Piere Rogalla

Angiogenetic signaling through hypoxia: HMGB1: an angiogenetic switch molecule.

The initiation of angiogenesis, called the angiogenetic switch, is a crucial early step in tumor progression and propagation, ensuring an adequate oxygen supply. The rapid growth of tumors is accompanied by a reduced microvessel density, resulting in chronic hypoxia that often leads to necrotic areas within the tumor. These hypoxic and necrotic regions exhibit increased expression of angiogenetic growth factors, eg, vascular endothelial growth factor, and may also attract macrophages, which are known to produce a number of potent angiogenetic cytokines and growth factors. A group of molecules that may act as mediators of angiogenesis are the so-called high-mobility group proteins. Recent studies showed that HMGB1, known as an architectural chromatin-binding protein, can be extracellularly released by passive diffusion from necrotic cells and activated macrophages. To examine the angiogenetic effects of HMGB1 on endothelial cells an in vitro spheroid model was used. The results of the endothelial-sprouting assay clearly show that exogenous HMGB1 induced endothelial cell migration and sprouting in vitro in a dose-dependent manner. Thus, this is the first report showing strong evidence for HMGB1-induced sprouting of endothelial cells.

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.

An extended nomenclature of the canine karyotype

In contrast to many other animals, knowledge about the canine karyotype is quite sparse. This is due in part to the rather difficult canine karyotypic pattern. Except for the X and the Y chromosome, there are only acrocentric chromosomes, which appear to be quite small and difficult to identify unambiguously. In previous reports, schematic representations of the canine karyotype have been described. However, a nomenclature comparable to that of the human karyotype or the karyotypes of sheep, cattle, or goats does not yet exist for the dog. Based on high-resolution banding of metaphase chromosomes from canine fibroblasts, we propose an ideogram of the canine karyotype with 460 numbered bands and characteristic landmarks. In addition, the centromere positions of the canine chromosomes are determined by a combined GTG-banding/FISH approach, and the R- and G-banding patterns are compared.

HMGA2 expression in uterine leiomyomata and myometrium: Quantitative analysis and tissue culture studies

The high mobility group gene, HMGA2, is frequently expressed in uterine leiomyomata (UL) with chromosomal rearrangements of 12q15. In contrast, HMGA2 expression has not been detected in karyotypically normal UL or in myometrium, but has been detected in these tissues after culture. To characterize further the expression pattern of HMGA2, we assessed HMGA2 expression by RT‐PCR followed by Southern blot hybridization, and by real‐time PCR in three tissue panels: (1) primary myometrial cultures, (2) uncultured tissue from 15 karyotypically normal samples consisting of eleven 46,XX UL and four matched myometrial specimens, and (3) uncultured tissue from ten UL with 12q15 rearrangements and three matched myometrial specimens. HMGA2 expression was detected in all samples from the three panels. The level of HMGA2 expression in karyotypically normal UL was similar to the level of expression in myometrium; however, it was significantly less than the level measured in UL with 12q15 rearrangements. This expression analysis by use of detection methods of different sensitivities underscores the importance of studies of HMGA2 expression in uncultured tissues and of careful interpretation of results from experiments on cultured cells. Moreover, detection of HMGA2 expression in myometrium and in UL without 12q15 rearrangements, tissues previously thought not to express HMGA2, suggests that HMGA2 expression is required in normal adult myometrial physiology.

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.

HMGIC Expressed in a Uterine Leiomyoma with a Deletion of the Long Arm of Chromosome 7 Along with a 12q14–15 Rearrangement But Not in Tumors Showing del(7) as the Sole Cytogenetic Abnormality

Cytogenetic studies on uterine leiomyomas have shown that more than 60% of these tumors possess a normal karyotype and that 30% have clonal chromosomal aberrations. The most frequent changes are aberrations involving 12q14-15 and show rearrangements of the long arm of chromosome 7. Recently, we were able to demonstrate that in a variety of mesenchymal tumors showing 12q14-15 aberrations the HMGIC gene is rearranged thus playing a role in tumorigenesis. Here we report the results of HMGIC expression studies by RT-PCR of five uterine leiomyomas with different karyotypes. The RT-PCR studies were performed on two primary tumors showing a 12q14-15 aberration, one of which with an additional del(7) and three tumors with del(7) as the sole aberration. The tumor with the 12q14-15 aberration as the sole alteration and the leiomyoma with 12q14-15 rearrangement plus deletion of the long arm of chromosome 7 were shown to express HMGIC. In contrast, in all three tumors with the del(7) as the sole aberration no expression of HMGIC was noted.

Human HMGA2 promoter is coregulated by a polymorphic dinucleotide (TC)-repeat

HMGA proteins are thought to be causally involved in the progression of different diseases, including benign and malignant tumors, obesity, arteriosclerosis, and restenosis. As HMGA proteins are architectural transcription factors, their binding to DNA leads to changes in DNA-conformation modulating the environment for the assembly and function of transcriptional complexes, thus influencing the expression of a huge variety of genes. Despite the emerging role of HMGA proteins for important diseases, only limited information is available about mechanisms regulating the expression of the HMGA2 gene. In this report, 2240 bp of the 5′ flanking region of the HMGA2 gene were functionally analyzed by luciferase assay experiments. Besides the identification of novel positive and negative regulatory elements, it was shown that transcription is initiated from two independent promoter regions within cell lines HeLa, MCF7, and L14TSV40. Furthermore, a functional polymorphic dinucleotide repeat (TCTCT(TC)n) 500 bp upstream of the ATG translational start codon was found to regulate strongly the human HMGA2 promoter with an activation pattern that correlates to its TC-repeat length.

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.

Telomeric repeat fragment lengths are not correlated to histological grading in 85 breast cancers

The mean telomeric repeat fragment (TRF) lengths of 85 breast cancer samples were determined. The TRF length varied between 7260 bp and 14570 bp (average 11370 bp) reflecting a unimodal distribution. There was no significant correlation between TRF length and the histological grade of the tumor. Neither were there differences in telomeric length between different histological types of tumors, in particular lobular and ductal types, nor correlations between TRF length and age of patient, tumor volume, lymph node status, or steroid receptor status. These results contradict the hypothesis that the telomere repeat fragment sizes represent limiting or promoting factors for the growth of breast cancer.