RB1 gene expression has been reported to be upregulated in colorectal carcinomas (CRC) at both the mRNA and protein levels when compared to normal colonic mucosa. However, allelic loss at the genomic level has been detected in CRC with widely differing frequencies ranging from 11.5% to 50%. To determine whether there is indeed a correlation between RB1 allelic imbalance (AI) and expression, a consecutive series of 55 CRC from Singapore patients were analysed by microsatellite analysis, real-time RT-PCR and immunohistochemistry. Microsatellite analysis using 3 RB1 intragenic microsatellite markers and 2 markers flanking RB1 detected AI in 32.7% (18/55) of the cases, in at least 1 locus. The highest AI frequency (22.9%) was observed at the microsatellite marker D13S137 (Cu13), which maps 5 cM distal to RB1. AI was present in both early and late Dukes stages. Real-time RT-PCR revealed that all 40 cases analysed expressed RB1 mRNA, with mRNA overexpression in 37.5% (15/40) and pRB protein expression in 88.2% (30/ 34) of cases. Notably, a statistically significant correlation was found between AI of RB1 and mRNA overexpression of RB1 (p < 0.001, Fishers exact test). These findings provide evidence that despite AI, RB1 expression is not abrogated. Thus, our data suggests that RB1 may play a role in colorectal tumorigenesis through functional regulation of the transcript and protein rather than through its tumour suppressor role by gene inactivation. ' 2006 Wiley-Liss, Inc.Key words: RB1; colorectal cancer; allelic imbalance; expressionThe retinoblastoma gene, RB1, is a well-known tumour suppressor gene that encodes a nucleoprotein (pRB) with a critical role in cell cycle regulation, proliferation, differentiation and apoptosis. Numerous studies have shown frequent loss of RB1 function and either low or no pRb expression in different tumour types, such as pituitary adenomas, 1 glioblastomas, 2,3 hepatocellular carcinomas 4 and sporadic retinoblastomas. 5 In contrast, RB1 gene expression has been reported to be upregulated in colorectal carcinomas (CRC) at both the mRNA and protein levels when compared to normal colonic mucosa.6-13 Consistent with this increased expression, RB1 transcripts and pRb are not truncated or absent in colorectal cancers, suggesting that Rb is functional in CRC. 12,14 At the genomic level, allelic loss detected by loss of heterozygosity (LOH) has also been reported in the RB1 region in CRC with widely differing frequencies ranging from 11.5% 15 to as high as 50% of cases studied.16,17 These differences in frequencies may be because LOH assays actually determine allelic imbalance which may indicate either loss or gain. Increased allelic copy number at polymorphic loci of RB1 has also been documented by densitometric comparisons of Southern blots in 32% of colorectal tumours, 18 as well as by fluorescence in situ hybridization analysis in 44% of colorectal adenomas. 19 The presence of RB1 allelic loss would suggest that its expression would be decreased, contradictory to previous expression stud...

Neurofibromatosis type 1 (NF1) is a genetic disorder characterized by the development of multiple neurofibromas, cafe‐au‐lait spots, and Lisch nodules. Individuals with NF1 are at increased risk of developing various tumors, such as malignant peripheral nerve sheath tumor (MPNST), pheochromocytoma, leukemia, glioma, rhabdomyosarcoma, and breast cancer. Here, we describe the exome sequencing of breast cancer, MPNST, and neurofibroma from a patient with NF1. We identified a germline mutation in the NF1 gene which resulted in conversion of leucine to proline at amino acid position 847. In addition, we showed independent somatic NF1 mutations in all the three tumors (frameshift insertion in breast cancer (p.A985fs), missense mutation in MPNST (p.G23R), and inframe deletion in dermal neurofibroma (p.L1876del‐Inf)), indicating that a second hit in NF1 resulting in the loss of function could be important for tumor formation. Each tumor had a distinct genomic profile with mutually exclusive mutations in different genes. Copy number analysis revealed multiple copy number alterations in the breast cancer and the MPNST, but not the benign neurofibroma. Germline loss of chromosome 6q22.33, which harbors two potential tumor suppressor genes, PTPRK and LAMA2, was also identified; this may increase tumor predisposition further. In the background of NF1 syndrome, although second‐hit NF1 mutation is critical in tumorigenesis, different additional mutations are required to drive the formation of different tumors.

Correspondencewere intervening cannot be answered at present. The absolute proof sults can be obtained with extensive sample preparation and hybridization. of the etiologic role of any microorganism in respiratory infections in very difficult to produce, since the presence of the microorganism in the inflammatory focus can only exceptionally be docu-In our study, we could conclude that M. pneumoniae was responsible for 13.3% of lower respiratory tract infections (bronchopneumonia and lobar pneumonia) in children, whereas it was found in only 2.1% of all other clinical presentations. This difference is Reference significant (P õ .01). Although little is known about the prevalence 1. Tjhie JHT, Savelkoul PHM, Vandenbroucke-Grauls CMJE. Polymerase

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