Chromosome #14 markers in two Epstein-Barr virus (EBV)-transformed lymphoblastoid cell lines of normal origin differ from the Burkitt lymphoma (BL)-associated 14q+ marker

Epstein-Barr virus-transformed pro-B cells are prone to illegitimate recombination between the switch region of the mu chain gene and other chromosomes

Six independently maintained sublines of FLEB 14, a fetal-liver-derived Epstein-Barr virus-transformed pro-B cell line that has not yet rearranged its immunoglobulin genes, were examined after in vitro propagation during 19-36 months. Two lines showed no immunoglobulin heavy chain gene rearrangement, whereas one allele was rearranged with breakpoints inside the switch region of the mu chain gene in the remaining four. These rearrangements had been generated by the translocation of different chromosome fragments to the immunoglobulin heavy chain gene cluster-carrying 14q32 band in each of the four lines. Previously, a similar rearrangement was found in a fifth subline concurrently with a reciprocal 6;14 translocation. The transposed pieces have been derived from chromosomes 16 and 18 in two of the more recently rearranged lines. Their origins could not be determined in the remaining two lines, but they were different from each other and the other three 14q+ markers. The 14q+ marker-carrying variant has replaced its diploid progenitor suggesting that the translocation has conveyed some in vitro growth advantage on its carrier. This was also supported by the duplication of the 14q+ marker and the loss of its normal chromosome 14 homologue in one subline during serial culturing. The vulnerability of the switch region of the mu chain gene to illegitimate recombination at the pro-B stage and the possible relevance of this finding for the origin of the Burkitt lymphoma-associated 8;14 (immunoglobulin heavy chain gene cluster/MYC) translocation is discussed.

Molecular characterization of novel reciprocal translocation t(6;14) in an Epstein-Barr virus-transformed B cell precursor

An in vitro culture of FLEB14 cells, an Epstein-Barr virus-transformed B cell precursor containing the germ line immunoglobulin genes, gave rise to a uniclonally expanded variant, FLEB14 delta 3, which was rearranged at the immunoglobulin heavy-chain gene locus. Cytogenetic analysis showed that FLEB14 delta 3 had a novel reciprocal translocation, t(6;14)(q15;q32). Molecular cloning of the rearranged DNA fragments and determination of their nucleotide sequence revealed that the recombination event was reciprocal, imprecise, and nonhomologous and took place in the S mu region, like those found in Burkitt's lymphoma cells. We propose a molecular model to explain this genetic event which may be relevant to class switch recombination. The translocated sequence of chromosome 6 did not contain any known oncogenes, although the sequence is conserved among mammals. FLEB14 delta 3 did not show tumorigenicity.

Molecular characterization of novel reciprocal translocation t(6;14) in an Epstein-Barr virus-transformed B cell precursor

An in vitro culture of FLEB14 cells, an Epstein-Barr virus-transformed B cell precursor containing the germ line immunoglobulin genes, gave rise to a uniclonally expanded variant, FLEB14 delta 3, which was rearranged at the immunoglobulin heavy-chain gene locus. Cytogenetic analysis showed that FLEB14 delta 3 had a novel reciprocal translocation, t(6;14)(q15;q32). Molecular cloning of the rearranged DNA fragments and determination of their nucleotide sequence revealed that the recombination event was reciprocal, imprecise, and nonhomologous and took place in the S mu region, like those found in Burkitt's lymphoma cells. We propose a molecular model to explain this genetic event which may be relevant to class switch recombination. The translocated sequence of chromosome 6 did not contain any known oncogenes, although the sequence is conserved among mammals. FLEB14 delta 3 did not show tumorigenicity.

Chromosome 14 marker appearance in a human B lymphoblastoid cell line of nonmalignant origin

A human B cell lymphoblastoid cell line of nonmalignant origin, derived 16 years ago, now carries a 14q+ marker chromosome in 100% of the cells analyzed. This marker was not apparent in karyotypes prepared 1 year after establishment of the line and, thus, presumably arose in culture. The cell line now grows more rapidly than typical B cell cultures and has an unusually high cloning efficiency (60%-90%). Using Southern blot hybridization, we have analyzed the arrangement of 13 onc genes that are often associated with human malignancy, including c-myc. None of these onc genes appear to be rearranged in this cell line.

Chromosome aberrations in peripheral lymphocytes of male homosexuals

Karyotypes of peripheral lymphocytes of 19 male homosexuals showed increased hypodiploidy. Chromosomes #19 and #20 were most frequently lost. Also, structural chromosome aberrations frequently occurred consisting chiefly of translocations and simple chromosome breaks. Terminal deletions, inversions, and isochromosomes occurred less commonly. In three of the cases, 100% of the cells were involved in a pericentric inversion of a chromosome #9. Chromosomes #3 in p21.1 and 1 in p32.3 were repeatedly affected. Structural aberrations were seen less frequently in men with acquired immunodeficiency syndrome(AIDS) and AIDS-related complex than in asymptomatic homosexuals. The hypodiploidy with preferential loss of chromosomes was constantly present. The marker chromosomes and simple breaks at repeated sites are another manifestation of damage to the immune system in these male homosexuals from Greenwich Village in New York City. The chromosomal damage was potentially the result of exposure to amyl and butyl nitrites, viral infections, or immunologic reactions to sperm, which crossreact with lymphocytes.

Morphologic, immunologic, enzymehistochemical and chromosomal analysis of a cell line derived from Hodgkin's disease. Evidence for a B-cell origin of Sternberg-Reed cells

Cell lines derived from Hodgkin's disease may provide a clue to the nature of Sternberg-Reed cells. In the current study, the establishment of an Epstein-Barr-virus-negative lymphoblastoid cell line, derived from the pleural fluid of a patient with the nodular sclerosis type of Hodgkin's disease, is described. The morphologic and immunologic cell marker findings indicate that this cell line is derived from Sternberg-Reed cells. The immunologic findings and a chromosomal analysis are in agreement with a B-lymphocyte origin of these cultured cells. Extrapolation of the results to Hodgkin's disease in vivo would indicate that Hodgkin's disease, like most non-Hodgkin's lymphomas, is the result of B-cell proliferation.