A new approach is needed in the fight against cancer

Did you know there are over 200 different types of cancer that affect humans? Each type of cancer is complex and highly diverse. That’s why animal research has proven highly unreliable and most human cancers remain difficult to cure.

So today, on World Cancer Day, while we think of those who are affected by this devastating disease, we also reflect on the countless animals who continue to suffer and die in fruitless research.

In cancer experiments, mice are often given cancer by exposing them to radiation, viruses, bacteria and cancer-causing chemicals (known as carcinogens) or transplanting human tumours into their bodies. They are then injected with drugs or subjected to radiation to see if the cancer can be cured. Genetically modified mice are also used to create animals who are likely to develop certain types of cancer.

There are huge differences between mice and people, which makes the value of these experiments extremely unreliable.

For example, one study found that out of over 100 mouse cell types, only 50% of the DNA responsible for regulating genes in mice could be matched with human DNA¹. This means that there will be significant differences between the two species in the way that the cells and organs in our bodies work.

Also, only one-third of known human carcinogens have been shown to be carcinogenic in animals. For example, smoking does not cause cancer in mice and yet it is responsible for 25-30% of cancer deaths in people.

Perhaps unsurprisingly, cancer drugs have been shown to have the lowest success rate out of all drug approvals. A survey of 4,451 drugs made by 835 companies between 2003 and 2011 found that only 6.7% of cancer drugs were approved after entering the first phase of clinical trials². The researchers that carried out the study admitted that “current animal models [of cancer] can be poor predictors of clinical outcomes in humans.”

Most recently, the use of ‘humanised mice’ has been hyped in the media as the answer to curing cancer in humans. In these experiments, mice are made ‘more human’ by having portions of the human immune system injected into their bodies before transplanting human tumours.

Experts caution that it has not been proven that the use of humanised mice will prolong the lives of cancer patients. And like all animal cancer experiments, there are still many limitations e.g. difficulties adapting the human immune system with the mouse immune system³.

Instead of trying to make mice ‘more human’, we should be looking ahead to what can be achieved using technologically advanced human-specific alternatives.

Non-animal methods have already been central to breakthroughs in treatments for cancer. For example, epidemiological research (study of human populations) led to the discovery that smoking causes cancer. Also, because of unreliable animal screening studies, human cancer cells are now vital for screening for new drugs that might have anti-tumour benefits⁴.

Sources:

1. A comparative encyclopaedia of DNA elements in the mouse genome. (2014). Nature, 515: 355-264.
2. Clinical development success rates for investigational drugs. (2014). Nature Biotechnology, 32(1): 40-51.
3. Overcoming current limitations in humanized mouse research. (2013). Journal of Infectious Diseases, 208(2): S-125-S130.
4. The NCI in vitro anticancer drug discovery screen: Concept, implementation and operation, 1985-1995: http://home.ncifcrf.gov/mtdp/catalog/full_text/paper309/Paper309.pdf.