Bernd Kazmierczak

Expression of HMGI-C, a member of the high mobility group protein family, in a subset of breast cancers: Relationship to histologic grade

The high‐mobility‐group (HMG) protein gene HMGI‐C is apparently involved in the genesis of a variety of benign human solid tumors with rearrangements of chromosomal region 12q14‐15 affecting the HMGI‐C gene. So far, no expression of HMGI‐C has been found in adult tissues, and no data are available on the expression of HMGI‐C in primary human malignant tumors of epithelial origin. Therefore, we analysed the HMGI‐C expression patterns in 44 breast cancer samples and 13 samples of nonmalignant adjacent tissue by hemi‐nested reverse transcriptase–polymerase chain reaction for HMGI‐C expression. There was no detectable expression of HMGI‐C in any nonmalignant adjacent breast tissues analyzed. In contrast, we found expression in 20 of 44 breast cancer samples investigated. In invasive ductal tumors, expression was noted predominantly in tumors with high histologic grade: 17 of 21 breast cancer samples with histologic grade 3 but only three of 16 samples with histologic grades 1 or 2 showed expression of HMGI‐C. In addition, all seven lobular breast cancer samples tested did not express HMGI‐C. From these results, we concluded that HMGI‐ C expression may be of pathogenetic or prognostic importance in breast cancer. Mol. Carcinog. 19:153–156, 1997.

A high frequency of tumors with rearrangements of genes of the HMGI(Y) family in a series of 191 pulmonary chondroid hamartomas.

Pulmonary chondroid hamartomas (PCHs) are benign mesenchymal tumors that often are characterized by specific chromosomal aberrations. Herein we report our cytogenetic and molecular cytogenetic (FISH) studies on 191 PCHs, including 48 previously published cases. In this series, 134/191 PCHs (70.2%) showed either abnormalities of chromosomal bands 6p21 (21 tumors), 12q14–15 (95 tumors), or had other abnormalities (18 tumors). Two tumors had a 6p21 aberration together with a 12q14–15 aberration. The most frequent translocations were t(12;14)(q15;q24) (19 cases) and t(6;14)(p21.3;q24) (18 cases), both in either simple or complex form. By FISH with cosmids spanning the gene encoding the high‐mobility‐group protein HMGIC, we were able to show a rearrangement within or close to HMGIC in all tumors with 12q14–15 abnormalities tested, in 11 tumors with an apparently normal karyotype, and in 4 tumors with complex abnormalities without cytogenetically visible alterations of chromosomes 12. Rearrangements of HMGIY or its immediate surroundings were shown for 21 cases with 6p21 aberrations and three cases with other chromosomal abnormalities but without cytogenetically visible alterations of chromosomes 6. Genes Chromosomes Cancer 26:125–133, 1999.

HMGIY is the target of 6p21.3 rearrangements in various benign mesenchymal tumors

Specific chromosomal abnormalities of chromosomal region 6p21.3 have been described in subsets of many benign mesenchymal tumors. In the presented study, we investigated a series of 36 such cases by FISH, and Southern blot analyses for HMGIY rearrangements. FISH results revealed that the chromosomal breakpoints of 11 pulmonary chondroid hamartomas (PCHs), 12 endometrial polyps (EPs), one lipoma, and two uterine leiomyomas (ULs) were located within a 80 kb region surrounding the HMGIY gene. In 11 PCHs and one UL the breakpoints were located 3′ of HMGIY, and one PCH showed a breakpoint 5′ of HMGIY. Southern blot analyses with intra‐ and extragenic probes were performed of primary tumor material or cell lines from one UL, three PCHs, and five EPs. In none of these cases was an intragenic rearrangement found. Finally, we were able to detect expression of truncated HMGIY transcripts by 3′‐RACE PCR. Our data clearly show the role of a further member of the HMGI family in the development of benign mesenchymal tumors. Although most of the breakpoints of the chromosomal translocations involving HMGIY are located outside the gene, aberrant transcripts resembling the structure of those observed in the case of HMGIC have been found. Our molecular investigations thus led to the identification of the molecular mechanism by which rearrangements of either of two closely related genes lead to the development of frequent benign mesenchymal tumors in humans. Genes Chromosomes Cancer 23:279–285, 1998.

HMGI-C, a member of the high mobility group family of proteins, is expressed in hematopoietic stem cells and in leukemic cells.

The human HMGI-C gene encoding a member of the high mobility group protein family normally is expressed only during embryonic/fetal development but in none of the adult tissues tested so far. Recently, the HMGI-C gene has attracted a lot of interest since its rearrangements seem to underlie the development of frequent benign mesenchymal tumors. We have therefore checked CD34 positive hematopoietic stem cells and their normal and malignant descendants for HMGI-C expression. CD34 positive stem cells from healthy donors and the leukemia samples tested were positive while all peripheral blood samples from healthy volunteers were negative. We have concluded that the expression of the HMGI-C gene in leukemia seems to be a secondary effect due to abnormal stem cell proliferation and might be a sensitive tumor marker for particular types of leukemia.

An identical HMGIC-LPP fusion transcript is consistently expressed in pulmonary chondroid hamartomas with t(3;12)(q27–28;q14–15)

The high frequency of the t(3;12)(q27–28;q14–15) in lipomas and pulmonary chondroid hamartomas (PCHs) makes the HMGIC‐LPP fusion gene the most common fusion gene in a human tumor known so far. Nevertheless, there is no in‐depth molecular analysis of the HMGIC‐LPP fusion transcripts in PCHs. Certainly, a possible molecular variability of the HMGIC‐LPP fusion may contribute to a better understanding of the histologic differences between lipomas and PCHs and the intratumoral histologic heterogeneity of PCHs. By RT‐PCR and restriction analysis, we have investigated the HMGIC‐LPP fusion transcripts in a series of 13 PCHs with t(3;12)(q27–28;q14–q15). HMGIC‐LPP fusion transcripts of identical size were found in all PCHs tested. In all tumors investigated, the fusion transcripts had the same structure, i.e., exons 1 to 3 of HMGIC and exons 9 to 11 of LPP encoding a protein composed of three AT‐hooks and two LIM‐domains. Our results clearly show that neither the histologic differences between lipomas and PCHs nor the histologic heterogeneity of PCHs can be explained by a molecular diversity of the HMGIC‐LPP fusion transcript.

Amplification and expression of the HMGIC gene in a benign endometrial polyp

In a totally benign endometrial polyp, double minute chromosomes were shown to contain an amplified and apparently nonrearranged HMGIC gene, expressed in the tumor cells, suggesting amplification of HMGIC through double minute chromosome formation as another hitherto unreported mechanism associated with the development of some mesenchymal tumors. Genes Chromosomes Cancer 22:95–99, 1998.

The t(3;12)(q27;q14-q15) with underlying HMGIC-LPP fusion is not determining an adipocytic phenotype

The HMGIC gene, located in chromosome band 12q15, is rearranged in many different benign human tumors, often resulting in its fusion to ectopic sequences from other genes. The t(3;12)(q27;q14–q15) fuses HMGIC with the LPP gene and has so far been described exclusively in lipomas. Thus, it can be hypothesized that this particular gene fusion determines the adipocytic differentiation. We studied five pulmonary chondroid hamartomas all showing a t(3;12)(q27;q14‐q15) that apparently was identical to the one observed in lipomas. By fluorescence in situ hybridization we found that both HMGIC and LPP are disrupted by this translocation. By RT‐PCR the existence of a HMGIC/LPP fusion gene was confirmed. These results show that the fusion is not specific for lipomas. We favor the hypothesis that it is an ectopic sequence fused to HMGIC that is responsible for a cell shift to an embryogenic stage. Following this hypothesis the phenotype of the tumor may be induced by extracellular signal transduction. Genes Chromosomes Cancer 22:100–104, 1998.

A KRAB zinc finger protein gene is the potential target of 19q13 translocation in benign thyroid tumors

In an attempt to identify the target gene of specific translocations involving chromosomal band 19q13 in benign follicular thyroid tumors, we have used two cell lines derived from benign thyroid tumors showing translocations with 19q13 breakpoints for fluorescence in situ hybridization mapping studies with cosmid and PAC clones located in a 400‐kbp region. The breakpoints of the chromosome 19 abnormalities mapped within a 140‐kb segment covered by a single PAC clone. Sequencing of part of this PAC clone allowed us to establish the cDNA sequence and the genomic structure of a candidate gene located in close vicinity to the breakpoints. The gene that we tentatively refer to as RITA (rearranged in thyroid adenomas) belongs to the KRAB zinc finger protein coding genes. From our results we have concluded that in the two cell lines investigated the breaks have occurred either within the 5′ untranslated region of RITA or in its close 5′ vicinity. By Northern blot analyses two transcripts of about 4.7 kbp and 5 kbp were detected in normal thyroid tissue as well as in other normal tissues tested. An additional 2.1‐kbp transcript was found only in testicular tissue. In contrast to all normal tissues, both cell lines with 19q aberrations expressed larger transcripts of approximately 5.5 kbp and 6.2 kbp. From the close vicinity to the breakpoint region, the expression patterns of the gene, and its type, we consider RITA a strong candidate target gene of the specific 19q aberrations in benign thyroid tumors. Genes Chromosomes Cancer 26:229–236, 1999.

Hamartoma of the breast with involvement of 6p21 and rearrangement of HMGIY

The first description of involvement of 6p21 and rearrangement of HMGIY in a hamartoma of the breast is in keeping with the emerging role of HMG genes in benign mesenchymal tumors. Genes Chromosom. Cancer 20:90–92, 1997.

Molecular cytogenetic characterization of del(7q) in two uterine leiomyoma-derived cell lines.

Uterine leiomyoma cytogenetically exhibits at least six chromosomally abnormal subgroups. The largest subgroup is characterized by deletions of the long arm of chromosome 7. Few molecular and fluorescence in situ hybridization data are available that have aimed at a better definition of the lesion. Here, we report the results of a partial molecular cytogenetic characterization of two del(7q) chromosomes that were derived from cell lines established from two uterine leiomyomas with del(7)(q22q32). By using a large series of ordered 7q markers, we were able to identify the most proximal and the most distal conserved markers, which delineate the size of the deletion and which allow for a more targeted approach to the nature and function of genes that are possibly relevant for the pathogenesis of the disorder. Genes Chromosom. Cancer 18:155–161, 1997.