Everyone knows as a scientist your expected to be busy asking questions and challenging assumptions.However this is to some degree unfeasible,you cant distrust everything or it will take a very long time to get any work done!Thus some things just have to be taken at face value.However,some researchers got a shock recently when it was announced that three frequently used human esophageal adenocarcinoma cell lines used for cancer research were in fact anything but, according to a brief communication published online January 14 in the Journal of the National Cancer Institute. Two of the cell lines have been used in 11 U.S. patents and were part of more than 100 published studies.
The 13 established esophageal adenocarcinoma cell lines (or 14 if another suspect one is in fact authentic) are important because of the limited availability of patient samples and the fact that there are no animal models of the disease. New drugs can be tested on these cells to see if they have an effect before they are tested on real patients and important biochemical pathways can also be elucidated.
What is Esophageal Cancer?
Esophageal cancer forms in tissues lining the esophagus (the muscular tube through which food passes from the throat to the stomach). Two types of esophageal cancer are squamous cell carcinoma (cancer that begins in flat cells lining the esophagus) and adenocarcinoma (cancer that begins in cells that make and release mucus and other fluids).The exact causes of this cancer are not known but chronic/heavy alcohol use,smoking,previous history of other head and neck cancers and a condition known as Barrett's Esophagus (pre-malignant condition caused by long term irritation of tissues by stomach acid at the bottom of the esophagus which over time may cause cells in the irritated part to change and resemble cells that line the stomach) are known risk factors.Interestingly people who use both alcohol and tobacco have an especially high risk of esophageal cancer as it is thought that they increase the harmful affects of each other.
To determine the authenticity of all the available cell lines, Winand N.M. Dinjens, Ph.D., Department of Pathology, Erasmus MC, University Medical Center, in Rotterdam, the Netherlands,
and colleagues used data from pathology archives and genotyping assays in collaboration with the primary investigators who established the cell lines.
Cell lines SEG-1, BIC-1, and SK-GT-5 were proven to be cell lines from other tumor types, including lung carcinoma, colorectal adenocarcinoma, and gastric fundus carcinoma, respectively.
"Experimental results based on these contaminated cell lines have led to ongoing clinical trials recruiting [esophageal adenocarcinoma] patients, to more than 100 scientific publications, and to at least three National Institutes of Health cancer research grants and 11 U.S. patents, which emphasizes the importance of our findings," the authors write. "Widespread use of contaminated cell lines threatens the development of treatment strategies for [esophageal adenocarcinoma]."
According to the brief communication,the cell lines whose authenticity was verified will be placed in public repositories to promote future research, The researchers also suggest that the clinical
trial involving Barrett-related esophageal adenocarcinoma patients on the drug sorafenib (Nexavar) should be reconsidered as it has now been shown that the incorrect cell line was used. They say there is now little evidence for the inhibition of the mitogen-activated protein kinase pathway by the drug in this cancer. Nexavar is approved for kidney and liver cancer but has not yet been approved for esophageal cancer.
In an accompanying editorial, Robert Shoemaker, Ph.D., of the National Cancer Institute at Frederick in Maryland, questions this suggestion, pointing out that tissue of origin may not be important for allresearch studies. "…Given the knowledge that cancer is a heterogeneous
disease," he writes, "one might question the rationale for any therapeutic maneuver that is based on studies conducted on a single cell line."Shoemaker suggests that a study conducted with thecorrect cell lines (esophageal adenocarcinomas) would probably provide
the same rationale for sorafenib because alterations in mitogen-activated protein kinase pathways are common in many tumor types.
The problem of cell line contamination is not a new one and there have been warnings in the past for scientists to verify the authenticity of their cell lines before use.If not they risk producing misleading findings and possibly throwing their findings into dispute in the future.
Other scientists were also less alarmist about the findings saying that the unintentional misidentification or contamination of the cell lines is not critical and is even a fairly common occurrence.
"From the scientific point of view, it's not a huge deal, but it's certainly something you're glad you found out," said Charles Saxe, scientific director of the Program in Cancer Cell Biology and
Metastasis at the American Cancer Society in Atlanta. "This probably doesn't surprise anybody. The surprise is probably that there were only three."
And clinical trials shouldn't necessarily be stopped, Saxe said, but researchers "need to go back to the other 10 cell lines that are good and see how much of this stuff holds up. They're not
saying pull the plug."
Verifying Cell lines
University's and research scientists could take a leaf out of the book used by any quality control lab worth its salt;that is check it is what it says it is and then check it again!In any pharmaceutical company raw materials being used in a plant are barely in the door before each one is tested to ensure it is as pure as the manufacturer stated ,in the correct concentrations and amounts and it doesn't contain anything unexpected.Although this would obviously be unfeasible in a research setting due to lack of staff and funds,checking cell lines are in fact
what they say they are should now become a typical part of starting work with any new cell line.
In the UK, one of the main funders of cancer studies, Cancer Research UK, has reported that it uses DNA testing to check its cell lines.The Health Protection Agency also operates an extensive cell culture collection and a spokesman said it urged scientists to, where necessary, pay for tests to check their cell lines.Their website is very informative and provides a detailed list of all known contaminated or 'false' cell lines and those that are suspected to be.Click here to access it.
They said: "The use of wrongly identified human cancer cell lines is a problem that was first recognized more than 20 years ago.
"We draw attention to this danger on our website, which includes an ever-expanding list of those cell lines known to be incorrectly identified, or cross-contaminated with a cell line of a different type.
"As a national culture collection we, together with other national collections, exhort research scientists to always work with authenticated cell lines of known provenance."