Protein expression in relation to the cell cycle of exponentially growing human prostatic epithelial cells

Characterization of functionally active interleukin-18/eGFP fusion protein expression during cell cycle phases in recombinant chicken DF1 Cells

The dependence of foreign gene expression on cell cycle phases in mammalian cells has been described. In this study, a DF1/chIL-18a cell line that stably expresses the fusion protein chIL-18 was constructed and the enhanced green fluorescence protein connected through a (G4 S)3 linker sequence investigated the relationship between cell cycle phases and fusion protein production. DF1/chIL-18a cells (1 × 10(5) ) were inoculated in 60-mm culture dishes containing 5 mL of media to achieve 50%-60% confluence and were cultured in the presence of the cycle-specific inhibitors 10058-F4, aphidicolin, and colchicine for 24 and 48 h. The percentage of cell density and mean fluorescence intensity in each cell cycle phase were assessed using flow cytometry. The inhibitors effectively arrested cell growth. The fusion protein production rate was higher in the S phase than in the G0/G1 and G2/M phases. When cell cycle progression was blocked in the G0/G1, S, and G2/M phases by the addition of 10058-F4, aphidicolin, and colchicine, respectively, the aphidicolin-induced single cells showed higher fusion protein levels than did the 10058-F4- or colchicine-induced phase cells and the uninduced control cells. Although the cells did not proliferate after the drug additions, the amount of total fusion protein accumulated in aphidicolin-treated cells was similar to that in the untreated cultures. Fusion protein is biologically active because it induces IFN-γ production in splenocyte cultures of chicken. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 32:581-591, 2016.

A novel cytostatic process enhances the productivity of Chinese hamster ovary cells

We have established a novel production process which allows up to fourfold higher production of a model secreted protein, the human secreted alkaline phosphatase (SEAP), in Chinese hamster ovary (CHO) cells. A cytostatic production phase is established in which cell proliferation is inhibited or completely abolished. Such a cytostatic production phase is established by overexpression of the tumor suppressor genes p21, p27, or p53175P (a p53 mutant showing specific loss of apoptotic function) under transcriptional control of a tetracycline-repressible promoter (P(hCMV*-1)). In order to minimize complications due to possible clonal variation of selected, stable cell lines, our investigations are based on transiently transfected subpopulations, that have become a useful tool in industrial R&D. These subpopulations have been selected by flow cytometry for the expression of genes encoded on a dicistronic expression vector. These vectors contain a dicistronic expression unit consisting of the genes encoding the green fluorescent protein (GFP) or SEAP, followed by one of the cytostatic genes p21, p27 or p53175P encoded by the second cistron. p21, p27 as well as p53175P block the cell cycle of CHO cells in the G1-phase for a prolonged period. However, these G1-arrested cells remain viable and proliferation proficient upon repression of expression of the cytostatic gene. All three of the cytostatic genes studied provided similar regulation of proliferation, and also similar enhancements in SEAP production, suggesting that higher productivity may be a general and intrinsic feature of G1-phase arrested CHO cells. Overall productivity is most likely enhanced because growth-arrested cells do not need to devote cellular resources to biomass production.

p27Kip1-mediated controlled proliferation technology increases constitutive sICAM production in CHO-DUKX adapted for growth in suspension and serum-free media

We have engineered dihydrofolate reductase-deficient (dhfr(-)) Chinese hamster ovary (CHO)-DUKX B11 cells adapted for growth in serum-free suspension cultures for unlinked muristerone-inducible expression of the cyclin-dependent kinase inhibitor p27Kip1 and constitutive expression of the soluble intercellular adhesion molecule-1 (sICAM), a potent common cold therapeutic. Conditional overexpression of p27Kip1 resulted in a sustained G1-specific growth arrest of transgenic CHO-DUKX associated with up to fivefold-increased specific sICAM productivity. Herein we exemplify the implementation of controlled proliferation technology in a major biopharmaceutical production cell line that is compatible with key requirements for large-scale production procedures, including constitutive transgene expression and anchorage-independent growth in serum-free media.

The role of the cell cycle in determining gene expression and productivity in CHO cells

Understanding the relationships between cell cycle and protein expression is critical to the optimisation of media and environmental conditions for successful commercial operation of animal cell culture processes. Using flow cytometry for the analysis of the early phases of synchronised batch cultures, the dependency of product expression on cell cycle related events has been evaluated in a recombinant CHO cell line. Although the production of recombinant protein is initially found to be cell cycle related, the maximum specific protein productivity is only achieved at a later stage of the exponential phase which also sees a maximum in the intracellular protein concentration. Subsequent work suggests that it is the batch phase/medium composition of cultures which is the major determinant of maximum specific productivity in this cell line. Furthermore the effect of the positive association between S phase and specific productivity is subordinate to the effect of batch phase/medium composition on the specific productivity of batch cultures.

Flow cytometric applications of Sulforhodamine 101 as a fluorescent stain for total cellular protein

In this paper, the use of Sulforhodamine 101 (SR 101; C.I. 14318) as a fluorescent stain for flow cytometric determinations of total cellular protein (TCP) is described. Flow cytometric quantification of TCP fluorescence can provide a valuable analytical parameter for assessing both changes occurring in overall cellular protein content, such as in response to blast transformation, and heterogeneity in cellular size within a specimen, such as a tumor. Very little information is available in the literature pertaining to the use of SR 101 as a protein stain. Like fluorescein isothiocyanate (FITC), SR 101 can be excited at 488 nm; however, it binds ionically and has an emission maximum at 600 nm, which is advantageous in certain staining and filter combinations. In this report, the utility of SR 101 staining is demonstrated using pokeweed mitogen-stimulated lymphocytes and cycloheximide- and dimethylsufloxide-treated cells. Single, two- and three-color flow cytometric applications are possible, using SR 101 in combination with 4',6-diamidino-2-phenylindole (DAPI) and/or FITC.

Analysis of foreign protein overproduction in recombinant CHO cells. Effect of growth kinetics and cell cycle traverse

Intracellular foreign protein (beta-galactosidase) expression in recombinant CHO cell lines in continuous culture was analyzed by developing a mathematical model that includes the effects of metabolic burden and cell cycle dependence of intracellular foreign protein expression. This combined growth kinetic and cell cycle model, assuming S- or G1-phase-dependent expression, was stimulated to predict productivity on a single-cell and culture-volume basis in continuous cultures. In the case of S-phase-dependent expression, the intracellular foreign protein level increases monotonically, but in the case of G1-phase-dependent expression it decreases monotonically with increasing dilution rate. Also, the trends of foreign protein concentration in the culture volume differ significantly between S- and G1-dependent expression kinetics. Thus, the cell cycle dependency of foreign protein expression should be included in process optimization concepts and operating strategies of continuous bioreactors.

Expression of glial fibrillary acidic protein (GFAP) by cultured angiofibroma stroma cells from patients with tuberous sclerosis

Large dendritic cells were cultured from facial angiofibromas of six patients with tuberous sclerosis. The cells were examined immunocytochemically for expression of selected cytoskeletal and non-structural proteins and the results compared with the staining profiles obtained with normal skin fibroblasts and normal glial cells. In similarity to normal glia, the angiofibroma stroma cells expressed glial fibrillary acidic protein (GFAP). Conversely, by analogy to fibroblasts, the abnormal stroma cells produced fibronectin and did not react with the antibody to S-100 protein. By immunogold labelling it was established that GFAP and vimentin were co-localized in intermediate filaments of the angiofibroma cells.

Asymmetric distribution of oncogene products at mitosis

Computer-assisted image analysis was used to demonstrate in exponentially proliferating human tumor cells the uneven postmitotic apportionment of several oncogene-encoded proteins (ras p21; erbB-2 p185; fos p55; myc p62). This observation may provide the explanation for the high degree of heterogeneity of postmitotic cells and the asynchrony in cell cycle traverse of cultured cells.

Modulation of tumour marker CA-125 expression in cultured ovarian carcinoma cells

The aim of this study was to elucidate whether proliferation of ovarian carcinoma cells may affect the biosynthesis and release of CA-125. In a cell culture model the tumour marker CA-125 expression in cytosol, surface membrane, and release into culture medium was studied in six human carcinoma cell lines. Cell cycle analysis of propidium iodide stained nuclei was performed using a fluorescent activated cell sorter. The turnover of CA-125 is very rapid, within 24 h the equivalent amount found in each cell was also released in the supernatant culture medium. A good relation between cytosolic, membrane, and released CA-125 was observed. CA-125 expression was associated predominantly with the G0/G1 phase of the cell cycle and was dependent on cell density. The results presented here demonstrate that factors associated with tumour cell proliferation could influence the CA-125 serum level in ovarian cancer patients.