Tag Archives: animal testing

Why we haven’t cured the common cold – a response to PETA’s science advisor, Dr. Julia Baines

For a previous post that also debunks comments made by PETA, read our article, “Biology, History and Maths: A lesson in debunking PETA’s nonsense”.

The United Kingdom recently released their annual statistics of scientific procedures on living animals and, as expected, interested parties weighed in and provided their views and interpretations of these numbers (e.g., here, here and here). While it is acknowledged that providing a context for these numbers is key, it is often quite difficult to do so without sufficient passage of time. Indeed, the timeframe required for the translation of research from bench to bedside takes years, if not decades. Moreover, as science is self-generating and self-correcting, there is no explicit requirement that an applied benefit results from all scientific research, including research performed on animals.

With this in mind, which facts can we infer from these annual statistics? We can, for example, quantify the number of animals used by species (mice, rats, primates, etc.), by establishment (e.g., government, university), and by study type (e.g., basic research, breeding, applied research) to name a few. We can also do a retrospective account of the amount of pain experienced (severity) by animals used in experimental procedures. What we should not do based on these statistics, is make false claims about the procedures involved in animal research and what animal research should have achieved. In what can only be viewed as an attempt to evoke the maximum emotional response, Dr. Julia Baines, a science advisor for PETA, was quoted as saying:

“Given that the latest Home Office statistics reveal that a staggering 4.14 million scientific procedures were carried out on animals in British laboratories in 2015, we should have a cure for everything, including the common cold, by now if this was a useful method of gaining scientific information.” [Our emphasis]

As Dr. Baines correctly points out, 4.14 million scientific procedures were carried out in British laboratories. And, it is true that 4.14 million is a large number of procedures. What Dr. Baines fails to do is to provide a fact-based context for those numbers, as for example was done here and here. Such a context would reflect, for example, that the number of animals used between 2013 and 2015 increased by only 0.5%. Next, Dr. Baines goes on to imply a causal relationship between animal use and a cure for all diseases, including the common cold. While this statement is at best an example of illogical abstraction and at worst logically flawed thinking below what one would expect from a “science advisor”, I found it useful to reflect on the question, “Why don’t we have a cure for the common cold?”

The first thing worth pointing out is that the common cold is not a single virus strain. Rhinoviruses are the most common form of the cold virus but even then there are over a hundred known types of rhinoviruses.

Furthermore, curing the common cold would mean eradicating a long list of viruses which cause similar symptoms, such as adenoviruses and coronaviruses. To further complicate matters, in a given geographical area, only 20 to 30 different types of the “cold virus” circulate each season, only 10% of those will show up next year for that season, and due to viral mutation, new strains will emerge across time.  Thus, we immediately see that for something seemingly as “simple” as the common cold, producing a “cure” is exceedingly difficult.

Rhinovirus caption: Surface of the human rhinovirus 16, one of the viruses which cause the common cold. Source:Wikipedia Commons

Rhinovirus caption: Surface of the human rhinovirus 16, one of the viruses which cause the common cold. Source:Wikipedia Commons

Moreover, the statement by Julia that we should have a “cure for everything” is something that cutting edge science is working on. The basic premise is that because there are many viruses and many diseases caused by viruses, as well as many viral mutations, it may be virtually impossible to eradicate all viruses by utilizing single vaccinations. For example, Todd Rider is working on a broad spectrum antiviral approach, dubbed DRACO, which causes infected cells to die while leaving uninfected cells intact.

DRACOs have worked against H1N1 influenza in cells and mice. NIAID/Flickr (CC BY 2.0) Source: Secondary citation from here: http://www.techinsider.io/todd-rider-draco-crowdfunding-broad-spectrum-antiviral-2015-12

DRACOs have worked against H1N1 influenza in cells and mice. NIAID/Flickr (CC BY 2.0)
Source: Secondary citation from here: http://www.techinsider.io/todd-rider-draco-crowdfunding-broad-spectrum-antiviral-2015-12

Consistent with the 3Rs, this method was first developed in vitro, and given that the method showed evidence of proof of principle, in vivo trials were begun, recognizing that currently, alternative methods such as in vitro studies complement rather than replace animal research.

Todd is not the only scientist working on this problem. Brian Lichty is adopting a somewhat different approach, looking at the mechanism via which immune cells detect viruses in the body and how they trigger an immune response. Both approaches recognize the complexity of curing viral diseases, both at the level of the host and the agent, and the valuable role which animal research plays in the development of cures.

What emerges from a review of scientific history and method is this: be patient.

Dr. Baines is not alone in wishing that cures and medical progress were faster and error-free – many of us have this wish. Unfortunately, that isn’t the way science or reality works. With the help of animal research, we have great potential for curing many diseases, including diseases which affect non-human animals. It just may take some time. More importantly, I encourage all readers of information on the internet to carefully scrutinize what is presented, including this post. We are often faced with common-sense notions in our everyday life, and we often do not question such information, particularly if it is something that is consistent with what we believe to be true. We saw this behaviour most recently with the release of the animal use statistics in the UK for 2015, with facts being flagrantly misrepresented and, frighteningly, widely publicized.

Jeremy D. Bailoo

The opinions expressed here are my own and do not necessarily reflect the interests of the University of Bern or the Division of Animal Welfare at the University of Bern.

USDA publishes 2015 Animal Research Statistics

Congratulations to the USDA/APHIS for getting ahead of the curve for a second time and making the US the first country to publish its 2015 animal research statistics. Overall, the number of animals (covered by the Animal Welfare Act) used in research fell 8% from 834,453 (2014) to 767,622 (2015).

These statistics do not include all animals as most mice, rats, and fish are not covered by the Animal Welfare Act – though they are still covered by other regulations that protect animal welfare. We also have not included the 136,525 animals which were kept in research facilities in 2015 but were not involved in any research studies.

USDA Statistics_2016_A

The statistics show that 53% of research is on guinea pigs, hamsters and rabbits, while 11% is on dogs or cats and 8% on non-human primates. In the UK, where mice, rats, fish and birds are counted in the annual statistics, over 97% of research is on rodents, birds and fish. Across the EU, which measures animal use slightly differently, 93% of research is on species not counted under the Animal Welfare Act (AWA). If similar proportions were applied the US, the total number of vertebrates used in research in the US would be between 11 and 25 million, however there are no statistics to confirm this.

USDA Statistics_2016_B

If we look at the changes between the 2014 and 2015 statistics we can see a drop in the number of studies in hamsters, rabbits, cats and the “all other animals” category. Notably, there was a 7.3% rise in the number of non-human primates used although this comes the year after a 9.9% fall in their numbers.

USDA Statistics_2016_C

There has been a downward trend in the number of AWA-covered animals used in the last three decades, with a 64% drop in numbers between 1985 and 2015. It is also likely that, similar to the UK, a move towards using more genetically altered mice and fish has reduced the numbers of other AWA-covered species of animals used. In the UK this change in the species of animals studied has contributed to an overall increase in the numbers of animals used in research in the past 15 years.

Rises and falls in the number of animals used reflects many factors including the level of biomedical activity in a country, trending areas of research, changes to legislations at home and abroad, outsourcing research to and from other countries, and new technologies (which may either replace animal studies or create reasons for new animal experiments).

It is important to note that the number of animals cannot be tallied across years to get an accurate measure of total number of animals. This is because animals in longitudinal studies are counted each year. Thus, if the same 10 animals are in a research facility for 10 years, they would appear in the stats of each year – adding these numbers would incorrectly create the illusion of 100 animals being used.

Speaking of Research welcomes the open publication of these animal research statistics as offering the public a clear idea of what animal research goes on in their country.

Novo Nordisk demonstrate what good openness looks like

Openness has been a buzz word in science policy over the past five years, particularly for animal research. Today, Speaking of Research reached 250 animal research statements on our list of public statements, up from 200 in February (is your institution included?). Much of our focus has been on universities, particularly in the UK and US. In the past we have showcased examples of good openness including the University of Edinburgh, University of Cambridge, Imperial College London and Primate Products Inc.

Today we will focus on a Danish pharmaceutical company – Novo Nordisk – and their excellent efforts at greater openness and transparency around their animal research.

Novonordisk provide a whole section of their website on Animal Ethics. This starts out with a clear statement about the ongoing need for animals to test new pharmaceutical and medical products.

At present, some research using living animals is essential for all pharmaceutical companies in the discovery, development and production of new pharmaceutical and medical products.
We only use animals in research where no alternative exists. We recognise that not all research using animals can be replaced in the foreseeable future and consider it our responsibility to actively support the principles of the 3Rs.

This front page also talks about the “Responsible use of animals” including the 3Rs, efforts to replace animal tests and the importance of animal welfare. They include a video on the front page, which shows their facilities.

Novo Nordisk website providing videos of its research animals and facilities

Novo Nordisk website providing videos of its research animals and facilities

There’s dedicated subpages on Housing, Ethical Review, their 3Rs Award, Welfare  and External Contractors. They also have a page with nine different videos showing the animal enclosures. This is among the best sets of videos provided by an animal research institution showing its animals.

There is also a page which outlines the number of each species of animal used at Novo Nordisk over the past three years. In 2015, Novo Nordisk used 67,240 animals, of which almost 97% were mice or rats.

Finally, Novo Nordisk have produced a fantastic 24-page brochure titled “Animals in Pharmaceutical Research: A responsible approach” which explains more about their research, with a particular focus towards their 3Rs efforts.  The brochure provides plenty of pictures and information, as well as the principles of animal use which underpin their animal research work. Explaining why animal research is necessary to their work:

Before new pharmaceutical products can be studied in people, they need to be investigated in animals for efficacy, safety and toxicology, as it is not yet possible to examine the complex interactions in a living organism solely by the use of cell cultures and tissues.

Animals are only used in research and development at Novo Nordisk when no alternative exists. The use of animals in the early phases of the company’s drug discovery and development has been reduced by applying tissue cultures, cell-based and other non-animal models.

Click to Enlarge

Click to go to the brochure

Overall, the information provided by Novo Nordisk is fantastic – above and beyond any other pharmaceutical company’s online offering we have seen to date. If there was one possible area for improvement, it would be the provision of some case studies to explain a few examples of exactly how and why animals are used. This would also give them full marks on our animal research statement ratings.

So all that’s left to say is to congratulate Novo Nordisk for its fantastic web resources. Speaking of Research will continue to celebrate good examples of openness and public outreach wherever we can find it.

Has your institution got a statement or set or web pages explaining its animal research for the public? Is it on our list (if not, tell us)? Could it be improved? Speaking of Research has written about what makes a good public-facing webpage on an institution’s animal research.

Speaking of Research

Montage of images from the Novo Nordisk brochure on its animal research. Click to Enlarge

Montage of images from the Novo Nordisk brochure on its animal research. Click to Enlarge

We mightn’t like it, but there are ethical reasons to use animals in medical research

Trichur Vidyasagar, University of Melbourne

The media regularly report impressive medical advances. However, in most cases, there is a reluctance by scientists, the universities, or research institutions they work for, and the media to mention animals used in that research, let alone non-human primates. Such omission misleads the public and works against long-term sustainability of a very important means of advancing knowledge about health and disease.

Consider the recent report by Ali Rezai and colleagues, in the journal Nature, of a patient with quadriplegia who was able to use his hands by just thinking about the action. The signals in the brain recorded by implanted electrodes were analysed and fed into the muscles of the arm to activate the hand directly.

When journalists report on such bionic devices, rarely is there mention of the decades of research using macaques that eventually made these early brain-machine interfaces a reality for human patients. The public is shielded from this fact, thereby lending false credence to claims by animal rights groups that medical breakthroughs come from human trials with animal experiments playing no part.

Development of such brain-machine interfaces requires detailed understanding of how the primate brain processes information and many experiments on macaques using different interfaces and computing algorithms. Human ethics committees will not let you try this on a patient until such animal research is done.

Image: Understanding Animal Research

Image: Understanding Animal Research


These devices are still not perfect and our understanding of brain function at a neuronal level needs more sophistication. In some cases, the macaque neural circuitry one discovers may not quite match the human’s, but usually it is as close as we can get to the human scenario, needing further fine-tuning in direct human trials. However, to eliminate all animal research and try everything out on humans without much inkling of their effects is dangerous and therefore highly unethical.

The technique Dr Rezai’s team used on human patients draws heavily upon work done on monkeys by many groups. This can be seen by looking at the paper and the references it cites.

Another case in point is the technique of deep brain stimulation using implanted electrodes, which is becoming an effective means of treating symptoms in many Parkinson’s patients. This is now possible largely due to the decades of work on macaques to understand in detail the complex circuitry involved in motor control. Macaques continue to be used to refine deep brain stimulation in humans.

Ethical choices

The number of monkeys used for such long-term neuroscience experiments is relatively small, with just two used in the study above. Many more are used for understanding disease processes and developing treatment methods or vaccines in the case of infectious diseases such as malaria, Ebola, HIV/AIDS, tuberculosis and Zika.

Approximately 60,000 monkeys are used for experiments for all purposes each year in the United States, Europe and Australia.

However, if one looks at what is at stake without these experiments on non-human primates, one must acknowledge a stark reality. In many cases, the situation is similar to that which once existed with polio. Nearly 100,000 monkeys were used in the 1950s to develop the polio vaccine. Before that, millions of people worldwide, mostly children, were infected with polio every year. Around 10% died and many were left crippled.

Now, thanks to the vaccine, polio is almost eradicated.

Similarly, about 200 million people contract malaria every year, of whom 600,000 (75% being children) die, despite all efforts to control the mosquitoes that transmit the disease. Development of a vaccine is our best chance, but again primates are necessary for this, as other species are not similarly susceptible to the parasitic infection.

Circumstances are similar with other devastating ailments such as Ebola, HIV and Zika. The ethical choice is often between using a few hundred monkeys or condemning thousands or more humans to suffer or die from each one of these diseases year after year.


Reports of medical breakthroughs conveniently leave out animals used in the process.
Novartis AG/Flickr, CC BY

In the popular press and in protests against primate research, there is sometimes no distinction made between great apes (chimpanzees, bonobos and gorillas) and monkeys such as macaques, leading to misplaced emotional reactions. To my knowledge, invasive experiments on great apes are not done anywhere, because of the recognition of their cognitive proximity to humans.

While the ape and human lineages separated six million years ago, there is an additional 20 to 35 million years of evolutionary distance from monkeys, which clearly lack the sophisticated cognitive capacities of the apes.

With urgent medical issues of today such as HIV, Ebola, malaria, Zika, diabetes and neurological conditions such as stroke and Parkinson’s disease, monkeys are adequate to study the basic physiology and pathology and to develop treatment methods. There is nothing extra to be gained from studying apes.

Alternatives have limitations

Opponents of animal research often cite the impressive developments of computer modelling, in-vitro techniques and non-invasive experiments in humans as alternatives to animal experiments. These have indeed given us great insights and are frequently used also by the very same scientists who use animals.

However, there are still critical areas where animal experimentation will be required for a long time to come.

Modelling can be done only on data already obtained and therefore can only build upon the hypotheses such data supported. The modelling also needs validation by going back to the lab to know whether the model’s predictions are correct.

Real science cannot work in a virtual world. It is the synergy between computation and real experiments that advances computational research.

In-vitro studies on isolated cells from a cell line cultured in the lab or directly taken from an animal are useful alternatives. This approach is widely used in medical research. However, these cells are not the same as the complex system provided by the whole animal. Unless one delves into the physiology and pathology of various body functions and tries to understand how they relate to each other and to the environment, any insights gained from studying single cells in in-vitro systems will be limited.

Though many studies can be done non-invasively on humans and we have indeed gained much knowledge on various questions, invasive experiments on animals are necessary. In many human experiments we can study the input to the system and the output, but we are fairly limited in understanding what goes on in between. For example, interactions between diet, the microbiome, the digestive system and disease are so complex that important relationships that have to be understood to advance therapy can only be worked out in animal models.

Of course, animals are not perfect models for the human body. They can never be. Species evolve and change.

However, many parts of our bodies have remained the same over millions of years of evolution. In fact, much of our basic knowledge about how impulses are transmitted along a nerve fibre has come from studying the squid, but our understanding also gets gradually modified by more recent experiments in mammals.

Higher cognitive functions and the complex operations of the motor system have to be studied in mammals. For a small number of these studies, nothing less than a non-human primate is adequate.

The choice of species for every experiment is usually carefully considered by investigators, funding bodies and ethics committees, from both ethical and scientific viewpoints. That is why the use of non-human primates is usually a small percentage of all animals used for research. In the state of Victoria, this constitutes only 0.02%.

Medical history can vouch for the fact that the benefits from undertaking animal experiments are worth the effort in the long run and that such experimentation is sometimes the only ethical choice. Taken overall, the principle of least harm should and does prevail. There may come a day when non-invasive experiments in humans may be able to tell us almost everything that animal experiments do today, but that is probably still a long way off.

Priorities in animal use

The ethical pressure put on research seems to be in stark contrast to that on the food industry. It is hypocritical for a society to contemplate seriously restricting the use of the relatively small number of animals for research that could save lives when far more animals are allowed to be slaughtered just to satisfy the palate. This is despite meat being a health and environmental concern.

To put this in perspective, for every animal used in research (mostly mice, fish and rats), approximately 2,000 animals are used for food, with actual numbers varying between countries and the organisations that collect the data.

The ratio becomes even more dramatic when you consider the use of non-human primates alone. In Victoria, for every monkey used in research, more than one million animals are used for meat production. However, the monitoring of the welfare of farm animals is not in any way comparable to that which experimental animals receive.

Reduced use of livestock can greatly reduce mankind’s ecological footprint and also improve our health. This is an ethical, health and environmental imperative. Animal experiments, including some on non-human primates, are also an ethical and medical imperative.

Trichur Vidyasagar, Professor, Department of Optometry and Vision Sciences and Melbourne Neuroscience Institute, University of Melbourne

This article was originally published on The Conversation. Read the original article.

When are rats, mice, birds and fish protected by US federal laws?

There is sometimes confusion about how US law protects rats, mice and non-mammalian vertebrates such as birds and fish. Much of this confusion is rooted in the fact that the US Animal Welfare Act (AWA) explicitly excludes purpose-bred rodents (rats of the genus Rattus rattus, mice of the genus Mus mus), as well as birds that were specifically bred for research. Research with these purpose-bred rats and mice likely comprises the overwhelming majority of vertebrate animals in research in the US, but it is not overseen by the United States Department of Agriculture (USDA).

Sometimes this fact is used mistakenly (or perhaps purposely?) to suggest that all species not covered by the Animal Welfare Act are not protected by any federal laws.

Claims that research with non-AWA-covered species is not subject to care standards, external oversight, and public transparency are demonstrably untrue.

This post aims to address these misconceptions by looking at when and how rats, mice, and birds in research are covered by federal laws.

Mouse Science

Image from Understanding Animal Research

In the US, both the USDA, through the Animal and Plant Health Inspection Service (APHIS), and the Department of Health and Human Services (DHHS), through the Public Health Service (PHS) and National Institutes of Health (NIH) Office of Laboratory Animal Welfare (OLAW), are responsible for the oversight animal research. The table below provides a broad overview of the federal regulation and oversight agencies for different species and types of research.

Covered species are defined as: "with certain exceptions, any live or dead dog, cat, monkey (nonhuman primate mammal), guinea pig, hamster, rabbit, or such other warm-blooded animal, as the Secretary [of Agriculture] may determine is being used, or is intended for use for research”

Overview of animal research regulation in the US. The Animal Welfare Act (AWA) states that covered species are defined as: “with certain exceptions, any live or dead dog, cat, monkey (nonhuman primate mammal), guinea pig, hamster, rabbit, or such other warm-blooded animal, as the Secretary [of Agriculture] may determine is being used, or is intended for use for research” (7 U.S.C. 2132(g) The 2002 Farm Bill amended this definition to exclude purpose-bred rats, mice, and birds from the provisions of the AWA. Note that certain types of research with animals and most animal testing are also subject to regulation and oversight by the US Food and Drug Administration (FDA).

Animal Welfare Act (AWA) and USDA. The USDA is charged with enforcement of the AWA. The AWA applies to research with a range of species that includes: “with certain exceptions, any live or dead dog, cat, monkey (nonhuman primate mammal), guinea pig, hamster, rabbit, or such other warm-blooded animal, as the Secretary [of Agriculture] may determine is being used, or is intended for use for research” (7 U.S.C. 2132(g), referred to here as “USDA-covered species.” Institutions that engage in research with covered species must be registered with the USDA.  The AWA also applies to zoos, entertainment facilities, breeders, and other facilities that engage covered species in activities that involve public contact. All such facilities must be licensed by the USDA and research may also be conducted in facilities licensed for non-research purposes.

An amendment to the 2002 Farm Bill  specifically excluded from AWA oversight rats of the genus Rattus rattus, mice of the genus Mus mus, and birds specifically bred for research. Thus, research with these rats, mice, and birds, which likely comprises the overwhelming majority of vertebrate animals in research in the US, is not overseen by the USDA.

Does that mean rats, mice, and birds are not covered by federal animal welfare laws?

It depends on the funding! In fact, many rats, mice, and birds bred for research are covered by federal law.

Why?  Because, for federally-funded research, another federal regulation specifies the conditions for animal care, animal research, external oversight, and associated public transparency via a second federal agency. This includes, for example, university research funded by the National Institutes of Health, the National Science Foundation, or other federal agencies.

PHS and OLAW. The Health Research Extension Act (HREA; 1985) provides the statutory authority for the PHS Policy on Humane Care and Use of Laboratory Animals (PHS Policy), which applies to all PHS-funded research with live vertebrate animals.  In brief, such research must follow the National Research Council’s Guide for the Care and Use of Animals in Research (The Guide) (NRC, 2011).  Each institution receiving PHS funding for research with vertebrate animals is required to have an Assurance of Compliance (Assurance) with OLAW. The Assurance describes policies and procedures adopted by the institution in order to comply with PHS Policy.

The NIH website provides extensive information about PHS policy and OLAW.


Guide for the Care and Use of Laboratory Animals

Guide for the Care and Use of Laboratory Animals

Food and Drug Administration (FDA). Certain types of research with animals and most animal testing are also subject to oversight and regulation by the US FDA.

Part of the federal regulation governing animal research also requires that each institution engaged in research has a mechanism for ethical consideration, approval, oversight and monitoring of animal care and research. Thus, there are also oversight bodies at each institution that are charged with the approval, monitoring, and reporting of activities with animals.

Institutional Animal Care and Use Committees (IACUC). Animal research oversight at the institutional level is entrusted to an Institutional Animal Care and Use Committee or “IACUC.” The responsibilities of the IACUC are spelled out in the AWA regulations and the PHS policy. Read more about IACUC here: http://grants.nih.gov/grants/olaw/tutorial/iacuc.htm

What about rats, mice, and birds that are not in federally-funded research?

While privately-funded research is not subject to the AWA or PHS Policy, there are other mechanisms that are used to ensure standards of animal care and research review, such as voluntary accreditation of the institutions’ animal care program. Such research may also fall under FDA oversight and, as such, be required to follow PHS Policy.

Private accreditation.  An institution may choose to seek and maintain voluntary accreditation by a private agency, AAALAC, International (AAALAC). In the US, AAALAC accreditation depends on demonstrating compliance with the The Guide; thus, institutions that are not overseen by APHIS or OLAW may choose to be accredited and adopt the same standards for the care and treatment of research animals. Private accreditation for the care of captive animals is common across different kinds of facilities that house nonhuman animals, including those in research, but also in zoos and sanctuaries, who have their own accreditation organizations (e.g., American Zoological Association, AZA; Global Federation of Animal Sanctuaries, GFAS). Importantly, however, unlike oversight by a federal entity, voluntary accreditation does not provide a venue for public oversight and enforcement, nor does it allow for public transparency. For example, both USDA’s APHIS and PHS’s OLAW are responsive to public requests for investigation of facilities and records relating to oversight of those facilities. Private accreditation agencies do not provide public transparency of the accreditation process and/or inspection reports.

In Conclusion:

There are many sources of federal and local protection of animals in laboratories. Any research on AWA-covered species OR research that receives federal funding will be covered by federal laws aimed at ensuring laboratory animal welfare. Those laws provide for external oversight and for public transparency of records including, for example, inspection and investigation reports.

Most research is also covered by the IACUC system, which provides for oversight and, for many public institutions, another route of public transparency via state open records. Finally, many facilities– both public and private– maintain voluntary accreditation, which also should have a positive impact on animal welfare.

Speaking of Research

For more information about regulation, also see:

Update 5/24/16:  “New MOU Among NIH, USDA, and FDA.  NIH, USDA, and FDA have participated under a Memorandum of Understanding (MOU) Concerning Laboratory Animal Welfare for over 30 years. Each agency, operating under its own authority, has specific responsibilities for fostering proper animal care and welfare. This agreement sets forth a framework for reciprocal cooperation intended to enhance agency effectiveness while avoiding duplication of efforts in achieving required standards for the care and use of laboratory animals. The new MOU is available at: http://grants.nih.gov/grants/olaw/references/finalmou.htm.”


How zebrafish help advance cancer research

Do sharks get cancer?

Despite the widely touted myth that sharks do not develop cancer, fish of all species do occasionally develop spontaneous tumours. This is of course also true for the most common of laboratory fish, the zebrafish. In this article, I will give you a brief overview of how the unique properties of the zebrafish have been exploited by scientists to generate very useful models to study the molecular basis of various cancers.

The use of zebrafish in cancer biology goes right back to when scientists first started using them in the lab, at which point it was noticed that they spontaneously develop various kinds of tumours. However, using these naturally occurring malignancies to study cancer development is rather impractical – not only would you need a lot of fish due to the rarity of these cancers, but there would also be a lot of heterogeneity as to what kinds of tumours develop. This is clearly not ideal if you want to study the molecular basis and treatment options of one particular cancer.

From disease to model

Subsequently, carcinogenic chemicals were used to speed up the onset of cancer development. However, similar to using naturally occurring tumours, this strategy is not terribly useful for studying one particular kind of cancer, as the resulting tumours can still be very diverse(although some substances tend to always cause the same type). This approach is mostly used to identify cancer-causing chemicals during human and environmental safety testing.

To study one specific cancer type in detail, scientists started to create zebrafish carrying particular loss of function mutations (i.e. genes that lose activity due to a change), or overexpressing certain cancer-causing oncogenes (i.e. genes that cause cancer when they are overly active). Usually, this leads to the early development of only one – or at most a few – types of cancer. The first of these more specific models were acute lymphoblastic leukaemia (ALL) models, but nowadays there are models for cancers of various tissues, ranging from the brain to the pancreas.

Most of these mutant models were originally created using mutagenizing drugs followed by screening for a phenotype, but recently the research community has shifted to more targeted techniques. These make use of novel genome editing tools, such as the CRISPR-Cas9 system to switch off certain genes. The overexpression of specific genes on the other hand was usually achieved using proteins called transposases to integrate novel genetic information, but very recently the CRISPR-Cas9 system has also been tweaked to do the same.

Why study cancer in fish?

So why would anyone bother to go through this effort and do all this in fish, if we can just use the more closely related mice or rats? Apart from the lower expense and easier generation of large numbers of fish, the main reason why fish are used is that visualizing particular cells is much easier than in other organisms. This is mainly due to two factors: the existence of various transgenic fish lines in which a particular cell type is labelled, and the existence of transparent adult fish (the casper fish, as below).


Transparent fish like these Casper fish shown here allow researchers to track cells inside the body of adult fish much more easily than ever before

The ease of labelling specific cell types has been exploited elegantly for studying the clonal expansion of cancer cells that drives tumor growth in vivo as it happens, as well for the study of cancer metastases. Now that adult transparent zebrafish have enabled even easier in vivo imaging, the approach has been used successfully to visualize the process by which metastases arise and cancer cells distribute throughout the body.

Understanding the origins of melanoma

A recent paper from Charles Kaufman of the Harvard Stem Cell Institute and colleagues nicely illustrates how these advantages can be very powerful indeed. In this paper published in Science magazine, the researchers used a zebrafish melanoma model that they had developed a few years earlier which expresses gene variants associated with the cancer in humans, and combined this with a newly developed transgenic zebrafish line, in which cells expressing a gene known as Crestin, which is involved in early neural development , are labelled in green. The Crestin gene is normally not expressed in adult humans, but is switched on again in melanomas. This is also why this combination is interesting; emerging melanoma cells will re-express the normally silent gene and be labelled fluorescently.

This method allowed the researchers to track melanoma development from the very first tumour cell to the macroscopically visible tumour comprised of millions of cells. The very early changes that have to occur for cancer to develop can now be studied at much greater detail than before, as these very early tumorigenic cells are extremely hard (or completely impossible) to distinguish from normal cells if they are not labelled. In this specific case the researchers identified the activation of several gene pathways that are usually involved in neural crest development in the embryo as key events in the initiation of melanoma, and believe that their findings could lead to a new genetic test for suspicious moles in patients. Their work suggests a model of cancer development where normal tissue becomes primed for cancer when oncogenes are activated and tumour suppressor genes are silenced or lost, but where cancer develops only when a cell in the tissue reverts to a more primitive, embryonic state and starts dividing.

This paper increased our understanding of the underlying biology of the very early stages of tumour development, and a detailed understanding of these early steps might be very important when developing preventative or therapeutic drugs.

Image: Kaufman, C.K., et al, 2016. A zebrafish melanoma model reveals emergence of neural crest identity during melanoma initiation. Science, 351(6272), p.aad2197. DOI: 10.1126/science.aad2197

Image: Kaufman, C.K., et al, 2016. A zebrafish melanoma model reveals emergence of neural crest identity during melanoma initiation. Science, 351(6272), p.aad2197. DOI: 10.1126/science.aad2197

In summary, the field of zebrafish cancer biology has made great advances in the last decade and will continue to do so with the increasing popularity of genome editing techniques. The easy visualization of particular cell types leads to distinct advantages of using zebrafish, particularly for the study of metastases and the very early stages of cancer development.

Jan Botthof

Kaufman, C.K., Mosimann, C., Fan, Z.P., Yang, S., Thomas, A.J., Ablain, J., Tan, J.L., Fogley, R.D., van Rooijen, E., Hagedorn, E.J. and Ciarlo, C., 2016. A zebrafish melanoma model reveals emergence of neural crest identity during melanoma initiation. Science, 351(6272), p.aad2197. DOI: 10.1126/science.aad2197