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Over the last 50 years, drug development and clinical trials have resulted in successful complete responses in diseases such as childhood leukemia, testicular cancer and Hodgkin's disease. We are still, however, confronted with over 500,000 cancer-related deaths per year. Clearly, the phenomenon of drug resistance is largely responsible for these failures and continues to be an area of active investigation. Since the last volume in this series, we have learned that the energy-dependent drug efflux protein, p-glycoprotein, encoded by the MDR 1 gene, is a member of a family of structurally related transport polypeptides, thus allowing us to explore the relationship between structure and function. In addition to ongoing well designed clinical trials aimed at reversing MDR mediated drug resistance, the first gene therapy studies with the MDR 1 gene retrovirally transduced into human bone marrow cells are about to be initiated. Although MDR is currently the most understood mechanism of drug resistance, we are uncovering increasing knowledge of alternative molecular and biochemical mechanisms of drug resistance to antimetabolites, cisplatin and alkylating agents and developing new strategies for circumventing such resistance. It is clear that drug resistance is complex, and many mechanisms exist by which cancer cells may overcome the cytotoxicity of our known chemotherapeutic agents. As our understanding of each of these mechanisms expands, well designed models will be necessary to test laboratory hypotheses and determine their relationship to drug resistance in humans. It is this integration of basic science and clinical investigation that will both advance our scientific knowledge and result in the improvement of cancer therapy.
It was estimated that in 2008, 1,437,180 patients would receive a new cancer diagnosisand 565,650individualswould die of cancer (Jemal et al. 2008).Since the vast majority of patients dying of cancer will have had anticancer therapy, both c- ventional chemotherapy and novel targeted therapy, it can be concluded that these patients are dying with drug resistant cancer. The term multidrug resistance is also apt – in that these patients die after having undergone multiple rounds of different and structurally unrelated cancer therapies. However, for some, the concept of m- tidrug resistance is a worn out idea, stemming from disappointment with the drug resistancereversalstrategiesthatwerecarriedoutinthe1990susingpumpinhibitors to block drug resistance mediated by P-glycoprotein, product of the MDR-1 gene. However, if one takes the larger de?nition – multidrug resistance as simultaneous resistance to multiple structurally unrelated anticancer therapies – its existence c- not be denied. The purpose of this book is to explore new concepts related to drug resistance in cancer, including resistance to the new molecularly targeted agents. Perhaps new terminology is needed for resistance that occurs following therapy with the targeted agents: Novel Targeted Agent Resistance (NTR). Alternatively, we can return to the original de?nition of multidrug resistance as simply the res- tance to multipleagents that occurs in the course of normalcancer progression.This resistance is likely to be mediated by many factors.
The importance of drug resistance in cancer chemotherapy cannot be over stated. The 500,000 patients who die every year from cancer in the United States have, in most cases, been treated with chemotherapy. Many of these patients responded initially to chemotherapy, but death resulted from the development of drug-resistant tumors. In the first volume in the series. Drug Resistance in Chemotherapy the results of comprehensive laboratory studies aimed at understanding the mechanisms for resistance to individual agents and to the development of broad cross-resistance were described. In the past 2 years there has been substantial progress in understanding the molecular biology associated with these mechanisms of drug resistance. For the first time we are starting to understand which mechanisms are playing an im portant role in human tumors, and even more importantly, clinical trials have recently been initiated in an effort to reverse specific forms of drug resistance. The purpose of this volume is to describe the new advances, both at the molecular level and in the clinic regarding mechanisms of drug resistance and potential ways this resistance can be circumvented. This volume is focused upon mechanisms of resistance associated with two major classes of anticancer drugs: alkylating agents (including cisplatin) and the natural products (e. g. , adriamycin and vinblastine). The first section of the book describes new insights into the genetic mechanisms associated with drug resistance.
Chemotherapy is one of the major treatment options for cancer patients; however, the efficacy of chemotherapeutic management of cancer is severely limited by multidrug resistance, in that cancer cells become simultaneously resistant to many structurally and mechanistically unrelated drugs. In the past three decades, a number of mechanisms by which cancer cells acquire multidrug resistance have been discovered. In addition, the development of agents or strategies to overcome resistance has been the subject of intense study. This book contains comprehensive and up-to-date reviews of multidrug resistance mechanisms, from over-expression of ATP-binding cassette drug transporters such as P-glycoprotein, multidrug resistance-associated proteins, and breast cancer resistance p- tein to the drug ratio-dependent antagonism and the paradigm of cancer stem cells. The book also includes strategies to overcome multidrug resistance, from the development of compounds that inhibit drug transporter function to the modulation of transporter expression. In addition, this book contains techniques for the detection and imaging of drug transporters, methods for the investigation of drug resistance in animal models, and strategies to evaluate the efficacy of resistance reversal agents. The book intends to provide a state-of-the-art collection of reviews and methods for both basic and clinician investigators who are interested in cancer multidrug resistance mechanisms and reversal strategies. Tianjin, China Jun Zhou v Contents Preface. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v Contributors. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ix 1 Multidrug Resistance in Cancer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Bruce C. Baguley 2 Multidrug Resistance in Oncology and Beyond: From Imaging of Drug Efflux Pumps to Cellular Drug Targets . . . . . . . . . . . . . . . . . . . . . . . . . .
Cancer remains a major public health problem, representing the second leading cause of death worldwide. Amongst the different type of cancer, pancreatic ductal adenocarcinoma (PDAC) is one of the most lethal forms in humans, due to late diagnosis and limited treatment possibilities. Therefore, improved treatments for PDAC patients are urgently warranted. Similarly, mesothelioma is a rare but aggressive disease, difficult to diagnose for the long latency period before clinical signs. The standard therapeutic approaches include surgery, chemotherapy, and radiation. However, the overall median survival is about one year. Another global health issue is represented by drug-resistant infections, accounting for hundreds of thousands of deaths worldwide. The present dissertation aims to evaluate novel approaches to counteract drug resistance, a major cause of failure for both conventional chemotherapy and standard antimicrobial agents.
MULTI-DRUG RESISTANCE IN CANCER The book details the mechanisms underlying multi-drug cellular resistance and the targets of novel chemotherapeutic agents. Cancer is a major killer all over the world. Even with all the progress made, chemotherapy is still the mainstay of modern cancer treatment. The progression of the cellular defeat of numerous independent anticancer drugs in terms of their chemical structure is a major barrier to successful chemotherapy. Multi-drug resistance (MDR) is a term for the fact that most cancer patients exhibit this phenomenon. According to the numbers, drug resistance carries the blame for 90% of cancer patient deaths. Refractory cancer and tumor recurrence are common outcomes of prolonged chemotherapy. Because of the prevalence of drug-resistance mutations, the difficulty of treating tumors increases and the therapeutic efficacy of drugs decreases. Multi-Drug Resistance in Cancer: Mechanism and Treatment Strategies contains nine chapters that cover topics such as: studying the mechanics of resistance to drugs by autophagy; studies to delineate the role of efflux transporters; expression of drug transporters; resistance to targeted therapies in breast cancer; advances in metallodrug driven combination treatment for cancer; and use of natural agents for the overcoming of cancer drug resistance. The book aims to provide the latest data on the mechanisms of cellular resistance to anticancer agents currently used in clinical treatment. It provides a better understanding of the mechanisms of MDR and targets of novel chemotherapy agents which should guide future research concerning new effective strategies in cancer treatment. Audience This book is written for pharmaceutical and biomedical scientists and researchers at both the bench and in the clinic who are interested in the mechanisms and strategies for overcoming cancer’s multi-drug resistance.
Advances in Anticancer Agents in Medicinal Chemistry is an exciting eBook series comprising a selection of updated articles previously published in the peer-reviewed journal Anti-Cancer Agents in Medicinal Chemistry. The first volume gathers reviews of many classes of drugs of contemporary interest for cancer therapy and is devoted to small molecules inhibitors of various proteins involved in cancer development such as Casein kinase 2 (CK2), Protein kinase B (PKB), mTOR, Hsp90, P-glycoprotein (P-gp), Kinesin spindle protein (KSP), Cyclooxygenase 2 (COX-2), Histone deacetylase enzymes (HDACs) and Topoisomerase I. Advances in Anticancer Agents in Medicinal Chemistry will be of particular interest to readers interested in anti cancer drug therapy as the series provides additional value to scientific research by entailing an approach of bringing relevant reviews up-to-date and thus more valuable for reference purposes.
Basic scientific background Breast cancer is one of the most common cancer and the most frequent cause of cancer death among women worldwide. Currently, subtyping breast cancers into hormone receptor (HR) positive, human epidermal growth factor receptor-2 overexpressing (HER2+), and triple negative breast cancer (TNBC) is the basis of diagnosing and treating this disease. The main treatment strategies for breast cancer include surgery, endocrine therapy, molecular targeted therapy, chemotherapy, radiotherapy, immunotherapy and gene therapy. However, resistance of breast cancer cells to chemotherapeutic agents, molecular targeted therapies and immunotherapy may occur either intrinsically or de nova, and is often ultimately responsible for treatment failure. Therefore, drug resistance poses a major challenge to breast cancer treatment. Current developments: Drug resistance in breast cancer is a complex clinical condition originating from a wide range of molecular alterations. The development of endocrine therapy resistance is believed to be associated with many cellular changes, such as ESR1 gene mutations, bypassing estrogen signaling pathway and altered tamoxifen metabolism. Meanwhile, changes in immune response, alternation of drug-binding property and downstream pathways are involved in the mechanisms of drug resistance in HER2+ breast cancer. In addition, resistance to chemotherapeutic agents predominantly arises from increased drug efflux and cross resistance. Current studies suggest that treatment strategies and therapeutics have to be designed specifically to each patient in different clinical situations. The use of modern genomic, proteomic and functional analytical techniques has contributed to identify novel genes and signaling networks involved in breast cancer drug resistance. Moreover, the use of high-throughput techniques in combination with bioinformatics and systems biology approaches has aided the interrogation of clinical samples and allowed the identification of molecular signatures and genotypes that predict responses to certain drugs. Despite much progress has been made in the field of breast cancer drug resistance, such as combination therapy and drug-loaded nanoparticles, the complexity and variability of drug resistance mechanism still inevitably lead to the continuous occurrence of drug resistance. Therefore, with the increasing amounts of anti-breast cancer agents, there are now unprecedented opportunities to understand and overcome drug resistance through further research into mechanisms and corresponding strategies, which will help achieve lasting disease control and bring survival benefits to patients with advanced cancer. Papers of interest: The current Research Topic of Frontiers in Pharmacology focuses on publishing Original Research, Review articles and Case Reports focusing on (a) elucidating mechanisms of drug resistance in breast cancer, target mutations, tumor microenvironment, undiscovered genes and signaling pathways; (b) promising drug delivery systems that can enhance the sensitivity of anti- breast cancer agents to various tumors; (c) strategies that can improve patient care during bio-chemotherapeutic treatments; (d) small molecule compounds that are effective against drug-resistant breast tumors (e) biomarkers of chemotherapy resistance in breast cancer patients and (f) in vitro and in vivo models. Guidelines for article of submission: - Authors must stick to the set guidelines for ethical practices by the Frontiers journals. - The main content of the article must have certain innovation and research significance. - The authors should describe the construction method of drug-resistant cell lines when using them for experiments in the article.
More than 40 years ago, the observation that doxorubicin-resistant tumor cells were cross-resistant to several structurally different anticancer agents was the first step in the discovery of P-glycoprotein (P-gp). P-gp belongs to the superfamily of ATP-binding cassette (ABC) transporters;its overexpression has become a therapeutic target for overcoming multidrug resistance in tumors. However, P-gp is also expressed in cells of normal tissues where it plays a physiological role, by protecting them from the toxic effects of xenobiotics. Also, ABCB1 gene polymorphisms may influence the response to anticancer drugs substrate of P-gp. Several strategies to overcome P-gp tumor drug resistance have been suggested. P-gp 'circumvention’ is the most explored and is based on the coadministration of anticancer agents and pump inhibitors (P-gp modulators). Despite the positive findings obtained in preclinical studies, results of clinical trials are not yet successful and clinical research is still ongoing. Other investigational approaches have been studied (e.g. P-gp targeting antibodies, use of antisense strategies or transcriptional regulators targeting ABCB1 gene expression) but their use is still circumscribed to the preclinical setting. A further approach is represented by the encapsulation of P-gp substrate anticancer drugs into liposomes or nanoparticles. This strategy has shown higher efficacy in tumor previously treated with the free drug. The reasons explaining the increased efficacy of liposomal/nanoparticle-based drugs in Pgp-overexpressing tumors include the coating with specific surfactants, the composition changes in the plasma membrane microdomains where P-gp is embedded, the direct impairment of P-gp catalytic mechanisms exerted by specific component of the liposomal shell, but are not yet fully understood. A second strategy to overcome P-gp tumor drug resistance is represented by exploiting the P-gp presence. Actually, P-gp-overexpressing cells show increased sensitivity (collateral sensitivity) to some drugs (e.g. verapamil, narcotic analgesics) and to some investigational compounds (e.g. NSC73306). P-gp-overexpressing cell are hypersensitive to reactive oxygen species, to agents perturbing the energetic metabolic pathways, changing the membrane compositions, reducing the efflux of endogenous toxic catabolites. However, the mechanisms explaining collateral sensitivity have not been fully elucidated. Another approach to exploit P-gp is represented by ABCB1 gene transfer to transform bone marrow progenitor cells into a drug resistant state which may allow conventional or higher doses of anticancer drug substrates of P-gp to be administered safely after transplantation. More recently the development and introduction in the clinics of anticancer drugs which are not substrates of P-gp (e.g. new microtubule modulators, topoisomerase inhibitors) has provided a new and promising strategy to overcome P-gp tumor drug resistance (P-gp 'evasion'). This ‘research topic’ issue aims at exploding the above mentioned matters, in particular by: -retracing the history of the first researches on P-gp - describing the physiological role of P-gp - describing the molecular basis, structural features and mechanism of action of P-gp - describing diagnostic laboratory methods useful to determine the expression of P-gp and its transporter function - describing strategies to overcome tumor drug resistance due to P-gp and other ABC transporters - indicating novel approaches to overcome P-gp multidrug resistance, ranging from basic research studies to pre-clinical/clinical studies.