XBP1 and breast cancer: Indeed, genes XBP1, AGR2, and CA12 which yielded high posterior selection probabilities as well as the strongest negative projection coefficients in Factor 1 (Fig. 4E, Supplementary Table S1) for the Estrogen Response (Late) pathway were all associated with a breast cancer Steroid Responsiveness (SR) module that indicates functional steroid response (Fredlund et al. 2012).