Protein kinase D2 is a novel regulator of glioblastoma growth and tumor formation.

Glioblastoma multiforme, a highly aggressive tumor of the central nervous system, has a dismal prognosis that is due in part to its resistance to radio- and chemotherapy. The protein kinase C (PKC) family of serine threonine kinases has been implicated in the formation and proliferation of glioblastoma multiforme. Members of the protein kinase D (PKD) family, which consists of PKD1, -2 and, -3, are prominent downstream targets of PKCs and could play a major role in glioblastoma growth. PKD2 was highly expressed in both low-grade and high-grade human gliomas. The number of PKD2-positive tumor cells increased with glioma grading (P < .001). PKD2 was also expressed in CD133-positive glioblastoma stem cells and various glioblastoma cell lines in which the kinase was found to be constitutively active. Inhibition of PKDs by pharmacological inhibitors resulted in substantial inhibition of glioblastoma proliferation. Furthermore, specific depletion of PKD2 by siRNA resulted in a marked inhibition of anchorage-dependent and -independent proliferation and an accumulation of glioblastoma cells in G0/G1, accompanied by a down-regulation of cyclin D1 expression. In addition, PKD2-depleted glioblastoma cells exhibited substantially reduced tumor formation in vivo on chicken chorioallantoic membranes. These findings identify PKD2 as a novel mediator of glioblastoma cell growth in vitro and in vivo and thereby as a potential therapeutic target for this devastating disease.

Selected technologies to control genes and their products for experimental and clinical purposes.

"On-demand" regulation of gene expression is a powerful tool to elucidate the functions of proteins and biologically-active RNAs. We describe here three different approaches to the regulation of expression or activity of genes or proteins. Promoter-based regulation of gene expression was among the most rapidly developing techniques in the 1980s and 1990 s. Here we provide basic information and also some characteristics of the metallothionein-promoter-based system, the tet-off system, Muristerone-A-regulated expression through the ecdysone response element, RheoSwitch, coumermycin/novobiocin-regulated gene expression, chemical dimerizer-based promoter activation systems, the "Dual Drug Control" system, "constitutive androstane receptor"-based regulation of gene expression, and RU486/mifepristone-driven regulation of promoter activity. A large part of the review concentrates on the principles and usage of various RNA interference techniques (RNAi: siRNA, shRNA, and miRNA-based methods). Finally, the last part of the review deals with historically the oldest, but still widely used, methods of temperature-dependent regulation of enzymatic activity or protein stability (temperature-sensitive mutants). Due to space limitations we do not describe in detail but just mention the tet-regulated systems and also fusion-protein-based regulation of protein activity, such as estrogen-receptor fusion proteins. The information provided below is aimed to assist researchers in choosing the most appropriate method for the planned development of experimental systems with regulated expression or activity of studied proteins.

Targeting the EGFR pathway for cancer therapy.

Clinical studies have shown that HER-2/Neu is over-expressed in up to one-third of patients with a variety of cancers, including B-cell acute lymphoblastic leukemia (B-ALL), breast cancer and lung cancer, and that these patients are frequently resistant to conventional chemo-therapies. Additionally, in most patients with multiple myeloma, the malignant cells over-express a number of epidermal growth factor receptors (EGFR)s and their ligands, HB-EGF and amphiregulin, thus this growth-factor family may be an important aspect in the patho-biology of this disease. These and other, related findings have provided the rationale for the targeting of the components of the EGFR signaling pathways for cancer therapy. Below we discuss various aspects of EGFR-targeted therapies mainly in hematologic malignancies, lung cancer and breast cancer. Beside novel therapeutic approaches, we also discuss specific side effects associated with the therapeutic inhibition of components of the EGFR-pathways. Alongside small inhibitors, such as Lapatinib (Tykerb, GW572016), Gefitinib (Iressa, ZD1839), and Erlotinib (Tarceva, OSI-774), a significant part of the review is also dedicated to therapeutic antibodies (e.g.: Trastuzumab/Herceptin, Pertuzumab/Omnitarg/rhuMab-2C4, Cetuximab/Erbitux/IMC-C225, Panitumumab/Abenix/ABX-EGF, and also ZD6474). In addition, we summarize, both current therapy development driven by antibody-based targeting of the EGFR-dependent signaling pathways, and furthermore, we provide a background on the history and the development of therapeutic antibodies.

Viral modulation of cell death by inhibition of caspases.

Caspases are key effectors of the apoptotic process. Some of them play important roles in the immune system, being involved in the proteolytic maturation of the key cytokines, including interleukin 1beta (IL-1beta) and IL-18. The latter directs the production of interferon gamma (IFN-gamma). Among pathogens, particularly viruses express various modulators of caspases that inhibit their activity by direct binding. By evading the apoptotic process, viruses can better control their production in the infected cell and avoid the attack of the immune system. Targeting the maturation of the key cytokines involved in the initiation of (antiviral) immune response helps to avoid recognition and eradication by the immune system. The three main classes of caspase inhibitors frequently found among viruses include serine proteinase inhibitors (serpins: CrmA/SPI-2), viral IAPs (vIAPs) and p35. Their molecular mechanisms of action, structures and overall influence on cellular physiology are discussed in the review below.