Epigenetic silencing of miRNA-9 is associated with HES1 oncogenic activity and poor prognosis of medulloblastoma.

BACKGROUND: microRNA-9 is a key regulator of neuronal development aberrantly expressed in brain malignancies, including medulloblastoma. The mechanisms by which microRNA-9 contributes to medulloblastoma pathogenesis remain unclear, and factors that regulate this process have not been delineated. METHODS: Expression and methylation status of microRNA-9 in medulloblastoma cell lines and primary samples were analysed. The association of microRNA-9 expression with medulloblastoma patients' clinical outcome was assessed, and the impact of microRNA-9 restoration was functionally validated in medulloblastoma cells. RESULTS: microRNA-9 expression is repressed in a large subset of MB samples compared with normal fetal cerebellum. Low microRNA-9 expression correlates significantly with the diagnosis of unfavourable histopathological variants and with poor clinical outcome. microRNA-9 silencing occurs via cancer-specific CpG island hypermethylation. HES1 was identified as a direct target of microRNA-9 in medulloblastoma, and restoration of microRNA-9 was shown to trigger cell cycle arrest, to inhibit clonal growth and to promote medulloblastoma cell differentiation. CONCLUSIONS: microRNA-9 is a methylation-silenced tumour suppressor that could be a potential candidate predictive marker for poor prognosis of medulloblastoma. Loss of microRNA-9 may confer a proliferative advantage to tumour cells, and it could possibly contribute to disease pathogenesis. Thus, re-expression of microRNA-9 may constitute a novel epigenetic regulation strategy against medulloblastoma.

Mismatch repair deficiency: a temozolomide resistance factor in medulloblastoma cell lines that is uncommon in primary medulloblastoma tumours.

BACKGROUND: Tumours are responsive to temozolomide (TMZ) if they are deficient in O(6)-methylguanine-DNA methyltransferase (MGMT), and mismatch repair (MMR) proficient. METHODS: The effect of TMZ on medulloblastoma (MB) cell killing was analysed with clonogenic survival assays. Expression of DNA repair genes and enzymes was investigated using microarrays, western blot, and immunohistochemistry. DNA sequencing and promoter methylation analysis were employed to investigate the cause of loss of the expression of MMR gene MLH1. RESULTS: Temozolomide exhibited potent cytotoxic activity in D425Med (MGMT deficient, MLH1 proficient; IC(50)=1.7 µM), moderate activity against D341Med (MGMT proficient, MLH1 deficient), and DAOY MB cells (MGMT proficient, MLH1 proficient). MGMT inhibitor O(6)-benzylguanine sensitised DAOY, but not D341Med cells to TMZ. Of 12 MB cell lines, D341Med, D283Med, and 1580WÜ cells exhibited MMR deficiency due to MLH1 promoter hypermethylation. DNA sequencing of these cells provided no evidence for somatic genetic alterations in MLH1. Expression analyses of MMR and MGMT in MB revealed that all patient specimens (n=74; expression array, n=61; immunostaining, n=13) are most likely MMR proficient, whereas some tumours had low MGMT expression levels (according to expression array) or were totally MGMT deficient (3 out of 13 according to immunohistochemistry). CONCLUSION: A subset of MB may respond to TMZ as some patient specimens are MGMT deficient, and tumours appear to be MMR proficient.

Interferon-gamma mediated up-regulation of caspase-8 sensitizes medulloblastoma cells to radio- and chemotherapy.

Loss of caspase-8 expression - which has been demonstrated in a subset of Medulloblastoma (MB) - might block important apoptotic signalling pathways and therefore contribute to treatment resistance. In this study, IFN-gamma mediated up-regulation of caspase-8 in human MB cells was found to result in chemosensitization to cisplatin, doxorubicin and etoposide, and sensitisation to radiation. These effects were more prominent in D425 and D341 MB cells (low basal caspase-8 expression) when compared to DAOY MB cells (high basal caspase-8 expression). IFN-gamma mediated chemosensitization and radiosensitization effects were reduced by treatment with the caspase-8 specific inhibitor z-IETD-fmk. Treatment of IFN-gamma resulted in activation of STAT1 in DAOY MB cells and to a lesser extent in D425, but not in D341, indicating that IFN-gamma acts in MB cells through STAT1-dependent and -independent signalling pathways. Taken together, our results demonstrate that IFN-gamma mediated restoration of caspase-8 in MB cells might enhance apoptotic pathways relevant to the response to chemo- and radiotherapy.

Antisense treatment of IGF-IR induces apoptosis and enhances chemosensitivity in central nervous system atypical teratoid/rhabdoid tumours cells.

Central nervous system (CNS) atypical teratoid/rhabdoid tumours (AT/RT) are among the paediatric malignant tumours with the worst prognosis and fatal outcome. Insulin-like growth factor I receptor (IGF-IR) protects cancer cells from apoptosis induced by a variety of anticancer drugs and radiation. In the present study, IGF-IR was expressed in 8/8 primary AT/RT as detected by immunohistochemistry. Moreover, we found IGF-I and IGF-II mRNA in BT-16 CNS AT/RT cells and IGF-II mRNA in BT-12 CNS AT/RT cells, and autophosphorylated IGF-IR in both cell lines, indicating the potential presence of an autocrine/paracrine IGF-I/II/IGF-IR loop in CNS AT/RT. IGF-IR antisense oligonucleotide treatment of human CNS AT/RT cells resulted in significant down-regulation of IGF-IR mRNA and protein expression, induction of apoptosis, and chemosensitisation to doxorubicin and cisplatin. These studies provide evidence for the influence of IGF-IR on cellular responses to chemotherapy and raise the possibility that curability of selected CNS AT/RT may be improved by pharmaceutical strategies directed towards the IGF-IR.

Paediatric medulloblastoma cells are susceptible to Viscum album (Mistletoe) preparations.

BACKGROUND: Medulloblastoma constitute more than 20% of all paediatric brain tumours and are the most common malignant brain tumours in children. Adjuvant chemotherapy has seen a strong increase in the use of complementary medicine for cancer treatment. Evidence for cytotoxic and apoptotic effects of Viscum album (Mistletoe) in vitro is available, however, no data concerning paediatric tumours, especially paediatric brain tumours, has been provided so far. MATERIALS AND METHODS: In order to compare the receptiveness of medulloblastoma cells to different Viscum album preparations, in vitro cytotoxic effects of eight Viscum album extracts on four different paediatric medulloblastoma cell lines were analysed by MTT-Tests. Lectin contents of the extracts were determined to correlate them with the mitochondrial activity of mistletoe-treated cells. Flowcytometric analyses with Annexin V-FITC staining were carried out to quantify the amount of apoptotic cells compared to necrotic and viable cells. RESULTS: Data obtained with the medulloblastoma cell lines, Daoy, D342, D425 and UW-288-2, treated with Viscum album preparations from eight dissimilar host trees (Iscucin Abietis, Pini, Populi, Mali, Salicis, Crataegi, Quercus and Tiliae), indicated a significant growth-inhibition of all cell lines, yet the cell susceptibility was dissimilar against the different extracts. The decrease in mitochondrial activity and increase in apoptosis correlated with the lectin content of the used preparation in a dose-dependent manner. CONCLUSION: These in vitro results show that paediatric medulloblastoma cells respond to Viscum album preparations, by undergoing cell death through apoptosis and that this growth-inhibition correlates with the lectin content of the used preparation.

Resistance to tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-induced apoptosis in neuroblastoma cells correlates with a loss of caspase-8 expression.

Disruption of apoptotic pathways may be involved in tumor formation, regression, and treatment resistance of neuroblastoma (NB). Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a potent inducer of apoptosis in cancer cell lines, whereas normal cells are not sensitive to TRAIL-mediated apoptosis. In this study we analyzed the expression and function of TRAIL and its agonistic and antagonistic receptors as well as expression of cellular FLICE-like inhibitory protein and caspase-2, -3, -8, -9, and -10 in 18 NB cell lines. Semiquantitative RT-PCR revealed that TRAIL-R2 and TRAIL-R3 are the main TRAIL-receptors used by NB cells. Sensitivity to TRAIL-induced apoptosis did not correlate with mRNA expression of TRAIL receptors or cellular FLICE-like inhibitory protein. Surprisingly, caspase-8 and caspase-10 mRNA expression was detected in only 5 of 18 NB cell lines. Interestingly, only these five NB cell lines were susceptible to TRAIL-induced apoptosis in a time- and dose-dependent manner. Treatment with 5-aza-2'-deoxycytidine restored mRNA and protein expression of caspase-8 and TRAIL sensitivity of resistant cell lines, suggesting that gene methylation is involved in caspase inactivation. The TRAIL system seems to be functional in NB cells expressing caspase-8 and/or caspase-10. Because many cytotoxic drugs induce caspase-dependent apoptosis, failure to express caspase-8 and/or caspase-10 might be an important mechanism of resistance to chemotherapy in NB.

Resistance to TRAIL-induced apoptosis in primitive neuroectodermal brain tumor cells correlates with a loss of caspase-8 expression.

TNF-related apoptosis-inducing ligand (TRAIL) is a potent inducer of apoptosis in adult malignant glioma and various other human solid tumor models but not in normal tissues. To characterize the TRAIL death pathway in childhood primitive neuroectodermal brain tumor (PNET), 8 human PNET cell lines were tested for TRAIL-induced apoptosis. TRAIL-sensitivity of the PNET cell lines was correlated with mRNA expression levels of TRAIL, its agonistic (TRAIL-R1, TRAIL-R2) and antagonistic (TRAIL-R3, TRAIL-R4) receptors, cellular FLICE-like inhibitory protein (cFLIP), caspase-3 and caspase-8. Three of 8 PNET cell lines tested were susceptible to TRAIL-induced apoptosis. Sensitivity to TRAIL-induced apoptosis did not correlate with mRNA expression of TRAIL receptors or cFLIP. However, all TRAIL-sensitive PNET cell lines expressed caspase-8 mRNA and protein, while none of the five TRAIL-resistant PNET cell lines expressed caspase-8 protein. Treatment with the methyltransferase inhibitor 5-aza-2'-deoxycytidine restored mRNA expression of caspase-8 and TRAIL-sensitivity in formerly TRAIL-resistant PNET cells, suggesting that gene methylation inhibits caspase-8 transcription in these cells. We conclude, that loss of caspase-8 mRNA is an important mechanism of TRAIL-resistance in PNET cells. Treatment with recombinant soluble TRAIL, possibly in combination with methyltransferase inhibitors, represents a promising therapeutic approach for PNET that deserves further investigation.

Expression of the neurotrophin receptor TrkB is associated with unfavorable outcome in Wilms' tumor.

PURPOSE: Neurotrophins and their receptors regulate the proliferation, differentiation, and death of neuronal cells, and they have been implicated in the pathogenesis and prognosis of neuroblastomas and medulloblastomas. Tyrosine kinase (Trk) receptors also are expressed in extraneural tissues. PATIENTS AND METHODS: To study the role of neurotrophin receptors and ligands in Wilms' tumor (WT), we determined their expression by semiquantitative duplex reverse transcriptase polymerase chain reaction in 39 patients with primary WT. Comparison of mRNA expression levels with clinical variables was performed by use of Cox regression analysis. RESULTS: Children with WT that expressed high levels of full-length TrkB mRNA (TrkBfull) had a significantly greater risk of death than children whose tumors had little or no TrkBfull expression (hazard ratio, 9.7; P =.02). The 5-year relapse-free survival was 100% versus 65% for patients with low versus high tumor expression of TrkBfull (P <.003). Conversely, children with tumors that expressed high mRNA levels of a functionally inactive truncated TrkB receptor (TrkBtrunc) had a greater chance of survival than children with low levels of TrkBtrunc (hazard ratio, 0.08; P =.005). The 5-year relapse-free survival was 95% versus 68% for patients with high versus low levels of TrkBtrunc (P =.01). The hazard ratios for TrkBfull and TrkBtrunc remained significant after they were adjusted for tumor stage (P =.01 and P =.017, respectively). All WTs with high levels of TrkB expression also expressed the brain-derived nerve growth factor ligand. CONCLUSION: Expression of TrkBfull in WT is associated with worse outcome, perhaps because it provides an autocrine survival pathway. Conversely, TrkBtrunc expression is associated with excellent outcome, perhaps as a result of a dominant negative effect.

TrkC expression predicts good clinical outcome in primitive neuroectodermal brain tumors.

PURPOSE: To identify biologic prognostic factors in childhood primitive neuroectodermal tumors (PNET), including medulloblastoma, that accurately define patient groups with sufficiently good prognosis to permit a reduction in treatment intensity. PATIENTS AND METHODS: We determined expression levels of the neurotrophin receptor TrkC mRNA in formalin-fixed tumor samples from 87 well characterized PNET patients using in situ hybridization. Comparison of TrkC mRNA expression levels with clinical and other laboratory variables was performed using univariate and multivariate Cox regression analysis. RESULTS: High TrkC mRNA expression was found to be associated more with higher 5-year cumulative survival rate than was low TrkC mRNA expression (89% v 46%, respectively). When compared with established clinical prognostic factors and laboratory variables of potential prognostic significance, TrkC mRNA expression, by univariate analysis, was found to be the single most powerful predictor of outcome (hazards ratio, 4.81; P <.00005), exceeding all clinical prognostic factors. In multivariate analysis, the hazards ratio remained significant (P <.00005). CONCLUSION: High TrkC mRNA expression in PNET is a powerful independent predictor of favorable clinical outcome. Assessment of TrkC mRNA levels may aid in treatment planning for patients with PNETs and should be incorporated prospectively into PNET clinical trials.

Telomerase inhibition, telomere shortening, cell growth suppression and induction of apoptosis by telomestatin in childhood neuroblastoma cells.

Neuroblastoma is a tumour derived from primitive cells of the sympathetic nervous system and is the most common extracranial solid tumour in childhood. Unfavourable tumours are characterised not only by structural changes, including 1p deletion and amplification of the MYCN proto-oncogene, but also by high telomerase activity. Telomeric G-rich single-stranded DNA can adopt in vitro an intramolecular quadruplex structure, which has been shown to inhibit telomerase activity. In this study, we examined telomestatin, a G-quadruplex interactive agent, for its ability to inhibit telomere maintenance of neuroblastoma cells. Telomere length was determined by the terminal restriction fragment method, telomerase activity was measured by a quantitative telomeric repeat amplification protocol, and the expression of human telomerase by quantitative real-time polymerase chain reaction (RT-PCR). Short-term treatment with telomestatin resulted in dose-dependent cytotoxicity and induction of apoptosis. Long-term treatment with telomestatin at non-cytotoxic, but still telomerase activity-inhibiting, concentrations resulted in telomere shortening, growth arrest and induction of apoptosis. These results suggest that the effect of telomestatin is dose-dependent and at least 2-fold. Prolonged low-dose treatment with telomestatin limits the cellular lifespan of NB cells through disruption of telomere maintenance.

MYC messenger RNA expression predicts survival outcome in childhood primitive neuroectodermal tumor/medulloblastoma.

PURPOSE AND EXPERIMENTAL DESIGN: Cerebellar primitive neuroectodermal tumors/medulloblastomas (PNET/MB) are the most common malignant brain tumors in childhood. To identify PNET/MB biological prognostic factors that define a patient group with a sufficiently good prognosis to permit a reduction in treatment intensity, we determined the expression levels of MYC mRNA in fresh frozen tumor samples from 26 PNET/MB patients using semiquantitative reverse transcription-PCR. RESULTS: MYC mRNA expression levels in primary PNET/MB showed a wide range with a 22-fold difference between the highest and lowest values and did not correlate with MYC gene amplification. MYC mRNA expression was an independent significant prognostic factor for progression-free survival outcome and was more predictive than standard clinical factors. The combination of low MYC mRNA expression and high TrkC mRNA expression identified a good outcome group of PNET/MB patients (n = 7) with 100% progression-free survival after a median follow-up time of 55 months (range, 15-91 months). Three of these seven good outcome patients survived without radiotherapy. CONCLUSIONS: Low MYC mRNA expression is a powerful independent predictor of favorable clinical outcome in PNET/MB. Assessment of MYC mRNA levels is feasible and may be incorporated in prospective PNET/MB clinical trials to aid in treatment planning for patients with PNET/MB on confirmation of our results in larger studies.

Microbeam radiation therapy: Clinical perspectives.

Microbeam radiation therapy (MRT), a novel form of spatially fractionated radiotherapy (RT), uses arrays of synchrotron-generated X-ray microbeams (MB). MRT has been identified as a promising treatment concept that might be applied to patients with malignant central nervous system (CNS) tumours for whom, at the current stage of development, no satisfactory therapy is available yet. Preclinical experimental studies have shown that the CNS of healthy rodents and piglets can tolerate much higher radiation doses delivered by spatially separated MBs than those delivered by a single, uninterrupted, macroscopically wide beam. High-dose, high-precision radiotherapies such as MRT with reduced probabilities of normal tissue complications offer prospects of improved therapeutic ratios, as extensively demonstrated by results of experiments published by many international groups in the last two decades. The significance of developing MRT as a new RT approach cannot be understated. Up to 50% of cancer patients receive conventional RT, and any new treatment that provides better tumour control whilst preserving healthy tissue is likely to significantly improve patient outcomes.

Port-A-Cath infections in children with cancer.

Implanted subcutaneous (s.c.) central venous port accesses including Port-A-Cath (PAC) facilitate the administration of chemotherapy or blood products and are frequently used in children with cancer. The incidence of PAC-related infections was determined in 155 consecutive paediatric cancer patients with PAC followed for a total of 134,773 days (median, 738; range, 25-2080). Overall, 48 bloodstream infections occurred in 26 patients. 12 (25%) of these infections and 3 local infections at the insertion site were treatment-resistant and demanded removal of the PAC. Coagulase-negative staphylococci were involved in 12 of these 15 episodes. The rate of clearly PAC-related infections in this so far largest reported series was 0.11 episodes per 1000 PAC days, one of the lowest in the literature. Although catheter-related infections demanded PAC removal in 8% of our patients, the long periods PAC were in use and their benefits argue for continued PAC use in the paediatric cancer population.

Expression of Apo-3 and Apo-3L in primitive neuroectodermal tumours of the central and peripheral nervous system.

Deregulation of apoptosis has been implicated in the pathogenesis, spontaneous regression and treatment resistance of neuroblastoma. A newly recognised member of the tumour necrosis factor (TNF)-family of death receptors known as Apo-3 has been mapped to human chromosome 1p36.3, a region commonly deleted in aggressive neuroblastoma. Based on its localisation and function, Apo-3 is a candidate for the putative neuroblastoma tumour suppressor gene. Therefore we analysed mRNA expression of the Apo-3 receptor/ligand (Apo-3/Apo-3L) system in a representative panel of 18 neuroblastoma cell lines, 41 primary neuroblastoma and 13 ganglioneuromas/ganglioneuroblastomas by semi-quantitative RT-PCR. We compared the level of expression with the well-established prognostic factors age, stage, histology, MYCN-amplification and TrkA expression, as well as outcome. For comparison, we studied Apo-3/Apo-3L expression in 27 central nervous system (CNS) primitive neuroectodermal tumours/medulloblastomas (PNET/medulloblastoma) and in six normal brain samples. Neuroblastoma cell lines with 1p deletion and MYCN-amplification expressed significantly lower levels of Apo-3 (P=0.009 and P=0.03, respectively) compared with neuroblastoma cell lines without 1p deletion or MYCN-amplification. The mean expression level of Apo-3L was significantly higher in ganglioneuromas/ganglioneuroblastomas compared with neuroblastomas (P=0.001) and in normal brain compared with PNET/medulloblastoma (P<0.0001). Expression of Apo-3L was significantly associated with survival in neuroblastomas (P<0.049) and in PNET/medulloblastomas (P=0.01). Expression of Apo-3 was significantly associated with survival in PNET/medulloblastomas (P=0.03). Thus, the Apo-3 receptor/ligand system might be involved in the regulation of apoptosis in neuroblastomas and PNET.

Loss of caspase-8 mRNA expression is common in childhood primitive neuroectodermal brain tumour/medulloblastoma.

Upon binding of tumour necrosis factor (TNF)-related apoptosis inducing ligand (TRAIL), the agonistic TRAIL receptors DR4 and DR5 activate caspase-8 leading to apoptosis. In primitive neuroectodermal brain tumour (PNET) cell lines, TRAIL-induced apoptosis was recently shown to correlate with caspase-8 mRNA expression (Grotzer MA, Eggert A, Zuzak TJ, et al. Oncogene 2000, 19, 4604-4610). In this study, we analysed the expression of the TRAIL death pathway in 27 primary PNET/medulloblastoma. As shown by semiquantitative reverse transcriptase-polymerase chain reaction (RT-PCR), all PNET/medulloblastoma evaluated expressed DR5, the adapter protein FADD and caspase-3, but only 48% expressed caspase-8. The mRNA expression of caspase-8 was significantly lower in primary PNET/medulloblastoma compared with normal brain samples. PCR revealed >75% methylation of the caspase-8 promoter region in three of seven PNET cell lines and in 55% of the primary PNET/medulloblastoma evaluated. In the PNET cell lines, the methylation status correlated with the caspase-8 mRNA expression. We conclude that loss of caspase-8 gene expression is common in PNET/medulloblastoma suggesting that suppression of death receptor induced apoptosis may play an important role in the pathogenesis of this common childhood brain tumour.

Angiogenic profile of childhood primitive neuroectodermal brain tumours/medulloblastomas.

Primitive neuroectodermal brain tumours (PNET) including medulloblastomas (PNET/MB) are the most common malignant brain tumours of childhood. Similar to many other brain tumours, PNET/MB often show marked neovascularisation. To determine which angiogenic factors contribute to PNET/MB angiogenesis, we examined the expression of eight angiogenic factors (vascular endothelial growth factors (VEGF, VEGF-B, VEGF-C), basic fibroblast growth factor (bFGF), angiopoetins (Ang-1, Ang-2), transforming growth factor (TGF-alpha), and platelet-derived endothelial growth factor (PDGF-A)) by semi-quantitative reverse transcriptase polymerase chain reaction (RT-PCR) in six PNET cell lines and 28 primary PNET/MB. Expression levels of angiogenic factors were compared with microvessel density, TrkC mRNA expression, clinical variables and survival outcomes. Our results indicate that all PNET/MB tested produce a wide range of angiogenic factors that are, individually or together, likely to play a direct role in PNET/MB tumour growth. This suggests that anti-angiogenesis approaches targeting VEGF alone may be insufficient in PNET/MB.

Autocrine secreted insulin-like growth factor-I stimulates MAP kinase-dependent mitogenic effects in human primitive neuroectodermal tumor/medulloblastoma.

Primitive neuroectodermal tumors/medulloblastoma (PNET/MB) have similarities to neuroectodermal progenitor cells of the developing CNS. Since insulin-like growth factor I (IGF-I) exerts pleiotrophic effects on cells in the developing CNS, we evaluated the production, mitogenic effects and signaling pathways of IGF-I in PNET/MB cells and found that IGF-I is an autocrine growth factor in human PNET/MB cell lines tested. Stimulation of DAOY cells by IGF-I led to phosphorylation of its cognate receptor (IGF-IR) and resulted in cell proliferation. These effects of IGF-I were suppressed by IGF-IR blocking antibodies and by PD 98059, MAP kinase pathway inhibitor. The results demonstrate the existence of an autocrine IGF-I/IGF-IR loop and indicate that IGF-I promotes proliferation via MAP kinase pathway.

The investigation of karyotypic instability in the high-hyperdiploidy subgroup of acute lymphoblastic leukemia.

Acute lymphoblastic leukemia (ALL) of childhood has been cytogenetically well characterized, and approximately 25% of cases will have a high-hyperdiploid (51-68) chromosome complement. In a 5 year period a consecutive series of 152 presentation ALL's were karyotyped. In all cases a result was obtained and 138 (91%) had a detectable abnormal clone of which 44 (29%) were high-hyperdiploid. Within the high-hyperdiploidy group karyotypic cell to cell variation was observed in many cases. To provide further evidence of this phenomenon a dual-color fluorescence in-situ hybridization (FISH) experiment was performed on stored fixed suspension from 14 ALL's with such a karyotype. In each case 4-6 probes were investigated, employing probes to centromeres of chromosomes X, 4, 6, 8, and 10 and a locus specific probe to chromosome 21q22. It was found that the FISH produced results that were generally in good agreement with the G-banding findings and supported the notion of karyotypic cell to cell variation. FISH further showed that most of cases would have two extra copies of chromosome 21 in the majority of leukemic cells and a single extra copy in the minority. A further finding was that fewer cells contained extra copies of chromosomes 6, 8 and 10 than was expected based on the comparison of the signal number of the other probes investigated. In contrast chromosomes X, 4, and 21 seldom displayed this feature. We have demonstrated that karyotypic instability as defined by karyotypic cell to cell variation is a feature of the high-hyperdiploid subgroup in childhood ALL. It is questioned whether the underlying defect resulting in the observed karyotypic instability of this subgroup is one of the primary causative events in the formation of the leukemia.

Quassinoids: From traditional drugs to new cancer therapeutics.

Quassinoids are a group of compounds extracted from plants of the Simaroubaceae family, which have been used for many years in folk medicine. These molecules gained notoriety after the initial discovery of the anti-leukemic activity of one member, bruceantin, in 1975. Currently over 150 quassinoids have been isolated and classified based on their chemical structures and biological properties investigated in vitro and in vivo. Many molecules display a wide range of inhibitory effects, including anti-inflammatory, anti-viral, anti-malarial and anti-proliferative effects on various tumor cell types. Although often the exact mechanism of action of the single agents remains unclear, some agents have been shown to affect protein synthesis in general, or specifically HIF-1α and MYC, membrane polarization and the apoptotic machinery. Considering that future research into chemical modifications is likely to generate more active and less toxic derivatives of natural quassinoids, this family represents a powerful source of promising small molecules targeting key prosurvival signaling pathways relevant for diverse pathologies. Here, we review available knowledge of functionality and possible applications of quassinoids and quassinoid derivatives, spanning traditional use to the potential impact on modern medicine as cancer therapeutics.