Translocation breakpoints in FHIT and FRA3B in both homologs of chromosome 3 in an esophageal adenocarcinoma.

Common fragile sites have been proposed to play a mechanistic role in chromosome translocations and other rearrangements in cancer cells in vivo based on their behavior in vitro and their co-localization with cancer translocation breakpoints. This hypothesis has been the subject of controversy, because associations have been made at the chromosomal level and because of the large number of both fragile sites and cancer chromosome breakpoints. Tests of this hypothesis at the molecular level are now possible with the cloning of common fragile site loci and the use of fragile site clones in the analysis of rearranged chromosomes. FRA3B, the most frequently seen common fragile site, lies within the large FHIT gene. It is now well established that this region is the site of frequent, large intragenic deletions and aberrant transcripts in a number of tumors and tumor cell lines. In contrast, only one tumor-associated translocation involving the FHIT gene has been reported. We have found translocations in both homologs of chromosome 3 in an early-passage esophageal adenocarcinoma cell line. This cell line showed no normal FHIT transcripts by reverse transcription polymerase chain reaction. Subsequent chromosome analysis showed translocations of the short arms of both homologs of chromosome 3: t(3;16) and t(3;4). The breakpoints of both translocations were shown by fluorescence in situ hybridization and polymerase chain reaction to be in the FHIT gene, at or near the center of the fragile site region. Using rapid amplification of cDNA ends with FHIT primers, a noncoding chimeric transcript resulting from t(3;16) was identified. These data provide direct support for the hypothesis that FRA3B, and likely other common fragile sites, may be "hot spots" for translocations in certain cancers, as they are for deletions, and that such translocations have the potential to form abnormal chimeric transcripts. In addition, the results suggest selection for loss of a functional FHIT gene by the translocation events.

Distinct areas of allelic loss on chromosomal regions 10p and 10q in human prostate cancer.

Utilizing tissue microdissection and PCR techniques, we have examined 35 prostate tumors paired with normal tissues from the same patients for allelic loss at 24 polymorphic loci spanning chromosome 10. Twenty-five tumors (71%) were deleted for at least one chromosome 10 locus. Of the total 35 tumors, 6 (17%) were deleted for 10p loci only, 5 (14%) for 10q loci only, and 14 (40%) were deleted for both 10p and 10q loci. The common region of deletion on 10p included loci D10S211-D10S89-D10S111. Fluorescence in situ hybridization of yeast artificial chromosome probes encompassing these loci demonstrated that the 10p region of deletion maps to 10p11.2. Losses involving 10p loci alone were most common in localized (5/14, 36%) and least common in metastatic (0/8) tumors. The common region of deletion on 10q included loci D10S219-D10S215, consistent with the major region of deletion recently defined for prostate tumors on 10q. Losses involving 10q loci alone were lowest in localized and locally invasive tumors (1/14 and 2/12, respectively) and highest in tumors metastatic to regional lymph nodes (2/8). These results suggest that 10p losses may define less invasive tumors, whereas 10q losses may play a role in the progression to more advanced tumor states in the prostate. Furthermore, this is the first report of allelic loss of a defined region on 10p potentially harboring tumor suppressor gene loci in human prostate cancer.

Chromosome breakpoint at 17q11.2 and insertion of DNA from three different chromosomes in a glioblastoma with exceptional glial fibrillary acidic protein expression.

A glioblastoma that retained glial fibrillary acidic protein (GFAP) in culture has a break in the long arm of chromosome 17 at band 17q11.2. DNA inserted at this breakpoint came from chromosome bands 3p21, 3q23, 16q11.2, and 22q11.2. These chromosome fragments were inserted in band 17q11.2 proximal to the neurofibromatosis-1 (NF-1) gene and neu (HER2; erbB2) oncogene loci. The glioblastoma also contained a reciprocal translocation between 16p12 and 20p12. These structural abnormalities, previously undescribed in gliomas, were demonstrated by high-resolution chromosome banding, microdissection, and fluorescence in situ hybridization (FISH). Numerical changes typical of glioblastoma were present: gain of chromosome 7 and losses of chromosomes 10, 13, and 22. The complex chromosome origin of DNA inserted in this glioma chromosome is described. The association of two infrequent events in this single glioblastoma line, this complex insertion and retention of GFAP expression, is not likely to be a chance occurrence. It raises the possibility of an association between the two events.

Coverage of chromosome 6 by chromosome microdissection: generation of 14 subregion-specific probes.

Human chromosome 6 has been subdivided by chromosome microdissection into 14 unique regions. Following microdissection, polymerase chain reaction (PCR) amplification of dissected DNA was performed using a universal primer to generate subregion-specific probes that provided complete coverage of chromosome 6. All 16 microdissections have been regionally assigned along chromosome 6 by fluorescence in situ hybridization (FISH) using biotin-labeled dissected DNA hybridized to G-banded normal metaphase chromosomes. These probes can be used as region-specific paints to generate unique "bar codes" and for analysis of chromosome alterations involving chromosome 6 that are unidentifiable by conventional banding analysis.

Use of fluorescence in situ hybridization (FISH) to study chromosomal damage induced by radiation and bromodeoxyuridine in human colon cancer cells.

PURPOSE: Although the thymidine analog radiation sensitizer bromodeoxyuridine (BrdUrd) increases radiation-induced chromosomal aberrations, it is not known whether these aberrations are uniformly distributed among chromosomes. Using fluorescence in situ hybridization, we carried out a study to test the hypothesis that BrdUrd-induced radiosensitization may be mediated by nonuniform chromosomal damage. METHODS AND MATERIALS: Log phase HT29 human colon cancer cells were exposed to 10 microM BrdUrd (or media alone) for one cell cycle, and the G1 cells were separated by centrifugal elutriation. Half of the control and BrdUrd samples were irradiated with 8 Gy. Cells were then incubated for 24-28 h, and metaphase spreads were prepared. Fluorescence in situ hybridization was performed using paint probes for chromosomes 1 and 4. RESULTS: We found that radiation induced 0.20 aberrations per chromosome in chromosome 4. Based on the ratio of the relative lengths of chromosome 1-4 (1.34), it was predicted that chromosome 1 would have approximately 0.26 aberrations per chromosome. However, we observed 0.39 aberrations per chromosome 1, which was significantly greater than the predicted (p < 0.001 by chi-square). Incubation with BrdUrd prior to irradiation significantly increased the aberrations found in chromosome 1 (by a factor of 1.4) and chromosome 4 (by a factor of 1.9) compared to radiation alone (p < 0.001) for both chromosome 1 and 4). CONCLUSION: This study demonstrates that individual chromosomes in human colon cancer cells show significantly different rates of aberration after irradiation. Furthermore, the BrdUrd-mediated increase in radiation-induced chromosomal aberrations may not be uniform among chromosomes.

Examination of clonal variants from human malignant melanoma studied by chromosome banding analysis.

Multiple metastatic melanoma lesions from three patients were cytogenetically characterized in order to assess the degree of intra-patient karyotypic heterogeneity. A total of 20 specimens were analysed: 12 samples from patient No. 1, five samples from patient No. 2, and three samples from patient No. 3. Sufficient mitoses were obtained to perform detailed analysis in 19/20 specimens following short-term culture. The modal chromosome number of all three cases was near-diploid, with all samples demonstrating multiple structural abnormalities. Abnormalities shared by all three patients were alterations of chromosomes 1 and 8. Other structural abnormalities common to two of the three patients involved chromosomes 6, 7, 9 and 10. Minor intra-tumour karyotypic variation was detected in all three cases. However, the majority of clonal alterations were retained in all metastatic lesions, clearly indicating the karyotypically stable and clonal nature of this neoplasm.

Chromosome mosaicism and maternal cell contamination in chorionic villi.

While chorionic villus sampling allows both early and rapid prenatal diagnosis of chromosome disorders, the accuracy of this technique has not been fully established. Maternal cell contamination and pseudomosaicism represent two major sources of diagnostic error. Combined use of both direct chromosome preparations and villus cultures is important in overcoming these problems. Direct preparations of villus tissue allow recognition of maternal cell contamination of villus cultures. Conversely, villus cultures yield higher resolution chromosomes and may be helpful in differentiating between true versus pseudomosaicism when two or more cell lines are identified in direct chromosome preparations. Preliminary data suggest that analysis of direct preparations from multiple individually processed villus fragments may also be of value in this regard. Until more experience is gained, mid-trimester amniocentesis should be offered to CVS patients when mosaicism is encountered.

High resolution R banding in amniotic fluid cells using the BrdU-Hoechst 33258-Giemsa (RBG) technique.

While standard Giemsa banding is generally adequate for amniotic fluid chromosome analysis, small deletions, duplications, or translocation breakpoints involving G-negative bands may be difficult to appreciate. We report a method for producing high resolution R banding in human amniotic fluid cultures using the BrdU-Hoechst 33258-Giemsa (RBG) technique. RBG banding can be useful in confirming and precisely defining structural abnormalities in amniotic fluid cultures.

Serological diagnosis of California (La Crosse) encephalitis by immunofluorescence.

A method of indirect immunofluorescence was developed and examined retrospectively as a serological test for the laboratory diagnosis of California encephalitis (CE). LaCrosse virus immunofluorescence immunoglobulin (Ig) G and IgM studies were done on paired sera from 50 patients with acute central nervous system infections. CE had been documented in 25 patients by hemagglutination inhibition, neutralizing, complement fixing, and/or precipitin tests. Five (20%) of the acute and 16 (64%) of the convalescent sera from CE patients had La Crosse IgM antibodies. Seven (28%) of the acute and all of the convalescent CE specimens had La Crosse IgG antibodies. Titers ranged from less than 4 to 256. IgG antibodies were present in all 11 sera collected 1 to 2 years after CE, but IgM antibodies were absent. The 25 serum pairs from patients who did not have CE were negative for IgM and IgG antibodies. This study indicated that La Crosse immunofluorescence antibody tests were as sensitive and specific for CE as conventional hemagglutination-inhibition tests, and would detect at least 20% of patients during their acute illness.