To further explore whether the proportions of epithelial cells in mammary tumors were affected by Frmd8 loss, we subset and reidentified four epithelial cell clusters (Valdés-Mora et al., 2021), including alveolar progenitor (Avp), basal (Bsl), hormone-sensing differentiated (Hsd), and luminal progenitor (Lp) epithelial cells (Figure 2E). Here, CHST3 is linked to breast cancer.