Tumour suppressor gene p53 mutation in a case of haemangiosarcoma of a dog

Haemangiosarcomas of dogs were analysed by molecular genetic techniques. Regions of the tumour suppressor gene p53, including the well-known tumour hot spots (codons 175, 245, 248, 249, 273 and 282) were screened. A 24 bp deletion was detected in exon 5 of the gene.     

Canine tumour suppressor gene p53 mutation in a case of anaplastic carcinoma of the intestine

Tumours localised in the large bowel of dogs were subjected to molecular genetic studies. Highly conserved regions of the tumour suppressor gene p53, including typical tumour hot spots (codons 175, 245, 248, 249, 273 and 282), were analysed. A mutation CGG-->TGG (arginine-->tryptophan) was present in codon 249 in an anaplastic carcinoma in the caecum.     

Comparative studies in the promoter and exon 1 regions of tumour suppressor p53 in several mammalian species: absence of mutations in a panel of spontaneous domestic animal tumours

Tumour suppressor p53 is critical in a broad panel of tumour types in human, mouse and other mammals. Regions of the promoter and exon 1 play an important role in expression of p53. In the present study, the DNA sequences of promoter and exon 1 regions of four domestic animal species (dog, cat, horse and cattle) are determined and compared with experimental rodents (mouse, rat and hamster) and man. A broad panel of tumour types have been investigated for mutations in this regulatory area in 90 canine, 136 feline, 25 equine and 10 bovine patients. No mutation was detected in any of the tumours analysed.     

p53 protein expression in conjunctival squamous cell carcinomas of domestic animals

The expression of p53 protein was investigated in eight formalin-fixed, paraffin-embedded conjunctival squamous cell carcinomas of five horses and one cow, dog and cat each by an immunohistochemical procedure in order to evaluate protein overexpression. Anti-human p53 protein mouse monoclonal antibodies known to be cross-reactive with p53 protein of the animal species examined were used. Positive p53 nuclear immunostaining was detected in five equine, one bovine and one feline cases. Conversely, no p53 immunostaining was found in the only canine case examined. These results demonstrate a frequent p53 overexpression in conjunctival squamous cell carcinoma that could be related to UV-induced mutations of the p53 tumor suppressor gene.     

p53 expression in canine lymphoma

The tumour suppressor p53 plays a key role in DNA damage and repair. It is the most frequently altered gene in human cancers and these mutations may implicate the genesis and/or progression of tumours. Mutations of the p53 gene were also found in a number of canine cancers, although it is poorly estimated in canine lymphomas. Thus, the aim of this study was to investigate the p53 status in these types of tumours. We have shown that the expression of p53 in canine lymphomas is rare, however significantly differs between lymphomas of T- and B-cell origin.     

Detection of centrosome amplification as a surrogate marker of dysfunction in the p53 pathway –p53 gene mutation or MDM2 overexpression

In human and canine cancers, the inactivation of p53 protein as well as p53 gene mutation and MDM2 overexpression result in centrosome amplification that in turn contributes to chromosomal instability. To explore the usefulness of the detection of centrosome amplification as a surrogate marker of dysfunction in the p53 pathway, we systematically analysed centrosome amplification, p53 overexpression, p53 gene mutation and MDM2 overexpression in canine tumours. Centrosome amplification was detected in 16 of 51 (31%) naturally developing tumours in dogs. All the tumour specimens with aberrations in the p53 pathway, including p53 overexpression, p53 gene mutation or MDM2 overexpression, showed centrosome amplification, suggesting that the detection of centrosome amplification could serve as a preliminary surrogate marker of dysfunction in the p53 pathway.     

Presence of p53 mutations in feline neoplasms

A region from exon 4 to 8 of the tumour suppressor gene p53 was analysed in 60 feline tumours (30 fibrosarcomas, seven malignant histiocytomas, three lymphosarcomas, five basal cell tumours, five squamous cell carcinomas, two adenocarcinomas of tubular skin glands, one undifferentiated carcinoma of the skin, seven mammary carcinomas). Missense mutations were detected in two fibrosarcomas, one malignant fibrous histiocytoma, the undifferentiated carcinoma of the skin and one mammary carcinoma. One nonsense mutation was detected in one fibrosarcoma and one deletion/frameshift-mutation was observed in one squamous cell carcinoma.     

p53基因与肿瘤形成

肿瘤抑制基因的研究已经成为继癌基因之后肿瘤遗传学、分子生物学领域的前沿和热点,尤其是抑癌基因p53越来越被人们重视。研究表明正常的p53,又称野生型p53,在细胞损伤后的修复过程中发挥重要作用。正常p53的功能像"分子警察"一样监视着基因组DNA的完整性。在细胞发生DNA损伤时,p53蛋白能使细胞分裂终止在G1/S期,以使细胞有足够的时间修复损伤,恢复正常状态。若不能修复,野生型p53还能启动细胞的凋亡过程从而引发细胞的程序性死亡,阻止具有癌变倾向的突变细胞产生。而突变型p53基因会导致肿瘤的发生,大多数肿瘤与p53的突变有关。文章着重阐述了p53的表达与突变、p53的稳定调节及p53的转录调控等。     

Immunohistochemical expression of dogTERT in canine testicular tumours in relation to PCNA,ki67 and p53 expression.

The objective of the study was to determine the immunohistochemical expression of canine TERT in canine testicular tumours comparing two different antibodies for TERT, and to correlate them with well established markers specific to dividing cells such as PCNA and ki67, and with expression of the p53 tumour suppressor gene. The study included 36 cases of canine testicular tumours, which were categorized as 12 Sertoli Cell Tumours (SCT), 20 seminomas, 3 interstitial cell tumours and 1 mixed germ cell-sex cord stromal tumour (MT). Two antibodies for hTERT were examined; a highly specific TERT antibody, RCK-hTERT, was evaluated for the first time. Immunodetection of RCK-hTERT was observed in 31% of tumours examined (6/20 Seminomas, 4/12 SCT, 1/3 interstitial cell tumour and 0/1 mixed germ cell-sex cord stromal tumour), while the NCL-hTERT in 67% of them (15/20 Seminomas, 6/12 SCT, 3/3 interstitial cell tumour and 0/1 ΜΤ). PCNA immunoreactivity was detected in all cases. Regarding ki67, 3 SCT, 12 seminomas and all interstitial cell tumours showed clear immunoreaction. p53 immunoreactivity was detected in 6 SCT, 15 seminomas and all interstitial cell tumours. The immunohistochemical expression of both TERT antibodies are discussed and compared in order to clarify their potential usefulness in canine testicular malignancies in relation to the expression of well known cell cycle markers. Our results indicate that TERT and PCNA are useful proliferation markers but not helpful to evaluate prognosis. Instead of that ki67 and p53 could be used for predicting aggressiveness in this group of tumours     

p53 expression and apoptosis in melanomas of dogs and cats

Twenty-seven melanocytic tumours from 20 dogs and four cats were examined for p53 expression and apoptosis. They included tumours that were histologically classified as benign (BM), primary malignant (PMM) and metastatic malignant melanomas (MMM). For all cases clinical follow-up was available. p53 expression was examined immunohistochemically using different monoclonal and polyclonal antibodies. Apoptosis was detected using the TUNEL technique. The tissue sections were analysed using a quantitative image analysing system. A p53 index (p53I) and an apoptotic index (AI) were determined. p53 over-expression was found infrequently in these canine and feline melanocytic tumours. Apoptosis was observed in some of the malignant tumours. In one feline case of malignant melanoma, p53 accumulation together with apoptosis was seen in three metastases but not in the primary tumour. p53I and AI were not significantly correlated with survival. These results are similar to those reported for human cutaneous melanomas.     

Absence of p21 WAF1 and p27 Kip1 Gene Mutations in Various Feline Tumours

The coding regions of tumour suppressor and cell cycle regulatory genes p21 WAF1 and p27 Kip1 were investigated in 101 feline tumours of various types. No damaging mutations were present in the analysed areas of the genes     

Novel p53 tumour suppressor mutations in cases of spindle cell sarcoma,pleomorphic sarcoma and fibrosarcoma in cats

Twenty feline neoplasms were sequenced in the region from exons 5 to 8 for the presence of tumour suppressor gene p53 mutations. In a spindle cell sarcoma of the bladder, a missense mutation (codon 164 AAGGAG, lysineglutamic acid) in exon 5 was detected. In a pleomorphic sarcoma, a 23 bp deletion involving the splicing junction between intron 5 and exon 6 was observed. In a fibrosarcoma, a 6 bp deletion of p53 covering 2 bp of exon 7 and 4 bp of intron 7, including the splicing junction, was found. The study demonstrates three new p53 mutations in different types of sarcomas in cats.     

p53 gene mutations occurring in spontaneous benign and malignant mammary tumors of the dog

Sixty-three cases of benign and malignant canine mammary tumors were analyzed to define the alteration of exons 5-8 for the p53 tumor suppressor gene using polymerase chain reaction direct sequence analysis with paraffin-embedded tissues. Four missense mutations were found in 38 benign mammary tumors (11%), and five missense (one tumor had two missense mutations) and one nonsense mutations were found in 25 mammary carcinomas (20%). These data suggest that the p53 gene alterations might be initiated at an early stage of canine mammary carcinogenesis and p53 mutations might be associated with malignancy. However, there was no evidence of any relationship between the p53 alterations and the histologic types of tumors or breeds of dogs.     

Search for physical interaction between BICP0 of bovine herpesvirus-1 and p53 tumor suppressor protein

The immediate-early (IE) protein BICP0 of bovine herpesvirus-1 (BHV-1) may have other functions besides transactivation of viral promoters. Recently, we observed that BICP0, delivered to cultured cells by a helpervirus-free amplicon system, forms spherical or doughnut-like structures in which the tumor suppressor protein p53 is sequestered. The objective was to determine whether BICP0 and p53 interact physically, we used both yeast and mammalian two-hybrid systems. As a bait plasmid, pVA3 which encodes a hybrid protein consisting of the Gal4 DNA binding domain fused to murine p53 was used. The BICP0 gene or its truncated versions were inserted into the prey plasmid pGAD424. Bait and prey plasmids were cotransformed into yeast strain Y153, which has LacZ and HIS3 reporter genes under the control of Gal4 upstream activating sequence. After 4-6 days, colonies were stained for beta-galactosidase activity. In the mammalian two-hybrid system, pM-53 was used as a bait where truncated p53 fused to Gal4 DNA binding domain is expressed. The BICP0 gene was cloned into prey plasmid pVP16. The interaction between p53 and SV40 T-antigen was evaluated as a positive control in both systems. Neither full-length BICP0 nor its truncated derivatives induced beta-galactosidase activity in yeast whereas the positive control turned blue under the same conditions. The mammalian two-hybrid system, in which chloramphenicol acetyltransferase (CAT) activity was used as a reporter, also failed to show an interaction between these two proteins. Co-localization of p53 with BICP0 in spherical structures is unlikely to result from a direct physical interaction between these two proteins. Mediation by additional cellular proteins may be required.     

Immunohistochemical detection of tumor suppressor gene p53 protein in feline injection site-associated sarcomas

Sarcomas associated with injection sites are a rare but important problem in cats. Immunohistochemical detection of p53 protein may correlate to mutation of the p53 tumor suppressor gene, a gene known to be important in oncogenesis. The expression of nuclear p53 protein in 40 feline injection site-assocated sarcomas was examined by immunohistochemical staining. In 42.5% (17/40), tumor cell nuclei were stained darkly; in 20% (8/40), tumor cell nuclei were stained palely; and in 37.5% (15/40), tumor cell nuclei were unstained. Immunohistochemical detection of p53 protein in a proportion of injection site-associated sarcomas suggests that mutation of the p53 gene may play a role in the pathogenesis of these tumors.     

Radiosensitivity of canine osteosarcoma cells transfected with wild‐type p53 in vitro*

The p53 gene is one of the important tumour suppressor genes that are involved with the cell survival signal pathway. One of the major functions of the p53 protein is to organize cell cycle regulation and induction of apoptosis for cellular genetic stability. It has been documented that more than 50% of all human cancers include a p53 mutation. We evaluated the difference in radiosensitivity between upregulating the expression of canine wild‐type p53 (cp53) in cultured osteosarcoma (D17) cells and naive D17 cells in vitro. We found that upregulating transfected cp53 D17 cells increased their radiation sensitivity in vitro, and there was a significant decrease (P < 0.009) in survival between cp53‐transfected D17 cells and naive D17 cells. In this experiment, a p53 enhancement ratio (p53ER) reached approximately 3.0 at high doses. The transfected cp53 D17 cells were significantly more radiosensitive at all doses evaluated than naive D17 cells, except at 1 Gy where too few data points were available. The p53ER increased rapidly at doses less than 4 Gy, achieving a maximum of about 3.0 for doses of 4 Gy and above. This study shows the enhanced radiosensitivity of the transfected p53 at clinically relevant doses.     

Canine Tumour Suppressor Gene p53 - Mutation in a Case of Adenoma of Circumanal Glands

Highly conserved regions of the tumour suppressor gene p53, including the typical human tumour hot spots (codons 175, 245, 248, 249, 273 and 282), were investigated in various canine neoplasms. A mutation CGG TGG (arginine tryptophan) was detected in codon 249 in an adenoma of the circumanal gland.