The relationship between cisplatin sensitivity and drug uptake into mammalian cells in vitro.

Clonogenic survival of HeLa, Chinese hamster and HaK cells after treatment with a range of cisplatin concentrations and exposure times was determined and cellular platinum concentrations were measured by PIXE. It was demonstrated that cisplatin cytotoxicity of the three cell lines varied considerably as a function of drug exposure dose. These differences are related to differential cellular drug uptake

Radiation-induced transient cisplatin resistance in murine fibrosarcoma cells associated with elevated metallothionein content.

Cisplatin resistant mouse fibrosarcoma cells were isolated after fractionated irradiation in the absence of any drug treatment. Several sublines have been established; clone SSK-rad1 was used for further studies. These cells exhibit unchanged radiosensitivity and are compared to cisplatin resistant sublines, SSK-cis2, previously induced by low dose cisplatin exposure. Both resistant sublines are characterised by reduced CdCl2 sensitivity, indicating enhanced metallothionein content; loss of cisplatin resistance occurs after 10 to 25 generations and correlates with rising CdCl2 toxicity. Increase of MT is demonstrated directly by 109Cd binding to the MT containing region after FPLC. Both sublines differ in GSH level, which is increased only in SSK-rad1 cells, and in cellular platinum content, which is reduced in SSK-cis2 cells compared to the parental SSK cell line. These factors may contribute to cisplatin resistance but are not the main cause responsible for the transient nature of the drug resistance observed. Our results indicate that transient cisplatin resistance in SSK cells can be induced not only by the drug itself but also by gamma-irradiation and is based on the same mechanism of increased cellular MT content

Turnover, account value and diversification of real traders: evidence of collective portfolio optimizing behavior

Despite the availability of very detailed data on financial market, agent-based modeling is hindered by the lack of information about real trader behavior. This makes it impossible to validate agent-based models, which are thus reverse-engineering attempts. This work is a contribution to the building of a set of stylized facts about the traders themselves. Using the client database of Swissquote Bank SA, the largest on-line Swiss broker, we find empirical relationships between turnover, account values and the number of assets in which a trader is invested. A theory based on simple mean-variance portfolio optimization that crucially includes variable transaction costs is able to reproduce faithfully the observed behaviors. We finally argue that our results bring into light the collective ability of a population to construct a mean-variance portfolio that takes into account the structure of transaction costsComment: 26 pages, 9 figures, Fig. 8 fixe

The Anti-Apoptotic Activity of BAG3 Is Restricted by Caspases and the Proteasome

Caspase-mediated cleavage and proteasomal degradation of ubiquitinated proteins are two independent mechanisms for the regulation of protein stability and cellular function. We previously reported BAG3 overexpression protected ubiquitinated clients, such as AKT, from proteasomal degradation and conferred cytoprotection against heat shock. We hypothesized that the BAG3 protein is regulated by proteolysis. caspase-resistant mutant. Caspase and proteasome inhibition resulted in partial and independent protection of BAG3 whereas inhibitors of both blocked BAG3 degradation. STS-induced apoptosis was increased when BAG3 was silenced, and retention of BAG3 was associated with cytoprotection.BAG3 is tightly controlled by selective degradation during STS exposure. Loss of BAG3 under STS injury required sequential caspase cleavage followed by polyubiquitination and proteasomal degradation. The need for dual regulation of BAG3 in apoptosis suggests a key role for BAG3 in cancer cell resistance to apoptosis

LPA Is a Chemorepellent for B16 Melanoma Cells: Action through the cAMP-Elevating LPA5 Receptor

Lysophosphatidic acid (LPA), a lipid mediator enriched in serum, stimulates cell migration, proliferation and other functions in many cell types. LPA acts on six known G protein-coupled receptors, termed LPA1–6, showing both overlapping and distinct signaling properties. Here we show that, unexpectedly, LPA and serum almost completely inhibit the transwell migration of B16 melanoma cells, with alkyl-LPA(18∶1) being 10-fold more potent than acyl-LPA(18∶1). The anti-migratory response to LPA is highly polarized and dependent on protein kinase A (PKA) but not Rho kinase activity; it is associated with a rapid increase in intracellular cAMP levels and PIP3 depletion from the plasma membrane. B16 cells express LPA2, LPA5 and LPA6 receptors. We show that LPA-induced chemorepulsion is mediated specifically by the alkyl-LPA-preferring LPA5 receptor (GPR92), which raises intracellular cAMP via a noncanonical pathway. Our results define LPA5 as an anti-migratory receptor and they implicate the cAMP-PKA pathway, along with reduced PIP3 signaling, as an effector of chemorepulsion in B16 melanoma cells