Amplification of the Cyclin A Gene in Canine and Feline Mammary Tumors.

Abstract

ABSTRACT. DNAs from 33 canine mammary tumors and 8 feline mammary carcinomas were examined by Southern blot analysis to clarify genomic abnormalities of the cyclin A gene. Amplification of cyclin A was detected in 27.3% (9/33) of canine mammary tumors and 87.5% (7/8) of feline mammary carcinomas. It was suggested that amplification of cyclin A do not correlate directly with the tumorigenesis of canine mammary tumors, because there was no significant difference of incidence of cyclin A amplification between the benign and malignant tumors. In feline mammary carcinomas, the high frequency of cyclin A amplification raised the possibility that the amplification lead to the protein overexpression and play an important role in the tumorigenesis.KEY WORDS: amplification, cyclin A, mammary tumor.J. Vet. Med. Sci. 62(7): 783-787, 2000 Cyclins are prime cell cycle regulators that are central to the control of major checkpoints in eukaryotic cells. Cyclins are categorized into three types: A-type, B-type and G1 cyclins (C-, D-, and E-types), and are activated by forming a complex with cyclin dependent kinases (cdk) at various stages of the cell cycle. The involvement of several cyclins in human cancer has been recognized over the last several years [1-13, 15, 17-21].Cyclin A, a protein of 60 kDa, binds independently to cdk2 in S to G2 phase, and cdk2/cdc2 in G2 to M phase, leading to enzyme activation. Cyclin A is detectable in S phase, and increases during cell cycle progression to G2 phase. Cyclin A is overexpressed in some hepatocellular carcinomas because it lacks a cyclin destruction box due to genomic insertion by the hepatitis B virus [3]. Recently, cyclin A alterations have also been identified in several tumors including squamous cell carcinomas of the lung [6,[19][20][21], oral cavity [11], esophagus [7] and uterine cervix [17].We recently found that overexpression of cyclin A protein occurs frequently in canine malignant mammary tumors and feline mammary carcinomas. However, molecular analysis of cyclin A remains to be done. Therefore, we examined DNAs from canine and feline mammary tumors for amplification of the cyclin A gene using Southern blot analysis.The samples of 33 canine mammary tumors and 8 feline mammary carcinomas were collected during a 3-year period (1996)(1997)(1998) at the Department of Veterinary Pathology, Miyazaki University, Japan. For histopathology, the samples were fixed in 10% formalin, and paraffin sections were prepared and stained with hematoxylin and eosin (HE). The histological typing of the tumors is listed in Tables 1 and 3. Immunohistochemistry was performed by using EnvisionPolymer reagent (Dako Japan, Kyoto, Japan). The primary antibodies used were a rabbit polyclonal antibody against human cyclin A, a recombinant protein corresponding to amino acids 1-432 representing full-length cyclin A of human origin (H-432, Santa Cruz Biotech, U.S.A.). The chromogenic reaction was carried out with diaminobenzidine (Sigma, St. Louis, U.S.A.) and counterstained with Mayer's hematoxylin....

Immunohistochemical Analysis of Cyclins in Canine Normal Testes and Testicular Tumors.

“…There is a similar report concerning cytoplasmic staining of cyclin A in human renal cell cancers [1]. In addition, we also reported previously that cytoplasmic staining of cyclin A was observed in canine squamous cell carcinomas [10]. However, it is unclear the reason why cyclin A was expressed in the cytoplasm of their tumors.…”

Inositol 1,4,5-Trisphosphate Receptor Phosphorylation in Breast Cancer

“…In addition, the amplifi cation of CyA gene has been reported in canine and feline mammary tumors [22] . Overexpression of CyA has been shown to be highly associated with early relapse and decreased survival in patients with primary breast carcinoma [3] .…”

Feline STK gene expression in mammary carcinomas

“…In particular, the lack of estrogen dependency in most tumours (De las Mulas et al, 2000) may indicate that FMC is a suitable animal model for human hormonal-unresponsive breast cancer. The ®nding of over-expression and ampli®cation of cyclin A (Murakami et al, 2000a) and p53 nuclear accumulation (Murakami et al, 2000b) suggests also a similar tumorigenesis.Over-expression of tyrosine kinase oncogenes has been reported in many carcinomas (for a review see Kolibaba and Druker, 1997). In vitro and in vivo studies suggested that among these receptors, those of the MET family might be speci®cally involved in the activation of the tyrosine kinase cascade that stimulates invasive properties of carcinoma cells.…”

“…In particular, the lack of estrogen dependency in most tumours (De las Mulas et al, 2000) may indicate that FMC is a suitable animal model for human hormonal-unresponsive breast cancer. The ®nding of over-expression and ampli®cation of cyclin A (Murakami et al, 2000a) and p53 nuclear accumulation (Murakami et al, 2000b) suggests also a similar tumorigenesis.…”