Sir

In 1981, Nelson-Rees et al. found that many cell lines had been unwittingly switched or cross-contaminated with HeLa cells1. Despite that warning, the number of published cases of cross-contamination is still increasing. Reference culture collections use techniques including DNA fingerprinting to authenticate their cell stocks2,3,4 and continue to discover HeLa contamination2,5. In such cases, the only remaining characteristic of the original cultures is their name!

Misrepresentation of such cultures is perpetuated in scientific publications where the original designation is retained, including several HeLa derivatives of established value as reference cells, for example Hep2c, INT407 and KB — used respectively in virology, bacterial studies and cancer research5.

The American Type Culture Collection (ATCC) recently found 15 cases that were not authentic among newly acquired cell lines (see http://www.atcc.org ). Furthermore, a recent survey of 252 human tumour cell lines, performed by the German Collection of Microorganisms and Cell Cultures (DSMZ), identified 45 (18%) that had been cross-contaminated by their originators6.

It is high time that the true origins of ‘cross-contaminated’ cultures are acknowledged, for transparency and to raise awareness amongst those new to cell culture. Action at several levels is required.

We recommend clear identification of cross-contaminated cultures in catalogue entries of culture collections. Thus, we propose that HeLa-contaminated cultures should carry the appendage ‘(HeLa)’ in addition to the official cell name.

Resource centres and scientific organizations (such as the World Health Organisation international cell banks) should collaborate to authenticate cell stocks and ensure unrestricted access for research.

When new cell lines are established, representative samples of the original tissue, cells or DNA should be archived by originators for later authentication of cell stocks.

Authentication of new cell lines should be a prerequisite for publication. We strongly recommend that this should be by submission to a culture collection (not necessarily for immediate release to other investigators). This protects the intellectual investment of the originator and is a prerequisite for certain patents.

Cell lines should be disseminated only if they are from authenticated sources, such as bona fide culture collections; recipients should refer to guidelines on best practice in cell culture, such as those produced by the UK Co-ordinating Committee on Cancer Research and the US Food and Drug Administration7,8.

Proper documentation must accompany a cell line being transferred between laboratories, including a description of the cell line, its origin and provenance, confirmation of authenticity and freedom from mycoplasma, and biohazard information.

Such precautions could save months or years of wasted work. Those using cell culture in research and development should remember a phrase coined in information technology: “garbage in, garbage out”.

Other signatories of this letter: J. R. W. Masters Institute of Urology, University College London, 67 Riding House Street, London W1P 7PN, UK R. J. Hay American Type Culture Collection, 10801 University Boulevard, Manassas, Virginia 20110-2209, USA  H. G. Drexler, R. A. F. MacLeod German Collection of Microorganisms and Cell Cultures, Mascheroderweg 1b, 38124 Braunschweig, Germany R. I. Freshney CRC Department of Medical Oncology, University of Glasgow, Garscube Estate, Bearsden, Glasgow G61 1BD, UK