Milea Timbergen

64 Results No difference in AXIN2, CCND1 and DKK1 expression between wild-type and CTNNB1 mutated desmoids To examine whether different CTNNB1 mutations in desmoid tumours cause differential expression of Wnt target genes, the transcript levels of AXIN2 , CCND1 and DKK1 were determined by RT-PCR. In total, 64 FFPE samples from the Dutch cohort were available for the RT-PCR analysis. The cohort included 23 males (35.9%) and 41 females (64.1%). Mutational status was as follows; 11 tumours (17.2 %) were WT for exon 3, 38 (59.4%) tumours harboured a T41A mutation, 12 (18.8%) tumours harboured a S45F mutation and 3 (4.7%) tumours harboured a S45P mutation. Because of the low prevalence, the desmoids with the S45P mutation were not included in the RT-PCR analysis leaving a total of 61 patients. The tumour and patient characteristics are summarized in Table 1. The relative expression values of AXIN2 , CCND1 and DDK1 transcripts were measured and the median expression levels and the maximum IQR were calculated (Table 2). A Kruskal-Wallis test shows that the mean rank of the relative expression levels was not statistically significantly different between groups for AXIN2 and DKK1 (Table 2). The mean rank of the relative expression level for CCND1 showed a significant difference between groups, however failed significance after Bonferroni correction for multiple testing between mutation groups (Table 2). A dot plot depicting the relative expression levels of individual samples of AXIN2, CCND1 and DKK1 is shown in Figure 1. Table 2. Relative expression values of Wnt target genes AXIN2 , CCND1 and DKK1 for the Dutch and French subgroups (tumours harbouring a T41A, S45F or wild-type CTNNB1 gene mutation A. Dutch cohort, subgroup data (n = 61) a,b Median (IQR) p-value c AXIN2 1.48 (1.12) 0.273 CCND1 0.61 (0.86) 0.029 d DKK1 0.02 (0.04) 0.319 B. French cohort, subgroup data (n = 93) a Median using log2 transformed data (IQR) p-value c AXIN2 (224498_x_at) 4.80 (1.48) 0.058 CCND1 ( 208711_s_at) 5.89 (0.80) 0.486 DKK1 (204602_at) 5.20 (1.17) 0.652 a T41A, S45F and wild-type CTNNB1 tumours included; b compared to house keeper gene Peptidylprolyl Isomerase A; c calculated p-values using the Kruskal-Wallis test; d non-significant after Bonferroni correction for multiple testing. IQR, interquartile range; AXIN2, Axin 2; CCND1, Cyclin D1; DKK1, Dickkopf1; CI, confidence interval 3