Progesterone and Wnt4 control mammary stem cells via myoepithelial crosstalk.

Ovarian hormones increase breast cancer risk by poorly understood mechanisms. We assess the role of progesterone on global stem cell function by serially transplanting mouse mammary epithelia. Progesterone receptor (PR) deletion severely reduces the regeneration capacity of the mammary epithelium. The PR target, receptor activator of Nf-κB ligand (RANKL), is not required for this function, and the deletion of Wnt4 reduces the mammary regeneration capacity even more than PR ablation. A fluorescent reporter reveals so far undetected perinatal Wnt4 expression that is independent of hormone signaling. Pubertal and adult Wnt4 expression is specific to PR+ luminal cells and requires intact PR signaling. Conditional deletion of Wnt4 reveals that this early, previously unappreciated, Wnt4 expression is functionally important. We provide genetic evidence that canonical Wnt signaling in the myoepithelium required PR and Wnt4, whereas the canonical Wnt signaling activities observed in the embryonic mammary bud and in the stroma around terminal end buds are independent of Wnt4. Thus, progesterone and Wnt4 control stem cell function through a luminal-myoepithelial crosstalk with Wnt4 acting independent of PR perinatally.

MOM1 and Pol-IV/V interactions regulate the intensity and specificity of transcriptional gene silencing.

It is commonly observed that onset or release of transcriptional gene silencing (TGS) correlates with alteration of repressive epigenetic marks. The TGS regulator MOM1 in Arabidopsis is exceptional since it regulates transcription in intermediate heterochromatin with only minor changes in epigenetic marks. We have isolated an enhancer of the mom1 mutation that points towards regulatory interplay between MOM1 and RNA polymerase-V (Pol-V). Pol-V transcribes heterochromatic loci, which seems to be required for maintenance of their silencing; however, it is still not clear how Pol-V is targeted to heterochromatin. We now provide evidence that Pol-V is required for MOM1-mediated suppression of transcription at a subset of its chromosomal targets. Thus, Pol-V genetically interacts with MOM1 in the control of gene silencing. Interestingly, functional cooperation of MOM1 and Pol-V not only broadens the range of the controlled loci in comparison to each individual factor, but also determines the degree of TGS.

ID4 regulates mammary gland development by suppressing p38MAPK activity.

The ID family of helix-loop-helix proteins regulates cell proliferation and differentiation in many different developmental pathways, but the functions of ID4 in mammary development are unknown. We report that mouse Id4 is expressed in cap cells, basal cells and in a subset of luminal epithelial cells, and that its targeted deletion impairs ductal expansion and branching morphogenesis as well as cell proliferation induced by estrogen and/or progesterone. We discover that p38MAPK is activated in Id4-null mammary cells. p38MAPK is also activated following siRNA-mediated Id4 knockdown in transformed mammary cells. This p38MAPK activation is required for the reduced proliferation and increased apoptosis in Id4-ablated mammary glands. Therefore, ID4 promotes mammary gland development by suppressing p38MAPK activity.

Two distinct mechanisms underlie progesterone-induced proliferation in the mammary gland.

The mouse mammary gland develops postnatally under the control of female reproductive hormones. Estrogens and progesterone trigger morphogenesis by poorly understood mechanisms acting on a subset of mammary epithelial cells (MECs) that express their cognate receptors, estrogen receptor alpha (ERalpha) and progesterone receptor (PR). Here, we show that in the adult female, progesterone drives proliferation of MECs in two waves. The first, small wave, encompasses PR(+) cells and requires cyclin D1, the second, large wave, comprises mostly PR(-) cells and relies on the tumor necrosis factor (TNF) family member, receptor activator of NF-kappaB-ligand (RANKL). RANKL elicits proliferation by a paracrine mechanism. Ablation of RANKL in the mammary epithelium blocks progesterone-induced morphogenesis, and ectopic expression of RANKL in MECs completely rescues the PR(-/-) phenotype. Systemic administration of RANKL triggers proliferation in the absence of PR signaling, and injection of a RANK signaling inhibitor interferes with progesterone-induced proliferation. Thus, progesterone elicits proliferation by a cell-intrinsic and a, more important, paracrine mechanism.

Estimated Costs of the Ipilimumab-Nivolumab Therapy and Related Adverse Events in Metastatic Melanoma.

Combined ipilimumab and nivolumab significantly improve outcomes in metastatic melanoma patients but bear an important financial impact on the healthcare system. Here, we analyze the treatment costs, focusing on irAE. We conducted a retrospective analysis of 62 melanoma patients treated with ipilimumab-nivolumab at the Lausanne University Hospital between 1 June 2016 and 31 August 2019. The frequency of irAEs and outcomes were evaluated. All melanoma-specific costs were analyzed from the first ipilimumab-nivolumab dose until the therapy given subsequently or death. A total of 54/62 (87%) patients presented at least one irAE, and 31/62 (50%) presented a grade 3-4 irAE. The majority of patients who had a complete response 12/14 (86%) and 21/28 (75%) of overall responders presented a grade 3-4 toxicity, and there were no responses in patients without toxicity. Toxicity costs represented only 3% of the total expenses per patient. The most significant contributions were medication costs (44%) and disease costs (39%), mainly disease-related hospitalization costs, not toxicity-related. Patients with a complete response had the lowest global median cost per week of follow up (EUR 2425) and patients who had progressive disease (PD), the highest one (EUR 8325). Except for one patient who had a Grade 5 toxicity (EUR 6043/week), we observe that less severe toxicity grades (EUR 9383/week for Grade 1), or even the absence of toxicity (EUR 9922/week), are associated with higher median costs per week (vs. EUR 3266/week for Grade 4 and EUR 2850/week for Grade 3). The cost of toxicities was unexpectedly low compared to the total costs, especially medication costs. Patients with higher toxicity grades had better outcomes and lower total costs due to treatment discontinuation.

Divergent evolution of CHD3 proteins resulted in MOM1 refining epigenetic control in vascular plants.

Arabidopsis MOM1 is required for the heritable maintenance of transcriptional gene silencing (TGS). Unlike many other silencing factors, depletion of MOM1 evokes transcription at selected loci without major changes in DNA methylation or histone modification. These loci retain unusual, bivalent chromatin properties, intermediate to both euchromatin and heterochromatin. The structure of MOM1 previously suggested an integral nuclear membrane protein with chromatin-remodeling and actin-binding activities. Unexpected results presented here challenge these presumed MOM1 activities and demonstrate that less than 13% of MOM1 sequence is necessary and sufficient for TGS maintenance. This active sequence encompasses a novel Conserved MOM1 Motif 2 (CMM2). The high conservation suggests that CMM2 has been the subject of strong evolutionary pressure. The replacement of Arabidopsis CMM2 by a poplar motif reveals its functional conservation. Interspecies comparison suggests that MOM1 proteins emerged at the origin of vascular plants through neo-functionalization of the ubiquitous eukaryotic CHD3 chromatin remodeling factors. Interestingly, despite the divergent evolution of CHD3 and MOM1, we observed functional cooperation in epigenetic control involving unrelated protein motifs and thus probably diverse mechanisms.

The secreted protease Adamts18 links hormone action to activation of the mammary stem cell niche.

Estrogens and progesterone control breast development and carcinogenesis via their cognate receptors expressed in a subset of luminal cells in the mammary epithelium. How they control the extracellular matrix, important to breast physiology and tumorigenesis, remains unclear. Here we report that both hormones induce the secreted protease Adamts18 in myoepithelial cells by controlling Wnt4 expression with consequent paracrine canonical Wnt signaling activation. Adamts18 is required for stem cell activation, has multiple binding partners in the basement membrane and interacts genetically with the basal membrane-specific proteoglycan, Col18a1, pointing to the basement membrane as part of the stem cell niche. In vitro, ADAMTS18 cleaves fibronectin; in vivo, Adamts18 deletion causes increased collagen deposition during puberty, which results in impaired Hippo signaling and reduced Fgfr2 expression both of which control stem cell function. Thus, Adamts18 links luminal hormone receptor signaling to basement membrane remodeling and stem cell activation.

Adamts18 deletion results in distinct developmental defects and provides a model for congenital disorders of lens, lung, and female reproductive tract development.

The ADAMTS family comprises 19 secreted metalloproteinases that cleave extracellular matrix components and have diverse functions in numerous disease and physiological contexts. A number of them remain 'orphan' proteases and among them is ADAMTS18, which has been implicated in developmental eye disorders, platelet function and various malignancies. To assess in vivo function of ADAMTS18, we generated a mouse strain with inactivated Adamts18 alleles. In the C57Bl6/Ola background, Adamts18-deficient mice are born in a normal Mendelian ratio, and are viable but show a transient growth delay. Histological examination revealed a 100% penetrant eye defect resulting from leakage of lens material through the lens capsule occurring at embryonic day (E)13.5, when the lens grows rapidly. Adamts18-deficient lungs showed altered bronchiolar branching. Fifty percent of mutant females are infertile because of vaginal obstruction due to either a dorsoventral vaginal septum or imperforate vagina. The incidence of ovarian rete is increased in the mutant mouse strain. Thus, Adamts18 is essential in the development of distinct tissues and the new mouse strain is likely to be useful for investigating ADAMTS18 function in human disease, particularly in the contexts of infertility and carcinogenesis.

Transgenerational stability of the Arabidopsis epigenome is coordinated by CG methylation.

Maintenance of CG methylation ((m)CG) patterns is essential for chromatin-mediated epigenetic regulation of transcription in plants and mammals. However, functional links between (m)CG and other epigenetic mechanisms in vivo remain obscure. Using successive generations of an Arabidopsis thaliana mutant deficient in maintaining (m)CG, we find that (m)CG loss triggers genome-wide activation of alternative epigenetic mechanisms. However, these mechanisms, which involve RNA-directed DNA methylation, inhibiting expression of DNA demethylases, and retargeting of histone H3K9 methylation, act in a stochastic and uncoordinated fashion. As a result, new and aberrant epigenetic patterns are progressively formed over several plant generations in the absence of (m)CG. Interestingly, the unconventional redistribution of epigenetic marks is necessary to "rescue" the loss of (m)CG, since mutant plants impaired in rescue activities are severely dwarfed and sterile. Our results provide evidence that (m)CG is a central coordinator of epigenetic memory that secures stable transgenerational inheritance in plants.