J Korean Assoc Oral Maxillofac Surg.  2001 Oct;27(5):373-384.

Study On Mutation Of P53 And Expression Of Mdm-2 In Dmba Induced Carcinoma Of Hamster Buccal Pouch

• Park YS
• Kim KW
• Lee JH
• Kim CJ

Abstract

Cellular proliferation is an intricately regulated process mediated by the coordinated interactions of critical growth control genes.Two of these factors in mammalian cells are the p53 and mdm-2 genes. A protein product of the mem-2 oncogene has been recentlyshown to associate with the protein encoded by the tumor suppressor gene p53.The p53 tumor suppressor protein is stabilized in response to DNA damage and other stress signals and causes the cell to undergo growth arrest or apoptosis, thus preventing the establishment of mutations in future cellular generations. Mutation or loss of p53 is a very common event in tumor progression. It occurs in about 50% of all tumors analysed including of colon, lung, breast and liver.The cellular mdm-2 gene, which has potential transforming activity that can be activated by overexpression, is amplified in a significant percentage of human sarcoma and in other mammalian tumors. Proteins encoded by the mdm-2 gene are able to bind to the p53 protein and, when overexpressed, can inhibit p53's transcriptional activation function, thus mdm-2 can act as a negative regulator of p53 function. Experimental study was performed to observe the relationship between p53 gene mutation and mdm-2 protein expression and apply the results to the clinical activity. 36 golden syrian hamster each weighing 60.80g were used and painted with 0.5% DMBA by 3 times weekly on the right buccalcheek(experimental side) for 6, 8, 10, 12, 14 and 16 weeks. Left buccal cheek(control side) was treated with mineral oil as the same manner to the right side. The hamsters were sacrificed on the 6, 8, 10, 12, 14 & 16 weeks.Normal and tumor tissues from paraffin block were examined for histology and immunohistochemistry observation, and were completely dissected by microdissection and DNA from both tissue were isolated by proteins K/phenol/chloroform extraction. Segments of the hamster p53 exons 5, 6, 7 and 8 were amplified by PCR using the oligonucleotide primers, and then confirmational change wasobserved by SSCP respectively. The results were as follows : 1. Dysplasia at 6 weeks, carcinoma in situ at 8 weeks and invasive carcinoma from 10 weeks could be observed in experimental groups. 2. p53 mutations were detected in 10 of the 36(28%) and the exons 6(6 of the 10 : 60%) was the most hot spot area among the highy conserved region(exons 5, 6, 7 & 8). 3. Immunohistochemical study confirmed 22 of the 36(61%) of p53 expression involving 10 of p53 mutations. 4. mdm-2 expression of was showed in 3 of the 36(8%) involving 1 of the 22 of p53 expression and 2 of the 14 of p53 non-expression. From the above results, mutation of p53 gene or expression of p53 protein may have the influence of the DMBA induced carcinoma of hamster buccal pouch but the expression of mdm-2 protein may not have relationship with tumorigenesis.

MeSH Terms

9,10-Dimethyl-1,2-benzanthracene*
Animals
Apoptosis
Breast
Carcinogenesis
Carcinoma in Situ
Cell Proliferation
Colon
Cricetinae*
DNA
DNA Damage
DNA Primers
Exons
Family Characteristics
Genes, p53
Genes, Tumor Suppressor
Humans
Immunohistochemistry
Lung
Microdissection
Mineral Oil
Oncogenes
Paint
Paraffin
Polymerase Chain Reaction
Polymorphism, Single-Stranded Conformational
Proto-Oncogene Proteins c-mdm2
Sarcoma
Transcriptional Activation
Tumor Suppressor Protein p53
9,10-Dimethyl-1,2-benzanthracene
DNA
DNA Primers
Mineral Oil
Paraffin
Proto-Oncogene Proteins c-mdm2
Tumor Suppressor Protein p53