Asfar S. Azmi

Prior exposure to restraint stress enhances 7,12‐dimethylbenz(a)anthracene (DMBA) induced DNA damage in rats

Over the years, several lines of evidence have emerged supporting the role of stress in the development and progression of cancer. Stress can cause an increase in the production of reactive oxygen species (ROS) and decrease in the in vivo antioxidant defense systems. A ROS‐induced DNA damage in peripheral lymphocytes, liver and skin cells may be revealed by Comet assay. To test whether DNA is damaged by stress/DMBA/stress and DMBA, rats were exposed to multiple doses of DMBA in the presence and absence of restraint stress, and DNA damage was evaluated. Insignificant differences were detected in all the three cells tested (peripheral lymphocytes, liver and skin cells) between control and stress treatment in terms of frequencies of damaged DNA. The extent of DNA migration was enhanced in DMBA treated rats in a dose dependent manner. Pre‐stress DMBA treatment showed still higher frequencies of damage in comparison with control, stress alone or DMBA alone groups. Thus, prior exposure to stress clearly enhanced the DMBA induced DNA damage, especially so in the skin cells (target organ of the carcinogen application) than liver and peripheral lymphocytes as observed on the basis of the extent of DNA migration (tail DNA) during single cell gel electrophoresis.

Understanding XPO1 Target Networks Using Systems Biology and Mathematical Modeling

The nuclear transport protein Exportin 1 (XPO1), also called chromosome region maintenance 1 (CRM1), is over-expressed 2- 4 fold in cancer. XPO1 is one of seven nuclear exporter proteins, and is solely responsible for the transport of the major tumor suppressor proteins (TSPs) from the nucleus to the cytoplasm. XPO1 exports any protein that carries a leucine-rich, hydrophobic nuclear export sequence (NES). A number of inhibitors have been discovered that block XPO1 function and thereby restore TSPs to the nucleus of both malignant and normal cells. However, natural product, irreversible XPO1 antagonists such as leptomycin B (LMB) have proven toxic in both preclinical models and in the clinic. Recently, orally bioavailable, drug-like small molecule, potent and selective inhibitors of XPO1 mediated nuclear export (SINE) have been designed and are undergoing clinical evaluations in both humans and canines with cancer. The breadth of clinical applicability and long-term viability of an XPO1 inhibition strategy requires a deeper evaluation of the consequence of global re-organization of proteins in cancer and normal cells. Unfortunately, most of the studies on XPO1 inhibitors have focused on evaluating a limited number of TSPs or other proteins. Because XPO1 carries ~220 mammalian proteins out of the nucleus, such reductionism has not permitted a global understanding of cellular behavior upon drug-induced disruption of XPO1 function. The consequence of XPO1 inhibition requires holistic investigations that consider the entire set of XPO1 targets and their respective pathways modulated without losing key details. Systems biology is one such holistic approach that can be applied to understand XPO1 regulated proteins along with the downstream players involved. This review provides comprehensive evaluations of the different computational tools that can be utilized in the better understanding of XPO1 and its target. We anticipate that such holistic approaches can allow for the development of a clinically successful XPO1 targeted therapeutic strategy against cancer.

Systems and Network Understanding of Cancer Stem Cells

The notion that tumors arise from a rare population of cells with stem cell characteristics was first proposed more than a century ago when pathologists like Virchow and Cohnheim formulated the hypothesis that cancer results from the activation of embryonic-tissue remnants (Weiss 2000). Since then, advances in different fields have provided support to this original proposal that has led to the increasingly accepted yet controversial “cancer stem cell (CSC)” hypothesis that explains the development of multiple forms of human cancers (Wicha et al. 2006). The first experiments indicating the existence of these cells were performed in animal models in the 1970s where it was concluded that only a low percentage of transplanted murine lymphoma cells formed colonies in the spleen of recipient animals (Park et al. 1971a; Bruce and VAN DER 1963). Likewise, only a minimum number (1 in 100 to 1 in 100,000) of murine myeloma cells were able to form colonies in

An Overview of Proteomics Techniques and its Application as a Tool in Biomarker and Drug Discovery

Introduction: Proteomics technology is extensively used to identify the underlying molecular mechanisms of various diseases. Emergent technologies in proteomics have been used in the biomarker and drug discovery process. Proper use of this technology can enable the understanding of mechanism of drug action; efficacy and toxicity, there by facilitating effective translation of the drug from bench to bedside. nAreas covered: The major techniques used in proteomics technology with an application in drug discovery process are discussed. An overview on different kinds of proteomic approaches and their application in various fields of biomarker discovery as well as drug development process has also been presented. nConclusions: Proteomics technology serves as a promising approach by providing unbiased information about protein-protein interactions, post-translational modifications and regulatory mechanisms. Owing to the complexity of the proteomes the technology needs to be complemented with other omics techniques which could revolutionize drug development process. Advanced instrumentation with improved sensitivity, selectivity coupled with efficient proteomics work flows can facilitate comprehensive characterization of various proteomes for potential drug targets

Systems and Network-Centric Understanding of Pancreatic Ductal Adenocarcinoma Signalling

Pancreatic ductal adenocarcinoma (PDAC) is a deadly disease that is intractable to currently available treatment modalities (Vincent et al. 2011). Failure of standard chemo-, radioand neoadjuvant single pathway targeted therapies indicate that before newer treatment regimens are designed, one has to re-visit the basic understanding of the origins and complexity of PDAC. As such, PDAC is now appreciated to have not only a highly heterogeneous pathology but is also a disease characterized by dysregulation of multiple pathways governing fundamental cell processes (Kim and Simeone 2011). Such complexity has been suggested to be governed by molecular networks that execute metabolic or cytoskeletal processes, or their regulation by complex signal transduction originating from diverse genetic mutations (Figure 1). A major challenge, therefore, is to understand how to develop actionable modulation of this multivariate dysregulation, with respect to both how it arises from diverse genetic mutations and to how it may be ameliorated by prospective treatments in PDAC. Lack of understanding in both these areas is certainly a major underlying reason for failure of most of the available and clinically used drugs (Stathis and Moore 2010). The pharmaceutical industry handpicked drugs have been generally based on their specificity towards a particular protein and the subsequent targeted pathway (K-Ras, PI3K, MEK, EGFR, p53 etc) without considering the effect of modulating secondary and interacting pathways (Almhanna and Philip 2011; Philip 2011). However, as results from integrated network modeling and systems biology studies indicate, targeting one protein is not straightforward as each protein in a cellular system works in a complex interacting network comprised of a myriad interconnected pathways (Wist et al. 2009a). Silencing one protein/pathway can have multiple effects on different secondary pathways leading to secondary effects. For example, activation of salvage pathways (commonly observed in PDAC) can result in diminished drug response or in some cases acquired resistance. Therefore, in order to decode this complexity and to understand both the PDAC disease and identify drug targets, it requires a departure from a protein-centric to a more advanced network-centric view. This chapter deals with recent advancements on deciphering PDAC disease networks and drug response networks based on integrated systems and network biology-driven science. It is believed that such integrated and holistic approach will help in not only delineating the mechanism of resistance of this complex disease, it will also aid in the future design of targeted drug combinations that will improve the dismal cure rate.

p53 Re-Activating Small Molecule Inhibitors for the Treatment of Pancreatic Cancer

Pancreatic ductal adenocarcinoma (PDAC) devours two American lives every 30 minutes (annual death rate >37,000) and is the fourth leading cause of cancer-related deaths in the US (Jemal et al. 2010). Median survival is 4 to 6 months and the 5-year survival is less than 5% (Baxter et al. 2007). The standard chemotherapeutic agent gemcitabine shows dismal response rate and has little impact. Recently, clinicians have incorporated platinum-based genotoxic regimens such as oxaliplatin nevertheless such combinations have little impact on improving the overall survival of PDAC patients (Wang et al. 2011). There are critical unanswered questions regarding the mechanism of drug failure in PDAC and investigations are still a long way from identifying novel drug combination regimens to achieve cure. Therefore, management of PDAC is an ongoing challenge and novel clinically-translatable therapeutic agents that can improve on the dismal survival statistics of PDAC are urgently needed.