In breast cancer, overexpression of the small heat shock protein, HSP-27, is associated with increased anchorage-independent growth, increased invasiveness, and resistance to chemotherapeutic drugs and is associated with poor prognosis and reduced disease-free survival. Therefore, factors that increase the expression of HSP-27 in breast cancer are likely to affect the prognosis and outcome of treatment. In this study, we show a strong correlation between elevated levels of the Brn-3b POU transcription factor and high levels of HSP-27 protein in manipulated MCF-7 breast cancer cells as well as in human breast biopsies. Conversely, HSP-27 is decreased on loss of Brn-3b. In cotransfection assays, Brn-3b can strongly transactivate the HSP-27 promoter, supporting a role for direct regulation of HSP-27 expression. Brn-3b also cooperates with the estrogen receptor (ER) to facilitate maximal stimulation of the HSP-27 promoter, with significantly enhanced activity of this promoter observed on coexpression of Brn-3b and ER compared with either alone. RNA interference and site-directed mutagenesis support the requirement for the Brn-3b binding site on the HSP-27 promoter, which facilitates maximal transactivation either alone or on interaction with the ER. Chromatin immunoprecipitation provides evidence for association of Brn-3b with the HSP-27 promoter in the intact cell. Thus, Brn-3b can, directly and indirectly (via interaction with the ER), activate HSP-27 expression, and this may represent one mechanism by which Brn-3b mediates its effects in breast cancer cells.

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The Brn-3 family of transcription factors play a critical role in regulating expression of genes that control cell fate, including the small heat shock protein Hsp27. The aim of this study was to investigate the relationship between Brn-3a and Brn-3b and Hsp27 expression in the developing rodent heart. Brn-3a and Brn-3b were detected from embryonic days 9.5-10.5 (E9.5-E10.5) in the mouse heart, with significant increases seen later during development. Two isoforms (long and short) of each protein were detected during embryogenesis and postnatally. Brn-3a messenger RNA (mRNA) and protein were localized by E13.0 to the atrio-ventricular (AV) valve cushions and leaflets, outflow tract (OFT), epicardium and cardiac ganglia. By E14.5, Brn-3a was also localised to the septa and compact ventricular myocardium. An increase in expression of the long Brn-3a(l) isoform between E17 and adult coincided with a decrease in expression of Brn-3b(l) and a marked increase in expression of Hsp27. Hearts from Brn-3a-/- mice displayed a partially penetrant phenotype marked by thickening of the endocardial cushions and AV valve leaflets and hypoplastic ventricular myocardium. Loss of Brn-3a was correlated with a compensatory increase in Brn-3b and GATA3 mRNA but no change in Hsp27 mRNA. Reporter assays in isolated cardiomyocytes demonstrated that both Brn-3a and Brn-3b activate the hsp27 promoter via a consensus Brn-3-binding site. Therefore, Brn-3 POU factors may play an important role in the development and maintenance of critical cell types and structures within the heart, in part via developmental regulation of myocardial Hsp27 expression. Furthermore, Brn-3a may be necessary for correct valve and myocardial remodelling and maturation.

L eft ventricular rupture and formation of a pseudoaneurysm is a well-recognized complication after mitral valve replacement. With an incidence of Ϸ1.2%, it is extremely rare and potentially fatal. 1 We describe such a case in the setting of infective endocarditis.A 47-year-old man came into casualty reporting fever, chest pain, and shortness of breath. His history included 25 years as an intravenous drug user, injecting heroin and methadone, and being positive for hepatitis C. He had recently experienced an abscess in the groin after the use of this site for injection. On examination, he was found to be pyrexial (39.4°C) and tachycardic, with a blood pressure of 142/97 mm Hg. He had a harsh apical pansystolic murmur, nail fold infarcts, and splinter hemorrhages in his hands and feet. Blood tests showed a C-reactive protein count of 236 mg/L and a white cell count of 6.8ϫ10 9 , with the differential being 6.3ϫ10 9 (91%) neutrophils, 0.1ϫ10 9 (1%) lymphocytes, and 0.5ϫ10 9 (7%) monocytes. His initial transthoracic echocardiogram revealed a grossly disrupted mitral valve with severe mitral regurgitation and hyperdynamic left ventricular function. The left ventricular wall was diffusely thickened just below the posterior mitral annulus, with focal translucent areas highly suggestive of an abscess cavity (Figure 1). Given these findings, he was referred immediately to cardiothoracic surgeons with a diagnosis of Staphylococcus aureus endocarditis secondary to intravenous drug use. The valve was shown to have extensive destruction, with a large vegetation on the posterior leaflet. Both mitral leaflets were completely excised, with further removal of infected and necrotic tissue around the annulus. The valve was replaced with a 31-mm perimount pericardial valve. The tissue around the posterior margin of the sewing ring was of very poor quality, edematous, and infected with multiple abscess cavities. In view of this, it was decided to perform his repair in 2 stages: first, to remove the infected tissue and replace the valve, and second, to seal the aneurysm. The patient subsequently made a good recovery, and although his inflammatory markers returned to normal, he remained pyrexial. In the following days, he continued to have a low-grade fever, and further echocardiography determined that he had a persistent pericardial effusion that failed to resolve. Three and a half weeks later, he was found to be short of breath on exertion, with persistent tachycardia. Echocardiography revealed a large posterolateral pseudoaneurysm measuring Ϸ8ϫ6 cm, which exhibited free-flowing color into the aneurysm cavity (Figure 2). His mitral valve showed moderate regurgitation, with the persistent pericardial effusion showing signs of tamponade. It was therefore decided to perform the second stage of his surgery at this time. The pseudoaneurysm was well demarcated, fibrosed, and sealed with interrupted mattress sutures 2 and the perimount valve was replaced with a 31-mm pericardial valve. The patient was then continued on intravenous antibio...