A group of authors in China has retracted their December 2013 paper in PLoS ONE after realizing that they’d been studying the wrong cells.
The paper, “Up-Regulation of pVHL along with Down-Regulation of HIF-1α by NDRG2 Expression Attenuates Proliferation and Invasion in Renal Cancer Cells,” came from Lei Gao, of the Fourth Military Medical University, in Xi’an, and colleagues. It purported to find that:
The majority of renal cell carcinomas (RCCs) are characterized by loss of function of the tumor suppressor gene von Hippel Lindau (VHL), which acts as ubiquitin ligase for hypoxia-inducible factor-1α (HIF-1α). In the absence of VHL, HIF-1α protein becomes stabilized and contributes to tumorigenesis. Recent data demonstrate the antitumor efficacy of VHL promoter in RCC cells. This study demonstrates that N-Myc downstream-regulated gene 2 (NDRG2) is a potential regulator of VHL. NDRG2 is involved in proliferation and invasion of cancer cell, furthermore it is frequently down-regulated in renal cell carcinoma. Herein we evaluated the effect of NDRG2 overexpression on proliferation and invasion in human renal cancer cells. The human renal cancer cell line 786-O and A498 were infected with Ad-NDRG2 or Ad-LacZ. Overexpression of NDRG2 not only inhibited the growth of the cells, but also suppressed the invasion. Further study showed that the tumor suppressor gene VHL were up-regulated, whereas transcription factor HIF-1a and vascular endothelial growth factor (VEGF) were down-regulated in 786-O cells infected by Ad-NDRG2. Finally, in a nude mouse model, intratumoral injections of Ad-NDRG2 every 3 days for a total of seven times significantly inhibited the growth and angiogenesis of xenografted 786-O tumors. In conclusion, these data indicate that NDRG2 may be involved in proliferation and invasion by impacting the expression of VHL and HIF-1α. NDRG2 may be an attractive therapeutic target for renal cell carcinoma.
Not so attractive, after all. According to the retraction notice:
The authors retract this publication due to concerns about the cell lines employed in the study.
One part of the study involves an assessment of the effects of NDRG2 on the expression of pVHL, HIF-1α and VEGF in 786-O cells. After the publication of the article, a reader raised concerns that the human renal cancer cell lines 786-O and A498 used in the study lack HIF-1α. In addition the cell line 786-O has been reported to be VHL negative. The authors have completed a short tandem repeat analysis on the cell lines and this has revealed cross-contamination, which compromises the relevance of the work to renal cell carcinoma, and thus the conclusions of the study.
In the light of this, the authors retract this publication.
Cell line mixups have been the cause of retractions before.
Hat tip: Rolf Degen
Presumably the contaminant is another epithelial cell line that “looks the same” in the flask when grown to confluence. The STR profile is on ATCC’s website for cell lines, so that should be helpful in determining the contaminant in question.
Any lab that cultures the common transfected lines will have cross-contamination in most of their other cell lines, including primaries. It is a problem that is almost always buried.
Imagine 1 cell line B that grows 3 times faster than cell line A. If a few microlitres of the cell line B at 1 million cells/ml gets into the Cell line A’s flask, after just a few passages (changing media and diluting the cells when they’re confluent) the contaminating cell line B will be the majority cell type of cell line A’s flask.
Presumably the cross-contamination in question was not spotted when looking down the microscope!
The retraction appears to be a good example of some quality control, although at a late stage. There are examples where some cell lines turn out to be a slightly different types of cells, although they have many “functional” and morphological criteria of endothelial cells. I think there could be a possibility in my example to still be able to publish that old work of cell rolling on endothelial and endothelial-“like” cells as long as this is well explained to the reader. Such a “wrong” cell line with almost all functional characteristics of an endothelial cell line can have even many advantages, i.e. missing some of the otherwise interfering adhesion receptors. But I don’t know if I really should finish such a paper and trying to argue that a non-endothelial line is included for interesting experiments… (expressing “only” the interesting receptors).
This retraction isn’t just an issue about cross contamination. It’s about using cell lines without even knowing their published characteristics with regard to one’s oncogenic model.