Atypical pattern of light chain gene rearrangement in hairy cell leukemia.

Molecular genetic analysis was exploited to determine the lineage of the neoplastic cells in nine patients affected by hairy cell leukemia (HCL). In all cases the B-lineage of the cells was confirmed at the molecular level. In four cases a relatively advanced maturation stage was suggested by the expression of lambda light chain genes. Surprisingly, in two patients lambda light chain gene rearrangement was observed in spite of a germ-line kappa light chain gene. In at least one case the rearrangement was productive, as a full length messenger RNA (mRNA) was shown by Northern blot analysis and lambda light chain-restricted surface immunoglobulins (sIg) were found. These data suggest that exceptions to the hierarchy that regulates light chain gene rearrangements are not uncommon in this type of leukemia and that molecular genetic analysis should include lambda gene locus to determine more precisely the lineage origin of some leukemic cell populations.

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.

[Expression of immunoglobulin genes and T lymphocyte antigen receptors in a case of acute lymphatic leukemia]. / Espressione dei geni delle immunoglobuline e del recettore antigenico T-linfocitario in un caso di leucemia linfatica acuta.

Molecular genetic analysis was performed on DNA extracted from blast cells of a patient with acute lymphoblastic leukemia. While k light chain genes were in a germ line configuration rearranged bands were found using both JH and TCR beta probes, thus making a lineage diagnosis uncertain. Northern blot analysis showed that both mu heavy chain and TCR beta chain genes were transcribed in blast cells; TCR beta gene, however, gave a truncated transcript whereas Ig heavy chain gene cluster produced a full length mu mRNA. These data show that the accuracy of lineage diagnosis can be improved if expression studies are performed in association with molecular genetic analysis.

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.

Simultaneously increased expression of the c-myc and mu chain genes in the acute blastic transformation of a chronic lymphocytic leukaemia.

A B-cell chronic lymphocytic leukaemia terminated, 5 years from the onset, with a blast crisis. Karyotype analysis showed that the terminal lymphoblastic population evolved from the original B lymphocytic clone. The levels of expression of several oncogenes, as well as the mu chain gene, were assayed by Northern blot hybridization analysis of RNA extracted from the lymphoid populations before and after the 'acute transformation'. A seven- to eight-fold increase in the expression of c-myc and mu chain genes was observed in the blast population. c-myb, c-fes, c-Haras were not expressed either before or after the blastic transformation.

[Atrial dissociation in complete intra-atrial block]. / Dissociazione atriale da blocco intra-atriale completo.

Atrial dissociation due to a complete intraatrial block is a very rare electrocardiographic occurrence. Two cases of this atrial arrhythmia characterized by two atrial ectopic beats of different origin are reported. The electrophysiologic mechanisms of the arrhythmia are discussed briefly.