The mammalian Cks family consists of 2 well-conserved small proteins, Cks1 and Cks2. Cks1 has been shown to promote cellcycle progression by triggering degradation of p27 kip1 . The function of Cks2 in somatic mammalian cells is not well understood although it is required for the first metaphase/anaphase transition during the meiosis. Emerging evidence shows that elevated expression of Cks1 and Cks2 is often found in a variety of tumors, and is correlated with poor survival rate of the patients. Here we demonstrated that expression of Cks1 and Cks2 were elevated in prostate tumors of human and animal models, as well as prostatic cancer cell lines. Forced expression of Cks1 and Cks2 in benign prostate tumor epithelial cells promoted cell population growth. Knockdown of Cks1 expression in malignant prostate tumor cells inhibited proliferation, anchorage-independent growth, and migration activities, whereas knockdown of Cks2 expression induced programmed cell death and inhibited the tumorigenicity. Collectively, the data suggest that elevated expression of Cks1 contributes to the tumorigenicity of prostate tumor cells by promoting cell growth and elevated expression of Cks2 protects the cells from apoptosis. Thus, the finding suggests a novel therapeutic strategy for prostatic cancer based on inhibiting Cks1 and Cks2 activity. ' 2008 Wiley-Liss, Inc.Key words: prostate cancer; animal model; apoptosis; shRNA The human Cks (also designated as CksHs) family consists of 2 well-conserved members, Cks1 and Cks2, both of which are identified based on the sequence homology to yeast suc1 and Cks1 (Cdc28 kinase subunit 1) that are essential for cell cycle-control.
SummaryThe cardiac outflow tract (OFT) is a developmentally complex structure derived from multiple lineages and is often defective in human congenital anomalies. While emerging evidence shows that the fibroblast growth factor (FGF) is essential for OFT development, the downstream pathways mediating FGF-signaling in cardiac progenitors remain poorly understood. Here, we report that FRS2α, an adaptor protein that links FGF receptor kinases to multiple signaling pathways, mediates critical aspects of FGF-dependent OFT development. Ablation of Frs2α in mesodermal OFT progenitor cells that originate in the second heart field (SHF) affects their expansion into the OFT myocardium, resulting in OFT misalignment and hypoplasia. Moreover, Frs2α mutants had defective endothelial-mesenchymal-transition and neural crest cell recruitment into the OFT cushions, resulting in OFT septation defects. The results provide new insight into the signaling molecules downstream of FGF receptor tyrosine kinases in cardiac progenitors.
The fibroblast growth factor (FGF) regulates a broad spectrum of biological activities by activation of transmembrane FGF receptor (FGFR) tyrosine kinases and their coupled intracellular signaling pathways. FGF receptor substrate 2alpha (FRS2alpha) is an FGFR interactive adaptor protein that links multiple signaling pathways to the activated FGFR kinase. We previously showed that FGFR2 in the prostate epithelium is important for branching morphogenesis and for the acquisition of the androgen responsiveness. Here we show in mice that FRS2alpha is uniformly expressed in the epithelial cells of developing prostates, whereas it is expressed only in basal cells of the mature prostate epithelium. However, expression of FRS2alpha was apparent in luminal epithelial cells of regenerating prostates and prostate tumors. To investigate FRS2alpha function in the prostate, the Frs2alpha alleles were ablated specifically in the prostatic epithelial precursor cells during prostate development. Similar to the ablation of Fgfr2, ablation of Frs2alpha disrupted MAP kinase activation, impaired prostatic ductal branching morphogenesis and compromised cell proliferation. Unlike the Fgfr2 ablation, disrupting Frs2alpha had no effect on the response of the prostate to androgens. More importantly, ablation of Frs2alpha inhibited prostatic tumorigenesis induced by oncogenic viral proteins. The results suggest that FRS2alpha-mediated signals in prostate epithelial cells promote branching morphogenesis and proliferation, and that aberrant activation of FRS2-linked pathways might promote tumorigenesis. Thus, the prostate-specific Frs2alpha(cn) mice provide a useful animal model for scrutinizing the molecular mechanisms underlying prostatic development and tumorigenesis.
NVP-BKM120 is a novel phosphatidylinositol 3-kinase (PI3K) inhibitor and is currently being investigated in phase I clinical trials in solid tumors. This study aimed to evaluate the therapeutic efficacy of BKM120 in multiple myeloma (MM). BKM120 induces cell growth inhibition and apoptosis in both MM cell lines and freshly isolated primary MM cells. However, BKM120 only shows limited cytotoxicity toward normal lymphocytes. The presence of MM bone marrow stromal cells, insulin-like growth factor, or interleukin-6 does not affect BKM120-induced tumor cell apoptosis. More importantly, BKM120 treatment significantly inhibits tumor growth in vivo and prolongs the survival of myeloma-bearing mice. In addition, BKM120 shows synergistic cytotoxicity with dexamethasone in dexamethasone-sensitive MM cells. Low doses of BKM120 and dexamethasone, each of which alone has limited cytotoxicity, induce significant cell apoptosis in MM.1S and ARP-1. Mechanistic study shows that BKM120 exposure causes cell cycle arrest by upregulating p27 (Kip1) and downregulating cyclin D1 and induces caspase-dependent apoptosis by downregulating antiapoptotic XIAP and upregulating expression of cytotoxic small isoform of Bim, BimS. In summary, our findings demonstrate the in vitro and in vivo anti-MM activity of BKM120 and suggest that BKM120 alone or together with other MM chemotherapeutics, particularly dexamethasone, may be a promising treatment for MM.
Bone destruction is a hallmark of multiple myeloma and affects more than 80% of patients. However, current therapy is unable to completely cure and/or prevent bone lesions. Although it is accepted that myeloma cells mediate bone destruction by inhibition of osteoblasts and activation of osteoclasts, the underlying mechanism is still poorly understood. This study demonstrates that constitutive activation of p38 mitogen-activated protein kinase in myeloma cells is responsible for myeloma-induced osteolysis. Our results show that p38 is constitutively activated in most myeloma cell lines and primary myeloma cells from patients. Myeloma cells with high/detectable p38 activity, but not those with low/undetectable p38 activity, injected into SCID or SCID-hu mice caused bone destruction. Inhibition or knockdown of p38 in human myeloma reduced or prevented myeloma-induced osteolytic bone lesions without affecting tumor growth, survival, or homing to bone. Mechanistic studies showed that myeloma cell p38 activity inhibited osteoblastogenesis and bone formation and activated osteoclastogenesis and bone resorption in myeloma-bearing SCID mice. This study elucidates a novel molecular mechanism—sactivation of p38 signaling in myeloma cells—by which myeloma cells induce osteolytic bone lesions and indicates that targeting myeloma cell p38 may be a viable approach to treating or preventing myeloma bone disease.
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