Pygo2 expands mammary progenitor cells by facilitating histone H3 K4 methylation

Recent studies have unequivocally identified multipotent stem/progenitor cells in mammary glands, offering a tractable model system to unravel genetic and epigenetic regulation of epithelial stem/progenitor cell development and homeostasis. In this study, we show that Pygo2, a member of an evolutionarily conserved family of plant homeo domain–containing proteins, is expressed in embryonic and postnatal mammary progenitor cells. Pygo2 deficiency, which is achieved by complete or epithelia-specific gene ablation in mice, results in defective mammary morphogenesis and regeneration accompanied by severely compromised expansive self-renewal of epithelial progenitor cells. Pygo2 converges with Wnt/β-catenin signaling on progenitor cell regulation and cell cycle gene expression, and loss of epithelial Pygo2 completely rescues β-catenin–induced mammary outgrowth. We further describe a novel molecular function of Pygo2 that is required for mammary progenitor cell expansion, which is to facilitate K4 trimethylation of histone H3, both globally and at Wnt/β-catenin target loci, via direct binding to K4-methyl histone H3 and recruiting histone H3 K4 methyltransferase complexes

Targeting IL-17B–IL-17RB signaling with an anti–IL-17RB antibody blocks pancreatic cancer metastasis by silencing multiple chemokines

Pancreatic cancer has an extremely high mortality rate due to its aggressive metastatic nature. Resolving the underlying mechanisms will be crucial for treatment. Here, we found that overexpression of IL-17B receptor (IL-17RB) strongly correlated with postoperative metastasis and inversely correlated with progression-free survival in pancreatic cancer patients. Consistently, results from ex vivo experiments further validated that IL-17RB and its ligand, IL-17B, plays an essential role in pancreatic cancer metastasis and malignancy. Signals from IL-17B–IL-17RB activated CCL20/CXCL1/IL-8/TFF1 chemokine expressions via the ERK1/2 pathway to promote cancer cell invasion, macrophage and endothelial cell recruitment at primary sites, and cancer cell survival at distant organs. Treatment with a newly derived monoclonal antibody against IL-17RB blocked tumor metastasis and promoted survival in a mouse xenograft model. These findings not only illustrate a key mechanism underlying the highly aggressive characteristics of pancreatic cancer but also provide a practical approach to tackle this disease

Localization and dynamic relocalization of mammalian Rad52 during the cell cycle and in response to DNA damage

AbstractThe importance of RAD52 in establishment and maintenance of genomic structure has been established by genetic experiments in the yeast Saccharomyces cerevisiae, where mutation of RAD52 has been shown to diminish DNA repair and recombination of a variety of markers, including the rDNA [1–3]. Biochemical analysis has shown that yeast and mammalian Rad52 proteins have some identical functions in vitro[4–6], but targeted deletion of Rad52 in vertebrates has little effect on repair and recombination [7,8]. These results raise the question of whether mammalian Rad52 does indeed function in recombination and/or repair. Here we show that Rad52 is distributed throughout the nucleoplasm in actively cycling mammalian cells and is localized specifically to the nucleoli in S phase. In response to ionizing radiation, Rad52 relocalizes to form distinctive foci which are distributed throughout the nucleus and which colocalize with Rad50 foci in the DNA damage response. These data suggest that rDNA recombination and DNA repair are functions shared by mammalian Rad52 and its S. cerevisiae homolog, and provide evidence for the coordinated action of Rad50 and Rad52 in DNA repair

Breast Cancer Stem Cells and Tumor Suppressor Genes

Studies of breast cancer stem cells are in their infancy and many fundamental questions have yet to be fully addressed. The molecular distinction between normal and cancerous breast stem cells is not clear. While there have been recent breakthroughs in mouse mammary stem cells and lineage determination in mammary glands, little has been determined in human cells. Microarray analyses have provided molecular categorization of breast cancer. However, the cellular origin of different types of breast cancer is largely unknown. In addition, the relationship between breast cancer stem cells and mammary progenitor cells has yet to be clarified. One of the key questions is how a normal mammary stem cell becomes a breast cancer stem cell. Importantly, the existence of different types of human breast cancers with distinct pathologic and molecular signatures suggests the possibility that different types of breast cancer stem cells may exist. Here, we aim to review the current evidence for the existence of different subtypes of breast cancer stem cells and provide further insight into how tumor suppressors might be involved in the initiation of breast cancer stem cells

Cep164 is a mediator protein required for the maintenance of genomic stability through modulation of MDC1, RPA, and CHK1

The activation of the ataxia telangiectasia mutated (ATM) and ATM/Rad3-related (ATR) kinases triggers a diverse cellular response including the initiation of DNA damage-induced cell cycle checkpoints. Mediator of DNA Damage Checkpoint protein, MDC1, and H2AX are chromatin remodeling factors required for the recruitment of DNA repair proteins to the DNA damage sites. We identified a novel mediator protein, Cep164 (KIAA1052), that interacts with both ATR and ATM. Cep164 is phosphorylated upon replication stress, ultraviolet radiation (UV), and ionizing radiation (IR). Ser186 of Cep164 is phosphorylated by ATR/ATM in vitro and in vivo. The phosphorylation of Ser186 is not affected by RPA knockdown but is severely hampered by MDC1 knockdown. siRNA-mediated silencing of Cep164 significantly reduces DNA damage-induced phosphorylation of RPA, H2AX, MDC1, CHK2, and CHK1, but not NBS1. Analyses of Cep164 knockdown cells demonstrate a critical role of Cep164 in G2/M checkpoint and nuclear divisions. These findings reveal that Cep164 is a key player in the DNA damage-activated signaling cascade

SMC1 is a downstream effector in the ATM/NBS1 branch of the human S-phase checkpoint

Structural maintenance of chromosomes (SMC) proteins (SMC1, SMC3) are evolutionarily conserved chromosomal proteins that are components of the cohesin complex, necessary for sister chromatid cohesion. These proteins may also function in DNA repair. Here we report that SMC1 is a component of the DNA damage response network that functions as an effector in the ATM/NBS1-dependent S-phase checkpoint pathway. SMC1 associates with BRCA1 and is phosphorylated in response to IR in an ATM- and NBS1-dependent manner. Using mass spectrometry, we established that ATM phosphorylates S957 and S966 of SMC1 in vivo. Phosphorylation of S957 and/or S966 of SMC1 is required for activation of the S-phase checkpoint in response to IR. We also discovered that the phosphorylation of NBS1 by ATM is required for the phosphorylation of SMC1, establishing the role of NBS1 as an adaptor in the ATM/NBS1/SMC1 pathway. The ATM/CHK2/CDC25A pathway is also involved in the S-phase checkpoint activation, but this pathway is intact in NBS cells. Our results indicate that the ATM/NBS1/SMC1 pathway is a separate branch of the S-phase checkpoint pathway, distinct from the ATM/CHK2/CDC25A branch. Therefore, this work establishes the ATM/NBS1/SMC1 branch, and provides a molecular basis for the S-phase checkpoint defect in NBS cells

Antitumor agents 279. Structure–activity relationship and in vivo studies of novel 2-(furan-2-yl)naphthalen-1-ol (FNO) analogs as potent and selective anti-breast cancer agents

In our ongoing modification study of neo-tanshinlactone (1), we discovered 2-(furan-2-yl)naphthalen-1-ol (FNO) derivatives 3 and 4 as a new class of anti-tumor agents. To explore structure-activity relationships (SAR) of this scaffold, 18 new analogs, 6–12 and 14–24, were designed and synthesized. The C11-esters 7 and 12 displayed broad anti-tumor activity (ED(50) 1.1–4.3 µg/mL against seven cancer cell lines), while C11-hydroxymethyl 14 showed unique selectivity against the SKBR-3 breast cancer cell line (ED(50) 0.73 µg/mL). Compounds 15 and 22 displayed potent and selective anti-breast tumor activity (ED(50) 1.7 and 0.85 µg/mL, respectively, against MDA-MB-231). The SAR results demonstrated that the substitutions from the ring-opened lactone ring C of 1 are critical to the anti-tumor potency as well as the apparent tumor-tissue type selectivity. Treatment with 3 in Brca1(f11/f11)p53(f5&6/f5&6)Cre(c) mice models significantly inhibited the proliferation of mammary epithelial cells and branching of mammary glands