Expression of the N-ras oncogene in tumorigenic and non-tumorigenic HT 1080 fibrosarcoma X normal human fibroblast hybrid cells.
Explore the source record for details and available documents.
Animals↗
Biomedical subjects
B E Weissman
Publications and source records attributed to B E Weissman.
Tumorigenicity of human HT1080 fibrosarcoma X normal fibroblast hybrids: chromosome dosage dependency.
The tumorigenic capacity of hybrids formed by fusion of the highly tumorigenic HT1080 human fibrosarcoma cell line with nontumorigenic normal fibroblasts was examined. The HT1080 also contains an activated N-ras oncogene. Near-tetraploid hybrids which contained an approximately complete chromosomal complement from both parental cells were nontumorigenic when 1 X 10(7) cells were injected s.c. into athymic (nude) mice, whereas the parental HT1080 cells produced tumors in 100% of the animals with no latency period following injection of 2 X 10(6) cells. Tumorigenic variants were obtained from these hybrids which had lost only a few chromosomes compared to cells from the nontumorigenic mass cultures. In addition, several near-hexaploid hybrids were obtained which contained approximately a double chromosomal complement from the HT1080 parental line and a single chromosomal complement from the normal fibroblasts. All of these near-hexaploid hybrids produce tumors in 100% of nude mice with no latency period. Our results indicate that tumorigenicity of these particular human malignant cells of mesenchymal origin can be suppressed when fused with normal diploid fibroblasts. In addition, the results suggest that tumorigenicity in this system is chromosomal dosage dependent, since a diploid chromosomal complement from normal fibroblasts is capable of suppressing the tumorigenicity of a near-diploid but not a near-tetraploid chromosomal complement from the tumorigenic HT1080 parent. Finally, the loss of chromosome 1 (the chromosome to which the N-ras oncogene has been assigned) as well as chromosome 4 was correlated with the reappearance of tumorigenicity in the rare variant populations from otherwise nontumorigenic near-tetraploid hybrid cultures. Our results also suggest the possibility that tumorigenicity in these hybrids may be a gene dosage effect involving the number of activated N-ras genes in the hybrids compared to the gene(s) controlling the suppression of the activated N-ras genes.
Cell Fusion↗
BALB and Kirsten murine sarcoma viruses alter growth and differentiation of EGF-dependent balb/c mouse epidermal keratinocyte lines.
Clonal BALB/c mouse epidermal keratinocyte (BALB/MK) cell lines were established in tissue culture. Despite their aneuploid nature, the lines were nontumorigenic, and retained in vitro properties similar to those of primary diploid keratinocytes. These included the constitutive expression of keratin and terminal differentiation in response to a calcium concentration greater than 1.0 mM in the medium. The cells also demonstrated an absolute requirement for nanomolar concentrations of epidermal growth factor (EGF) for their proliferation. BALB or Kirsten murine sarcoma viruses are acute transforming retroviruses, which have been shown to transform fibroblastic and hematopoietic cells. Infection of BALB/MK or its clonal sublines with either virus leads to the rapid acquisition of EGF-independent growth. The cells concomitantly lose their sensitivity to calcium-induced terminal differentiation. Thus these retroviruses can rapidly confer upon epithelial keratinocytes in culture growth properties that resemble those of malignant epidermoid carcinoma cells.
Animals↗
Complexity of control of tumorigenic expression in intraspecies hybrids of human SV40-transformed fibroblasts and normal human fibroblast cell lines.
Somatic cell hybrids between SV40-transformed human fibroblast cells and normal human fibroblasts were isolated and tested for growth in vitro and in athymic nu/nu (nude) mice. All hybrid cells formed by a cross of WI-18/VA-2, a tumorigenic SV40-transformed human fibroblast, with IMR-90 expressed T antigen and grew in the appropriate selective medium. However, tumorigenic potential ranged from completely suppressed to fully expressed in these hybrid cells. In addition, all hybrid cells formed between LNSV, a nontumorigenic SV40-transformed human fibroblast, and IMR-90 were nontumorigenic. Previous studies have shown that the tumorigenic potential of hybrids cells formed between a variety of human tumor cell lines and normal human fibroblasts is completely suppressed. These results imply that the genetic control of tumorigenic expression in virally transformed human cells differs from that seen in spontaneously arising human tumor cells.
Animals↗
Complementation of the tumorigenic phenotype in human cell hybrids.
Several combinations of human tumor cell lines were fused together. Hybrid populations formed from fusions between carcinoma x carcinoma and carcinoma x lymphoblastoid remained highly tumorigenic. However, suppression of tumorigenic potential was seen in carcinoma x sarcoma and carcinoma x melanoma hybrid populations. These results suggest that complementation of the tumorigenic phenotype can occur and that at least 2 different complementation groups may be involved.
Carcinoma↗
Human cell hybrids: analysis of transformation and tumorigenicity.
Intraspecific human-human cell hybrids provide a stable model system with which to investigate the genetic control of transformed and tumorigenic phenotypes. Using this system it has been shown that these phenotypes are under separate genetic control. Furthermore, the tumorigenic phenotype can be complemented by fusion of different tumorigenic cells, resulting in nontumorigenic hybrids. This system also provides information on the control of differentiated function. Molecular cytogenetic techniques should reveal the nature of the chromosomal control of neoplastic transformation.
Animals↗
David Brinkerhoff, M.D., F.A.C.S. 1899-1971.
Explore the source record for details and available documents.
Arizona↗
Chromosome 18 suppresses prostate cancer metastases.
Loss of heterozygosity and allelic imbalance data has shown that there are two distinct regions of loss on chromosome 18q associated with the progression of prostate cancer (CaP). To investigate the functional significance of chromosome 18q loci in CaP, we utilized the technique of microcell-mediated chromosome transfer to introduce an intact chromosome 18 into the human prostate cancer cell line, PC-3. Three of the resulting hybrid lines were compared to the PC-3 cells in vitro and in vivo. The hybrid cell lines, containing an intact copy of the introduced chromosome 18, exhibited a substantial reduction in anchorage-dependent and independent growth in vitro. These hybrid cell lines also made smaller tumors in nude mice following subcutaneous injection compared to PC-3 cells. Because tumor growth was not completely eliminated by introduction of chromosome 18, we assessed the ability of the hybrids to metastasize to bone after intra-cardiac inoculation in a nude mouse model. Mice inoculated with PC-3 hybrids containing intact copies of chromosome 18 had significantly fewer bone metastases and dramatically improved survival compared to PC-3 cells. In addition, the introduction of chromosome 18 significantly reduced tumor burden in extraskeletal sites. This was not because of differences in growth rates because mice bearing hybrids were monitored for metastases over twice as long as mice bearing PC-3 cells. Taken together, these data suggest that chromosome 18 has a functional role in CaP to suppress growth and metastases. Identification of the responsible gene(s) may lead to molecular targets for drug discovery.
Agar↗