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

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.