TI - Results and Discussion The LRP5Delta receptor is expressed in breast carcinoma . AB - To investigate whether the internally truncated LRP5Delta666-809 receptor ( LRP5Delta ) was expressed in breast carcinoma we initially analyzed nineteen breast cancer specimens ( T1-T19 ) that had been randomly selected in a previous study regarding 25-hydroxyvitamin D3 1alpha-hydroxylase [32] . RT-PCR analysis , using primers located in exons 9 and 13 of LRP5 [26] , revealed expression of LRP5Delta in 15 out of 17 ductal breast carcinoma and 1 out of 2 lobular carcinoma ( Figure 1A ) . Thus , 84% of the analyzed tumors expressed LRP5Delta . Normal LRP5 ( LRP5wt ) transcripts were seen in all tumors , and in normal breast tissue specimens ( N1-N4 ) as anticipated ( Figure 1A ) [26] . Immunoprecipitation and Western blot analysis confirmed expression of LRP5wt and LRP5Delta in the tumors ( Figure 1B ) . In order to relate accumulation of beta-catenin to expression of LRP5Delta , Western blotting analysis was done on cryosections of the tumor material , including two normal breast tissue specimens . The sixteen tumors with LRP5Delta showed increased accumulation of non-PHOSphorylated active beta-catenin when compared to the normal breast tissues , and the tumors expressing LRP5wt only ( Thr3 , Thr9 , Thr11 ) showed similar relative amounts ( Figure 1C ) . Thus , correlation of LRP5Delta expression and aberrant accumulation of non-PHOSphorylated active beta-catenin was observed in these breast tumors . Stabilizing mutation in beta-catenin exon 3 was not found in the nineteen breast carcinomas ( not shown ) . Encouraged by the above results we then screened a commercially available cDNA panel of 96 breast tissue specimens that covered eight cancer stages . LRP5wt and LRP5Delta was observed in 79 out of 95 ( 83% ) samples ( Table 1 ) . The remaining samples expressed only LRP5wt and one sample was negative . LRP5Delta was detected in all disease stages including carcinoma in situ and metastases . Thus , expression of LRP5Delta was very common in carcinoma of the breast and may be an early event during cancer progression .