Clinical study of 9-cis retinoic acid (LGD1057) in acute promyelocytic leukemia

Emerging role of cancer stem cells in the biology and treatment of ovarian cancer: basic knowledge and therapeutic possibilities for an innovative approach

In 2013 there will be an estimated 22,240 new diagnoses and 14,030 deaths from ovarian cancer in the United States. Despite the improved surgical approach and the novel active drugs that are available today in clinical practice, about 80% of women presenting with late-stage disease have a 5-year survival rate of only 30%. In the last years a growing scientific knowledge about the molecular pathways involved in ovarian carcinogenesis has led to the discovery and evaluation of several novel molecular targeted agents, with the aim to test alternative models of treatment in order to overcome the clinical problem of resistance. Cancer stem cells tend to be more resistant to chemotherapeutic agents and radiation than more differentiated cellular subtypes from the same tissue. In this context the study of ovarian cancer stem cells is taking on an increasingly important strategic role, mostly for the potential therapeutic application in the next future. In our review, we focused our attention on the molecular characteristics of epithelial ovarian cancer stem cells, in particular on possible targets to hit with targeted therapies.

Cancerous ovarian stem cells: obscure targets for therapy but relevant to chemoresistance

Chemotherapy with platinum and taxanes is the first line of treatment for all epithelial ovarian cancer (EOC) patients after debulking surgery. Even though the treatment is initially effective in 80% of patients, recurrent cancer is inevitable in the vast majority of cases. Emerging evidence suggests that some tumor cells can survive chemotherapy by activating the self-renewal pathways resulting in tumor progression and clinical recurrence. These defined population of cells commonly termed as "cancer stem cells" (CSC) may generate the bulk of the tumor by using differentiating pathways. These cells have been shown to be resistant to chemotherapy and, to have enhanced tumor initiating abilities, suggesting CSCs as potential targets for treatment. Recent studies have introduced a new paradigm in ovarian carcinogenesis which proposes in situ carcinoma at the fimbrial end of the fallopian tube to generate high-grade serous ovarian carcinomas, in contrast to ovarian cortical inclusion cysts (CIC) which produce borderline and low grade serous, mucinous, endometrioid, and clear cell carcinomas. This review summarizes recent advances in our understanding of the cellular origin of EOC and the molecular mechanisms defining the basis of CSC in EOC progression and chemoresistance. Using a model ovarian cancer cell line, we highlight the role of CSC in response to chemotherapy, and relate how CSCs may impact on chemoresistance and ultimately recurrence. We also propose the molecular targeting of CSCs and suggest ways that may improve the efficacy of current chemotherapeutic regimens needed for the management of this disease.

Ovarian cancer stem cells: a new target for cancer therapy

Ovarian cancer is a highly lethal disease among all gynecologic malignancies and is the fifth leading cause of cancer-related death in women. Although the standard combination of surgery and chemotherapy was initially effective in patients with ovarian cancer, disease relapse commonly occurred due to the generation of chemoresistance. It has been reported that cancer stem cells (CSCs) are involved in drug resistance and cancer recurrence. Over the past decades, increasing studies have been done to identify CSCs from human ovarian cancer cells. The present paper will summarize different investigations on ovarian CSCs, including isolation, mechanisms of chemoresistance, and therapeutic approaches. Although there are still numerous challenges to translate basic research to clinical applications, understanding the molecular details of CSCs is essential for developing effective strategies to prevent ovarian cancer and its recurrence.

Overcoming challenges of ovarian cancer stem cells: novel therapeutic approaches

Understanding the genetic and molecular mechanisms of ovarian cancer has been the focus of research efforts working toward the greater goal of improving cancer therapy for patients with residual disease after initial treatment with conventional surgery and neoadjuvant chemotherapy. The focus of this review will be centered on new therapeutic strategies based on Cancer Stem Cells studies of chemoresistant subpopulations, the prevention of metastasis, and individualized therapy in order to find the most successful combination of treatments to effectively treat human ovarian cancer. We reviewed recent literature (1993-2011) of novel treatment approaches to ovarian cancer stem cells. As the focus of ovarian cancer investigation has centered on the cancer stem cell model and the complexities that it presents in the development of effective treatments, the future of treating ovarian cancer lies in utilizing individualized treatment systems that include enhancing existing treatments, aiming for novel therapy targets, managing the plasticity of stem cells to induce cellular differentiation, and regulating oncogenic signaling pathways.

Treatment of acute promyelocytic leukemia by retinoids

We review the role of all-trans retinoic acid (ATRA) in the treatment of acute promyelocytic leukemia (APL). The combination of ATRA and conventional anthracycline-ARA-C chemotherapy (CT) has clearly demonstrated its superiority over CT alone (in terms of relapse and survival) in newly diagnosed APL. Combination treatment probably also reduces the incidence of initial failures, and complete remission (CR) rates greater than 90% are now regularly reported in large multicenter trials. Some randomized studies strongly suggest that prolonged maintenance treatment (for 1 or 2 years) with ATRA and low-dose CT, and possibly very early introduction of anthracycline CT during induction treatment, may reduce the incidence of relapse. With those treatments, the relapse risk appears to be only 10%-15%, although it remains greater in patients who initially have high white blood cell counts (often associated with variant M3 morphology, short bcr3 isoform, etc.) and patients with residual disease detectable by RT-PCR at the end of consolidation courses. In those patients, addition of arsenic derivatives to induction or consolidation treatment (or both treatments together) may prove useful and is currently being tested. ATRA syndrome (now generally called APL differentiation syndrome, as it is also seen with arsenic derivatives) remains the major side effect of ATRA treatment. It occurs in 10%-15% of patients and is currently fatal in at least 10% of them. Rapid onset of CT or high dose steroids (or both) should improve its outcome. A sizeable proportion of APL patients who relapse after ATRA and CT can be durably salvaged by the same treatment followed by allogeneic or autologous stem cell transplantation, provided the transplant (in the autologous setting) is RT-PCR-negative. However, in relapsing APL arsenic derivatives (mainly arsenic trioxide) are now considered to be the reference treatment. Some of the current issues with ATRA treatment in newly diagnosed APL include whether ATRA has a role during consolidation treatment and whether arabinoside (AraC) is required in addition to anthracyclines in the chemotherapy combined to ATRA.

Retinoic-acid-induced apoptosis in leukemia cells

Retinoic acid (RA) cures more than 75% of patients with acute promyelocytic leukemia (APL). Here, we review the various anti-cancer activities of retinoids and rexinoids, alone and in combination with other drugs, with emphasis on the RA-dependent induction of a cancer-cell-selective apoptosis signaling pathway to which multiple anti-cancer signals converge. These findings identify the TRAIL (tumor-necrosis-factor-related apoptosis-inducing ligand) pathway as a central cell-autonomous anti-cancer weapon that can act independently of the immune system.

Notch signaling in neuroblastoma

Neuroblastoma is a pediatric tumor that originates from precursor cells of the sympathetic nervous system that have discontinued their normal differentiation program. This review is focused on involvement of the Notch signaling cascade in the process of differentiation in neuroblastoma cells and normal cells of the sympathetic nervous system. Hypoxia induces dedifferentiation of neuroblastoma cells in vivo and in vitro, and under oxygen-compromised conditions the Notch cascade is activated. This activation might promote development of the dedifferentiated phenotype. The implications of these observations for tumor biology are also discussed.

Treatment of acute promyelocytic leukemia: strategy toward further increase of cure rate

Acute promyelocytic leukemia (APL) has become a curable disease by all-trans retinoic acid (ATRA)-based induction therapy followed by two or three courses of consolidation chemotherapy. Currently around 90% of newly diagnosed patients with APL achieve complete remission (CR) and over 70% of patients are curable. To further increase the CR and cure rates, detection and diagnosis of this disease at its early stage is very important, hopefully before the appearance of APL-associated coagulopathy. In induction therapy, concomitant chemotherapy is indispensable, except for patients with low initial leukocyte counts. Prophylactic use of intrathecal methotrexate and cytarabine should be done, particularly for patients with hyperleukocytosis. If patients relapse hematologically or even molecularly, arsenic trioxide will be the treatment of choice under careful electrocardiogram monitoring. Am80, liposomal ATRA, gemtuzumab ozogamicin or ATRA in combination with cytotoxic drugs may be used at this stage or later. Allogeneic SCT will be the treatment of choice after patients of age <50 years have relapsed, provided that they have HLA-identical family donors or DNA-identical unrelated donors.

Retinoic acid resistance in acute promyelocytic leukemia

Primary resistance of PML-RARalpha-positive acute promyelocytic leukemia (APL) to the induction of clinical remission (CR) by all-trans retinoic acid (ATRA) is rare but markedly increases in frequency after > or =2 relapses from chemotherapy-induced CRs. Nevertheless, even in de novo cases, the primary response of ATRA-naive cases is variable by several measures, suggesting involvement of heterogeneous molecular elements. Secondary, acquired ATRA resistance occurs in most patients treated with ATRA alone and in many patients who relapse from combination ATRA chemotherapy regimens despite limited ATRA exposure. Although early studies suggested that an adaptive hypercatabolic response to pharmacological ATRA levels is the principal mechanism of ATRA resistance, recent studies suggest that molecular disturbances in APL cells have a predominant role, particularly if disease relapse occurs a few months after discontinuing ATRA therapy. This review summarizes the systemic and APL cellular elements that have been linked to clinical ATRA resistance with emphasis on identifying areas of deficient information and important topics for further investigation. Overall, the subject review strongly supports the hypothesis that, although APL is an infrequent and nearly cured disease, much can be gained by understanding the complex relationship of ATRA resistance to the progression and relapse of APL, which has important implications for other leukemias and malignancies.

Pharmacokinetic study of all-trans-retinoyl-beta-D-glucuronide in Sprague-Dawley rats after single and multiple intravenous administration(s)

All-trans-retinoyl-beta-D-glucuronide (RAG) is an endogenous active metabolite of all-trans-retinoic acid (ATRA). In the present study, the pharmacokinetics of RAG was examined after the administration of a single intravenous does (5, 10, or 15 micromol/kg) and of multiple daily intravenous doses (5 micromol/kg) to rats for 8 days. The plasma concentrations of RAG and ATRA were measured by a reverse-phase HPLC method. A rapid distribution phase of approximately 1 h was observed in all of the rats after single or multiple doses. Thereafter, RAG was eliminated through a first-order process, in accord with a typical two-compartment first order pharmacokinetic profile. After single intravenous doses, the AUC of RAG increased proportionally with the dose and the clearance remained unchanged within the tested doses. There was no statistical significant difference in distribution rate constants from central compartment to peripheral compartment (K(12)) and from peripheral compartment to central compartment (K(21)) between different doses. However, as the dose increased from 5 micromol/kg to 10 micromol/kg, the volume of distribution at the steady state (V(ss)) and the volume of peripheral compartment (V(p)) decreased significantly (p < 0.05) from 1.290 +/- 0.269, 0.928 +/- 0.232. L/kg to 0.961 +/- 0.149, 0.647 +/- 0.107 L/kg, respectively. V(ss) and V(p) at a dose of 15 micromol/kg (0.924 +/- 0.187, 0.698 +/- 0.165 L/kg) were not significantly different from that at 10 micromol/kg. Thus, RAG might saturate the tissue-binding sites at higher doses. ATRA was detected as a metabolite of RAG at low levels (usually < 0.05 microM) only in the first 2 h after intravenous administration. RAG clearly was not extensively hydrolyzed to ATRA in our study. After multiple daily intravenous administration of RAG, the clearance (Cl) and the elimination rate constant (K(10)) remained unchanged (p > 0.05), indicating that long-term daily administration of RAG did not induce its accelerated metabolism. However, K(12), V(p), and V(ss) declined significantly (p < 0.05) from 1.67 +/- 0.54 h(-1), 0.928 +/- 0.232 L/kg, and 1.290 +/- 0.269 L/kg to 0.96 +/- 0.48 h(-1), 0.494 +/- 0.147 L/kg, and 0.818 +/- 0.187 L/kg, respectively. Therefore, long-term daily dosing of RAG seemed to decrease its distribution profile. Although the AUC of RAG did not change significantly after multiple dosing, the AUC of ATRA after RAG dosing significantly declined (p < 0.05) from 0.032 +/- 0.019 microM x h to 0.010 +/- 0.006 microM x h. The decline in the AUC of ATRA might reflect an increase in its uptake by tissue and/or in its metabolism. Because enhanced clearance is not associated with RAG after multiple administrations, RAG could be considered as an alternate to ATRA in appropriate clinical applications.

Retinoid therapy of childhood cancer

In vitro studies that showed RA could cause growth arrest and differentiation of myelogenous leukemia and neuroblastoma led to clinical trials of retinoids in APL and neuroblastoma that increased survival for both of those diseases. In the case of APL, ATRA has been the drug of choice, and preclinical and clinical data support direct combinations of ATRA with cytotoxic chemotherapy. For neuroblastoma, a phase I study defined a dose of 13-cis-RA, which was tolerable in patients after myeloablative therapy, and a phase III trial that showed postconsolidation therapy with 13-cis-RA improved EFS for patients with high-risk neuroblastoma. Preclinical studies in neuroblastoma indicate that ATRA or 13-cis-RA can antagonize cytotoxic chemotherapy and radiation, so use of 13-cis-RA in neuroblastoma is limited to maintenance after completion of cytotoxic chemotherapy and radiation. A limitation on the antitumor benefit of ATRA in APL is the marked decrease in drug levels that occurs during therapy as a result of induction of drug metabolism, resulting in a shorter drug half-life and decreased plasma levels. Although early studies sought to overcome the pharmacologic limitations of ATRA therapy in APL, the demonstration that ATO is active against APL in RA-refractory patients has led to a focus on studies employing ATO. Use of 13-cis-RA in neuroblastoma has avoided the decreased plasma levels seen with ATRA. It is likely that recurrent disease seen during or after 13-cis-RA therapy in neuroblastoma is due to tumor cell resistance to retinoid-mediated differentiation induction. Studies in neuroblastoma cell lines resistant to 13-cis-RA and ATRA have shown that they can be sensitive, and in some cases collaterally hypersensitive, to the cytotoxic retinoid fenretinide. Fenretinide induces tumor cell cytotoxicity rather than differentiation, acts independently from RA receptors, and in initial phase I trials has been well tolerated. Clinical trials of fenretinide, alone and in combination with ceramide modulators, are in development.

Treatment of acute promyelocytic leukaemia

We review improvements achieved in the treatment of acute promyelocytic leukaemia (APL) over the last ten years. The combination of all- trans retinoic acid (ATRA) and conventional anthracycline-ARA-C chemotherapy (CT) has clearly demonstrated its superiority over CT alone (in terms of relapse and survival) in newly diagnosed APL. Combination treatment probably also reduces the incidence of initial failures, and complete remission (CR) rates greater than 90% are now regularly reported in large multicentre trials. Some randomized studies strongly suggest than prolonged maintenance treatment (for 1 or 2 years) with ATRA and low dose CT, and possibly very early introduction of anthracycline CT during induction treatment (i.e. not after ATRA) may reduce the incidence of relapse. With those treatments, the risk of relapse appears to be only 10-15%, although it remains greater in patients who initially have white blood cell counts (often associated with variant M(3)morphology, short bcr(3)isoform etc.) and patients with residual disease detectable by RT-PCR at the end of consolidation courses.ATRA syndrome remains the major side effect of ATRA treatment. It occurs in 10-15% of patients and is currently fatal in at least 10% of them. Rapid onset of CT and/or high dose steroids should improve its outcome.A sizeable proportion of APL patients who relapse after ATRA and CT can be durably salvaged by the same treatment followed by allogeneic or autologous stem cell transplantation, provided the transplant (in the autologous setting) is RT-PCR negative. Arsenic trioxide can induce CR in most APL patients refractory to ATRA and CT. It acts mainly by inducing apoptosis of APL cells. A place for arsenic trioxide earlier in the treatment of APL must currently be more precisely defined. Another issue in the treatment of APL is reducing the toxicity of first line treatment without increasing the relapse risk. Preliminary findings suggest that this could be achieved by consolidation CT using an anthracycline alone, without cytarabine.

All-trans retinoic acid and chemotherapy in the treatment of acute promyelocytic leukemia

All-trans retinoic acid (ATRA) can induce complete remission (CR) in most patients with acute promyelocytic leukemia (APL) through in vivo differentiation of APL-blasts. However, it cannot eliminate the leukemic clone and must be used in combination with anthracycline-based chemotherapy. Experience accumulated over the last 10 years has clearly shown that the combination of ATRA and chemotherapy gave better survival than chemotherapy alone in newly diagnosed APL because of fewer relapses and a slightly higher CR rate. It is also strongly suggested that maintenance treatment with ATRA, and possibly with low-dose chemotherapy, can further reduce the incidence of relapse. Overall, more than 90% of patients with newly diagnosed APL can achieved CR, and about 75% can be cured by the combination of ATRA and chemotherapy. ATRA syndrome remains the major side effect of ATRA treatment, which should be prevented by addition of chemotherapy and/or dexamethasone in case of increasing white blood cell (WBC) counts. Current issues in the treatment of newly diagnosed APL include the role of early addition of chemotherapy to ATRA, whether or not ara-C is useful in combination with anthracycline, and a possible interest of arsenic trioxide during consolidation in patients remaining at relatively high risk of relapse.

Oral 9-cis retinoic acid (Alitretinoin) in the treatment of myelodysplastic syndromes: results from a pilot study

A multicenter phase II study was initiated to investigate the efficacy, toxicity and tolerability of an oral regimen of 9-cis retinoic acid (9CRA) as a differentiation-inducing agent stimulating both retinoic acid receptor (RAR) and retinoic X receptor (RXR). Thirty patients with myelodysplastic syndromes (MDS) were enrolled into the study. The MDS subtypes were distributed as follows: 14 refractory anaemia (RA), four refractory anaemia with ringed sideroblasts (RARS), and 12 refractory anaemia with excess blasts (RAEB). The age ranged from 40 to 81 years (median 70). None of these had previously received treatment for MDS other than supportive therapy. 9CRA (Alitretinoin capsules, kindly provided by Allergan-Ligand Retinoid Therapeutics) was given daily at 60 mg/m2 p.o. for 1 week, followed by an intra-patient escalation to 100 mg/m2 during the second week, up to a maximum of 140 mg/m2. The planned treatment duration was 48 weeks. Twenty-five were available for assessment. One patient (4%) with RA achieved complete hematological remission. Four (16%), two with RA, two with RAEB, had minor responses resulting in decreased transfusion requirements or increased neutrophils. Thus, the overall response rate was 20% in evaluable patients with MDS and 17% in the study group on an intention-to-treat basis. The most frequent side-effects included headache (77%), dry skin (57%), arthralgias (30%), and rash (23%). In conclusion, although modest responses were noted in this study, the treatment tolerability was suboptimal. It is conceivable that a lower dosage schedule may be efficacious and better tolerated so enabling prolonged exposure which may be required to induce a differentiation effect.

The biologic basis for the use of retinoids in cancer prevention and treatment

Retinoids (vitamin A and related molecules) are biologic agents that have demonstrated, in preclinical and clinical models, potent activity in the prevention and treatment of a variety of malignancies. Presented in this article is a review of recent clinical studies and correlative laboratory findings that advance our understanding of the biologic basis for the use of retinoids in cancer prevention and treatment.