201
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Abstract
Conventional intravenous chemotherapy regimens are toxic, cumbersome, and negatively affect patients' quality of life, with oral treatment preferable to most patients with cancer. Multiple myeloma is the second most common haematological malignant disease, but cannot be cured with conventional and high-dose chemotherapy. New oral treatments that target myeloma cells or bone marrow are being developed that are highly effective yet have low toxic effects, such as the immunomodulatory drugs thalidomide and lenalidomide. Several treatments in early development have shown antimyeloma activity, including: CHIR-258, which inhibits fibroblast growth factor receptor 3; NVP-ADW742, which inhibits insulin-like growth factor receptor 1; and PTK787, which inhibits vascular endothelial growth factor. Additional drugs aimed at switching off silenced genes include histone deacetylase inhibitors. The availability of these various oral treatments is hoped to improve regimens that, if used sequentially or in combination, offer the potential of making multiple myeloma a chronic disease, thereby extending patients' lifespans and improving quality of life.
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Affiliation(s)
- Gareth J Morgan
- Royal Marsden Hospital and Institute of Cancer Research, London, UK.
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202
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Perez OD, Nolan GP. Phospho-proteomic immune analysis by flow cytometry: from mechanism to translational medicine at the single-cell level. Immunol Rev 2006; 210:208-28. [PMID: 16623773 DOI: 10.1111/j.0105-2896.2006.00364.x] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Understanding a molecular basis for cellular function is a common goal of biomedicine. The complex and dynamic cellular processes underlying physiological processes become subtly or grossly perturbed in human disease. A primary objective is to demystify this complexity by creating and establishing relevant model systems to study important aspects of human disease. Although significant technological advancements over the last decade in both genomic and proteomic arenas have enabled progress, accessing the complexity of cellular interactions that occur in vivo has been a difficult arena in which to make progress. Moreover, there are extensive challenges in translating research tools to clinical applications. Flow cytometry, over the course of the last 40 years, has revolutionized the field of immunology, in both the basic science and clinical settings, as well as having been instrumental to new and exciting areas of discovery such as stem cell biology. Multiparameter machinery and systems exist now to access the heterogeneity of cellular subsets and enable phenotypic characterization and functional assays to be performed on material from both animal models and humans. This review focuses primarily on the development and application of using activation-state readouts of intracellular activity for phospho-epitopes. We present recent work on how a flow cytometric platform is used to obtain mechanistic insight into cellular processes as well as highlight the clinical applications that our laboratory has explored. Furthermore, this review discusses the challenges faced with processing high-content multidimensional and multivariate data sets. Flow cytometry, as a platform that is well situated in both the research and clinical settings, can contribute to drug discovery as well as having utility for both biomarker and patient-stratification.
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Affiliation(s)
- Omar D Perez
- The Baxter Laboratory for Genetic Pharmacology, Department of Microbiology and Immunology, Stanford University, School of Medicine, Stanford, CA 94305, USA.
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203
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Ribatti D, Nico B, Vacca A. Importance of the bone marrow microenvironment in inducing the angiogenic response in multiple myeloma. Oncogene 2006; 25:4257-66. [PMID: 16518413 DOI: 10.1038/sj.onc.1209456] [Citation(s) in RCA: 122] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Tumor microenvironment is essential for tumor cell proliferation, angiogenesis, invasion and metastasis through its provision of survival signals, secretion of growth and pro-angiogenic factors, and direct adhesion molecule interactions. This review examines its importance in the induction of an angiogenic response in multiple myeloma (MM). The encouraging results of preclinical and clinical trials in which MM has been treated by targeting the tumor microenvironment are also discussed.
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Affiliation(s)
- D Ribatti
- Department of Human Anatomy and Histology, University of Bari Medical School, Italy.
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204
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Höglund M. Bladder cancer, a two phased disease? Semin Cancer Biol 2006; 17:225-32. [PMID: 16574430 DOI: 10.1016/j.semcancer.2006.02.002] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2006] [Revised: 02/16/2006] [Accepted: 02/17/2006] [Indexed: 10/25/2022]
Abstract
The processes of intraepithelial migration, intraluminal seeding, and field cancerization as models for initiation, spread, and recurrences of urothelial cell carcinoma (UCC) are reviewed in light of recent molecular investigations. The accumulated molecular data on synchronous and metachronous tumors indicate that the majority of recurrent and multiple tumors are monoclonal. Molecular data has also shown the presence of chromosomal and genetic changes in precursor lesions as well as in normal urothelial cells. Genetic-histological mapping of cystectomized bladders has shown that overt tumors occur as local events in areas of genetically altered urothelium. A model is put forward in which the tumor process is initiated by genetically altered but histologically normal cells that produce fields of altered cells by intraepithelial displacement. By the accumulation of further genetic changes the fields of altered urothelium reaches a state of criticality, which locally may produce frank tumors.
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Affiliation(s)
- Mattias Höglund
- Department of Clinical Genetics, Lund University Hospital, Lund SE-221 81, Sweden.
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205
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Trudel S, Stewart AK, Rom E, Wei E, Li ZH, Kotzer S, Chumakov I, Singer Y, Chang H, Liang SB, Yayon A. The inhibitory anti-FGFR3 antibody, PRO-001, is cytotoxic to t(4;14) multiple myeloma cells. Blood 2006; 107:4039-46. [PMID: 16467200 DOI: 10.1182/blood-2005-10-4179] [Citation(s) in RCA: 118] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
The association of fibroblast growth factor receptor 3 (FGFR3) expression with t(4;14) multiple myeloma (MM) and the demonstration of the transforming potential of this receptor tyrosine kinase (RTK) make it a particularly attractive target for drug development. We report here a novel and highly specific anti-FGFR3-neutralizing antibody (PRO-001). PRO-001 binds to FGFR3 expressed on transformed cells and inhibits FGFR3 autophosphorylation and downstream signaling. The antibody inhibited the growth of FGFR3-expressing FDCP cells (IC(50) of 0.5 microg/mL) but not that of cells expressing FGFR1 or FGFR2, and potently inhibited FGFR3-dependent solid tumor growth in a mouse xenograft model. Furthermore, PRO-001 inhibited the growth of the FGFR3-expressing, human myeloma cell line, UTMC2. Inhibition of viability was still observed when cells were cocultured with stroma or in the presence of IL-6 or IGF-1. PRO-001 did not inhibit constitutive activation of K650E, G384D, and Y373C FGFR3 in myeloma cell lines and failed to inhibit the growth of these cells. Most importantly, however, PRO-001 induced cytotoxic responses in primary t(4;14)(+) MM samples with an increase in apoptotic index of 20% to 80% as determined by annexin V staining. The data demonstrate that PRO-001 is a potent and specific inhibitor of FGFR3 and deserves further study for the treatment of FGFR3-expressing myeloma.
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MESH Headings
- Animals
- Antibodies/pharmacology
- Cell Division/drug effects
- Cell Line, Tumor
- Cell Survival
- Chromosomes, Human, Pair 14
- Chromosomes, Human, Pair 4
- Cytotoxicity, Immunologic/drug effects
- Humans
- Mice
- Mice, Transgenic
- Multiple Myeloma/genetics
- Receptor, Fibroblast Growth Factor, Type 3/genetics
- Translocation, Genetic
- Transplantation, Heterologous
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Affiliation(s)
- Suzanne Trudel
- University Health Network, Princess Margaret Hospital, McLaughlin Centre of Molecular Medicine, 620 University Avenue, Rm 8204, Toronto, Ontario, Canada M5G 2C1.
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206
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Orlowski RZ. Initial Therapy of Multiple Myeloma Patients Who Are Not Candidates for Stem Cell Transplantation. Hematology 2006:338-47. [PMID: 17124081 DOI: 10.1182/asheducation-2006.1.338] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Abstract
Multiple myeloma patients deemed to not be candidates for high-dose therapy followed by stem cell rescue who nonetheless need chemotherapy have traditionally received an oral regimen combining melphalan and prednisone. With the advent of novel agents, however, such as immunomodulatory drugs and proteasome inhibitors that are active in the relapsed/refractory setting, there has been an impetus to incorporate these new options into front-line therapy. Several phase II studies have recently revealed that addition of either thalidomide, lenalidomide, or bortezomib to melphalan and prednisone increased the overall and complete response rates, albeit at the cost of some increased toxicity. Randomized phase III studies of melphalan and prednisone with thalidomide have already shown that, compared to melphalan and prednisone alone, the three-drug regimen prolonged time to progression and overall survival in this population, thereby defining a new standard of care. Moreover, our increasing knowledge of the molecular role that cytogenetic abnormalities play in the biology of multiple myeloma and our growing chemotherapeutic armamentarium are beginning to allow us to rationally select therapies based on these characteristics of each patient’s disease. Such a risk- and molecular-adapted strategy to the therapy of multiple myeloma promises to revolutionize and personalize our care of these patients and bring us closer to a cure for this disease.
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Affiliation(s)
- Robert Z Orlowski
- University of North Carolina at Chapel Hill, 22-003 Lineberger Comprehensive Cancer Center, Chapel Hill, NC 27599, USA.
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207
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Abstract
The receptor tyrosine kinase FLT3 is an important regulatory molecule in hematopoiesis and is expressed on the blasts in most cases of acute leukemia. Activating mutations of this receptor are present in roughly 30% of acute myeloid leukemia (AML) patients and are associated with a distinctly worse clinical outcome. Efforts to target this mutation and improve out-comes in this subgroup of AML patients have led to the investigation of several novel small-molecule FLT3 tyrosine kinase inhibitors. These compounds derive from a wide variety of chemical classes and differ significantly, both in their potency and in their selectivity. In this review, we discuss the results of preclinical, clinical, and correlative laboratory studies of FLT3 inhibitors in demonstrating how this field represents a truly translational enterprise with multiple ongoing interactions between the laboratory and the clinic.
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Affiliation(s)
- Mark Levis
- Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins, Baltimore, MD 21231, USA
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208
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Bisping G, Kropff M, Wenning D, Dreyer B, Bessonov S, Hilberg F, Roth GJ, Munzert G, Stefanic M, Stelljes M, Scheffold C, Müller-Tidow C, Liebisch P, Lang N, Tchinda J, Serve HL, Mesters RM, Berdel WE, Kienast J. Targeting receptor kinases by a novel indolinone derivative in multiple myeloma: abrogation of stroma-derived interleukin-6 secretion and induction of apoptosis in cytogenetically defined subgroups. Blood 2005; 107:2079-89. [PMID: 16278310 DOI: 10.1182/blood-2004-11-4250] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In multiple myeloma (MM), both vascular endothelial (VEGF) and basic fibroblast growth factor (bFGF) promote tumor growth and survival. We have used the novel indolinone BIBF 1000 to study effects of simultaneous inhibition of VEGF, FGF and transforming growth factor-beta on MM cells and their interactions with bone marrow stroma cells (BMSCs). Both, in the absence and presence of myeloma-stroma cell contacts, BIBF 1000 abrogated BMSC-derived secretion of interleukin-6 (IL-6). In addition, BIBF 1000 directly induced apoptosis in t(4;14)-positive cell lines as well as in CD138+ marrow cells from patients with t(4;14) myeloma. To a similar extent, BIBF 1000 induced apoptosis in MM.1S and MM.1R cells carrying the translocation t(14;16). In case of MM.1S and other dexamethasone-sensitive t(14;16) cell lines, BIBF 1000 and dexamethasone had additive proapoptotic effects. Induction of apoptosis by BIBF 1000 was associated with inhibition of the mitogen-activated protein kinases (MAPK) pathway in t(4;14) and inhibition of the phosphatidyl-inositol-3 kinase/AKT pathway in t(14;16) cells. Apoptotic effects did not occur in t(4;14)-or t(14;16)-positive MM cells carrying n- or k-Ras mutations. The data provide the rationale for clinical evaluation of this class of targeted kinase inhibitors in MM with focus on defined cytogenetic subgroups.
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Affiliation(s)
- Guido Bisping
- Department of Medicine/Hematology and Oncology, University of Muenster, Albert-Schweitzer-Str. 33, D-48129 Muenster, Germany
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209
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Chng WJ, Fonseca R. Risk Stratification of Patients with Newly Diagnosed Multiple Myeloma: Optimizing Treatment Based on Pretreatment Characteristics. ACTA ACUST UNITED AC 2005; 6:200-7. [PMID: 16354325 DOI: 10.3816/clm.2005.n.047] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Marked clinical and biologic heterogeneity exists in multiple myeloma (MM). Over the years, many prognostic factors have been identified and several prognostic systems have been proposed. The integration of data from international groups including patients treated with common modalities such as chemotherapy and high-dose therapy culminated in the International Staging System. Recently, genetic information has also been shown to include powerful prognostic factors across different treatment modalities. These advances have facilitated categorization of patients into different risk groups, particularly a subset of patients at high risk with short survival times after current standard therapy. The expanding armamentarium of effective treatments in MM also means that it is now possible to select treatments for patients based on their risk categories. This review will summarize the important prognostic factors identified to date, how they can be used to identify patients at high risk, and their clinical utility in relation to treatment optimization at diagnosis.
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Affiliation(s)
- Wee J Chng
- Division of Hematology/Oncology, Mayo Clinic, Scottsdale, AZ 85259, USA
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210
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Jaksic W, Trudel S, Chang H, Trieu Y, Qi X, Mikhael J, Reece D, Chen C, Stewart AK. Clinical Outcomes in t(4;14) Multiple Myeloma: A Chemotherapy-Sensitive Disease Characterized by Rapid Relapse and Alkylating Agent Resistance. J Clin Oncol 2005; 23:7069-73. [PMID: 16129840 DOI: 10.1200/jco.2005.17.129] [Citation(s) in RCA: 82] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Purpose To determine whether primary drug resistance or rapid relapse explains the poor prognosis seen in t(4;14)-positive multiple myeloma (MM). Patients and Methods A total of 131 patients treated with high-dose therapy (HDT) were assessed, of whom 19 were t(4;14) positive. We examined the presentation features, chemotherapy responsiveness at presentation and to salvage therapies at relapse, and overall survival outcomes. Results t(4;14)-positive patients had a predominance of the immunoglobulin A isotype (52.6%) but otherwise baseline characteristics were indistinguishable. After treatment with vincristine, doxorubicin, and dexamethasone or dexamethasone alone, 17 (89.7%) of the 19 patients achieved a partial response and 11 patients (57.9%) demonstrated an additional 50% reduction in paraprotein after HDT. Thus, t(4;14)-positive patients are chemotherapy sensitive; however, early progression was common, with 26% of patients progressing before HDT and a median progression-free survival after HDT of only 14.1 months. At relapse, a resistance to alkylating agents was evident, with no responses (zero of 11 patients) seen with conventional-dose alkylating agents. Salvage regimens using thalidomide and/or dexamethasone achieved at least minimal response in 59% of patients. The duration of response was short, however, with a median of only 4.7 months. The median overall survival after HDT was 24.2 months. Conclusion We conclude that t(4;14)-positive MM is chemotherapy sensitive but rapid relapse occurs. Resistance to alkylating agents is evident at relapse. The development of novel therapeutic agents is required, including the early clinical study of targeted fibroblast growth factor receptor 3 tyrosine kinase inhibitors, which have shown promise in preclinical studies.
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Affiliation(s)
- Wilfrid Jaksic
- Department of Medical Oncology and Hematology, Princess Margaret Hospital/University Health Network, University of Toronto, Toronto, Canada
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211
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Stewart AK, Fonseca R. Prognostic and Therapeutic Significance of Myeloma Genetics and Gene Expression Profiling. J Clin Oncol 2005; 23:6339-44. [PMID: 16155017 DOI: 10.1200/jco.2005.05.023] [Citation(s) in RCA: 104] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Molecular diagnostic tools and novel therapeutics now offer the potential for accurate prognostic and personalized treatment road maps for patients with multiple myeloma (MM). We will review the evidence and provide specific recommendations for routine clinical molecular genetic testing and use of such information to guide therapeutic decision making. In particular, the negative prognostic impact of specific IgH translocations such as the t(4;14), t(14;16), chromosome 13 deletion by conventional cytogenetics and loss of 17p13 by interphase fluorescence in situ hybridization are now established. Preliminary gene expression profiling studies have also demonstrated that individual genes (CSK1-B) or groups of genes can define prognosis with greater accuracy than conventional genetic markers and can provide pharmacogenomic and biologic insight into the pathophysiology, therapeutics, and future targets of myeloma. Importantly, we recommend that all clinical trials now adopt routine genetic testing and risk stratification.
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Affiliation(s)
- A Keith Stewart
- Hematology-Oncology, Room 3-008, Mayo Clinic College of Medicine, Scottsdale, AZ 85259, USA.
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212
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Abstract
The advent of new techniques, such as interphase fluorescence in situ hybridization, and, more recently, global array-based gene expression profiling, has accelerated genomic research in myeloma. Distinct biologic subtypes, characterized by unique genetic abnormalities with differing clinical outcomes, have been identified. The identification of these primary genetic defects, and the deregulated oncogenes and pathways in myeloma, has allowed for the development of more targeted therapies. This has led to the discovery of an increased number of active agents in the treatment of myeloma. Genetics also have prognostic importance in myeloma. Recent studies have elucidated a genetic prognostic hierarchy, and have enabled improved definition of the prognostic significance of their interactions. The current challenges are to: improve the dissection of the genetic heterogeneity of the disease; better define progression events; improve the risk stratification of patients; more accurately select patients who will respond well to a particular treatment; and develop more rational combinations of treatment. Genomics will have an important role to play in all of these goals.
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Affiliation(s)
- Wee J Chng
- Division of Hematology-Oncology, Mayo Clinic Scottsdale, Johnson Research Building, 13400 E Shea Blvd, AZ 85259, USA
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213
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Abstract
Urothelial carcinoma of the bladder is unique among epithelial carcinomas in its divergent pathways of tumorigenesis. Low-grade papillary tumours rarely become muscle-invasive and they frequently harbour gene mutations that constitutively activate the receptor tyrosine kinase-Ras pathway. By contrast, most high-grade invasive tumours progress to life-threatening metastases and have defects in the p53 and the retinoblastoma protein pathways. Correcting pathway-specific defects represents an attractive strategy for the molecular therapy of urothelial carcinomas.
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Affiliation(s)
- Xue-Ru Wu
- Department of Urology, New York University School of Medicine, New York, New York 10016, USA.
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214
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Bruno B, Giaccone L, Rotta M, Anderson K, Boccadoro M. Novel targeted drugs for the treatment of multiple myeloma: from bench to bedside. Leukemia 2005; 19:1729-38. [PMID: 16094421 DOI: 10.1038/sj.leu.2403905] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Multiple myeloma remains an incurable plasma cell neoplasm. New insights into its pathogenesis have identified signaling pathways that have become potential therapeutic targets. It has clearly been established that intracellular regulatory proteins and interactions between malignant plasma cells and the bone marrow microenvironment play an important role in their survival and drug resistance. Several new agents associated with molecular targets are currently being investigated to design new treatment strategies aimed at prolonging survival and improving quality of life. This review illustrates their mechanisms of action and the possible future clinical applications.
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Affiliation(s)
- B Bruno
- Divisione di Ematologia dell'Università di Torino, Ospedale San Giovanni Battista, Torino, Italy.
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215
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Chang H, Stewart AK, Qi XY, Li ZH, Yi QL, Trudel S. Immunohistochemistry accurately predicts FGFR3 aberrant expression and t(4;14) in multiple myeloma. Blood 2005; 106:353-5. [PMID: 15761022 DOI: 10.1182/blood-2005-01-0033] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The t(4;14) translocation detected by fluorescence in situ hybridization (FISH) is an independent prognostic factor for an adverse outcome of multiple myeloma (MM). Because t(4;14) uniquely results in fibroblast growth factor receptor 3 (FGFR3) expression, decalcified, paraffin-embedded bone marrow biopsies were immunostained for FGFR3, and its expression was correlated with the t(4;14) status. FISH detected t(4;14) in 16 (19%) of 85 MM patient specimens, and immunocytochemistry detected aberrant FGFR3 expression in 13 (15%). Twelve (75%) t(4;14)-positive cases expressed FGFR3, and 12 (92%) FGFR3-positive cases harbored a t(4;14). FGFR3 expression and t(4;14) were strongly correlated (P < .001). FGFR3 expression by immunohistochemistry was associated with the immunoglobulin A (IgA) isotype (P < .001), a shorter progression-free survival (median, 11.5 versus 25.8 months; P < .001), and a shorter overall survival (median, 19.2 versus 46.3 months; P < .001).
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MESH Headings
- Adult
- Aged
- Chromosomes, Human, Pair 14
- Chromosomes, Human, Pair 4
- Female
- Gene Expression Regulation, Neoplastic
- Genetic Testing
- Humans
- Immunohistochemistry
- In Situ Hybridization, Fluorescence
- Male
- Middle Aged
- Multiple Myeloma/diagnosis
- Multiple Myeloma/genetics
- Predictive Value of Tests
- Protein-Tyrosine Kinases/genetics
- Receptor, Fibroblast Growth Factor, Type 3
- Receptors, Fibroblast Growth Factor/genetics
- Translocation, Genetic
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Affiliation(s)
- Hong Chang
- Department of Laboratory Hematology, Princess Margaret Hospital/University Health Network, McLaughlin Center for Molecular Medicine, University of Toronto, ON, Canada.
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216
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Keats JJ, Maxwell CA, Taylor BJ, Hendzel MJ, Chesi M, Bergsagel PL, Larratt LM, Mant MJ, Reiman T, Belch AR, Pilarski LM. Overexpression of transcripts originating from the MMSET locus characterizes all t(4;14)(p16;q32)-positive multiple myeloma patients. Blood 2005; 105:4060-9. [PMID: 15677557 PMCID: PMC1895072 DOI: 10.1182/blood-2004-09-3704] [Citation(s) in RCA: 136] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Multiple myeloma (MM) is a B-lineage malignancy characterized by diverse genetic subtypes and clinical outcomes. The recurrent immunoglobulin heavy chain (IgH) switch translocation, t(4;14)(p16;q32), is associated with poor outcome, though the mechanism is unclear. Quantitative reverse-transcription-polymerase chain reaction (RT-PCR) for proposed target genes on a panel of myeloma cell lines and purified plasma cells showed that only transcripts originating from the WHSC1/MMSET/NSD2 gene are uniformly dysregulated in all t(4;14)POS patients. The different transcripts detected, multiple myeloma SET domain containing protein (MMSET I), MMSET II, Exon 4a/MMSET III, and response element II binding protein (RE-IIBP), are produced by alternative splicing and alternative transcription initiation events. Translation of the various transcripts, including those from major breakpoint region 4-2 (MB4-2) and MB4-3 breakpoint variants, was confirmed by transient transfection and immunoblotting. Green fluorescent protein (GFP)-tagged MMSET I and II, corresponding to proteins expressed in MB4-1 patients, localized to the nucleus but not nucleoli, whereas the MB4-2 and MB4-3 proteins concentrate in nucleoli. Cloning and localization of the Exon 4a/MMSET III splice variant, which contains the protein segment lost in the MB4-2 variant, identified a novel protein domain that prevents nucleolar localization. Kinetic studies using photobleaching suggest that the breakpoint variants are functionally distinct from wild-type proteins. In contrast, RE-IIBP is universally dysregulated and also potentially functional in all t(4;14)POS patients irrespective of fibroblast growth factor receptor 3 (FGFR3) expression or breakpoint type.
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Affiliation(s)
- Jonathan J Keats
- Department of Oncology, University of Alberta & Cross Cancer Institute, 11560 University Ave, Edmonton, AB, T6G 1Z2, Canada
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