Preferential retention of the mink chromosome group in somatic cell hybrids of Chinese hamster and American mink

The chromosomal complement was studied in 57 independent clones of hybrid cells obtained in six experiments for fusion of Chinese hamster and American mink cells. Various mink chromosomes in hybrids of concern are lost. It is shown when a small number of mink chromosomes are retained in hybrid clones, chromosomes 6, 9, 10, 12, 13, 14 and X segregate in a similar way and are preferentially retained in these clones. When a considerable number of mink chromosomes are detained in hybrid clones, the segregation mode is close to a random one.     

Integration of 101 DNA markers across human Xp11 using a panel of somatic cell hybrids

One hundred and one DNA markers previously assigned to the short arm of the human X chromosome were localized on a hybrid mapping panel consisting of ten radiation-reduced, and four classical somatic cell hybrids. Of the 101 DNA markers, 16 are genes, two are pseudogenes, 13 are expressed sequence tags, 32 are simple tandem repeats (STRs), four are restriction fragment length polymorphisms, one is a variable number of tandem repeats, and 33 are sequence tagged sites (STSs). Three of these markers, two STSs and one STR, were generated from the products of an inter-Alu PCR library of a radiation-reduced hybrid containing Xp11.4-->p11.22 as its only human DNA content. A second STR was isolated from a region-specific cosmid containing the gene ZNF21. The 101 DNA markers fell into 22 bins based on their retention on the hybrids of this panel, which, in combination with YAC contig data, could be further resolved into 24 bins. This hybrid map of Xp11 has an average resolution of approximately 0.8 Mb.     

Human somatic cell gene therapy

The prelude to successful human somatic gene therapy, i.e. the efficient transfer and expression of a variety of human genes into target cells, has already been accomplished in several systems. Safe methods have been devised to do this using non-viral and viral vectors. Potentially therapeutic genes have been transferred into many accessible cell types, including hematopoietic cells, hepatocytes and cancer cells, in several different approaches to ex vivo gene therapy. Successful in vivo gene therapy requires improvements in tissue-targeting and new vector design, which are already being sought. Gene-transfer protocols have been approved for human use in inherited diseases, cancer and acquired disorders. Although the results of these trials to date have been somewhat disappointing, human somatic cell gene therapy promises to be an effective addition to the arsenal of approaches to the therapy of many human diseases in the 21st century if not sooner.     

An immunochemical method for the detection of the expression of human gene loci in human-rodent somatic cell hybrids with special reference to the GPI locus

Species-specific antibodies, prepared against unpurified human enzymes in human-hamster somatic cell hybrids. Results of the detection of the expression of the human glucosephosphate isomerase gene locus (GPI) by electrophoretic and immunochemical techniques were concordant in 17 instances. The human GPI synthesized by fibroblasts derived from skin explants and by somatic cell hybrids retaining the human GPI locus, regardless of whether the human parental cells were lymphocytes or fibroblasts, appeared to be antigenically identical.     

Control of expression of differentiated functions in neuroblastoma cell hybrids

Cell hybrids have been extensively utilized for gene mapping; more than 50 enzymes and nonenzyme proteins have been assigned to individual human chromosomes. Hybrids have also been used in the study of differentiation; fusions involving mouse or human neuroblastoma cells and various nonneuronal lines resulted in hybrid cells that continued to express neuronspecific functions. The expression of the differentiated state is, however, not an all-or-none phenomenon: One neuronal trait may be evident in such hybrids, in the absence of others. The potential usefulness of the human neuroblastoma hybrids for the assignment of genes involved in the expression of differentiated functions to specific chromosomes is discussed.     

Stable nontumorigenic phenotype of somatic cell hybrids between malignant Burkitt's lymphoma cells and autologous EBV-immortalized B cells despite induction of chromosomal breakage and loss

Fusion of the highly tumorigenic Burkitt's lymphoma (BL) cell line BL60-P7 with the nontumorigenic autologous EBV-immortalized lymphoblastoid cell line (LCL) IARC 277 results in suppression of the tumorigenic phenotype of the parental cell line BL60-P7 after s.c. inoculation into T cell-deficient nude mice. We analyzed whether, after long-term cultivation of these lymphoma hybrid cells, expression of tumorigenicity could be observed and correlated to the loss of particular chromosomes or chromosomal fragments, akin to numerous nonlymphoid hybrid cell models described previously. Two years after fusion, in vitro proliferation of some BL x LCL hybrid cells accelerated, and they partially lost LCL-typical aggregation. However, no major changes in the expression pattern of B cell-associated surface antigens and the EBV latent membrane protein LMP 1 were observed. Cytogenetic evaluation of these cells revealed spontaneous loss of chromosomes. Karyotyping of long-term cultivated hybrid cells demonstrated the occurrence of disomy for each chromosome in at least one metaphase analyzed. Therefore, if suppression of tumorigenicity in these hybrid cells would have been the result of the presence of a single LCL-derived chromosome, there should have been a high probability of its loss, leading to tumorigenic segregants. Surprisingly, the tumorigenic phenotype remained suppressed in nude mice. To induce chromosomal breakage and maldistribution, in addition to spontaneous chromosomal loss, the hybrid cell lines were irradiated at various doses. Again, none of the hybrid cell clones treated in this manner became tumorigenic in nude mice. Immunohistological analysis of the regressing hybrid cell tumors revealed that the hybrid cells had retained their LCL-like differentiation phenotype in vivo. In addition, infiltration with mononuclear cells of murine origin was observed in these regressing hybrid grafts. We conclude that suppression of the tumorigenic Burkitt's lymphoma phenotype in these hybrid cells cannot be attributed to a function encoded by a distinct chromosome or chromosomal fragment. Rather, the unexpected stable nontumorigenic phenotype reflects a LCL-specific activated B-cell phenotype of these hybrids, most probably induced by the expression of numerous copies of episomal latent EBV proteins.