Detection of low abundance mRNA of myeloid specific genes in cells of acute and chronic lymphoid leukemias by cRNA hybridization

The hybridization to a complementary RNA (cRNA) probe both in situ and in solution was used to assay tiny amounts of mRNA of the lactoferrin (LF) and myeloperoxidase (MPO) genes in normal bone marrow cells and in acute and chronic lymphoid leukemias. Evidence is reported that this technique is much more sensitive than the standard Northern blot technique. The LF mRNA was detectable in three of seven cases of acute lymphoblastic leukemia (ALL) and in three of seven cases of chronic lymphocytic leukemia (CLL). Four cases of ALL were also positive when tested with the MPO cRNA. It is apparent from these results that myeloid specific mRNA, different from MPO, may be detected in leukemic cells with lymphoid phenotype using a method more sensitive than the Northern blot technique. Whether or not the molecular events observed in these cell populations reflect events physiologically occurring rather than a deregulation of gene expression associated to leukemogenesis remains to be established.

Noncoordinated expression of S6, S11, and S14 ribosomal protein genes in leukemic blast cells

The steady state levels of mRNAs codying for the ribosomal proteins S6, S11, and S14 have been evaluated in quiescent and proliferating human fibroblasts and in resting and proliferating human peripheral blood mononuclear cells. It was found that the amounts of ribosomal protein mRNA are very similar and are not increased by serum or mitogen stimulation. The constitutive expression of these genes appears to be coordinately regulated and it is not modified after protein synthesis inhibition by cycloheximide. The ribosomal protein mRNA was also assayed in 15 different populations of human leukemic blast cells. In these populations the abundance of each ribosomal protein mRNA is remarkably different from the other. The results of our present experiments indicate that the expression of the three ribosomal protein genes undergoes independent noncoordinated changes in the large majority of the leukemic populations studied.

Sinus histiocytosis with massive lymphadenopathy: immunological, cytogenetic and molecular studies

We describe a case of "sinus histiocytosis with massive lymphadenopathy" (SHML) studied by immunohistochemical, cytogenetic and molecular analysis. The immunophenotyping showed that the lymph node histiocytes were strongly positive for the S-100 protein and MoAb LeuM3, OKM5, KP1 and DRC-1; a portion of these cells was also positive for OKT6 and Leu3A, suggesting a possible relationship with the veiled cells, which represent an intermediate step in the pathway from the Langerhans cell to the interdigitating reticulum cell. Cytogenetic analysis showed a normal prevalent clone and a small hypodiploid clone and the molecular study showed no detectable involvement of the c-fms proto-oncogene, which is related to monocyte/macrophages. Unfortunately all these data do not seem sufficient to define the benign or neoplastic nature of the disease. Further investigations, immunophenotypical, cytogenetic and molecular, are needed to elucidate the pathogenesis of the disease, especially for more aggressive cases or for cases with unfavorable evolution.

Ratios between the abundance of messenger RNA and the corresponding protein of two growth-related genes, c-myc and vimentin, in leukemia blast cells

The abundance of the mRNAs of two growth-related genes, vimentin and c-myc, and that of the corresponding proteins have been studied in unstimulated and phytohemagglutinin-stimulated lymphocytes as well as in 18 populations of leukemic blast cells. The quantitative assay was carried out by densitometric scanning of Northern and Western blots. In normal lymphocytes the mRNA and the protein of both genes were almost undetectable. The phytohemagglutinin stimulation led to a sharp increase of the mRNA and the proteins of vimentin and c-myc. The increase was followed by a progressive fall of the gene products. The rate of decrease of the two mRNAs was similar to that of the corresponding proteins. In some leukemic populations very similar amounts of the vimentin protein were accompanied by amounts of the mRNA differing at least 25 times. Not unlikely, very similar amounts of p62c-myc corresponded to mRNA abundances differing at least 16 times. The coordinated biogenesis of both messenger RNAs and proteins, which occurs in mitogen-stimulated lymphocytes, is substituted, in approximately 30% of the leukemic blast cell populations, by molecular events leading to the accumulation of an excess of mRNA.

Extramedullary pleural blast crisis in chronic myelogenous leukemia: cytogenetic and molecular study

Two patients with Ph1-positive chronic myelogenous leukemia with pleural blastic transformation occurring before medullary involvement are presented. The clonal origin of the pleural cells identified as unclassified blasts in 1 patient and as erythroid blasts in the other was confirmed by the presence of the t(9;22) translocation and their clonal evolution by the presence of duplicated Ph1 and additional chromosome alterations. DNA obtained from the pleural blasts and peripheral blood cells of 1 patient showed an identically rearranged bcr configuration, indicating the origin of the pleural blasts from the CML clone and suggesting that this genomic event is not directly linked with the progression of disease.

Philadelphia-positive chronic myelogenous leukemia with typical bcr/abl molecular features and atypical, prolonged survival

Despite the major breakthrough in the knowledge of the molecular events underlying the t(9;22) translocation, still no consistent data have been found on the evolution of Ph1 positive CML from the chronic to the accelerated or blastic phase of the disease. In most patients in fact the bcr/abl rearrangements are identical both in chronic phase and in blast crisis, and overall differences in chronic phase duration, related to different location of breakpoints inside the bcr region, were found to be marginal. We approached this problem by studying the molecular features of the bcr/abl abnormality in rare CML patients with very long, atypical chronic phase. The three patients studied, whose chronic phase duration is 17, 19, and 21 years, respectively, have typical genomic bcr rearrangements, and two of them show, hybridizing Northern blots to c-abl, the 8.5 kb mRNA, as that typically present in CML. It seems that genomic alterations within bcr and abl cannot account, alone, for the duration of the chronic phase of Ph1 positive CML and those quantitative and/or qualitative alterations of the p210 bcr/abl protein, unluckily awkward to prove, might be responsible for the atypical clinical features of these CML long survivors.

T-cell receptor genes expression in B-cell leukaemias

Using Northern-blot analysis we have studied the expression of T-cell receptor (TCR) alpha, beta and gamma chain genes in primary cells obtained from 36 leukaemic patients. Fifteen patients had myeloid leukaemias, two had T-cell leukaemias, and 19 leukaemias corresponding to various stages of B-lymphocyte differentiation. We observed that truncated TCR beta mRNAs were produced in B-cells at relatively high levels even in the absence of detectable gene rearrangements. Ti alpha mRNAs of abnormal size were also frequently found. Such transcripts were not detectable in total RNA extracted from leukaemic myeloid cells. Factors allowing Ti alpha and beta gene transcription must be active in leukaemic pre-B and B cells but not in myeloid cells. Neither B-lineage nor myeloid leukaemias expressed TCR gamma gene at detectable levels.

Cytogenetic and molecular studies in primary myelofibrosis

Cytogenetic and molecular data of three patients affected by primary myelofibrosis with myeloid metaplasia (PMMM) evolving to blastic crisis are reported. The cytogenetic findings were uncommon. The first patient (female) showed an idic(X)(q13) as the sole alteration in chronic phase, with an additional r(7) in 67% of the cells of the blast crisis; the other two patients showed, in blast crisis, a partial trisomy of the long arm of chromosome 1, without translocation, as a unique structural abnormality. These findings confirm the presence of nonrandom, although nonspecific, alterations in PMMM that, in our cases, seem to be related to the multistep progression of the neoplastic process. Molecular investigations have been applied to study the genomic organization and the level of expression of genes such as bcr and calcyclin and c-fms protooncogene possibly involved in the molecular mechanisms underlying cell proliferation in hematopoietic cells. The data obtained are discussed with respect to the myeloproliferative disorder.

Isodicentric X chromosome in myeloproliferative disorders

Two further cases of acquired isodicentric (X)(q13) chromosome in patients with myeloproliferative disorders are reported. One patient had a primary myelofibrosis and the other a chronic myelogenous leukemia. DNA replication study demonstrated that both abnormal X chromosomes were late replicating in all cells examined. The inactive condition of idic(X)(q13) seems to be indicative of a selective advantage for a cell carrying this alteration.

Expression of oncogenes and cell cycle related genes in acute and chronic leukemias

The authors have assayed the level of expression of several cell-cycle related genes in several populations of circulating myeloid leukemic blast cells. The genes explored included oncogenes such as c-myc, c-myb, p53, and cell-cycle-related genes such as vimentin, calcyclin, ornithine decarboxylase (ODC) and histone H3. Particular attention was given to analysis of the relationship existing between the mRNA levels of the histone H3 gene, which is expressed specifically in the S phase of the cell cycle, and the levels of other genes that are expressed in different stages of the G1 phase. Remarkable differences were observed among the different cases indicating that a differential expression of cell-cycle-related genes characterizes many acute leukemias. This differential expression is reflected in an altered ratio among G1-related genes and the H3 histone gene. The large fraction of leukemic cells which does not express histone H3 and therefore is functionally noncycling, shows a heterogeneous pattern of G1-related gene expression. This reflects the inability of most leukemic cells to progress through the G1 phase into the S phase of the cell cycle. This inability represents an abnormality of the cell cycle. It is concluded that the study of the expression of cell-cycle genes and protooncogenes in in understanding how leukemic cells enter a state of proliferation arrest, which appears to occur in a large fraction of leukemic cells.

Prognostic significance of "short-term" effects of chemotherapy on MYC and histone H3 mRNA levels in acute leukemia patients

We have found that administration of chemotherapy alters expression of growth-regulated genes in leukemia blast cells. To determine if such changes might be correlated with therapeutic outcome, we studied steady-state mRNA levels of MYC and histone H3 in the leukemic blasts of patients just prior to and 24 hr after the administration of the first doses of antileukemic drug therapy. Among nine patients with acute myelogenous leukemia, mRNA levels of MYC and histone H3 were reduced in five patients, and hematologic remission was achieved in three of these individuals. No remission was obtained in the four patients without reduction in MYC and histone H3 mRNA. Among acute lymphocytic leukemia patients, the mRNA levels of MYC and/or histone H3 were reduced by the therapy in seven of nine patients. A complete hematologic remission was obtained in five of them, and a partial remission was obtained in the other two. No remission was obtained in the patients in which MYC and H3 mRNA levels were unaffected by the therapy. These studies are of interest because they suggest that a decrease in the mRNA levels of MYC and histone H3 24 hr after a single dose of antineoplastic drugs may predict which patients will achieve complete remission; lack of reduction in these mRNAs correlates with failure to achieve remission. In addition, these studies also provide further proof of the heterogeneity of altered growth regulation among human leukemias.

Philadelphia-positive chronic myeloid leukemia with a chromosome 22 breakpoint outside the breakpoint cluster region

In chronic myelogenous leukemia (CML) the reciprocal translocation resulting in the Philadelphia chromosome (Ph1) leads to the formation of a chimeric transcriptional unit carrying both c-abl and bcr genetic information whose transcript is a new fused mRNA of 8.5-kilobases (kb) and whose translational product is a 210-kD phosphoprotein with tyrosine kinase activity implicated in the pathogenesis of CML. Twenty patients affected by Ph1-positive CML were studied by Southern blot analysis with bcr. Unexpectedly, in three Ph1-positive patients, the breakpoint of chromosome 22 was located neither inside the bcr region nor 5' to it. Northern blot analysis of the RNAs of two of these patients showed the absence of a detectable 8.5-kb chimeric mRNA. In the third patient a chimeric mRNA was detected by a c-abl cDNA probe but failed to hybridize with a bcr cDNA probe and showed very low hybridization levels with further 5' bcr cDNA probes. The possibility is raised that in CML a breakpoint outside bcr might either still allow the formation of a chimeric mRNA, possibly through alternative splicing mechanisms, or might prevent the transcription of the chimera. In the latter case different molecular events resulting in the formation of a Ph1 chromosome may underlie the same myeloid neoplastic phenotype.

Expression of c-myb protooncogene and other cell cycle-related genes in normal and neoplastic human colonic mucosa

The expression of c-myb, c-myc, histone H3, and ornithine decarboxylase genes was examined by Northern blot analysis in the normal and neoplastic mucosa of ten subjects affected by colon cancer. The mRNA levels of c-myb protooncogene were detected at low levels in all normal samples but were increased in the neoplastic mucosa of six cases in comparison to the normal counterpart. In five of these six cases the mRNA levels of c-myc, histone H3, and ornithine decarboxylase mRNAs were also increased, suggesting that there is a relation between the high expression of c-myb and the fraction of cycling neoplastic cells.

Establishment and characterization of a human IgA-kappa-secreting plasma cell line (MT3)

We have established a new human plasma cell line from the peripheral blood of a patient with an IgA-kappa plasma-cell leukemia. Morphological, immunological, cytogenetic and molecular studies confirm that the cultured cells are derived from the same clone of leukemic plasma cell in vivo. The established cell line (MT3) grows in suspension, secretes high amounts of IgA kappa and exhibits morphological and ultrastructural characteristics of plasma cells. Surface marker analysis shows that both primary and cultured cells express the plasma-cell-associated antigens PCA-1 and T10, while specific B- and T-cell determinants and EBV nuclear antigen are undetectable. In the established cell line a few cells express Ia-like and CALLA antigens. Cytogenetic analysis of MT3 cells reveals a prevalent hypertriploid karyotype with constant chromosomal aberrations consisting of 14q+, 22q- and marker chromosomes.

Platelet alpha-granule release in chronic myeloproliferative disorders with thrombocytosis

Platelet alpha-granule release in 22 patients affected by chronic myeloproliferative disorders with thrombocytosis and seven subjects with thrombocytosis secondary to splenectomy were studied. We found elevated beta-thromboglobulin (BTG) and platelet factor 4 (PF4) plasma levels in all patients. Intraplatelet content of BTG and PF4 was decreased in patients with idiopathic thrombocythaemia (IT) and idiopathic myelofibrosis (IMF). The BTG and PF4 results were also expressed as the ratio plasma BTG and PF4: whole blood platelet count. In patients with IT, BTG: whole blood platelet count ratio was low, conversely, the same ratio was high in patients with IMF. In conclusion, our results suggest the presence of an abnormal, BTG-deficient clone in IT and a peripheral platelet activation in IMF.

Cellular levels of mRNA from c-myc, c-myb and c-fes onc-genes in normal myeloid and erythroid precursors of human bone marrow: an in situ hybridization study

The expression of three onc-genes, c-myc, c-myb and c-fes, has been evaluated at the cellular level in myeloid and erythroid precursors of normal human bone marrow, by "in situ" hybridization with tritium-labelled probes. A relatively large amount of m-RNA from the three onc-genes was detected in myeloblasts and promyelocytes, but whereas the expression of c-myc and c-myb decreased in more advanced stage of maturation of the myeloid lineage, c-fes mRNA remained at a relatively high level until the granulocyte stage. c-myc and c-myb were expressed at a fairly high level in basophilic erythroblasts, which also showed low levels of c-fes mRNA. No expression of these onc-genes was detectable in more mature erythroblasts. Megakaryocytes showed high levels of m-RNA from all three onc-genes. Our results suggest that c-myc and c-myb expression is related in some way to the cellular proliferation of myeloid and erythroid precursors, whereas c-fes expression is more restricted to myeloid differentiation.

Differential patterns of expression of cell cycle-related genes in blast cells of acute myeloid leukemia

The expression of two G1-specific clones, p2A9 and p4F1, of two cell cycle-related oncogenes, c-myc and c-myb and of one S phase-specific gene, the H3 histone gene, was explored in 11 cases of acute myeloid leukemia. Both Northern blot analysis and in-situ hybridization were employed. Differential patterns of gene expression were observed. In 6 out of 11 cases a considerable or high expression of the p2A9 and p4F1 clones and of c-myc and c-myb oncogenes was observed. In 2 cases a high expression of c-myc was matched by low or absent expression of the other genes examined. In 3 cases the expression of 2A9, 4F1, c-myc and c-myb was very low or undetectable. In two of these cases a considerable expression of the H3 histone gene was observed.

Activation of c-myb expression by phytohemagglutinin stimulation in normal human T lymphocytes

The expression of c-myb in normal human T lymphocytes directly derived from a normal subject and not adapted to continuous growth in culture was found to be markedly increased after phytohemagglutinin stimulation. In the same cells, the expression of c-myc mRNA is a much earlier event compared with the appearance of c-myb mRNA, which takes place soon after that of histone H3 mRNA. The increase in c-myb expression was not due to a particular T-lymphocyte subset, as shown by in situ hybridization assays.

Study of the levels of expression of two oncogenes, c-myc and c-myb, in acute and chronic leukemias of both lymphoid and myeloid lineage

Total cellular RNA from a series of leukemic cell populations, both myeloid and lymphoid, as well as from normal circulating lymphocytes was analysed for the expression of two cellular oncogenes, c-myc and c-myb, by Northern blot hybridization assay. Expression of c-myc but not of c-myb was observed in unstimulated normal lymphocytes. Stimulation by PHA was shown to activate the expression of both genes. Remarkably different levels of expression of c-myc were observed in ALL, whereas in CLL the expression of c-myc was uniformly low or absent. Differential expression of c-myc was detected in AML as well as in CML, c-myb was differentially expressed in AML and ALL, and absent in CLL and CML. Other single cases of hemopoietic disorders were studied, but the expression of the two oncogenes was low or absent. Neither evident genome amplification nor genome rearrangements were detected in the cell DNAs digested with restriction endonucleases.