The Immortal Life of Contaminating and Misidentified Cell Lines

As the building blocks of life, cells are the most basic structural, functional, and biological units found in living organisms. Bacteria are classified as unicellular as they only consist of a single cell, whereas plants and animals are multicellular. The study of the biology of cells in the laboratory environment has greatly advanced our understanding of the nature of life itself. Cell culture refers to the process used by researchers to grow cells (human, animal, insect, etc.) in a favourable artificial environment.

There are two fundamental components of cell culture: isolating the cells of interest, and maintaining the survival and/or growth of those cells in culture. Cells that are isolated directly from a source are referred to as primary cells. Immortalized cell lines refer to cell lines that have been manipulated to grow indefinitely (if provided the right growth conditions). Luckily, there are organizations, such as the American Type Culture Collection, that collects, stores and distributes cell lines, thus making the “isolation” step much easier. After a researcher isolates (or selects) the cells to be used in their experiments, they have to think about maintaining those cells in culture. Culture conditions can vary widely depending on the cell type. In general, there are six components that comprise the media used to grow cells: carbon (for energy), amino acids (for protein building), vitamins (for cell growth), balanced salt solution (for maintenance of osmotic pressure with the cells), pH indicator, and a buffer (for maintenance of media pH). It is important that the culture conditions are not only correct for the cell type, but are also consistent over the course of the experiment, as variations of conditions can lead to different cellular phenotypes. Cells are left to grow in an incubator set to an assigned temperature and gas mixture (usually 37°, 5% CO₂). The gas helps to buffer the pH of the culture media. After a period of time, cells will stop dividing, a sign the cell population is too dense, and thus they will be “split” (cells are diluted and plated into new dishes), allowing dividing to resume.

The introduction of cell lines revolutionized scientific research by providing consistent ‘reference’ cells that could help researchers in different labs generate reproducible results. Furthermore, cell lines provided researchers with an opportunity to investigate potential phenotypes before using animal models. Unfortunately, as discussed by Horbach et. al., cell line misidentification is a big problem. In their article, they conducted extensive literature searches and found that 32,755 articles report research with misidentified cells, and in turn those articles had been cited in an estimated half a million other papers. The HeLa cell line (popularized by the novel “The Immortal Life of Henrietta Lacks”), for example, has been causing controversy since the 1960’s. Around this period, researchers began to identify HeLa cells in their other cell lines. This insight had huge implications as it called into question if previously reported results were indeed accurate, or a manifestation of HeLa contamination. This article highlights the need for better identification of cell lines. In addition, it proposes the use of a “paper trail” for each cell line in order to better document each line.

Cell culture is an invaluable research technique, but moving forward, systems have to be designed to carefully manage cell line literature. This article forces its readers to think about the implications of misleading literature (whether that be misidentified cell lines, or something else).

Summary written by: Emma Finlayson-Trick

To read the full article, please click the following link:

The ghosts of HeLa: How cell line misidentification contaminates the scientific literature

Serge P.J.M. Horbach, Willem Halffman