Cancer Research – Why We Can’t Keep Using Mice

How cancers in humans form and progress is incredibly complex, we simply can’t try and model it in a different species and expect the results to translate over to humans.
August 9, 2022
“The history of cancer research has been a history of curing cancer in the mouse. We have cured mice of cancer for decades—and it simply didn’t work in humans.”

- Richard Klausner, M.D., former director of the National Cancer Institute, to the Los Angeles Times.1

This statement was made over 20 years ago. Yet, we are still subjecting mice and rats to this kind of research.

Using animals for research into life-threatening diseases, such as cancer, is often perceived as justified – that the death of a few hundred mice is worth it if it’s going to save people.

In reality, this choice doesn’t exist. We do not need to choose between the life of a mouse or the life of a human. Not only can we both live but by removing animals from the equation and focusing on human-based research instead, we’ll inevitably be able to increase the chances of helping people in need.


Rats and mice have been preferred experimental models because of their relatively short life span, ease of handling, widespread use in academic studies, their susceptibility to tumours, and the availability of their genetic information.

They are used for:

  • Testing potential cancer treatments: For example, injecting rodents with cancer cells and monitoring the effects of test drug injections.
  • Carcinogenicity studies: Testing if something can cause cancer.

Animals are used in these types of studies right here in Aotearoa, New Zealand…


The below studies were published in 2020, 2021 and 2022, showing a sad trend at this institute.

Mice were injected with cancer cells to try and test a potential vaccine2

Mice were injected with cancer cells, followed by one of several potential vaccines. They were killed when the cancer reached a certain size, or it became otherwise “inhumane” to keep them alive. On average, this point was reached after 20 to 24 days.

Ulcers formed on tumours in 20% of the mice - these animals were killed before the experiment ended.

Mice were used to test the impact of exercise on cance3,4

During experiments, groups of mice were:

  • Injected with either breast or skin cancer.
  • Given treatment or were left untreated.
  • Given access to a running wheel or not.

All animals were killed at a maximum “humane” tumour size; on average, within 19 days. Along with control mice, they were anaesthetised, and their necks were broken.

Eight mice in one of the experiments had to be killed early because their condition worsened too fast, and one mouse did not develop any tumours.

Mice were used to try and test the safety of a potential prostate cancer drug5

Prior to this study, human trials were conducted using a similar drug that was toxic and inefficient in humans. So, this new study involved testing a new drug in the hopes that it would be better.

Here mice were force-fed with the new drugs daily for 21 days (in different doses). Some were force-fed with a control solution, and some were left completely untreated. On day 22, the animals were killed with CO2 and dissected, except for one completely untreated control mouse who died unexpectedly on day 7.


How cancers in humans form and progress is incredibly complex, we simply can’t try and model it in a different species and expect the results to translate over to humans.

Quick facts

1. Many factors influence how a tumour behaves in an organism and how it reacts to treatment. For example, results can change depending on the breed or sex of mice used, where in the body the cancer cells are injected, the stress levels of the animals (i.e., from relocation, surgery, isolation, handling) and even the season of the year that the experiment is conducted can impact the results!6

2. The success of animal models in approving a cancer drug for humans is one of the lowest overall, with a mere 1.6% success rate (or about 10.7% when using biomarkers). 7

3. The U.S. Food and Drug Administration (FDA), which is responsible for approving the use of drugs for humans, estimates that less than 10% of drugs tested on animals get approved to go to market. 8

4. A whole group of chemicals (called MMP Inhibitors) have been showing great success against aggressive cancers in animal models since the 1980s. But none of them has made it through clinical trials on humans,9 yet some researchers keep trying to make it work and continue testing them on mice.10

5. Despite macaque monkeys and rats showing promising results and no negative side effects of a potential blood cancer drug, the six human volunteers trying a much lower dose experienced life-threatening complications within hours.11

6. Inorganic arsenic is well known to be highly toxic to humans, and skin cancer is a quite common symptom.12 Yet, researchers failed to find any cancer-causing effect in animals, even in 2-year experiments of feeding arsenic to rats and dogs.13 It is less toxic overall for them, too.14

It’s vital that we end animal experimentation as soon as possible, for the animals who are forced to endure cruel procedures and for humans who urgently need useable treatments and cures.

The image above was taken from our children's book The Six-Foot Rats, which was written and illustrated by Rebecca Gibbs Illustration for NZAVS.

With your help we can end animal experimentation in Aotearoa.