C57BL/6 Mouse Primary Mammary Epithelial Cells

L-arginine Promotes Cell Proliferation by Up-Regulating the Expression of Proliferation-Related Proteins

Amino acids have been shown to affect the development of mammary gland (MG). However, it is unclear whether L-arginine promotes the development of pubertal MG. Therefore, Ge's team aims to explore the effect of L-arginine on the development of MG in pubertal mice.

To investigate its internal mechanism of action, they used mouse mammary epithelial cells (mMECs) line. The results revealed that L-arginine can significantly promote the development of MG. Next, they investigated the effect of various concentrations of L-arginine (0, 0.2, 0.4, 0.6, 0.8 and 1.0 mM) on the proliferation of mMECs. The results showed that mMECs had the most obvious effect on their proliferation after being treated with 0.4 mM L-arginine (Fig. 1a). Furthermore, L-arginine significantly increased the protein levels of proliferation-related proteins such as Cyclin D1/D3/A1 and PCNA in mMECs (Fig. 1b-f). The final results indicate that L-arginine promotes the proliferation of mMECs and increases the levels of proliferation-related proteins.

BMP4 Differentiates Mammary Epithelial Cells into an Acinar Structure in 3D Cell Culture

Basal-like triple-negative breast cancer (TNBC) is characterized by an aggressive phenotype with poor prognosis, relapse, and drug resistance mediated by a high cancer stem-cell (CSC) burden. The mechanisms sustaining the stemness feature in this breast cancer subtype are not well understood. Here, Yan et al. asked how TGFβ family ligands network to control CSC abundance in TNBC, and whether opposing factors could be therapeutically exploited.

They evaluated whether BMP4 could induce the formation of mammary acinar structures in normal mouse mammary epithelial cells. They performed ex vivo acini morphogenesis assays in primary mammary epithelial cells isolated from female virgin mice. As seen in Fig. 2a, BMP4 strongly induced the formation of organized mammary acini with well-established apical/basal polarity (as indicated by the apical localization of ZO-1 and basal/lateral localization of E-cadherin) compared to the control and TGFβ-stimulated cells that did not form such organized acini. Interestingly, TGFβ strongly antagonized the effects of BMP4 on acinar morphogenesis. They then quantified the number of acini under different conditions. As shown in Fig. 2b, BMP4 significantly increased the efficiency of acinar formation, an effect that was antagonized by TGFβ. These data point to BMP4 as a strong differentiation factor in normal mammary epithelial cells that efficiently promotes the formation of well-organized 3D acinar structures, and TGFβ can efficiently antagonize this BMP4 activity.