Acute lymphoblastic leukemia with a late- appearing Philadelphia chromosome: case report and review of the literature.

UNLABELLED: We describe a rare presentation of acute lymphoblastic leukemia in a young adult male who at the beginning of the disease lacked the Philadelphia chromosome in bone marrow and blood cells and fluorescence in situ hybridization was negative for the presence of a clone with the BCR-ABL1 rearrangement. The patient initially had pancytopenia with a blast cell count of 5% in the peripheral blood that evolved to a phase with progressive leukocytosis and a sudden rise in blast cells 7 months later. At this time, his bone marrow aspirate showed the presence of a neartriploid karyotype containing two Philadelphia chromosomes. The multiple karyotypic changes observed in our patient support the notion that leukemic progression involves several cytogenetic evolutionary processes, the first step of which may not necessarily involve acquisition of the Philadelphia chromosome. KEYWORDS: Late-appearing Philadelphia chromosome, adolescent ALL, BCR-ABL1, dasarinib.

Secondary acute myeloid leukemia after successful treatment for osteosarcoma.

Secondary acute myeloid leukemia (sAML) is a rare complication following chemotherapy for osteogenic sarcoma. However, the exact offending drug is difficult to prove as there is no consistent data. It usually develops 2 years after completion of therapy. We report a case of sAML that developed within 8 months of completing the treatment. The patient was treated with cisplatin, doxorubicin and high-dose methotreaxate followed by surgery (amputation). Eight months after completion of therapy, while on follow-up, he presented with leukocytosis and thrombocytopenia and confirmed to have AML.

A novel variant translocation t(6;8;21)(p22;q22;q22) leading to AML/ETO fusion in acute myeloid leukemia.

Acute myeloid leukemia associated with translocation t(8;21) and the underlying AML1-ETO gene fusion is considered as a distinct type of leukemia with characteristic morphologic features. Variant and masked forms of the classic translocation t(8;21) are uncommon and their clinicopathologic features are less well characterized. We report here a patient with a masked translocation involving chromosomes 6,8 and 21. Chromosomal study at diagnosis initially reported the karyotype as translocation between chromosomes 6 and 8 without visible involvement of chromosome 21. However, fluorescence in situ hybridization studies revealed the involvement of chromosome 21 in the translocation and presence of the AML1-ETO chimeric gene. The complex rearrangement t(6;8;21) observed in our patient was not previously described and could be not detected without combination of techniques. Our case illustrates the challenge of recognizing complex aberrations that occur with variant t(8;21) and further reinforces the utility of fluorescence in situ hybridization applications in more accurate characterization of chromosome abnormalities which can lead to more precise therapeutic stratification.

Acute myeloid leukemia as a genetic disease. Review article.

The number of recurring genetic abnormalities recognized in acute myeloid leukemia (AML) has increased rapidly in recent years and at present, acute leukemia is probably the most extensively analyzed human cancer. Combined cytogenetic and molecular genetic studies have revealed that clonal chromosome abnormalities are present in the majority of patients with AML that are very closely, and sometimes uniquely, associated with distinct subsets of leukemia. Detailed analysis of these rearrangements indicates that in most instances chromosome rearrangements result in gene fusions leading to chimeric abnormal protein with oncogenic potential. Continued identification and characterization of genes involved in the development of leukemia has a major impact on our understanding of the molecular biology of cancer and in formulating of biologically based therapies.

All-transretinoic acid and chemotherapy in the treatment of acute promyelocytic leukemia.

BACKGROUND: All-transretinoic acid (ATRA) and chemotherapy has improved complete remission rates and disease free survival in acute promyelocytic leukemia (APL). There is scanty data from Middle East. AIM: To determine the efficacy of ATRA and multi-agent combination chemotherapy in treatment of APL in a single Centre in Kuwait. SET-UPS AND DESIGN: Tertiary cancer centre, retrospective study. METHODS AND MATERIAL: All newly diagnosed APL patients were treated with oral ATRA 45 mg/m2 daily until complete remission (CR), intravenous daunorubicin 50 mg/m2 on days 1,3 and 5, cytosine arabinoside 100 mg/m2 12 hrly on days 1 through 10 and etoposide 100 mg/m2 on days 1 through 5. Post remission three courses of intensive consolidation chemotherapy were administered. Since October 1999, maintenance chemotherapy consisting of oral 6 mercaptopurine 9 mg/m2 daily, methotrexate 15 mg/m2 weekly and ATRA 45 mg/m2 for 2 weeks every three months was added. Complete remission rates and duration, relapse rate and toxicity were studied. RESULTS: 22 of 24 evaluable patients (91.6%) achieved CR. The median duration of remission was 13 months (range 2-55 months). Three patients (12.5%) relapsed. Two patients (8.3%) developed retinoic acid syndrome and responded to dexamethasone. Five patients (20.8%) died one each of refractory disease, during remission induction and of relapse. Two patients died while in remission. CONCLUSION: ATRA and combination chemotherapy results in high complete remission rates and low relapse rate in newly diagnosed APL. Maintenance therapy may be useful in preventing relapses.

Chromosome aberrations in de novo acute myeloid leukemia patients in Kuwait.

Cytogenetic analysis was successfully performed at the time of diagnosis in 45 patients with de novo acute myeloid leukemia, including 10 children and 35 adults. In approximately 73% of AML patients (35 patients) clonal chromosome abnormalities were detected at the time of diagnosis. Twelve patients (22.8%) had apparently normal karyotypes. Recurring aberrations found in 22 of patients with abnormal karyotypes included t(15;17)(q22;q11), t(8;21)(q22;q22), inv(16)(p13q22), trisomy 8, monosomy 7 and del(5q). The highest frequency of chromosome changes was observed in AML-M3. The occurrence of the classical cytogenetic abnormalities was not a ubiquitous phenomenon. In 11 patients previously not described miscellaneous clonal chromosomal abnormalities were detected. Clonal chromosomal abnormalities detected in AML have shown correlations between specific recurrent chromosomal abnormalities and clinico-biological characteristics of the patients, therefore have been repeatedly shown to constitute markers of diagnostic and prognostic significance. Moreover, ongoing cytogenetic analysis can identify new nonrandom chromosome aberrations in AML and contribute to the identification of novel genes involved in the development of cancer, which can lead to better understanding of the disease pathogenesis.

Effects of heat shock on the Mre11/Rad50/Nbs1 complex in irradiated or unirradiated cells.

The mechanism by which hyperthermia sensitizes mammalian cells to ionizing radiation remains to be elucidated, but an overwhelming amount of circumstantial evidence suggests that heat radiosensitization might be mediated by inhibition of double-strand break repair, particularly after exposure of irradiated cells to heat treatments in excess of about 43 degrees C. In mammalian cells, double-strand break repair usually occurs via two pathways, non-homologous end-joining and homologous recombination. Several reports suggest a role for non-homologous end-joining in heat radiosensitization, while others implicate homologous recombination as a target. However, cell lines that are compromised in either the non-homologous end-joining or homologous recombination pathway are still capable of being radiosensitized, suggesting that heat affects both pathways. Indeed, several of the proteins involved in one or both of these pathways have been observed to undergo alterations or translocation after unirradiated or irradiated cells are exposed to heat shock. The work summarized in this review implicates proteins of the Mre11/Rad50/Nbs1 complex as targets for heat radiosensitization.

Mice overexpressing genes from the 22q11 region deleted in velo-cardio-facial syndrome/DiGeorge syndrome have middle and inner ear defects.

Velo-cardio-facial syndrome/DiGeorge syndrome (VCFS/DGS) is a congenital anomaly disorder associated with hemizygous 22q11 deletions. We previously showed that bacterial artificial chromosome (BAC) transgenic mice overexpressing four transgenes, PNUTL1, (CDCrel-1), GP1B beta, TBX1 and WDR14, had reduced viability, cardiovascular malformations and thymus gland hypoplasia. Since these are hallmark features of VCFS/DGS, we analyzed the mice for additional anomalies. We found that the mice have important defects in the middle and inner ear that are directly relevant to the disorder. The most striking defect was the presence of chronic otitis media, a common finding in VCFS/DGS patients. In addition, the mice had a hyperactive circling behavior and sensorineural hearing loss. This was associated with middle and inner ear malformations, analogous to Mondini dysplasia in humans reported to occur in VCFS/DGS patients. We propose that overexpression of one or more of the transgenes is responsible for the etiology of the ear defects in the mice. Based upon its pattern of expression in the ear and functional studies of the gene, TbX1 likely plays a central role. Haploinsufficiency of TBX1 may be responsible for ear disorders in VCFS/DGS patients.

Isolation and characterization of a novel gene containing WD40 repeats from the region deleted in velo-cardio-facial/DiGeorge syndrome on chromosome 22q11.

Three congenital disorders, cat-eye syndrome (CES), der(22) syndrome, and velo-cardio-facial syndrome/DiGeorge syndrome (VCFS/DGS), result from tetrasomy, trisomy, and monosomy, respectively, of part of 22q11. They share a 1.5-Mb region of overlap, which contains 24 known genes. Although the region has been sequenced and extensively analyzed, it is expected to contain additional genes, which have thus far escaped identification. To understand completely the molecular etiology of VCFS/DGS, der(22) syndrome, and CES, it is essential to isolate all genes in the interval. We have identified and characterized a novel human gene, located within the 1.5-Mb region deleted in VCFS/DGS, trisomic in der(22) syndrome and tetrasomic in CES. The deduced amino acid sequence of the human gene and its mouse homologue contain several WD40 repeats, but lack homology to known proteins. We termed this gene WDR14 (WD40 repeat-containing gene deleted in VCFS). It is expressed in a variety of human and mouse adult and fetal tissues with substantial expression levels in the adult thymus, an organ hypoplastic in VCFS/DGS.

Characterization of ataxia telangiectasia fibroblasts with extended life-span through telomerase expression.

Ataxia-telangiectasia (A-T) is an autosomal recessive disease characterized by progressive cerebellar degeneration, immunodeficiencies, genomic instability and gonadal atrophy. A-T patients are hypersensitive to ionizing radiation and have an elevated cancer risk. Cells derived from A-T patients require higher levels of serum factors, exhibit cytoskeletal defects and undergo premature senescence in culture. We show here that expression of the catalytic subunit of telomerase (hTERT) in primary A-T patient fibroblasts can rescue the premature senescence phenotype. Ectopic expression of hTERT does not rescue the radiosensitivity or the telomere fusions in A-T fibroblasts. The hTERT+AT cells also retain the characteristic defects in cell-cycle checkpoints, and show increased chromosome damage before and after ionizing radiation. Although A-T patients have an increased susceptibility to cancer, the expression of hTERT in A-T fibroblasts does not stimulate malignant transformation. These immortalized A-T cells provide a more stable cell system to investigate the molecular mechanisms underlying the cellular phenotypes of Ataxia-telangiectasia.

TBX1 is responsible for cardiovascular defects in velo-cardio-facial/DiGeorge syndrome.

Velo-cardio-facial syndrome (VCFS)/DiGeorge syndrome (DGS) is a human disorder characterized by a number of phenotypic features including cardiovascular defects. Most VCFS/DGS patients are hemizygous for a 1.5-3.0 Mb region of 22q11. To investigate the etiology of this disorder, we used a cre-loxP strategy to generate mice that are hemizygous for a 1.5 Mb deletion corresponding to that on 22q11. These mice exhibit significant perinatal lethality and have conotruncal and parathyroid defects. The conotruncal defects can be partially rescued by a human BAC containing the TBX1 gene. Mice heterozygous for a null mutation in Tbx1 develop conotruncal defects. These results together with the expression patterns of Tbx1 suggest a major role for this gene in the molecular etiology of VCFS/DGS.

Two functional copies of the DGCR6 gene are present on human chromosome 22q11 due to a duplication of an ancestral locus.

The DGCR6 (DiGeorge critical region) gene encodes a putative protein with sequence similarity to gonadal (gdl), a Drosophila melanogaster gene of unknown function. We mapped the DGCR6 gene to chromosome 22q11 within a low copy repeat, termed sc11.1a, and identified a second copy of the gene, DGCR6L, within the duplicate locus, termed sc11.1b. Both sc11.1 repeats are deleted in most persons with velo-cardio-facial syndrome/DiGeorge syndrome (VCFS/DGS), and they map immediately adjacent and internal to the low copy repeats, termed LCR22, that mediate the deletions associated with VCFS/DGS. We sequenced genomic clones from both loci and determined that the putative initiator methionine is located further upstream than originally described, but in a position similar to the mouse and chicken orthologs. DGCR6L encodes a highly homologous, functional copy of DGCR6, with some base changes rendering amino acid differences. Expression studies of the two genes indicate that both genes are widely expressed in fetal and adult tissues. Evolutionary studies using FISH mapping in several different species of ape combined with sequence analysis of DGCR6 in a number of different primate species indicate that the duplication is at least 12 million years old and may date back to before the divergence of Catarrhines from Platyrrhines, 35 mya. These data suggest that there has been selective evolutionary pressure toward the functional maintenance of both paralogs. Interestingly, a full-length HERV-K provirus integrated into the sc11.1a locus after the divergence of chimpanzees and humans.

Cystometric evaluation of bladder function in non-anesthetized mice with and without bladder outlet obstruction.

PURPOSE: To develop a model for cystometric study of bladder function in the awake mouse, and to characterize urodynamically and immunohistochemically the non-obstructed and infravesically obstructed mouse bladder. MATERIALS AND METHODS: Non-obstructed Balb/CJ mice, and mice with bladder outlet obstruction after surgical, partial ligation of the urethra underwent continuous cystometry as previously described for rats. Bladders were also investigated by immunohistochemistry. RESULTS: During the period of cystometry, reproducible micturition patterns were obtained. Marked differences in the urodynamic parameters between non-obstructed and obstructed mice were revealed. In mice subjected to urethral obstruction, micturition pressure (p <0.05), threshold pressure (p <0.05), bladder capacity (p <0.001), micturition volume (p <0.001), and residual volume (p <0.05) increased significantly. There was no difference in basal pressure or compliance between non-obstructed and obstructed mice. Non-voiding bladder activity was consistently recorded in obstructed mice; both frequency and amplitude increased significantly (p <0.01). Compared with non-obstructed bladders, obstructed bladders showed hypertrophy of the bladder wall and various degrees of "patchy denervation" of the detrusor. When tested in non-obstructed mice capsaicin, prostaglandin E2 (intravesical administration) and apomorphine (subcutaneous administration) induced bladder overactivity. CONCLUSIONS: Continuous cystometry can be reproducibly performed in awake, freely moving non-obstructed mice and mice with bladder outflow obstruction. The changes induced by infravesical obstruction in mice were similar to those previously found in rats. This model may be useful for investigations of genetically modified mice.

Functional characteristics of urinary tract smooth muscles in mice lacking cGMP protein kinase type I.

Nitric oxide (NO)-mediated smooth muscle relaxation is mediated by cGMP through activation of cGMP-dependent protein kinase I (cGKI). We studied the importance of cGKI for lower urinary tract function in mice lacking the gene for cGKI (cGKI-/-) and in litter-matched wild-type mice (cGKI+/+) in vitro and in vivo. cGKI deficiency did not result in any changes in bladder gross morphology or weight. Urethral strips from cGKI-/- mice showed an impaired relaxant response to nerve-derived NO. The cGMP analog 8-bromo-cGMP (8-BrcGMP) and the NO-donor SIN-1 relaxed the wild-type urethra (50-60%) but had only marginal effects in the cGKI-deficient urethra. Bladder strips from cGKI-/- mice responded normally to electrical field stimulation and to carbachol but not to 8-BrcGMP. In vivo, the cGKI-deficient mice showed bladder hyperactivity characterized by decreased intercontraction intervals and nonvoiding bladder contractions. Loss of cGKI abolishes NO-cGMP-dependent relaxations of urethral smooth muscle and results in hyperactive voiding. These data suggest that certain voiding disturbances may be associated with impaired NO-cGKI signaling.

Expression of Cdcrel-1 (Pnutl1), a gene frequently deleted in velo-cardio-facial syndrome/DiGeorge syndrome.

The murine Cdcrel-1 (Pnutl1) gene belongs to the family of septins, which are thought to be involved in cytokinesis in yeast, Drosophila and vertebrates. Recent studies implicate Cdcrel-1 in the regulation of vesicle transport in neurons of the adult brain. The human homologue, hCDCREL-1 maps to chromosome 22q11.2, a region commonly deleted in patients displaying velo-cardio-facial syndrome (VCFS) or DiGeorge syndrome (DGS). During development, Cdcrel-1 transcripts are expressed from E10.5 on in the nervous system such as the dorsal root ganglia and the cranial ganglia as well as the lateral layer of the neural tube, the area where terminally differentiated neurons are located. Low level expression is found in the mesenchyme of the frontonasal mass and the limb bud mesenchyme of E11.5 and E13.5 murine embryos. At E15.5, expression is detected in the nervous tissue and in the neural layer of the eye. Based on the expression pattern as well as clinical data, Cdcrel-1 may be involved in the etiology of VCFS/DGS.

Intravesical oxyhemoglobin initiates bladder overactivity in conscious, normal rats.

PURPOSE: To investigate whether intravesical oxyhemoglobin, a nitric oxide scavenger, changes bladder activity in normal rats. MATERIALS AND METHODS: Oxyhemoglobin was given intravesically at different concentrations to conscious, female Sprague-Dawley rats undergoing continuous cystometry. RESULTS: Intravesical oxyhemoglobin increased bladder activity in a concentration-dependent way. At a concentration of 2.5 x 10-4 M (n = 8), micturition pressure (p <0. 01), basal pressure (p <0.01), and residual volume (p <0.05) increased, and bladder capacity (p <0.001) and micturition volume (p <0.001) decreased. The effect of oxyhemoglobin was reduced or abolished by L-arginine (200 mg./kg.-1), given intra-arterially near the bladder, and was enhanced by the guanylate cyclase inhibitor, ODQ (0.5 and 1 mg./kg.-1). The K+ channel opener, ZD6169 100 ng.ml. -1, given intravesically for 1 hour prior to instillation of oxyhemoglobin, reduced or completely prevented the bladder activity induced by oxyhemoglobin. CONCLUSIONS: Intravesical oxyhemoglobin induces bladder overactivity, probably by interfering with nitric oxide (NO) generated in the urothelium or suburothelially. NO may be involved in the regulation of the threshold for afferent firing in the bladder.

A common breakpoint on 11q23 in carriers of the constitutional t(11;22) translocation.

Structural chromosomal rearrangements occur commonly in the general population. Individuals that carry a balanced translocation are at risk of having unbalanced offspring; therefore, the frequency of translocations in couples with recurrent spontaneous abortions is higher than that in the general population. The constitutional t(11;22) translocation is the most common recurrent non-Robertsonian translocation in humans and may serve as a model to determine the mechanism that causes recurrent meiotic translocations. We previously localized the t(11;22) translocation breakpoint to a region on 22q11 within a low-copy repeat, termed "LCR22." To define the breakpoint on 11q23 and to ascertain whether this region shares homology with LCR22 sequences, we performed haplotype analysis on patients with der(22) syndrome. We found that the breakpoint on 11q23 occurred between two genetic markers, D11S1340 and APOC3-tetra, both being present within a single bacterial-artificial-chromosome clone. To determine whether the breakpoint occurred within the same region among a larger set of carriers, we performed FISH mapping studies. The breakpoints were all within the same clone, suggesting that this region may harbor sequences that are prone to breakage. We narrowed the breakpoint interval, in both derivative chromosomes from two unrelated carriers, to a 190-bp, AT-rich repeat, which indicates that this repeat may mediate recombination events on chromosome 11. Interestingly, the LCR22s harbor AT-rich repeats, suggesting that this sequence motif may mediate recombination events in nonhomologous chromosomes during meiosis.

Effects of intravesical administration of the K+ channel opener, ZD6169, in conscious rats with and without bladder outflow obstruction.

PURPOSE: To investigate the urodynamic effects of the new K(ATP) channel opener, ZD6169, given intravesically, in rats with and without bladder outflow obstruction. MATERIALS AND METHODS: Female, conscious Sprague-Dawley rats, normal or with bladder hypertrophy and overactivity secondary to bladder outflow obstruction, were given ZD6169 intravesically (10 or 100 ng./ml.), and intra-arterially (1 mg./kg.). Continuous cystometry was performed. RESULTS: In normal and obstructed rats, intravesical ZD6169 had similar, dose-dependent effects on bladder function. In obstructed rats, ZD6169 (100 ng./ml.) significantly decreased micturition pressure (17%), and increased bladder capacity (32%), micturition volume (18%), residual volume (145%), and inter-contraction interval (71%). There was a marked decrease in both frequency (40%) and amplitude (43%) of the spontaneous bladder activity. When given intra-arterially in obstructed rats ZD6169 increased bladder capacity (19%) and residual volume (47%) and decreased amplitude (51%), but not frequency, of the spontaneous bladder activity. CONCLUSIONS: In both normal and obstructed rats, intravesical ZD6169, at the investigated doses, significantly affected bladder function. In obstructed rats, the drug markedly reduced bladder overactivity. If the results have clinical validity, intravesical ZD6169 may offer an alternative way of treating bladder overactivity in selected patients.

Sequential standard dose mitoxantrone and cytosine arabinoside for newly diagnosed adult acute myeloblastic leukemia.

Twenty one adult patients with previously untreated acute myeloblastic leukemia (AML) were treated with sequential mitoxantrone and standard dose cytosine arabinoside remission induction therapy. The median age was 33 years (range 17-56 years). Complete remission (CR) was achieved in 80% (17/21 cases) and 76% (16/21 cases) achieved CR after one course of induction therapy. The median duration of disease free survival was 9 months with an actuarial disease free survival of 22% at 43 months. The non-hematological toxicity was acceptable. We conclude that sequential mitoxantrone and cytosine arabinoside combination therapy is an effective antileukemic regimen which produces high CR rates in previously untreated adult patients with AML.