Contaminated Cell Lines are Bad for Your Health

By: Edward Burnett and Liz Penn, European Collection of Cell Culture (ECACC®)
Don Finley, Market Segment Manager, Sigma® Life Science
, Biofiles, Vol. 8, No. 16

For many decades cell lines have been fundamentally important tools in many fields of biomedical research, including cancer research. Over previous decades many billions of dollars have been spent, and many advances made in understanding disease etiology and in the development of treatments and cures. However, there is a problem. It is estimated that between 15–20% of the cell lines used worldwide are either cross contaminated or misidentified.1,2 This means that worldwide many hundreds of millions of dollars spent in the biomedical and healthcare fields may have been wasted in producing false or misleading data. If this statistic is not surprising enough, what may be even more surprising is that the problem of misidentified cell lines has been known for over four decades but is as prevalent as ever. As early as the 1960s Stanley Gartler, using isozyme analysis, showed 18 cell lines of independent origin with the same profile as HeLa, the first immortalized human cell line.3 Over the last decade literature searches have shown there are still over a thousand citations using cell lines such as Chang liver, Hep-2, and KB which have been known to be HeLa contaminants for decades.4

There are a number of robust techniques available to identify cross contaminated or misidentified cell lines. For the detection of interspecies cross contamination, DNA barcoding is becoming the method of choice. This utilizes amplification of a mitochondrial cytochrome c oxidase gene with a set of universal primers, which recognize conserved sequences of thousands of different species. The DNA sequence in between the primers is not highly conserved across different species, so when the PCR product is sequenced the species can be determined from database searches. Currently there are over 50,000 species that can be distinguished using this method (www.barcodinglife.org).

The most robust method for detection of intra-species contamination of human cell lines is Short Tandem Repeat (STR) profiling, also known as DNA fingerprinting. STRs are polymorphic loci in the genome. Each allele occurs in the population at a particular frequency. By amplifying a sufficient number of different alleles and multiplying by the frequency at which each occurs in the population, a unique profile for a DNA sample is obtained.5,6 The Health Protection Agency Culture Collections (HPACC) is one of a number of organizations that supply DNA barcoding and STR profiling services. (http://www.hpacultures.org.uk/services/celllineidentityverification/celllineidentityverification.aspx).

In an attempt to tackle the problem of misidentified cell lines, HPACC is part of a new International Cell Line Authentication Committee (ICLAC). ICLAC comprises a group of international scientists and culture collections with expertise in working with cell lines and experience in dealing with the ongoing issue of misidentified cell lines. The focus of the group is to raise the profile of cell line misidentification and cell line authentication. When a member of the group finds evidence for misidentification in the literature and upon agreement within the group, communication is initiated with the authors and, if necessary, the editors and publishers of the journal involved. The committee is also in conversation with the editors of leading international science journals to engage them to prescribe authentication as part of the requirements for publication. A letter to this effect has already been published in Nature.7 This will help increase the awareness of authentication as part of good cell culture practice and help resolve the cross contamination issue.

Despite the availability of the methods for detecting cell line misidentification, it is evident from the investigations the ICLAC committee has undertaken that new false cells lines continue to be established, without the knowledge of their originators. In a 2011 study, the continuous expansion of a cell line derived from human fetal striatum neural stem cells was reported and an STR profile of the derived cell line was published. However, this profile was not compared to the thousands available on a number of online STR databases (e.g. dsmz.de/services/services-human-and-animal-celllines/ online-str-analysis.html). Comparison would have found the profile matched HeLa cells.

Working with authenticated cell lines is a prerequisite for the generation of robust, reliable, and reproducible data in the biomedical research field. There are proven methods for detecting misidentified cell lines and a number of providers who offer this service. There are also easily accessible list of misidentified cell lines available on a number of websites (hpacultures.org.uk/services/ celllineidentityverification/misidentifiedcelllines.jsp). In addition, use of authenticated cells such as the ECACC lines from Sigma guarantee the right start for critical cell-based biomedical research.

Click here for the complete list of over 1500 cell lines available world-wide.

Materials

     

 Reference

  1. Perkel, J.M., Curing cell lines. Biotechniques, 57(1), 85-90 (2011).
  2. Drexler, H.G. et al., False leukemia-lymphoma cell lines: an update on over 500 cell lines. Leukemia, 17, 416-426 (2003).
  3. Gartler, S.M., Apparent HeLa Cell Contamination of Human Heteroploid Cell Lines. Nature, 217, 750-751 (1968).
  4. Nardone, R.M., Curbing rampant cross-contamination and misidentification of cell lines. Biotechniques, 45, 221-27 (2008).
  5. Butler, J.M., Short tandem repeat typing technologies used in human identity testing. Biotechniques, 43(4) supplement (2007).
  6. Butler, J.M., Genetics and genomics of core short tandem repeat loci used in human identity testing. J. Forensic Sci., 51(2), 253-265 (2006).
  7. Master, J., Cell-line authentication: End the scandal of false cell lines. Nature, 492, 186 (2012).

 

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