Single-cell RNA-sequencing of human spleens reveals an IDO-1 tolerogenic dendritic cell subset in pancreatic cancer patients that is absent in normal individuals.

Local and systemic immunosuppression are prominent features of pancreatic cancer, rendering anti-tumor effector cells inactive and immunotherapeutic approaches ineffective. The spleen, an understudied point of antigen-presentation and T cell priming in humans, holds particular importance in pancreatic cancer due to its proximity to the developing tumor. As main effectors of antigen presentation, dendritic cells display antigens to lymphocytes, thereby bridging the innate and adaptive immune response.

The Janus kinase 1 is critical for pancreatic cancer initiation and progression.

Interleukin-6 (IL-6)-class inflammatory cytokines signal through the Janus tyrosine kinase (JAK)/signal transducer and activator of transcription (STAT) pathway and promote the development of pancreatic ductal adenocarcinoma (PDAC); however, the functions of specific intracellular signaling mediators in this process are less well defined. Using a ligand-controlled and pancreas-specific knockout in adult mice, we demonstrate in this study that JAK1 deficiency prevents the formation of KRAS-induced pancreatic tumors, and we establish that JAK1 is essential for the constitutive activation of STAT3, whose activation is a prominent characteristic of PDAC. We identify CCAAT/enhancer binding protein δ (C/EBPδ) as a biologically relevant downstream target of JAK1 signaling, which is upregulated in human PDAC.

Dual recombinase action in the normal and neoplastic mammary gland epithelium.

We developed a transgenic mouse line that expresses the codon-optimized Flp recombinase under the control of the MMTV promoter in luminal epithelial cells of the mammary gland. In this report, we demonstrate the versatile applicability of the new MMTV-Flp strain to manipulate genes in a temporally and spatially controlled manner in the normal mammary gland, in luminal-type mammary tumors that overexpress ERBB2, and in a new KRAS-associated mammary cancer model. Although the MMTV-Flp is expressed in a mosaic pattern in the luminal epithelium, the Flp-mediated activation of a mutant Kras allele resulted in basal-like mammary tumors that progressively acquired mesenchymal features.

Highly metastatic claudin-low mammary cancers can originate from luminal epithelial cells.

Claudin-low breast cancer represents an aggressive molecular subtype that is comprised of mostly triple-negative mammary tumor cells that possess stem cell-like and mesenchymal features. Little is known about the cellular origin and oncogenic drivers that promote claudin-low breast cancer. In this study, we show that persistent oncogenic RAS signaling causes highly metastatic triple-negative mammary tumors in mice.

The Multifaceted Roles of the Tumor Susceptibility Gene 101 (TSG101) in Normal Development and Disease.

The multidomain protein encoded by the () is ubiquitously expressed and is suggested to function in diverse intracellular processes. In this review, we provide a succinct overview of the main structural features of the protein and their suggested roles in molecular and cellular functions. We then summarize, in more detail, key findings from studies using genetically engineered animal models that demonstrate essential functions of TSG101 in cell proliferation and survival, normal tissue homeostasis, and tumorigenesis.

Efficient tissue-type specific expression of target genes in a tetracycline-controlled manner from the ubiquitously active Eef1a1 locus.

Using an efficient gene targeting approach, we developed a novel mouse line that expresses the tetracycline-controlled transactivator (tTA) from the constitutively active Eef1a1 locus in a Cre recombinase-inducible manner. The temporally and spatially controlled expression of the EF1-LSL-tTA knockin and activation of tTA-driven responder transgenes was tested using four transgenic lines that express Cre under tissue-specific promoters of the pancreas, mammary gland and other secretory tissues, as well as an interferon-inducible promoter. In all models, the endogenous Eef1a1 promoter facilitated a cell-type-specific activation of target genes at high levels without exogenous enhancer elements.

Janus Kinase 1 Plays a Critical Role in Mammary Cancer Progression.

Janus kinases (JAKs) and their downstream STAT proteins play key roles in cytokine signaling, tissue homeostasis, and cancer development. Using a breast cancer model that conditionally lacks Janus kinase 1, we show here that JAK1 is essential for IL-6-class inflammatory cytokine signaling and plays a critical role in metastatic cancer progression. JAK1 is indispensable for the oncogenic activation of STAT1, STAT3, and STAT6 in ERBB2-expressing cancer cells, suggesting that ERBB2 receptor tyrosine kinase complexes do not directly activate these STAT proteins in vivo.

Autocrine IGF1 Signaling Mediates Pancreatic Tumor Cell Dormancy in the Absence of Oncogenic Drivers.

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.

Generation of Janus kinase 1 (JAK1) conditional knockout mice.

The biological functions of the Janus kinase 1 (JAK1) are suggested to be pleiotropic since this signal transducer is ubiquitously expressed and coupled to a variety of cytokine receptors. Consequently, mice that are deficient in this tyrosine kinase were reported to die shortly after birth. To facilitate studies that address the biological and molecular functions of JAK1 during postnatal development, we performed gene targeting in embryonic stem cells and generated a Cre/lox-based conditional knockout mouse model.

Janus Kinase 1 Is Essential for Inflammatory Cytokine Signaling and Mammary Gland Remodeling.

Despite a wealth of knowledge about the significance of individual signal transducers and activators of transcription (STATs), essential functions of their upstream Janus kinases (JAKs) during postnatal development are less well defined. Using a novel mammary gland-specific JAK1 knockout model, we demonstrate here that this tyrosine kinase is essential for the activation of STAT1, STAT3, and STAT6 in the mammary epithelium. The loss of JAK1 uncouples interleukin-6-class ligands from their downstream effector, STAT3, which leads to the decreased expression of STAT3 target genes that are associated with the acute-phase response, inflammation, and wound healing.

Novel transcripts from a distinct promoter that encode the full-length AKT1 in human breast cancer cells.

Background: The serine-threonine kinase AKT1 plays essential roles during normal mammary gland development as well as the initiation and progression of breast cancer. AKT1 is generally considered a ubiquitously expressed gene, and its persistent activation is transcriptionally controlled by regulatory elements characteristic of housekeeping gene promoters. We recently identified a novel Akt1 transcript in mice (Akt1m), which is induced by growth factors and their signal transducers of transcription from a previously unknown promoter.

Stat5 regulates the phosphatidylinositol 3-kinase/Akt1 pathway during mammary gland development and tumorigenesis.

Stat5 (signal transducer and activator of transcription 5) is an essential mediator of cytokine receptor signaling and plays important roles in the proliferation of alveolar progenitors and the survival of functionally differentiated epithelial cells in the mammary gland. A deregulated expression and activation of Stat5 leads to precocious alveolar development in the absence of pregnancy hormones, impaired mammary gland remodeling following the cessation of lactation, and mammary tumor formation. We reported previously that Stat5 induces the transcription of the Akt1 gene from a novel promoter.

Gain-of-function of Stat5 leads to excessive granulopoiesis and lethal extravasation of granulocytes to the lung.

The Signal Transducer and Activator of Transcription 5 (Stat5) plays a significant role in normal hematopoiesis and a variety of hematopoietic malignancies. Deficiency in Stat5 causes impaired cytokine-mediated proliferation and survival of progenitors and their differentiated descendants along major hematopoietic lineages such as erythroid, lymphoid, and myeloid cells. Overexpression and persistent activation of Stat5 are sufficient for neoplastic transformation and development of multi-lineage leukemia in a transplant model.

Dormant cancer cells contribute to residual disease in a model of reversible pancreatic cancer.

The initiation and progression of pancreatic ductal adenocarcinoma (PDAC) is governed by a series of genetic and epigenetic changes, but it is still unknown whether these alterations are required for the maintenance of primary and metastatic PDAC. We show here that the c-Myc oncogene is upregulated throughout the entire process of neoplastic progression in human PDAC and in genetically engineered mice that express mutant Kras. To experimentally address whether c-Myc is essential for the growth and survival of cancer cells, we developed a novel mouse model that allows a temporally and spatially controlled expression of this oncogene in pancreatic progenitors and derived lineages of the exocrine pancreas.

Cyclin D3 compensates for the loss of cyclin D1 during ErbB2-induced mammary tumor initiation and progression.

Cyclin D1 regulates cell proliferation and is a candidate molecular target for breast cancer therapy. This study addresses whether Cyclin D1 is indispensable for ErbB2-associated mammary tumor initiation and progression using a breast cancer model in which this cell-cycle regulator can be genetically ablated prior to or after neoplastic transformation. Deficiency in Cyclin D1 delayed tumor onset but did not prevent the occurrence of mammary cancer in mice overexpressing wild-type ErbB2.

Stat5 promotes survival of mammary epithelial cells through transcriptional activation of a distinct promoter in Akt1.

The signal transducer and activator of transcription 5 (Stat5) plays a pivotal role in the proliferation, secretory differentiation, and survival of mammary epithelial cells. However, there is little information about Stat5 target genes that facilitate these biological processes. We provide here experimental evidence that the prolactin-mediated phosphorylation of Stat5 regulates the transcriptional activation of the Akt1 gene.

Temporally and spatially controlled expression of transgenes in embryonic and adult tissues.

Using ES cell-mediated transgenesis, we generated a novel mouse strain that permits a temporally and spatially controlled expression of responder genes in embryonic and multiple adult tissues. The transgene was constructed in a way that a CMV enhancer linked to the chicken beta-actin promoter (CAG) drives the expression of the tetracycline-controlled transactivator (tTA) in particular tissues upon Cre-mediated excision of a floxed betageo marker located between the promoter and the tTA. Based on the enzymatic activity of lacZ, the CAG-betageo-tTA construct exhibits a widespread expression and appears to be very strong in the brain, heart, muscle, pancreas, and skin.

Targeting janus kinase 2 in Her2/neu-expressing mammary cancer: Implications for cancer prevention and therapy.

The Janus kinase 2 (Jak2) is essential for normal mammary gland development, but this tyrosine kinase and its main effector, signal transducer and activator of transcription 5, are also active in a significant subset of human breast cancers. We have recently reported that Jak2 controls the expression and nuclear accumulation of cyclin D1. Because this particular D-type cyclin has been suggested to be a key mediator for ErbB2-associated mammary tumorigenesis, we deleted Jak2 from ErbB2-expressing mammary epithelial cells prior to tumor onset and in neoplastic cells to address whether this tyrosine kinase plays a role in the initiation as well as progression of mammary cancer.

Longitudinal analysis of mammogenesis using a novel tetracycline-inducible mouse model and in vivo imaging.

We generated a novel mouse model, which expresses the tetracycline-inducible transactivator under the regulation of the endogenous whey acidic protein gene. Using a tet-responsive luciferase reporter transgene, we demonstrated that the Wap-rtTA knockin allele allows a tightly controlled temporal and spatial expression of transgenes in the mammary gland in a ligand-inducible manner. The longitudinal analysis of individual females throughout their reproductive cycles using in vivo bioluminescence imaging confirmed that the expression of the Wap-rtTA knockin allele is highly upregulated during lactation.

A mammary-specific, long-range deletion on mouse chromosome 11 accelerates Brca1-associated mammary tumorigenesis.

We engineered a mammary-specific knockout model for Brca1 deficiency that also lacks the majority of one chromosome 11 to determine whether tumor susceptibility loci reside on this chromosome that cooperate with the loss of Brca1 during mammary cancer formation. Brca1-deficient females that are haploinsufficient in 60 cM of chromosome 11 exhibited accelerated mammary tumorigenesis in comparison to Brca1 conditional knockout mice. On the histopathologic level, these tumors were either adenocarcinomas or benign, inflammatory lesions.

The Janus kinase 2 is required for expression and nuclear accumulation of cyclin D1 in proliferating mammary epithelial cells.

Using a conditional knockout approach, we previously demonstrated that the Janus kinase 2 (Jak2) is crucial for prolactin (PRL) signaling and normal mammary gland development. PRL is suggested to synchronously activate multiple signaling cascades that emerge on the PRL receptor (PRLR). This study demonstrates that Jak2 is essential for the activation of the signal transducer and activator of transcription 5 (Stat5) and expression of Cish (cytokine-inducible SH2-containing protein), a Stat5-responsive negative regulator of Jak/Stat signaling.

Parity-induced mammary epithelial cells are multipotent and express cell surface markers associated with stem cells.

Parity-induced mammary epithelial cells (PI-MECs) are defined as a pregnancy hormone-responsive cell population that activates the promoter of late milk protein genes during the second half of pregnancy and lactation. However, unlike their terminally differentiated counterparts, these cells do not undergo programmed cell death during post-lactational remodeling of the gland. We previously demonstrated that upon transplantation into an epithelial-free mammary fat pad, PI-MECs exhibited two important features of multipotent mammary epithelial progenitors: a) self-renewal, and b) contribution to ductal and alveolar morphogenesis.

Expression of the whey acidic protein (Wap) is necessary for adequate nourishment of the offspring but not functional differentiation of mammary epithelial cells.

Whey acidic protein (WAP) is the principal whey protein found in rodent milk, which contains a cysteine-rich motif identified in some protease inhibitors and proteins involved in tissue modeling. The expression of the Wap gene, which is principally restricted to the mammary gland, increases more than 1,000-fold around mid-pregnancy. To determine whether the expression of this major milk protein gene is a prerequisite for functional differentiation of mammary epithelial cells, we generated conventional knockout mice lacking two alleles of the Wap gene.

Generation of a conditional knockout allele for the Janus kinase 2 (Jak2) gene in mice.

To study biologically relevant functions of the Janus kinase 2 (Jak2) in multiple cytokine and hormone receptor signal transduction pathways, we generated a conditional knockout (floxed) allele of this gene by placing loxP sites around the first coding exon of Jak2. Homozygous floxed animals developed normally and exhibited no phenotypic abnormalities. The conversion of the floxed allele into a null mutation was achieved by transmitting the targeted allele through the female germline of MMTV-Cre (line A) mice.

Parity-induced mammary epithelial cells facilitate tumorigenesis in MMTV-neu transgenic mice.

Using a Cre-lox-based genetic labeling technique, we have recently discovered a parity-induced mammary epithelial subtype that is abundant in nonlactating and nonpregnant, parous females. These mammary epithelial cells serve as alveolar progenitors in subsequent pregnancies, and transplantation studies revealed that they possess features of multipotent progenitors such as self-renewal and the capability to contribute to ductal and alveolar morphogenesis. Here, we report that these cells are the cellular targets for transformation in MMTV-neu transgenic mice that exhibit accelerated mammary tumorigenesis in multiparous animals.