Sonsoles Shack

Loss in oxidative stress tolerance with aging linked to reduced extracellular signal-regulated kinase and Akt kinase activities

Oxidative stress is believed to be an important factor in the development of age‐related diseases, and studies in lower organisms have established links between oxidative stress tolerance and longevity. We have hypothesized that aging is associated with a reduced ability to mount acute host defenses to oxidant injury, which increases the vulnerability of aged cells to stress. We tested this hypothesis by using primary hepatocytes from young (4‐6 months) and aged (24‐26 months) rats. Old hepatocytes were more sensitive to H2O2‐induced apoptosis than were young cells. Lower survival was associated with reduced activations of extracellular signal‐regulated kinase (ERK) and Akt kinase, both of which protect against oxidant injury. That reduced ERK and Akt activities contribute to lower survival of aged cells was supported by additional findings. First, pharmacologic inhibition of ERK and Akt activation in young cells markedly increased their sensitivity to H2O2. Second, caloric restriction, which increases rodent life span and delays the onset of many age‐related declines in physiologic function, prevented loss in ERK and Akt activation by H2O2 and enhanced survival of old hepatocytes to levels similar to those of young cells. Strategies aimed at boosting these host responses to acute oxidant injury could have significant anti‐aging benefits.

Cytostatic activity of phenylacetate and derivatives against tumor cells: Correlation with lipophilicity and inhibition of protein prenylation

The aromatic fatty acid phenylacetate, a common metabolite of phenylalanine, shows promise as a relatively non-toxic drug for cancer treatment. This slowly metabolized fatty acid alters tumor cell lipid metabolism causing, among other effects, inhibition of protein prenylation critical to malignant growth. In pursuit of more potent analogues, we have examined the activity of related compounds against tumor cell lines established from patients with advanced prostatic carcinoma, glioblastomas, and malignant melanoma. Like phenylacetate, derivatives containing alpha-carbon or ring substitutions induced cytostasis and phenotypic reversion at non-toxic concentrations. Potency was correlated with the degree of calculated lipophilicity of the aromatic fatty acid, and the extent of inhibition of protein prenylation. Remarkably, a parallel cytostatic activity was reported in embryonic plant cells, which respond to phenylacetate and its analogues in the same concentration range and the same rank order of lipophilicity. These data suggest that phenylacetate and its analogues may act through common mechanisms to inhibit the growth of vastly divergent, undifferentiated cell types, and provide a basis for the development of new agents for the treatment of human malignancies.

Gene expression profiling-based identification of cell-surface targets for developing multimeric ligands in pancreatic cancer

Multimeric ligands are ligands that contain multiple binding domains that simultaneously target multiple cell-surface proteins. Due to cooperative binding, multimeric ligands can have high avidity for cells (tumor) expressing all targeting proteins and only show minimal binding to cells (normal tissues) expressing none or only some of the targets. Identifying combinations of targets that concurrently express in tumor cells but not in normal cells is a challenging task. Here, we describe a novel approach for identifying such combinations using genome-wide gene expression profiling followed by immunohistochemistry. We first generated a database of mRNA gene expression profiles for 28 pancreatic cancer specimens and 103 normal tissue samples representing 28 unique tissue/cell types using DNA microarrays. The expression data for genes that encode proteins with cell-surface epitopes were then extracted from the database and analyzed using a novel multivariate rule-based computational approach to identify gene combinations that are expressed at an efficient binding level in tumors but not in normal tissues. These combinations were further ranked according to the proportion of tumor samples that expressed the sets at efficient levels. Protein expression of the genes contained in the top ranked combinations was confirmed using immunohistochemistry on a pancreatic tumor tissue and normal tissue microarrays. Coexpression of targets was further validated by their combined expression in pancreatic cancer cell lines using immunocytochemistry. These validated gene combinations thus encompass a list of cell-surface targets that can be used to develop multimeric ligands for the imaging and treatment of pancreatic cancer. [Mol Cancer Ther 2008;7(9):3071–80]

Tracking transcriptional activities with high-content epifluorescent imaging

High-content cell imaging based on fluorescent protein reporters has recently been used to track the transcriptional activities of multiple genes under different external stimuli for extended periods. This technology enhances our ability to discover treatment-induced regulatory mechanisms, temporally order their onsets and recognize their relationships. To fully realize these possibilities and explore their potential in biological and pharmaceutical applications, we introduce a new data processing procedure to extract information about the dynamics of cell processes based on this technology. The proposed procedure contains two parts: (1) image processing, where the fluorescent images are processed to identify individual cells and allow their transcriptional activity levels to be quantified; and (2) data representation, where the extracted time course data are summarized and represented in a way that facilitates efficient evaluation. Experiments show that the proposed procedure achieves fast and robust image segmentation with sufficient accuracy. The extracted cellular dynamics are highly reproducible and sensitive enough to detect subtle activity differences and identify mechanisms responding to selected perturbations. This method should be able to help biologists identify the alterations of cellular mechanisms that allow drug candidates to change cell behavior and thereby improve the efficiency of drug discovery and treatment design.

DYNAMICAL ANALYSIS OF DRUG EFFICACY AND MECHANISM OF ACTION USING GFP REPORTERS

Two issues are critical to the development of effective cancer-drug combinations. First, it is necessary to determine common combinations of alterations that exert strong control over proliferation and survival regulation for the general type of cancer being considered. Second, it is necessary to have a drug testing method that allows one to assess the variety of responses that can be provoked by drugs acting at key points in the cellular processes dictating proliferation and survival. Utilizing a previously reported GFP (green fluorescent protein) reporter-based technology that provides dynamic measurements of individual reporters in individual cells, the present paper proposes a dynamical systems approach to these issues. It involves a three-state experimental design: (1) formulate an oncologic pathway model of relevant processes; (2) perturb the pathways with the test drug and drugs with known effects on components of the pathways of interest; and (3) measure process activity indicators at various poin...

Gene Expression Profiling of Tissues and Cell Lines: A Dual-Color Microarray Method

Since its origin in the mid-1990s, gene expression profiling by microarray has become a productive and useful tool in basic science and preclinical research. Current dual-color, high-density cDNA oligo arrays contain 60-mer detectors for the whole human genome. With this powerful technology, expression of RNA samples from cell lines or tissue can be assessed, revealing specific gene expression signatures. The technique includes three major steps: (1) isolation and purification of RNA from cells or tissues, (2) labeling of total RNA, and (3) hybridization with Agilent cDNA microarrays. Conveniently, this technique can be performed with as little as 50 ng of purified total RNA; however, it is important to keep in mind that the quality of the RNA template, namely the level of sample degradation and the presence of contaminants that are carried over from the starting material or introduced during RNA isolation, can significantly impact the efficiency of the labeling reaction and the reliability of the hybridization. In this chapter, the details of each step of this technique are explained thoroughly, while highlighting the key issues that can prevent a failed hybridization.

Abstract LB-277: Dynamic functional analysis of the response of cancer cell lines to the drug UNBS1450

The analysis of the dynamics of cellular responses to drugs is currently bounded by inherent limitations of the methods most often used to assess levels of promoter activity and protein abundance or activation. The sensitivity of these assays is limited by the averaging of analyte over many cells, which can produce an average that is not accurately descriptive of the wide range of activities of members of the population examined. The ability of these assays to indicate the trajectory of the various responses is limited by a very infrequent sampling rate, frequently 2–4 time points spread over many hours. These limits are further exacerbated by populations of treated cells9 inhomogeneity in the timing of their own response to the drugs. To improve the determination of the functional dynamics of cells9 responses to drugs, PBS-Bio has developed technology that allows gathering data from living cells using fluorescent reporter technology. This technology allows measurements to be made serially on single populations of cells at the individual cell level, providing both high sensitivity in terms of when even a small fraction of the cells exhibit significant shifts of a particular activity, the rate of shift of cells in the population to this different activity and the ability to temporally order the timing of events relative to each other. Experimentation on two cell lines, A549 and PC3, using a variety of drugs that affect different cellular processes and a set of fluorescent reporters that provide information on a variety of cellular processes it was possible to show that the modified cardenolide drug, UNBS1450 (Unibioscreen), provoked a very early reduction in the expression of the MCL1 and MYC genes, followed by induction of a strong apoptotic response in both cell lines. As loss of MCL1 provoked by other means has been shown to be sufficient to induce apoptosis in both these lines, a very strong case can be made for UNBS14509s ability to provoke Mcl1 protein reduction as the drug9s mode of apoptotic induction. This finding would also implicate Mcl1 as a useful biomarker of the possible efficacy of UNBS1450. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr LB-277. doi:10.1158/1538-7445.AM2011-LB-277