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This volume presents a compendium of the most recent and advanced methods applied to the rapidly expanding field of telomerase inhibition. The techniques described provide the researcher with a diverse and comprehensive set of tools for the study of telomerase inhibition. The volume is aimed at biochemists, molecular biologists, cancer researchers, and geneticists.
Telomerase, an enzyme that maintains telomeres and endows eukaryotic cells with immortality, was first discovered in tetrahymena in 1985. In 1990s, it was proven that this enzyme also plays a key role in the infinite proliferation of human cancer cells. Now telomere and telomerase are widely accepted as important factors involved in cancer biology, and as promising diagnostic tools and therapeutic targets. Recently, role of telomerase in “cancer stem cells” has become another attractive story. Until now, there are several good books on telomere and telomerase focusing on biology in ciliates, yeasts, and mouse or basic sciences in human, providing basic scientists or students with updated knowledge.
Telomeres are essential functional elements of eukaryotic chromosomes. Their fundamental biological role as protectors of chromosome stability was identified for the first time in the 1930s by Hermann Muller and Barbara McClintock based on pioneering cytological experiments. Modern molecular research carried out more recently revealed that telomeres and telomerase play important roles in processes such as carcinogenesis and cellular senescence. This special issue presents the most recent developments in this highly active field of research. It is becoming increasingly clear that molecular pathways involved in regulation of telomere length and structure are functionally linked with pathways involved in DNA damage response, cellular stress response, chromatin organization and perhaps even pathways that regulate evolutionary chromosome rearrangements. The above functional link is explored by the leading experts in the field of telomere biology. Cell biologists, molecular biologists, oncologists, gerontologists, and radiobiologists with an interest in the role of telomeres/telomerase will appreciate the up-to-date information in this publication.
Telomerase is a target of intense scientific interest largely because of its implicated role in human carcinogenesis. The inactivation of this enzyme is widely believed to be a promising method to selectively destroy neoplastic cells, while leaving normal cells mostly unaffected. In this dissertation work, the inactivation of human telomerase by molecules based on nucleic acid intercalator structures is presented. The process of cell division shortens the distal portion of linear chromosomes (the telomere). Human telomerase, a special DNA polymerase which functions to maintain telomere length, is composed of RNA and protein subunits. Upon binding to its telomeric DNA substrate, a RNA/DNA heteroduplex is formed. The working hypothesis pursued here is that molecules which target this specific RNA/DNA heteroduplex will stabilize this structure and effectively stall telomerase polymerase activity. Since telomere maintenance is paramount for the survival of rapidly dividing cancer cells, the prevention of telomere maintenance, via inhibition of the telomerase enzyme, is a promising approach to cancer treatment. There are several other approaches to telomerase inhibition presented in the literature. However, targeting the RNA/DNA heteroduplex with the use of modified DNA intercalating agents is a novel and attractive approach to telomerase inhibition. A multifaceted methodology was undertaken to achieve the goal of producing specific inhibitors of human telomerase. First, commercially available nucleic acid intercalators were tested to obtain lead compounds with good inhibitory effect on telomerase activity. Secondly, utilizing techniques of enzyme kinetics, investigations were carried out to determine whether the telomerase RNA/DNA heteroduplex was the target of these lead compounds. Finally, the generation of more potent inhibitors of telomerase was attempted through the use of combinatorial peptide synthesis using lead intercalator(s) as the base structure. It was demonstrated in vitro, that more potent inhibitors of human telomerase could be developed by this approach. Using previously existing assay methods, in addition to original methods developed, relevant experiments were carried out to investigate the stated working hypothesis. During the course of these experiments many interesting observations were made, some of which were pursued and dealt with in these chapters.
We hypothesize that telomerase inhibition (telomere shortening) can sensitize human tumor cells to existing anticancer drugs. During the period of the grant we made the following findings-: 1) 2'-methoxy ethyl oligonucleotides inhibit - -telomerase in prostate cancer cells, cause telomeres to shorten, and cause cell- proliferation to decrease; -2) Cell proliferation in culture is -more pronounced when cells are grown under conditions that mimic tumor growth; 3) Cell proliferation is dramatically reduced in a xenograft model using LNCAP cells, and 4) We did not observe significant synergy with standard chemotherapy agents. The ability of relatively short-term treatments with telomerase inhibitors to slow tumor growth in vivo suggests that telomerase inhibitors are a reasonable approach to prostate cancer therapy.
This book is a comprehensive and up-to-date review and evaluation of the contemporary status of telomerase research. Chapters in this volume cover the basic structure, mechanisms, and diversity of the essential and regulatory subunits of telomerase. Other topics include telomerase biogenesis, transcriptional and post-translational regulation, off-telomere functions of telomerase and the role of telomerase in cellular senescence, aging and cancer. Its relationship to retrotransposons, a class of mobile genetic elements that shares similarities with telomerase and serves as telomeres in selected organisms, are also reviewed.
The fundamental problem that dividing cells have to ov- come is that of end-replication. Chromosomes shorten by many bases during DNA replication and so this presents a major hurdle that a cell has to overcome both to enable it to proliferate and for the larger organism to survive and reproduce. The enzyme telomerase provides a mechanism to ensure chromosome stability in both normal and neoplastic cells. The demonstration of telomerase expression in a majority of tumors and the realization of the potential role of telomerase in aging has opened up the potential for telomerase to be used as a target for therapeutic intervention. There is therefore great interest in the expression and activity of telomerase in a wide range of biological disciplines. Telomeres and Telomerase: Methods and Protocols has been produced as a tool for the many researchers in different areas of cell biology who are interested in following research in the area of telomerase and telomere maintenance, either in the area of fundamental mec- nisms or perhaps in the area of more applied drug discovery work.
Over the recent years, medicinal chemistry has become responsible for explaining interactions of chemical molecule processes such that many scientists in the life sciences from agronomy to medicine are engaged in medicinal research. This book contains an overview focusing on the research area of enzyme inhibitor and activator, enzyme-catalyzed biotransformation, usage of microbial enzymes, enzymes associated with programmed cell death, natural products as potential enzyme inhibitors, protease inhibitors from plants in insect pest management, peptidases, and renin-angiotensin system. The book provides an overview on basic issues and some of the recent developments in medicinal science and technology. Especially, emphasis is devoted to both experimental and theoretical aspect of modern medicine. The primary target audience for the book includes students, researchers, chemists, molecular biologists, medical doctors, pharmacologists, and professionals who are interested in associated areas. The textbook is written by international scientists with expertise in biochemistry, enzymology, molecular biology, and genetics, many of which are active in biochemical and pharmacological research. I would like to acknowledge the authors for their contribution to the book. We hope that the textbook will enhance the knowledge of scientists in the complexities of some medical approaches; it will stimulate both professionals and students to dedicate part of their future research in understanding relevant mechanisms and applications of pharmacology.
Telomerase, a ribonucleoprotein enzyme composed of an RNA template (hTR) and a catalytically active protein subunit (hTERT), synthesizes telomeres after cell divisions and is obligatory for continuous tumor cell proliferation as well as malignant progression of breast cancer cells. Telomerase is an attractive anti-cancer therapeutic agent because telomerase activity is present in over 90% of human breast cancers but is undetectable in most normal somatic cells. Traditional therapies (surgery, chemotherapy, radiotherapy, etc.) lack the ability to effectively control and cure breast cancer, primarily because residual cells are or become resistant to DNA damaging modalities including standard chemo- and radio-therapies. Since telomerase requires its associated hTR for repeat synthesis, we have chosen to use RNA interference as a method to inactivate hTR and hence telomerase. RNA interference (RNAI) has become a powerful tool for the analysis of gene function in that RNAI allows sequence specific inhibition of gene expression. Another protein we targeted is p21, which has long been established as a requirement for senescence. We wanted to further examine its relationship to senescence and apotosis, in an attempt to sensitize breast tumor cells more effectively.