Immortal cell lines were a crucial discovery in biology and have brought forward medical fields in ways we could only have dreamed of 70 years ago. For decades we have known that there’s an issue with them, they can contaminate and take over other samples, which might produce incorrect results. Now researchers from Radboud University have estimated how many published papers have worked on mislabeled cell lines.

According to the study, published in PLOS One, almost 33,000 papers from 1955 to today are likely to feature research on incorrect cell lines. The estimate suggests that these papers could have been cited in half a million other papers. Although this is just a small percentage of the total number of papers in biology, it shows that cell line mislabeling is a serious issue.

"Most scientists don't intentionally publish findings on the wrong cells," lead author Serge Horbach, said in a statement. "It's an honest mistake. The more concerning problem is that the research data is potentially invalid and impossible to reproduce. What's even scarier is that we've known about these wrongly identified cells for half a century, yet many researchers aren't aware of this. New articles are published every week about misidentified cells."

Contamination can happen due to carelessness and often just using multiple cell lines on the same lab workbench might result in issues. Certain cell lines are incredibly tenacious and they take over other cultures given half the chance. So far researchers have found more than 451 cell lines that were completely taken over by other cells.

Another issue is where the cells come from. Cell distribution centers are often semi-privately owned and fear that disclosing such large-scale problems might hurt their reputation or finances. Although contamination is a problem, there are reasonable steps to solve it. Better protocols to avoid cross-contamination like hygienic fume cupboards and genetic testing could make the problem go away. But all of these require time and money.

"The scientists I spoke to said that was the biggest problem," co-author Willem Halffman added. "And to solve that problem, you either have to reduce the pressure to publish or require all researchers to carry out a genetic test before working with the cells."

"It's not our intention to damage anyone's reputation with this publication. It's about the overarching problem: what are we going to do about the mistakes that have been made? That's all we want to determine,” the authors stated.

The most famous cell line is the HeLa, named after Henrietta Lacks who died of cervical cancer in 1951. The cells were removed from her cancer without her knowledge or consent. These cells made the development of a polio vaccine possible, as well as many other medical developments.