Protein synthesis in 3T3 cells stimulated to proliferate at various rates

Discrimination of colon cancer stem cells using noncanonical amino acid

Cancer stem cells (CSCs) may be responsible for tumor recurrence. Metabolic labelling of newly synthesized proteins with non-canonical amino acids allows us to discriminate CSCs in mixed populations due to the quiescent nature of these cells.

Sensitive determination of cell number using the CyQUANT cell proliferation assay

We describe here the development and characterization of the CyQUANT cell proliferation assay, a highly sensitive, fluorescence-based microplate assay for determining numbers of cultured cells. The assay employs CyQUANT GR dye, which produces a large fluorescence enhancement upon binding to cellular nucleic acids that can be measured using standard fluorescein excitation and emission wavelengths. The fluorescence emission of the dye-nucleic acid complexes correlated linearly with cell number over a large range using a wide variety of cell types. Under the recommended assay conditions, standard curves were linear (r(2)>0.995), detecting as few as 10-50 cells and as many as 25,000-50,000 cells with a single dye concentration, depending on cell type. Increasing the dye concentration extended the linear range of the assay to 100,000-250,000 cells. Results of cell proliferation and growth inhibition studies with the assay were similar to those obtained in published studies using other standard assays. CyQUANT assay measurements of serum-stimulated cell proliferation correlated well with measurements made using [3H]-thymidine. Also, the assay was used to analyze cellular DNA or RNA content, with the addition of a nuclease digestion step to the protocol. The assay procedure is simple and convenient, with no wash steps, and is readily amenable to automation.

Level of ribosomal RNA required for stimulation from quiescence increases during cellular aging in vitro of mammalian fibroblasts

We have investigated the relation between cell size in terms of cellular ribosomal RNA (rRNA) content and proliferation of diploid human and rat embryo fibroblasts during their aging in vitro. During phase III of the proliferative lifespan in vitro, cellular rRNA content increases by a factor of nearly 3. For very different regimes of stimulation of quiescent cells, a strict correlation was observed, between the proportion of cells stimulated and cellular rRNA content, resembling a steep threshold curve. During aging in vitro, these characteristic curves exhibit an essentially parallel shift to higher values of cellular rRNA content (to higher 'thresholds'). Upon establishment as a permanent cell line, the relation between proliferation stimulation and cellular rRNA ceases to change with further subculturing. It is suggested that the essence of transformation of fibroblasts with a myc-type of oncogenes is a reduction and stabilizing of the critical rRNA content required for proliferation.