agar and Chromosome-Deletion

Losses of heterozygosity involving chromosomes 9 and 10 are frequent events in the development and progression of cutaneous malignant melanoma. To investigate whether specifically deleted chromosomal regions encode tumor suppressor genes (TSGs), we introduced normal chromosome 10 into the tumorigenic human metastatic melanoma cell line UACC-903 by microcell fusion. In addition, two chromosome 9 derivatives that were microdeleted in the region of the p16INK4A/p15INK4B locus were transferred to determine whether an additional melanoma TSG or TSGs reside on chromosome 9p, as indicated by previous melanoma allele loss studies. In comparison to parental cells, microcell hybrids generated with chromosomes 9 (microdeleted) and 10 displayed reduced anchorage-independent growth in soft agar and markedly reduced tumorigenicity in athymic (nu/nu) mice. These data define a TSG or TSGs that function independently of p15/p16 on chromosome 9 and provide evidence for a TSG (or TSGs) on chromosome 10 that may be important in melanoma development.

Topics: Agar; Animals; Carrier Proteins; Cell Cycle Proteins; Cell Division; Chromosome Deletion; Chromosome Mapping; Chromosomes, Human, Pair 10; Chromosomes, Human, Pair 9; Cloning, Molecular; Cyclin-Dependent Kinase Inhibitor p15; Cyclin-Dependent Kinase Inhibitor p16; Female; Genes, p16; Genes, Tumor Suppressor; Humans; Melanoma; Mice; Mice, Nude; Neoplastic Stem Cells; Phenotype; Skin Neoplasms; Tumor Cells, Cultured; Tumor Suppressor Proteins

We studied the migration through semisolid agar of chemotactic and nonchemotactic cells of Escherichia coli. While swarms of nonchemotactic cells were generally smaller than those of chemotactic cells, they varied markedly in size and in structure. Cells that failed to tumble or that tumbled incessantly formed the smallest swarms. Cells that tumbled at intermediate frequencies formed much larger swarms, even when deleted for many of the genes known to be required for chemotaxis. Surprisingly, the higher the tumble frequency, the larger the swarms. Microscopic examination revealed that tumbles enable cells to back away from obstructions in the agar. Thus, not all cells that swarm effectively need be chemotactic.

Topics: Agar; Cell Movement; Chemotaxis; Chromosome Deletion; Escherichia coli; Genes, Bacterial; Genotype; Kinetics; Species Specificity; Time Factors

Thymidine kinase-deficient syrian hamster cells were cotransfected with recombinant plasmids containing the thymidine kinase (TK) gene of Herpes Simplex Virus Type 1, and either intact or partially deleted SV40 T antigen-coding genes. The transformants were selected by their ability to grow in gHAT medium. After selection and cloning, the TK-positive transformants that also expressed T antigen were tested for the extent of their transformation with respect to a number of characteristics, which included saturation density, ability to grow in soft agar, resistance to butyrate and to dibutyryl-cAMP, and plating efficiency. The combined results of these various tests indicate that cells containing partially deleted SV40 T antigen-coding genes are less transformed than cells containing an intact SV40 T antigen-coding gene. However, the amounts of T antigen are lower in cells transformed by deletion mutants than in cells transformed by wild-type T antigen-coding gene. Our data indicate that both the quantity and the quality of T antigen may be important in determining the degree of transformation in Syrian hamster cells.

Topics: Agar; Animals; Antigens, Viral, Tumor; Bucladesine; Butyrates; Butyric Acid; Cell Count; Cell Division; Cell Line; Cell Transformation, Viral; Chromosome Deletion; Cricetinae; Culture Media; Genes, Viral; Mesocricetus; Mutation; Simian virus 40; Transfection