Differentiation therapy in acute myelogenous leukemia (non-APL)

Neratinib impairs function of m6A recognition on AML1-ETO pre-mRNA and induces differentiation of t (8;21) AML cells by targeting HNRNPA3

Acute myeloid leukemia (AML) is frequently linked to genetic abnormalities, with the t (8; 21) translocation, resulting in the production of a fusion oncoprotein AML1-ETO (AE), being a prevalent occurrence. This protein plays a pivotal role in t (8; 21) AML's onset, advancement, and recurrence, making it a therapeutic target. However, the development of drug molecules targeting AML1-ETO are markedly insufficient, especially used in clinical treatment. In this study, it was uncovered that Neratinib could significantly downregulate AML1-ETO protein level, subsequently promoting differentiation of t (8; 21) AML cells. Based on "differentiated active" probes, Neratinib was identified as a functional inhibitor against HNRNPA3 through covalent binding. The further studies demonstrated that HNRNPA3 function as a putative m6A reader responsible for recognizing and regulating the alternative splicing of AML-ETO pre-mRNA. These findings not only contribute to a novel insight to the mechanism governing post-transcriptional modification of AML1-ETO transcript, but also suggest that Neratinib would be promising therapeutic potential for t (8; 21) AML treatment.

Fatty acid synthase (FASN) signalome: A molecular guide for precision oncology

The initial excitement generated more than two decades ago by the discovery of drugs targeting fatty acid synthase (FASN)-catalyzed de novo lipogenesis for cancer therapy was short-lived. However, the advent of the first clinical-grade FASN inhibitor (TVB-2640; denifanstat), which is currently being studied in various phase II trials, and the exciting advances in understanding the FASN signalome are fueling a renewed interest in FASN-targeted strategies for the treatment and prevention of cancer. Here, we provide a detailed overview of how FASN can drive phenotypic plasticity and cell fate decisions, mitochondrial regulation of cell death, immune escape and organ-specific metastatic potential. We then present a variety of FASN-targeted therapeutic approaches that address the major challenges facing FASN therapy. These include limitations of current FASN inhibitors and the lack of precision tools to maximize the therapeutic potential of FASN inhibitors in the clinic. Rethinking the role of FASN as a signal transducer in cancer pathogenesis may provide molecularly driven strategies to optimize FASN as a long-awaited target for cancer therapeutics.

Extirpating the cancer stem cell hydra: Differentiation therapy and Hyperthermia therapy for targeting the cancer stem cell hierarchy

Ever since the discovery of cancer stem cells (CSCs), they have progressively attracted more attention as a therapeutic target. Like the mythical hydra, this subpopulation of cells seems to contribute to cancer immortality, spawning more cells each time that some components of the cancer cell hierarchy are destroyed. Traditional modalities focusing on cancer treatment have emphasized apoptosis as a route to eliminate the tumor burden. A major problem is that cancer cells are often in varying degrees of dedifferentiation contributing to what is known as the CSCs hierarchy and cells which are known to be resistant to conventional therapy. Differentiation therapy is an experimental therapeutic modality aimed at the conversion of malignant phenotype to a more benign one. Hyperthermia therapy (HT) is a modality exploiting the changes induced in cells by the application of heat produced to aid in cancer therapy. While differentiation therapy has been successfully employed in the treatment of acute myeloid leukemia, it has not been hugely successful for other cancer types. Mounting evidence suggests that hyperthermia therapy may greatly augment the effects of differentiation therapy while simultaneously overcoming many of the hard-to-treat facets of recurrent tumors. This review summarizes the progress made so far in integrating hyperthermia therapy with existing modules of differentiation therapy. The focus is on studies related to the successful application of both hyperthermia and differentiation therapy when used alone or in conjunction for hard-to-treat cancer cell niche with emphasis on combined approaches to target the CSCs hierarchy.

Homoharringtonine-Based Induction Regimen Improved the Remission Rate and Survival Rate in Chinese Childhood AML: A Report From the CCLG-AML 2015 Protocol Study

PURPOSE

Homoharringtonine (HHT) is commonly used for the treatment of Chinese adult AML, and all-trans retinoic acid (ATRA) has been verified in acute promyelocytic leukemia (APL). However, the efficacy and safety of HHT-based induction therapy have not been confirmed for childhood AML, and ATRA-based treatment has not been evaluated among patients with non-APL AML.

PATIENTS AND METHODS

This open-label, multicenter, randomized Chinese Children's Leukemia Group-AML 2015 study was performed across 35 centers in China. Patients with newly diagnosed childhood AML were first randomly assigned to receive an HHT-based (H arm) or etoposide-based (E arm) induction regimen and then randomly allocated to receive cytarabine-based (AC arm) or ATRA-based (AT arm) maintenance therapy. The primary end points were the complete remission (CR) rate after induction therapy, and the secondary end points were the overall survival (OS) and event-free survival (EFS) at 3 years.

RESULTS

We enrolled 1,258 patients, of whom 1,253 were included in the intent-to-treat analysis. The overall CR rate was significantly higher in the H arm than in the E arm (79.9% v 73.9%, P = .014). According to the intention-to-treat analysis, the 3-year OS was 69.2% (95% CI, 65.1 to 72.9) in the H arm and 62.8% (95% CI, 58.7 to 66.6) in the E arm (P = .025); the 3-year EFS was 61.1% (95% CI, 56.8 to 65.0) in the H arm and 53.4% (95% CI, 49.2 to 57.3) in the E arm (P = .022). Among the per-protocol population, who received maintenance therapy, the 3-year EFS did not differ significantly across the four arms (H + AT arm: 70.7%, 95% CI, 61.1 to 78.3; H + AC arm: 74.8%, 95% CI, 67.0 to 81.0, P = .933; E + AC arm: 72.9%, 95% CI, 65.1 to 79.2, P = .789; E + AT arm: 66.2%, 95% CI, 56.8 to 74.0, P = .336).

CONCLUSION

HHT is an alternative combination regimen for childhood AML. The effects of ATRA-based maintenance are comparable with those of cytarabine-based maintenance therapy.

Multi-Target Neural Differentiation (MTND) Therapeutic Cocktail to Suppress Brain Tumor

Brain tumors have been proved challenging to treat. Here we established a Multi-Target Neural Differentiation (MTND) therapeutic cocktail to achieve effective and safe treatment of brain malignancies by targeting the important hallmarks in brain cancers: poor cell differentiation and compromised cell cycle. In-vitro and in-vivo experiments confirmed the significant therapeutic effect of our MTND therapy. Significantly improved therapeutic effects over current first-line chemo-drugs have been identified in clinical cells, with great inhibition of the growth and migration of tumor cells. Further in-vivo experiments confirmed that sustained MTND treatment showed a 73% reduction of the tumor area. MTND also induced strong expression of phenotypes associated with cell cycle exit/arrest and rapid neural reprograming from clinical glioma cells to glutamatergic and GABAergic expressing cells, which are two key neuronal types involved in many human brain functions, including learning and memory. Collectively, MTND induced multi-targeted genotypic expression changes to achieve direct neural conversion of glioma cells and controlled the cell cycle/tumorigenesis development, helping control tumor cells' malignant proliferation and making it possible to treat brain malignant tumors effectively and safely. These encouraging results open avenues to developing new therapies for brain malignancies beyond cytotoxic agents, providing more effective medication recommendations with reduced toxicity.

All-trans retinoic acid in anticancer therapy: how nanotechnology can enhance its efficacy and resolve its drawbacks

Introduction: All-trans retinoic acid (ATRA, tretinoin) is the main drug used in the treatment of acute promyelocytic leukemia (APL). Despite its impressive activity against APL, the same could not be clinically observed in other types of cancer. Nanotechnology can be a tool to enhance ATRA anticancer efficacy and resolve its drawbacks in APL as well as in other malignancies.Areas covered: This review covers ATRA use in APL and non-APL cancers, the problems that were found in ATRA therapy and how nanoencapsulation can aid to circumvent them. Pre-clinical results obtained with nanoencapsulated ATRA are shown as well as the two ATRA products based on nanotechnology that were clinically tested: ATRA-IV® and Apealea®.Expert opinion: ATRA presents interesting properties to be used in anticancer therapy with a notorious differentiation and antimetastatic activity. Bioavailability and resistance limitations impair the use of ATRA in non-APL cancers. Nanotechnology can circumvent these issues and provide tools to enhance its anticancer activities, such as co-loading of multiple drug and active targeting to tumor site.

The important roles of protein SUMOylation in the occurrence and development of leukemia and clinical implications

Leukemia is a severe malignancy of the hematopoietic system, which is characterized by uncontrolled proliferation and dedifferentiation of immature hematopoietic precursor cells in the lymphatic system and bone marrow. Leukemia is caused by alterations of the genetic and epigenetic regulation of processes underlying hematologic malignancies, including SUMO modification (SUMOylation). Small ubiquitin-like modifier (SUMO) proteins covalently or noncovalently conjugate and modify a large number of target proteins via lysine residues. SUMOylation is a small ubiquitin-like modification that is catalyzed by the SUMO-specific activating enzyme E1, the binding enzyme E2, and the ligating enzyme E3. SUMO is covalently linked to substrate proteins to regulate the cellular localization of target proteins and the interaction of target proteins with other biological macromolecules. SUMOylation has emerged as a critical regulatory mechanism for subcellular localization, protein stability, protein-protein interactions, and biological function and thus regulates normal life activities. If the SUMOylation process of proteins is affected, it will cause a cellular reaction and ultimately lead to various diseases, including leukemia. There is growing evidence showing that a large number of proteins are SUMOylated and that SUMOylated proteins play an important role in the occurrence and development of various types of leukemia. Targeting the SUMOylation of proteins alone or in combination with current treatments might provide powerful targeted therapeutic strategies for the clinical treatment of leukemia.

A PDZ Protein MDA-9/Syntenin: As a Target for Cancer Therapy

Melanoma differentiation-associated gene 9 (MDA-9)/Syntenin is a multidomain PDZ protein and identified as a key oncogene in melanoma initially. This protein contains a unique tandem PDZ domain architecture (PDZ1 and PDZ2 spaced by a 4-amino acid linker), an N-terminal domain (NTD) that is structurally uncharacterized and a short C-terminal domain (CTD). The PDZ1 domain is regarded as the PDZ signaling domain while PDZ2 served as the PDZ superfamily domain. It has various cellular roles by regulating many of major signaling pathways in numerous cancertypes. Through the use of novel drug design methods, such as dimerization and unnatural amino acid substitution of inhibitors in our group, the protein may provide a valuable therapeutic target. The objective of this review is to provide a current perspective on the cancer-specific role of MDA-9/Syntenin in order to explore its potential for cancer drug discovery and cancer therapy.

The thymidine dideoxynucleoside analog, alovudine, inhibits the mitochondrial DNA polymerase γ, impairs oxidative phosphorylation and promotes monocytic differentiation in acute myeloid leukemia

Mitochondrial DNA encodes 13 proteins that comprise components of the respiratory chain that maintain oxidative phosphorylation. The replication of mitochondrial DNA is performed by the sole mitochondrial DNA polymerase γ. As acute myeloid leukemia (AML) cells and stem cells have an increased reliance on oxidative phosphorylation, we sought to evaluate polymerase γ inhibitors in AML. The thymidine dideoxynucleoside analog, alovudine, is an inhibitor of polymerase γ. In AML cells, alovudine depleted mitochondrial DNA, reduced mitochondrial encoded proteins, decreased basal oxygen consumption, and decreased cell proliferation and viability. To evaluate the effects of polymerase γ inhibition with alovudine in vivo, mice were xenografted with OCI-AML2 cells and then treated with alovudine. Systemic administration of alovudine reduced leukemic growth without evidence of toxicity and decreased levels of mitochondrial DNA in the leukemic cells. We also showed that alovudine increased the monocytic differentiation of AML cells. Genetic knockdown and other chemical inhibitors of polymerase γ also promoted AML differentiation, but the effects on AML differentiation were independent of reductions in oxidative phosphorylation or respiratory chain proteins. Thus, we have identified a novel mechanism by which mitochondria regulate AML fate and differentiation independent of oxidative phosphorylation. Moreover, we highlight polymerase γ inhibitors, such as alovudine, as novel therapeutic agents for AML.

Histone Acetyltransferase p300/CREB-binding Protein-associated Factor (PCAF) Is Required for All-trans-retinoic Acid-induced Granulocytic Differentiation in Leukemia Cells

Differentiation therapy with all-trans-retinoic acid (ATRA) improves the treatment outcome of acute promyelocytic leukemia (APL); however, the molecular mechanism by which ATRA induces granulocytic differentiation remains unclear. We previously reported that the inhibition of the NAD-dependent histone deacetylase (HDAC) SIRT2 induces granulocytic differentiation in leukemia cells, suggesting the involvement of protein acetylation in ATRA-induced leukemia cell differentiation. Herein, we show that p300/CREB-binding protein-associated factor (PCAF), a histone acetyltransferase (HAT), is a prerequisite for ATRA-induced granulocytic differentiation in leukemia cells. We found that PCAF expression was markedly increased in leukemia cell lines (NB4 and HL-60) and primary APL cells during ATRA-induced granulocytic differentiation. Consistent with these results, the expression of PCAF was markedly up-regulated in the bone marrow cells of APL patients who received ATRA-containing chemotherapy. The knockdown of PCAF inhibited ATRA-induced granulocytic differentiation in leukemia cell lines and primary APL cells. Conversely, the overexpression of PCAF induced the expression of the granulocytic differentiation marker CD11b at the mRNA level. Acetylome analysis identified the acetylated proteins after ATRA treatment, and we found that histone H3, a known PCAF acetylation substrate, was preferentially acetylated by the ATRA treatment. Furthermore, we have demonstrated that PCAF is required for the acetylation of histone H3 on the promoter of ATRA target genes, such as CCL2 and FGR, and for the expression of these genes in ATRA-treated leukemia cells. These results strongly support our hypothesis that PCAF is induced and activated by ATRA, and the subsequent acetylation of PCAF substrates promotes granulocytic differentiation in leukemia cells. Targeting PCAF and its downstream acetylation targets could serve as a novel therapeutic strategy to overcome all subtypes of AML.

Role of TCTP for Cellular Differentiation and Cancer Therapy

The translationally controlled tumor protein (TCTP) is a highly conserved protein that is regulated due to a high number of extracellular stimuli. TCTP has an important role for cell cycle and normal development. On the other side, tumor reversion and malignant transformation have been associated with TCTP. TCTP has been found among the 12 genes that are differentially expressed during mouse oocyte maturation, and an overexpression of this gene was reported in a wide variety of different cancer types. Its antiapoptotic effect is indicated by the interaction with several proapoptotic proteins of the Bcl-2 family and the p53 tumor suppressor protein. In this article, we draw attention to the role of TCTP in cancer, especially, focusing on cell differentiation and tumor reversion, a biological process by which highly tumorigenic cells lose their malignant phenotype. This protein has been shown to be the most strongly downregulated protein in revertant cells compared to the parental cancer cells. Decreased expression of TCTP results either in the reprogramming of cancer cells into reversion or apoptosis. As conventional chemotherapy is frequently associated with the development of drug resistance and high toxicity, the urge for the development of new or additional scientific approaches falls into place. Differentiation therapy aims at reinducing differentiation backward to the nonmalignant cellular state. Here, different approaches have been reported such as the induction of retinoid pathways and the use of histone deacetylase inhibitors. Also, PPARγ agonists and the activation of the vitamin D receptor have been reported as potential targets in differentiation therapy. As TCTP is known as the histamine-releasing factor, antihistaminic drugs have been shown to target this protein. Antihistaminic compounds, hydroxyzine and promethazine, inhibited cell growth of cancer cells and decreased TCTP expression of breast cancer and leukemia cells. Recently, we found that two antihistaminics, levomepromazine and buclizine, inhibited cancer cell growth by direct binding to TCTP and induction of cell differentiation. These data confirmed that TCTP is an exquisite target for anticancer differentiation therapy and antihistaminics have potential to be lead compounds for the direct interaction with TCTP as new inhibitors of human TCTP and tumor growth.

Cancer Stem Cells: Formidable Allies of Cancer

Cancer stem cells (CSC) represent the subpopulation of cells within a tumour showing two fundamental properties of stem cells - self-renewal (the ability to make more of their own kind) and differentiation (the ability to generate diverse cell types present within a tissue). The CSC hypothesis posits that CSCs play an important role in tumour initiation, maintenance and progression. Furthermore, owing to their intrinsic drug resistance, they remain refractory to currently used therapy, thereby contributing to tumour relapse. Thus, targeting or taming CSCs can lead to more effective cancer treatment in the coming decades. In this review, we will discuss about the origin of CSC hypothesis, evidence showing their existence, clinical relevance and translational significance.

Interaction of antihistaminic drugs with human translationally controlled tumor protein (TCTP) as novel approach for differentiation therapy

Translationally controlled tumor protein (TCTP) represents an exquisite target for cancer differentiation therapy, because it was most strikingly down-regulated in tumor reversion experiments. Since TCTP is identical with the histamine releasing factor, antihistamic drugs may inhibit TCTP. Indeed, antihistaminics, such as promethazine, thioridazine, perphemazine and chlorpromazine reveal antiproliferative effects. The aim of this investigation was to study antihistaminic drugs as new TCTP inhibitors to inhibit tumor growth. Levomepromazine and buclizine showed higher in silico binding affinities to TCTP among 12 different antihistaminic compounds including the control drugs, promethazine and hydroxyzine by using Autodock4 and AutodockTools-1.5.7.rc1. Recombinant human TCTP was codon-optimized, expressed in E. coli and purified by chitin affinity chromatography. For experimental validation of in silico data, we applied microscale thermophoresis. Levomepromazine bound with a Kd of 57.2 μM (p < 0.01) and buclizine with a Kd of 433μM (p < 0.01) to recombinant TCTP. Both drugs inhibited MCF-7 breast cancer cell growth in resazurin assays. TCTP expression was down-regulated after treatment with the two drugs. Cell cycle was arrested in the G1 phase without apoptosis as confirmed by the expression of cell cycle and apoptosis-regulating proteins. Annexin V-PI staining and Trypan blue exclusion assay supported that the two drugs are cytostatic rather than cytotoxic. Induction of differentiation with two drugs was detected by the increased appearance of lipid droplets. In conclusion, levomepromazine and buclizine inhibited cancer cell growth by binding to TCTP and induction of cell differentiation. These compounds may serve as lead compounds for cancer differentiation therapy.

Cyanidin induces apoptosis and differentiation in prostate cancer cells

Several natural antioxidants, including anthocyanins, have been reported to have chemotherapeutic activity in vivo and in vitro. The aim of the present study was to delineate the anti-proliferative activity and the cytodifferentiation properties mediated by cyanidin-3-O-β-glucopyranoside (C3G) treatment in the DU145 and LnCap human prostatic cancer cell lines. C3G produced anti-proliferative effects through activation of caspase-3 and induction of p21 protein expression. The reduced cell viability was associated with a clear increase of DNA fragmentation in both cell lines after C3G treatment. Since LnCap and DU145 exhibited differences in sensitivity to C3G treatment, the redox state of these cells was further investigated by estimating the levels of ROS and GSH. C3G antioxidant activity was confirmed only in DU145 cell line. Treatment with C3G increased the levels of tumor suppressor P75NGFR, indicating a possible role of C3G in the acquisition of a normal-like cell phenotype. Results reported in the present study demonstrate that C3G, the most abundant anthocyanin in diet, may represent a new approach and highly effective strategy in reducing carcinogenesis. C3G may be considered a new therapeutic agent with both anti-proliferative and pro-differentiation properties.

Flavonoid 4'-O-Methylkuwanon E from Morus alba Induces the Differentiation of THP-1 Human Leukemia Cells

Aims. In this work we studied cytodifferentiation effects of newly characterized prenyl flavonoid 4′-O-methylkuwanon E (4ME) isolated from white mulberry (Morus alba L.). Main Methods. Cell growth and viability were measured by dye exclusion assay; cell cycle and surface antigen CD11b were monitored by flow cytometry. For the cytodifferentiation of cells the NBT reduction assay was employed. Regulatory proteins were assessed by western blotting. Key Findings. 4ME induced dose-dependent growth inhibition of THP-1 cells, which was not accompanied by toxic effect. Inhibition of cells proliferation caused by 4ME was associated with the accumulation in G1 phase and with downregulation of hyperphosphorylated pRb. Treatment with 4ME led to significant induction of NBT-reducing activity of PMA stimulated THP-1 cells and upregulation expression of differentiation-associated surface antigen CD11b. Our results suggest that monocytic differentiation induced by 4ME is connected with up-regulation of p38 kinase activity. Significance. Our study provides the first evidence that 4ME induces the differentiation of THP-1 human monocytic leukemia cells and thus is a potential cytodifferentiating anticancer agent.

Mitochondrial dependency in progression of acute myeloid leukemia

Acute myeloid leukemia (AML) is a clonal hematopoietic malignant disorder which arises due to dysregulated differentiation, uncontrolled growth and inhibition of apoptosis leading to the accumulation of immature myeloid progenitor in the bone marrow. The heterogeneity of the disease at the molecular and cytogenetic level has led to the identification of several alteration of biological and clinical significance. One of the alterations which have gained attention in recent times is the altered energy and metabolic dependency of cancer originally proposed by Warburg. Mitochondria are important cell organelles regulating cellular energetic level, metabolism and apoptosis which in turn can affect cell proliferation and differentiation, the major manifestations of diseases like AML. In recent times the importance of mitochondrial generated ATP and mitochondrial localized metabolic pathways has been shown to play important role in the progression of AML. These studies have also demonstrated the clinical significance of mitochondrial targets for its effectiveness in combating relapsed or refractory AML. Here we review the importance of the mitochondrial dependency for the progression of AML and the emergence of the mitochondrial molecular targets which holds therapeutic importance.

Survival improvement of poor-prognosis AML/MDS patients by maintenance treatment with low-dose chemotherapy and differentiating agents

We evaluated a maintenance, post-remission treatment with low-dose chemotherapy plus differentiating agents on poor-prognosis acute myeloid leukemia (AML)/myelodysplastic syndrome (MDS) patients ineligible to allografting. Patients had either age over 60 and/or secondary AML, therapy-related AML, previous relapse, high-risk MDS. Forty-five patients received the maintenance therapy based on two alternated schedules: (a) 6-thioguanine + 13-cis retinoic acid + dihydroxylated vitamin D3 and (b) low-dose cytarabine + 6-mercaptopurine + all-trans retinoic acid + dihydroxylated vitamin D3. We compared their outcome, at a median follow-up of 52 months, to that of a matched population of 49 patients who stopped treatments after consolidation. Maintenance group had a lower relapse incidence (70.3 vs. 86.4 % at 5 years p = 0.007) and a longer disease-free survival (median 21.2 vs. 8.7 months, p = 0.017). The relapse reduction improved overall survival: median 40.4 months (35.9 % at 5 years) for maintenance group vs. 15.8 (14.2 % at 5 years) for controls (p = 0.005). At multivariate Cox analysis, both cytogenetic and maintenance therapies resulted independent outcome predictors for overall survival. Maintenance treatment also reduced minimal residual disease (detected by WT1 and CBFβ-MYH11) in five of eight evaluable patients. The present results suggest that our strategy of maintenance therapy might improve the outcome of poor-risk AML/MDS patients.

Effects of differentiation on purinergic and neurotensin-mediated calcium signaling in human HT-29 colon cancer cells

Calcium signaling is a key regulator of processes important in differentiation. In colon cancer cells differentiation is associated with altered expression of specific isoforms of calcium pumps of the endoplasmic reticulum and the plasma membrane, suggesting that differentiation of colon cancer cells is associated with a major remodeling of calcium homeostasis. Purinergic and neurotensin receptor activation are known regulators of cytosolic free Ca(2+) levels in colon cancer cells. This study aimed to assess changes in cytosolic free Ca(2+) levels in response to ATP and neurotensin with differentiation induced by sodium butyrate or culturing post-confluence. Parameters assessed included peak cytosolic free Ca(2+) level after activation; time to reach peak cytosolic free Ca(2+) and the EC50 of dose response curves. Our results demonstrate that differentiation of HT-29 colon cancer cells is associated with a remodeling of both ATP and neurotensin mediated Ca(2+) signaling. Neurotensin-mediated calcium signaling appeared more sensitive to differentiation than ATP-mediated Ca(2+) signaling.

C/EBPα induces highly efficient macrophage transdifferentiation of B lymphoma and leukemia cell lines and impairs their tumorigenicity

Earlier work demonstrated that the transcription factor C/EBPα can convert immature and mature murine B lineage cells into functional macrophages. Testing >20 human lymphoma and leukemia B cell lines, we found that most can be transdifferentiated at least partially into macrophage-like cells, provided that C/EBPα is expressed at sufficiently high levels. A tamoxifen-inducible subclone of the Seraphina Burkitt lymphoma line, expressing C/EBPαER, could be efficiently converted into phagocytic and quiescent cells with a transcriptome resembling normal macrophages. The converted cells retained their phenotype even when C/EBPα was inactivated, a hallmark of cell reprogramming. Interestingly, C/EBPα induction also impaired the cells' tumorigenicity. Likewise, C/EBPα efficiently converted a lymphoblastic leukemia B cell line into macrophage-like cells, again dramatically impairing their tumorigenicity. Our experiments show that human cancer cells can be induced by C/EBPα to transdifferentiate into seemingly normal cells at high frequencies and provide a proof of principle for a potential new therapeutic strategy for treating B cell malignancies.

Specific unsaturated fatty acids enforce the transdifferentiation of human cancer cells toward adipocyte-like cells

Differentiation therapy pursues the discovery of novel molecules to transform cancer progression into less aggressive phenotypes by mechanisms involving enforced cell transdifferentiation. In this study, we examined the identification of transdifferentiating adipogenic programs in human cancer cell lines (HCCLs). Our findings showed that specific unsatturated fatty acids, such as palmitoleic, oleic and linoleic acids, trigger remarkable phenotypic modifications in a large number of human cancer cell lines (HCCLs), including hepatocarcinoma HUH-7, ovarian carcinoma SK-OV-3, breast adenocarcinoma MCF-7 and melanoma MALME-3M. In particular, we characterized a massive biogenesis of lipid droplets (LDs) and up-regulation of the adipogenic master regulator, PPARG, resulting in the transdifferentiation of HCCLs into adipocyte-like cells. These findings suggest the possibility of a novel strategy in cancer differentiation therapy via switching the identity of HCCLs to an adipogenic phenotype through unsaturated fatty acid-induced transdifferentiation.

Differentiation-inducing activity of hydroxycamptothecin on cancer stem-like cells derived from hepatocellular carcinoma

BACKGROUND

Hydroxycamptothecin (HCPT) is an anti-tumor agent that can induce differentiation in human cancer cells. Recent evidence indicates that side population (SP) cells possess characteristics of stem-like cells, and may be capable of initiating tumor growth.

AIMS

The present study investigated the differentiation of cancer stem-like cells derived from hepatocellular carcinoma.

METHODS AND RESULTS

Flow cytometry was used to isolated SP cells from HCC cell line (MHCC97 cells). These SP cells exhibit several stem-like cell characteristics that are distinct from the main population (MP) cells in vitro. After 3 days of induction with a low concentration of HCPT, the SP cells lost their capacity to proliferate and invade, and their tumorigenicity declined. Based on real-time quantitative RT-PCR, we also found that the expression of hepatocyte-specific markers such as α-fetoprotein, albumin, hepatocyte nuclear factor-4 and miR-122 gradually changed during the differentiation of SP cells.

CONCLUSIONS

Our data suggest that a low concentration of HCPT can induce hepatocyte-specific differentiation of cancer stem-like cells from MHCC97 cells, offering a possible therapeutic strategy for the treatment of human malignancies.

Chloroform extract from Moricandia arvensis inhibits growth of B16-F0 melanoma cells and promotes differentiation in vitro

OBJECTIVES

Poor therapeutic results have been reported for treatment of malignant melanoma; therefore in this study we have investigated inhibitory capacity of ethyl acetate, chloroform (Chl) and methanol extracts from Moricandia arvensis on mouse melanoma (B16-F0) and human keratinocyte (HaCaT) cell proliferation. Influence of Chl extract on percentage distribution in cell cycle phases and melanogenesis was also studied.

MATERIAL AND METHODS

Cell viability was determined at various periods using the MTT assay, and flow cytometry was used to analyse effects of Chl extract on progression through the cell cycle and apoptosis. In addition, amounts of melanin and tyrosinase were measured spectrophotometrically at 475 nm.

RESULTS

Chl extract exhibited significant anti-proliferative activity after incubation with the two types of tumour skin cells. Morphological changes in B16-F0 cells, accompanied by increase of tyrosinase activity, and of melanin synthesis were observed, which are markers of differentiation of malignant melanoma cells. Furthermore, cell cycle analysis revealed that B16-F0 cells treated with Chl extract were arrested predominantly in G(1) phase.

CONCLUSION

Chl extract had the ability to reverse malignant melanoma cells from proliferative to differentiated state, thus providing a new perspective in developing novel strategies for prevention and treatment of malignant melanoma, possibly through consumption of the extract in an appropriate cancer prevention diet. Moreover, there is scope for the extract being introduced into cosmetic products as a natural tanning agent.

Silibinin can induce differentiation as well as enhance vitamin D3-induced differentiation of human AML cells ex vivo and regulates the levels of differentiation-related transcription factors

Induction of terminal differentiation is a conceptually attractive approach for the therapy of neoplastic diseases. Although vitamin D derivatives (deltanoids) can induce differentiation of AML cells in vitro, so far deltanoids have not been successfully brought to the clinic, due to the likelihood of life-threatening hypercalcemia. Here, we incubated freshly obtained blood cells from patients with AML with a plant antioxidant (PAOx), silibinin (SIL), alone or together with a deltanoid. Twenty patients with AML (all subtypes except M3) were available for this study, and in 14 (70%), SIL (60 µM) either induced differentiation ex vivo, or enhanced differentiation induced by deltanoids, or both. Interestingly, SIL acting alone induced differentiation only in cases in which chromosome aberrations could not be detected. In eleven samples sufficient material was available for a limited analysis of the underlying events. Quantitative RT-PCR showed that differentiation markers were upregulated at the mRNA level by both SIL and deltanoids, suggesting that intracellular signaling pathways upstream of transcription factors (TFs) were activated by these agents. Western analysis for proteins which function as TFs in deltanoid-induced monocytic differentiation, such as members of Jun and C/EBP families, surprisingly demonstrated that SIL upregulated all these TFs in the cases tested. This suggests that although the presence of SIL may not always be sufficient to induce differentiation, it can serve as a differentiation enabling factor for blasts obtained from a large proportion of patients with AML. Thus, SIL/deltanoid combinations warrant further consideration as preventive/therapeutic regimens in human leukaemia.

New insights in nutritional management and amino acid supplementation in urea cycle disorders

Sodium phenylbutyrate is used in the pharmacological treatment of urea cycle disorders to create alternative pathways for nitrogen excretion. The primary metabolite, phenylacetate, conjugates glutamine in the liver and kidney to form phenylacetylglutamine that is readily excreted in the urine. Patients with urea cycle disorders taking sodium phenylbutyrate have a selective reduction in the plasma concentrations of branched chain amino acids despite adequate dietary protein intake. Moreover, this depletion is usually the harbinger of a metabolic crisis. Plasma branched chain amino acids and other essential amino acids were measured in control subjects, untreated ornithine transcarbamylase deficiency females, and treated patients with urea cycle disorders (ornithine transcarbamylase deficiency and argininosuccinate synthetase deficiency) in the absorptive state during the course of stable isotope studies. Branched chain amino acid levels were significantly lower in treated patients with urea cycle disorders when compared to untreated ornithine transcarbamylase deficiency females or control subjects. These results were replicated in control subjects who had low steady-state branched chain amino acid levels when treated with sodium phenylbutyrate. These studies suggested that alternative pathway therapy with sodium phenylbutyrate causes a substantial impact on the metabolism of branched chain amino acids in patients with urea cycle disorders, implying that better titration of protein restriction can be achieved with branched chain amino acid supplementation in these patients who are on alternative pathway therapy.

Eupatilin exhibits a novel anti-tumor activity through the induction of cell cycle arrest and differentiation of gastric carcinoma AGS cells

In many cases, the process of cancer cell differentiation is associated with the programmed cell death. In the present study, interestingly, we found that eupatilin, one of the pharmacologically active ingredients of Artemisia asiatica that has been reported to induce apoptosis in human gastric cancer AGS cells, also triggers differentiation of these cells. Treatment of AGS cells with eupatilin induced cell cycle arrest at the G(1) phase with the concomitant induction of p21(cip1), a cell cycle inhibitor. This led us to test whether eupatilin may trigger AGS cells to differentiate into the matured phenotypes of epithelial cells and this phenomenon may be coupled to the apoptosis. Eupatilin induced changes of AGS cells to a more flattened morphology with increased cell size, granularity, and mitochondrial mass. It also markedly induced trefoil factor 1 (TFF1), a gene responsible for the gastrointestinal cell differentiation. Eupatilin dramatically induced redistribution of tight junction proteins such as occludin and ZO-1, and F-actin at the junctional region between cells. It also induced phosphorylation of extracellular signal-regulated kinase 2 and p38 kinase. Blockade of ERK signaling by PD098059 or the dominant-negative ERK2 significantly reduced eupatilin-induced TFF1 and p21 expression as well as ZO-1 redistribution, indicating that ERK cascades may mediate eupatilin-induced AGS cell differentiation. Collectively, our results suggest that eupatilin acts as a novel anti-tumor agent by inducing differentiation of gastrointestinal cancer cells rather than its direct role in inducing apoptotic cell death.

A study on the antitumoral and differentiation effects of peganum harmala derivatives in combination with ATRA on leukaemic cells

Plant derived agents may exert a new approach to the treatment of leukaemia. The present study was an evaluation of proliferation, cytotoxicity and differentiation of harmine and harmaline on HL60 cells, alone or in combination with ATRA and G-CSF. Counting of cells, viability, MTT assay, morphology, NBT reduction and flow cytometry analysis were performed using CD11b and CD 14 monoclonal antibodies. The data showed that harmine and harmaline reduced proliferation in dose and time dependent manner. Optimal antiproliferative concentration of these agents was chosen. However, both agents in higher doses were cytotoxic. Combination of ATRA, G-CSF and each agent alone, particularly harmaline in optimal dose, resulted in partially additive decrease in cell proliferation. Cells treated with both harmaline and ATRA demonstrated some morphological changes and NBT positivity, but the extent of changes observed following treatment with harmaline was less than ATRA. Flow cytometric analysis showed that ATRA induced a neutrophilic differentiation, while harmaline led to a predominantly monocytic differentiation. Combination of harmine and harmaline with ATRA and G-CSF did not change the extent of differentiation, and the cells differentiated into the neutrophilic lineage. This shows that the direction of differentiation is dominantly determined by ATRA. These preliminary data implies a new approach in treatment of leukemia.

Cytokines in the differentiation therapy of leukemia: from laboratory investigations to clinical applications

Differentiation therapy of leukemia is the treatment of leukemia cells with biological or chemical agents that induce the terminal differentiation of the cancer cells. It is regarded as a novel and targeted approach to leukemia treatment, based on our better understanding of the hematopoietic process and the mechanisms of its deregulation during leukemogenesis. Clinically, differentiation therapy has been most successful in acute promyelocytic leukemia using all-trans-retinoic acid as the inducer, either alone or in combination with chemotherapy. This review presents evidence that a number of hematopoietic cytokines play important roles in both normal and aberrant hematopoietic processes. In vitro laboratory investigations in the past two decades using well-characterized myeloid leukemic cell lines and primary blast cells from leukemia patients have revealed that many hematopoietic cytokines can trigger lineage-specific differentiation of leukemia cells, which may have important implications in the clinical setting. Moreover, our current understanding of cytokine interactions and the molecular mechanisms of cytokine-induced leukemic cell differentiation will be discussed in the light of recent findings. Finally, ways in which laboratory research on cytokines in the differentiation therapy of leukemia can lead to the improved design of protocols for future clinical applications to leukemia therapy will also be addressed.

Identification of a molecular signature predictive of sensitivity to differentiation induction in acute myeloid leukemia

Acute myeloid leukemia (AML) blasts are immature committed myeloid cells unable to spontaneously undergo terminal maturation, and characterized by heterogeneous sensitivity to natural differentiation inducers. Here, we show a molecular signature predicting the resistance or sensitivity of six myeloid cell lines to differentiation induced in vitro with retinoic acid or vitamin D. The identified signature was further validated by TaqMan assay for the prediction of response to an in vitro differentiation assay performed on 28 freshly isolated AML blast populations. The TaqMan assay successfully predicts the in vitro resistance or responsiveness of AML blasts to differentiation inducers. Furthermore, performing a meta-analysis of publicly available microarray data sets, we also show the accuracy of our prediction on known phenotypes and suggest that our signature could become useful for the identification of patients eligible for new therapeutic strategies.

Transcriptional and post-transcriptional regulation of glutathione S-transferase P1 expression during butyric acid-induced differentiation of K562 cells

Over-expression of glutathione S-transferase P1 is related to chemotherapeutic drug resistance as well as to differentiation of human erythroleukemia cells. In opposition to previously described differentiating inducers which enhance the GST-resistance phenotype, time- and concentration-dependent activation of both erythroid and megakaryocytic differentiation pathways by butyric acid progressively diminished GSTP1 mRNA expression. GSTP1 mRNA expression decreased by 25% (p<0.01) and 64% (p<0.01) in 1mM and 2mM butyric acid-differentiated K562 cells, respectively. These results were associated to both a reduction of GATA-1 binding activity to the GSTP1 promoter and to a posttranscriptional destabilization of GSTP1 mRNA in a concentration dependent manner. Indeed, GSTP1 mRNA half-life decreased from 43.8 to 36.2 h and 12.6 h in 1mM- and 2mM-treated cells, respectively.

Differentiation of pheochromocytoma PC12 cells induced by human urine extract and the involvement of the extracellular signal-regulated kinase signaling pathway

OBJECTIVE

The aim of this study was to investigate the effects of a human urine preparation on the differentiation of tumor cells.

DESIGN

The pheochromocytoma PC12 cells were used to examine the effects of a human urine preparation, CDA-2 on the induction of differentiation markers, neurofilaments, and compared with that induced by nerve growth factor (NGF). The MAPK/ERK kinase (MEK) inhibitor U0126 was used to examine the involvement of mitogen-activated protein kinase (MAPK) signaling pathway in this differentiation inducing effect.

RESULTS

We find that CDA-2 could induce differentiation of pheochromocytoma PC12 cells, as evidenced by the markedly increased expression of neurofilaments to a level comparable to those induced by NGF. This phenomenon was accompanied by the phosphorylation of extracellular-signal-regulated kinase (ERK) and could be inhibited by the MEK inhibitor, U0126.

CONCLUSIONS

Our results demonstrate the presence of active components in the human urine extract that can induce differentiation of PC12 cells and may involve the ERK signaling pathway. This may provide new insights for seeking novel differentiation agents and offer hope for cancer patients.

Rexinoid-triggered differentiation and tumor-selective apoptosis of acute myeloid leukemia by protein kinase A-mediated desubordination of retinoid X receptor

Apart from PML-retinoic acid receptor-alpha (RARalpha) acute promyelocytic leukemia all other acute myeloid leukemias (AML) are unresponsive to retinoid differentiation therapy. However, elevating the levels of cyclic AMP (cAMP) confers onto retinoid X receptor (RXR)-selective agonists ("rexinoids") the ability to induce terminal granulocyte differentiation and apoptosis of all-trans retinoic acid-resistant and insensitive AML cells and patients' blasts. Protein kinase A activation leads to corepressor release from the RAR subunit of the RAR-RXR heterodimer, resulting in "desubordination" of otherwise silent RXR, which acquires transcriptional competence in response to cognate ligands. Rexinoid-cAMP induction of endogenous RARbeta is blunted in mouse embryo fibroblasts lacking RARs, but reintroduction of exogenous RARalpha reestablishes responsiveness, thus confirming that the RARalpha-RXR heterodimer is the rexinoid mediator. The apoptogenic effect of this treatment involves enhanced expression of the death receptor DR5 and its cognate ligand, tumor necrosis factor-related apoptosis inducing ligand, both of which are known to induce apoptosis in a tumor cell-selective manner and lead to the activation of initiator caspases. Immunohistochemistry confirmed induction of tumor necrosis factor-related apoptosis inducing ligand and DR5 in AML patient blasts cultured ex vivo. AML patients' blasts responded to rexinoid-cAMP combination treatment with induction of maturation and apoptosis, independent of karyotype, immunophenotype, and French-American-British classification status. Clonogenic assays revealed complete inhibition of blast clonogenicity in four out of five tested samples. Our results suggest that despite the genetic, morphologic, and clinical variability of this disease, the combination of rexinoids and cAMP-elevating drugs, such as phosphodiesterase inhibitors, might lead to a novel therapeutic option for AML patients by inducing a tumor-selective death pathway.

Effects of anthracycline derivatives on human leukemia K562 cell growth and differentiation

New derivatives of daunorubicin (DRB), doxorubicin (DOX), and epidoxorubicin (EDOX) with an amidine group bonded to C-3' of daunosamine moiety with either morpholine or hexamethyleneimine ring attached to the amidine group are studied in this paper. We have shown that all of these newly synthesized anthracycline derivatives inhibit human leukemia K562 cell line proliferation but only some of them induce erythroid differentiation when used at subtoxic concentrations. Morpholine derivative of DOX has the greatest potential to inhibit proliferation and to induce differentiation in vitro. The correlation between these two cellular processes was also significant for other tested compounds. In cell cycle analysis, we have demonstrated that those anthracycline derivatives that exert the greatest cytostatic potential caused G(2)/M arrest, which in turn, might contribute to the development of a differentiating phenotype. The concentrations of the compounds used in the study are pharmacologically relevant. These new potent inducers of differentiation might be exploited as anticancer drugs for treatment of leukemia by differentiation therapy.

Gefitinib induces myeloid differentiation of acute myeloid leukemia

Cure rates for patients with acute myeloid leukemia (AML) remain low despite ever-increasing dose intensity of cytotoxic therapy. In an effort to identify novel approaches to AML therapy, we recently reported a new method of chemical screening based on the modulation of a gene expression signature of interest. We applied this approach to the discovery of AML-differentiation-promoting compounds. Among the compounds inducing neutrophilic differentiation was DAPH1 (4,5-dianilinophthalimide), previously reported to inhibit epidermal growth factor receptor (EGFR) kinase activity. Here we report that the Food and Drug Administration (FDA)-approved EGFR inhibitor gefitinib similarly promotes the differentiation of AML cell lines and primary patient-derived AML blasts in vitro. Gefitinib induced differentiation based on morphologic assessment, nitro-blue tetrazolium reduction, cell-surface markers, genome-wide patterns of gene expression, and inhibition of proliferation at clinically achievable doses. Importantly, EGFR expression was not detected in AML cells, indicating that gefitinib functions through a previously unrecognized EGFR-independent mechanism. These studies indicate that clinical trials testing the efficacy of gefitinib in patients with AML are warranted.

12-O-Tetradecanoylphorbol-13-acetate (TPA)-induced dual-specificity phosphatase expression and AML cell survival

12-O-Tetradecanoylphorbol-13-acetate (TPA) is being developed as a therapeutic agent by virtue of its being a potent modulator of signal transduction in pre-clinical models of AML [Strair RK, Schaar D, Goodell L, Aisner J, Chin KV, Eid J, et al. Administration of a phorbol ester to patients with hematological malignancies: preliminary results from a phase I clinical trial of 12-O-tetradecanoylphorbol-13-acetate. Clin Cancer Res 2002;8:2512-8]. In this report, we identify a subset of primary AML samples that undergoes apoptosis after exposure to TPA and demonstrate that TPA-induced cytotoxicity is associated with modulation of the ERK signaling pathway. Analysis of mitogen-activated protein kinase (MAPK) dual-specificity phosphatases (DUSP), as potential regulators of AML cell signaling, indicates that these genes are coordinately regulated and rapidly induced by TPA in primary AML cells. Therefore, TPA-induced primary AML cytotoxicity is associated with modulation of ERK signaling which may be partially mediated by regulation of phosphatase expression.

WEB-2086 and WEB-2170 trigger apoptosis in both ATRA-sensitive and -resistant promyelocytic leukemia cells and greatly enhance ATRA differentiation potential

PAF-receptor antagonists WEB-2086 and WEB-2170 (WEBs) have been previously shown to induce differentiation in murine and human leukemia cells. The present study describes the apoptotic-differentiative effect of WEBs in all-trans-retinoic acid (ATRA)-sensitive (NB4) and -resistant (NB4-007-6 and NB4-MR4) acute promyelocytic leukemia (APL) cell lines as well as blasts from patients with t(15;17) APL. NB4 cells exposed to 0.5-1 mM WEBs underwent striking growth arrest and massive apoptosis without appreciable differentiation; IC50 values after 3-day treatment of NB4 were 0.4 and 0.25 mM for WEB-2086 and WEB-2170, respectively. WEBs induced apoptosis also in the two ATRA-resistant NB4-007-6 and NB4-MR4 cell lines and in blasts from patients with t(15;17) APL. Moreover, subapoptotic WEBs acted synergistically with low-dose (0.025-0.05 microM) ATRA; this allowed to increase ATRA differentiation potential up to 40-fold and to improve both number and intensity of NBT-positive NB4 cells at definitely higher levels than with 1 muM ATRA alone. The powerful antiproliferative-apoptotic activities of WEBs in vitro on ATRA-sensitive, ATRA-resistant APL cells and blasts from patients with APL as well as drug capabilities to enhance ATRA differentiation potential suggested that these agents also due to their recognized tolerability in vivo might improve, alone or in combination, clinical treatment of APL.

The effect of anti-CD44 monoclonal antibodies on differentiation and proliferation of human acute myeloid leukemia cells

Acute myeloid leukemia (AML) is a clonal malignant disease characterized by an increasing number of immature myeloid cells arrested at various stages of granulocytic and monocytic differentiation. The stage of the blockage defines distinct AML subtypes (AML1 to AML5 are the most frequent ones). There is increasing evidence that the malignant clone is maintained by rare AML stem cells endowed with self-renewal capacity, which through extensive proliferation coupled to partial differentiation, generate leukemic progenitors and blasts, of which the vast majority have limited proliferative capacity. Contrarily to chemotherapy alone, which is still unable to cure most AML patients, the differentiation therapy, which consists in releasing the differentiation blockage of leukemic blasts, has succeeded, when it is combined with chemotherapy, to greatly improve the survival of AML3 patients, using retinoic acid as differentiating agent. However, this molecule is ineffective in other AML subtypes, which are the most frequent. We have shown that specific monoclonal antibodies (mAbs, H90 and A3D8) directed to the CD44 cell surface antigen, that is strongly expressed on human AML blasts, are capable of triggering terminal differentiation of leukemic blasts in AML1 to AML5 subtypes. These results have raised the perspective of developing a CD44-targeted differentiation therapy in most AML cases. Interestingly, these anti-CD44 mAbs can also induce the differentiation of AML cell lines, inhibit their proliferation and, in some cases, induce their apoptotic death. These results suggest that H90 and/or A3D8 mAbs may be capable to inhibit the proliferation of leukemic progenitors, to promote the differentiation of the leukemic stem cells at the expense of their self-renewal, and, perhaps, to induce their apoptotic death, thereby contributing to decrease the size of the leukemic clone. The challenges of an anti-CD44 based differentiation therapy in AML, and its importance in relation to the new other therapies developed in this malignancy, are discussed in this review.

Differentiation of human melanoma cells induced by cyanidin-3-O-beta-glucopyranoside

Great attention has been recently given to a flavonoid of the anthocyanin class, cyanidin-3-O-beta-glucopyranoside (C-3-G), which is widely spread throughout the plant kingdom, and is present in both fruits and vegetables of human diets. In this study, we investigated the effect of C-3-G on proliferation and differentiation of human melanoma cells. Both morphological and functional parameters were evaluated, using electron and confocal microscopy, cytofluorometric analysis, HPLC assay, Western blot analysis, and enzymatic assay, as appropriate. A treatment with a single dose of C-3-G decreased cell proliferation without affecting cell viability and without inducing apoptosis or necrosis. The mitotic index and cell percentage in S phase were significantly lower in C-3-G treated cells compared with untreated control. C-3-G treatment induced, in a dose- and time-dependent manner, melanoma cell differentiation characterized by a strong increase in dendrite outgrowth accompanied with a remodeling of the microtubular network, a dramatic increase of focal adhesion and an increased expression of "brain specific" cytoskeletal components such as NF-160 and NF-200 neurofilament proteins. C-3-G treatment also induced increase of cAMP levels and up-regulation of tyrosinase expression and activity resulting in an enhanced melanin synthesis and melanosome maturation. Up-regulation of the melanoma differentiation antigen Melan-A/MART-1 in treated cells respect to the untreated control was also recorded. Data obtained provide evidence that a single treatment with C-3-G is able to revert the human melanoma cells from the proliferating to the differentiated state. We conclude that C-3-G is a very promising molecule to include in the strategies for treatment of melanoma; also because of its nutritional relevance.

Induction of a senescent-like phenotype does not confer the ability of bovine immortal cells to support the development of nuclear transfer embryos

Previously, we reported that cloned embryos derived from an immortalized bovine mammary epithelial cell line (MECL) failed to develop beyond 12- to 16-cell stage. To analyze whether induction of a senescent-like phenotype in MECL can improve their ability to support the development after transfer into enucleated oocytes, we treated MECL with DNA methylation inhibitor 5-aza-2-deoxycytidine (Aza-C), histone deacetylase inhibitors trichostatin A (TSA), sodium butyrate (NaBu), or 5-bromodeoxyuridine and used those cells for nuclear transfer. Primary bovine fetal fibroblasts (BFF) were used as control. All agents were capable to induce features of senescence including reduced cell proliferation, enlarged cell size with a considerable proportion of cells stained positive for acidic senescence-associated beta-galactosidase and G1/S cell cycle boundary arrest in MECL. Aza-C treatment induced genome demethylation. Acetylation of H3 and H4 was increased after TSA treatment in both MECL and BFF, whereas no obvious changes in global H3 or H4 acetylation were detected after NaBu treatment. Nuclear transfer experiments following diverse treatments demonstrated that the induced senescent-like phenotype of MECL did not confer their ability to support embryonic development, although 7.3% of reconstructed embryos derived from NaBu-treated cells developed to morula stage. Intriguingly, a much higher proportion of cloned embryos developed to blastocysts when using NaBu-treated BFF, compared with using untreated BFF (59% versus 26%). Our results suggest that the developmental failure of donor nuclei from bovine immortal cells could not be reversed by induction of senescent-like phenotype. The beneficial effect of NaBu on the developmental potential of cloned embryos reconstructed from BFF merits further studies.

Downregulation of c-Jun expression and cell cycle regulatory molecules in acute myeloid leukemia cells upon CD44 ligation

In the present study, we investigated the mechanism of CD44 ligation with the anti-CD44 monoclonal antibody A3D8 to inhibit the proliferation of human acute myeloid leukemia (AML) cells. The effects of A3D8 on myeloid cells were associated with specific disruption of cell cycle events and induction of G0/G1 arrest. Induction of G0/G1 arrest was accompanied by an increase in the expression of p21, attenuation of pRb phosphorylation and associated with decreased Cdk2 and Cdk4 kinase activities. Since c-Jun is an important regulator of proliferation and cell cycle progression, we analysed its role in A3D8-mediated growth arrest. We observed that A3D8 treatment of AML patient blasts and HL60/U937 cells led to the downregulation of c-Jun expression at mRNA and protein level. Transient transfection studies showed the inhibition of c-jun promoter activity by A3D8, involving both AP-1 sites. Furthermore, A3D8 treatment caused a decrease in JNK protein expression and a decrease in the level of phosphorylated c-Jun. Ectopic overexpression of c-Jun in HL60 cells was able to induce proliferation and prevent the antiproliferative effects of A3D8. In summary, these data identify an important functional role of c-Jun in the induction of cell cycle arrest and proliferation arrest of myeloid leukemia cells because of the ligation of the cell surface adhesion receptor CD44 by anti-CD44 antibody. Moreover, targeting of G1 regulatory proteins and the resulting induction of G1 arrest by A3D8 may provide new insights into antiproliferative and differentiation therapy of AML.

Chemoprevention of mammary carcinogenesis by 1alpha-hydroxyvitamin D5, a synthetic analog of Vitamin D

Numerous analogs of Vitamin D have been synthesized in recent years with the hope of generating a compound that retains the anticarcinogenic activity of Vitamin D without causing any toxicity. We synthesized such an analog, 1alpha-hydroxy-24-ethylcholecalciferol [1alpha-hydroxyvitamin D(5) or 1alpha(OH)D(5)], and showed that it was tolerated by rats and mice at a much higher dose than 1alpha,25 dihydroxy cholecalciferol [1alpha,25(OH)(2)D(3)]. This property makes it a prime candidate for chemoprevention studies. In the mouse mammary gland organ culture (MMOC), 1alpha(OH)D(5) inhibited carcinogen-induced development of both mammary alveolar and ductal lesions. In vivo carcinogenesis study showed statistically significant reduction of tumor incidence and multiplicity in N-methyl-N-nitrosourea (MNU)-treated rats that were fed 25-50 microg 1alpha(OH)D(5)/kg diet. There were no adverse effects on plasma calcium concentrations. In order to determine if the effect of 1alpha(OH)D(5) would be selective in suppressing proliferation of transformed cells, its effects on cell growth and proliferation were compared between BT474 (cancer) and MCF12F (non-tumorigenic) human breast epithelial cells. Results showed that 1alpha(OH)D(5) induced apoptosis and cell cycle G1 phase arrest in BT474 breast cancer cells without having any effects on proliferation of the MCF12F cells. In addition, in MMOC it had no growth inhibitory effects on normal epithelial cell proliferation in the absence of carcinogen. Similarly, non-tumorigenic human breast epithelial cells in explant culture did not respond to 1alpha(OH)D(5), whereas treatment with 1alpha(OH)D(5) induced cell death in the explants of cancer tissue. These results collectively indicate that 1alpha(OH)D(5) selectively induced apoptosis only in transformed cells but not in normal breast epithelial cells. Interestingly, the growth inhibitory effects of 1alpha(OH)D(5) were observed in Vitamin D receptor positive (VDR(+)) breast cancer cells, but not in highly metastatic VDR(-) breast cancer cells, such as MDA-MB-435 and MDA-MB-231, suggesting that 1alpha(OH)D(5) action may be mediated, in part, by VDR.

Emerging cancer-targeted therapies

There is reason to believe that the unfolding revolution in molecular biology and translational research will allow selective targeting of tumor cells, and radically change the way general practitioners and pediatric oncologists treat and follow children with cancer. This article highlights some of the most promising approaches being tested in the field. By learning about the underlying biology, the remaining hurdles, the projected timeline, and the possible impact of new therapies on the practice of pediatric oncology, health care professionals and patients should be better prepared for the future of pediatric oncology.

Butyric acid increases invasiveness of HL-60 leukemia cells: role of reactive oxygen species

Butyric acid (BA) induces differentiation of human leukemia, including HL-60 cells. By using a fluorescent probe, we showed that reactive oxygen species (ROS) were generated in BA-treated cells. BA-induced differentiation was accompanied with an increased secretion of pro-matrix metalloproteinase (MMP)-9. Both phenomena were inhibited by antioxidants. Tissue inhibitors of MMP (TIMP)-1 and -2 secretion were increased by BA, but differently affected by antioxidants. By contrast, BA did not affect MMP-9 mRNA, and decreased TIMP-1 and TIMP-2 mRNA levels. In addition, migratory and invasive properties of HL-60 cells were enhanced by BA, but differently affected by antioxidants. Altogether, these results indicate that ROS are messengers of BA-induced differentiation and increased invasiveness.

Vitamin D and cancer

Vitamin D, a steroid hormone and exerts its biological effects through its active metabolite 1alpha, 25 dihydroxyvitamin D3 [1,25(OH)2D3]. Like steroid hormones, 1,25(OH)2D3 is efficacious at very low concentrations and serves as a ligand for vitamin D receptors (VDR), associating with VDR very high affinity. Despite its potent property as a differentiating agent, its use in the clinical practice is hampered by the induction of hypercalcemia at a concentration required to suppress cancer cell proliferation. Therefore nearly 400 structural analogs of vitamin D3 have been synthesized and evaluated for their efficacy and toxicity. Among these analogs, relatively less toxic but highly efficacious analogs, EB1089, RO24-5531, 1alpha-hydroxyvitamin D5 and a few others have been evaluated in a preclinical toxicity and in Phase I clinical trials for dose tolerance in advanced cancer patients. Clinical trials using vitamin D analogs for prevention or therapy of cancer patients are still in their infancy. Vitamin D mediates its action by two independent pathways. Genomic pathway involves nuclear VDR and induces biological effects by interactions with hormone response elements and modulation of differential gene expressions. Evidence also suggests that vitamin D analogs also interact with steroid hormone(s) inducible genes. The non-genomic pathway is characterized by rapid actions of vitamin D. It involves interactions with membrane-VDR interactions and its interactions with protein kinase C and by altering intracellular calcium channels. Thus, the development of nontoxic analogs of vitamin D analogs and understanding of their molecular mechanism(s) of action are of significant importance in the prevention and treatment of cancer by vitamin D.

Differential effects of histone deacetylase inhibitors on interleukin-18 gene expression in myeloid cells

Histone deacetyrase (HDAC) inhibitors induce growth arrest and differentiation of leukemia cell lines and tumor cells derived from a large variety of human tissues. Here we showed that HDAC inhibitors sodium butyrate, TSA, and valproate regulated the expression of Interleukin-18 (IL-18), a cytokine with antitumor and proinflammatory properties, in human acute myeloid leukemia cell lines U937 and HEL. Sodium butyrate increased expression of IL-18 protein and mRNA and activated 1357bp IL-18 gene promoter construct. IL-18 mRNA level was up-regulated by TSA or valproate, which also activated IL-18 full-length promoter. While sodium butyrate or TSA stimulated the 108-bp IL-18 minimal promoter, valproate failed to activate it, indicating that valproate may use a distinct mechanism from sodium butyrate and TSA to activate IL-18 gene expression.

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.