Comparative cytogenetic studies of benign, borderline, and malignant epithelial ovarian tumors

Comparative study of primary and recurrent ovarian serous carcinomas: comparative genomic hybridization analysis with a potential application for prognosis

OBJECTIVES

The purpose of this study is to comparatively characterize genomic imbalances in primary and recurrent ovarian serous carcinomas and to identify genomic alterations that may be used as a marker for prognosis.

METHODS

Twenty ovarian serous carcinomas were studied by comparative genomic hybridization (CGH).

RESULTS

Genomic alterations were found in all of the tumors. The most common regions involving gain of DNA copy numbers are 1q41q44, 8q22q24, 19p12q13.1, 20q12q13, 3q26q29, 12p12p13, 2p22p25, 7p14p21, 5p15.2p15.3, and 17q22q25. The most common regions with loss of DNA copy numbers are Xp11.2q13, 4q31q35, Xp21p22.3, 18q22q23, 13q22q31, 9p22p24, and 16q22q24. High-level gains were detected at chromosomal regions of 1q41q44, 2p22p25, 3q26q29, and 19p12q13.1. Comparative analysis of primary and recurrent tumors showed that gains of 2p22p25, 19p12q13.1, and 20q12q13 and loss of 5q14q22 were more common in the recurrent high-grade tumors. About 85% of the tumors showed increases in DNA copy numbers in the regions (2p and 8q) harboring the myc family gene. Patients with tumor containing fewer than seven chromosomal aberrations showed longer survival time.

CONCLUSION

The myc oncogene family may play a role in the pathogenesis of ovarian serous carcinomas. Our study suggests that tumors with gains of 2p22p25, 19p12q13.1, and 20q12q13 and loss of 5q14q22 may be at high risk for recurrence. Furthermore, the patients' survival time inversely correlates with the numbers of chromosomal alterations found in their tumors. CGH analysis may have a clinical application in predicting prognosis and risk of recurrence in patients with ovarian serous carcinomas.

Genomic imbalances in ovarian borderline serous and mucinous tumors

We analyzed 25 ovarian borderline tumors (13 serous and 12 mucinous tumors) by comparative genomic hybridization (CGH). Genomic imbalance was detected in 85% of serous tumors and 75% of mucinous tumors. Different patterns of genomic alterations were identified in serous and mucinous tumors. Gain of the X chromosome was common in both serous (30%) and mucinous (42%) tumors. However, gain of chromosome 8 was detected exclusively in 38% of serous and mixed sero-mucinous tumors, but not in any pure mucinous tumors. According to the present and previous studies, gain of chromosome 8 is the most common abnormality in borderline serous tumors. Gain of the same chromosome is also common in high grade and advanced stage serous carcinomas, but uncommon in early stage serous carcinomas. In addition gain of chromosome X is common in borderline serous and mucinous tumors, while loss of chromosome X is predominant in invasive carcinomas. These findings do not support the multi-step progression theory from borderline tumor to high-grade, advanced stage carcinoma, but indicate that the borderline ovarian tumor is a distinct entity. Genes in chromosome 8 may be critical for the development and the differentiation of borderline serous tumors.

Allelic imbalance is not restricted to numerically abnormal chromosomes in epithelial ovarian tumours

In this study, 23 low malignant potential (LMP) and 27 invasive epithelial ovarian tumours have been examined by microdissection and microsatellite polymerase chain reaction (PCR) for allelic imbalance (AI) at loci on the p and q arms of chromosomes 1, 11, 17, and X, and the data have been compared with interphase cytogenetics for numerical abnormalities (aneusomy) of these chromosomes. AI was uncommon in LMP tumours (5 of 23 at 9 of 146 informative loci) but was significantly more common (p<0.001) in invasive carcinomas (21 of 27 at 47 of 168 informative loci). This difference remained when LMP tumours were compared specifically with stage I carcinomas (p<0.001). A greater number of loci were involved in AI amongst serous than amongst mucinous carcinomas (p=0.015). AI was present at significantly more loci in carcinomas showing aneusomy by interphase cytogenetics than in those showing no numerical chromosome abnormalities (p<0.001). However, amongst the carcinomas showing aneusomy, AI was as frequent at loci on chromosomes with no numerical abnormality as at those with the numerical changes. These data demonstrate that aneusomy and AI are interrelated phenomena but that AI does not occur simply as a consequence of numerical chromosome changes.