Molecular characterization of the canine HMGB1.

Due to the close similarities of numerous canine diseases to their human counterparts, the dog could join the mouse as the species of choice to unravel the genetic background of complex diseases as e.g. cancer and metabolic diseases. Accordingly, the role of the dog as a model for therapeutic approaches is strongly increasing. However, prerequisite for such studies is the characterization of the corresponding canine genes. Recently, the human high mobility group protein B1 (HMGB1) has attracted considerable interest of oncologists because of what is called its "double life". Besides its function as an architectural transcription factor HMGB1 can also be secreted by certain cells and then acts as a ligand for the receptor for advanced glycation end products (RAGE). The binding of HMGB1 to RAGE can activate key cell signaling pathways, such as p38(MAPK), JNK, and p42/p44(MAPK) emphasizing the important role of HMGB1 in inflammation and tumor metastasis. These results make HMGB1 a very interesting target for therapeutic studies done in model organisms like the dog. In this study we characterized the molecular structure of the canine HMGB1 gene on genomic and cDNA levels, its predicted protein, the gene locus and a basic expression pattern.

High mobility group protein HMGA1 expression in breast cancer reveals a positive correlation with tumour grade.

Members of the HMGA protein (high mobility group protein A) family act as master switches of the chromatin structure by bending DNA and thus modulating the formation of transcription factor complexes of a number of target genes. Accordingly, HMGA proteins have been shown to be associated with the development and/or progression of a variety of benign and malignant tumours. Nevertheless, the HMGA1 expression studies published so far have not included primary breast cancer samples. In this study we have investigated the HMGA1 expression patterns in a series of 170 breast cancer samples by immunohistochemistry. We have found a strong variation in HMGA1 expression between the tumours. Based on an immunoreactive score (IRS) 14.1% of the tumour samples were scored to IRS 8-12 (strong positivity for HMGA1), 24.7% were scored to IRS 4-6 (moderate positivity), 25.3% were scored to IRS 1-3 (weak positivity), and 35.9% showed no positivity at all. Immunoreaction could be detected in all histological types of breast cancers analysed with the exception of invasive papillary and cribriform carcinoma. Statistical analysis revealed a strong correlation between tumour grade and HMGA1 expression (rs=0.3516, p<0.0001). Thus, the HMGA1 expression level can be considered a potential prognostic marker for breast cancer.

Indications for therapy for fungemia in postoperative patients.

We reviewed the clinical courses of 63 surgical patients who had experienced one or more days of fungemia, to determine the clinical setting for such infections and to define indications for systemic therapy. Fifty-one patients experienced fungemia as a late complication of intraperitoneal infection. Candida was identified as part of a polymicrobial flora in 70%. If untreated, the mortality was 83% (30 of 36). No untreated patients with fungemia for more than one day survived. Adequate therapy with amphotericin B (total dose, greater than 3 mg/kg) improved survival to 67% (ten of 15). Autopsies performed in 20 cases revealed visceral Candida microabscesses in seven, with the gastrointestinal tract (12) and intraabdominal abscess (five) as the most common sources of fungi. These data support the concept of Candida as an important participant in polymicrobial infection and recommend therapy with amphotericin B for patients with intraperitoneal infection experiencing fungemia.

Variation of HMGB1 expression in breast cancer.

The amount of steroid hormone receptor proteins does not always correlate with the response of breast cancers to endocrine therapy. This may partly be due to the fact that binding of the estrogen receptor (ER) to estrogen responsive elements (ERE) of its target genes is mediated by additional cellular proteins. One of these is the high mobility group protein HMGB1, known to interact with ER thus dramatically increasing its binding to ERE. This is the first report analysing the expression patterns of HMGB1 in breast cancer cells. Northern blot analyses of the 1.4 kb and the 2.4 kb transcripts of HMGB1 in 13 breast cancer samples revealed a strong intertumoural variation by a factor of 8.5 and 14.5, respectively. This variation may contribute to the different response, of estrogen receptor-positive breast tumours to endocrine therapy, making HMGB1 a marker of considerable clinical interest.

Back to the roots of a new exon--the molecular archaeology of a SP100 splice variant.

Retropseudogenes are intronless DNA sequences sharing a high degree of homology with the cDNA of their corresponding active genes. They are thought to have originated by reverse transcription of messenger RNA and reintegration of the cDNA into the genome. Usually considered a type of evolutionary waste, they melt into the background of their surrounding DNA by the loss of similarity to the active gene or disappear from the genome by the accumulation of deletions. On the other hand, in this paper we describe the evolutionary recycling of this genomic waste. Recently, a splice variant of the gene encoding the nuclear protein SP100 was identified in which the 3' part of the cDNA is replaced by an alternative exon apparently encoding an HMG1-DNA-binding domain. We were able to show that this HMG box is contributed by a new exon arising from an HMG1 retropseudogene that we have molecularly characterized in detail. In addition to being found in human cells, corresponding fusion transcripts were shown in Pan troglodytes, Gorilla gorilla, and Hylobates lar, but not in Macaca mulatta. Genomic DNA from M. mulatta enabled us to amplify by PCR the 5' part but not the 3' part of the HMG1 retropseudogene. From our data we thus can date the underlying retrotransposition to more than 35 million years ago. Our findings offer a model as to how new exons may evolve during evolution. To our knowledge this is the first example of a retropseudogene becoming part of an active gene in which both parental parts are well characterized and remain in-frame with their cDNA.