Cell line authentication: a necessity for reproducible biomedical research.

Immortalized or continuous cell lines are invaluable tools in basic and preclinical research. However, the widespread use of misidentified cell lines is a serious threat to scientific reproducibility. Based on the experiences of mandatory cell line authentication at the International Journal of Cancer (IJC), we provide an overview of the issues pertinent to misidentified cell lines and discuss available solutions. We also summarize the lessons learned, revealing that at least 5% of the human cell lines used in manuscripts considered for peer review are misidentified. About 4% of the considered manuscripts are rejected for severe cell line problems, and most are subsequently published in other journals. In order to diminish such malpractice and its consequences for the scientific record, we postulate that strict multi-layered quality control is essential. Besides journals and publishers, we encourage scientists, research institutions, and funders to take action on the matter and revise their respective policies. Hence, we provide concrete recommendations on introducing regular authentication schemes and staff training, and discuss future steps for enhancing good cell culture practices.

The need for a worldwide consensus for cell line authentication: Experience implementing a mandatory requirement at the International Journal of Cancer.

Cell lines are used in life science research worldwide as biological surrogates. All cell lines are subject to major limitations when used as research tools, including (i) cross-contamination with other cells cultured in the same laboratory environment and (ii) evolution in vitro that renders a given cell line inappropriate as a surrogate for a specific biological hypothesis. There is ample evidence that cross-contamination or phenotypic drift of cells in culture can generate irreproducible or misleading data. A small number of scientific journals-the International Journal of Cancer being at the forefront-and funding agencies have recently moved forward to ask for obligatory cell line authentication data. The history of implementing such rules by the International Journal of Cancer exemplifies the difficulties encountered when installing mandatory quality measures in life sciences.

Isothiocyanates in cancer prevention.

Isothiocyanates are sulfur-containing compounds which are largely responsible for the typical flavor of cruciferous vegetables. In animals and humans they are conjugated with glutathione; the first product of this reaction is a dithiocarbamate, which can be ultimately metabolized to the corresponding mercapturic acid, excreted in urine. Aliphatic and aromatic isothiocyanates, as well as dithiocarbamates, can react quantitatively with an excess of 1,2-benzenedithiol giving rise to a cyclic condensation product readily measured in biological fluids. The use of this assay as a biomarker of isothiocyanate or cruciferous vegetable intake can offer several advantages over food frequency questionnaires, mainly in the objectivity and accuracy of the measure and the lack of bias. Epidemiological studies on the relationship between cancer risk with isothiocyanate intake or excretion have shown inverse associations, mainly with lung cancer. The studies are also consistent in reporting a gene-environment interaction, with a stronger protective effect in persons null for the GSTM1 or GSTT1 genotype. However, further research is needed to better clarify the importance of these polymorphisms in modulating the effect of isothiocyanates in cancer development.

Weight control and physical activity in cancer prevention.

Overweight and obesity have reached epidemic dimensions worldwide, mainly due to consumption of high energy diets and increased sedentary behaviour. Overweight and insufficient physical activity are clearly associated with cardiovascular diseases and type 2 diabetes. Evidence is also accumulating that they may also increase cancer risk, particularly in the colon, breast and endometrium. This effect seems to be mediated by alterations in the metabolism of endogenous hormones, including sex steroids and insulin, and levels of insulin-like growth factor(IGF)-I and IGF-binding proteins. In light of the beneficial effects of weight control and physical activity for cancer prevention, a healthy lifestyle, keeping a low body weight and exercising most days of the week, is recommended.

Weight control and physical activity in cancer prevention: international evaluation of the evidence.

To evaluate the evidence for the role of weight control and physical activity in cancer prevention and to identify priorities for research and for public health action in relation to the primary prevention of cancer, an international working group of experts was convened in Lyon in February 2001 by the International Agency for Research on Cancer of the World Health Organization. The expert group concluded that limiting weight gain during adult life, thereby avoiding overweight and obesity, reduces the risk of postmenopausal breast cancer and cancers of the colon, endometrium, kidney (renal cell) and esophagus (adenocarcinoma). Limiting weight gain possibly reduces risk of cancer of the thyroid. Weight loss among overweight or obese persons possibly reduces risks of these cancers, but no definite conclusion can be drawn because of the paucity of the epidemiological evidence. The working group also concluded that there was sufficient evidence for the role of physical activity in preventing colon and breast cancers, and limited evidence for the cancers of the prostate and endometrium. Some of these effects were independent of that of the weight control. Taken together, the working group considered that excess body weight and physical inactivity account for approximately a quarter to one-third of cancers of the colon, breast, endometrium, kidney (renal cell) and esophagus (adenocarcinoma). Thus adiposity and physical inactivity appear to be the most important avoidable causes of these cancers.