COS-7 cells are adherent to glass and plastic in culture. Their permissiveness to lytic growth of SV40 makes them a popular host for transfection with recombinant plasmids. In addition, SV40 has been a heavily researched area for many years as it has potentially been linked with some cancers, including mesothelioma, as well as being an unusually simple virus to manipulate genetically. Along with coding for its capsid proteins, SV40 contains genes for two antigens. One gene, T-antigen (or large T-antigen) is oncogenic, while the other, small t-antigen is not. T-antigen is used to control regulation and packaging of the virus when in simian cells. However, in other cell types it may interfere in cell-growth regulation, causing tumor growth.
COS-7 Cell Line Transfection Protocol
A pre-optimized COS-7 Transfection Kit is available from Altogen Biosystems, which includes:
- COS7 Transfection Reagent (0.5 ml / 1.5 ml / 8.0 ml)
- Transfection Enhancer (0.5 ml), and
- Complex Condenser (0.5 ml)
The kit is a lipid-based transfection reagent that is optimized to transfect miRNA, siRNA or DNA plasmid following either a standard or reverse transfection. The protocol for a 24-well plate to transfect COS-7 cells is here:
- Plate 10,000-15,000 COS& cells per well in 0.5 ml of complete growth medium 12-24 hours prior to transfection
- Wash with 1xPBS and add 0.5 ml of fresh growth medium
- Prepare transfection complexes by mixing 40 µl of serum-free medium, 5 µl of transfection reagent, and (referred to a final volume including growth medium)
- 600 ng DNA 9 (or mRNA), or
- 30 nM – 50 nM of siRNA (or microRNA)
- Incubate transfection complexes at RT for 15-30 minutes
- Optional: Add 2 µl of Complex Condenser. This reagent increases transfection efficiency by reducing the size of transfection complex; however, it may increase cell toxicity
- Add prepared transfection complexes to 0.5 ml of complete growth medium with COS7 cells (from step 2)
- Incubate cells at 37ºC in a humidified CO2 incubator
- Assay for phenotype or target gene expression 48-72 hours after transfection
Optional: Adding transfection Enhancer reagent can increase transfection efficiency. Add 2 µl of Transfection Enhancer reagent 12-24 hours after transfection.
If the viability of COS7 cells being transfected is affected at 16-24 hours post-transfection, changing the growth medium and eliminating redundant exposure of cells to transfectant can reduce the level of cytotoxicity
Research Using COS-7
COS-7 is a popular research tool, and often an excellent choice for transfection experiments using recombinant plasmids. It is used to study the monkey virus SV40, as well as for other transfection experiments aimed at creating novel gene products, such as recombinant proteins. The two COS cell lines used for this type of work are COS-1 and COS-7. In order to use COS cells as a transfection host, a genetic construct preceded by the SV40 promoter is integrated into the cells. Using this strategy, the vector can be replicated by the T-antigen, which controls SV40 DNA replication and virus packaging in COS-7 cells and other simian cells.
The Simian Virus, SV40, is a popular research subject due to simplicity of the genome and ease of manipulation. Its importance also stems from association with certain types of human cancers such as mesothelioma, a cancer of the body lining. This cancer almost always develops as a result of asbestos exposure. SV40 is only 5243 nucleotides long and the DNA is arranged in a closed super helical conformation. Genetic coding for proteins of the virus’ capsid shell, as well as viral regulatory proteins, are encoded with overlapping reading frames, as well as regions coding for the T-antigen (large T-antigen) and t-antigen (small t-antigen). The T-antigen, which facilitates SV40 replication, can become bound to proteins involved in cell growth, resulting in unchecked cell growth. This unchecked cell growth can lead to tumorigenicity.
Links
COS-7 Transfection Reagent (Kidney Cells, CRL-1651)
Research services – ELISA assay development using Cos-7 cells
Transfection. Cells and Molecular Biology Research Methods, Protocols, and Lab Techniques
List of Companies Offering Lab Services
Research studies
- Replication of JC polyomavirus (JCV): JCV persists in the kidney cells post-infection and is also the causative agent of progressive multifocal leukoencephalopathy in humans. The virus itself is ubiquitous and mostly asymptomatic in humans. Scientists studied the virus’ replication in COS-7 cells, which are simian in origin. They found that it replicated efficiently in COS-7 cells, but not in COS cells without T antigen. [LINK]
- Stat5 expression and binding: After identifying the genes to encode Stat5A and Stat5B proteins in human cells, researchers were able to co-express them in COS-7 cells. They were able to identify the molecules required to activate the Stat5 proteins as well as the pathway the Stat 5 proteins followed. [LINK]
- Expression of Adipose differentiation related protein (ADRP): Researchers cloned the gene for a mouse ADRP and inserted it into a plasmid. They were able to transiently transfect the plasmid into CSO-7 cells and investigate its involvement in FA uptake. [LINK]
- Expression of steroidogenic enzymes and metabolism of steroids in COS-7 cells: COS-7 cells are recognized as non-steroidogenic cells because they are derived from the cells of a kidney, a non-steroidogenic organ. This study investigates whether or not COS-7 cells express steroidogenic enzymes and metabolize steroids. Results show evidence that COS-7 express a series of steroidogenic enzyme mRNAS and metabolize a variety of steroids. [LINK]
- Propofol protects COS-7 cell against oxidative-stress-induced apoptosis: Reactive oxygen species production in oxidative stress contributes to cellular dysfunction and initiates apoptosis. This study investigates whether or not propofol preconditioning (PPC) protects against COS-7 cell damage from hydrogen peroxide-induced oxidative stress. Results show that cell viability improved in hydrogen peroxide groups with PPC. Overall, PPC effectively protected COS-7 against apoptosis by inducing autophagy. [LINK]
COS-7 Cells I COS-7 Cell Culture Protocol I COS-7 Transfection Information I Get COS-7 Transfection Reagent