Marta Bernués

Detection of chromosomal imbalances in papillary bladder tumors by comparative genomic hybridization

OBJECTIVES To identify those genetic alterations that are associated with bladder cancer invasion and progression. METHODS A total of 30 specimens of transitional cell carcinoma of the bladder were analyzed by comparative genomic hybridization. The results were compared and summarized with previously reported studies. RESULTS The most frequent chromosome changes detected in our series of tumors were losses in 9q, 9p, 8p, and 11p and gains in 8q, 1q, 20q, and 11q. Three regions of deletion on chromosome 9 were delineated, at 9p21-p22, 9q13-q22, and 9q31-q34. Gains in 1q and losses on 11p were significantly more frequent in pT1G2 tumors than in superficial (pTa) ones. In our study, the most striking differences were seen between pT1G3 and pT1G2 tumors. Gains on 10p and 6p and losses at 5q, 6q, and 18q were significantly more frequent in the former. CONCLUSIONS A summary of our results and those available from published reports suggest that several groups of chromosomal imbalances may be associated with specific steps along bladder cancer progression. These genetic changes assume two different patterns: those that are shared, but are more intensive in one stage than in the other, and those such as a gain on 3p that are unique to invasive tumors.

Analysis of kidney tumors by comparative genomic hybridization and conventional cytogenetics

Comparative genomic hybridization (CGH) and conventional cytogenetic karyotyping were used to screen for losses and gains of DNA sequences along chromosomes in ten renal tumors (RCC) of different histologic types (clear-cell RCC, papillary RCC, and one oncocytoma). Loss of 3p was the most common change in clear-cell RCC. All papillary tumors, either adenomas or carcinomas revealed gains of chromosomes 7 and 17q without limitation to size and grade. Homozygotic loss of the pseudoautosomal Xp or Yp region was detected in three RCC tumors. A dicentric (Y;14) was present as the sole chromosome abnormality in the oncocytoma. Both techniques showed concordant results in tumors with homogeneous karyotype. However, in tumors with several composite clones some discrepancies were observed, especially in cases of clear-cell RCC where chromosomal abnormalities present in a low number of metaphases could not be detected by CGH.

Comparative genomic hybridization analysis of transitional cell carcinomas of the renal pelvis.

We used comparative genomic hybridization to analyze 10 primary tumor samples from patients with transitional cell carcinoma of the renal pelvis. The most frequent loss was located at 9q, that is, in 50% of the tumors. Gains of DNA sequences were most frequently observed in chromosome regions 1q21 approximately q23, 2p23 approximately p25, 8q21.1 approximately q22 and in the whole chromosome 20. High level amplifications at 1q21 approximately q25, 6p22 approximately p23, 8q21 approximately q22, 8q22 approximately q24.1, 11q13, and 12q14 approximately q21 were detected. Most of these regions have previously been reported to be involved in transitional cell carcinoma of the bladder, thus confirming the importance of an increasing number of chromosome imbalances in the development and progression of this type of tumors.

Cytogenetic characterization of a familial papillary renal cell carcinoma

We describe the first case of a familial renal cell carcinoma cytogenetically characterized as a papillary renal cell carcinoma. Cytogenetic and molecular studies were performed on primary renal cell carcinomas and normal kidney tissue from two members of the same family. Both patients showed a normal constitutional karyotype. The two tumors analyzed from the first patient showed the numerical chromosome alterations characteristic of papillary renal cell carcinomas. From the four tumors analyzed in the second patient, three of them presented the cytogenetic pattern of papillary renal cell tumors, and the fourth showed only structural chromosome abnormalities with the presence of a del(7)t(7;7) or dup(7) in all metaphases analyzed. Chromosome 3 was cytogenetically unaffected in all tumors from both patients, and restriction fragment length polymorphism analysis performed with probe pEFD145 (3p21.1-p23) did not detect any loss of heterozygosity.

Study of Allelic Losses on 3p, 6q, and 17p in Human Urothelial Cancer

Forty-eight transitional cell carcinomas of the bladder and three transitional cell carcinomas of the renal pelvis were examined for loss of heterozygosity (LOH) on chromosomes 3p, 6q, and 17p. The most frequent allelic loss was seen on 17p (18/36, 50%) followed by 6q (6/22, 27%), and 3p (5/22, 23%). In cases with LOH at more than one locus, the same DNA sample often varied in degree of signal reduction for missing alleles. This observation indicates that LOH studies can serve to detect intratumor heterogeneity. No correlation was found between allelic losses at these chromosome arms and tumor grade and stage. Allelic losses on 6q were associated with tumors having a solid growth pattern; in this kind of tumors, allelic losses on 3p were associated with invasion.

Analysis of 3p Allelic Losses in Renal Cell Carcinomas: Comparison with Cytogenetic Results

We performed a study of loss of heterozygosity (LOH) at 3p by restriction fragment length polymorphism analysis in a series of 22 renal tumors. In 11 cases, molecular results could be compared with those of cytogenetic studies. The highest frequency of allelic losses at 3p was seen in clear cell non-papillary renal tumors, whereas none of the papillary renal cell carcinomas showed LOH at 3p. Allelic losses on 3p were found to be independent of tumor grade or stage or both. One case analyzed showed a discrepancy between cytogenetic and LOH studies. This tumor displayed rearrangements of chromosome 3 and no LOH at the c-RAF-1 (close to the Von Hippel Lindau gene) locus.

A case of transitional cell carcinoma of the bladder with a del(9)(q11q21.2).

Monosomy for chromosome 9, as well as loss of heterozygosity for markers on this chromosome, has been detected in a high percentage of transitional cell carcinomas (TCC) of the bladder. We report a case of a TCC of the bladder with an interstitial del(9)(q11q21.2) that could be indicative of the presence of a putative tumor-suppressor gene related to bladder tumor progression. To elucidate the role of chromosome 9 in bladder tumors, it would be interesting to study a possible loss of heterozygosity in this chromosome region.

Acute lymphoblastic leukemia with e1a3 BCR/ABL fusion protein. A report of two cases

B Acute Lymphoblastic leukemia (B-ALL) with Philadelphia chromosome (Ph′) is a neoplasm of lymphoblast committed to the B cell lineage. The clinical presentation of B-ALL Ph′+ is similar to B-ALL, but is more common in adults than in children. The e1a3 rare variant is produced by the fusion of BCR exon 1 to ABL exon 3. The presence of this translocation has been associated with good disease outcome for chronic myeloid leukemia in a very small series of only 5 cases; there is no such evidence for B-ALL. We report two new cases of B-ALL Ph+ with the rare e1a3 fusion transcript. The e1a3 and e1a2 (p190) transcripts have been reported to have a similar molecular weight and probably a similar clinical profile, thus in these cases the presence of e1a3 was associated with extramedullary infiltration and disease acceleration.

DNA hypermethylation at the D17S5 locus is not a frequent event in human urothelial cancer

Objective To analyse the DNA methylation status and the loss of heterozygosity (LOH) at the D17S5 locus (17p13.3) in urothelial cancer.