List of contaminated cell lines

This is a list of cell cultures which have been cross-contaminated and overgrown by other cells. A project is currently underway to enumerate and rename contaminated cell lines to avoid errors in research caused by misattribution (Masters, 2002). Estimates based on screening of leukemia-lymphoma cell lines suggest that about 15% of these cell lines are not representative of what they are usually assumed to be (Drexler et al., 2002).

Contaminated cell lines have been extensively used in research without knowledge of their true character. For example, most if not all research on the "endothelium" ECV-304 or the "megakaryocyte" DAMI cell lines has in reality been conducted on bladder carcinoma and erythroleukemia cells, respectively. Thus, all research on endothelium- or megakaryocyte-specific functions utilizing these cell lines has turned out to be worthless, except as a warning example.

There are two principal ways a cell line can become contaminated: cell cultures are often exchanged between research groups; if, during handling, a sample gets contaminated and then passed on, subsequent exchanges of cells will lead to the contaminating population being established, although parts of the supposed cell line are still genuine. More serious is contamination at the source: during establishment of the original cell line, some contaminating cells are accidentally introduced into the cultures, where they in time outgrow the desired cells. The initial testing, in this case, still suggested that the cell line is genuine and novel, but in reality, it has disappeared soon after being established and all samples of such cell lines are actually the contaminant cells. It requires lengthy research to determine the precise point where cell lines have become contaminated.

Cell lines marked Virtual in the table below are known instances of contamination at the source; these cell lines went extinct or never existed. Cases where non-contaminated lines are known or strongly suspected to exist are marked Extant

Contaminated cell lines should never be used for research demanding the specific type of cell line they are assumed to be, and most of them should ideally be discarded or at least not used in research at all, except when the contaminant cells have acquired novel characteristics (e.g., by mutation or viral transfection, for example the HeLa derivate Det98) and thus constitute a novel lineage after all.

If in doubt, researchers should test cell lines for authenticity; the references listed below contain some papers on how common contaminants can be recognized. It is worth noting that the widespread contamination with HeLa cells was initially recognized by Walter Nelson-Rees using simple Giemsa stain karyotyping under a light microscope. This technique works well in recognizing HeLa because these cells have distinctive chromosome aberrations.

Novel cell lines should be proliferated and distributed and/or deposited at a safekeeping institution such as the ATCC as soon as possible after establishment, to minimize the odds that the line becomes spoiled by contamination. It is good practice to periodically check cell lines maintained under laboratory conditions (i.e., not placed in long-term storage) for contamination with HeLa or other common contaminants, to ensure that their quality and integrity is maintained.

Lists of contaminated cell lines
If no species is given in the individual entries, the table's species applies to both the assumed and the actual cell types.