Evidence of an immunologic mechanism behind the therapeutical effects of arsenic trioxide (As(2)O(3)) on myeloma cells

Old dog, new trick: Trivalent arsenic as an immunomodulatory drug

Trivalent arsenic (As(III)) is recently found to be an immunomodulatory agent. As(III) has therapeutic potential in several autoimmune and inflammatory diseases in vivo. In vitro, it selectively induces apoptosis of immune cells due to different sensitivity. At a non-toxic level, As(III) shows its multifaceted nature by inducing either pro- or anti-inflammatory functions of immune subsets. These effects are exerted by either As(III)-protein interactions or as a consequence of As(III)-induced homeostasis imbalance. The immunomodulatory properties also show synergistic effects of As(III) with cancer immunotherapy. In this review, we summarize the immunomodulatory effects of As(III), focusing on the effects of As(III) on immune subsets in vitro, on mouse models of immune-related diseases, and the role of As(III) in cancer immunotherapy. Updates of the mechanisms of action, the pioneer clinical trials, dosing, and adverse events of therapeutic As(III) are also provided.

Trials of Arsenic Trioxide in Multiple Myeloma

BACKGROUND

Several reports on the use of arsenic trioxide (ATO), mainly in acute promyelocytic leukemia, have led to a renewed interest in ATO in the management of malignancies, especially those of hematologic origin such as multiple myeloma (MM). MM remains an incurable disease, with median survival rates of 4-6 years. Thus, newer treatments with good safety profiles are needed to improve the quality of responses, prolong progression, and increase overall survival.

METHOD

The current state of the art regarding the role of ATO in the management of MM and the rationale for this consideration is reviewed.

RESULTS

Preclinical evidence suggests that one of the mechanisms in which ATO exerts its antimyeloma effect is by immunologic mechanisms. One such mechanism appears to be achieved by a marked increase in lymphokine-activated killer (LAK)-mediated killing and up-modulation of CD38 and CD54, two molecules involved in cell-cell interactions. Two phase II trials have shown that the drug appears to be clinically effective.

CONCLUSIONS

With the improved understanding of the interaction between the myeloma cell and its microenvironment as well as the cytokine support system, it does not appear than any particular agent will be able to control the disease permanently. In the clinical arena, the next generation of studies will be designed to combine different molecules to take advantage of non-overlapping toxicities and to compromise the extensive and redundant myeloma support system, thus controlling the disease in a chronic phase.

Impact of exposure to tobacco smoke, arsenic, and phthalates on locally advanced cervical cancer treatment-preliminary results

BACKGROUND

Cancer research is a national and international priority, with the efficiency and effectiveness of current anti-tumor therapies being one of the major challenges with which physicians are faced.

OBJECTIVE

To assess the impact of exposure to tobacco smoke, arsenic, and phthalates on cervical cancer treatment.

METHODS

We investigated 37 patients with locally advanced cervical carcinoma who underwent chemotherapy and radiotherapy. We determined cotinine and five phthalate metabolites in urine samples collected prior to cancer treatment, by gas chromatography coupled to mass spectrometry, and urinary total arsenic by atomic absorption spectrometry with hydride generation. We used linear regression to evaluate the effects of cotinine, arsenic, and phthalates on the change in tumor size after treatment, adjusted for confounding variables.

RESULTS

We detected no significant associations between urinary cotinine, arsenic, or phthalate monoesters on change in tumor size after treatment, adjusted for urine creatinine, age, baseline tumor size, and cotinine (for arsenic and phthalates). However, higher %mono-ethylhexyl phthalate (%MEHP), a putative indicator of phthalate diester metabolism, was associated with a larger change in tumor size (β = 0.015, 95% CI [0.003-0.03], P = 0.019).

CONCLUSION

We found no statistically significant association between the urinary levels of arsenic, cotinine, and phthalates metabolites and the response to cervical cancer treatment as measured by the change in tumor size. Still, our results suggested that phthalates metabolism may be associated with response to treatment for locally advanced cervical cancer. However, these observations are preliminary and will require confirmation in a larger, more definitive investigation.

Overview of drug therapy for multiple myeloma

Background. Multiple myeloma accounts for 10% of all haematologic malignancies worldwide. In Europe, over 10 000 new cases and nearly 8000 deaths were attributed to multiple myeloma in 2000. Unlike other malignancies, in which surgery and radiation are important treatment modalities, myeloma is exclusively treated with stem cell transplantation and drug therapy, requiring pharmacists to stay abreast of new developments. The melphalan-prednisolone and vincristine-doxorubicin-dexamethasone (VAD) regimens, which have been standard treatments for multiple myeloma over the past few decades, have yielded responses without real survival benefits. Transplantation utilizing high-dose chemotherapy has produced the only meaningful survival benefits for patients with multiple myeloma, but many patients are not candidates for this aggressive treatment option. More effective therapies for multiple myeloma are needed.

Objective. To address the mechanisms of action, safety, and efficacy of novel approaches to the treatment of myeloma involving bortezomib, thalidomide and its analogues, lenalidomide and CC-4047 (ActimidTM), and arsenic trioxide as single agents or in combination regimens.

Data sources. Published preclinical and primary clinical trial results, as well as scientific or clinical meeting abstracts. The author determined the relevance and subsequent inclusion of the data.

Conclusions. Bortezomib is approved in the US and Europe as single-agent therapy for the treatment of relapsed or refractory multiple myeloma. Thalidomide, its analogues, and arsenic trioxide have demonstrated activity and are under investigation in this disease. Further clinical trials of the efficacy and toxicity of these novel agents are ongoing and will further define optimal combinations and sequencing with conventional therapies.

Resolving the daratumumab interference with blood compatibility testing

BACKGROUND

Daratumumab (DARA), a promising novel therapy for multiple myeloma, is an IgG1κ monoclonal antibody that recognizes CD38 on myeloma cells. During routine compatibility testing, we observed that the plasma of five of five DARA-treated patients demonstrated a positive antibody screen and panreactivity on red blood cell (RBC) panel testing. We hypothesized that the observed panreactivity reflected DARA binding to CD38 on reagent RBCs, and we investigated methods to prevent this binding.

STUDY DESIGN AND METHODS

DARA binding to CD38+ or CD38- HL60 cells was assessed by flow cytometry. To remove cell surface CD38, cells were incubated with dithiothreitol (DTT) or trypsin. Soluble CD38 or anti-DARA was used to neutralize DARA in solution. Routine blood bank serologic methods were used to test samples from DARA-treated patients and normal plasma samples spiked with DARA and/or alloantibodies.

RESULTS

Normal plasma samples spiked with DARA (0.1-10 µg/mL) and incubated with reagent RBCs recapitulated the interference observed with samples from DARA-treated patients. Flow cytometry experiments confirmed DARA binding to CD38+ HL60 cells, but not to CD38- controls. DTT treatment of CD38+ HL60 cells reduced DARA binding by 92% by denaturing cell surface CD38. Treating DARA-containing plasma with soluble CD38 or anti-DARA idiotype also inhibited DARA binding.

CONCLUSION

DARA causes panreactivity in vitro by binding to CD38 on reagent RBCs. Treating reagent RBCs with DTT is a robust method to negate the DARA interference, enabling the safe provision of blood to DARA-treated patients. Because DTT denatures Kell antigens, K- units are provided to these patients.

Heavy metal toxicity and the environment

Heavy metals are naturally occurring elements that have a high atomic weight and a density at least five times greater than that of water. Their multiple industrial, domestic, agricultural, medical, and technological applications have led to their wide distribution in the environment, raising concerns over their potential effects on human health and the environment. Their toxicity depends on several factors including the dose, route of exposure, and chemical species, as well as the age, gender, genetics, and nutritional status of exposed individuals. Because of their high degree of toxicity, arsenic, cadmium, chromium, lead, and mercury rank among the priority metals that are of public health significance. These metallic elements are considered systemic toxicants that are known to induce multiple organ damage, even at lower levels of exposure. They are also classified as human carcinogens (known or probable) according to the US Environmental Protection Agency and the International Agency for Research on Cancer. This review provides an analysis of their environmental occurrence, production and use, potential for human exposure, and molecular mechanisms of toxicity, genotoxicity, and carcinogenicity.

Multiple myeloma: an update of developments in targeted therapy

Multiple myeloma continues to be an incurable illness. Improvement in our understanding of the disease is leading to new therapeutic modalities and the definition of new targeted therapy. Several pathways have been identified as areas for targeted therapy, and this review will discuss key molecules in some detail. New agents and molecules with biologic modulator activity appear to be changing the natural history of the disease. Agents such as thalidomide or its analogs, arsenic trioxide or bortezomib, hold great promise; however, much is yet to be learned on how to integrate these agents into disease management.

Use of anti-cancer drugs, mitocans, to enhance the immune responses against tumors

Cytotoxic drugs in cancer therapy are used with the expectation of selectively killing and thereby eliminating the offending cancer cells. If they should die in an appropriate manner, the cells can also release danger signals that promote an immune reaction that reinforces the response against the cancer. The identity of these immune-enhancing danger signals, how they work extra- and intracellularly, and the molecular mechanisms by which some anti-cancer drugs induce cell death to bring about the release of danger signals are the major focus of this review. A specific group of mitocans, the vitamin E analogs that act by targeting mitochondria to drive ROS production and also promote a more immunogenic means of cancer cell death exemplify such anti-cancer drugs. The role of reactive oxygen species (ROS) production and the events leading to the activation of the inflammasome and pro-inflammatory mediators induced by dying cancer cell mitochondria are discussed along with the evidence for their contribution to promoting immune responses against cancer. Current knowledge of how the danger signals interact with immune cells to boost the anti-tumor response is also evaluated.

Heavy metal toxicity and the environment

Heavy metals are naturally occurring elements that have a high atomic weight and a density at least five times greater than that of water. Their multiple industrial, domestic, agricultural, medical, and technological applications have led to their wide distribution in the environment, raising concerns over their potential effects on human health and the environment. Their toxicity depends on several factors including the dose, route of exposure, and chemical species, as well as the age, gender, genetics, and nutritional status of exposed individuals. Because of their high degree of toxicity, arsenic, cadmium, chromium, lead, and mercury rank among the priority metals that are of public health significance. These metallic elements are considered systemic toxicants that are known to induce multiple organ damage, even at lower levels of exposure. They are also classified as human carcinogens (known or probable) according to the US Environmental Protection Agency and the International Agency for Research on Cancer. This review provides an analysis of their environmental occurrence, production and use, potential for human exposure, and molecular mechanisms of toxicity, genotoxicity, and carcinogenicity.

Arsenic trioxide enhances the cytotoxic effect of thalidomide in a KG-1a human acute mylogenous leukemia cell line

Studies have shown that thalidomide exerts modest activity as a single agent in the therapy of acute myeloid leukemia (AML). The present investigation was conducted to test the hypothesis that the cytotoxic effect of thalidomide is enhanced when properly combined with other chemotherapeutic agents. The human AML cell line KG-1a was used in this study. Cells were cultured for 48 h in the presence or absence of thalidomide, arsenic trioxide and a combination of the two substances. Results obtained indicate that thalidomide at concentrations of 1, 2 and 5 mg/l produced a dose-dependent cytotoxic effect and at 5 mg/ml resulted in late apoptosis in 49.39% of the total cell population (as compared to 5.35% in the control cells). When the cells were incubated with arsenic trioxide alone (4 µM), late apoptosis was detected in 16.97% of the total cell population. However, when cells were incubated with a combination of thalidomide (5 mg/l) and arsenic trioxide (4 µM), late apoptosis was noted to be 80.6% in the total cell population. This percentage of late apoptosis was statistically significant from that observed when cells were incubated with thalidomide alone. These findings clearly indicate that arsenic trioxide enhances the cytotoxic effects of thalidomide.

Supplements for immune enhancement in hematologic malignancies

This brief review aims to discuss the various cellular immunological aspects and related mechanisms of the use of specific components from traditional herbal medicines. We begin with lessons learned from thalidomide as an effective single drug with multiple mechanisms of action to treat multiple myeloma. Examples of “supplements” or integrative therapy will be drawn from arsenic trioxide, medicinal mushrooms including Coriolus vesicular and Ganoderma lucidum, followed by the discussion of beta-glucans affecting various immunological important cellular subsets. Different classes of compounds may enhance distinct immune cell populations that might contribute to a multi-targeted holistic effects on anti-cancer treatment. Finally, we conclude by highlighting an herbal formulation PHY906 as a potential adjunct to chemotherapy that might become one of the first US Food and Drug Administration (FDA) approved oral herbal medicines for anti-cancer adjunct treatment.

Arsenical-based cancer drugs

Arsenic is a semi-metal or metalloid with two biologically important oxidation states, As(III) and As(V). As(III), in particular, reacts with closely spaced protein thiols, forming stable cyclic dithioarsinite complexes in which both sulfur atoms are bound to arsenic. It is this reaction that is mostly responsible for arsenics cytotoxicity. Arsenic compounds have been used as medicinal agents for many centuries for the treatment of diseases such as psoriasis, syphilis, and rheumatosis. From the 1700's until the introduction of and use of modern chemotherapy and radiation therapy in the mid 1900's, arsenic was a mainstay in the treatment of leukemia. Concerns about the toxicity of arsenical compounds led eventually to their abandonment for the treatment of cancer. The discovery in the 1980's that arsenic trioxide induces complete remission in a high percentage of patients with acute promyelocytic leukemia has awakened interest in this metalloid for the treatment of human disease. In particular, a new class or organoarsenicals are being trialed for the treatment of hematological malignancies and solid tumors. In this review, we discuss the arsenical-based compounds used in the past and present for the treatment of various forms of cancer. Mechanisms of action and selectivity and acute and chronic toxicities are discussed along with the prospects of this class of molecule.

Arsenic trioxide and neuroblastoma cytotoxicity

The majority of aggressive forms of the childhood tumor neuroblastoma can with current treatment protocols not be cured and possess a major challenge in pediatric oncology. After initial rounds of chemotherapy, surgery and irradiation, which in most cases result in tumor regression, these aggressive neuroblastomas relapse and frequently develop drug resistance. As approximately 50% of the children with neuroblastoma have an aggressive form, there is a compelling demand for new treatment strategies. Arsenic trioxide has the capacity to kill multidrug-resistant neuro-blastoma cells in vitro and in vivo and the drug is currently being evaluated in clinical trials. In this report we discuss the background to the use of arsenic trioxide in cancer therapy and the currently known mechanisms by which arsenic trioxide kills human neuroblastoma cells.

Efficacy and safety results with the combination therapy of arsenic trioxide, dexamethasone, and ascorbic acid in multiple myeloma patients: a phase 2 trial

BACKGROUND

Single-agent arsenic trioxide has shown promising results in patients with relapsed or refractory multiple myeloma (MM). Because preclinical data suggested greater activity with dexamethasone and ascorbic acid, a phase 2 trial of the combination of arsenic trioxide, dexamethasone, and ascorbic acid in patients with relapsed or refractory MM was conducted.

METHODS

Twenty patients in whom no more than two previous therapies had failed were enrolled. The mean age was 62 yr, and 55% of the patients had refractory disease. The regimen consisted of 14- or 15-wk cycles, with the first cycle considered induction, followed by one or two consolidation cycles with a reduced steroid schedule and then a maintenance cycle in responding patients.

RESULTS

The overall response rate was 30%, with at least stable disease in 80% of patients. Median progression- free survival was 316 d in all patients and 584 d in those with a response. The regimen was well tolerated, with most adverse events being mild or moderate.

CONCLUSIONS

This study showed the clinical efficacy and tolerability of the combination of arsenic trioxide, dexamethasone, and ascorbic acid. Further study is warranted.

The emerging role of arsenic trioxide as an immunomodulatory agent in the management of multiple myeloma

Multiple myeloma is a clonal disorder of plasma cells which is considered incurable with currently available therapies. Substantial advances have been achieved in the past decade with the identification of cellular mechanisms that confer drug resistance. This has resulted in newer agents such as arsenic trioxide (Trisenoxt), lenalidomide (Revlimid) and bortezomib (Velcade) with promising activity in this disease. In this review article we will outline the history, mechanisms of action, pharmacology, and clinical trials of arsenic trioxide in multiple myeloma.

Sustained activation of c-jun-N-terminal kinase plays a critical role in arsenic trioxide-induced cell apoptosis in multiple myeloma cell lines

Multiple myeloma (MM) is a presently incurable B-cell malignancy, and newer biologically based therapies are needed. Arsenic trioxide (ATO) has been established as a therapeutic agent for relapsed acute promyelocytic leukemia patients, and has been used for MM patients in clinical trials. In this study, we investigated the role of c-jun-N-terminal kinase (JNK) in ATO-induced apoptosis in MM lines. The exogenous interleukin (IL)-6 dependent MM line, ILKM-3, and independent MM lines, U266 and XG-7, were treated with a therapeutic concentration of ATO with or without JNK inhibitor 1 (a JNK-specific inhibitor) and anisomycin (a JNK activator). Their cell growth, cell cycle, JNK activation and NF-kappaB activation were investigated. ATO induced apoptosis in U266 and ILKM-3 regardless of their exogenous IL-6 dependency. This apoptosis, accompanied with decreased mitochondrial transmembrane potential, sustained activation of JNK but not cell cycle arrest. Pretreatment of JNK inhibitor prevented ATO-induced apoptosis in ATO-sensitive lines. Combined treatment with ATO and anisomycin induced sustained activation of JNK and apoptosis in the ATO-insensitive MM line, XG-7. Results of various time period treatments of ATO showed that sustained activation of JNK was needed in ATO-induced apoptosis in MM. IkBalpha phosphorylation was not associated with ATO-sensitivity of MM lines. These findings suggest that sustained activation of JNK plays a critical role in ATO-induced apoptosis in MM cell lines. Cotreatment with ATO and the agent, which can induce sustained activation of JNK, might improve the outcome in MM therapy.

Targeted therapy in multiple myeloma

BACKGROUND

Multiple myeloma (MM) is an incurable malignancy. Recent insights into its biology has allowed the use of novel therapies targeting not only the deregulated intracellular signaling in MM cells but also its interaction with the bone marrow microenvironment that confers drug resistance, growth, and survival advantage to the malignant cells.

METHODS

We review and summarize the recent advances in our knowledge of myeloma biology as well as the mechanism of action and clinical efficacy for novel therapeutic agents in clinical trials.

RESULTS

Several novel therapeutic agents are currently in clinical trials. Thalidomide is already established for both initial and salvage treatment. Bortezomib is being tested alone and in combination with conventional chemotherapy in various settings. Other agents are less effective in producing response but have been able to stabilize disease in patients with relapsed and/or refractory disease, such as arsenic trioxide, farnesyltransferase inhibitors, 2-methoxyestradiol, and vascular endothelial growth factor receptor inhibitors. Insights into drug resistance mechanism have also led to the development of novel agents that sensitize myeloma cells to chemotherapy (Bcl-2 antisense). Gene expression studies have in many instances identified pathways other than the intended target of the drug and have provided insights into the therapeutic mechanisms.

CONCLUSIONS

In the future, patients with MM will have more therapeutic options available than ever before. The challenge will be to identify patient subgroups that will benefit most from the different therapies and then determine how these biologically based therapies could be combined and incorporated into the overall management of patients.

Arsenic trioxide: an anti cancer missile with multiple warheads

The proven efficacy of ATO in the treatment of APL and the emerging importance of ATO in other diseases prompted extensive studies of the mechanisms of action of ATO in APL and in other types of cancers. In this review we will focus on downstream events in ATO-induced intrinsic and extrinsic apoptotic pathways with an emphasis on the role of pro-apoptotic and anti-apoptotic proteins and the role of p53 in ATO-induced apoptosis including its effect on cell cycle, its anti-mitotic effect and the role of apoptosis inducing factors (AIF) in ATO-induced apoptosis, chromatin condensation and nuclear fragmentation in myeloma cells as a model.

Clonal heterogeneity in growth kinetics of CD34+CD38- human cord blood cells in vitro is correlated with gene expression pattern and telomere length

Human hematopoietic stem cells (HSCs) are characterized by an extensive proliferative capacity that decreases from fetal liver to cord blood (CB) to adult bone marrow. In previous studies, it was demonstrated that the proliferative capacity of individual CD34+CD38- HSC clones is correlated with their growth kinetics in vitro and that HSC turnover in vivo can be estimated by telomere-length measurements. The present study was aimed at the characterization of the clonal composition of CD34+CD38- human umbilical CB cells in terms of growth kinetics, telomere length, and gene expression profile. For this purpose, individual CD34+CD38- CB cells were sorted into 96-well plates containing serum-free medium supplemented with six growth factors. During expansion, cell numbers in each individual well were scored in 3-day intervals. Once sufficient cell numbers were achieved, telomere length was measured by flow fluorescence in situ hybridization (flow FISH). In a second set of experiments, gene expression and colony-forming capacity were analyzed in slowly growing clones as compared with fast-growing clones, using linear amplification and oligonucleotide microarrays (HG-U133A; Affymetrix). Individual CD34+CD38- cells from CB displayed an extensive functional heterogeneity in growth kinetics. Among highly proliferative clones, the most slowly growing clones were characterized by the longest telomeres. Furthermore, significant differences in gene expression were detected between slow- and fast-growing clones, whereas no significant difference in colony-forming capacity was observed. These data provide further evidence for a functional hierarchy in the human HSC compartment and suggest a link between telomere length and proliferation capacity of individual HSC clones.

Arsenic trioxide therapy in acute promyelocytic leukemia and beyond: from bench to bedside

Arsenic trioxide (As2O3) has a long history of use in medicine. However, it was almost forgotten in Western medicine in the recent centuries. Prompted by reports from China about successful treatment of acute promyelocytic leukemia (APL) with As2O3, there was again increasing interest in this drug in the 1990s. This review summarizes the considerable knowledge about the mechanisms of action of As2O3 that was gained during the last 5-10 years. It is focused in particular on the effects of As2O3 in non-APL cells. Since As2O3 seems to induce apoptosis and inhibits growth in a large variety of cellular targets, it might become an alternative or adjunct drug to conventional chemotherapy. As2O3 can even be effective in cells resistant to conventional cytostatic agents. Insight into the cellular mechanisms, in particular the impact of the redox state on sensitivity towards As2O3 opens the possibility to enhance As2O3 effects by appropriate combination therapies.

Arsenic trioxide causes redistribution of cell cycle, caspase activation, and GADD expression in human colonic, breast, and pancreatic cancer cells

Arsenic trioxide is valuable for treatment of promyelocytic leukemia, but less attention has been paid to its therapeutic potential for other cancers. In this study, the effects of arsenic trioxide were tested in human pancreatic (AsPC-1), colonic (HT-29), and breast (MCF-7) cancer cells. In all three cancer cell lines, arsenic trioxide inhibited proliferation in a concentration and time-dependent manner, as measured by 3H-methyl thymidine incorporation and cell counting. Coincident with inhibition of growth, arsenic trioxide induced marked morphologic changes, including reduced cytoplasmic volume, membrane blebbing, and nuclear condensation consistent with apoptosis. Propidium iodide DNA staining at 24 hours revealed cell cycle arrest in the G0/G1 phase and an increase in the S phase, while at 72 hr there was G2/M phase arrest with a marked increase in the sub-G0/G1, apoptotic cell population. The DNA fragmentation induced by arsenic trioxide was confirmed by the terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling (TUNEL) assay in all cell lines. Western blot analysis revealed activation of caspase -3, -7, and -9 by arsenic trioxide. Caspase-3 activity was confirmed by demonstrating cleavage of its downstream target, poly ADP-ribose polymerase (PARP). Expression of the antiapoptosis protein, Bcl-2, was time-dependently decreased. In contrast, arsenic trioxide markedly enhanced the expression of the p21 protein, GADD45 and GADD153, in a time-dependent manner. These findings suggest that arsenic trioxide has potential as a therapeutic agent for these cancers.

The potential of arsenic trioxide in the treatment of malignant disease: past, present, and future

Arsenic trioxide (As2O3) is an effective therapy for acute promyelocytic leukemia (APL), and there has been promising activity noted in other hematologic and solid tumors. The mechanism of action of As2O3 such as differentiation and apoptosis has prompted study into combination therapy. Furthermore, the connection of the sensitivity of diseases such as APL and multiple myeloma to oxidative damage has allowed the investigation of pharmacologic modulation of the cellular redox state for potentiation of As2O3. Continued study of As2O3 as a single-agent and in combination therapy will allow identification of the safest and most effective treatment regimens for malignant disease.

Phase 2 study of arsenic trioxide in patients with relapsed or refractory multiple myeloma

Despite aggressive and innovative therapy, patients with multiple myeloma (MM) invariably relapse and die of their disease. New options for non-cytotoxic salvage therapy and additional therapeutic strategies are needed. Arsenic trioxide, an antitumour agent with a multifaceted mechanism of action, induces apoptosis in vitro in MM cell lines and freshly isolated cells from MM patients and, in preliminary studies, displayed clinical activity in patients with late-stage MM. A phase 2, multicentre, open-label study of arsenic trioxide was conducted in 24 MM patients; eight had relapsed and 16 were refractory to prior therapy. Patients received arsenic trioxide 0.25 mg/kg/d for 5 d/week during the first 2 weeks of each 4-week cycle. Sixteen patients had grade 3 or 4 neutropenia and one required antibiotics. Reductions (25% or more) in serum M-protein levels occurred in eight of 24 (33%) patients. An additional six (25%) patients had stable disease. The median time to response was 67.5 d, with a median duration of response of 130 d. Arsenic trioxide therapy lowered serum creatinine levels in two patients with high baseline values. These data indicate that arsenic trioxide is active and reasonably well tolerated as a single-agent salvage therapy, even in patients with late-stage, relapsed and refractory MM.

An update of novel therapeutic approaches for multiple myeloma

Multiple myeloma (MM) remains an incurable malignancy, despite conventional and high-dose therapies, and novel biologically based treatment approaches are urgently needed. Recent studies have characterized the molecular mechanisms by which MM cell/host bone marrow (BM) interactions regulate tumor cell growth, survival, and migration in the BM milieu. These studies have not only enhanced our understanding of disease pathogenesis, but they have also provided the framework for a new treatment paradigm targeting the MM cell in its BM microenvironment to overcome drug resistance and improve patient outcome. Clinical trials are confirming the remarkable activity and improved tolerability of some of the new agents identified through this paradigm, providing exciting evidence of translational success in MM.

Carcinogenic and systemic health effects associated with arsenic exposure--a critical review

Arsenic and arsenic containing compounds are human carcinogens. Exposure to arsenic occurs occupationally in several industries, including mining, pesticide, pharmaceutical, glass and microelectronics, as well as environmentally from both industrial and natural sources. Inhalation is the principal route of arsenic exposure in occupational settings, while ingestion of contaminated drinking water is the predominant source of significant environmental exposure globally. Drinking water contamination by arsenic remains a major public health problem. Acute and chronic arsenic exposure via drinking water has been reported in many countries of the world, where a large proportion of drinking water is contaminated with high concentrations of arsenic. General health effects that are associated with arsenic exposure include cardiovascular and peripheral vascular disease, developmental anomalies, neurologic and neurobehavioural disorders, diabetes, hearing loss, portal fibrosis, hematologic disorders (anemia, leukopenia and eosinophilia) and multiple cancers: significantly higher standardized mortality rates and cumulative mortality rates for cancers of the skin, lung, liver, urinary bladder, kidney, and colon in many areas of arsenic pollution. Although several epidemiological studies have documented the sources of exposure and the global impact of arsenic contamination, the mechanisms by which arsenic induces health effects, including cancer, are not well characterized. Further research is needed to provide a better understanding of the pathobiology of arsenic-induced diseases and to better define the toxicologic pathology of arsenic in various organ systems. In this review, we provide and discuss the underlying pathology and nature of arsenic-induced lesions. Such information is critical for understanding the magnitude of health effects associated with arsenic exposure throughout the world.

Breakthroughs in the management of multiple myeloma

Although multiple myeloma remains a terminal illness, the past four decades have seen a dramatic change in the outlook for a newly diagnosed patient in terms of therapies available, supportive care and insight into the pathogenesis of this disease. Among the newer agents available for treatment, thalidomide has been resurrected and discovered to be a valuable therapy for myeloma. Thalidomide appears to work, at least in part, through its anti-angiogenic properties, but much remains to be learned about its mechanism of action as well as optimal administration regimens. With the development of increasingly more potent bisphosphonates it has become possible to diminish the painful skeletal complications of myeloma, one of the most devastating problems of this disease. The most recent generation of bisphosphonates, pamidronic acid and zoledronic acid, have provided a statistically significant decrease in the skeletal complications of myeloma when used in a prophylactic manner. These agents appear to work by inhibiting osteoclast function. Progressive improvement in cytogenetic techniques has now demonstrated that almost all patients with myeloma have chromosomal abnormalities, some of which appear to confer varying degrees of prognostic significance. In particular, the changes in chromosome 13 are associated with an unusually poor outcome. These findings are serving as a guide toward learning more about the pathogenesis of myeloma as well as in identifying potential targets for therapy. Stem cell transplantation has emerged as the standard treatment for the large majority of patients with myeloma following the demonstration of superior complete remission and survival, both disease-free and overall, in a French randomised trial. Unfortunately, virtually all patients will eventually relapse following autologous stem cell transplantation, prompting continuing efforts such as tandem transplants, CD34+ selection, as well as modifications in the conditioning regimen to improve outcomes. Allogeneic bone marrow transplants appear to offer a better chance for a possible cure of myeloma but have been associated with an unusually high mortality. However, this approach is being revived with the advent of the less toxic non-myeloablative transplant that has provided an 81% short-term survival in a trial combining this approach with an initial conventional autologous bone marrow transplant. Immunotherapy with dendritic cells appears now to be a feasible way to enhance innate or acquired immunity to help eliminate minimal residual disease following autologous bone marrow transplant. Unfortunately, a cure for myeloma remains elusive but the continuing advances in management may significantly prolong survival in affected patients.

Novel therapeutic approaches for multiple myeloma

Multiple myeloma (MM) affects 15,000 new patients annually in the US, with 50,000 total patients, and remains incurable. Our preliminary in vitro and animal studies suggest a role for MM-host interactions in regulating MM cell growth, drug resistance, and migration in the bone marrow. Importantly, treatment strategies which target mechanisms whereby MM cells grow and survive in the bone marrow, including thalidomide and its potent immunomodulatory derivatives and proteasome inhibitor PS-341, can overcome classical drug resistance in preclinical and early clinical studies.

Treatment of acute promyelocytic leukemia and other hematologic malignancies with arsenic trioxide: review of clinical and basic studies

Acute promyelocytic leukemia (APL) is now the most potentially curable subtype of acute myeloid leukemia in adults because of the introduction of novel approaches in the management of this disease. All-trans-retinoic acid (ATRA)-based therapy is now the first-choice treatment of patients presenting with de novo APL, and clinical studies have shown that nearly all patients who receive ATRA therapy achieve complete remission. However, approximately 20% to 30% of APL patients eventually have relapses with resistance to further ATRA treatment. Arsenic trioxide (As2O3 [ATO]) has been established as highly effective therapy for patients with APL, even for those with disease refractory to ATRA. Furthermore, results of recent studies have suggested a broad therapeutic potential for ATO in the treatment of hematologic malignancies beyond APL. In this review, we discuss the clinical activity and multiple mechanisms of ATO therapy in the management of APL and other hematologic neoplasms.

Role of CD31/platelet endothelial cell adhesion molecule-1 expression in in vitro and in vivo growth and differentiation of human breast cancer cells

Breast ductal carcinoma in situ is an intraductal proliferation of malignant epithelial cells that diffuse within the ductal system without stromal invasion. Our finding that a subset of these tumors express CD31/platelet endothelial cell adhesion molecule-1 suggests that breast cancer represents an informative model for studying the involvement of the molecule in the morphogenesis, differentiation, and diffusion of this disease. Transfection of CD31 in MDA-MB-231 cells caused reduction in growth, loss of CD44, and acquisition of a ductal morphology. The same effects were maintained in vivo, in which CD31(+) tumors grew with in situ-like aspects, papillary differentiation, and a secretory phenotype. CD44 was down-modulated, with the CD31(+) cells blocked in the G(1) phase. The morphology was highly similar to what was observed in some human CD31(+) ductal carcinomas in situ. MDA-MB-231 mock cells grew in solid sheets, lacking stromal material, and displaying high levels of CD44 and proliferation. CD31(+) cells acquired motility characteristics in in vitro assays, a finding confirmed in vivo by the diffusion of human tumor cells throughout the normal ducts residual in the murine mammary gland. In conclusion, CD31 expression reverts the undifferentiated morphology and aggressive behavior of MDA-MB-231 cells, indicating its active role in the morphogenesis of breast ductal in situ carcinomas.

Molecular mechanisms of novel therapeutic approaches for multiple myeloma

Multiple myeloma remains largely incurable despite conventional and high-dose therapies, and so novel biologically based treatment approaches are urgently required. Recent studies have characterized the molecular mechanisms by which multiple myeloma cell-host bone-marrow interactions regulate tumour cell growth, survival and migration in the bone-marrow microenvironment. These studies have not only enhanced our understanding of disease pathogenesis, but have also provided the framework for a new treatment model that targets the multiple myeloma cell in its bone-marrow microenvironment to overcome drug resistance and improve patient outcome.

Nontraditional cytotoxic therapies for relapsed/refractory multiple myeloma

Multiple myeloma remains an incurable disease, with median survival rates of 4-6 years even with aggressive, high-dose chemotherapy, bone marrow transplantation, and intensive supportive care. Additionally, multiple myeloma is primarily a disease of the elderly, many of whom cannot tolerate aggressive chemotherapy. Thus, newer treatments with good safety profiles are needed to improve the quality of responses and, hopefully, to translate into prolonged progression and overall survival. The pathophysiology of multiple myeloma is complex, involving many pathways and interactions among cytokines, adhesion molecules, angiogenesis, and mechanisms of resistance, which, taken together, provide multiple targets for novel therapeutic modalities. Agents currently under investigation for treating multiple myeloma include thalidomide and its successors, PS-341, and arsenic trioxide. Thalidomide and immunomodulatory drugs both exhibit activity against multiple myeloma by affecting different levels of the immune system. PS-341 is a proteasome inhibitor that halts the cell cycle, resulting in apoptosis; it also inhibits a key transcription factor and may have antiangiogenic activity. Arsenic trioxide activates multicellular mechanisms to induce apoptosis, inhibit angiogenesis, and stimulate immune responses. Preclinical and early clinical data suggest that combination regimens should be pursued, given the different mechanisms of action of these compounds on the immune system and their non-overlapping toxicities at low dosages.

Advances in the management of acute promyelocytic leukemia and other hematologic malignancies with arsenic trioxide

Acute promyelocytic leukemia (APL), once considered the most devastating subtype of acute myeloid leukemia, is now the most treatable of all subtypes as a result of intensive research into its molecular pathogenesis. This research has led to a rational approach to treatment in which the use of the differentiating agent all-trans-retinoic acid (ATRA) has proven to be effective first-line treatment for inducing complete remission. Arsenic trioxide (ATO) is currently used to treat relapsed disease, further enhancing survival rates in a patient population for which limited salvage options exist. This review discusses the molecular mechanisms responsible for development of APL and the evolution of treatment options over the last three decades, including the major advances using ATRA and ATO in the last 12 years. The mechanism of action of ATO is also described in view of this agent's potential for broader therapeutic application in a variety of hematologic malignancies.

Novel therapies for multiple myeloma

Multiple myeloma (MM) continues to evade cure by conventional therapies, increasing the urgency for new, biologically based treatments. Reviewed in this discussion are novel chemotherapies under clinical trial that capitalize upon greater comprehension of tumor pathophysiology. In targeting tumor biology, these therapies serve as a model of treatment with great potential for improving outcomes in patients with MM.

Novel biologically based therapeutic strategies in myeloma

Multiple myeloma remains incurable despite advances in conventional chemotherapy and wider applicability of high dose chemotherapy with single and/or tandem autologous peripheral blood stem cell transplantation. Although a complete remission rate of 41% and an event-free survival of 43 months have been reported after tandem transplantation, it is highly unlikely that further improvements in the outcome of multiple myeloma will be achieved by escalating cytotoxic chemotherapy alone. Novel biologically based therapies are therefore urgently required. Targeted therapeutic approaches based on: identification of genetic abnormalities in malignant plasma cells; interrupting growth of myeloma cells; triggering apoptotic signaling cascades in tumor cells; modulating growth and survival of multiple myeloma cells in the bone marrow microenvironment, i.e. angiogenesis and cytokine networks; enhancing allogeneic and autologous antimyeloma immunity; and characterizing newer myeloma antigens for serotherapy are under development. These therapies offer great promise, used alone/or in combination with conventional treatment approaches, to improve the outcome in this disease in newly diagnosed/refractory or relapsed patients with multiple myeloma.

Phosphatidylinositol 3-kinases are involved in the all-trans retinoic acid-induced upregulation of CD38 antigen on human haematopoietic cells

All-trans retinoic acid (ATRA) is a specific inducer of CD38 antigen on marrow CD34+ cells as well as on blast cells in acute promyelocytic and myeloblastic leukaemia. The CD38 antigen contributes to the control of blast cell proliferation, and the upregulation of CD38 might constitute an element in the pathogenesis of retinoic acid syndrome. The aim of this study was to determine whether phosphoinositide 3-kinase (PI3-K) is involved in the modification of CD38 antigen expression on myeloid cells, as PI3-K plays a major role in the ATRA-induced granulocytic differentiation of HL-60 cells. We evaluated the effects of PI3-K inhibitors (wortmannin and LY294002) on the levels of CD38 antigen and mRNA in HL-60 and normal marrow CD34+ cells exposed to ATRA (1 micromol/l). The inhibitors prevented increase in CD38 mRNA expression and the overexpression of membrane CD38 antigen, without modification of the cytoplasmic level of this antigen. Interestingly, PI3-K activity was also necessary for CD38 expression on normal marrow CD34+ cells and for the ATRA-induced upregulation of CD157, a CD38-related antigen. In conclusion, PI3-K activity plays an essential role in the regulation of CD38 expression on human haematopoietic cells, and might constitute an interesting therapeutic target in haematological disorders involving CD38 overexpression.

Treatment of post-transplant lymphomas with anti-B-cell monoclonal antibodies

The treatment of post-transplant lymphomas still needs major improvements in order to put the patient in remission and to retain graft function. Chemotherapy is far too toxic in these patients. A more specific treatment such as anti-B-cell monoclonal antibody is very promising. The cytotoxic effect of antibody relies mainly on complement-induced and antibody-dependent cellular cytotoxicity; apoptosis may also induce tumor cell death. B-cell antigens expressed on the cell surface are the targets of antibody attack; some specificities may be chosen because of their level of expression or because of signaling induced within the cell. Anti-B-cell antibodies can be produced by genetic engineering in order to be humanized or to carry bispecific Fabs. The efficacy and safety of anti-B-cell monoclonal antibodies (mAbs) in transplant patients have been proven with different antibodies such as anti-CD21/CD24 mAb, anti-CD38 mAb and anti-CD20 mAb. In a retrospective analysis of different centers in France, rituximab (anti-CD20 mAb, Roche Products) achieved an overall 69% remission rate in 34 organ and bone-marrow transplant patients. But the conditions of use of antibody must be better defined, particularly with regard to the immunosuppressive therapy, the type of tumor and the dose of antibody. We must also improve our understanding of the in vivo mechanisms of action of antibody to develop more efficient antibody constructs.

Arsenic trioxide and breast cancer: analysis of the apoptotic, differentiative and immunomodulatory effects

Arsenic trioxide (As2O3) is used clinically to treat acute promyelocytic leukemia and has activity in vitro against several solid tumour cell lines, where induction of differentiation and apoptosis are the prime effects. To investigate the potential therapeutic application of As2O3 to breast cancer, we analysed the effects of As2O3 on the growth of four human breast cancer cell lines: MCF7, MDA-MB-231, T-47D and BT-20. Cells were cultured in 0.5, 2 and 5 microM AS2O3, a range of pharmacologically achievable concentrations of AS2O3. At > or = 2 microM, AS2O3 rapidly induced cell death by apoptosis in MCF7 and MDA-MB-231 while T-47D and BT-20 were partially resistant. At 0.5 microM, As2O3 was subapoptotic but induced features of differentiation consisting in upregulation of ICAM-1 (CD54), a marker of mammary epithelial differentiation, and cell cultures appeared morphologically more organized. Furthermore, we demonstrate by standard cytotoxicity assays that As2O3 treatment can augment breast cancer cell lysis by lymphokine-activated killer cells and demonstrate an important role of the ICAM-1/LFA-1 interaction in this process. This additional activity of As2O3 could translate into improved antitumour immunosurveillance in vivo. In conclusion, As2O3 induced varying degrees of differentiation, apoptosis and lysis in these model cell lines, and may be a promising adjuvant to current treatments of breast cancer by virtue of its triple apoptotic, differentiative and immunomodulatory effects.

Multiple myeloma: present and future

Multiple myeloma is a clonal B-cell tumor of slowly proliferating plasma cells within the bone marrow. Among hematologic malignancies, it constitutes 10% of the cancers and ranks as the second most frequently occurring hematologic cancer in the United States, after non-Hodgkin lymphoma. Interleukin-6 is an important cytokine in myeloma cell growth and proliferation. Close cell-to-cell contact between myeloma cells and the bone marrow stromal cells triggers a large amount of interleukin-6 production, which supports the growth of these cells, as well as protecting them from apoptosis induced by dexamethasone and other chemotherapeutic agents. Therapies modulating the tumor and its microenvironment are being actively pursued with the goal of converting multiple myeloma to a chronic disease with the patients maintaining a normal lifestyle.

Arsenic trioxide, a therapeutic agent for APL

Acute promyelocytic leukemia (APL) is an interesting model in cancer research, because it can respond to the differentiation/apoptosis induction therapy using all-trans retinoic acid (ATRA) and arsenic trioxide (As(2)O(3)). Over the past 5 years, it has been well demonstrated that As(2)O(3) induces a high complete remission (CR) rate in both primary and relapsed APL patients (around 85 to 90%). The side effects are mild to moderate in relapsed patients, while severe hepatic lesions have been found in some primary cases. After CR obtained in relapsed patients, chemotherapy in combination with As(2)O(3) as post-remission therapy has given better survival than those treated with As(2)O(3) alone. The effect of As(2)O(3) has been shown to be related to the expression of APL-specific PML-RARalpha oncoprotein, and there is a synergistic effect between As(2)O(3) and ATRA in an APL mouse model. Cell biology studies have revealed that As(2)O(3) exerts dose-dependent dual effects on APL cells. Apoptosis is evident when cells are treated with 0.5 approximately 2.0 microM of As(2)O(3) while partial differentiation is observed using low concentrations (0.1 approximately 0.5 microM) of the drug. The apoptosis-inducing effect is associated with the collapse of mitochondrial transmembrane potentials in a thiol-dependent manner, whereas the mechanisms underlying APL cell differentiation induced by low dose arsenic remain to be explored. Interestingly, As(2)O(3) over a wide range of concentration (0.1 approximately 2.0 microM) induces degradation of a key leukemogenic protein, PML-RARalpha, as well as the wild-type PML, thus setting up a good example of targeting therapy for human cancers.