Immunohistochemical analysis of the endoribonucleases Drosha, Dicer and Ago2 in smooth muscle tumours of soft tissues.

AIMS: The aims of the present study were to determine the protein levels and cellular distribution of the endoribonucleases Drosha, Dicer and Ago2, major components of the microRNA-processing machinery, in benign and malignant soft tissue smooth muscle tumours, and to correlate the cellular levels of these enzymes with clinicopathological parameters including tumour histopathological grade. METHODS AND RESULTS: Cellular levels of Drosha, Dicer and Ago2 were evaluated in 110 soft tissue leiomyosarcomas (LMS), 31 leiomyomas (LM) and normal smooth muscle (NSM) using immunohistochemistry. Drosha and Dicer were barely detectable in NSM, while augmented levels of these enzymes were observed in LM and LMS. This finding suggests that Drosha and Dicer are implicated in the development of smooth muscle neoplasms. Notably, cellular levels of Dicer were significantly greater in high-grade compared to low-grade LMS, implying its participation in the progression of these neoplasms. Ago2 was detected in NSM, as well as LM and LMS; its cellular levels were not associated with tumour grade. CONCLUSIONS: Our results provide novel evidence that Drosha, Dicer and Ago2 are probably involved in the pathobiology of human smooth muscle neoplasms and that Dicer could serve as potentially significant biomarker for LMS progression.

Analysis of Cox-2 expression in Wilms' tumor.

Cylooxygenase-2 (Cox-2) inhibitors have increasingly become therapeutic alternatives in some Cox-2-overexpressing neoplasms. As the treatment eligibility for these drugs hinges on Cox-2 expression, Cox-2 immunostaining has recently been widely examined in several malignant neoplasms. However, data on the expression of Cox-2 in Wilms' tumor (WT) are limited. In this study, we examined Cox-2 expression in 40 examples of WT to identify the prognostic impact, to evaluate the effects on tumorigenesis, and to answer the question of whether neoplasms with Cox-2 expression could benefit from treatment with specific Cox-2 inhibitors. Sections from paraffin-embedded tumor samples were immunostained by a standard ABC technique using Cox-2 mouse monoclonal antibody. As in other rare examples reported in the literature, Cox-2 immunoreactivity was analyzed and correlated with histological features and the staging of neoplasms. However, in contrast to other studies, we also evaluated the relation of Cox-2 positivity to age, sex, and survival of patients. The results of this study demonstrated that Cox-2 was ubiquitously expressed in all cases of WT and their neovasculature, independently of the type of neoplasm (tumors with a favorable or unfavorable histology), tissues which constitute the neoplasm (blastemal, mesenchymal and epithelial, heterologous or non-heterologous elements), patient age, sex, or stage of development and survival rate. Thus, Cox-2 inhibitors could be used for treating all cases of WT. Further studies, including molecular investigations, would be useful to confirm our hypotheses.

Myocyte changes and their left atrial distribution in patients with chronic atrial fibrillation related to mitral valve disease.

It has been found that the pulmonary veins and adjacent left atrial posterior wall (LAPW) are deeply involved in both the initiation and maintenance of atrial fibrillation (AF), and the identification of these high-risk sites has aroused great interest in investigating their histopathologic substrate. We used light and conventional electron microscopy to evaluate the differential myocyte and interstitial changes in LAPW and left atrial appendage (LAA) samples from 28 patients with chronic AF undergoing mitral valve surgery and from 12 autoptic controls. There were always more myocytes with loss of sarcomeres in the LAPW than in the LAA (19.9% +/- 7.7% versus 8.2% +/- 5.0%; P < .0001), and the LAPW showed more marked immunohistochemical evidence of dedifferentiation, characterized by the reexpression of smooth muscle actin. In pathological left atria, myocyte diameter in the LAPW and LAA was comparable (19.0 +/- 1.5 versus 18.5 +/- 2.0 microm; not significant) but larger than in the controls (11.9 +/- 0.8 and 12.1 +/- 1.3 microm, respectively; P < .0001). A terminal deoxynucleotidyltransferase assay did not reveal any myocyte apoptosis. The LAPW also showed more interstitial fibrosis than the LAA (7.49% +/- 3.34% versus 2.80% +/- 1.35%; P < .0001). Ultrastructural examination confirmed the presence of myocyte myocytolysis in the perinuclear area and showed changes in mitochondrial shape. In conclusion, the LAPW in patients with chronic AF related to mitral valve disease seems to be a particular anatomical site in which major myocyte and interstitial changes are concentrated, whereas the LAA is more protected. This remodeling may increase the heterogeneity of LAPW electrical conduction, thus confirming this location as an elective target for the ablation treatment of AF.