Generation of Human Embryonic Kidney Cells with Extended In Vitro Life Span through Viral Oncogene Transfection

Sensitivity of primary cells immortalised by oncogene transfection for the detection and isolation of foot-and-mouth disease and swine vesicular disease viruses

Primary cells derived from calf thyroid (CTY), calf kidney (CK) and piglet kidney (PK) were immortalised by oncogene transfection and their susceptibility to infection by foot-and-mouth disease (FMD) virus and swine vesicular disease (SVD) virus examined. Eighty-five immortalised cell lines (47 CTY, 20 CK and 18 PK) proved stable upon repeated cell culture passage and many supported the growth of FMD virus and several of the PK cell lines supported SVD virus. However, none of the immortalised lines exhibited either the degree of sensitivity or the specificity for all virus serotypes and strains as shown by primary CTY and IB-RS-2 cell cultures which are routinely employed for vesicular virus diagnosis.

Cell lines with extended in vitro growth potential from human renal proximal tubule: characterization, response to inducers, and comparison with established cell lines

Few model systems exist for the study of injury to human renal proximal tubule epithelium. Optimized differentiated human renal epithelial cell lines with extended in vitro growth potential would provide an alternative model system to primary culture or other available non-human mammalian kidney cell lines. For this purpose, human renal tubule epithelial cells were isolated from normal kidney cortex and exposed in culture to a hybrid immortalizing virus, adenovirus 12-SV40. Cell lines were developed by limiting dilution, and three selected cell lines were screened for growth pattern, production of immortalizing virus, tumorigenicity, and ploidy. Cell lines were also monitored for response to inducer agents and matrix factors and were screened for expression of biochemical properties and differentiation markers of renal epithelium. All three are nonproducers of the immortalizing virus and are nontumorigenic. They grow in monolayer, have intermediate growth kinetics, and express markers of renal proximal tubular epithelium by immunohistochemistry. They also express biochemical properties comparable to other widely used proximal tubular cell lines including LLC-RK1, OK, and HK-2 and comparable to human tubular cells in stable culture. Growth medium containing low levels of fetal calf serum, or epidermal growth factor combined with parathyroid hormone, produced optimal growth characteristics, brush border enzyme expression, biochemical properties, and glucose transport in a selected cell line. The addition of dimethyl sulfoxide allows maintenance in morphologically intact monolayers for prolonged periods. These cell lines should be useful model systems for the study of human renal proximal tubular injury or disease.

Endogenous [3H]flunitrazepam binding in human embryonic kidney cell line 293

Specific endogenous [3H]flunitrazepam binding sites were identified and characterized in membranes from the human embryonic kidney (HEK) cell line 293. A large part of these binding sites exhibited an intermediate affinity for [3H]flunitrazepam and a microM affinity for diazepam, clonazepam, 1-(2-chlorophenyl)-N-methyl-N-(1-methylpropyl)-3-isoquinolinecarboxam ide (PK 11195) or 4'-chlorodiazepam (Ro 5-4864). These sites, thus, resembled neither gamma-aminobutyric acidA (GABAA) receptor associated nor 'peripheral' benzodiazepine binding sites. A small part of the binding sites labeled by [3H]flunitrazepam seemed to belong to 'peripheral' benzodiazepine binding sites exhibiting a nM affinity for PK 11195, and another small part of the binding sites seemed to exhibit a high affinity for flunitrazepam and PK 11195. Although small amounts of mRNA for alpha 1-, beta 3- and gamma 2-subunits of GABAA receptors could be identified in HEK 293 cells, neither the actual expression of GABAA receptors in these cells nor a coassembly of endogenous subunits with transfected GABAA receptor subunits could be demonstrated by binding studies.

Expression of SV40 tumour antigens enables human endothelial cells to grow independently from foetal calf serum and exogenous growth factors

Human endothelial cells were transfected with a plasmid containing the coding sequence of the large T protein of simian virus 40. Transfected cells were selected for their ability to grow in defined medium (DM). Several cell lines were derived and characterized in their response to endothelial cell growth supplement (ECGS), epidermal growth factor (EGF) and insulin (INS). In addition to cell lines that were dependent on these additives, others growing without any exogenous growth factor could be selected. No evidence of autocrine growth stimulation was found. For growth studies, a simple assay was used based on the acid phosphatase activity as a parameter for the cell number. Cell lines in defined medium showed less chromosome aberrations than those grown in serum-containing medium. Because of their long in vitro life span of about 100 generation doublings and defined medium requirements these cells represent valuable test material for all kinds of investigations on the vascular endothelium.

A comparative study on the uptake of alpha-aminoisobutyric acid by normal and immortalized human embryonic kidney cells from proximal tubule

We investigated whether an immortalized human kidney epithelial cell line (IHKE), compared with normal embryonic cells (NHKE), can be used as a representative system with which to characterize the transport of neutral amino acids in the proximal tubule of the human kidney. The IHKE cell line, immortalized by treatment with NiSO4, exhibited microvilli and enzyme markers specific for highly specialized tubule cells. The Na(+)-dependent uptake of alpha-aminoisobutyric acid (AIB) by IHKE and NHKE cells occurred by means of a single transport system with identical half-saturation constants, but the capacity for uptake was higher in the immortalized cells. Proton-dependent influx of AIB was also mediated by a single transport component with similar uptake characteristics in both types of cells. Imposition of an H(+)-gradient to a Na(+)-gradient reduced the sodium dependent uptake of AIB with the exception of short incubation time (1 min), where addition of a proton gradient produced a marked increase in the Na(+)-dependent influx of AIB in NHKE but not in IHKE cells. Competition experiments revealed that the Na(+)-dependent uptake at 50 microM AIB was reduced by neutral alpha-amino acids in the two cell lines. L-Glutamate, L-aspartate, L-arginine and the beta-amino acid taurine had no effect. Only in the IHKE cell line did addition of 5 mM L-lysine produce a slight inhibition. Except for L-proline all of the neutral and acidic amino acids tested reduced the H(+)-dependent uptake of AIB in the IHKE cell line. By contrast, addition of L-aspartate did not influence the transport of AIB in NHKE cells. L-Arginine, but not L-lysine decreased the influx in both cell lines. We conclude that the IHKE cell line has retained the capability to accumulate AIB by transport protein(s) similar to those present for neutral alpha-amino acids in NHKE cells.

Influence of transfected SV40 early region on growth and differentiation of human endothelial cells

Endothelial cells isolated from human umbilical veins show a limited in vitro life span of about 40 population doublings. Cell division is dependent on the presence of endothelial cell growth factor in the culture medium. We have transfected primary endothelial cells with a plasmid containing the early region of SV40 virus. Large T positive cells were obtained which grew in the absence of endothelial cell growth factor at low serum concentrations and showed a prolonged lifespan. Expression of von Willebrand factor and SV40 large T antigen was detected simultaneously in transfected cells.

Extension of lifespan of human T lymphocytes by transfection with SV40 large T antigen

Lymphocytes have a finite and predictable proliferative life span in culture similar to that observed in fibroblasts. In general, the senescence of human fibroblasts is inevitable and irreversible, but their proliferative life span can be extended by certain DNA tumor virus oncogenes, such as the large T antigen of the SV40 virus. Here, we show that human T lymphocytes (HTL) can be stably transfected with SV40 large T and that expression of T antigen extended the life span of T cell cultures. PHA-stimulated HTL were transfected with pSV3neo, an expression vector containing the SV40 early region and the neomycin resistance gene. Transfectants were selected for neomycin (G418) resistance. Control HTL, either mock transfected or transfected with pSV2neo (containing the neomycin resistance gene only), ceased proliferation after about 17 population doublings. In contrast, HTL transfected with pSV3neo underwent more than 170 doublings. pSV3neo-transfected cells expressed SV40 large T RNA, detectable by in situ hybridization, and SV40 T antigen, detectable by immunofluorescence. Greater than 95% of the transfected cells were CD4 positive. These results clearly show that SV40 large T enables HTL to escape senescence. Transfection with SV40 large T may be a valuable method for obtaining long term human T cell lines for studies of both aging and immunology.

Defining the molecular mechanisms of human cell immortalization

Although the immortalization of human cells is a key step in oncogenic progression, the molecular mechanisms underlying this event are poorly understood. After reviewing the use of chemicals, physical agents, oncogenes and DNA tumor viruses as immortalizing agents, we consider the importance of negative regulators of cell growth (RB and p53), their inactivation, as well as genomic instability in the pathogenesis of cancer. Finally, a molecular model for human cell immortalization that integrates many of the above observations is presented along with supporting evidence.