Follicular lymphoma with t(8;14)(q24;q32): a distinct clinical and molecular subset of t(8;14)-bearing lymphomas.

The presence of the translocation t(8;14)(q24;q32) has not been well described in follicular lymphoma (FL). In a consecutive series of 278 karyotypically abnormal non-Hodgkin's lymphomas (NHL), six patients with FL showing a t(8;14) without a t(14;18)(q32;q21) were identified. They ranged in age from 45 to 73 years.

B cell lymphoma-associated chromosomal translocation involves candidate oncogene lyt-10, homologous to NF-kappa B p50.

A B cell lymphoma-associated chromosomal translocation, t(10;14)(q24;q32), juxtaposes the immunoglobulin C alpha 1 locus to a novel gene, lyt-10. The normal lyt-10 cDNA codes for a 98 kd protein which displays amino-terminal homology with the rel (DNA-binding) domain of the NF-kappa B-rel family of transcription factors and carboxy-terminal homology with the NF-kappa B p50 precursor protein, including the putative proteolytic cleavage domain (poly-G) and the ankyrin-like repeat domains. The lyt-10 protein can bind to kappa B sequences in vitro, although with different specificity from NF-kappa B p50, and in vitro DNA-binding is activated by removal of the ankyrin domain.

Loss of amplification and appearance of a novel translocation site of the c-myc oncogene in HL-60 leukemia cells.

The chromosomal localization of c-myc sequences was determined by in situ hybridization in HL-60 cells (HL-60a) which contain an amplified c-myc locus and in an HL-60 subline (T-HL60) which has lost the amplification and has proportionately lower levels of c-myc RNA. While in HL-60a cells amplified c-myc sequences were found on the M3q+ marker chromosome, in T-HL60 cells one or few residual c-myc copies were found on a novel 4q+ marker chromosome. Comparative phenotypic analysis of HL-60a and T-HL60 cells show that the decrease in c-myc amplification/expression is not accompanied by changes in the malignant phenotype, namely in doubling time and clonogenic capability in semi-solid media.

The ltk gene encodes a novel receptor-type protein tyrosine kinase.

Previously, analysis of cDNAs encoding the ltk tyrosine kinase suggested that the structure of this protein was unique among tyrosine kinases, containing a transmembrane domain but only a short, or virtually non-existent, extracellular domain. Further, it was suggested that translational initiation might occur predominantly at a CTG codon. We have now cloned and sequenced a putative full length human ltk cDNA which contains novel sequence information relative to previously identified cDNAs.

p53 mutations in human lymphoid malignancies: association with Burkitt lymphoma and chronic lymphocytic leukemia.

We have investigated the frequency of p53 mutations in B- and T-cell human lymphoid malignancies, including acute lymphoblastic leukemia, the major subtypes of non-Hodgkin lymphoma, and chronic lymphocytic leukemia. p53 exons 5-9 were studied by using genomic DNA from 197 primary tumors and 27 cell lines by single-strand conformation polymorphism analysis and by direct sequencing of PCR-amplified fragments. Mutations were found associated with (i) Burkitt lymphoma (9/27 biopsies; 17/27 cell lines) and its leukemic counterpart L3-type B-cell acute lymphoblastic leukemia (5/9), both of which also carry activated c-myc oncogenes, and (ii) B-cell chronic lymphocytic leukemia (6/40) and, in particular, its stage of progression known as Richter's transformation (3/7).

Patterns of chromosomal breakpoint locations in Burkitt's lymphoma: relevance to geography and Epstein-Barr virus association.

We have examined, by Southern blotting, the patterns of chromosomal breakpoint locations in 55 cases of Burkitt's lymphoma (BL) with respect to geography and Epstein-Barr virus (EBV) association. We have confirmed the association between chromosome 8 breakpoint and geography: 74% of endemic (eBL) but only 9% of sporadic BL (sBL) had breakpoints outside the HindIII fragment encompassing the c-myc gene (P2 less than .00001).

Epstein-Barr virus infection precedes clonal expansion in Burkitt's and acquired immunodeficiency syndrome-associated lymphoma.

The Epstein-Barr virus (EBV) is associated with distinct forms of human lymphoid malignancies, including the endemic (eBL) and sporadic forms of Burkitt's lymphoma (sBL) and acquired immunodeficiency syndrome-associated non-Hodgkin lymphoma (AIDS-NHL). However, whether EBV has a pathogenetic role in these tumors or is a passenger virus has not been conclusively demonstrated. One element to distinguish between these two possibilities is to determine whether EBV infection has preceded and, thus, possibly contributed to clonal expansion, or whether infection has occurred after clonal expansion and thus is unlikely to contribute to pathogenesis.

Negative autoregulation of c-myc gene expression is inactivated in transformed cells.

Negative feedback regulation of c-myc gene expression has been observed in some, but not all, cell types. In order to demonstrate conclusively the existence of this mechanism and gain insight into the cause of its inactivation, we have directly examined its function in B cells and then investigated its activity in a number of cell types. We demonstrate the existence of negative c-myc autoregulation by showing the rapid, dose dependent and reversible suppression of endogenous c-myc expression in EBV-immortalized B lymphoblastoid cells transfected with a c-myc gene expressed under the control of a heavy metal inducible promoter.

Down-regulation of LFA-1 adhesion receptors by C-myc oncogene in human B lymphoblastoid cells.

The function of the c-myc gene and its role in tumorigenesis are poorly understood. In order to elucidate the role of c-myc oncogene activation in B cell malignancy, the phenotypic changes caused by the expression of c-myc oncogenes in human B lymphoblastoid cells immortalized by Epstein-Barr virus were analyzed. C-myc oncogenes caused the down-regulation of lymphocyte function-associated antigen-1 (LFA-1) adhesion molecules (alpha L/beta 2 integrin) and loss of homotypic B cell adhesion in vitro.

tyk2, prototype of a novel class of non-receptor tyrosine kinase genes.

We previously identified a novel protein tyrosine kinase gene, tyk2, by screening a human lymphoid cDNA library with a tyrosine kinase domain specific c-fms restriction fragment under low stringency hybridization conditions. We have now isolated and sequenced a full length tyk2 cDNA clone; demonstrated that this gene is widely expressed in hematopoietic and non-hematopoietic cell lines; and mapped it to chromosome 19p13.2.

Identification and chromosomal mapping of new human tyrosine kinase genes.

To identify novel protein tyrosine kinase (PTK) genes expressed in human lymphoid cells, we have screened B- and T-cell cDNA libraries at low stringency using a c-fms tyrosine kinase domain probe. Three new PTK genes were identified, based on the presence of conserved amino acid sequence motifs characteristic of the catalytic domain of tyrosine kinases. Of these three genes, one (tyk1) appears to be the human homologue of a previously cloned murine gene (ltk), which has been reported to encode a tyrosine kinase with a unique structure; while the second gene, tyk2 cannot be clearly assigned to any of the known PTK subfamilies, and therefore may be the prototype of a new PTK gene subfamily.

Ras oncogene mutation in multiple myeloma.

The frequency of ras (H-, K-, and N-ras) and c-myc oncogenes was investigated in multiple myeloma (MM). By means of the polymerase chain reaction (PCR)/oligonucleotide hybridization method, DNA from 56 tumor biopsies was analyzed for the presence of activating mutations involving codons 12 and 61 of the H-, K-, and N-ras genes and codon 13 of the N-ras gene. Mutations, involving the N- or K-ras genes, were detected in 18 of 56 (32%) cases of which 12/43 (27%) were at diagnosis and 6/13 (46%) were after treatment.

Growth- and tumor-promoting effects of deregulated BCL2 in human B-lymphoblastoid cells.

Human follicular B-cell lymphomas possess a t(14;18) that translocates a putative protooncogene, BCL2, into the immunoglobulin heavy chain locus. The normal BCL2 gene is quiescent in resting B cells, expressed in proliferating, but down-regulated in differentiated B cells. Inappropriately high levels of BCL2-immunoglobulin chimeric RNA are present in t(14;18) lymphomas for their mature B-cell stage.

Minimal residual disease in acute lymphoblastic leukemia detected by immune selection and gene rearrangement analysis.

We have developed an assay for the detection of malignant residual cells in the bone marrow from patients with B- or T-lineage acute lymphoblastic leukemia (ALL) in clinical remission. This assay involves an immune selection step followed by immunoglobulin or T-cell receptor gene rearrangement analysis and allows the detection of one contaminating tumor cell out of 1,000 normal bone marrow cells. We have examined the bone marrow of 11 patients with adult ALL in remission over a 24-month period.

Molecular genetic analysis of three AIDS-associated neoplasms of uncertain lineage demonstrates their B-cell derivation and the possible pathogenetic role of the Epstein-Barr virus.

Each of three individuals with acquired immunodeficiency syndrome (AIDS) developed a pleomorphic malignant neoplasm in which a precise histopathologic diagnosis could not be rendered. In each case, the tumor cells expressed leukocyte common antigen and a variable constellation of antigens associated with B- and T-cell activation (HLA-DR, T9, T10, BL2, BL3, Ki-24, BLAST-2). They lacked all B cell, T cell, myeloid, and monocyte lineage-restricted antigens, resulting in their classification as hematopoietic neoplasms of uncertain lineage.

Transformation and plasmacytoid differentiation of EBV-infected human B lymphoblasts by ras oncogenes.

The biological effects of ras oncogene activation in B cells were studied by using amphotropic retroviral vectors to introduce H- or N-ras oncogenes into human B lymphoblasts immortalized by Epstein-Barr virus. Expression of both H- and N-ras oncogenes led to malignant transformation of these cells, as shown by clonogenicity in semisolid media and tumorigenicity in immunodeficient mice. In addition, terminal differentiation into plasma cells was detectable as specific changes in morphology, immunoglobulin secretion, and cell surface antigen expression.

Detection of occult leukemic cells in the autologous bone marrow graft of a patient with T-cell acute lymphoblastic leukemia by a highly specific and sensitive assay.

A patient with T-cell acute lymphoblastic leukemia (T-ALL) in second remission was treated with high doses of chemotherapy and radiotherapy, followed by transplantation of autologous bone marrow purged ex-vivo with an anti-CD5-saporin immunotoxin (OKT1-SAP). Prior to transplantation the bone marrow graft had been considered in complete remission, as assessed by morphology and immunophenotyping. Twenty-two days after transplantation, the disease relapsed in the bone marrow with the same phenotype as at the onset.

Analysis of RAS oncogene mutations in human lymphoid malignancies.

We investigated the frequency of mutations activating RAS oncogenes in human lymphoid malignancies, including B- and T-cell-derived acute lymphoblastic leukemia, chronic lymphocytic leukemia, and non-Hodgkin lymphoma. By the polymerase chain reaction/oligonucleotide hybridization method, DNA from 178 cases was analyzed for activating mutations involving codons 12 and 61 of the HRAS, KRAS and NRAS genes and codon 13 of the NRAS gene. Mutations involving codons 12 or 13 of the NRAS gene were detected in 6 of 33 cases of acute lymphoblastic leukemia (6/33, 18%), whereas no mutations were found in non-Hodgkin lymphoma or chronic lymphocytic leukemia.