Molecular cytogenetic analysis of human ovarian carcinoma: Identification and characterization of amplified DNA sequences

Abstract

DNA sequence amplification, a mechanism by which genes achieve increased dosage and expression, is known to contribute to the multistep process of carcinogenesis. Cytogenetic analyses of human tumor cells, including ovarian malignancies, frequently show cytological evidence of DNA amplification in the form of double minutes (dmin) and homogeneously staining regions (hsr). In this project, DNA sequence amplification in ovarian carcinoma has been examined by several methods. The combined techniques of chromosome microdissection and fluorescence in situ hybridization have been used to identify the chromosomal origin and composition of seven cases with hsr and one case with dmin. Fourteen specific chromosome band regions were identified as amplified including 2p24, 3q36, 11q13, 12p12 and 19q13. Detection of 2p24 amplification in one ovarian tumor led to the previously unreported identification of N-MYC amplification in multiple cases of ovarian carcinoma. Microdissection mediated cDNA capture (MMcC), a recently developed technique based on in situ hybridization of cDNA to tumor chromosomes with subsequent microdissection and recovery of selected cDNA sequences, was used to isolate transcripts from dmin in an ovarian tumor shown to contain 2p24 and 3q26 amplification. The dmin-selected cDNA library obtained by MMcC revealed that a third chromosomal region, 1q12, was coamplified with 2p24 and 3q26 in the same dmin population. Chromosomal band 3q26 has previously been shown to be gained in 50% of ovarian carcinoma analyzed as well as tumors of the cervix, endometrium, lung and mantle cell lymphoma. Studies of the dmin-selected cDNA identified several groups of amplified cDNA; one group mapped to 1q12, one group represented N-MYC, and 5 groups mapped to the 3q26 region. Characterization of several cDNA has been carried out. The 5 groups of amplified cDNA from 3q26 have provided reagents, including a large insert genomic clone, which can be used to explore the role of 3q26 in ovarian carcinoma as well as other malignancies. This project has identified amplified chromosomal regions containing previously recognized amplified genes as well as novel chromosomal regions and genes which may be of biological relevance in ovarian carcinogenesis. Further characterization of the identified chromosomal regions and expressed transcripts identified by this thesis project may provide insight into the role of DNA sequence amplification in the development and progression of ovarian carcinoma.