The effect of activin/TGF [beta] signaling in mammary epithelial and breast cancer cells /

Activin and TGFbeta, members of the TGFbeta superfamily, are pluripotent cytokines that are expressed in virtually every cell of the body. These factors play diverse roles in the body such as regulating early development of the embryo, differentiation, extracellular matrix formation, hematopoiesis, angiogenesis and immune functions. TGFbeta superfamily signaling is transduced by heteromeric serine/threonine kinase receptors at the cell surface and the intracellular mediator, the Smad complex. Following activation of the receptors, there is recruitment and phosphorylation the Smads. As a result the Smad proteins accumulate in the nucleus, bind co-activators or repressors and elicit or suppress transcription of target genes.To date, the molecular signaling mechanisms for activin/TGFbeta in mammary gland growth and differentiation have not been fully elucidated. Our data identify a novel regulatory crosstalk mechanism by which activin/TGFbeta induced Smad signaling acts to antagonize Stat5 transactivation in mammary epithelial cells. We demonstrate an inhibitory effect of activin/TGFbeta on milk protein expression, specifically betacasein. We further show that activin/TGFbeta inhibitory effect upon betacasein expression is not due to changes in either Stat5 phosphorylation, translocation to the nucleus or binding on the Stat5 response element. We finally demonstrate that the Smads are required to block Stat5 transactivation by activin/TGFbeta and show that they are important mediators in activin/TGFbeta inhibitory response upon Stat5 target gene expression, in particular betacasein and cyclin D1. Finally, we unveil the mechanism by which these two signaling cascades antagonize their effects and find that activated Smads inhibit Stat5 association with its co-activator CBP, thus blocking Stat5 transactivation of its target genes. Thus, we define a novel crosstalk mechanism between two divergent signaling pathways that are involved in regulating mammary gland growth and differentiation.Whereas the role of TGFbeta signaling in breast cancer has been well characterized, we sought out to study the role and mechanism of action of activin in the human breast cancer T47D cells. We found that activin treatment of T47D cells leads to a potent inhibition of cell growth. We further show that activin induces the Smad, the p38-mitogen activated kinase pathways and the p38 downstream target ATF2. Finally, using specific inhibitors to block p38 MAPK, activin-mediated cell growth inhibition is completely abolished. Together, these results define a novel signaling mechanism induced by activin in breast cancer cells.Finally in an attempt to identify genes regulated by activin in breast cancer cells, we discover the death adaptor molecule RAIDD as a novel target of activin signaling. We show that RAIDD mRNA and protein levels are potently upregulated by activin. Using antisense-oligos directed against RAIDD, we show that RAIDD expression is necessary in mediating activin inhibition in breast cancer cells. Hence, we define the involvement of a new player in activin mediated cell growth inhibition.Collectively, these studies reveal novel mechanisms of the activin/TGFbeta signaling cascade in normal mammary epithelial cells and breast cancer cells

The Development of Novel Therapies for the Treatment of Acute Myeloid Leukemia (AML)

cancer

The G protein-coupled receptor kinase-2 is a TGFβ-inducible antagonist of TGFβ signal transduction

Signaling from the activin/transforming growth factor β (TGFβ) family of cytokines is a tightly regulated process. Disregulation of TGFβ signaling is often the underlying basis for various cancers, tumor metastasis, inflammatory and autoimmune diseases. In this study, we identify the protein G-coupled receptor kinase 2 (GRK2), a kinase involved in the desensitization of G protein-coupled receptors (GPCR), as a downstream target and regulator of the TGFβ-signaling cascade. TGFβ-induced expression of GRK2 acts in a negative feedback loop to control TGFβ biological responses. Upon TGFβ stimulation, GRK2 associates with the receptor-regulated Smads (R-Smads) through their MH1 and MH2 domains and phosphorylates their linker region. GRK2 phosphorylation of the R-Smads inhibits their carboxyl-terminal, activating phosphorylation by the type I receptor kinase, thus preventing nuclear translocation of the Smad complex, leading to the inhibition of TGFβ-mediated target gene expression, cell growth inhibition and apoptosis. Furthermore, we demonstrate that GRK2 antagonizes TGFβ-induced target gene expression and apoptosis ex vivo in primary hepatocytes, establishing a new role for GRK2 in modulating single-transmembrane serine/threonine kinase receptor-mediated signal transduction

Tyrosine Phosphorylation of Grb2: Role in Prolactin/Epidermal Growth Factor Cross Talk in Mammary Epithelial Cell Growth and Differentiation▿

Characterizing mechanisms regulating mammary cell growth and differentiation is vital, as they may contribute to breast carcinogenesis. Here, we examine a cross talk mechanism(s) downstream of prolactin (PRL), a primary differentiation hormone, and epidermal growth factor (EGF), an important proliferative factor, in mammary epithelial cell growth and differentiation. Our data indicate that EGF exerts inhibitory effects on PRL-induced cellular differentiation by interfering with Stat5a-mediated gene expression independent of the PRL-proximal signaling cascade. Additionally, our data show that PRL is a potent inhibitor of EGF-induced cell proliferation. We identify tyrosine phosphorylation of the growth factor receptor-bound protein 2 (Grb2) as a critical mechanism by which PRL antagonizes EGF-induced cell proliferation by attenuating the activation of the Ras/mitogen-activated protein kinase (MAPK) pathway. Together, our results define a novel negative cross-regulation between PRL and EGF involving the Jak2/Stat5a and Ras/MAPK pathways through tyrosine phosphorylation of Grb2

Peripheral and local predictive immune signatures identified in a phase II trial of ipilimumab with carboplatin/paclitaxel in unresectable stage III or stage IV melanoma

BACKGROUND: Checkpoint blockade with ipilimumab provides long-term survival to a significant proportion of patients with metastatic melanoma. New approaches to increase survival and to predict which patients will benefit from treatment are needed. This phase II trial combined ipilimumab with carboplatin/paclitaxel (CP) to assess its safety, efficacy, and to search for peripheral and tumor-based predictive biomarkers. METHODS: Thirty patients with untreated unresectable/metastatic melanoma were treated with ipilimumab and CP. Adverse events (AEs) were monitored and response to treatment was evaluated. Tumor tissue and peripheral blood were collected at specified time points to characterize tumor immune markers by immunohistochemistry and systemic immune activity by multiplex assays and flow cytometry. RESULTS: Eighty three percent of patients received all 5 cycles of CP and 93% completed ipilimumab induction. Serious AEs occurred in 13% of patients, and no treatment-related deaths were observed. Best Overall Response Rate (BORR) and Disease Control Rate (DCR) were 27 and 57%, respectively. Median overall survival was 16.2 months. Response to treatment was positively correlated with a higher tumor CD3+ infiltrate (immune score) at baseline. NRAS and BRAF mutations were less frequent in patients who experienced clinical benefit. Assessment of peripheral blood revealed that non-responders had elevated baseline levels of CXCL8 and CCL4, and a higher proportion of circulating late differentiated B cells. Pre-existing high levels of chemokines (CCL3, CCL4 and CXCL8) and advanced B cell differentiation were strongly associated with worse patient overall survival. Elevated proportions of circulating CD8+/PD-1+ T cells during treatment were associated with worse survival. CONCLUSIONS: The combination of ipilimumab and CP was well tolerated and revealed novel characteristics associated with patients likely to benefit from treatment. A pre-existing systemic inflammatory state characterized by elevation of selected chemokines and advanced B cell differentiation, was strongly associated with poor patient outcomes, revealing potential predictive circulating biomarkers. TRIAL REGISTRATION: Clinicaltrials.gov , NCT01676649 , registered on August 29, 2012