No abstract

DICER1 is an endoribonuclease central to the generation of microRNAs (miRNAs) and short interfering RNAs (siRNAs). Germline mutations in DICER1 have been associated with a pleiotropic tumour predisposition syndrome and Wilms tumour (WT) is a rare manifestation of this syndrome. Three WTs, each in a child with a deleterious germline DICER1 mutation, were screened for somatic DICER1 mutations and were found to bear specific mutations in either the RNase IIIa (n = 1) or the RNase IIIb domain (n = 2). In the two latter cases, we demonstrate that the germline and somatic DICER1 mutations were in trans, suggesting that the two-hit hypothesis of tumour formation applies for these examples of WT. Among 191 apparently sporadic WTs, we identified five different missense or deletion somatic DICER1 mutations (2.6%) in four individual WTs; one tumour had two very likely deleterious somatic mutations in trans in the RNase IIIb domain (c.5438A>G and c.5452G>A). In vitro studies of two somatic single-base substitutions (c.5429A>G and c.5438A>G) demonstrated exon 25 skipping from the transcript, a phenomenon not previously reported in DICER1. Further we show that DICER1 transcripts lacking exon 25 can be translated in vitro. This study has demonstrated that a subset of WTs exhibits two 'hits' in DICER1, suggesting that these mutations could be key events in the pathogenesis of these tumours.No conflicts of interest were declared. pleuropulmonary blastoma (PPB) syndrome (OMIM 601200) [7,8]. Several genes have been identified as being somatically mutated in WT, including WT1 , CTNNB1 , IGF2 , TP53 , WTX , DIS3L2 , FBXW7 and MYCN [5,9]. There are overlapping distributions of molecular abnormalities at 11p15, WTX , WT1 and CTNNB1 in WT [9,10], but other genes could be contributing to the aetiology of WT [3,[11][12][13]. WT histopathology is heterogeneous and tumours associated with different types of nephrogenic rests and histologies tend to show different underlying genetic changes [14,15]. A revised model for WT ontogeny takes into account genetic data (WT1 status, 11p15 imprint control region 1 methylation status, gene expression patterns of other genes) and histological data [14]. Nevertheless, each WT is thought to be of monoclonal origin [16].

Despite almost 30 years of clinical cancer research, the true impact of second and subsequent lines of chemotherapy on the outcome of metastatic breast cancer patients, especially on the duration of survival, is still unknown. In the virtually incurable metastatic setting, issues like quality of life and patients' preferences gain particular relevance. At the turn of the century, in-depth rethinking of the design of clinical trials run in this challenging disease setting appears to be warranted.