False human hematopoietic cell lines: cross-contaminations and misinterpretations

The risk of adventitious contamination and subsequent overgrowth of cell lines by unrelated cells is a potential and often recurring problem where cells are grown and studied. This problem of intraspecies and interspecies cross-contamination among human cell lines has been recognized for over 25 years; incidences of cell cross-contamination between 17 and 35% have been reported. The most useful methods to detect human cell cross-contamination are DNA fingerprinting and cytogenetic analysis, each complementing the other. Using this combination, we found that in total 14.8% of the human hematopoietic cell lines received either from the original investigator (n = 117 cell lines) or from secondary sources (n = 72 cell lines) were cross-contaminated with another hematopoietic cell line and were thus false cell cultures. Another problem relates to the fact that not every cell line established from a patient with a hematopoietic malignancy is a malignant cell line; unintended immortalization of non-malignant B cells by 'passenger' Epstein-Barr virus (EBV) leads to the establishment of B-lymphoblastoid cell lines (termed EBV+ B-LCLs), an event which is much more frequent than the establishment of a 'true' leukemia-lymphoma-myeloma cell line. These EBV+B-LCLs are most often (albeit not always) unrelated to the malignant clone. The misinterpretation of such EBV+ B-LCLs as true malignant hematopoietic cell lines (particularly in research areas investigating B cell-derived neoplasms such as myeloma) and the indiscriminate use of these cell lines may render some of the results of such studies irrelevant to the pathobiology of the disease concerned. However, a combination of markers commonly allows for an accurate determination of the nature of EBV+ B-LCLs: immunoprofile, cellular morphology, EBV status, and karyotype. In summary, the continuous need for vigilant quality and identity control procedures is emphasized by the high incidences of cross-contaminated cell lines. Most laboratories using cells cultured in vitro maintain multiple cell lines. Such cell lines should be monitored regularly for their identity and specific characteristics in order to prevent invalidation of research work due to incidents of cell line cross-contamination or misinterpretation.