A rare genetic disease, Fanconi anemia (FA), now attracts broader attention from cancer biologists and basic researchers in the DNA repair and ubiquitin biology fields as well as from hematologists. FA is a chromosome instability syndrome characterized by childhood-onset aplastic anemia, cancer or leukemia susceptibility, and cellular hypersensitivity to DNA crosslinking agents. Identification of 11 genes for FA has led to progress in the molecular understanding of this disease. FA proteins, including a ubiquitin ligase (FANCL), a monoubiquitinated protein (FANCD2), a helicase (FANCJ/BACH1/BRIP1), and a breast/ovarian cancer susceptibility protein (FANCD1/BRCA2), appear to cooperate in a pathway leading to the recognition and repair of damaged DNA. Molecular interactions among FA proteins and responsible proteins for other chromosome instability syndromes (BLM, NBS1, MRE11, ATM, and ATR) have also been found. Furthermore, inactivation of FA genes has been observed in a wide variety of human cancers in the general population. These findings have broad implications for predicting the sensitivity and resistance of tumors to widely used anticancer DNA crosslinking agents (cisplatin, mitomycin C, and melphalan). Here, we summarize recent progress in the molecular biology of FA and discuss roles of the FA proteins in DNA repair and cancer biology.

The transforming growth factor-beta (TGF-beta) signaling pathway is an essential regulator of cellular processes, including proliferation, differentiation, migration, and cell survival. During hematopoiesis, the TGF-beta signaling pathway is a potent negative regulator of proliferation while stimulating differentiation and apoptosis when appropriate. In hematologic malignancies, including leukemias, myeloproliferative disorders, lymphomas, and multiple myeloma, resistance to these homeostatic effects of TGF-beta develops. Mechanisms for this resistance include mutation or deletion of members of the TGF-beta signaling pathway and disruption of the pathway by oncoproteins. These alterations define a tumor suppressor role for the TGF-beta pathway in human hematologic malignancies. On the other hand, elevated levels of TGF-beta can promote myelofibrosis and the pathogenesis of some hematologic malignancies through their effects on the stroma and immune system. Advances in the TGF-beta signaling field should enable targeting of the TGF-beta signaling pathway for the treatment of hematologic malignancies.

Recent insights into the molecular mechanisms of polycythemia vera (PV) and essential thrombocythemia (ET) are challenging the traditional diagnostic classification of these myeloproliferative disorders (MPDs). Clonality analysis using X-chromosome inactivation patterns has revealed apparent heterogeneity among the MPDs. The recently discovered single somatic activating point mutation in the JAK2 gene (JAK2-V617F) is found in the great majority of patients with PV, but also in many patients with phenotypically classified ET and other MPDs. In contrast to the acquired MPDs, mutations of the erythropoietin receptor and thrombopoietin receptor have been identified in familial forms of nonclonal erythrocytosis and thrombocytosis, respectively. The mechanisms of major clinical complications of PV and ET remain poorly understood. Quantitative or qualitative abnormalities of red cells and platelets do not provide clear explanations for the thrombotic and bleeding tendency in these MPDs, suggesting the need for entirely new lines of research in this area. Recently reported randomized clinical trials have demonstrated the efficacy and safety of low-dose aspirin in PV, and an excess rate of arterial thrombosis, major bleeding, and myelofibrotic transformation, but decreased venous thrombosis, in patients with ET treated with anagrelide plus aspirin compared to hydroxyurea plus aspirin.

Recent studies suggest that thrombophilic abnormalities and the use of oral contraceptives (OCs) are the leading causes of cerebral vein thrombosis (CVT). The purpose of this study was to assess the association between CVT and thrombophilic states, OCs, and their interaction. For data sources, we used the MEDLINE, EMBASE, and Cochrane Library databases (January 1994 to March 2005), reference lists of retrieved articles, and contact with content experts. We selected studies comparing the prevalence of OC use and the prevalence of prothrombitic abnormalities in patients with CVT compared with healthy controls. Two reviewers independently selected studies and extracted study characteristics, quality, and outcomes. Odds ratios (ORs) were calculated for each trial and pooled using the Mantel-Haenszel method. Seventeen studies were included. There was an increased risk of CVT in patients using OCs (OR 5.59; 95% confidence interval [CI] 3.95 to 7.91; P < .001), and in patients with factor V Leiden (OR 3.38; 95% CI 2.27 to 5.05; P < .001), with mutation G20 210A of prothrombin (OR 9.27; 95% CI 5.85 to 14.67; P < .001) and with hyperhomocysteinemia (OR 4.07; 95% CI 2.54 to 6.52; P < .001). We concluded that OC users, and patients with factor V Leiden, the prothrombin G20 120A mutation, and hyperhomocysteinemia are at a significantly increased risk of CVT.

Non-Hodgkin lymphomas develop from nodal and extranodal lymphoid tissues. A distinct subset of extranodal lymphomas arising from B cells of the marginal zone (MZ) of mucosa-associated lymphoid tissue (MALT) or spleen has been individualized. Growing evidence indicates that MZ lymphomas are associated with chronic antigenic stimulation by microbial pathogens and/or autoantigens. The list of microbial species associated with MZ lymphoproliferations has grown longer with molecular investigations and now comprises at least 5 distinct members: H. pylori, C. jejuni, B. burgdorferi, C. psittaci, and hepatitis C virus (HCV), which have been associated with gastric lymphoma, immunoproliferative small intestinal disease, cutaneous lymphoma, ocular lymphoma, and spleen lymphoma, respectively. A pathophysiologic scenario involving chronic and sustained stimulation of the immune system leading to lymphoid transformation has emerged. It defines a distinct category of infection-associated lymphoid malignancies, in which the infectious agent does not directly infect and transform lymphoid cells, as do the lymphotropic oncogenic viruses Epstein-Barr virus (EBV), human herpesvirus 8 (HHV8), and human T-lymphotropic virus 1 (HTLV-1), but rather indirectly increases the probability of lymphoid transformation by chronically stimulating the immune system to maintain a protracted proliferative state.

The separation of graft-versus-host disease (GVHD) and graft-versus-leukemia (GVL) remains the "holy grail" of allogeneic stem cell transplantation, and improvements are urgently needed to allow more effective therapy of malignant disease. The use of G-CSF-mobilized peripheral blood as a clinical stem cell source is associated with enhanced GVL effects without amplification of significant acute GVHD. Preclinical studies have demonstrated that G-CSF modulates donor T cell function before transplantation, promoting T(H)2 differentiation and regulatory T cell function. In addition, the expansion of immature antigen-presenting cells (APCs) and plasmacytoid dendritic cells (DCs) favors the maintenance of this pattern of T cell differentiation after transplantation. Although these patterns of T cell differentiation attenuate acute GVHD, they do not have an impact on the cytolytic pathways of the CD8(+) T cells that are critical for effective GVL. Recently, it has been demonstrated that modification of G-CSF, either by pegylation of the native cytokine or conjugation to Flt-3L, results in the expansion and activation of donor iNKT cells, which significantly augment CD8(+) T cell-mediated cytotoxicity and GVL effects after transplantation. Given that these cytokines also enhance the expansion of regulatory T cells and APCs, they further separate GVHD and GVL, offering potential clinical advantages for the transplant recipient.

Tumor angiogenesis is crucial for the progression and metastasis of cancer. The vasculature of tumor tissue is different from normal vasculature. Therefore, tumor vascular targeting therapy could represent an effective therapeutic strategy with which to suppress both primary tumor growth and tumor metastasis. The use of viral vectors for tumor vascular targeting therapy is a promising strategy based on the unique properties of viral vectors. In order to circumvent the potential problems of antiviral neutralizing antibodies, poor access to extravascular tumor tissue, and toxicities to normal tissue, viral vectors need to be modified to target the tumor endothelial cells. Viral vectors that could be used for tumor vascular targeting therapy include adenoviral vectors, adeno-associated viral vectors, retroviral vectors, lentiviral vectors, measles virus, and herpes simplex viral vectors. In this review, we will summarize the strategies available for targeting viral vectors for tumor vascular targeting therapy.

Our considerable wealth of data concerning hematologic processes has come despite difficulties working with stem and progenitor cells in vitro and their propensity to differentiate. Key methodologies that have sought to overcome such limitations include transgenic/knock-out animals and in vitro studies using murine embryonic stem cells, because both permit investigation of the formation of hematopoietic tissue from nonhematopoietic precursors. Although there have been many successful studies in model animals for understanding hematopoietic-cell development, differences between lower vertebrates and humans have left gaps in our understanding. Clearly, human-specific strategies to study the onset of hematopoiesis, particularly the earliest events leading to the specification of both normal and abnormal hematopoietic tissue, could bring an investigational renaissance. The recent availability of human embryonic stem (hES) cells suggests that such a system is now at hand. This review highlights the potential of hES cells to model human hematologic processes in vitro with an emphasis on disease targets.

Members of the Notch family of transmembrane receptors play an important role in cell fate determination. Over the past decade, a role for Notch in the pathogenesis of hematologic and solid malignancies has become apparent. Numerous cellular functions and microenvironmental cues associated with tumorigenesis are modulated by Notch signaling, including proliferation, apoptosis, adhesion, epithelial-to-mesenchymal transition, and angiogenesis. It is becoming increasingly evident that Notch signaling can be both oncogenic and tumor suppressive. This review highlights recent findings regarding the molecular and functional aspects of Notch-mediated neoplastic transformation. In addition, cellular mechanisms that potentially explain the complex role of Notch in tumorigenesis are discussed.

The use of myelosuppressive agents to reduce the risk of thrombosis in patients with polycythemia vera (PV) and essential thrombocythemia (ET) has been associated with an increased risk of transformation to acute myeloid leukemia (AML). Whereas chlorambucil, busulfan, and radiophosphorus (32P) have been demonstrated to increase the risk of transformation, the leukemogenic potential of hydroxyurea (HU) continues to be a matter of debate. Clinical studies have suggested that HU may cause a small increase in the risk of AML, but it has proven difficult to establish whether AML is actually caused by HU or arises during the natural progression of PV and ET. Reports that HU undergoes metabolic activation to species that induce mutation appear to support the notion that it is leukemogenic. Here, we suggest that the ability of HU to induce mutation in cell culture studies results from the generation of nitrogen dioxide via the autoxidation of nitric oxide, a product of HU metabolism. However, we argue that autoxidation would not occur in vivo, leading to the conclusion that generation of the mutagen nitrogen dioxide is peculiar to cell culture systems and has little relevance to the use of HU in the management of PV and ET.

Stem cell gene therapy has long been limited by low gene transfer efficiency to hematopoietic stem cells. Recent years have witnessed clinical success in select diseases such as X-linked severe combined immunodeficiency (SCID) and ADA deficiency. Arguably, the single most important factor responsible for the increased efficacy of these recent protocols is the fact that the genetic correction provided a selective in vivo survival advantage. Since, for most diseases, there will be no selective advantage of gene-corrected cells, there has been a significant effort to arm vectors with a survival advantage. Two-gene vectors can be used to introduce the therapeutic gene and a selectable marker gene. Efficient in vivo selection strategies have been demonstrated in clinically relevant large-animal models. Mutant forms of the DNA repair-enzyme methylguanine methyltransferase in particular have allowed for efficient in vivo selection and have achieved sustained marking with virtually 100% gene-modified cells in large animals, and with clinically acceptable toxicity. Translation of these strategies to the clinical setting is imminent. Here, we review how in vivo selection strategies can be used to make stem cell gene therapy applicable to the treatment of a wider scope of genetic diseases and patients.

Signals from the microenvironment have a profound influence on the maintenance and/or progression of hematopoietic and epithelial cancers. Mesenchymal or marrow-derived stromal cells, which constitute a large proportion of the non-neoplastic cells within the tumor microenvironment, constitutively secrete the chemokine stromal cell-derived factor-1 (SDF-1/CXCL12). CXCL12 secretion by stromal cells attracts cancer cells, acting through its cognate receptor, CXCR4, which is expressed by both hematopoietic and nonhematopoietic tumor cells. CXCR4 promotes tumor progression by direct and indirect mechanisms. First, CXCR4 is essential for metastatic spread to organs where CXCL12 is expressed, and thereby allows tumor cells to access cellular niches, such as the marrow, that favor tumor-cell survival and growth. Second, stromal-derived CXCL12 itself can stimulate survival and growth of neoplastic cells in a paracrine fashion. Third, CXCL12 can promote tumor angiogenesis by attracting endothelial cells to the tumor microenvironment. CXCR4 expression is a prognostic marker in various types of cancer, such as acute myelogenous leukemia or breast carcinoma. Promising results in preclinical tumor models indicate that CXCR4 antagonists may have antitumor activity in patients with various malignancies. Collectively, these observations reveal that CXCR4 is an important molecule involved in the spread and progression of a variety of different tumors. As such, CXCR4 antagonists, although initially developed for treatment of AIDS, actually may become effective agents for the treatment of neoplastic disease.

Embryonic stem (ES) cells exhibit the remarkable capacity to become virtually any differentiated tissue upon appropriate manipulation in culture, a property that has been beneficial for studies of hematopoiesis. Until recently, the majority of this work used murine ES cells for basic research to elucidate fundamental properties of blood-cell development and establish methods to derive specific mature lineages. Now, the advent of human ES cells sets the stage for more applied pursuits to generate transplantable cells for treating blood disorders. Current efforts are directed toward adapting in vitro hematopoietic differentiation methods developed for murine ES cells to human lines, identifying the key interspecies differences in biologic properties of ES cells, and generating ES cell-derived hematopoietic stem cells that are competent to repopulate adult hosts. The ultimate medical goal is to create patient-specific and generic ES cell lines that can be expanded in vitro, genetically altered, and differentiated into cell types that can be used to treat hematopoietic diseases.

Epstein-Barr virus (EBV) is a tumorigenic herpes virus that infects and persists in B lymphocytes in the majority of humans, generally without causing disease. However, in a few individuals the virus is associated with significant pathology, particularly benign and malignant lymphoproliferations. Recently acquired knowledge on the mechanisms of EBV persistence, immune control of primary and persistent infection, and disease pathogenesis is now being translated into the clinic with novel methods of diagnosis, prevention and treatment contributing to improved patient care. This review concentrates on these recent advances in the field of hematology/oncology.

Recently, considerable progress has been made in the identification of molecular and cellular markers that may predict the tendency for disease progression in patients with chronic lymphocytic leukemia (CLL) or detect minimal residual disease after therapy. These developments have created uncertainty for clinicians who hope to incorporate the use of these markers and new disease-assessment tools into standard clinical practice. However, clinical trials are required to determine whether poor-prognosis leukemia-cell markers, such as expression of unmutated immunoglobulin genes or the zeta-associated protein of 70 kDa (ZAP-70), can be used as the basis for determining the time or type of therapy. Pending the outcome of such trials, treatment decisions outside the context of a clinical trial still should be based on guidelines established by the most recent National Cancer Institute-sponsored Working Group.

T-cell non-Hodgkin lymphomas (NHLs) are uncommon malignancies. The current WHO/EORTC classification recognizes 9 distinct clinicopathologic peripheral T-cell NHLs. These disorders have unique characteristics and require individualized diagnostic and therapeutic strategies. Tremendous progress has been made in recent years in the understanding of the pathogenesis of these disorders. Specific chromosomal translocations and viral infections are now known to be associated with certain lymphomas. In this review, we describe their clinical and pathologic features. We also discuss the use of molecular studies in the diagnostic work-up of T-cell lymphomas. Because of the rarity of these disorders and the lack of well-designed clinical trials, the treatment of peripheral T-cell NHLs is often challenging. Additional studies are required to learn more about the biology of these diseases, which may lead to more optimal and possibly targeted therapies.

Therapy for patients with chronic lymphocytic leukemia (CLL) has greatly changed over the past few years. After years of stagnation, with treatment revolving around the use of rather ineffective drugs such as alkylators, many patients are now being treated with more effective agents such as purine analogs either alone or combined with other drugs and/or monoclonal antibodies. Treatment of patients refractory to these treatments is particularly challenging and should be decided only upon a careful evaluation of the disease, patient characteristics, and prognostic factors. Refractory disease should be clearly separated from relapsing disease. The only curative therapy for patients with CLL, including those with refractory disease, is allogeneic stem cell transplantation. However, the use of allogeneic transplantation is limited because of the advanced age of most patients and the high transplant-related mortality (TRM). Transplants with nonmyeloablative regimens may reduce TRM and allow more patients to receive transplants more safely. For patients in whom an allogeneic transplantation is not feasible or in whom it is deemed inappropriate, participation in phase 2 trials should be encouraged. Finally, to investigate mechanisms to overcome resistance to therapy in CLL and to identify patients that might gain benefit from early, intensive therapies (eg, based on biologic markers) constitute a challenge that needs active investigation.

The diagnosis of anemia is an important aspect of the practice of hematology. The first step is to decide whether the patient is, in fact, anemic. Unless earlier blood counts are available, and they often are not, the physician must make his or her decision on the basis of the population distribution of hemoglobin values. How likely is it that the patient's hemoglobin value lies below the normal distribution; that is, "the lower limit"?

Although most patients with cancer respond to therapy, few are cured. Moreover, objective clinical responses to treatment often do not even translate into substantial improvements in overall survival. For example, patients with indolent lymphoma who achieved a complete remission with conventional-dose therapies in the prerituximab era did not experience a survival advantage over similar patients treated with a "watch and wait" approach. Several studies have also shown that neither the magnitude nor the kinetics of clinical response has an impact on survival in multiple myeloma. Recent data suggesting many malignancies arise from a rare population of cells that exclusively maintains the ability to self-renew and sustains the tumor (ie, "cancer stem cells") may help explain this paradox that response and survival are not always linked. Therapies that successfully eliminate the differentiated cancer cells characterizing the tumor may be ineffective against rare, biologically distinct cancer stem cells. New methods for assessing treatment efficacy must also be developed, as traditional response criteria measure tumor bulk and may not reflect changes in rare cancer stem cell populations. In this article, we discuss the evidence for cancer stem cells in hematologic malignancies and possible ways to begin targeting these cells and measuring clinical effectiveness of such treatment approaches.

The human globin genes are among the most extensively characterized in the human genome, yet the details of the molecular events regulating normal human hemoglobin switching and the potential reactivation of fetal hemoglobin in adult hematopoietic cells remain elusive. Recent discoveries demonstrate physical interactions between the beta locus control region and the downstream structural gamma- and beta-globin genes, and with transcription factors and chromatin remodeling complexes. These interactions all play roles in globin gene expression and globin switching at the human beta-globin locus. If the molecular events in hemoglobin switching were better understood and fetal hemoglobin could be more fully reactivated in adult cells, the insights obtained might lead to new approaches to the therapy of sickle cell disease and beta thalassemia by identifying specific new targets for molecular therapies.