Based on the experimental work presented, such a conclusion should be taken with caution due to the simple fact that three of the four claudin-low tumor cell lines used in this study carry mutations ...in KRAS (MDA-MB-231) and HRAS (SUM159PT, Hs578T) 4. ...all three cell lines have mutations in RAS effector pathways. Despite gene expression data from human tumors and experimental evidence using genetic models that support important roles of oncogenic RAS/MAPK signaling in mammary cancer initiation and progression, the importance of this pathway is often diminished by comments about the infrequent occurrence of RAS mutations in primary human breast cancers. ...the specific upregulation of NRP1 in claudin-low breast cancer and its potential role in RTK signaling in the new report by Tang et al. might be important, but the presence of multiple driver mutations within the pathway of the particular cellular models must be taken into consideration to accurately assess the contribution of NRP1 as a signaling modulator for RAS and MAP kinases and the cellular characteristics that they instigate.
Pancreatic ductal adenocarcinoma (PDA) has a dismal prognosis and insights into both disease etiology and targeted intervention are needed. A total of 109 micro-dissected PDA cases were subjected to ...whole-exome sequencing. Microdissection enriches tumour cellularity and enhances mutation calling. Here we show that environmental stress and alterations in DNA repair genes associate with distinct mutation spectra. Copy number alterations target multiple tumour suppressive/oncogenic loci; however, amplification of MYC is uniquely associated with poor outcome and adenosquamous subtype. We identify multiple novel mutated genes in PDA, with select genes harbouring prognostic significance. RBM10 mutations associate with longer survival in spite of histological features of aggressive disease. KRAS mutations are observed in >90% of cases, but codon Q61 alleles are selectively associated with improved survival. Oncogenic BRAF mutations are mutually exclusive with KRAS and define sensitivity to vemurafenib in PDA models. High-frequency alterations in Wnt signalling, chromatin remodelling, Hedgehog signalling, DNA repair and cell cycle processes are observed. Together, these data delineate new genetic diversity of PDA and provide insights into prognostic determinants and therapeutic targets.
Jak2, a member of the Janus kinase family of nonreceptor protein tyrosine kinases, is activated in response to a variety of cytokines, and functions in survival and proliferation of cells. An ...activating JAK2V617F mutation has been found in most patients with myeloproliferative neoplasms, and patients treated with Jak2 inhibitors show significant hematopoietic toxicities. However, the role of Jak2 in adult hematopoietic stem cells (HSCs) has not been clearly elucidated. Using a conditional Jak2 knockout allele, we have found that Jak2 deletion results in rapid loss of HSCs/progenitors leading to bone marrow failure and early lethality in adult mice. Jak2 deficiency causes marked impairment in HSC function, and the mutant HSCs are severely defective in reconstituting hematopoiesis in recipient animals. Jak2 deficiency also causes significant apoptosis and loss of quiescence in HSC-enriched LSK (Lin(-)Sca-1(+)c-Kit(+)) cells. Jak2-deficient LSK cells exhibit elevated reactive oxygen species levels and enhanced p38 MAPK activation. Mutant LSK cells also show defective Stat5, Erk, and Akt activation in response to thrombopoietin and stem cell factor. Gene expression analysis reveals significant downregulation of genes related to HSC quiescence and self-renewal in Jak2-deficient LSK cells. These data suggest that Jak2 plays a critical role in the maintenance and function of adult HSCs.
Patients with myelofibrosis (MF) often develop anemia and frequently become dependent on red blood cell transfusions. Results from a phase 2 study for the treatment of MF with the Janus kinase 1/2 ...(JAK1/2) inhibitor momelotinib (MMB) demonstrated that MMB treatment ameliorated anemia, which was unexpected for a JAK1/2 inhibitor, because erythropoietin-mediated JAK2 signaling is essential for erythropoiesis. Using a rat model of anemia of chronic disease, we demonstrated that MMB treatment can normalize hemoglobin and red blood cell numbers. We found that this positive effect is driven by direct inhibition of the bone morphogenic protein receptor kinase activin A receptor, type I (ACVR1), and the subsequent reduction of hepatocyte hepcidin production. Of note, ruxolitinib, a JAK1/2 inhibitor approved for the treatment of MF, had no inhibitory activity on this pathway. Further, we demonstrated the effect of MMB is not mediated by direct inhibition of JAK2-mediated ferroportin (FPN1) degradation, because neither MMB treatment nor myeloid-specific deletion of JAK2 affected FPN1 expression. Our data support the hypothesis that the improvement of inflammatory anemia by MMB results from inhibition of ACVR1-mediated hepcidin expression in the liver, which leads to increased mobilization of sequestered iron from cellular stores and subsequent stimulation of erythropoiesis.
•MMB ameliorates anemia in a rodent anemia of chronic disease model by inhibiting activin receptor-like kinase-2 activity.•Hepcidin-dependent ferroportin degradation is independent of JAK2 phosphorylation.
Janus kinases (JAKs) and signal transducers and activators of transcription (STATs) have been shown to function downstream of several peptide hormones and cytokines that are required for postnatal ...development and secretory function of the mammary gland. As part of an extended network, these signal transducers can engage in crosstalk with other pathways to facilitate synergistic, and sometimes antagonistic, actions of different growth factors. Specifically, signaling through the JAK2/STAT5 cascade has been demonstrated to be indispensable for the specification, proliferation, differentiation, and survival of secretory mammary epithelial cells. Following a concise description of major cellular programs in mammary gland development and the role of growth factors that rely on JAK/STAT signaling to orchestrate these programs, this review highlights the significance of active STAT5 and its crosstalk with the PI3 kinase and AKT1 for mediating the proliferation of alveolar progenitors and survival of their functionally differentiated descendants in the mammary gland. Based on its ability to provide self-sufficiency in growth signals that are also capable of overriding intrinsic cell death programs, persistently active STAT5 can serve as a potent oncoprotein that contributes to the genesis of breast cancer. Recent experimental evidence demonstrated that, similar to normal developmental programs, oncogenic functions of STAT5 rely on molecular crosstalk with PI3K/AKT signaling for the initiation, and in some instances the progression, of breast cancer. The multitude by which STATs can interact with individual mediators of the PI3K/AKT signaling cascade may provide novel avenues for targeting signaling nodes within molecular networks that are crucial for the survival of cancer cells.
Cellular plasticity is a phenomenon where cells adopt different identities during development and tissue homeostasis as a response to physiological and pathological conditions. This review provides a ...general introduction to processes by which cells change their identity as well as the current definition of cellular plasticity in the field of mammary gland biology. Following a synopsis of the evolving model of the hierarchical development of mammary epithelial cell lineages, we discuss changes in cell identity during normal mammary gland development with particular emphasis on the effect of the gestation cycle on the emergence of new cellular states. Next, we summarize known mechanisms that promote the plasticity of epithelial lineages in the normal mammary gland and highlight the importance of the microenvironment and extracellular matrix. A discourse of cellular reprogramming during the early stages of mammary tumorigenesis that follows focuses on the origin of basal-like breast cancers from luminal progenitors and oncogenic signaling networks that orchestrate diverse developmental trajectories of transforming epithelial cells. In addition to the epithelial-to-mesenchymal transition, we highlight events of cellular reprogramming during breast cancer progression in the context of intrinsic molecular subtype switching and the genesis of the claudin-low breast cancer subtype, which represents the far end of the spectrum of epithelial cell plasticity. In the final section, we will discuss recent advances in the design of genetically engineered models to gain insight into the dynamic processes that promote cellular plasticity during mammary gland development and tumorigenesis in vivo.
A central and unique aspect of high-grade serous ovarian carcinoma (HGSC) is the extensive transcoelomic spreading of tumor cell via the peritoneal fluid or malignant ascites. We and others ...identified tumor-associated macrophages (TAM) in the ascites as promoters of metastasis-associated processes like extracellular matrix (ECM) remodeling, tumor cell migration, adhesion, and invasion. The precise mechanisms and mediators involved in these functions of TAM are, however, largely unknown. We observed that HGSC migration is promoted by soluble mediators from ascites-derived TAM, which can be emulated by conditioned medium from monocyte-derived macrophages (MDM) differentiated in ascites to TAM-like asc-MDM. A similar effect was observed with IL-10-induced alternatively activated m2c-MDM but not with LPS/IFNγ-induced inflammatory m1-MDM. These observations provided the basis for deconvolution of the complex TAM secretome by performing comparative secretome analysis of matched triplets of different MDM phenotypes with different pro-migratory properties (asc-MDM, m2c-MDM, m1-MDM). Mass spectrometric analysis identified an overlapping set of nine proteins secreted by both asc-MDM and m2c-MDM, but not by m1-MDM. Of these, three proteins, i.e., transforming growth factor beta-induced (TGFBI) protein, tenascin C (TNC), and fibronectin (FN1), have been associated with migration-related functions. Intriguingly, increased ascites concentrations of TGFBI, TNC, and fibronectin were associated with short progression-free survival. Furthermore, transcriptome and secretome analyses point to TAM as major producers of these proteins, further supporting an essential role for TAM in promoting HGSC progression. Consistent with this hypothesis, we were able to demonstrate that the migration-inducing potential of asc-MDM and m2c-MDM secretomes is inhibited, at least partially, by neutralizing antibodies against TGFBI and TNC or siRNA-mediated silencing of TGFBI expression. In conclusion, the present study provides the first experimental evidence that TAM-derived TGFBI and TNC in ascites promote HGSC progression.
The estrogen receptor-α (ERα) is a critical transcription factor that regulates epithelial cell proliferation and ductal morphogenesis during postnatal mammary gland development. Tissue recombination ...and transplantation studies using the first generation of ERα knockout (ERKO) mice suggested that this steroid hormone receptor is required in the mammary stroma that subsequently exerts its effect on the epithelium through additional paracrine signaling events. A more detailed analysis revealed that ERKO mice produce a truncated ERα protein with detectable transactivation activity, and it is likely that this functional ERα variant has masked the biological significance of this steroid receptor in the mammary epithelium. In this article, we describe the generation a Cre-lox-based conditional knockout of the ERα gene to study the biological function of this steroid receptor in the epithelial compartment at defined stages of mammary gland development. The mouse mammary tumor virus (MMTV)-Cre-mediated, epithelial-specific ablation of exon 3 of the ERα gene in virgin mice severely impaired ductal elongation and side branching. The conditional knockout resulted in ablation of the ERα protein, and the progesterone receptor (PR), whose expression is under the control of ERα, was largely absent. The whey acidic protein (WAP)-Cre-mediated deletion of ERα during successive gestation cycles resulted in a loss of ductal side-branching and lobuloalveolar structures, ductal dilation, and decreased proliferation of alveolar progenitors. These abnormalities compromised milk production and led to malnourishment of the offspring by the second lactation. These observations suggest that ERα expression in the mammary epithelium is essential for normal ductal morphogenesis during puberty and alveologenesis during pregnancy and lactation.
Mutant KRAS and c-MYC are oncogenic drivers and rational therapeutic targets for the treatment of pancreatic cancer. Although tumor growth and homeostasis are largely dependent on these oncogenes, a ...few residual cancer cells are able to survive the ablation of mutant KRAS and c-MYC. By performing a genome-wide gene expression analysis of in vivo-derived bulk tumor cells and residual cancer cells lacking the expression of mutant KRAS or c-MYC, we have identified an increase in autocrine IGF1/AKT signaling as a common survival mechanism in dormant cancer cells. The pharmacological inhibition of IGF-1R reduces residual disease burden and cancer recurrence, suggesting that this molecular pathway is crucial for the survival of cancer cells in the absence of the primary oncogenic drivers.
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•Tumor cells that remain dormant following oncogene ablation can cause cancer recurrence•Tumor dormancy is associated with a cancer cell-intrinsic increase in IGF1/AKT signaling•Overexpression of IGF-1R increases residual disease•Inhibition of IGF-1R reduces the survival of dormant cancer cells and cancer recurrence
Rajbhandari et al. demonstrate that an increase in autocrine IGF1 signaling mediates the survival of residual pancreatic cancer cells following the ablation of oncogenic drivers (mutant KRAS and c-MYC). They provide experimental evidence that inhibiting IGF-1R can eradicate minimal residual disease and reduce cancer recurrence in vivo.
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