K-ras activation in non-small cell lung cancer in the dog.

To investigate the role of K-ras mutations in canine non-small cell lung cancer, we first determined the nucleotide sequence of the normal canine K-ras gene and then examined 21 canine lung tumors for activating K-ras mutations. Canine K-ras was analyzed by direct sequencing of polymerase chain reaction products generated with oligonucleotide primers derived from the human K-ras sequence. Four nucleotide differences were found between the canine and human K-ras sequence from position 5 to 211. The deduced amino acid sequence of the canine gene was identical to that of the human. Activated K-ras alleles were detected in 5 of the 21 canine lung tumors examined. The activating lesions were point mutations, predominantly in codon 12. Of the 14 adenocarcinomas examined, 2 (14%) had K-ras mutations. Two of 5 (40%) adenosquamous carcinomas and the only large cell carcinoma also contained activated alleles. The overall frequency of K-ras point mutation in non-small cell lung cancer (25%) is similar to that reported in human non-small cell lung cancer. We conclude that K-ras activation by point mutation is associated with, but not necessary for, non-small cell lung cancer development in the dog.

Sequence analysis of canine p53 in the region of exons 3-8.

An 828 base pair region of canine wild-type p53, corresponding to codons 25 through 312 in the human p53 gene, was directly sequenced from asymmetric polymerase chain reaction (PCR) products. The deduced amino acid sequence of the dog was 86%, 73% and 83% homologous to that of the cat, mouse and human proteins, respectively. In the evolutionarily conserved domains II through V, the canine sequence approached 100% homology with the human sequence. The region sequenced encompasses exons 3-8 where the majority of mutations have been identified in neoplastic specimens from human patients.

Analysis of the equine tumor suppressor gene p53 in the normal horse and in eight cutaneous squamous cell carcinomas.

Wild type equine p53 was amplified between exons 2 and 9 by the polymerase chain reaction using primers designed from conserved regions in other species. An 828 base pair region, corresponding to codons 25-313 of human p53, was sequenced in both directions. Human and equine amino acid sequences were 87% homologous in this region and 96% homologous in conserved domains II-V. Of eight equine cutaneous or mucocutaneous squamous cell carcinomas directly sequenced from exons 5-8, two had p53 point mutations resulting in single amino acid substitutions.

K-ras mutations in 239PuO2 canine lung neoplasms.

Single-strand conformational polymorphism (SSCP) analysis and direct sequencing methods were used to examine lung tumors derived from a cohort of beagle dogs with inhalational exposures to 239PuO2. These exposures were done at Pacific Northwest Laboratories where 18-month-old beagle dogs were given 239PuO2 by single-dose inhalation and allowed to live out their life-spans. Formalin-fixed paraffin-embedded blocks of tissues from 25 dogs exposed to 239PuO2 by aerosol inhalation which later developed lung tumors were available for this study. Two of 25 tumors had mutations within exon 1 of K-ras detected by SSCP analysis. Both mutations were GGT to GAT transitions at codon 12 confirmed by direct sequencing experiments. One was an adenocarcinoma from the medium-high exposure group and the other was a broncheolo-alveolar carcinoma from the medium-low exposure group. The rate of K-ras mutations in plutonium-induced lung tumors described herein (8%) was greater than previously described in canine plutonium-induced lung tumors (0%), but was less than that which we have described in spontaneous canine lung cancer (16%), less than that reported for human spontaneous non-small cell lung cancer (13-36%) and less than that described in rats with spontaneous lung cancer (40%) or lung tumors following 239Pu inhalation exposure (46%).

Canine and bovine ras family expression detected and discriminated by use of polymerase chain reaction.

Cellular proto-oncogenes are highly conserved genes thought to be critical in cell growth and differentiation. In this study, we used human sequence designed oligonucleotide primers to detect and discriminate c-Ha-ras-1, c-Ki-ras-2 and c-N-ras genes of dogs and cows by polymerase chain reaction (PCR) amplification of genomic DNA (DNA/PCR). Further, we have applied PCR for analysis of expressed mRNA transcribed from the RAS genes (RNA/PCR).

Detection of mammalian and avian hepadnaviruses by the polymerase chain reaction.

The hepadnavirus family contains a number of related viruses able to infect a variety of animal species. In the present study, we have used the polymerase chain reaction and oligonucleotide primers to a conserved region of the viral replicase gene of hepadnaviruses to identify viral sequences in de novo tissues in three well-characterized hepadnavirus systems: the woodchuck, ground squirrel and Pekin duck. We did not detect related hepadnavirus sequences in liver specimens from tree squirrels putatively infected with the tree squirrel hepatitis virus, or in liver specimens from horses with hepatitis (serum sickness), or from dogs with chronic active hepatitis or hepatocellular carcinoma.

Clostridium difficile: a survey of fecal carriage in cats in a veterinary medical teaching hospital.

Fecal samples collected from 245 cats over a 6-month period were analyzed for the presence of Clostridium difficile. After culture on selective media, isolates were identified by a latex agglutination test, and the presence of toxin A and toxin B gene sequences was determined by polymerase chain reaction. Clostridium difficile was isolated from 23 (9.4%) of the cats, and 34.8% of that group were colonized with toxigenic strains. All of the cats colonized with toxigenic C. difficile had > or = 1 of the risk factors (antibiotic use, antineoplastic therapy, immunosuppressive virus infection) associated with C. difficile infection in humans. Clostridium difficile was not found in any of the cats from a clinically healthy outpatient group of cats examined from the same hospital nor in cats from a specific-pathogen-free research colony on the same campus tested during the same time period. The data obtained in this study confirm the presence of C. difficile in cats at a veterinary teaching hospital. DNA fingerprinting analysis of these isolates allowed separation of the strains into 5 groups. Type 4 strain found in 7 cats was also recovered from the floor drain in the same hospital, suggesting a possible source of infection. Whether the organism is of clinical significance in diarrheal diseases of cats remains to be determined.

Proliferation indices in spontaneous canine lung cancer: proliferating cell nuclear antigen (PCNA), Ki-67 (MIB1) and mitotic counts.

Proliferation indices were measured for specimens from 55 spontaneous canine lung tumours, collected by surgical biopsy from clinical patients and archived in paraffin wax blocks. These indices were then related to the mitotic index and histological type of the tumour. Proliferating cell nuclear antigen (PCNA) and Ki-67 (MIB1) proteins were detected immunohistochemically with a biotin-streptavidin amplified detection system on a representative tissue section from each tumour. Five adjacent, non-overlapping fields were selected at random, and 200 cells per field were examined in each section. For PCNA, cells were classified subjectively into negative, weak or strong reactivity groups, based on nuclear staining. MIB1 cells were classified as negative or positive, based on nuclear staining. Mitotic figures were counted in anti-PCNA-labelled and anti-MIB1-labelled sections, in the same tumour areas as those in which indices were established. Mitotic counts were also done on haematoxylin and eosin-stained tissue sections. Linear regression analysis showed that all PCNA, MIB1 and mitotic indices had highly significant positive correlations (P<0.0001) with each other. Adenosquamous and squamous cell carcinomas differed from other histological tumour types in having significantly higher proliferation indices. These data suggest that growth rates for lung tumours in the dog vary according to histological type. On the basis of differences in proliferation indices and the distribution of immunoreactivity between histological subtypes in this study, it would seem that immunohistochemical detection of PCNA and MIB/1 reactivity and analysis of mitotic figures in routinely processed tissues may be useful in the diagnosis of lung tumours. 1999 W.B. Saunders and Company Ltd.

Amelogenin expression in canine oral tissues and lesions.

Amelogenins are major enamel proteins within the enamel extracellular matrix. The expression of amelogenin was confirmed in neonatal tissues of the canine jaw. The sequence of a portion of canine amelogenin cDNA, within exons 5 and 6, was determined and found to be closely homologous to sequences reported in the cow, pig, mouse and human being. Two acanthomatous epulides collected from clinically affected dogs showed amelogenin expression, whereas 22 other canine oral lesions, including six additional acanthomatous epulides, did not show amelogenin expression. Examination of structural proteins may allow precise identification of the histogenesis of the odontogenic neoplasms, which are often difficult to distinguish by means of morphological criteria alone.

Acute reactions in dogs treated with doxorubicin: increased frequency with the use of a generic formulation.

During a 4-month period, 34 dogs with tumors received a total of 60 doses of a single generic formulation of doxorubicin; 13 acute drug reactions were observed in these 34 dogs, and no acute reactions were observed after replacing the product with the proprietary brand. These reactions were characterized by one or more of the following signs: pruritus; head-shaking; urticaria; erythema of the pinnal, axillary, or inguinal regions; vocalization; vomiting; hyperemic or pale mucous membranes; high heart rate; and high respiratory rate. We propose that a component unique to generic doxorubicin was responsible for the unusually high number of acute drug reactions observed.

Evaluation of single-agent mitoxantrone as chemotherapy for relapsing canine lymphoma.

Many chemotherapeutic regimens will induce remission in dogs with lymphoma, but almost all dogs suffer relapse. Mitoxantrone was selected for evaluation as single-agent chemotherapy for relapsing canine lymphoma based on its use in humans undergoing salvage chemotherapy for non-Hodgkin's lymphoma and its tumoricidal effect against canine lymphoma. Dogs entered into study had multicentric lymphoma, and all had been treated solely with a standard combination chemotherapy protocol. At 1st relapse, all dogs were again staged and underwent lymph node biopsy. Mitoxantrone was administered IV at 6 mg/m2 every 21 days. Dogs were evaluated for lymphadenopathy before each dose of mitoxantrone. Fifteen dogs were entered into study. The average age (+/- SEM) of the dogs studied was 7.7 +/- 0.91 years, and most dogs were large (mean +/- SEM weight, 24.44 +/- 2.15 kg). Twelve dogs (80%) had B-cell lymphoma, and 3 had T-cell lymphoma. Dogs were staged IV (n = 12) or V (n = 3). The median duration of chemotherapy before entry into the study was 98 days. Overall median duration of response after mitoxantrone chemotherapy was 21 days. Complete responses were attained in 7 of 15 dogs (47%) with a median response duration of 84 days. Nine of 15 (60%) dogs attained a complete remission with additional chemotherapy after failing mitoxantrone chemotherapy. Mild toxicities were observed after mitoxantrone administration. No adverse reactions were observed during mitoxantrone infusions. The results of this study demonstrate that mitoxantrone, as a single agent, has limited value for dogs with lymphoma at 1st relapse after conventional multidrug chemotherapy.

Nucleotide sequence of canine c-N-ras: codons 1 to 71.

The c-N-ras gene has been implicated often in the genesis and/or progression of human leukemias. To our knowledge, the sequence of this gene in the dog has not been reported. Using a system of asymmetric reamplification of double-stranded polymerase chain reaction (PCR) products, we have sequenced normal canine c-N-ras mRNA from position -26 to +213, including codons 12, 13, and 61, which are the sites where oncogenic mutations are most commonly observed. The canine c-N-ras sequence has close homology with the human sequence in this area; there were only 6 observed base differences in nucleotide sequence and none resulted in a change of the encoded amino acid. The results of this study set the stage for directed searches for c-N-ras mutations in experimentally induced and naturally acquired neoplasms of the dog.

Computer-assisted image analysis of intratumoral vessel density in mammary tumors from dogs.

OBJECTIVE: To determine whether intratumoral microvessel density can be used to distinguish benign from malignant mammary tumors in dogs and to predict the outcome of surgical treatment for small volume (< 3-cm diameter) tumors. SAMPLE POPULATION: Tissue sections from 58 mammary tumors (42 malignant and 16 benign) from dogs. PROCEDURE: Mammary tumors were stained by immunohistochemistry for factor VIII-related antigen. Computer-assisted image analysis was used to determine intratumoral vessel density in immunostained areas. Total vascular density (TVD), calculated from 3 non-overlapping fields, was analyzed for correlation with patient or tumor histomorphologic characteristics, and results obtained by surgical treatment of small volume tumors. RESULTS: Mean TVD of malignant tumors was significantly greater than that of benign tumors. Total vascular density was not correlated with patient age, sex, reproductive status, clinical tumor stage, or histologic type. For small volume (< 3-cm diameter) malignant tumors, mean TVD was higher in tumors that recurred after surgery than in tumors that did not recur; however, TVD was not predictive of time to recurrence. CONCLUSION AND CLINICAL IMPLICATIONS: Immunohistochemistry and computer-assisted image analysis allowed objective quantitation of intratumoral microvessel density in formalin-fixed, paraffin-embedded tissue sections. Tumors with high TVD were more likely to recur after surgical treatment than tumors with low TVD suggesting that TVD measurements can be used by the clinician, in addition to histologic type and clinical stage, to predict prognosis after surgical treatment. These data also provide rationale for use of antiangiogenesis strategies for treatment of malignant mammary tumors in dogs.

Osteogenic sarcoma and cisplatin chemotherapy in dogs: 16 cases (1986-1989).

Sixteen dogs, given adjuvant cisplatin chemotherapy after amputation for osteogenic sarcoma of the appendicular skeleton, had a median survival time of 413 days. Ten dogs (62%) were alive 1 year after amputation. Dogs were given cisplatin at a dosage of 50 mg/m2 of body surface every 4 weeks for a total of 6 cisplatin treatments, or until metastatic disease was detected. Cisplatin chemotherapy was well-tolerated by most dogs, with only 1 dog developing serious gastrointestinal toxicosis, requiring hospitalization. Results of this study support other investigators' findings that when a cisplatin chemotherapy-based protocol is administered, survival times after amputation can be prolonged for dogs with osteogenic sarcoma.

Results of chemotherapy for cats with alimentary malignant lymphoma: 21 cases (1993-1997)

OBJECTIVE: To determine clinical and pathologic findings in cats with alimentary malignant lymphoma and results of treatment with a combination of prednisone, L-asparaginase, vincristine, cyclophosphamide, doxorubicin, and methotrexate. DESIGN: Retrospective study. ANIMALS: 21 cats with alimentary malignant lymphoma. PROCEDURE: Medical records were reviewed, and information on signalment, clinical history and signs, previous treatments, and results of laboratory tests, thoracic radiography, and abdominal ultrasonography were obtained. RESULTS: Test results in all cats were negative for FeLV; 3 of 19 were positive for feline immunodeficiency virus. Thirteen tumors were stage III, 7 were stage IV, and 1 was stage V. Diagnosis was confirmed on the basis of microscopic examination of histologic (n = 13) or cytologic (8) specimens. Immunophenotyping was performed on 13 tumors; 10 were T-cell and 3 were B-cell lymphomas. Overall median duration of first remission was 20 weeks. Overall median survival time was 40 weeks. The only factor significantly associated with duration of first remission was whether cats had a complete response following induction chemotherapy; duration of first remission was significantly associated with survival time. Cats tolerated treatment well; only 1 cat had a delay in the treatment schedule because of neutropenia. CLINICAL IMPLICATIONS: Use of a multidrug chemotherapeutic protocol that includes L-asparaginase and doxorubicin results in minimal adverse effects and prolonged survival times in cats with alimentary malignant lymphoma.

Rapid detection of K-ras gene mutations in canine lung cancer using single-strand conformational polymorphism analysis.

A total of 126 spontaneous lung tumors from pet dogs were examined for K-ras mutations within exon 1 and exon 2 using a non-radioisotope single-strand conformational polymorphism analysis (SSCP) detection method on PCR products. Mutations were confirmed by direct DNA sequencing. Tumors were classified as adenomas (9), bronchioloalveolar carcinomas (59), adenocarcinomas (30), adenosquamous carcinomas (16), squamous cell carcinomas (3) and anaplastic carcinomas (9). Nineteen mutations were detected in the malignant tumors: 18 occurred in exon 1 codon 12 and one in exon 2 codon 61. No mutations were present in the adenomas. The most common mutation was a G-->A transition (11/19) in the second position of codon 12. Based on this study, K-ras mutations occur in canine non-small cell lung carcinomas. The frequency and type of mutation more closely matches tumors from human non-smokers with K-ras mutations than smokers. With the application of screening techniques such as SSCP, large numbers of dog tumors can be examined to provide a large animal model for comparative studies of carcinogenesis.

Mutational analysis of a dominant oncogene (c-Ki-ras-2) and a tumor suppressor gene (p53) in hamster lung tumorigenesis.

In human lung cancers, alterations of both a dominant oncogene (ras) and a tumor suppressor gene (p53) have been identified. Polymerase chain reaction (PCR) analysis of mRNA was used to amplify the c-Ki-ras-2 and p53 genes from Syrian golden hamsters. The PCR products were confirmed by predicted-size analysis, probing with nonradioactive (biotin-labeled) oligonucleotides, and direct sequencing. Lung tumors were produced in hamsters by repeated injections of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK). Of six tumors examined, three (50%) had mutations in codon 12 of Ki-ras. Examination of the conserved regions of p53 revealed no mutations. We conclude that NNK-induced carcinogenesis in the hamster results in characteristic alterations of Ki-ras but may not necessarily involve the p53 gene.

Adenosquamous carcinoma arising in a mucinous cystadenoma of the pancreas.

BACKGROUND: Approximately 500 cystic neoplasms of the pancreas have been reported, and among these the mucinous pancreatic cystadenomas are known to have malignant potential. We report a rare case of a mucinous cystadenoma containing adenosquamous carcinoma. METHODS: We studied the histochemical and immunohistochemical staining characteristics of the tumor by staining with hematoxylin/eosin, Alcian Blue/Periodic Acid Schiff, and with immunoperoxidase-labelled antibodies against carcinoembryonic antigen, epithelial membrane antigen, low and high molecular weight cytokeratins, the proliferation antigen Ki-67, and the tumor suppressor antigen p-53. The K-ras oncogene was analyzed by direct sequencing. RESULTS: This case illustrates the usual presentation and features of this unusual tumor-a middle aged woman with abdominal pain and no history of alcohol abuse or abdominal trauma. The mucinous cystic tumor of her pancreas was composed predominantly of benign epithelium with areas of a malignant component that were identified by thorough sampling. CONCLUSION: We discuss the nomenclature of these neoplasms and suggest that continuing efforts to subclassify mucinous cystic pancreatic tumors histologically may not be necessary, since the tumors are all histologically similar and are malignant or have malignant potential, and for all, treatment should include resection.