Why Alternative Cancer Treatment

It is not possible to apply to the human species, experimental information derived from inducing cancer in animals.
Dr Kenneth Starr, Hon. Director of the New South Wales Cancer Council, Sydney Morning Herald, 7 April 1960

Welcome to page twenty-one of “Why Alternative Cancer Treatment?” which shows alternatives to animal experimentation.

Cancer Research Without Animals:

Improved cell culture methods for anti-cancer drug development

National Anti-Vivisection Society

In October Professor Ian Cree of the Translational Oncology Research Centre, Queen Alexandra Hospital in Portsmouth was awarded a grant to develop improved cell culture techniques for testing the efficacy of anti-cancer drugs, using human cancer cell lines cultured in human serum.

Cancer research organisations and pharmaceutical companies use panels of cell lines grown in culture and grafted onto animals, usually mice, and giving groups of animals different doses of new anti-cancer drugs to determine their efficacy.

Alternative approaches are to use tumor cells derived from patients, or cell lines which mimic the situation in the living body. Obtaining large numbers of tumor-derived cells to substitute for the animal experiments can be difficult and costly and hard to compare the effects of new drugs between different tumour types.

Although cultured cell lines are relatively inexpensive and give reproducible results rapidly, the relevance of these results to the efficacy of anti-cancer drugs on cancer cells in human patients is not well established.

There are differences between cell lines and cells taken directly from the patient. The growth rates of cell lines and tumour-derived cells differ. Cell lines consist of rapidly dividing identical cells, whereas cells taken from tumours are generally a mixed population consisting of cancer cells, the characteristics of which are determined by their environment, and non-cancer cells.

Additionally, cells lines may lose some of the characteristics which they possess in the living body, due to prolonged culture. Because of these differences between cell lines and tumor-derived cells, there are differences in their sensitivity to drugs which kill cancer cells. For example, anti-cancer agents tend to target growing cells, so cell lines are more sensitive than tumour-derived cells.

The aim of this study is to generate defined media (the cell growth medium) and cell lines suitable for widespread use in testing new agents, in place of using animals. Professor Cree and colleagues have demonstrated previously that growth rate and drug sensitivity of the cell lines can be altered by reduced serum concentrations in culture.

Cell lines are generally poor representatives of the tumours from which they are derived because they are adapted to cell culture conditions. By altering the environment in which the cells are cultured, it may be possible to make cell lines behave more like tumour-derived cells. The response of the cell lines, cultured in altered conditions, to standard anti-cancer drugs, will be compared to a set data of known effects on tumor-derived cells.

Just over ten years ago, Professor Cree's team developed an assay called the Adenosine Triphosphate Tumour Chemosensitivity Assay (ATP-TCA), which measures ATP, the most basic fuel of living cells. The amount of ATP present in a cell population reflects the number of viable cells. This technique will be used to assess the toxic effects of the drugs in culture.

Professor Cree and colleagues have used the ATP-TCA assay to look at both tumor-derived cells and cell lines. Over 9 years all data collected from ATP-TCA experiments using different drugs tested on different tumour types has been added to a database. This currently holds data for 1,400 human tumours.

Cell lines will be derived from cells obtained from small pieces of human tumor tissue representing common tumor types, such as breast, lung, bowel, gullet/stomach, ovarian, prostate and melanoma. The majority of the cell lines to be tested are normally grown in media containing foetal bovine serum. Human serum at various concentrations will be substituted in this study. Serum-free media will also be tested.

Molecular fingerprinting of cells under culture conditions will be carried out by Affymetrix chip assays to enable comparison with representative tumor-derived cells for each of the tumor types tested. The intention is to set up a panel of cell lines whose sensitivity to anti-cancer drugs is representative of common tumor types.

The results will be published and the methods will be free to scientists to use as needed. Pharmaceutical companies are likely to be able to use this data to identify new chemotherapeutic agents more accurately and effectively.

Professor Cree said: "At present cell lines are such a poor model for likely human response that xenografts are used. Xenograft experiments use tumour cells (usually cell lines injected into animals so that tumours grow either within the peritoneum [the internal abdominal membrane or lining] or skin, followed in some cases by spread to other tissues.

At any one time there are approximately 1,000 investigational new anti-cancer drugs being tested in human subjects for possible clinical use: the turnover is probably around 500 per annum. Each one of these is probably the lead compound from around 20 drugs tested in xenograft experiments, most of which include around 30 mice.

I would therefore estimate the number of mice used per annum in such experiments as at least 300,000 per annum. This figure is likely to be an underestimate, as such models are used routinely in many cancer laboratories. While the majority of animals used are likely to be mice, there will be some use of rats, guinea pigs and rabbits for these experiments.

"The proposed cell line testing methods could replace much, if not all, of the testing of the efficacy of anti-cancer drugs in animals prior to human studies...."

269,000 procedures on animals were conducted for cancer research in the UK in 2001.

®NAVS 2003

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