It’s all too easy to mix up cell lines, so we see plenty of retractions for that reason — and, according to an expert in the area, many more cases lurk uncorrected in the literature.
The retraction notice for “Knockdown of tumor protein D52-like 2 induces cell growth inhibition and apoptosis in oral squamous cell carcinoma” in Cell Biology International explains the authors’ perspective on this case:
The above article, published online on 13 October 2014 in Wiley Online Library (http://onlinelibrary.wiley.com/doi/10.1002/cbin.10388/abstract), has been retracted by agreement between the authors, the journal Editor, Sergio Schenkman, and John Wiley & Sons Ltd. The retraction has been agreed because the authors discovered after publication that one of the cell lines described in the article had been unintentionally misidentified. The experiments described in the article as being conducted on Human Oral Squamous Cell Carcinoma cell line KB were in fact conducted on a Human Oral Epidermal-like Cancer cell line.
The authors and publisher apologise for any inconvenience.
The paper has not been cited, according to Thomson Reuters Web of Science.
KB is not an OSCC cell line – KB cells are actually HeLa, from cervical adenocarcinoma. Cross-contamination of KB was discovered by Stanley Gartler back in 1967. Unfortunately, KB is still widely used as a model for oral cancer. Cross-contaminated cell lines are extensively used in the scientific literature, with many scientists not aware of this important problem.
A list of cross-contaminated or otherwise misidentified cell lines can be found at http://iclac.org/databases/cross-contaminations/.
She also posted a comment on the retraction notice, noting why she believes the authors were using HeLa cells:
More than 600 articles have been published from 2000 to 2015 that refer to the KB cell line as “oral” or “epidermoid” (squamous cell carcinoma), when it is actually HeLa and thus derived from cervical adenocarcinoma. This is the first time I have seen a retraction or correction published in response. I would like to acknowledge the authors, editor Sergio Schenkman and publisher John Wiley & Sons Ltd for their integrity in correcting the scientific record.
In the comment, she explains why she believes some of the wording in the retraction notice is misleading:
The comment that KB is a “Human Oral Epidermal-like Cancer cell line” may cause confusion. More than 50 years of testing, starting with the work of Stanley Gartler in the 1960s, shows that KB is derived from HeLa. HeLa has been extensively described and we can be confident that it is cervical carcinoma. In the early stages of cross-contamination a mixed culture can occur, in which the original cells are present alongside the contaminating cells, resulting in a mixed phenotype. Typically this only lasts for a few passages; the faster growing culture will rapidly overgrow and replace the other population (Nims et al, 1998, PMID 9542633). Where HeLa is the contaminant it will typically outcompete other cell types, due to its higher rate of proliferation and resilience at low density. There is no evidence that KB is currently a mixed culture, or that it retains any characteristics from the original culture that were present before cross-contamination occurred.
The editor of the journal, Sergio Schenkman, told us he didn’t have more information on how the authors reached the conclusion that they were working with a Human Oral Epidermal-like Cancer (rather than HeLa):
As a Journal Editor, I’m not in a position to ask for a proof for a retraction.
Capes-Davis told us she,
came across this paper while doing a routine search for journal articles that use the KB cell line. I track usage of KB to try and understand how misidentified cell lines continue to be used in the literature.
The authors could have prevented the mistake, Capes-Davis added:
To detect misidentified cell lines, researchers need to do authentication testing. This involves comparing a DNA profile from their sample to others from the same person. All samples from the same person should have corresponding DNA profiles. If other samples from that donor are not available, researchers can compare to online databases that contain data from commonly used cell lines such as HeLa.
We have reached out to authors Fengshan Chen, Sihui Chen, and Ying Cai, affiliated with Tongji University in China. We could not find contact info for first author Yongchun He.
Hat tip: Rolf Degen
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