Biomedical subjects

A T Look

Publications and source records attributed to A T Look.

At least 127 records · Page 7Linked to original sources

PubMed1992

Assignment of the genes encoding human interleukin-8 receptor types 1 and 2 and an interleukin-8 receptor pseudogene to chromosome 2q35.

Two human cDNA clones that encode different interleukin-8 (IL8) receptors have recently been isolated. The interleukin-8 receptor type 1 (IL8R1) binds IL8 only, whereas the interleukin-8 receptor type 2 (IL8R2) (previously designated IL8RA) also binds growth regulated gene (GRO), and neutrophil activating protein-2 (NAP-2) with high affinity. In the process of screening a genomic library with these cDNAs to obtain large clones for use in chromosomal localization studies, we isolated an interleukin-8 receptor pseudogene (IL8RP) that bears greatest similarity to IL8R2. Using Southern hybridization analysis of human x rodent somatic cell hybrid DNAs with cDNA probes for IL8R1 and IL8R2 and probes from the IL8RP locus, we assigned the three loci to chromosome 2; fluorescence in situ hybridization (FISH) to metaphase chromosome preparations using genomic clones from each locus refined this localization to chromosome 2, band q35, for all three. By virtue of their chromosomal location, IL8R1 and IL8R2 may be considered candidate genes for several human disorders in which the involved locus has been mapped to distal 2q or that are associated with structural abnormalities of this segment, including van der Woude syndrome and the neoplastic diseases rhabdomyosarcoma and uterine leiomyomata. In addition, because this region of chromosome 2q is homologous to proximal mouse chromosome 1 in the segment containing the Lsh-Ity-Bcg locus involved in mediating host resistance to infection with intracellular pathogens, examination for abnormalities of the murine homologues of the IL8R genes should be considered in mice affected by mutations of this locus.

Amino Acid Sequence↗

PubMed1992

Monoclonal antibodies defining shared human macrophage-endothelial antigens.

We have selected several monoclonal antibodies (mAbs) producing using human rheumatoid arthritis (RA) synovial macrophages (m phi s) as immunogen. Of these, mAbs 8H2, 10G7 and 10G9 showed cross reactivity with endothelium, suggesting common antigens between these cell types. We have determined the spectrum of reactivity of these mAbs on hematopoietic cell lines, peripheral blood cells, and inflammatory and non-inflammatory tissues by immunohistochemistry. MAb 8H2 does not react with the myeloid cell lines HL60 (myelocytic), U937 (histiocytic lymphoma), and K562 (erythroleukemia), or with peripheral blood cells. In normal and inflamed tissue sections, mAb 8H2 reacts with m phi s and endothelial cells. In contrast, mAb 10G7 does not react with peripheral blood cells, but reacts with HL60, U937, and K562 cell lines, as well as with m phi s and endothelial cells in inflamed and noninflamed tissues. MAb 10G9 does not react with myeloid cell lines, but reacts with monocytes and platelets in peripheral blood. In both normal and inflamed tissues, mAb 10G9 reacts with m phi s and endothelial cells. The antigens identified by these three mAbs were characterized biochemically, by enzymatic digestion of RA synovial tissue m phi s followed by a cellular ELISA, as well as by reactivity of the mAbs with NIH-3T3 cells genetically engineered to express known myeloid antigens. These mAbs reacted with protein or glycoprotein antigens distinct from the known myeloid antigens CD13, CD14, CD33, CD34, CD36, and c-fms. These mAbs should prove to be a valuable tool for studying m phi s and endothelial cells and their shared antigenic determinants.

3T3 Cells↗

PubMed1991

Reassignment of the human CSF1 gene to chromosome 1p13-p21.

Human macrophage colony-stimulating factor (CSF-1 or M-CSF) is encoded by a single gene that was previously assigned to the long arm of chromosome 5, band q33.1, in a region adjacent to the gene encoding its receptor (Pettenati MJ, et al, Proc Natl Acad Sci USA 84:2970, 1987). Using fluorescence in situ hybridization with genomic probes to examine normal metaphase chromosomes, we reassigned the human CSF1 gene to the short arm of chromosome 1, bands p13-p21. We confirmed this result by hybridizing a CSF1 cDNA probe to filters containing flow-sorted chromosomes and by identifying CSF1 sequences in DNAs extracted from human x rodent somatic cell hybrids that contained human chromosome 1 but not human chromosome 5. Our findings are consistent with studies that have shown tight linkage between the murine CSF1 and amylase genes, as part of a conserved linkage group between mouse chromosome 3 and the short arm of human chromosome 1, which also includes the genes encoding the beta subunits of thyrotropin and nerve growth factor. Assignment of the CSF1 gene to chromosome 1 at bands p13-p21 raises the possibility that it may be altered by certain nonrandom chromosomal abnormalities arising in human hematopoietic malignancies and solid tumors.

Cell Line↗

PubMed1991

Separate promoters control transcription of the human aminopeptidase N gene in myeloid and intestinal epithelial cells.

Aminopeptidase N is a membrane-bound metalloprotease expressed on the surface of normal and malignant human myeloid cells, fibroblasts, hepatocytes, and the epithelial cells that form brush borders of the small intestine and kidney. Northern blot analysis of RNA extracted from these tissues revealed two distinct aminopeptidase N transcripts: a 3.7-kilobase (kb) transcript expressed by normal monocytes, myeloid leukemia cells, and fibroblasts and a 3.4-kb transcript expressed by intestinal epithelium and kidney cells. In intestinal epithelial cells, transcripts originated 47 base pairs upstream from the initiation codon and 22 base pairs downstream from a TATA box. By contrast, the longer transcripts found in myeloid cells and fibroblasts originated from several sites clustered in an upstream exon located 8 kb from the exon containing the initiation codon. Functional promoter activity was demonstrated by fusing sequences approximately 1 kb upstream from each transcription origin to bacterial reporter genes and transfecting the resultant constructs into murine NIH-3T3 fibroblasts. A novel feature of this system is that regulatory elements of the epithelial cell promoter, including the TATA box and transcription origin, are included within the 5'-untranslated region of the longer myeloid cell transcript. Both aminopeptidase N transcripts encode the same polypeptide, indicating that the physically distinct promoters must have evolved to regulate expression of this cell-surface peptidase by cells of different tissues.

Aminopeptidases↗

PubMed1991

New recurring chromosomal translocations in childhood acute lymphoblastic leukemia.

We identified seven new recurring translocations among 483 cases of acute lymphoblastic leukemia (ALL) with adequate chromosome banding studies. Four were apparently balanced [t(1;3)(p34;p21), t(7;9)(p15;p23-p24), t(12;13)(p13;q14), t(17;19)(q22;p13)], while three were unbalanced with the formation of a dicentric chromosome [dic(7;9)(p13;p11), dic(7;12)(p11;p12), and dic(12;17)(p11;p11-p12)]. One translocation was observed in five cases, two in four cases, and the remaining four in two cases each. The modal chromosome numbers in these 21 cases were 45 (n = 11), 46 (n = 8), and 47 (n = 2). Eight of the 11 cases with a dicentric chromosome had a modal number of 45. Only a single translocation was found in 14 cases (67%), representing the sole structural abnormality in six cases. In three of the seven translocation subgroups, the blast cells were consistently of B lineage (pre-B, early pre-B, or both); in all others, they represented both the B and T lineages. The small size of these subgroups prevented definitive clinical correlations, although it may be important that two of the four cases with a t(17;19) and an early pre-B-cell immunophenotype had disseminated intravascular coagulation, an event usually observed in acute promyelocytic leukemia or T-cell ALL. These findings add substantially to the existing list of nonrandom chromosomal translocations in childhood ALL and may help to explain the genetic alterations leading to the loss of normal growth control mechanisms in this disease.

Adolescent↗

PubMed1991

Improved outcome in childhood acute lymphoblastic leukaemia with reinforced early treatment and rotational combination chemotherapy.

To improve outcome in childhood acute lymphoblastic leukaemia (ALL), a stratified, randomised study of extended intensified chemotherapy was done. 358 evaluable patients received remission reinforcement therapy (teniposide, cytarabine, high-dose methotrexate) added to a four-drug induction regimen. Those achieving complete remission were randomised on the basis of risk group assignment to conventional continuation treatment or to four pairs of drugs rotated weekly or every 6 weeks. All patients received intrathecal chemotherapy; higher-risk patients also received 1800 cGy cranial irradiation after 1 year of remission. Complete remission was induced in 96% of the patients. At median follow-up of 40 (range 19-73) months, 4-year event-free survival (SE) was 73 (4)% overall, 81 (6)% in the lower-risk group (n = 110), and 69 (5)% in the higher-risk group (n = 248). Outcome within risk groups was not significantly affected by the speed of rotation of drug pairs during continuation treatment. Various high-risk subgroups had apparently improved responses to this treatment. This intensified chemotherapy may cure 69-77% of children with ALL.

Actuarial Analysis↗

PubMed1991

The human t(1;19) translocation in pre-B ALL produces multiple nuclear E2A-Pbx1 fusion proteins with differing transforming potentials.

The t(1;19) translocation that characterizes 25% of pediatric pre-B cell acute lymphoblastic leukemias (pre-B ALL) produces a chimeric gene, joining 5' sequences that encode a transcriptional activator domain of E2A with 3' sequences that, in part, encode a homeo box domain of a new gene called pbx1. Two E2A-pbx1 transcripts have been cloned. They encode the putative fusion proteins, p85(E2A-Pbx1) and p77(E2A-Pbx1), which differ in Pbx1 sequences alone, containing unique carboxyl termini whose sequences diverge after the Pbx1 homeo box. In this study, an antiserum to Pbx1 was used to investigate the identity and abundance of E2A-Pbx1 fusion proteins in both the pre-B ALL cell line, 697, and in cryopreserved leukemic bone marrow cells, obtained from six children with t(1;19)-positive pre-B ALL. Five species of E2A-Pbx1 proteins were identified in all cells containing t(1;19), two of which were indistinguishable from in vitro-translated p85(E2A-Pbx1) and p77(E2A-Pbx1). To assess the biological properties of p85(E2A-Pbx1) and p77(E2A-Pbx1) in fibroblasts, the cDNAs encoding these proteins were cloned into retroviral vectors, and each was introduced into NIH-3T3 cells. Both p85(E2A-Pbx1) and p77(E2A-Pbx1) are localized in the nucleus, and expression of either resulted in malignant conversion of NIH-3T3 cells as assayed by tumor formation in nude mice. When scored by focus formation, density-independent growth, and growth in agar assays, p77(E2A-Pbx1) was a much more potent transforming protein than was p85(E2A-Pbx1). Because subtle mutations in p85(E2A-Pbx1) converted its transforming activity into that of p77(E2A-Pbx1), we suggest that a sequence within the unique carboxyl terminus of p85(E2A-Pbx1) serves to negatively regulate its biochemical activity.

Animals↗

PubMed1991

Relationship of tumor-cell ploidy to histologic subtype and treatment outcome in children and adolescents with unresectable rhabdomyosarcoma.

Clinical and histopathologic features are often inadequate for accurate prediction of relapse or survival of individual patients with rhabdomyosarcoma (RMS). We therefore studied the cellular DNA content (ploidy) of RMS cells in relation to histology and response to therapy in 37 patients with unresectable tumors. Using flow cytometric techniques, we found that about one third of patients had diploid tumor stem lines, regardless of the histologic subtype. In the group with abnormal ploidy, a hyperdiploid classification (1.10 to 1.80 times the DNA content of normal diploid cells) was exclusively associated with embryonal histology (P = .001). By contrast, near-tetraploidy (1.80 to 2.60 times the DNA content of normal cells) was strongly associated with alveolar histology (P = .001). Thus, in these histologic subtypes of RMS, abnormal ploidy appears to arise through different mechanisms. Tumor-cell ploidy had a significant impact on survival that was especially apparent in patients with unresectable, nonmetastatic (group III) tumors. In this subgroup, hyperdiploidy conferred the best prognosis and diploidy the worst (P less than .0001). None of the eight patients with diploid tumors survived for more than 18 months. Tumor-cell ploidy was the best predictor of treatment outcome for patients with either embryonal (P less than .001; relative risk, 25.5) or alveolar (P = .073; relative risk 7.1) RMS and contributed significantly after adjustment for disease stage and anatomic site. Patients with unresectable diploid RMS have an unacceptably high risk of treatment failure, justifying new therapeutic approaches for this distinct subgroup.

Adolescent↗

PubMed1991

Clinical relevance of tumor cell ploidy and N-myc gene amplification in childhood neuroblastoma: a Pediatric Oncology Group study.

We assessed tumor cell DNA content (ploidy) and N-myc gene copy number as predictors of long-term disease-free survival in 298 children with neuroblastoma. Diploid tumor stem lines were identified in 101 patients (34%), clonal hyperdiploid abnormalities in 194 (65%), and hypodiploid stem lines in three (1%). In children with widely disseminated tumors at diagnosis (stage D), ploidy had a highly age-dependent influence on prognosis. Among infants (less than 12 months) treated with cyclophosphamide-doxorubicin, hyperdiploidy was closely associated with long-term disease-free survival (greater than 90% of cases), while diploidy invariably predicted early treatment failure (P less than .001). Similarly, in children 12 to 24 months of age who were treated with cisplatin-teniposide and cyclophosphamide-doxorubicin, diploidy uniformly predicted early failure, whereas half of the children with hyperdiploidy achieved long-term disease-free survival (P less than .001). There was no relationship between ploidy and treatment outcome in children older than 24 months with stage D tumors who had a very low probability of long-term disease-free survival (less than 10%). N-myc gene amplification was detected in 37 (25%) of the 147 tumors tested, with the remainder showing single-copy levels of the gene. N-myc gene amplification was more frequent in diploid than in hyperdiploid tumors (23 of 57 v 14 of 87, P = .001) and predicted a high likelihood of early treatment failure. In children younger than 2 years with disseminated neuroblastoma, tumor cell ploidy and N-myc gene copy number provide complementary prognostic information that will distinguish patients who can be cured on current regimens from those who require new treatment strategies.

Age Factors↗

PubMed1991

Risk of adverse events in children completing treatment for acute lymphoblastic leukemia: St. Jude Total Therapy studies VIII, IX, and X.

We studied the frequency, causes, and predictors of adverse events in 624 patients who had completed treatment for acute lymphoblastic leukemia (ALL) in three consecutive total therapy studies (VII, IX, and X, 1972 to 1983). Event-free survival in study X was significantly better overall than that in studies VIII and IX (P less than .0001 by the log-rank test). In study X, 75% of the patients were electively taken off therapy, compared with 54% in studies VIII and IX. However, the risks of having an adverse event during the first 5 years after completion of therapy were remarkably similar: 22% (95% confidence interval, 17% to 29%) in study X versus 24% (20% to 29%) in studies VIII and IX. Bone marrow, testicular, and CNS relapses accounted for the majority of failures in both groups (85% in study X and 92% in studies VIII and IX). Late adverse events consisted largely of hematologic relapses and the development of solid tumors. Black race (P = .001) and leukemia without an anterior mediastinal mass (P = .05) were associated with an increased risk of failure after completion of treatment in the two earlier clinical trials, whereas a lower leukemic cell DNA content (DNA index less than 1.16) was the only predictor of late treatment failure in the more recent trial (P = .019). None of the other presenting features that were examined (eg, age, leukocyte count, and sex) had value as predictors of late failure. Thus, improved treatment altered the impact of specific prognostic factors and the distribution of sites of relapse, but it did not significantly affect the risk of delayed failure.

Adolescent↗

PubMed1990

Biology and clinical significance of cytogenetic abnormalities in childhood acute lymphoblastic leukemia.

Virtually all cases of childhood ALL have chromosomal abnormalities and half contain translocations, which are nearly equally divided between random and nonrandom rearrangements. Nonrandom chromosomal abnormalities have been correlated with leukemic cell lineage, the degree of cell differentiation, and the specific gene involved at the molecular level. Many cytogenetic findings have prognostic significance; however, the adverse influence of certain changes, including most chromosomal translocations, may in fact be offset by the greater cytoreductive effects of intensified therapy. Table 4 summarizes the relation of selected karyotypic findings to treatment outcome in patients treated on contemporary protocols. Among all of the chromosomal abnormalities identified in childhood ALL, hyperdiploidy greater than 50 has been associated with the most favorable prognosis. At the opposite end of the spectrum, the treatment outcome for patients with classical Ph+ or hypodiploid ALL is very poor even in programs of intensive chemotherapy; alternative treatment such as bone marrow transplantation should be considered for such patients. Cases with the t(4;11)(q21;q23) also have a very poor clinical outcome, but the adverse prognosis may be limited to the infant or adolescent age groups. The prognostic significance of other nonrandom translocations, such as t(1;19)(q23;p13) and several other abnormalities, needs to be further assessed in larger numbers of patients. Finally, as more is learned about the molecular pathology underlying these rearrangements, it may be possible to develop new therapeutic agents that are specifically targeted to interfere with the aberrant gene products expressed by human leukemic cells.

Child↗

PubMed1990

Abnormalities of the long arm of chromosome 6 in childhood acute lymphoblastic leukemia.

To determine the biologic significance of the structural rearrangements of the long arm of chromosome 6(6q) in acute lymphoblastic leukemia (ALL) at diagnosis, we studied 412 consecutive children whose leukemic cell chromosomes had been completely banded and identified 45 (11%) children with this abnormality. The 45 cases were divided into del(6q) only (n = 11), del(6q) and numerical abnormalities (n = 4), del(6q) and structural abnormalities (n = 23), and 6q translocations (n = 7). The breakpoints of del(6q) were subgrouped: del(6)(q15q21) in 11 cases, del(6) (q13q21) in six, del(6)(q21q23) in four, del(6)(q15) in four, del(6)(q15q23) in three, and other deletions in 10 cases. Notably, all these deletions encompassed the 6q21 band, suggesting that this might be the locus of a recessive tumor suppressor gene, the absence of which contributes to malignant transformation or proliferation. Among the seven children with 6q translocations, a previously unidentified nonrandom translocation, t(6;12)(q21;p13) was noted in two cases with an early pre-B immunophenotype. Clinical features and event-free survival were similar among children with or without 6q abnormalities. Overall, children with 6q abnormalities were less likely than those without the abnormality to have a pre-B immunophenotype (P = .03). T-cell immunophenotypes were equally represented in cases with or without 6q abnormalities. However, all four children with del(6q) and a 12p abnormality had early pre-B ALL and all three children with del(6q) and a 9p abnormality had a T-cell immunophenotype. The lack of specificity for a particular immunophenotype may imply that the gene or genes affected by 6q abnormalities are broadly active in the multistep process of lymphoid leukemogenesis. The relatively high frequency of microscopically visible del(6q) indicates the need for molecular studies to identify cases with submicroscopic deletions.

Child↗

PubMed1990

Poor prognosis of children with pre-B acute lymphoblastic leukemia is associated with the t(1;19)(q23;p13): a Pediatric Oncology Group study.

The prognostic significance of chromosomal translocations, particularly t(1;19) (q23;p13), was evaluated in children with pre-B and early pre-B acute lymphoblastic leukemia (ALL). Patients were treated on a risk-based protocol of the Pediatric Oncology Group (POG) between February 1986 and May 1989. An abnormal clone was detected in 46% (130 of 285) of pre-B cases and 56% (380 of 679) of early pre-B cases. Translocation of any type was associated with a worse treatment outcome than other karyotypic abnormalities: 15 of 66 versus 3 of 64 failed therapy in the pre-B group (P = .001), and 37 of 141 versus 23 of 239 failed in the early pre-B group (P less than .001). The t(1;19) (q23;p13) occurred significantly more often in cases of pre-B ALL with a clonal abnormality than in early pre-B ALL cases (29 of 130 v 5 of 380, P less than .001). Among the 285 pre-B cases in which bone marrow was studied cytogenetically, those with t(1;19) had a significantly worse treatment outcome than all others (11 of 29 v 27 of 256 have failed therapy, P less than .001). This difference is significant (P less than .001) after adjustment for leukocyte count, age, and other relevant features. Cases with the t(1;19) also had a worse prognosis than pre-B patients with other translocations (4 of 37 have failed, P less than .01) or with any other karyotypic abnormality (7 of 101 have failed, P less than .001). We conclude that chromosomal translocations confer a worse prognosis for non-T, non-B-cell childhood ALL, and that the t(1;19) is largely responsible for the poor prognosis of the pre-B subgroup.

B-Lymphocytes↗

PubMed1990

Oncogene amplification in pediatric brain tumors.

Despite a considerable amount of information concerning chromosomal and molecular abnormalities found in gliomas in adults, relatively little is known regarding these abnormalities in pediatric brain tumors. We have analyzed DNA from 37 primary brain tumors and 4 tumor-derived cell lines for oncogene amplification. Probes utilized represent 11 known oncogenes (erbB1, gli, neu, myc, L-myc, N-myc, H-ras, K-ras, N-ras, sis, and src). Of 20 primary medulloblastomas studied, only one tumor was found to have erbB1 amplification. In contrast, of the 4 medulloblastoma cell lines studied, 1 had c-myc amplification, 1 had erbB1 amplification, and 1 had amplification of N-myc. Twelve glial brain tumors were analyzed, and only 1 case with amplification of the erbB1 oncogene was found. Other tumors studied include 1 meningioma, 2 ependymomas, 1 anaplastic ependymoma, and 1 cerebral primitive neuroectodermal tumor, none of which had oncogene amplification. These results suggest that oncogene amplification is relatively uncommon in primary medulloblastomas, but the frequency and diversity of oncogene amplification is greater in tumors that can be established as cell lines. The lower frequency of erbB1 amplification in glial brain tumors in children compared to adults is consistent with the generally lower grade of glial tumor histology seen in pediatric patients. However, the case with amplification of the erbB1 oncogene represented 1 of 2 cases of glioblastoma multiforme we studied, which suggests that pediatric glioblastoma multiforme may have a similar frequency of erbB1 oncogene amplification to glioblastomas seen in adults. Our results suggest that oncogene amplification is a relatively uncommon mechanism of oncogene activation in pediatric brain tumors, and they provide molecular evidence for heterogeneity in tumors classified as medulloblastomas.

Blotting, Southern↗

PubMed1990

Development and characterization of pediatric osteosarcoma xenografts.

Of 33 surgical specimens of osteosarcoma obtained from 24 patients, eight were established as transplantable tumor lines in immune-deprived CBA/CaJ inbred mice. Each line retained the histological characteristics of the corresponding primary tumor and produced human lactate dehydrogenase isozymes. Volume doubling times, which ranged from a mean of 12.3 +/- 5.6 to 39.3 +/- 9.8 days, were stable for individual lines over multiple passages. Flow cytometric analysis indicated similar cellular DNA content values in the primary human tumors and established xenograft lines; the presence of two separate stem lines, as in the original tumors, was observed in the laboratory models. Comparison of two methods of immune deprivation indicated that thymectomy, whole-body irradiation, and bone marrow reconstitution was associated with a higher rate of successful engraftment than was thymectomy, 1-beta-D-arabinofuranosylcytosine treatment, and whole-body irradiation. Bone marrow-reconstituted mice also showed less variability in tumor volume doubling time. We conclude that osteosarcoma can be heterotransplanted into bone marrow-reconstituted mice with a relatively high success rate and that the xenografts retain features characteristic of the tumors of origin. The availability of these models should prove useful in the development of new therapeutic regimens and in understanding the biology of osteosarcoma.

Animals↗

PubMed1990

Metalloprotease activity of CD13/aminopeptidase N on the surface of human myeloid cells.

We previously found that the myeloid cell surface glycoprotein CD13 (gp150) is identical to aminopeptidase N (EC 3.4.11.2), a widely distributed membrane-bound, zinc-dependent metalloprotease with an extracellular enzymatic domain that cleaves N-terminal amino acid residues from oligopeptides (J Clin Invest 83:1299, 1989). As a first step toward defining the function of this molecule on myeloid cells, we assessed cell surface-associated N-terminal peptidase activity by sensitive spectrophotometric measurements of the cleavage of p-nitroanilide amino acid derivatives. Aminopeptidase activity detected on the surface of normal and malignant hematopoietic cells coincided with the level of cell surface CD13 expression as measured by flow cytometry. The enzyme was specifically inhibited by the zinc-binding metalloprotease inhibitors, bestatin, 1,10-phenanthroline, or 2.2'-dipyridyl, but was not affected by several inhibitors of other classes of proteases. Aminopeptidase activity was demonstrated for CD13 molecules specifically immunoprecipitated from the surface of CD13-positive cells and was blocked by the metalloprotease inhibitor 1,10-phenanthroline. Moreover, cell surface aminopeptidase activity was partially inhibited when viable cells were incubated with two of a panel of 11 monoclonal antibodies (MoAbs) known to be specific for extracellular epitopes of human CD13. This inhibition was apparent in the absence of detectable downmodulation of CD13 molecules from the cell surface, suggesting that these MoAbs either physically interfere with substrate binding or alter the zinc-coordinating properties of aminopeptidase N molecules. Aminopeptidase N could play an important role in modulating signals generated by peptides at the surface of myeloid cells, either by removing key N-terminal residues from active peptides or by converting inactive peptides to active forms. The inhibitory antibodies used in this study should prove useful in delineating the physiologic roles of CD13/aminopeptidase N on normal and malignant myeloid cells.

Aminopeptidases↗

PubMed1990

Aminopeptidase N is directly sorted to the apical domain in MDCK cells.

In different epithelial cell types, integral membrane proteins appear to follow different sorting pathways to the apical surface. In hepatocytes, several apical proteins were shown to be transported there indirectly via the basolateral membrane, whereas in MDCK cells a direct sorting pathway from the trans-Golgi-network to the apical membrane has been demonstrated. However, different proteins had been studied in these cells. To compare the sorting of a single protein in both systems, we have expressed aminopeptidase N, which already had been shown to be sorted indirectly in hepatocytes, in transfected MDCK cells. As expected, it was predominantly localized to the apical domain of the plasma membrane. By monitoring the appearance of newly synthesized aminopeptidase N at the apical and basolateral surface, it was found to be directly sorted to the apical domain in MDCK cells, indicating that the sorting pathways are indeed cell type-specific.

Aminopeptidases↗

PubMed1990

Allogeneic bone marrow transplantation in a program of intensive sequential chemotherapy for children and young adults with acute nonlymphocytic leukemia in first remission.

Eighty-seven consecutive children and young adults with acute nonlymphocytic leukemia (ANLL) were treated uniformly with induction chemotherapy based on daunorubicin and cytarabine (ara-C), with the addition of etoposide (VP-16) and azacytidine (5-Az) for refractory patients. Of the 65 patients who entered complete remission, 42 were eligible for assessment of response to intensive chemotherapy consisting of four pairs of drugs administered in sequential fashion. Nineteen others with available histocompatibility locus antigen (HLA)-compatible donors were assigned to receive allogeneic bone marrow transplants within 16 weeks from their dates of complete remission. Durations of continuous complete remission (CCR) in the two groups were not significantly different at a median follow-up time of 6 years (P = .30 by log-rank analysis). Kaplan-Meier estimates of CCR probabilities (+/- SE) at 6 years were 43% +/- 13% (transplantation) and 31% +/- 7% (sequential chemotherapy). Postremission failures in the sequential chemotherapy group resulted from bone marrow relapse in 23 of 29 patients (79%), whereas in the transplantation group, failures were equally divided between marrow relapse and transplantation-related complications of graft-versus-host disease (GVHD) or infection due to the immunosuppressive effects of ablative chemotherapy. Comparison of hematologic remission curves indicated a significant advantage for marrow transplantation in terms of systemic leukemia control (P = .06). Thus, in programs of intensive chemotherapy of the type described here, allogeneic marrow transplantation should be seriously considered as alternative therapy for patients in first remission who have an HLA-matched sibling donor, provided that effective methods for control of transplant-related complications are available.

Adolescent↗