A subset of gestational trophoblastic disease characterized by abnormal chromosome 8 copy number detected by fluorescence in situ hybridization

Fluorescent in situ hybridization study of c-myc oncogene copy number in prostate cancer

We previously conducted a study of 88 cases of prostate cancer in an attempt to identify potential prognostic biomarkers that can distinguish aggressive cases that must be treated immediately. Prostate cancer is a serious disease affecting men worldwide and compromises the quality of life of its patients. Biomarkers studied included chromosome 7 trisomy, chromosome 8 trisomy, and HER-2/neu oncogene amplification. These biomarkers were initially studied because trisomy 8 and oncogene amplification of the HER-2/neu gene have been reported in many other cancers, including those studied in this laboratory. In view of the fact that HER-2/neu amplification was not found to play a prominent role in the group of prostate cancer specimens that we studied, an exploration of other biomarkers was felt to be warranted. Thus, we began a pilot study of c-myc oncogene copy number in prostate cancer using the same protocol for fluorescent in situ hybridization and a direct-labeled SpectrumOrange LSI c-myc probe (Vysis, Inc., Downers Grove, IL) on formalin-fixed, paraffin-embedded tissue. From a total of 36 cases of prostate cancers successfully analyzed, we found 11 (31%) tumors exhibiting 3 or more positive signals for c-myc in 15% or more of the cells. Of these, only 7 tumors (19% of the total cases studied) had >/=3 signals in 20% or more of the cells. No case had >/=3 signals in 25% or more of the cells. Compared to other molecular probes tested, the c-myc signals were more faint and the quality of the preparation was less optimal than other tumor specimens that we previously studied. Based on the information available thus far, we conclude that an increased copy number in c-myc oncogene copy number was not a prominent finding in our cohort of prostate cancer patients.

Comparative genomic hybridization studies in hydatidiform moles and choriocarcinoma: amplification of 7q21-q31 and loss of 8p12-p21 in choriocarcinoma

Comparative genomic hybridization (CGH) was utilized to investigate genetic changes from archived cases of choriocarcinoma (n = 12) and hydatidiform moles (n = 7). Test DNA was extracted from paraffin-embedded tissues, amplified using total universal PCR, and co-hybridized with control DNA to normal metaphases. Comparative genomic hybridization findings showed chromosomal imbalances in 9 of 12 cases of choriocarcinoma. By contrast, all hydatidiform moles showed normal CGH profiles. Consistent findings in choriocarcinoma included deletion at 8p (5 cases) and amplification at 7q (4 cases). A tumor suppressor gene (e.g., N33) at 8p and/or a growth regulator at 7q could play a role in the initiation of choriocarcinoma and its progression. This is the first study showing specific alterations in choriocarcinomas by CGH, and illustrates the utility of this technique in elucidating genetic changes in gynecological tumors.

Assessment of chromosomal trisomies in prostate cancer using fluorescent in situ hybridization

In a previous study, we observed a low frequency of HER-2/neu oncogene amplification in prostate cancer using fluorescent in situ hybridization (FISH). In our continued effort to identify prognostic biomarkers in prostate cancer, we analyzed 74 cases of prostate cancer to assess the presence of chromosomal trisomies in this cohort of patients. Previous results from this laboratory have implicated a role of chromosomal trisomies in various cancers. FISH using a chromosome 7 and a chromosome 8 centromere probe was utilized to study abnormal chromosome copy numbers together with data from a chromosome 17 control. The frequency of trisomy 7 was found to be 58.1% (43 of 74 informative cases), while the frequency of trisomy 8 was found to be 9.5% (7 of 74 informative cases). The frequency of cells showing chromosome 17 trisomy was 18.5% (15 of 81 cases successfully studied). While chromosome 8 trisomy did not seem to play as significant a role here as in other cancers that we studied, the results of chromosome 7 trisomy are consistent with those reported in the literature. Further exploration of selected trisomies as biomarkers in prostate cancer using a larger study sample size is warranted to establish their clinical utilities.

Fluorescence in situ hybridization study of HER-2/neu oncogene amplification in prostate cancer

Prostate cancer is a serious disease affecting men worldwide and treatment compromises the quality of life of prostate cancer patients. We conducted a study of 88 cases of prostate cancer in an attempt to identify prognostic biomarkers that can distinguish aggressive cases that must be treated immediately. HER-2/neu oncogene amplification was initially studied because amplification of this gene has been reported in many other cancers, including those studied in this laboratory. Fluorescence in situ hybridization (FISH) using a HER-2/neu gene probe with a chromosome 17 centromere control probe was performed on formalin-fixed, paraffin-embedded tissues. Of a total of 86 cases successfully analyzed, only 8 (9.3%) were found to be amplified. This frequency was lower than the frequency of amplification found in other cancers studied. Furthermore, no case was found where the level of amplification can be considered high. Only one case was found to have moderate amplification. The rest of the positive cases can all be classified as low amplification. Thus, while we have demonstrated that FISH is a sensitive technique for detecting oncogene amplification, the frequency and level of HER-2/neu amplification detected in prostate cancer seem to be lower than those in most cancers that we studied. In view of the fact that HER-2/neu amplification does not seem to play as significant a role, exploration of other biomarkers in prostate cancer is warranted.

c-myc and chromosome 8 centromere studies of ovarian cancer by interphase FISH

Forty tumor specimens from patients with ovarian cancer were studied for amplification of the c-myc oncogene relative to chromosome 8 centromere number using dual-color FISH. Interphase cytogenetic analysis showed amplification of the c-myc oncogene in 40% (16/40) of tumors using the standard oncogene:centromere ratio method of analysis. Eleven of these showed moderate amplification of c-myc, and 5 samples showed high amplification. Eight of the sixteen (50%) amplified tumors were polysomic centromere 8 as were 14 of the 24 (58%) non-amplified tumors. In previously reported work with these samples, the oncogene HER-2/neu, the chromosome 17 centromere, and the tumor suppressor gene p53 had been studied. When using the standard oncogene:centromere ratio criteria, 5 samples had amplification of both the c-myc and the HER-2/neu oncogenes, 5 samples had HER-2/neu amplification but not c-myc, 11 samples had c-myc amplification but not HER-2/neu, and 19 samples had neither oncogene amplified. The p53 gene was found to be deleted in 22.5% (9/40) of samples. The loss of the p53 gene did not appear to have any clinical correlation. The presence of an extra centromere 8 also did not appear to have any clinical correlation. The Kaplan-Meier survival curve for those patients who have c-myc amplification, while not statistically significant, appears to show a trend toward poorer survival. The survival curve for patients whose tumors have HER-2/neu amplification shows no clinical significance. It is of great interest, however, that the Kaplan-Meier plot of survival for patients whose tumors have amplification of both c-myc and HER-2/neu shows a significant difference (P = 0.047). The median survival times of the doubly amplified patient group and the non-doubly amplified groups were 12 and 43 months, respectively. This is the first study of the oncogene c-myc using FISH. The results suggest that the amplification of c-myc may indicate a poorer patient survival and that the amplification of both c-myc and HER-2/neu in combination may be a better prognostic indicator of poor patient survival.