Reduced BRCA1 expression due to promoter hypermethylation in therapy-related acute myeloid leukaemia

BRCA1 plays a pivotal role in the repair of DNA damage, especially following chemotherapy and ionising radiation. We were interested in the regulation of BRCA1 expression in acute myeloid leukaemia (AML), in particular in therapy-related forms (t-AML). Using real-time PCR and Western blot, we found that BRCA1 mRNA was expressed at barely detectable levels by normal peripheral blood granulocytes, monocytes and lymphocytes, whereas control BM-mononuclear cells and selected CD34+ progenitor cells displayed significantly higher BRCA1 expression (P=0.0003). Acute myeloid leukaemia samples showed heterogeneous BRCA1 mRNA levels, which were lower than those of normal bone marrows (P=0.0001). We found a high frequency of hypermethylation of the BRCA1 promoter region in AML (51/133 samples, 38%), in particular in patients with karyotypic aberrations (P=0.026), and in t-AML, as compared to de novo AML (76 vs 31%, P=0.0002). Examining eight primary tumour samples from hypermethylated t-AML patients, BRCA1 was hypermethylated in three of four breast cancer samples, whereas it was unmethylated in the other four tumours. BRCA1 hypermethylation correlated to reduced BRCA1 mRNA (P=0.0004), and to increased DNA methyltransferase DNMT3A (P=0.003) expression. Our data show that reduced BRCA1 expression owing to promoter hypermethylation is frequent in t-AML and that this could contribute to secondary leukaemogenesis.     

Cutaneous zygomycosis due to Rhizopus oryzae in a patient with acute lymphoblastic leukemia

We report herein a case of primary cutaneous zygomycosis caused by Rhizopus oryzae in a 7-year-old girl with acute lymphoblastic leukemia (ALL) receiving intensive chemotherapy. The diagnosis was based on observation of hyphal elements in cutaneous biopsy and isolation of the fungus in culture. The patient responded to surgical intervention and treatment with amphotericin B.     

Septicemia due to Streptococcus equisimilis in a child with acute lymphoblastic leukemia.

A 4-year-old boy with acute lymphoblastic leukemia in relapse with documented septicemia due to group C Streptococci (Streptococcus equisimilis) is described. The patient responded well to therapy with appropriate cytotoxic and antimicrobial agents. There is a general lack of recognition of the pathogenicity of group C Streptococci in man. The potential opportunistic nature of these organisms in immunocompromised hosts and the need for early recognition and appropriate treatment of such infection is emphasized.     

Mechanisms of resistance to STI571 (Imatinib) in Philadelphia-chromosome positive acute lymphoblastic leukemia

Resistance against STI571 (Imatinib) appears to be multifactorial, but the most likely mechanisms can be broadly categorized as interference with the pharmacologic activity of STI571 or genetic changes which alter the biologic behaviour of the leukemic cells. In Ph+ ALL, responses to STI571 are not sustained, and in the overwhelming majority of patients development of resistance is rapid. Clinically, two types of resistance to STI571 can be distinguished: 'primary resistance', corresponding to a failure to achieve fewer than 5% blasts in the bone marrow, and 'secondary resistance' in patients with STI571-induced complete remission who relapse despite continued STI571 treatment. Attempts to identify mechanisms by which Ph+ ALL acquire resistance to STI571 have already been successful. Mutations in the ATP binding site of ABL are frequent events which counteract the antileukemic effect of STI571. Gene expression profiling has been shown to discriminate between resistant and sensitive leukemic cells. Application of this technique has also generated several hypotheses regarding the ability of leukemic cells to bypass the BCR-ABL signal transduction pathway. This may result in the proliferation of Ph+leukemic cells even in the presence of STI571.     

Abnormal methylation of the common PARK2 and PACRG promoter is associated with downregulation of gene expression in acute lymphoblastic leukemia and chronic myeloid leukemia

The PARK2 gene, previously identified as a mutated target in patients with autosomal recessive juvenile parkinsonism (ARJP), has recently been found to be a candidate tumor suppressor gene in ovarian, breast, lung and hepatocellular carcinoma that maps to the third common fragile site (CFS) FRA6E. PARK2 is linked to a novel described PACRG gene by a bidirectional promoter containing a defined CpG island in its common promoter region. We have studied the role of promoter hypermethylation in the regulation of PARK2 and PACRG expression in different tumor cell lines and primary patient samples. Abnormal methylation of the common promoter of PARK2 and PACRG was observed in 26% of patients with acute lymphoblastic leukemia and 20% of patients with chronic myelogenous leukemia (CML) in lymphoid blast crisis, but not in ovarian, breast, lung, neuroblastoma, astrocytoma or colon cancer cells. Abnormal methylation resulted in downregulation of PARK2 and PACRG gene expression, while demethylation of ALL cells resulted in demethylation of the promoter and upregulation of PARK2 and PACRG expression. By FISH, we demonstrated that a lack of PARK2 and PACRG expression was due to biallelic hypermethylation and not to deletion of either PARK2 or PACRG in ALL. In conclusion, our results demonstrate for the first time that the candidate tumor suppressor genes PARK2 and PACRG are epigenetically regulated in human leukemia, suggesting that abnormal methylation and regulation of PARK2 and PACRG may play a role in the pathogenesis and development of this hematological neoplasm.     

RAS mutation is associated with hyperdiploidy and parental characteristics in pediatric acute lymphoblastic leukemia.

We explored the relationship of RAS gene mutations with epidemiologic and cytogenetic factors in a case series of children with leukemia. Diagnostic bone marrow samples from 191 incident leukemia cases from the Northern California Childhood Leukemia Study were typed for NRAS and KRAS codon 12 and 13 mutations. A total of 38 cases (20%) harbored RAS mutations. Among the 142 B-cell acute lymphoblastic leukemia (ALL) cases, RAS mutations were more common among Hispanic children (P=0.11) or children born to mothers <30 years (P=0.007). Those with hyperdiploidy at diagnosis (>50 chromosomes) had the highest rates of RAS mutation (P=0.02). A multivariable model confirmed the significant associations between RAS mutation and both maternal age and hyperdiploidy. Interestingly, smoking of the father in the 3 months prior to pregnancy was reported less frequently among hyperdiploid leukemia patients than among those without hyperdiploidy (P=0.02). The data suggest that RAS and high hyperdiploidy may be cooperative genetic events to produce the leukemia subtype; and furthermore, that maternal age and paternal preconception smoking or other factors associated with these parameters are critical in the etiology of subtypes of childhood leukemia.     

Resistance to methotrexate due to gene amplification in a patient with acute leukemia

A patient is described with acute myelocytic leukemia refractory to conventional therapy, who also became highly resistant to methotrexate (MTX) after repeated courses of this drug. Leukemia cells from this patient were found to contain an elevated level of dihydrofolate reductase (DHFR) activity, with no change in the affinity of the enzyme for MTX. A sensitive "dot blot" assay revealed a fourfold increase in the gene copy number of DHFR. Southern blot analysis with a human DHFR cDNA probe confirmed this increase in the gene copy number, and demonstrated a similar restriction pattern with Eco R1, Hind III, and Pst 1 as seen with a highly amplified human leukemia cell line, K562. Additional DHFR fragments were detected, not seen in the K562 blot, suggesting the presence of pseudogenes, or a result of gene rearrangements occurring as part of the amplification process. Resistance to MTX in this patient was therefore ascribed to gene amplification and overproduction of DHFR.     

伊马替尼联合造血干细胞移植或化疗治疗bcr-abl+急性淋巴细胞白血病

 目的　探讨伊马替尼联合异基因造血干细胞移植（allo-HSCT）或化疗治疗bcr-abl+融合基因成年人急性淋巴细胞白血病（ALL）（以下简称成年人ALL）的疗效。方法　12例成年人ALL经骨髓细胞学、细胞化学、免疫学表型、bcr-abl融合基因检测确诊为bcr-abl+ ALL（B细胞型）。初治时接受伊马替尼联合化疗诱导治疗,伊马替尼剂量为400 mg／d。完全缓解（CR）后8例接受allo-HSCT治疗,移植后bcr-abl融合基因转为阳性者给予伊马替尼（400～600 mg／d）治疗,3例接受伊马替尼与化疗交替巩固治疗。结果　11例获得CR,CR率91.7 %;诱导治疗2个疗程时bcr-abl融合基因转阴率为41.7 %;8例接受移植患者3例复发,3例化疗与伊马替尼交替巩固治疗的患者2例复发,伊马替尼联合造血干细胞移植组与伊马替尼联合化疗组患者的中位缓解期分别为16个月与10个月（P＜0.01）;中位生存期为18个月与12个月（P＜0.01）。结论　伊马替尼联合化疗诱导治疗bcr-abl+成年人ALL有较高的血液学和分子生物学缓解率,伊马替尼联合allo-HSCT的疗效优于伊马替尼联合化疗。     

Imatinib for secondary Ph+ acute lymphoblastic leukemia induces response in concomitant GBM.

Imatinib is an inhibitor of tyrosine kinase currently employedfor the treatment of chronic myelogenous leukemia and inoperablegastrointestinal stromal tumor (GIST). Several trials [1, 2] have been conducted recently with imatinibas monotherapy for treatment of glioblastoma multiforme (GBM)and preliminar results suggest a good level of efficacy in this     

Is Mycoplasma Pneumonia associated with childhood acute lymphoblastic leukemia?

Acute lymphoblastic leukemia (ALL) in the childhood peak may be arare response to delayed first exposure to one or more common infectiousagent(s). Mycoplasma Pneumonia has the appropriate socioeconomic correlatesand clinical symptoms and the hypothesis that delayed first exposure to itmay contribute to ALL is considered. Counts of positive reports of MPneumonia from disease surveillance data for England and Wales (UnitedKingdom) for 1975-92 have been taken as proxies for community burden ofinfection. Variation by months of birth (cohort) and diagnosis (period) ofincidence of ALL in children born and diagnosed 1975-92 are compared withpredictions. When periods were classified by mean M Pneumonia count rate inthe nine preceding months, standardized morbidity ratios (SMR) for thehighest and lowest 20 percent were 108 and 89 (rate ratio [RR] = 1.2, 95percent confidence interval [CI] = 1.1-1.4). SMRs for cohorts with highestand lowest predicted risk (i.e., lowest and hi ghest M Pneumonia count ratearound birth and during infancy) were 110 and 97 (RR = 1.1, CI = 1.0-1.3).The trend for period was most marked in the cohorts with low opportunity forexposure when young. This ecologic analysis provides preliminary support forthe hypothesis.     

Tumor-specific down-regulation of the tumor necrosis factor-related apoptosis-inducing ligand decoy receptors DcR1 and DcR2 is associated with dense promoter hypermethylation

TRAIL (tumor necrosis factor-related apoptosis-inducing ligand) induces apoptosis in a large variety of cancer cells but not in most normal human cells. This feature makes TRAIL, a potential antitumor agent. TRAIL can bind to four different receptors, two pro-apoptotic death receptors (DRs), DR4 and DR5, and two antiapoptotic decoy receptors (DcRs), DcR1 and DcR2. Normal cells express all four of the receptors. The increased TRAIL sensitivity of tumor cells has been postulated to result from the lack of DcR expression. We studied the tumor-specific down-regulation of the TRAIL receptors DcR1 and DcR2, as well as DR4 and DR5, in a group of pediatric tumor cell lines [nine neuroblastoma and three peripheral primitive neuro-ectodermal tumors (PNETs)] and three cell lines from adult tumors. Lack of expression of DcR1 and DcR2 was widespread (13 of the 15 cell lines and 10 of 15, respectively), both in the adult tumor cell lines and in the pediatric tumor lines. DR4 and DR5 were expressed in 8 of 15 and 12 of 15 cell lines, respectively. To understand the tumor-specific down-regulation of the TRAIL receptors, the promoter regions were studied for possible methylation changes of their CpG islands. All normal tissues were completely unmethylated, whereas in the tumor cell lines, we found frequent hypermethylation of the promoter. For DcR1 and DcR2, we found dense hypermethylation in 9 (69%) of 13 and 9 (90%) of 10 of nonexpressing cell lines, respectively. DR4 and DR5 were methylated in 5 (71%) of 7 and 2 (67%) of 3 nonexpressing cell lines, respectively. Treatment with the demethylating agent 5-aza-2'deoxycytidine resulted in partial demethylation and restored mRNA expression. In addition, we performed mutation analysis of the death domains of DR4 and DR5 by sequencing exon 9. Mutations were not present in any of the neuroblastoma or PNET cell lines. A panel of 28 fresh neuroblastoma tumor samples also lacked expression of DcR1 and DcR2 in 85 and 74% of cases, respectively. Hypermethylation was observed in 6 (21%) of 28 for DcR1 and 7 (25%) of 28 for DcR2. DR4 and DR5 were both expressed in 22 of 28 tumors, and no promoter methylation was observed. These data suggest that hypermethylation of the promoters of DcR1 and DcR2 is important in the down-regulation of expression in neuroblastoma and other tumor types.     

Etoposide-induced apoptosis is not associated with the fas pathway in acute myeloblastic leukemia cells

Two subclones of the OCI/AML-2 cell line, etoposide-sensitive (ES) and etoposide-resistant (ER), established by the authors, were used as models. We investigated whether the Fas pathway is involved in etoposide-induced apoptosis in acute myeloblastic leukemia (AML). Both of the studied subclones expressed the Fas receptor (FasR), but only the ER cell line expressed the Fas ligand (FasL). Etoposide caused an increase in the mean fluorescence intensity of FasR in both subclones, and an induction of FasL in the ES subclone. However, no change in the numbers of apoptotic cells induced by etoposide was observed when FasR was blocked by an antagonist anti-Fas antibody, nor was an agonist anti-Fas antibody alone cytotoxic to the subclones or enhanced the cytotoxic effect of etoposide. The Fas-resistant phenotype of the AML cells was converted to a Fas-sensitive one by cycloheximide (CHX) suggesting the presence of an inhibitory protein of the Fas pathway in the cells. In etoposide-induced apoptosis, the effect of CHX was different, apoptosis-preventing. In conclusion, etoposide-induced apoptosis is not mediated by the Fas pathway in AML.     

Lack of mitochondrial depolarization by oxidative stress is associated with resistance to buthionine sulfoximine in acute lymphoblastic leukemia cells

Raised intracellular glutathione is one characteristics of high-risk childhood acute lymphoblastic leukemia (ALL). Depletion of glutathione by buthionine sulfoximine (BSO) has been reported to be toxic against some cancer cells. To assess the role of glutathione in ALL, the toxicity of BSO was studied in B-precursor ALL cell lines. BSO increased oxidative stress equally in all cell lines; however mitochondrial depolarization was observed only in BSO-sensitive cells. BSO up-regulated Bcl-2 protein, and antagonized the anti-ALL effect of prednisolone in BSO-resistant cells. A lack of mitochondrial death-signal activation by oxidative stress seemed to be associated with BSO-resistance in ALL.