Figure 1 Immunohistochemical staining of HB using an antibody to β-catenin. (a) Cytoplasmic staining of βselleck compound -catenin in hepatoblastoma. (b) Nuclear and cytoplasmic accumulation of 17DMAG order β-catenin in hepatoblastoma.

(c) Normal staining of the liver cell membrane using an antibody to β-catenin. CTNNB1 mutation analysis of hepatoblastomas from SIOPEL clinical trial To identify CTNNB1 mutations we extracted total RNA from corresponding tissue cores of hepatoblastoma. A 150 pb region of the β-catenin regulatory region of exon 3 of the CTNNB1 gene (codons

32-45) was amplified successfully by RT-PCR in 92 of the samples. Lack of amplification in 6 samples may be due to deletion of exon 3 of CTNNB1. We attempted to amplify a region spanning exon 2 to exon 4 in these 6 samples but were unsuccessful. Therefore our estimation of samples containing deletions may be inaccurate. We identified 11 different point mutations in 14 of 98 samples (15%) (Table 1). These are all missense mutations affecting phosphorylation sites Pitavastatin mw in the regulatory region of the gene and have been previously reported [17, 38]. The mutations found, resulted in the following changes at the protein level; 32D > N, 32D > Y, 32D > V, 32D > A, 33S > P, 33S > C, 34G > R, 34G > E, 34G > V, 35I > P, 35I > S, 37S > Y. One HB patient (CCRG 64) showed the same sequence variation (missense 32D > V) in both diagnostic and post chemotherapy tumour samples. RNA from adjacent normal tissue was also analysed from

62 cases NADPH-cytochrome-c2 reductase including nine tumours that harboured mutations. All of these samples displayed wild type CTNNB1 showing that the mutations found were somatic variants (results not shown). The frequency of CTNNB1 mutations (14/98) and possible deletions (6/98) in our cohort was significantly lower than the frequency of aberrant expression of β-catenin protein and statistical analysis shows no correlation between aberrant β-catenin accumulation and gene mutation/deletion. This prompted us to investigate alternative pathways of β-catenin activation in hepatoblastomas in our patient cohort. Table 1 Histologic type and subtype, β-catenin and Y654 β-catenin IHC and CTNNB1 gene status of hepatoblastomas with mutations.