A Combination of Species Identification and STR Profiling Identifies Cross-contaminated Cells from 482 Human Tumor Cell Lines

Xiaocui Bian,Hailiang Feng,Yuqin Liu,Zhenli Yang,Hao Sun

doi:10.1038/s41598-017-09660-w

Xiaocui Bian, Hailiang Feng + Show 3 more

Open Access

https://doi.org/10.1038/s41598-017-09660-w

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Abstract

Human tumor cell lines are extremely important tools for cancer research, but a significant percentage is cross-contaminated with other cells. Short tandem repeat (STR) profiling is the prevailing standard for authenticating cell lines that originate from human tissues. Based on the analysis of 482 different human tumor cell lines used in China by STR, up to 96 cell lines were misidentified. More importantly, the study has found that STR profiling alone is insufficient to exclude inter-species cross-contamination of human cell lines. Among the 386 cell lines which had a correct STR profile, 3 of them were inter-species cross-contaminated. Careful microscopic examination may be helpful in some cases to detect changes in morphology but additional testing is needed. Additionally, species verification by PCR could easily identify the contaminants, even with a low percentage of contaminating cells. Combining STR profiling with species identification by PCR, more than 20.5% (99/482) of tumor cell lines were revealed as having been incorrectly identified, including intra-species (14.5%), inter-species (4.4%) cross-contamination and contaminating cell lines (1.7%). Therefore, quality control of cell lines is a systemic issue. Each cell line should undergo a full QA (Quality Assurance) assessment before it is used for research.

Highlights

We report the authentication of cell lines
Among 482 human tumor cell lines tested in our study, there were 20.5% (99/482) of misidentified cell lines, which is lower incidence than that reported by Ye et al (25.0%, 95/380)[5] and Huang et al (46.0%, 128/278)[15] because of different statistical range and calculating method, as mentioned in “Samples and genomic DNA extraction” in the Methods
Some were misidentified when introduced to China long ago, such as the famous HeLa contaminants KB and Hep-2, while some cells may have been cross-contaminated during culture in China

Summary

Results

As reported, OCM-1 cells were originally cultured from a human choroidal melanoma specimen in 198519, C918 and M619 cells were derived from patient tumors at the University of Iowa in the 1990s20 and Mum-2B and Mum-2C were derived from a heterogeneous tissue explant MUM-221 These 5 cell lines should show 4 different STR DNA types, but only 2 STR profiles were detected. When species identification was performed by PCR, 21 human cell lines were found to be fully substituted by another species such as rat, monkey, Chinese hamster, Syrian hamster or bovine (see Supplementary Table S4, Fig. 4) Some of these cell lines were further examined by STR profiling, and no signal was detected, as anticipated. Some cell lines, such as the human lowly metastatic lung cancer cell line PG-LH7, lacked 2 distinct cell morphologiesand showed correct STR profiles, but they were still mixed with cells from other species (Fig. 7)

Discussion

Methods