cIAP2 Is an Independent Signaling and Survival Factor during Mammary Lactational Involution and Tumorigenesis

Cancer invasion and metastasis: Insights from murine pubertal mammary gland morphogenesis

Cancer invasion and metastasis accounts for the majority of cancer related mortality. A better understanding of the players that drive the aberrant invasion and migration of tumors cells will provide critical targets to inhibit metastasis. Postnatal pubertal mammary gland morphogenesis is characterized by highly proliferative, invasive, and migratory normal epithelial cells. Identifying the molecular regulators of pubertal gland development is a promising strategy since tumorigenesis and metastasis is postulated to be a consequence of aberrant reactivation of developmental stages. In this review, we summarize the pubertal morphogenesis regulators that are involved in cancer metastasis and revisit pubertal mammary gland transcriptome profiling to uncover both known and unknown metastasis genes. Our updated list of pubertal morphogenesis regulators shows that most are implicated in invasion and metastasis. This review highlights molecular linkages between development and metastasis and provides a guide for exploring novel metastatic drivers.

Culture Models to Investigate Mechanisms of Milk Production and Blood-Milk Barrier in Mammary Epithelial Cells: a Review and a Protocol

Mammary epithelial cells (MECs) are the only cell type that produces milk during lactation. MECs also form less-permeable tight junctions (TJs) to prevent the leakage of milk and blood components through the paracellular pathway (blood-milk barrier). Multiple factors that include hormones, cytokines, nutrition, and temperature regulate milk production and TJ formation in MECs. Multiple intracellular signaling pathways that positively and negatively regulate milk production and TJ formation have been reported. However, their regulatory mechanisms have not been fully elucidated. In addition, unidentified components that regulate milk production in MECs likely exist in foods, for example plants. Culture models of functional MECs that recapitulate milk production and TJs are useful tools for their study. Such models enable the elimination of indirect effects via cells other than MECs and allows for more detailed experimental conditions. However, culture models of MECs with inappropriate functionality may result in unphysiological reactions that never occur in lactating mammary glands in vivo. Here, I briefly review the physiological functions of alveolar MECs during lactation in vivo and culture models of MECs that feature milk production and less-permeable TJs, together with a protocol for establishment of MEC culture with functional TJ barrier and milk production capability using cell culture inserts.

Elucidating the pharmacological mechanism by which Si-Wu-Tang induces cellular senescence in breast cancer via multilevel data integration

Traditional Chinese medicine (TCM) is a promising strategy for effectively treating cancer by inducing cellular senescence with minimal side effects. Si-Wu-Tang (SWT) is a TCM composed of four herbs that is commonly used in China for the treatment of gynecological diseases; SWT can prevent breast cancer (BC), but the molecular mechanism by which SWT induces cellular senescence and its clinical application value remain unknown. We identified 335 differentially expressed genes (DEGs) in SWT-treated MCF-7 cells through Gene Expression Omnibus (GEO) dataset analysis. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses revealed the enrichment of biological processes and key signaling pathways including cellular senescence, the cell cycle, the MAPK signaling pathway, and the p53 signaling pathway. Additionally, SWT induced BC cell senescence by upregulating the expression of 33 aging/senescence-induced genes (ASIGs). According to LASSO regression analysis, NDRG1, ERRFI1, SOCS1, IRS2, IGFBP4, and BIRC3 levels were associated with BC prognosis and were used to develop risk scores. ERRFI1, SOCS1, IRS2, IGFBP4, and BIRC3 were identified as protective factors (P < 0.05, HR < 1), while NDRG1 was identified as a risk factor (P < 0.05, HR > 1). Notably, patients with low risk scores had increased senescence-associated secretory phenotypes (SASPs) and immune cell infiltration. Overall, we systematically integrated biological databases and biocomputational methods to reveal the mechanisms by which SWT induces senescence in breast cancer and its clinical value.

Multiple roles for Bcl-3 in mammary gland branching, stromal collagen invasion, involution and tumor pathology

BACKGROUND

The Bcl-3 protein is an atypical member of the inhibitor of -κB family that has dual roles as a transcriptional repressor and a coactivator for dimers of NF-κB p50 and p52. Bcl-3 is expressed in mammary adenocarcinomas and can promote tumorigenesis and survival signaling and has a key role in tumor metastasis. In this study, we have investigated the role of Bcl-3 in the normal mammary gland and impact on tumor pathology.

METHODS

We utilized bcl-3^-/- mice to study mammary gland structure in virgins and during gestation, lactation and early involution. Expression of involution-associated genes and proteins and putative Bcl-3 target genes was examined by qRT-PCR and immunoblot analysis. Cell autonomous branching morphogenesis and collagen I invasion properties of bcl-3^-/- organoids were tested in 3D hydrogel cultures. The role of Bcl-3 in tumorigenesis and tumor pathology was also assessed using a stochastic carcinogen-induced mammary tumor model.

RESULTS

Bcl-3^-/- mammary glands demonstrated reduced branching complexity in virgin and pregnant mice. This defect was recapitulated in vitro where significant defects in bud formation were observed in bcl-3^-/- mammary organoid cultures. Bcl-3^-/- organoids showed a striking defect in protrusive collective fibrillary collagen I invasion associated with reduced expression of Fzd1 and Twist2. Virgin and pregnant bcl-3^-/- glands showed increased apoptosis and rapid increases in lysosomal cell death and apoptosis after forced weaning compared to WT mice. Bcl-2 and Id3 are strongly induced in WT but not bcl-3^-/- glands in early involution. Tumors in WT mice were predominately adenocarcinomas with NF-κB activation, while bcl-3^-/- lesions were largely squamous lacking NF-κB and with low Bcl-2 expression.

CONCLUSIONS

Collectively, our results demonstrate that Bcl-3 has a key function in mammary gland branching morphogenesis, in part by regulation of genes involved in extracellular matrix invasion. Markedly reduced levels of pro-survival proteins expression in bcl-3 null compared to WT glands 24 h post-weaning indicate that Bcl-3 has a role in moderating the rate of early phase involution. Lastly, a reduced incidence of bcl-3^-/- mammary adenocarcinomas versus squamous lesions indicates that Bcl-3 supports the progression of epithelial but not metaplastic cancers.

MPA/DMBA-driven mammary carcinomas

The polycyclic aromatic hydrocarbon 7,12-dimethylbenz[a]anthracene (DMBA, D) administered per os to wild-type female mice bearing slow-release medroxyprogesterone (MPA, M) pellets s.c. drives the formation of mammary carcinomas that recapitulate numerous immunobiological features of human luminal B breast cancer. In particular, M/D-driven mammary carcinomas established in immunocompetent C57BL/6 female mice (1) express hormone receptors, (2) emerge by evading natural immunosurveillance and hence display a scarce immune infiltrate largely polarized toward immunosuppression, (3) exhibit exquisite sensitivity to CDK4/CDK6 inhibitors, and (4) are largely resistant to immunotherapy with immune checkpoint blockers targeting PD-1. Thus, M/D-driven mammary carcinomas evolving in immunocompetent female mice stand out as a privileged preclinical platform for the study of luminal B breast cancer. Here, we provide a detailed protocol for the establishment of M/D-driven mammary carcinomas in wild-type C57BL/6 female mice. This protocol can be easily adapted to generate M/D-driven mammary carcinomas in female mice with most genetic backgrounds (including genetically-engineered mice).