Acute Myeloid Leukemia in Mexico: The Specific Challenges of a Developing Country. Results From a Multicenter National Registry

BACKGROUND

In the past decades, long-term survival outcomes for younger patients with acute myeloid leukemia (AML) have improved. Nonetheless, developing nations might be lagging behind, highlighting the need to assess real-world outcomes in such regions.

METHODS

We performed a multicenter retrospective study, which included patients with AML diagnosed between January 2013 and December 2017 from 13 centers in Mexico.

RESULTS

A total of 525 patients with AML met the inclusion criteria and were included in the study. Median age for the entire cohort was 47 years. The patients were classified according to cytogenetic risk: favorable 16.0%, intermediate 55.6%, and unfavorable 28.4%. Most patients received intensive chemotherapy (80.2%), and among these 74.1% underwent a 7 + 3 induction regimen. A complete remission was achieved in 71.3% of patients. Induction-related mortality occurred in 17.8% and we identify the following as independent risk factors: >60 years (odds ratio [OR] 2.09 [1.09-4.02]), Eastern Cooperative Oncology Group >2 (OR 4.82 [2.46-9.43]), prior solid tumor (OR 3.8 [1.24-11.59]) and active infection (OR 1.82 [1.06-3.12]). Further, allogeneic hematopoietic stem-cell transplantation (AlloHSCT) was performed in 8.2% in CR1. The 3-year overall survival (OS) was 34.8%. In a multivariate analysis, several factors were independently associated with a worse OS, including secondary AML (hazard ratio [HR] 2.14 [1.15-4.01]) and unfavorable cytogenetic risk (HR 1.81 [1.16-2.82]), whereas maintenance therapy (HR 0.53 [0.32-0.86]) and AlloHSCT (HR 0.40 [0.17-0.94]) were associated with better OS.

CONCLUSIONS

This is the first multicenter report analyzing AML survival in Mexico. Challenges in this setting include a high induction-related mortality and low AlloHSCT rate, which should be addressed to improve outcomes.

The inaccuracy of LaFarge equations estimating the oxygen consumption in children under 3 years age

Accurate oxygen consumption measurement (VO₂), is essential to obtain a reliable hemodynamic assessment, particularly in patients with congenital heart diseases undergoing cardiac catheterization. LaFarge equations can be unreliable in predicting VO₂, particularly in the pediatric population. In a clinical setting, these inaccurate estimates can lead to important hemodynamic parameter miscalculations, with possible therapeutic or diagnostic consequences. Our aim is to validate LaFarge equations (the most widely used for estimating VO₂) and compare them with direct measurement in children during cardiac catheterization in the cath lab. We performed a prospective observational study in 21 patients (0-3 years of age) with different congenital cardiac diseases, scheduled for diagnostic cardiac catheterization. Under general anesthesia and mechanical ventilation, VO₂ was measured directly with a metabolic module in our cath lab, and also estimated using LaFarge equations. Statistical analysis included Bland-Altman plots, Pearson coefficient and percentage error, among others. LaFarge equations overestimated VO₂ values in all study patients. Therefore, in pediatric patients under 3 years of age, the use of direct VO₂ measurement methods are more accurate and acceptable than LaFarge equations.

Identity, expression and functional role of the sodium-activated potassium current in vestibular ganglion afferent neurons

Vestibular afferent neurons (VANs) transmit information from the vestibular end organs to the central nuclei. This information is encoded within the firing pattern of these cells and is heavily influenced by the K⁺ conductances expressed by vestibular neurons. In the present study, we describe the presence of a previously unidentified Na⁺-activated K⁺ conductance (KNa) in these cells. We observed that the blocking of Na⁺ channels by tetrodotoxin (TTX) or the substitution of choline for Na⁺ in the extracellular solution during voltage clamp pulses resulted in the reduction of a sustained outward current that was dependent on the Na⁺ current. Furthermore, increases in the intracellular concentration of Na⁺ that were made by blocking the Na⁺/K⁺ ATPase with ouabain increased the amplitude of the outward current, and reduction of the intracellular Cl⁻ concentration reduced the TTX-sensitive outward current. The substitution of Li⁺ for Na⁺ in the extracellular solution significantly reduced the amplitude of the outward current in voltage clamp pulses and decreased the afterhyperpolarization (AHP) of the action potentials in current clamp experiments. These electrophysiological results are consistent with the presence of mRNA transcripts for the KNa subunits Slick and Slack in the vestibular ganglia and in the sensory epithelium, which were detected using reverse-transcription polymerase chain reaction (RT-PCR). These results are also consistent with the immunolabeling of Slick and Slack protein in isolated vestibular neurons, in the vestibular ganglion and in the vestibular sensory epithelium. These results indicate that KNa channels are expressed in VANs and in their terminals. Furthermore, these data indicate that these channels may contribute to the firing pattern of vestibular neurons.

Periodicity and patterns of Entamoeba histolytica and E. dispar infection in HIV+/AIDS patients in Mexico

In a 12-month longitudinal study, a cohort of Mexican HIV+/AIDS patients was checked several times for Entamoeba infection, with the parasites identified, as E. histolytica or E. dispar, using PCR. The polymorphic region of the parasites' chitinase genes was investigated by PCR, with the variation in amplicon sizes being used as a measure of the genetic variation among the isolates. The patients found infected with Entamoeba at the start of the study displayed varied patterns of infection clearance and re-infection. The analysis of the polymorphisms in the chitinase gene revealed seven polymorphic patterns in the E. histolytica isolates investigated and three in the E. dispar isolates. Many of the patients were each re-infected with Entamoeba at least once during the 12 months of follow-up. As seen in a previous study in Mexico, none of the E. histolytica-infected patients developed any clinical symptoms of invasive amoebiasis during the follow-up period. The results highlight the complexity of the host-parasite relationship in human amoebiasis.

Myeloablation enhances engraftment of transduced murine hematopoietic cells, but does not influence long-term expression of the transgene

To investigate to what extent myeloablation, graft size, and ex vivo manipulation influence the engraftment and long-term survival of transduced murine hematopoietic cells, groups of C57BL/6J (CD45.2) mice receiving total body irradiation (TBI) (1-9 Gy) or no irradiation were transplanted with either transduced bone marrow (BM) cells, at two cell doses, or with fresh BM cells from B6/SJL (CD45.1) congenic mice. Short (40 days) and long-term (5 months) engraftment and transgene expression were measured by FACS analysis. No donor cells were detected in the hematopoietic tissues of non-myeloablated mice, whereas in the irradiated animals, levels of engraftment correlated well with the dose of TBI administered. Similar percentages of transgene-expressing cells were found in the grafted hematopoietic cells of all groups of mice, regardless of the dose of TBI administered or the level of engraftment achieved. This suggests that the engrafted animals could become tolerant to the transgene product (enhanced green fluorescent protein, EGFP). Our results indicate that TBI facilitates the engraftment of manipulated hematopoietic cells in a dose-dependent manner, that mice engrafted with EGFP(+) hematopoietic cells probably acquire tolerance to EGFP, and that increasing the graft size and reducing the ex vivo manipulation required for retroviral gene transfer of hematopoietic cells also enhances their engrafting potential.

E1A modulates phosphorylation of p130 and p107 by differentially regulating the activity of G1/S cyclin/CDK complexes

We have previously shown that the adenoviral 12S E1A protein modulates the phosphorylation status of p130 and p107 without apparent changes in the cell cycle dependent phosphorylation of the retinoblastoma protein. Here we report on the mechanisms by which E1A modifies differentially the phosphorylation status of pocket proteins. In human U-2 OS osteosarcoma cells transiently expressing E1A, ectopic expression of D-type cyclins alone or combined, but not cyclins E and/or A, fully rescues E1A-mediated block in hyperphosphorylation of p130 to form 3. However, cyclins E and A, individually or together, induce hyperphosphorylation of p130 to species with intermediate mobility. Phosphopeptide maps indicate that E1A inhibits phosphorylation of sites phosphorylatable by CDKs. One of these sites is Ser-1044. The effects of blocking the activities of endogenous and exogenous cyclins with p16 and dominant negative CDK2 in E1A expressing cells further indicate that p130 is phosphorylated by both D-type cyclin and cyclin E/CDK complexes and that E1A modulates the activity of these G1/S CDKs by independent mechanisms. Stable expression of E1A in MC3T3-E1 cells leads to downregulation of D-type cyclins, and upregulation of cyclins E and A. This is accompanied by increased CDK2 kinase activity. Downregulation of D-type cyclins in these cells correlates with a block on both p130 hyperphosphorylation to form 3 and hyperphosphorylation of p107. This is rescued by D-type cyclins but not by cyclin E. In addition, we show that the upregulation of cyclins E and A is at least partially dependent on an intact pocket protein/E2F pathway, but downregulation of D-type cyclins is not. Moreover, we provide evidence that while the lack of a functional pRB pathway also results in a block on hyperphosphorylation of p130 to form 3, this is not sufficient to induce constitutive expression of p130 form 2b.

Efficient transduction of human hematopoietic repopulating cells generating stable engraftment of transgene-expressing cells in NOD/SCID mice

In an attempt to develop efficient procedures of human hematopoietic gene therapy, retrovirally transduced CD34(+) cord blood cells were transplanted into NOD/SCID mice to evaluate the repopulating potential of transduced grafts. Samples were prestimulated on Retronectin-coated dishes and infected with gibbon ape leukemia virus (GALV)-pseudotyped FMEV vectors encoding the enhanced green fluorescent protein (EGFP). Periodic analyses of bone marrow (BM) from transplanted recipients revealed a sustained engraftment of human hematopoietic cells expressing the EGFP transgene. On average, 33.6% of human CD45(+) cells expressed the transgene 90 to 120 days after transplantation. Moreover, 11.9% of total NOD/SCID BM consisted of human CD45(+) cells expressing the EGFP transgene at this time. The transplantation of purified EGFP(+) cells increased the proportion of CD45(+) cells positive for EGFP expression to 57. 7% at 90 to 120 days after transplantation. At this time, 18.9% and 4.3% of NOD/SCID BM consisted of CD45(+)/EGFP(+) and CD34(+)/EGFP(+) cells, respectively. Interestingly, the transplantation of EGFP(-) cells purified at 24 hours after infection also generated a significant engraftment of CD45(+)/EGFP(+) and CD34(+)/EGFP(+) cells, suggesting that a number of transduced repopulating cells did not express the transgene at that time. Molecular analysis of NOD/SCID BM confirmed the high levels of engraftment of human transduced cells deduced from FACS analysis. Finally, the analysis of the provirus insertion sites by conventional Southern blotting indicated that the human hematopoiesis in the NOD/SCID BM was predominantly oligoclonal.

E1A blocks hyperphosphorylation of p130 and p107 without affecting the phosphorylation status of the retinoblastoma protein

The phosphorylation status of the pRB family of growth suppressor proteins is regulated in a cell cycle entry-, progression-, and exit-dependent manner in normal cells. We have shown previously that p130, a member of this family, exhibits patterns of phosphorylated forms associated with various cell growth and differentiation stages. However, human 293 cells, which are transformed cells that express the adenoviral oncoproteins E1A and E1B, exhibit an abnormal pattern of p130 phosphorylated forms. Here we report that, unlike pRB, the phosphorylation status of both p130 and p107 is not modulated during the cell cycle in 293 cells as it is in other cells. Conditional overexpression of individual G(1)/S cyclins in 293 cells does not alter the phosphorylation status of p130, suggesting that the expression of E1A and/or E1B blocks hyperphosphorylation of p130. In agreement with these observations, transient cotransfection of vectors expressing E1A 12S, but not E1B, in combination with pocket proteins into U-2 OS cells blocks hyperphosphorylation of both p130 and p107. However, the phosphorylation status of pRB is not altered by cotransfection of E1A 12S vectors. Moreover, MC3T3-E1 preosteoblasts stably expressing E1A 12S also exhibit a block in hyperphosphorylation of endogenous p130 and p107. Direct binding of E1A to p130 and p107 is not required for the phosphorylation block since E1A 12S mutants defective in binding to the pRB family also block hyperphosphorylation of p130 and p107. Our data reported here identify a novel function of E1A, which affects p130 and p107 but does not affect pRB. Since E1A does not bind the hyperphosphorylated forms of p130, this function of E1A might prevent the existence of "free" hyperphosphorylated p130, which could act as a CDK inhibitor.

Occurrence of Hodgkin's disease and cutaneous B-cell lymphoma in the same patient: a report of two cases

The occurrence of Hodgkin's disease (HD) and non-Hodgkin's lymphoma (NHL) in the same patient is well known. The most frequent observation has been the development of large B cell lymphoma in patients affected with the nodular form of lymphocytic predominant HD. A less common situation is the development of NHL among patients successfully treated for HD. In such patients the second lymphoma has been thought to be related to the previous therapy or the immunodeficiency state that can accompany HD. Histologically, these NHL lymphomas often are intermediate to high grade and frequently extranodal. We report two patients successfully treated for HD who also developed NHL of the skin. Both patients presented with strikingly similar findings regarding to sex, age and subtype of HD. Clinical, histopathological and immunophenotypical findings were consistent with cutaneous low-grade B cell lymphoma of the marginal zone type. Both cases remain in complete remission of HD after standard therapy. In both patients the cutaneous lymphoma followed an indolent clinical course after a long follow-up period. This observation expands the spectrum of alterations possibly related to HD.

Cardiac involvement and molecular staging in a fatal case of mycosis fungoides

Polymerase chain reaction (PCR) amplification of T-cell receptor-gamma gene rearrangement was used for molecular staging in a case of primary cutaneous T-cell lymphoma (CTCL) with fatal evolution. Although initial evaluation was negative for systemic involvement, the patient died due to heart failure. Autopsy findings revealed lymphomatous myocardial infiltration, but other tissues and organs examined, including lymph nodes, liver, spleen, lung and bone marrow, appeared to be free of disease. Molecular analysis from frozen samples obtained during the initial evaluation, as well as paraffin-embedded material obtained during autopsy, revealed the presence of clonal rearranged bands in all tissues examined except the bone marrow. Subsequent hybridization of PCR products with a tumour-specific oligoprobe confirmed the PCR results, suggesting widespread dissemination of the lymphomatous process. The use of molecular analysis can add significant information about the extent of disease in patients with CTCL and may be helpful in the establishment of therapeutic options.

Retroviral gene transfer into human hematopoietic cells: an in vitro kinetic study

BACKGROUND AND OBJECTIVE

Successful gene therapy applications require optimized strategies to increase gene transfer efficiency into hematopietic progenitor cells (HPCs) with long-term repopulating ability. One of the issues that needs to be clarified is how hematopoietic cells proliferate, differentiate and express the transgene after each cycle of transduction. We investigated the kinetics of cell expansion, CD34 antigen expression and transduction efficiency of human hematopoietic cells in culture conditions commonly used in retroviral gene transfer protocols.

DESIGN AND METHODS

Purified CD34+ cells from cord blood (n=5) or leukapheresis products (n=9) and a retroviral vector encoding an enhanced version of the green fluorescent protein (EGFP) were used. Target cells were exposed daily to vector-containing supernatants and a combination of interleukin 3 (IL-3), interleukin 6 (IL-6), stem cell factor (SCF) and Flt3-ligand (FL). Cell samples were harvested from the cultures and analyzed at 24 hour intervals for seven consecutive days.

RESULTS

We found that CD34+ cells proliferated and differentiated under our culture conditions. The number of genetically modified cells increased after each cycle of transduction. Median numbers of cells positive for both CD34 and EGFP increased steadily over the culture period, but after day four most of the EGFP+ cells had a low CD34 expression.

INTERPRETATION AND CONCLUSIONS

Culturing and transducing CD34+ cells for longer periods of time under these conditions might be detrimental for ex vivo gene transfer applications since the transduced cells are likely to have a decreased potential for long-term engraftment and repopulation in vivo.

Inactive and temperature-sensitive folding mutants of aldehyde dehydrogenase of Escherichia coli

Aldehyde dehydrogenase, encoded by the aldA gene in Escherichia coli, is inactive in nitrosoguanidine induced mutant strain ECL40 and temperature-sensitive in spontaneous mutant strain JA104. Both mutants were proven, by complementation experiments, to have a functional aldA regulator and promoter. In spite of no immunodetection of the aldA product, its specific transcript was present in the mutant extracts. It was subsequently proven that the immunodetection of aldehyde dehydrogenase in these mutants required denaturation, revealing that cells lacking the enzyme activity had the inactive protein in their extracts. Thus, the mutations seemed to affect the protein conformation. The temperature-sensitive aldehyde dehydrogenase did not show, neither in vivo nor in vitro, a different thermal stability compared to the wild type enzyme. In this temperature-sensitive strain, the recovery of active aldehyde dehydrogenase, in the presence of rifampicin but not of chloramphenicol, when cells grown at 37 degrees C were shifted to 30 degrees C indicated that this mutation affected the folding process of the protein at the restrictive temperature. Sequencing of the two mutant aldA corresponding genes determined a single amino acid change of Pro to Leu at position 182 for strain ECL40, and of Val to Met at position 145 for strain JA104. These mutations were thought to possibly promote changes in the local flexibility in the first case, and to perturb the packing of residues by steric hindrance in the second case.

Immunomagnetic bone marrow (BM) and peripheral blood progenitor cell (PBPC) purging in follicular lymphoma (FL)

Twenty-nine B cell follicular lymphoma (FL) patients had their BM (n = 12) or PBPC (n = 17) purged using a panel of monoclonal antibodies and immunomagnetic beads (IMB). The median recovery of nucleated cells (NC) and CD34+ cells was 59.3% (40.5-74) and 56.1% (30.8-82.9) in BM and 77.2% (64.7-88.3) and 73.5% (61.5-98.6) in PBPC (P<0.0005). A median of >1.62 and >1.02 log of target cell depletion was achieved as judged by flow cytometry analysis in BM and PBPC, respectively. Of 29% of initial harvests that had a bcl2 PCR-amplified signal, 37.5% became PCR negative in the final purged products. Absorbed cells containing IMB-target cell complexes gave bcl2 rearrangement signal in 20% of samples in which the start and final purged components were negative. Twenty-three of 26 patients receiving an autologous purged product are evaluable for engraftment. Median time to reach an ANC >0.5x10(9)/l and platelet count >20x10(9)/l was 21 (11-43) and 41 days (13-70) for BM (n = 9) and 14 (10-31) and 14 (8-37) for PBPC (n = 14) autografted patients (P = 0.01 and 0.001). One patient did not engraft and was rescued with a back-up BM. These data demonstrate that this indirect immunomagnetic technique is able to achieve a high grade of lymphoma cell depletion in BM and PBPC and that these purged products are capable of rapid engraftment after autologous transplantation.

Highly efficient transduction of the green fluorescent protein gene in human umbilical cord blood stem cells capable of cobblestone formation in long-term cultures and multilineage engraftment of immunodeficient mice

Purified CD34(+) and CD34(+)CD38(-) human umbilical cord blood (UCB) cells were transduced with the recombinant variant of Moloney murine leukemia virus (MoMLV) MFG-EGFP or with SF-EGFP, in which EGFP expression is driven by a hybrid promoter of the spleen focus-forming virus (SFFV) and the murine embryonic stem cell virus (MESV). Infectious MFG-EGFP virus was produced by an amphotropic virus producer cell line (GP+envAm12). SF-EGFP was produced in the PG13 cell line pseudotyped for the gibbon ape leukemia virus (GaLV) envelope proteins. Using a 2-day growth factor prestimulation, followed by a 2-day, fibronectin fragment CH-296-supported transduction, CD34(+) and CD34(+)CD38(-) UCB subsets were efficiently transduced using either vector. The use of the SF-EGFP/PG13 retroviral packaging cell combination consistently resulted in twofold higher levels of EGFP-expressing cells than the MFG-EGFP/Am12 combination. Transplantation of 10(5) input equivalent transduced CD34(+) or 5 x 10(3) input equivalent CD34(+)CD38(-) UCB cells in nonobese diabetic/severe combined immunodeficient (NOD/SCID) mice resulted in median engraftment percentages of 8% and 5%, respectively, which showed that the in vivo repopulating ability of the cells had been retained. In addition, mice engrafted after transplantation of transduced CD34(+) cells using the MFG-EGFP/Am12 or the SF-EGFP/PG13 combination expressed EGFP with median values of 2% and 23% of human CD45(+) cells, respectively, which showed that the NOD/SCID repopulating cells were successfully transduced. EGFP+ cells were found in all human hematopoietic lineages produced in NOD/SCID mice including human progenitors with in vitro clonogenic ability. EGFP-expressing cells were also detected in the human cobblestone area-forming cell (CAFC) assay at 2 to 6 weeks of culture on the murine stromal cell line FBMD-1. During the transduction procedure the absolute numbers of CAFC week 6 increased 5- to 10-fold. The transduction efficiency of this progenitor cell subset was similar to the fraction of EGFP+ human cells in the bone marrow of the NOD/SCID mice transplanted with MFG-EGFP/Am12 or SF-EGFP/PG13 transduced CD34(+) cells, ie, 6% and 27%, respectively. The study thus shows that purified CD34(+) and highly purified CD34(+)CD38(-) UCB cells can be transduced efficiently with preservation of repopulating ability. The SF-EGFP/PG13 vector/packaging cell combination was much more effective in transducing repopulating cells than the MFG-EGFP/Am12 combination.

Differential regulation of the retinoblastoma family of proteins during cell proliferation and differentiation

In the present study we have analysed the regulation of pocket protein expression and post-transcriptional modifications on cell proliferation and differentiation, both in vivo and in vitro. There are marked changes in pocket protein levels during these transitions, the most striking differences being observed between p130 and p107. The mechanisms responsible for regulating pocket protein levels seem to be dependent on both cell type and pocket protein, in addition to their dependence on the cell growth status. Changes in retinoblastoma protein and p107 levels are independent of their state of phosphorylation. However, whereas p130 phosphorylation to forms characteristic of quiescent/differentiated cells results in the accumulation of p130 protein, phosphorylation of p130 to one or more forms characteristic of cycling cells is accompanied by down-regulation of its protein levels. We also show here that the phosphorylation status and protein levels of p130 and p107 are regulated in vivo as in cultured cells. In vivo, changes in p130 forms are correlated with changes in E2F complexes. Moreover, the modulation of p130 and p107 status during cell differentiation in vitro is consistent with the patterns of protein expression and phosphorylation status found in mouse tissues. Thus in addition to the direct disruption of pocket protein/E2F complexes induced by cyclin/cyclin-dependent kinase, the results we report here indicate that the differential modulation of pocket protein levels constitutes a major mechanism that regulates the pool of each pocket protein that is accessible to E2F and/or other transcription factors.

Genotypic analysis of cutaneous T-cell lymphoma: a comparative study of Southern blot analysis with polymerase chain reaction amplification of the T-cell receptor-gamma gene

The diagnosis of early cutaneous T-cell lymphoma (CTCL) is a difficult point in dermatology. Recently, Southern blot analysis (SBA) and polymerase chain reaction (PCR) have been used to detect clonality in initial lesions in which clinical and histological findings are unspecific. Forty-one samples from 25 patients with CTCL were investigated for the presence of T-cell receptor-gamma gene rearrangement using a nested PCR technique and analysed by polyacrylamide gel electrophoresis (PAGE). Conventional SBA was also performed on 28 samples from 20 of these patients. In addition, 20 samples corresponding to patients with large plaque parapsoriasis (LPP), cutaneous B-cell lymphoma (CBCL) and eczema were analysed by PCR in the same way as were the CTCL specimens. Most of the CTCL specimens (81%) showed clonality on PCR analysis. Among patients with mycosis fungoides, 71% of initial patch lesions and 100% of plaques and tumours showed clonal disease. Clonality could be detected in three of four histologically negative post-treatment lesions. Clonal rearrangement was detected in one of three patients with LPP and in three of 10 patients with CBCL. None of the samples corresponding to patients with eczema showed positive results. SBA was significantly less sensitive than PCR in detecting clonality in CTCL patients (42% among early disease and 60% among advanced cases). The results indicate that this PCR/PAGE technique is a reliable and useful method for the detection of clonality in early skin lesions of CTCL patients and probably in the identification of silent extracutaneous involvement.

High-titer retroviral vectors containing the enhanced green fluorescent protein gene for efficient expression in hematopoietic cells

Retroviral vectors constitute the most efficient system to deliver and integrate foreign genes into mammalian cells. We have developed a producer cell line that yields high titers of amphotropic retroviral vectors carrying the enhanced green fluorescent protein (EGFP) gene, a codon humanized, red-shifted variant of the green fluorescent protein (GFP) gene, which can be used as a selectable marker. We have used a hybrid vector that has been shown to efficiently drive gene expression in hematopoietic cells. Virtually all murine and human cell lines and primary human hematopoietic cells tested were transduced with varying efficiency after incubation with vector-containing supernatants. Human CD34(+) cells obtained from cord blood or aphereses products were transduced using a protocol that involves daily addition of vector-containing supernatants for 6 consecutive days. At day 6, up to 16% of the cells expressed EGFP, as assessed by flow cytometry. Sorted EGFP-expressing cells were able to produce fluorescent hematopoietic colonies. EGFP's main advantages are its fast flow cytometry determination and the possibility of cell sorting and simultaneous evaluation of the transduction efficiency along with other phenotypic markers.

A new human cell line with pre-B cell phenotype and t(5;12)

A new cell line (LR10.6) with pre-B cell phenotype has been established from bone marrow cells obtained from a child with B lineage acute lymphoblastic leukemia in complete clinical remission. The line expresses nuclear TdT enzyme, cytoplasmic Ig lambda-chain and membrane mu-chain and other B but no T or myeloid markers. The cells also show activation antigens CD69 and CD71, adhesion molecules CD54, CD50 and CD56 and the tyrosine kinase receptor CD117. No expression of multidrug resistance phenotype MDR-1 is observed on these cells which nevertheless express the transcriptional factor p53 protein in a mutant form. Cytogenetic study shows a translocation t(5;12)(q31;p13) involving breakpoints which contain the growth factor interleukin 3 gene (5q31) and the recently identified TEL/ETV6 gene (12p13). Activation of the cells with phorbol-12 myristate 13-acetate (PMA) up-regulates the expression of the CD69 activation antigen and down-regulates the CD117 molecule. In addition, PMA fails to induce the CD20 B cell antigen.

A second Escherichia coli gene with similarity to gapA

An open reading frame has been found downstream of the ald gene at 31 min in the Escherichia coli chromosome and has been designated gapC because of its high similarity with gapA (min 39, encoding glyceraldehyde-3-phosphate dehydrogenase), and with gapB (min 62, a gene with high similarity to gapA, encoding erythrose-4-phosphate dehydrogenase). The gapC gene (min 31) encodes a polypeptide of 204 amino acids, 126 residues shorter than glyceraldehyde-3-phosphate dehydrogenase. In this 204-codon open reading frame several amino acids important for catalysis are conserved. However, the cofactor binding site is lost. The results illustrate a case of a gene, encoding a glycolytic enzyme, for which at least three copies maintaining a certain degree of similarity are apparent in the E. coli genome. It seems likely that the genes encode products with different cellular functions. The origin of these three copies of the gap gene by horizontal transfer or by duplication of an ancestral gene is discussed.

[Frequency of allergens in immediate, late, and dual allergic skin response at the National Institute of Pediatrics]

We studied 126 children with allergic illness in Instituto Nacional de Pediatria. We applied cutaneous test to determine the early, late and dual response. The results were 68% for the early response, 6% late response and 26% dual response. The allergens more frequently found in the early and late response were Dermatophagoides pteronyssinus, Dermatophagoides farinae and house dust. Approximately the third part of the children studied presented late cutaneous response (dual response more isolated late response). It is important to make the evaluation of the late response in patients with allergy disease for a good etiologic diagnosis.

Presentation of a PCR-nuclease protection strategy for minimal residual disease monitoring in B-ALL

Methods for detecting residual malignant cells in patients suffering from lymphoid malignancies have neither been sufficiently sensitive nor easy to routinize, hampering a potential prediction of disease outcome. Taking advantage of clone-specific DNA sequences, generated during lymphocyte differentiation and the polymerase chain reaction, some strategies have been developed for several groups. Up to now the most specific and sensitive methodology, which consists of designing leukemia-specific oligonucleotides, requires sequencing of the complementary determining region III-DNA for each particular patient and is too laborious to be applied to each case for routine monitoring in most hospital laboratories. In an attempt to achieve an easy way to detect residual malignant cells in B lymphoproliferative diseases, we have used a new PCR-based approach, named here as PCR-nuclease protection assay, consisting of: (i) amplification of DNA segments corresponding to the complementarity determining region III of the immunoglobulin heavy chain genes from samples at disease diagnosis; (ii) isolation of the disease-specific single-stranded DNA; (iii) labeling of the single-stranded DNA to generate specific probes; (iv) hybridization to amplified DNA from samples corresponding to different disease phases; and (v) digestion with S1-nuclease. Using this approach, we could detect one malignant cell in a background of 10(5) healthy cells. The sensitivity and specificity of this approach compares with those of the above mentioned specific oligonucleotide strategy in detecting residual malignant B cells. Moreover, this strategy is much less tedious and could be used by most hospital laboratories.