Barbro Wedell

Chromosome studies in thyroid neoplasia

Cytogenetic studies in thyroid neoplasia were performed by G‐banding of chromosome preparations obtained from the in vitro cultures of nine adenomas, one follicular carcinoma, five papillary carcinomas, and two medullary carcinomas. Complex structural chromosome aberrations were found in one adenoma. Two more adenomas, both composed of Hürthle cells, showed multiple numerical chromosome deviations with trisomy 4 and tetrasomy 7 in common. Six metastasizing carcinomas were characterized by normal stemlines, which indicates that malignancy in thyroid neoplasia cannot be excluded by cytogenetic techniques used currently. Comparisons between cytogenetic findings and cytophotometric DNA measurements in the material studied illustrate that euploid tumors represent a heterogenous group including cases with various gross structural chromosome aberrations of yet unknown clinical significance. Further studies of additional material with long‐term follow‐up are called for by our findings of structural and numerical chromosome aberrations in follicular neoplasms that are benign according to histologic criteria.

High‐resolution genomic profiling of adenomas and carcinomas of the salivary glands reveals amplification, rearrangement, and fusion of HMGA2

Carcinoma ex pleomorphic adenoma (Ca‐ex‐PA) is an epithelial malignancy developing within a benign salivary gland pleomorphic adenoma (PA). Here we have used genome‐wide, high‐resolution array‐CGH, and fluorescence in situ hybridization to identify genes amplified in double min chromosomes and homogeneously staining regions in PA and Ca‐ex‐PA and to identify additional genomic imbalances characteristic of these tumor types. Ten of the 16 tumors analyzed showed amplification/gain of a 30‐kb minimal common region, consisting of the 5′‐part of HMGA2 (encoding the three DNA‐binding domains). Coamplification of MDM2 was found in nine tumors. Five tumors had cryptic HMGA2‐WIF1 gene fusions with amplification of the fusion oncogene in four tumors. Expression analysis of eight amplified candidate genes in 12q revealed that tumors with amplification/rearrangement of HMGA2 and MDM2 had significantly higher expression levels when compared with tumors without amplification. Analysis of individual HMGA2 exons showed that the expression of exons 3–5 were substantially reduced when compared with exons 1–2 in 9 of 10 tumors with HMGA2 activation, indicating that gene fusions and rearrangements of HMGA2 are common in tumors with amplification. In addition, recurrent amplifications/gains of 1q11‐q32.1, 2p16.1‐p12, 8q12.1, 8q22‐24.1, and 20, and losses of 1p21.3‐p21.1, 5q23.2‐q31.2, 8p, 10q21.3, and 15q11.2 were identified. Collectively, our results identify HMGA2 and MDM2 as amplification targets in PA and Ca‐ex‐PA and suggest that amplification of 12q genes (in particular MDM2), deletions of 5q23.2‐q31.2, gains of 8q12.1 (PLAG1) and 8q22.1‐q24.1 (MYC), and amplification of ERBB2 may be of importance for malignant transformation of benign PA.

Chromosomal patterns in human benign uterine leiomyomas

Chromosomal observations by banding technique in 18 short-term cultured human uterine leiomyomas are reported. Half of the tumors had a primary or secondary abnormal stemline. They were usually characterized only by structural changes, in particular reciprocal translocations or insertions. Reviewing already published cases together with the new material confirmed that the aberrations in abnormal stemlines predominantly affected chromosomes 1, 2, 6, 7, 12, 14, and X. In these chromosomes the regions 1p36, 2p24, 6p12-21, 7q21-31, 12q13-15, 14q22-24, and the short arm of the X chromosome were preferentially affected. As in two other thoroughly studied human benign tumors, the pleomorphic adenoma and the meningioma, the very specific but sometimes complex chromosomal aberrations in leiomyomas could well be events of primary evolutionary importance. Likewise, in cases with a normal stemline, it is possible that comparable changes in the corresponding specific chromosomal regions have occurred at a submicroscopic level. Ascertaining this possibility, as well as the role of the aberrations with regard to the benign nature of the tumors, must be the focus of future analysis using molecular techniques.

Significance of the choice of tissue culture technique on the chromosomal patterns in human mixed salivary gland tumors

Cytogenetic observations by banding methods in 56 new cases of human benign pleomorphic adenomas are reported. Thirty of the cases (series I) were studied in preparations from primary cultures established from cells growing out from mechanically dispersed tumor pieces. The remaining 26 cases (series II) were analyzed in preparations from primary cultures established from enzymatically pretreated material. The use of the latter method resulted in a decrease in the frequency of cases with a normal stemline from about 53% to about 19%. However, the general characteristics of the aberrations observed in abnormal stemlines in both series agreed well. The minor differences observed consisted of a higher frequency of recurrent t(3;8)(p21;q12) in series II and, in the same series, fewer cases showing an involvement of 8q or 12q. The present results emphasize the importance of molecular studies of, in particular, the regions 8q12, 12q13-15, and 3p21.

High-resolution array CGH analysis of salivary gland tumors reveals fusion and amplification of the FGFR1 and PLAG1 genes in ring chromosomes.

We have previously identified a subgroup of pleomorphic salivary gland adenomas with ring chromosomes of uncertain derivation. Here, we have used spectral karyotyping (SKY), fluorescence in situ hybridization (FISH) and high-resolution oligonucleotide array-CGH to determine the origin and content of these rings and to identify genes disrupted as a result of ring formation. Of 16 tumors with rings, 11 were derived from chromosome 8, 3 from chromosome 5 and 1 each from chromosomes 1, 6 and 9. Array-CGH revealed that 10/11 r(8) consisted of amplification of a 19 Mb pericentromeric segment with recurrent breakpoints in FGFR1 in 8p12 and in PLAG1 in 8q12.1. Molecular analyses revealed that ring formation consistently generated novel FGFR1–PLAG1 gene fusions in which the 5′-part of FGFR1 is linked to the coding sequence of PLAG1. An alternative mechanism of PLAG1 activation was found in tumors with copy number gain of an intact PLAG1 gene. Rings derived from chromosomes 1, 5, 6 or 9 did not result in gene fusions, but rather resulted in losses indicative of the involvement of putative tumor suppressor genes on 8p, 5p, 5q and/or 6q. Our findings also reveal a novel mechanism by which FGFR1 contributes to oncogenesis and further illustrate the versatility of the FGFR1 and PLAG1 genes in tumorigenesis.

Cytogenetic relationship between uterine lipoleiomyomas and typical leiomyomas

SummaryThe chromosomes from two human uterine lipoleiomyomas, L25 and L26, from the same patient, were studied by a banding technique applied to preparations from short-term cultures. Both tumors displayed the same pseudodiploid stemline characterized by the reciprocal translocationt (5; 12) (q12; q24). These observations coincide with the previous finding that the largest subgroup of typical leiomyomas with an abnormal stemline are characterized by a long-arm change of one chromosome No. 12. The combined results support the previously advanced hypothesis that different histologic subtypes of uterine leiomyomas are derived from a common totipotential stem cell. This interpretation also fits with a proposed theory about the derivation of malignant leiomyomatous uterine neoplasms.

Characterisation of a cell line (LCC-18) from a cultured human neuroendocrine-differentiated colonic carcinoma.

A cell line (LCC-18) from a neuroendocrine colonic tumour was established. The tumour cells retained their endocrine characteristics through more than 100 passages and showed positive immunocytochemistry for synaptophysin, vasoactive intestinal polypeptide (VIP) and glucagon. The culture medium also contained VIP and glucagon, which indicates that mechanisms for release of some of the active peptides were preserved. Transplantation of LCC-18 tumour cells into nude rats resulted in tumour formation with similar endocrine characteristics. The c-myc gene was amplified which might have been a prerequisite for establishment of the cell line. The chromosomes in LCC-18 were studied by G-banding and C-banding. The cell line had a distinctive mode in the hypotriploid region, at S = 61. The double minute (Dms) positive stemline karyotype showed numerical and structural aberrations more similar to findings in ordinary colonic adenocarcinomas than to observations in previously studied, pure intestinal neuroendocrine tumours. The Dms may be correlated with amplification of c-myc. LCC-18 may become valuable for studies of neuroendocrine differentiation, regulation of growth and production and release of hormones and for studies of drug effect.

Karyotypic variability and evolutionary characteristics of a polymorphous low grade adenocarcinoma in the parotid gland

The chromosomes of a polymorphous low-grade adenocarcinoma originating from a pleomorphic adenoma of the parotid gland were studied. Three successful preparations were performed. A minor fraction of cells showed normal karyotypes and some cells only inconsistent, usually numerical, deviations. The remaining cells constituted an abnormal monoclonal population with an unusual and very extensive karyotypic variability. The origin of most marker chromosomes could be wholly or partly clarified. Five different subclones could be distinguished on basis of different specific marker chromosomes. The characteristics of the marker sets suggested a closely interrelated derivation of the subclones. The results also provide insight as to the influence of random factors and/or differential growth rate on the chromosomal picture observed in in vitro systems. The present chromosomal observations showed no similarities either to the cytogenetical findings in the five previously reported salivary gland adenocarcinomas or to the deviations seen in the single studied case of carcinoma ex-pleomorphic adenoma.

Cytogenetic observations in a human gastric leiomyosarcoma

The chromosomes of a human gastric leiomyosarcoma were studied in preparations from short-term cultures. The tumor had a triploid-near-triploid modal population characterized by extensive numerical and structural changes. Of these deviations, del(1)(p12-13), monosomy 14, and underrepresentation of chromosomes 18 and 22 were abnormalities in common with two of the three previously studied leiomyosarcomas of the small bowel.

Human benign chondroblastoma with a pseudodiploid stemline characterized by a complex and balanced translocation

The chromosomes of a human benign chondroblastoma of the jaw were studied by in vitro technique. Approximately one-third of the analyzed cells had a normal karyotype. The remaining two-thirds constituted an abnormal monoclonal population with a complex and balanced translocation. The observations are different from those in previously studied benign primary bone tumors. The breakpoint in 22q, however, is similar or very close to that observed in two extraskeletal myxoid chondrosarcomas earlier reported.