[Predictive and prognostic markers of breast cancer. Molecular biological analysis of fixed tumor tissue]. / Prädiktive und prognostische Brustkrebsmarker. Molekularbiologische Analyse von fixiertem Tumorgewebe als Basis.

A multitude of prognostic and predictive multiparameter algorithms based on the analysis of mRNA have been published in recent years. Many of the algorithms require fresh or fresh frozen tissue as a source of the mRNA. However, practical considerations suggest formalin-fixed paraffin-embedded tissue (FFPE tissue) to be a more suitable starting material for routine diagnostic applications. Therefore, Siemens Healthcare Diagnostics is developing a fully automated method to extract mRNA and DNA from FFPE tissue for use in pathology laboratories. Initially, the method will be used as part of a prognosis assay to predict the likelihood of distant metastasis and death for node-negative breast cancer patients.

Oxygen dependent regulation of DNA synthesis and growth of Ehrlich ascites tumor cells in vitro and in vivo.

Ehrlich ascites cells were cultured under different O2 partial pressures from less than 0.1 ppm to 2 x 10(5) ppm. During the artificial hypoxia and following reoxygenation the DNA synthesis rate was measured and the relative frequency of replicon initiations was examined by analyzing the length distributions of replicative daughter strand DNA. These studies were complemented by evaluation of growth and cycling of the cells and by biochemical analyses. It was demonstrated that the reversible shut-down of clusters of replication units already described before (Probst, H., Gekeler, V., and Helftenbein, E. Exp. Cell Res., 154: 327-341, 1984) occurred between 0.25 and about 2.5 microM dissolved O2. Above 2.5 microM, a transition range to aerobiosis extended to about 16 microM O2. Below 0.25 microM O2, the cells suffered damage impairing the reversibility of the shutdown. The observed changes of growth and cycling correlated well with the respective changes of replication. Analogous oxygenation dependent regulatory events in replication were also observed during growth of the cells as an in vivo ascites tumor. Obviously, the particular oxygenation conditions in the peritoneal cavity strongly influence tumor growth via the oxygen dependent regulation of replication.

Application of hypoxia-induced shut down of replicon initiation to the analysis of replication intermediates in Ehrlich ascites cells.

Cultured Ehrlich ascites cells were subjected to hypoxic conditions for about 2 h, then reaerated or allowed to remain hypoxic. The newly formed DNA of hypoxic or reaerated cells was labeled with [3H]thymidine using different pulse and pulse/pulse-chase protocols. The chain length distribution of the labeled DNA molecules was analysed by sedimentation after lysing the cells on the top of alkaline sucrose gradients. The results indicated that the hypoxia effectively and reversibly suppressed the initiation of new replication units. Initiation, growth and integration of Okazaki pieces into active replicons was not noticeably affected. In marked contrast to aerobic cells, the use of hypoxic cells allows the separation of Okazaki pieces as a distinct class of pulse labeled short DNA chains. Short daughter DNA of very recently initiated replicons did not interfere at pulse times shorter than 4 min. For examination of the newly initiated replicons it seems favourable to trigger a burst of initiations by reaeration.

Assignment of the human progesterone receptor to the q22 band of chromosome 11.

The human progesterone receptor gene was localized by in situ hybridization to the q22 band of chromosome 11.

Two distinct estrogen-regulated promoters generate transcripts encoding the two functionally different human progesterone receptor forms A and B.

The human progesterone receptor (hPR) cDNA, synthesized from T47D breast cancer cells, and the hPR gene 5'-flanking region were cloned and sequenced. Comparison of the cDNA-deduced amino acid sequence with other PR homologues demonstrated the modular structure characteristic of nuclear receptors. As in the case of the chicken homologue, there are two hPR forms, A and B, which originate from translational initiation at AUG2 (codon 165) and AUG1, respectively. Northern blot analysis of T47D mRNA using various cDNA derived probes identified two classes of hPR mRNAs, one of which could code for hPR form B, while the other one lacked the 5' region upstream of AUG1. S1 nuclease mapping and primer extension analyses confirmed that the second class of hPR transcripts are initiated between +737 and +842 and thus encode hPR form A, but not form B. By using the hPR gene 5'-flanking sequences as promoter region in chimeric genes, we show that a functional promoter (located between -711 and +31) directs initiation of hPR mRNAs from the authentic start sites located at +1 and +15. Most importantly, initiation of transcription from chimeric genes demonstrated the existence of a second promoter located between +464 and +1105. Transient co-transfection experiments with vectors expressing the human estrogen receptor showed that both promoters were estrogen inducible, although no classical estrogen responsive element was detected in the corresponding sequences. When transiently expressed, the two hPR forms similarly activated transcription from reporter genes containing a single palindromic progestin responsive element (PRE), while form B was more efficient at activating the PRE of the mouse mammary tumor virus long terminal repeat. Transcription from the ovalbumin promoter, however, was induced by hPR form A, but not by form B.