Expression of COX-2 and HER-2/neu and estrogen and progesterone receptor in primary squamous cell carcinomas of the endometrium

PURPOSE

Primary endometrial squamous cell carcinoma (ESCC) are rare but aggressive malignancies. To evaluate therapeutically relevant molecules, ESCC were investigated immunohistochemically.

MATERIAL AND METHODS

Eight ESCC were stained with antibodies against estrogen and progesterone receptors, HER-2/neu, and COX-2 followed by semiquantitative evaluation of the staining results.

RESULTS

Seven out of eight ESCC were negative for estrogen receptor as well as for HER-2/neu. Four tumors showed positivity for progesterone receptor. All ESCC displayed COX-2 overexpression.

CONCLUSIONS

Primary ESCC are probably not under hormonal control of estrogens and lack HER-2/neu expression. Thus, anti-hormonal or antibody therapy with herceptine is not indicated. The use of COX-2 inhibitors might be a therapeutic alternative in ESCC that requires further investigation.

Role of retinoid receptor coactivator pockets in cofactor recruitment and transcriptional regulation

The nuclear receptor for retinoic acid (RAR) forms a heterodimeric complex with the retinoid X receptor (RXR). This RXR/RAR heterodimer binds to the promoter of retinoic acid target genes and recruits coactivators and corepressors to regulate gene expression. Currently, the relative role of each receptor monomer in regulating coactivator and corepressor recruitment remains unclear. Here we show that the receptor-associated coactivator 3 (RAC3) uses two separate LXXLL motifs to bind RAR and RXR. The mutation of the coactivator-binding pockets of RAR and RXR abolishes RAC3 binding. Although the coactivator pocket of RXR is essential for the function of the RXR homodimer, it has a minor role for the recruitment of RAC3 and trans-activation by the RXR/RAR heterodimer. Consistently, deletion of the activation helix of RXR enhances binding of RAC3 to the heterodimer, and mutation of the coactivator pocket of RXR had little effect on RXR/RAR activity. In contrast, the coactivator pocket and the activation helix of RAR are absolutely required. We also show that different residues of the RAR coactivator pocket are used differently for interactions with the corepressor silencing mediator for retinoid and thyroid hormone receptor (SMRT) and coactivator. These results indicate a differential role for each retinoid receptor to the overall binding of cofactors and regulation of transcription by the retinoid receptor heterodimer.

Dominant effector genetics in mammalian cells

We have expressed libraries of peptides in mammalian cells to select for trans-dominant effects on intracellular signaling systems. As an example-and to reveal pharmacologically relevant points in pathways that lead to Taxol resistance-we selected for peptide motifs that confer resistance to Taxol-induced cell death. Of several peptides selected, one, termed RGP8.5, was linked to upregulation of expression of the gene ABCB1 (also known as MDR1, for multiple drug resistance) in HeLa cells. Our data indicate that trans-dominant effector peptides can point to potential mechanisms by which signaling systems operate. Such tools may be useful in functional genomic analysis of signaling pathways in mammalian disease processes.

The SRC family of nuclear receptor coactivators

Nuclear hormone receptors are ligand-dependent transcription factors that regulate genes critical to such biological processes as development, reproduction, and homeostasis. Interestingly, these receptors can function as molecular switches, alternating between states of transcriptional repression and activation, depending on the absence or presence of cognate hormone, respectively. In the absence of hormone, several nuclear receptors actively repress transcription of target genes via interactions with the nuclear receptor corepressors SMRT and NCoR. Upon binding of hormone, these corepressors dissociate away from the DNA-bound receptor, which subsequently recruits a nuclear receptor coactivator (NCoA) complex. Prominent among these coactivators is the SRC (steroid receptor coactivator) family, which consists of SRC-1, TIF2/GRIP1, and RAC3/ACTR/pCIP/AIB-1. These cofactors interact with nuclear receptors in a ligand-dependent manner and enhance transcriptional activation by the receptor via histone acetylation/methylation and recruitment of additional cofactors such as CBP/p300. This review focuses on the mechanism of action of SRC coactivators in terms of interactions with receptors and activation of transcription. Specifically, the roles of the highly conserved LXXLL motifs in mediating SRC function will be detailed. Additionally, potential diversity among SRC family members, as well as several recently cloned SRC-associated cofactors, will be discussed.

Sequestration and inhibition of Daxx-mediated transcriptional repression by PML

PML fuses with retinoic acid receptor alpha (RARalpha) in the t(15;17) translocation that causes acute promyelocytic leukemia (APL). In addition to localizing diffusely throughout the nucleoplasm, PML mainly resides in discrete nuclear structures known as PML oncogenic domains (PODs), which are disrupted in APL and spinocellular ataxia cells. We isolated the Fas-binding protein Daxx as a PML-interacting protein in a yeast two-hybrid screen. Biochemical and immunofluorescence analyses reveal that Daxx is a nuclear protein that interacts and colocalizes with PML in the PODs. Reporter gene assay shows that Daxx drastically represses basal transcription, likely by recruiting histone deacetylases. PML, but not its oncogenic fusion PML-RARalpha, inhibits the repressor function of Daxx. In addition, SUMO-1 modification of PML is required for sequestration of Daxx to the PODs and for efficient inhibition of Daxx-mediated transcriptional repression. Consistently, Daxx is found at condensed chromatin in cells that lack PML. These data suggest that Daxx is a novel nuclear protein bearing transcriptional repressor activity that may be regulated by interaction with PML.

Differential mechanisms of nuclear receptor regulation by receptor-associated coactivator 3

Steroid and nuclear receptor coactivators (NCoAs) have been implicated in the regulation of nuclear receptor function by enhancing ligand-dependent transcriptional activation of target gene expression. We have previously isolated receptor-associated coactivator 3 (RAC3), which belongs to the steroid receptor coactivator family. In this study, we investigated the differential mechanisms by which RAC3 interacts with and modulates the transcriptional activity of different nuclear receptors. We found that the vitamin D receptor (VDR) and estrogen receptor beta interact with different alpha-helical LXXLL motifs of RAC3. Peptides corresponding to these motifs have diverse affinities for the VDR and estrogen receptor beta, and mutation of specific motifs differentially impairs the ability of RAC3 to interact with these receptors in vitro. Consequently, these mutations inhibit the enhancement of transcriptional activation by these receptors in vivo. Furthermore, we found that the activation function-2 (AF-2) domain of the retinoid X receptor interferes with RAC3 binding to a DNA-bound VDR/retinoid X receptor (RXR) heterodimer, whereas the VDR AF-2 domain is required for this interaction. These results suggest a receptor-specific binding preference for the different LXXLL motifs of RAC3, which may provide flexibility for RAC3 to differentially regulate the function of different nuclear receptors.

Characterization of receptor interaction and transcriptional repression by the corepressor SMRT

SMRT (silencing mediator of retinoic acid and thyroid hormone receptor) and N-CoR (nuclear receptor corepressor) are two related transcriptional corepressors that contain separable domains capable of interacting with unliganded nuclear receptors and repressing basal transcription. To decipher the mechanisms of receptor interaction and transcriptional repression by SMRT/N-CoR, we have characterized protein-protein interacting surfaces between SMRT and nuclear receptors and defined transcriptional repression domains of both SMRT and N-CoR. Deletional analysis reveals two individual nuclear receptor domains necessary for stable association with SMRT and a C-terminal helix essential for corepressor dissociation. Coordinately, two SMRT domains are found to interact independently with the receptors. Functional analysis reveals that SMRT contains two distinct repression domains, and the corresponding regions in N-CoR also repress basal transcription. Both repression domains in SMRT and N-CoR interact weakly with mSin3A, which in turn associates with a histone deacetylase HDAC1 in a mammalian two-hybrid assay. Far-Western analysis demonstrates a direct protein-protein interaction between two N-CoR repression domains with mSin3A. Finally we demonstrate that overexpression of full-length SMRT further represses basal transcription from natural promoters. Together, these results support a role of SMRT/N-CoR in corepression through the utilization of multiple mechanisms for receptor interactions and transcriptional repression.

Influence of anaesthesia and muscle relaxation on intubating conditions and sympathoadrenal response to tracheal intubation

BACKGROUND

The study aimed to assess the relative influence of anaesthesia and muscle relaxation on intubating conditions and the haemodynamic and catecholamine responses to tracheal intubation.

METHODS

Sixty ASA 1 or 2 patients were randomly assigned to one of four groups (15 patients each) that differed in the depth of anaesthesia (thiopentone plus fentanyl 2.5 microg x kg(-1) or thiopentone alone) and the degree of vecuronium-induced neuromuscular block (100% or > or =65%) at intubation. Muscle relaxation was measured at 0.1 Hz by means of mechanomyography. Heart rate (HR) and mean arterial blood pressure (MAP) were measured before and after induction of anaesthesia, and 1 min and 5 min following intubation, while adrenaline (A) and noradrenaline concentrations (NA) were determined from arterial blood samples.

RESULTS

Intubating conditions were improved primarily by providing complete muscle relaxation at the adductor pollicis muscle (P<0.001) and to a lesser extent by adding fentanyl to thiopentone (P=0.04). The response of HR and MAP to tracheal intubation was attenuated mainly by fentanyl (P<0.001). Complete muscle relaxation further diminished the response of MAP to intubation (P=0.03). Changes in A and NA were dependent on the depth of anaesthesia only (P < or =0.01).

CONCLUSION

The results of the study demonstrate that the sympathoadrenal response to intubation is attenuated by adding fentanyl (2.5 X kg[-1]) to an induction regimen with thiopentone, whereas provision of complete muscle relaxation at the adductor pollicis muscle is necessary to attain smooth intubating conditions.

[Paucity of interlobular bile ducts in twins and maternal abuse of psychopharmaceuticals during pregnancy]

We report the case of twins with intrahepatic cholestasis in "paucity of interlobular bile ducts". Both the children presented an associated cardiac defect even if dissimilar and a transient tubulopathy. Despite the presence of these alterations we suppose that these cases can be included among the group of rare nonsyndromic paucity of interlobular bile ducts. The different extent of the pathology in the two patients suggest a toxic etiology which could have struck more severely the twin who were less protected by the utero-placental barrier. In the literature reports we found some cases of extrahepatic biliary atresia related with maternal amphetamine addiction, but no cases of intrahepatic atresia. As during pregnancy the mother had abused of a number of drugs and in particular of amphetamine, we suppose that the amphetamine addiction can account for the hepatic pathology.

[Neurobehavioral evaluation of term and preterm neonates]

The Brazelton neonatal behavioral assessment scale in the actual version (1984) was used by the authors to examine neurobehavioral performance of two different groups of newborns (one fullterm and the other preterm). Although the average difference between gestational age in the two groups was not very high, the results show that the preterms were significantly inferior in habituation, motor and supplementary items. A lower gestational age results correlated with reduced performance in newborn.