Fig. 2

Bcl-3^−/− mammary epithelial organoids demonstrate retarded bud formation and defective collagen I invasion in 3D cultures. a Bcl-3^−/− and WT mammary organoids were isolated as described in Methods, seeded into Cultrex BME and allowed to grow for 10 days prior to imaging. Bars are 400 µm. b Graph depicting average number of organoid buds produced by mammary epithelium from WT and bcl-3^−/− mice after 10 days in basement membrane 3D cultures. Statistical analysis; unpaired t test. c Comparison of 10 day organoids from WT and bcl-3^−/− mice that lacked bud formation. Results of the paired t test, n = 3 mice per genotype. All bars are S.E.M. d Immunofluorescence for Bcl-3 on frozen sections of WT and bcl-3^−/− mammary organoids grown in Cultrex BME for 10 days and processed as described in Methods. DAPI was used to identify nuclei. e Mammary organoids were seeded into 3 mg/ml collagen I gels, and images were collected at the indicated days of culture. All images acquired with a 20× objective. f Graph showing number of organoids seeded relative to organoid numbers that produced continuous protrusive invasion at day 8 of culture. g qRT-PCR to detect the indicated invasion-associated genes in organoid RNA from 3 mice per genotype cultured for 8 days in collagen I. **p < 0.01; ***p < 0.001, unpaired t test