Chromosome aberrations in cattle raised on bracken fern pasture

The role of bracken fern illudanes in bracken fern-induced toxicities

Bracken fern is carcinogenic when fed to domestic and laboratory animals inducing bladder and ileal tumours and is currently classified as a possible human carcinogen by IARC. The carcinogenic illudane, ptaquiloside (PTQ) was isolated from bracken fern and is widely assumed to be the major bracken carcinogen. However, several other structurally similar illudanes are found in bracken fern, in some cases at higher levels than PTQ and so may contribute to the overall toxicity and carcinogenicity of bracken fern. In this review, we critically evaluate the role of illudanes in bracken fern induced toxicity and carcinogenicity, the mechanistic basis of these effects including the role of DNA damage, and the potential for human exposure in order to highlight deficiencies in the current literature. Critical gaps remain in our understanding of bracken fern induced carcinogenesis, a better understanding of these processes is essential to establish whether bracken fern is also a human carcinogen.

Papillomaviruses: a systematic review

In the last decades, a group of viruses has received great attention due to its relationship with cancer development and its wide distribution throughout the vertebrates: the papillomaviruses. In this article, we aim to review some of the most relevant reports concerning the use of bovines as an experimental model for studies related to papillomaviruses. Moreover, the obtained data contributes to the development of strategies against the clinical consequences of bovine papillomaviruses (BPV) that have led to drastic hazards to the herds. To overcome the problem, the vaccines that we have been developing involve recombinant DNA technology, aiming at prophylactic and therapeutic procedures. It is important to point out that these strategies can be used as models for innovative procedures against HPV, as this virus is the main causal agent of cervical cancer, the second most fatal cancer in women.

Chromosome aberrations in cells infected with bovine papillomavirus: comparing cutaneous papilloma, esophagus papilloma, and urinary bladder lesion cells

The majority of malignant cells present genetic instability with chromosome number changes plus segmental defects: these changes involve intact chromosomes and breakage-induced alterations. Some pathways of chromosomal instability have been proposed as random breakage, telomere fusion, and centromere fission. Chromosome alterations in tumor cells have been described in animal models and in vitro experiments. One important question is about possible discrepancies between animal models, in vitro studies, and the real events in cancer cells in vivo. Papillomaviruses are relevant agents in oncogenic processes related to action on host genome. Recently, many reports have discussed the presence of virus DNA in peripheral blood, in humans and in animals infected by papillomaviruses. The meaning of this event is of controversy: possible product of apoptosis occurring in cancer cells, metastasized cancer cells, or active DNA sequences circulating in bloodstream. This study compares chromosome aberrations detected in bovine cells, in peripheral blood cells, and in BPV lesion cells: the literature is poor in this type of study. Comparing chromosome aberrations described in the different cells, a common mechanism in their origin, can be suggested. Furthermore blood cells can be evaluated as an effective way of virus transmission.

Cytogenetic studies in peripheral blood of bovines afflicted by papillomatosis

Ten types of bovine papillomavirus (BPV) have been described and there are reports of viral transmission via blood. The presence of viral DNA in lymphocytes was described to be associated with chromosome instability in these cells. This study presents an evaluation of chromosome instability in short-term peripheral lymphocyte cultures from cows presenting skin papillomatosis, compared with asymptomatic infected animals and non-infected healthy bovines. In a total of 2203 cells, 918 (42%) showed at least one chromosome aberration: 42.7 (± 7.8) in animals with papillomatosis (BPV + W), 40.2 (± 11) in asymptomatic animals (BPV-W) and 4 (± 2) in control animals. Significant differences were found between the infected group (with or without symptoms) and the control group (P < 0.0001). The increased frequencies of chromosome aberrations suggest an interaction between the virus and host cell chromatin.

A new, very sensitive method of assessment of ptaquiloside, the major bracken carcinogen in the milk of farm animals

We describe a new method to detect trace levels of ptaquiloside (Pta), a major carcinogen of bracken fern in biological samples such as milk from farm animals. The method involves the absorption of analyte on carbograph followed by elution with solvents mixtures. The unstable analyte is then converted into Br-Pt (II), which is specific for Pta, as it is not a natural decay product of the glycoside in aqueous media. An internal standard, the Br-pterosine-d₂, prepared in our laboratories has been used. Detection and quantification are possible with gas chromatography/mass spectrometry (GC/MS) in single ion monitoring mode (SIM). The detectable amount is in the range of ppb. The method allowed us to detect Pta not only in the milk from bracken fern-poisoned cattle but also, for the first time, in the milk from healthy farm animals such as sheep, goat, horse, and donkey mares.

Immunohistochemical Evaluation of Vascular Urinary Bladder Tumors from Cows with Enzootic Hematuria

Fifty-six endothelial-derived urinary bladder tumor samples collected from 26 animals with bovine enzootic hematuria were selected for immunohistochemical studies. Expression of factor VHI-related antigen (FVIIIra), CD31, muscle-specific actin, uroplakin III (UPIII), and the cell cycle-related proteins cyclin Dl and p53 was evaluated in hemangiomas, “hemangioendotheliomas” (a vascular tumor that histologically is intermediate in appearance between a hemangioma and a conventional hemangiosarcoma), and hemangiosarcomas. Although CD31 expression was seen in all endothelial tumors tested, FVIIIra was not expressed in poorly differentiated endothelial tumor cells from solid areas or in 7 muscle-invasive hemangiosarcomas. Cyclin Dl overexpression was seen in 53% of hemangiomas, 82% of hemangioendotheliomas, and 95% of hemangiosarcomas. P53 immunoreac-tivity was only seen in muscle-invasive hemangiosarcomas. The UPIII staining pattern, normally very intense on the apical aspect and cytoplasm of superficial urothelial cells, was altered in the urothelium in an estimated 25% of hemangiomas, most hemangioendotheliomas, and most hemangiosarcomas. In conclusion, CD31 is a better marker than FVIIIra in the characterization of bovine endothelial tumors. The cell cycle regulatory pathways involving cyclin Dl and p53 seem to be impaired in endothelial urinary bladder tumors, p53 immunoreactivity positively correlating with enhanced invasion.

Bovine papillomaviruses: their role in the aetiology of cutaneous tumours of bovids and equids

Bovine papillomavirus (BPV) is perhaps the most extensively studied animal papillomavirus. In cattle BPVs induce benign tumours of cutaneous or mucosal epithelia, called papillomas or warts. Cattle papillomas are benign tumours and generally regress without eliciting any serious clinical problems in the host, but occasionally persist and provide the focus for malignant transformation to squamous cell carcinoma, as in the case of cancer of the urinary bladder and cancer of the upper alimentary canal. BPV is the only papillomavirus that jumps species: the virus also infects equids, and gives rise to fibroblastic tumours called sarcoids. Sarcoids very rarely regress, more often they persist and can be locally aggressive. These tumours are the most common dermatological tumour of equids worldwide. The purpose of this review is to discuss the biology of BPV, the biology of bovine tumours and equine sarcoids, and present the current understanding of BPV in tumour pathogenesis in its natural host, cattle, and in its heterologous host, equids. Finally, the use of anti-BPV vaccines as a therapy for equine sarcoids will be discussed. Only limited information on the clinical or pathological aspects of either bovine or equine tumours will be provided as this subject has been extensively addressed previously.

Bovine papillomaviruses, papillomas and cancer in cattle

Bovine papillomaviruses (BPV) are DNA oncogenic viruses inducing hyperplastic benign lesions of both cutaneous and mucosal epithelia in cattle. Ten (BPV 1-10) different viral genotypes have been characterised so far. BPV 1-10 are all strictly species-specific but BPV 1/2 may also infect equids inducing fibroblastic tumours. These benign lesions generally regress but may also occasionally persist, leading to a high risk of evolving into cancer, particularly in the presence of environmental carcinogenic co-factors. Among these, bracken fern is the most extensively studied. The synergism between immunosuppressants and carcinogenic principles from bracken fern and the virus has been experimentally demonstrated for both urinary bladder and alimentary canal cancer in cows whose diets were based on this plant. BPV associated tumours have veterinary and agricultural relevance in their own right, although they have also been studied as a relevant model of Human papillomavirus (HPV). Recent insights into BPV biology have paved the way to new fields of speculation on the role of these viruses in neoplastic transformation of cells other than epithelial ones. This review will briefly summarise BPV genome organization, will describe in greater detail the functions of viral oncoproteins, the interaction between the virus and co-carcinogens in tumour development; relevant aspects of immunity and vaccines will also be discussed.

Bracken-fern extracts can be clastogenic or aneugenic depending on the tissue cell assay

The consumption of bracken fern (Pteridium aquilinum) as food is associated with a high incidence of cancer in humans and animals. We investigated the cytogenetic effects of bracken-fern extracts (hexane extract-HE, ethanol extract-EE, hot water extract-HWE and cold water extract-CWE) on chromosomes of peritoneal and bone-marrow cells of Swiss mice. In peritoneal cells, all four treatments (HE, EE, HWE and CWE) induced structural chromosome aberrations, but the EE also induced numerical chromosome aberrations. In bone-marrow cells both HE and CWE induced structural chromosome aberrations; additionally, the number of abnormal metaphases was higher in peritoneum than in bone marrow. We suggest that bracken fern induces cytogenetic damage through DNA strand breaks and affects chromosome segregation.

Bovine papillomavirus type 2 detection in the urinary bladder of cattle with chronic enzootic haematuria

The bovine papillomavirus type 2 (BPV-2) involvement in the aetiology of chronic enzootic haematuria associated to bracken fern ingestion has been suggested for a long time. However, a few reports have shown the presence of the BPV-2 in urinary bladder tumors of cattle. The aim of this study was to investigate the presence of the BPV-2 infection in the urinary bladder of cattle with chronic enzootic haematuria in Brazilian cattle herds. Sixty-two urinary bladders were collected from adult cattle in beef herds from the north region of the state of Paraná, Brazil. According to clinical and pathological finds the specimens were distributed in three groups: the group A was constituted by 22 urinary bladders with macroscopic lesions collected at necropsy of cattle with clinical signs of chronic enzootic haematuria; the group B by 30 urinary bladders with macroscopic lesions collected in a slaughterhouse of cows coming from bracken fern-endemic geographical region; and the group C (control) by 10 urinary bladders without macroscopic lesions collected from asymptomatic cattle in a bracken fern-free geographical region. By a semi-nested polymerase chain reaction (PCR) assay, with an internal control, a fragment of the BPV-2 L1 gene with 386 bp length was amplified in 36 (58%) urinary bladder. The rate of BPV-2 positive urinary bladders was 50% (11/22) for group A, 80% (24/30) for group B, and 10% (1/10) for group C (control). The rate of the positive results found in groups A and B that included urinary bladder samples with macroscopic lesions was 67% (35/52) and the detection of the BPV-2 in both groups was significantly higher (P < 0.05) than in the control group. RFLP with Rsa I and Hae III enzymes evaluated the specificity of the BPV-2 amplicons. The PCR internal control that amplified a 626 bp fragment of the ND5 gene of the bovine mitochondrial genome was amplified in all analyzed samples and excluded false-negatives or invalid results in the semi-nested PCR. These results suggest the BPV-2 involvement in the chronic enzootic haematuria aetiology and open the perspective of the development of new strategies for the control of this disease that is the major cause of economical losses in beef herds from many Brazilian geographical regions.

Differential susceptibility to chromatid breaks induced by bleomycin in sub-fertile and fertile bovines

The rate of chromatid breaks was studied in cows with a history of sub-fertility by means of a test based on measurement of the average of breaks induced in lymphocytes of peripheral blood cultures. Fourteen female specimens were divided into two groups: fertile and sub-fertile. Peripheral blood lymphocytes were cultured and prepared for cytogenetic analysis. Two types of culture were established for each animal to evaluate the response of peripheral blood lymphocyte cultures to the genotoxic effects of bleomycin. The first culture did not receive bleomycin treatment (spontaneous chromosome aberrations). Our results showed that median breaks per cell (b/c) (+/-semirange) for spontaneous culture of the fertile and sub-fertile animals and bleomycin sensitivity assay for fertile and sub-fertile animals were 0.00+/-0.06, 0.02+/-0.03, 0.08+/-0.05 and 0.22+/-0.09, respectively. There was no significant difference (P>0.05) in the chromosomal breakage in lymphocytes not exposed to bleomycin; however, in comparing the number of chromatid breaks per cell in cultures treated with bleomycin, the sub-fertile group showed a significantly higher (P<0.05) level than the fertile group. These findings have implications both for identifying cattle with less than optimum fertility as well as for providing potential avenues to study the origins of sub-fertility.

Chromosome Aberrations in Cattle with Chronic Enzootic Haematuria

Chromosomal aberrations were investigated in 56 cattle with chronic enzootic haematuria (CEH) raised on pastures giving access to bracken fern. Of these animals, 27 were slaughtered and showed neoplastic lesions of the urinary bladder. Tumour tissue from 11 of the 27 cattle contained bovine papillomavirus type 2 (BPV-2) DNA. Increased numbers of chromosomal aberrations were seen in all animals with CEH, as compared with 30 control cattle that had had no access to bracken fern. The highest clastogenic effect was observed in cattle with urinary bladder cancer and evidence of BPV-2 DNA, suggesting that BPV-2 and bracken fern act synergistically in the production of chromosomal instability. In 19 of 20 animals with CEH, two bracken fern toxic compounds (quercitin and ptaquiloside) were demonstrated in urine, serum and milk.

Bovine papillomavirus and cancer

Bovine papillomavirus (BPV) induces papillomas of cutaneous or mucosal epithelia in cattle. The papillomas are benign tumours and generally regress, but occasionally persist and provide the focus for malignant transformation to squamous cell carcinoma, particularly in the presence of environmental cofactors. This has been experimentally demonstrated for BPV-2 and cancer of the urinary bladder, and BPV-4 and cancer of the upper alimentary canal in cattle feeding on bracken fern. In this review, several aspects of the biology of the virus are described including viral genome structure, regulation of transcription of the viral oncogenes, function of the viral oncoproteins, cooperation between virus and chemical cofactors in carcinogenesis, virus latency and prophylactic and therapeutic vaccination programmes.

Synergism between bovine papillomavirus type 4 and the flavonoid quercetin in cell transformation in vitro

Bovine papillomavirus type 4 (BPV-4) morphologically transforms primary bovine cells in vitro only in the presence of an activated ras gene. The transformed cells are capable of anchorage-independent growth, but are not immortal and are incapable of inducing tumors in nude mice, suggesting that other events are needed to convert the cells to the fully transformed phenotype. We show here that treatment of the cells with a single dose of the flavonoid quercetin leads to full oncogenic transformation of cells transfected with BPV-4 and ras. Quercetin is one of the most potent mutagens found in bracken fern, the environmental cofactor in BPV-4-associated carcinogenesis of the upper alimentary canal of cattle. Our results point to quercetin as the probable in vivo cocarcinogen synergizing with BPV-4 in malignant progression.