed at 21 days after transplantation and used for the histopathological examination of pancreatic and metastatic lesions (primary transplantation model). The metastatic liver tumors were minced with scissors and 1 mm(3) tumors were retransplanted into the pancreas of a second hamster. All hamsters were sacrificed 21 days after retransplantation, and the pancreatic tumors were removed (back transplantation model). Immunohistochemical analyses using antibody against VEGF were performed for all pancreatic and liver tumors. Reverse transcription-polymerase chain reaction (RT-PCR) was performed to examine the expression of VEGF mRNA in the tumors. In addition, we investigated the proliferation of each tumor using Ag-NOR staining. In the primary transplantation models, VEGF expression in the pancreatic tumors was positive, but that in the liver metastases was only weakly positive or negative. On the other hand, VEGF expression in the pancreatic tumors that had developed from the retransplantation of the liver tumors (back transplantation model) was strongly positive. VEGF mRNA was expressed in the pancreatic tumors of both primary and back transplantation models. In the metastatic liver tumors of the primary transplantation model, VEGF mRNA was expressed in all cases, although the immunohistochemical staining pattern was weakly positive or negative. Similarly, in the metastatic liver tumor of the back transplantation model, VEGF mRNA was expressed in all cases, although the immunohistochemical staining pattern was weakly positive or negative. No significant differences in Ag-NOR scores were found between the models. Our results suggest that VEGF expression usually occurs in PGHAM-1 cells but that VEGF expression is reduced during the process of liver metastasis and revived by retransplantation. Thus, the interrelationship between cancer cells and the organ environment might play an important role in VEGF expression.

FREQUENT P16INK4A/CDKN2A ALTERATIONS IN CHEMICALLY INDUCED SYRIAN GOLDEN HAMSTER PANCREATIC TUMORS.

The p16INK4A/CDKN2A (p16) tumor suppressor gene is known to be inactivated in up to 98% of human pancreatic cancer specimens. Chemically induced pancreatic tumors in Syrian golden hamsters have been demonstrated to share many morphological and biological similarities with human pancreatic tumors and represent a potentially suitable model for the evaluation of therapies targeting p16. The purpose of this study was to evaluate primary hamster pancreatic tumor specimens for potentially inactivating p16 alterations. Tumors were induced with N-nitrosobis-(2-oxopropyl)amine, and were harvested on day 100. Foci of tumor cells were identified by light microscopy after staining with hematoxylin and eosin, and corresponding tumor tissues were excised for DNA extraction. The techniques of multiplex real-time PCR, direct sequencing and methylation specific PCR were used to evaluate 30 tumor specimens for homozygous deletions, mutations and aberrant methylation of 5′ CpG islands, respectively. Homozygous deletions were identified in 11 of 30 (36.7%) specimens, mutations were identified in four of 30 (13.3%) specimens, and aberrant methylation of 5′ CpG islands was found in 14 of 30 (46.7%) specimens. The overall frequency of p16 alterations was 93.3% (28 of 30 specimens) and the majority of changes (83.3%) were noted to be secondary to methylation or homozygous deletion. The four mutations significantly impaired cyclin-dependent kinase 4 inhibitory activity, and two resulted in perturbation of the global structure of P16 protein. These findings indicate that p16 inactivation is a common event in chemically induced hamster tumors, and that this animal model is appropriate for comparative studies evaluating pancreatic cancer therapeutic strategies targeting p16.

Age, sex and co-exposure to N-ethyl-N-nitrosourea influence mutations in the Alu repeat sequences in diethylstilbestrol-induced kidney tumors in Syrian hamsters.

We report, for the first time, mutations in the Alu repeat regions in the genome of kidney tumors induced by diethylstilbestrol in Syrian hamsters. Among the 66 loci amplified by 11 random primers, 28 loci exhibited insertions, deletions or losses or gains in intensity in the genome of kidney tumor tissues compared with normal kidney tissues from age-matched hamsters. Higher numbers of mutated Alu loci were observed in the tumors of old hamsters compared with young hamsters. In N-ethyl-N-nitrosourea- and diethylstilbestrol-treated hamsters deletion of a 0.59 kb locus amplified with primer OPC03 was observed in most of the female hamsters, but not in male hamsters. An insertion mutation of a 0.498 kb locus amplified with primer OPC03 was observed in 12 of 36 diethylstilbestrol-induced kidney tumors. The cloning and sequencing of the 0.498 kb locus amplified with primer OPC03 revealed that it had significant sequence similarity to the mouse RIKEN cDNA clone. These findings indicate that age, sex and co-exposure to N-ethyl-N-nitrosourea influence mutations in the Alu repeat sequences in the genome of diethylstilbestrol-induced kidney tumors in Syrian hamsters. Structural alterations in Alu repeats in critical target genes may be involved in diethylstilbestrol-induced carcinogenesis.

Frequent p16INK4A/CDKN2A alterations in chemically induced Syrian golden hamster pancreatic tumors.

The p16INK4A/CDKN2A (p16) tumor suppressor gene is known to be inactivated in up to 98% of human pancreatic cancer specimens. Chemically induced pancreatic tumors in Syrian golden hamsters have been demonstrated to share many morphological and biological similarities with human pancreatic tumors and represent a potentially suitable model for the evaluation of therapies targeting p16. The purpose of this study was to evaluate primary hamster pancreatic tumor specimens for potentially inactivating p16 alterations. Tumors were induced with N-nitroso-bis-(2-oxopropyl) amine, followed by two cycles of augmentation pressure, and were harvested on day 100. Foci of tumor cells were identified by light microscopy after staining with hematoxylin and eosin, and corresponding tumor tissues were excised for DNA extraction. The techniques of multiplex real-time PCR, direct sequencing and methylation-specific PCR were used to evaluate 30 tumor specimens for homozygous deletions, mutations and aberrant methylation of 5' CpG islands, respectively. Homozygous deletions were identified in 11 of 30 (36.7%) specimens, mutations were identified in four of 30 (13.3%) specimens, and aberrant methylation of 5' CpG islands was found in 14 of 30 (46.7%) specimens. The overall frequency of p16 alterations was 93.3% (28 of 30 specimens) and the majority of changes (83.3%) were noted to be secondary to methylation or homozygous deletion. The four mutations significantly impaired cyclin-dependent kinase 4 inhibitory activity, and two resulted in perturbation of the global structure of P16 protein. These findings indicate that p16 inactivation is a common event in chemically induced hamster tumors, and that this animal model is appropriate for comparative studies evaluating pancreatic cancer therapeutic strategies targeting p16.

Expression and characterization of Syrian golden hamster p16, a homologue of human tumor suppressor p16INK4A

The p16 INK4A / CDKN2A tumor suppressor gene is known to be inactivated in up to 98% of human pancreatic cancer specimens and represents a potential target for novel therapeutic intervention. Chemically induced pancreatic tumors in Syrian golden hamsters have been demonstrated to share many morphologic and biological similarities with human pancreatic tumors and this model may be appropriate for studying therapies targeting p16 INK4A / CDKN2A. The purpose of this study was to investigate the fundamental biochemistry of hamster P16 protein. Using both in vivo and in vitro approaches, the CDK4 binding affinity, kinase inhibitory activity, and thermodynamic stability of hamster and human P16 proteins were evaluated. Furthermore, a structural model of hamster P16 protein was generated. These studies demonstrate that hamster P16 protein is biochemically indistinguishable from human P16 protein. From a biochemical perspective, these data strongly support the study of p16-related pancreatic oncogenesis and cancer therapies in the hamster model.

The abortive infection of Syrian hamster cells with human adenovirus type 12.

Human adenovirus type 12 (Ad12) induces undifferentiated tumors in newborn Syrian hamsters, and this tumor model has been investigated in detail in our laboratory. One of the characteristics of the Ad12-hamster cell system is a strictly abortive infection cycle. In this chapter, we summarize previous and more recent results of studies on the interaction of Ad12 with the nonpermissive BHK21 hamster cell line. The block of Ad12 replication lies before viral DNA replication and late gene transcription which cannot be detected with the most sensitive techniques. Ad12 adsorption, cellular uptake and transport of the viral DNA to the nucleus are less efficient in the nonpermissive hamster cells than in permissive human cells. However, most of the early functions of the Ad12 genome are expressed in BHK21 cells, though at a low level. In the downstream region, the first exon, of the major late promoter (MLP) of Ad12 DNA, a mitigator element of 33 nucleotide pairs in length has been identified which contributes to the inactivity of the MLP in hamster cells and its markedly decreased activity in human cells. The E1 functions of Ad2 or Ad5 are capable of partly complementing the Ad12 deficiencies in hamster cells in that Ad12 viral DNA replication and late gene transcription can proceed, e.g. in a BHK hamster cell line, BHK297-C131,which carries in an integrated form and constitutively expresses the E1 region of Ad5 DNA. Nevertheless, the late Ad12 mRNAs, which are synthesized in this system with the authentic nucleotide sequence, fail to be translated to structural viral proteins. Hence, infectious virions are not produced in the partly complementing system. Probably there is also a translational block for late Ad12 mRNAs in hamster cells. We have recently shown that the overexpression of the Ad12 preterminal protein (pTP) gene or of the E1A gene facilitates the synthesis of full-length, authentic Ad12 DNA in BHK21 cells infected with Ad12. Apparently the pTP has a hitherto unknown function in eliciting full cycles of Ad12 DNA replication even in nonpermissive BHK21 cells when sufficient levels of Ad12 pTP are produced. We pursue the possibility that the completely abortive infection cycle of Ad12 in hamster cells ensures the survival of Ad12-induced hamster tumor cells which all carry, integrated in their genomes, multiple copies of Ad12 DNA. In this way, the viral genomes are immortalized and expanded in a huge number of tumor cells.

Causation and prevention of solely estrogen-induced oncogenesis: similarities to human ductal breast cancer.

Estrogens are intimately involved in the causation of some of the most prevalent cancers afflicting women, particularly, breast, endometrial, cervico-vaginal, and possibly ovarian. Therefore, it has become particularly pertinent to elucidate the molecular changes and mechanisms whereby estrogens elicit their oncogenic actions so that better prevention strategies can be developed. The estrogen-induced Syrian hamster tumors of the kidney have emerged as one of the most intensively studied in-vivo models in solely estrogen-induced oncogenesis. An advantage of this model is that the tumors occur in the absence of any intervening morphologic changes, but rather they are the result of the continuous progression of a subset of interstitial stem cells in the kidney leading to tumor formation. Evidence is presented that the origin of these tumors is derived from ectopic "uterine" stem cells, which are responsive to estrogenic hormones. The other animal tumor model studied is the highly sensitive estrogen-induced mammary tumors of female ACI rats. Their steroid receptor and other gene alterations have been delineated. Importantly, a crucial early event in this solely estrogen-induced oncogenic process, common to both animal tumor models, is the overexpression and amplification of c-myc and its protein product. Chromosomal instability, in both early and large well-established frank tumors, is another important characteristic found during early E-induced oncogenesis. These features have been shown to be characteristic of human ductal carcinomas in-situ and in primary invasive ductal breast carcinomas. The molecular alterations seen are considered crucial in eliciting estrogen-induced oncogenesis and have established for the first time a direct causal link between estrogen and the induction of chromosomal instability and aneuploidy in these estrogen-associated neoplasms.

Effect of the single major proteic fractions of the liver perchloric extract UK101 on the development of oral tumours in Syrian hamsters

Squamous cell carcinoma of the oral cavity continues to be a major clinical problem, with about 100,000 new deaths each year worldwide. There is therefore a need to search for new tools to aid oral cancer treatment. We tested the inhibitory activity on chemical carcinogenesis of the three principal protein fractions of about 50, 14, and 8.5 kDa of the mixture UK101 derived from goat liver. These are composed principally of a glycoprotein rich in mannose residues, a protein with analogy to the heat shock protein family, and ubiquitin, respectively. The animal model employed was dimethylbenzanthracene-induced hamster cheek pouch carcinoma. Number of tumours per animal, tumour mass per animal, and proliferating cell nuclear antigen (PCNA) in non-tumour mucosa were quantified: the 14-kDa fraction was the most active; this was also confirmed by testing its corresponding recombinant material. The 50-kDa fraction was inactive, while the ubiquitin showed only low inhibitory activity. It is possible that the technique described and the results obtained could lead to an interesting clinical approach to the treatment of oral cancer.

Role of iron in estrogen-induced cancer.

Redox cycling of catecholestrogen metabolites between quinone and catechol forms is a mechanism of generating potentially mutagenic oxygen radicals in estrogen-induced carcinogenesis. Consistent with this concept, multiple forms of oxygen radical-generated DNA damage are induced by estrogen in cell-free systems, in cells in culture and in rodents prone to estrogen-induced cancer. Metal ions, specifically iron, are necessary for the production of hydroxy radicals. Iron has not received much attention in discussions of estrogen-induced carcinogenesis and human hormone-associated cancer, and is the focus of this review. An elevated dietary iron intake enhances the incidence of carcinogen-induced mammary cancer in rats and estrogen-induced kidney tumors in Syrian hamsters. Estrogen administration increases iron accumulation in hamsters and facilitates iron uptake by cells in culture. In humans, elevated body iron storage has been shown to increase the risk of several cancers including breast cancer. A role of iron in hormone-associated cancer in humans offers attractive routes for cancer prevention by regulating metal ion metabolism and interfering with iron accumulation in tissues.

Immunohistochemical analysis of diethylstilbestrol-induced renal tumors in adult male Syrian hamsters: evidence for relationship to peripheral nerve sheath tumors.

Estrogen-induced Syrian hamster kidney tumors (SHKT) are widely used as experimental models for the study of hormonal and renal carcinogenesis. In order to characterize the direction of differentiation of SHKT, kidney sections of diethylstilbestrol (DES)-treated hamsters (1-11 months) were analyzed by immunohistochemistry using a panel of lineage-specific markers. The first tumorous buds found in animals exposed to DES for 4-6 months exhibited prominent S100, Leu-7, and vimentin immunoreactivities. Immunopositivities for neuron-specific enolase, PGP 9.5, desmin, and glial fibrillary acidic protein were mostly detected in medium-sized and large tumors after prolonged exposure to DES (> 6 months). All neoplasms, irrespective of the size and the duration of treatment, appeared negative for cytokeratin, neurofilaments, synaptophysin, and CD99 antibodies. Western blotting confirmed to a large extent the immunohistochemical observations. The systematic analysis of serial kidney sections by confocal microscopy after double immunostaining for S100 and neurofilaments revealed that early neoplastic buds could stem from S100-positive cells associated with nerves bundles. Altogether, these observations suggest that DES-induced SHKT could be related to malignant peripheral nerve sheath tumor and originate from a yet unidentified precursor cell present in the sheath of peripheral nerves.

The fingerprints of the host innate immunity on the cells of primary virus-induced tumors

As shown earlier, the cells transformed in vitro by various oncogenes, during subsequent in vivo growth were gradually replaced by descendant tumor cells, which co-expressed highly increased H 2O 2-catabolizing antioxidant activity (H 2O 2 CA), and the ability to release PGE 2 (PGE S) in contact with natural killer cells; v-src was the only oncogene, which in vitro induced cells transformation characterised with the expression of [H 2O 2 CA+PGE S] phenotype. Expression of [H 2O 2 CA+PGE S] phenotype was providing tumor cells with significantly increased resistance to cytotoxic activities of macrophages and NK cells. However, the possible involvement of [H 2O 2 CA+PGE S] phenotype in primary carcinogenesis remained obscure. Here, using three models of the primary virus-induced Syrian hamster tumors we demonstrated that Rous Sarcoma Virus-induced tumors arising after short latent period expressed [H 2O 2 CA + PGE S] phenotype at appearance. During the latent periods of SV40- and SA7(C8)-induced tumors the cells expressing [H 2O 2 CA+PGE S] phenotype gradually replaced the original [H 2O 2 CA+PGE S]-phenotype-negative cell populations. The effectiveness of such selection correlated with the duration of in vivo tumor development. Thus it was shown, that selection of tumor cells expressing [H 2O 2 CA+PGE S] phenotype is beginning and may be completed during the latent period of primary carcinogenesis. Taken together, data of this and preceding our studies on [H 2O 2 CA+PGE S] phenotype demonstrate that in vivo the host innate immunity antitumor reactions are apparently responsible for the selection of rare tumor cell variants capable to defend themselves against CTA of Mph and NK.