We have previously shown that secondmessenger-dependent kinases (cAMP-dependent kinase, protein kinase C) in the olfactory system are essential in terminating second-messenger signaling in response to odorants. We now document that subtype 2 of the ,B-adrenergic receptor kinase (fARK) is also involved in this process. By using subtype-specific antibodies to .ARK-1 and I3ARK-2, we show that flARK-2 is preferentially expressed in the olfactory epithelium in contrast to 'mdings in most other tissues. Heparin, an inhibitor of DARK, as well as anti-flARK-2 antibodies, (i) completely prevents the rapid decline of second-messenger signals (desensitization) that follows odorant stimulation and (ii) strongly inhibits odorant-induced phosphorylation of olfactory ciliary proteins. In contrast, (6ARK-1 antibodies are without effect. Inhibitors ofprotein kinase A and protein kinase C also block odorant-induced desensitization and phosphorylation. These data suggest that a sequential interplay of secondmessenger-dependent and receptor-specific kinases is functionally involved in olfactory desensitization.The olfactory system responds precisely to iterative stimulation (1) and thus can continuously monitor changes in the odorous environment occurring between consecutive sniffs. This sensory behavior is due to characteristic phasic responses of receptor cells to short odor pulses (2), thereby preventing a brief stimulus from being perceived as continuous smell. The basis for this characteristic feature of olfactory neurons is a rapid termination of the odor-induced primary reaction-i.e., the second-messenger cascade initiated by an odorant-occupied receptor is rapidly turned off (3,4). Recent studies have indicated that olfactory signaling is terminated by uncoupling the transduction cascade; this is accomplished via a negative-feedback reaction controlled by the second messenger elicited upon odor stimulation. Second-messenger-activated protein kinases [protein kinase A (PKA) or protein kinase C (PKC)] presumably phosphorylate elements of the transduction apparatus and thereby uncouple the signaling cascade (5). Subsequent experiments have shown that stimulation with odorants indeed caused significant phosphorylation of olfactory ciliary proteins, and there is some circumstantial evidence indicating that receptor proteins for odorants may be modified via second-messengercontrolled protein kinases (6). The emerging picture for signal termination in olfaction is, in many respects, reminiscent of desensitization phenomena in other systems-notably the visual and hormonal signaling pathways, where phosphorylation of receptors in an active state uncouples the reaction cascade by preventing further stimulation ofG proteins (7,8).For the most widely studied model, the p-adrenergic system, two distinct pathways for phosphorylation and desensitization have recently been discovered. Receptor phosphorylation and cascade uncoupling may be mediated either by a cAMP-dependent protein kinase (PKA) or alternatively by a cAMP-independen...

The polyphenolic alcohol resveratrol has demonstrated promising activities for the prevention and treatment of cancer. Different modes of action have been described for resveratrol including the activation of sirtuins, which represent the class III histone deacetylases (HDACs). However, little is known about the activity of resveratrol on the classical HDACs of class I, II and IV, although these classes are involved in cancer development or progression and inhibitors of HDACs (HDACi) are currently under investigation as promising novel anticancer drugs. We could show by in silico docking studies that resveratrol has the chemical structure to inhibit the activity of different human HDAC enzymes. In vitro analyses of overall HDAC inhibition and a detailed HDAC profiling showed that resveratrol inhibited all eleven human HDACs of class I, II and IV in a dose-dependent manner. Transferring this molecular mechanism into cancer therapy strategies, resveratrol treatment was analyzed on solid tumor cell lines. Despite the fact that hepatocellular carcinoma (HCC) is known to be particularly resistant against conventional chemotherapeutics, treatment of HCC with established HDACi already has shown promising results. Testing of resveratrol on hepatoma cell lines HepG2, Hep3B and HuH7 revealed a dose-dependent antiproliferative effect on all cell lines. Interestingly, only for HepG2 cells a specific inhibition of HDACs and in turn a histone hyperacetylation caused by resveratrol was detected. Additional testing of human blood samples demonstrated a HDACi activity by resveratrol ex vivo. Concluding toxicity studies showed that primary human hepatocytes tolerated resveratrol, whereas in vivo chicken embryotoxicity assays demonstrated severe toxicity at high concentrations. Taken together, this novel pan-HDACi activity opens up a new perspective of resveratrol for cancer therapy alone or in combination with other chemotherapeutics. Moreover, resveratrol may serve as a lead structure for chemical optimization of bioavailability, pharmacology or HDAC inhibition.

The oncolytic potential of measles vaccine virus (MeV) has been demonstrated in several tumor entities. Here, we investigated the susceptibility of eight sarcoma cell lines to MeV-mediated oncolysis and found five to be susceptible, whereas three proved to be resistant. In the

Unlike other malignant bone tumors including osteosarcomas and Ewing sarcomas with a peak incidence in adolescents and young adults, conventional and dedifferentiated chondrosarcomas mainly affect people in the 4th to 7th decade of life. To date, the cell type of chondrosarcoma origin is not clearly defined. However, it seems that mesenchymal stem and progenitor cells (MSPC) in the bone marrow facing a pro-proliferative as well as predominantly chondrogenic differentiation milieu, as is implicated in early stage osteoarthritis (OA) at that age, are the source of chondrosarcoma genesis. But how can MSPC become malignant? Indeed, only one person in 1,000,000 will develop a chondrosarcoma, whereas the incidence of OA is a thousandfold higher. This means a rare coincidence of factors allowing escape from senescence and apoptosis together with induction of angiogenesis and migration is needed to generate a chondrosarcoma. At early stages, chondrosarcomas are still assumed to be an intermediate type of tumor which rarely metastasizes. Unfortunately, advanced stages show a pronounced resistance both against chemo- and radiation-therapy and frequently metastasize. In this review, we elucidate signaling pathways involved in the genesis and therapeutic resistance of chondrosarcomas with a focus on MSPC compared to signaling in articular cartilage (AC).

Stimulating the immune system to attack cancer is a promising approach, even for the control of advanced cancers. Several cytokines that promote interferon-γ-dominated immune responses show antitumor activity, with interleukin 12 (IL-12) being of major importance. Here, we used an antibody-IL-12 fusion protein (NHS-IL12) that binds histones of necrotic cells to treat human sarcoma in humanized mice. Following sarcoma engraftment, NHS-IL12 therapy was combined with either engineered IL-7 (FcIL-7) or IL-2 (IL-2MAB602) for continuous cytokine bioavailability. NHS-IL12 strongly induced innate and adaptive antitumor immunity when combined with IL-7 or IL-2. NHS-IL12 therapy significantly improved survival of sarcoma-bearing mice and caused long-term remissions when combined with IL-2. NHS-IL12 induced pronounced cancer cell senescence, as documented by strong expression of senescence-associated p16INK4a and nuclear translocation of p-HP1γ, and permanent arrest of cancer cell proliferation. In addition, this cancer immunotherapy initiated the induction of myogenic differentiation, further promoting the hypothesis that efficient antitumor immunity includes mechanisms different from cytotoxicity for efficient cancer control in vivo.