Early animal research into blocking breast cancer

Thursday January 2 2014

"'An injection that prevents breast cancer is being developed by scientists," is the news on the Mail Online website.

This news seems a heartening way to start the year, but a caveat is that the research is in the very early stages – as yet only tested in mice.

The researchers were interested in a type of breast cancer known as ductal carcinoma in situ (DCIS).

In DCIS the cancerous cells are contained within the ducts in the breast, and not spread to other breast tissue. The problem with DCIS is that it is currently impossible to predict whether the cancer will remain inside the duct (so will not require treatment) or become invasive and spread into other parts of the breast. This means that some women with DCIS will undergo invasive treatment unnecessarily.

This research involved genetically engineered mice designed to develop DCIS-like tumours that eventually spread. They found that a gene called Hox1A seemed to be involved in stimulating the growth of the DCIS-like tumours. They then went on to use an injection of specially designed nanoparticles into the mammary tissue, designed to "turn-off" the Hox1A gene.

They found that the injection stopped three-quarters of the mice from developing tumours at 21 weeks. However, the researchers don’t yet know if the tumours might develop later in these mice, or are stopped completely.

These findings are definitely worth more investigation, but, as yet, implications for human breast cancer prevention or treatment are still uncertain.

Where did the story come from?

The study was carried out by researchers from Harvard University and other research institutions in the US. It was funded by the US Department of Defense and the Wyss Institute for Biologically Inspired Engineering. The study was published in the peer-reviewed journal Science Translational Medicine.

The Mail Online’s headline and photos of women (including Angelina Jolie) may lead people to believe that this research is more advanced than it is. As yet, this technique has only been tested in mice, so its effects in humans are not known. 

So despite the Mail Online’s claims, it is far too early to know whether it will “spare thousands of women the trauma of surgery”. (The injection was also not given intravenously as the Mail Online suggests, it was injected directly into the mice’s mammary tissue.)

What kind of research was this?

This was laboratory and animal research aiming to understand more about which genes are involved in the development of breast tumours and to see if blocking these genes could stop tumour progression.

This early stage research was carried out mainly in mice, but researchers hope that their findings will be applicable in humans. The genetically engineered mice they used start to show abnormal mammary cells at about 12 weeks of age, before developing growths that are contained within the mammary glands at about 16 weeks, and then progress to invasive tumours at 20 weeks of age.

At the point where the growths are contained within the mammary glands, they resemble ductal carcinoma in situ (DCIS) in humans. DCIS is a very early stage of breast cancer where there are abnormal cancer cells in the breast ducts, but the cancer has not spread out into the breast tissue. It is estimated that up to half of people with DCIS will go on to develop invasive breast cancer. This is where the cancer has spread into the breast tissue with potential for spread to the lymph nodes and other tissues and organs of the body. In the remainder of people the abnormal cells will remain confined to the breast ducts and they will never develop invasive breast cancer.

The difficulty for scientists and medical professionals is that they can’t tell in advance whether DCIS will progress to invasive cancer or will be the non-aggressive kind that remains confined to the ducts. So currently all women with DCIS are assumed to be at risk of invasive breast cancer and are offered treatment as a precaution, such as surgery or radiation. Doctors would like to be able to use less invasive treatments for DCIS that would still be effective, and also have fewer side effects. The current research aimed to test an approach that could eventually provide a way to do this.

What did the research involve?

The researchers first identified which genes looked like they were involved in the development of breast tumours. They started by using computer software to analyse and model how different genes interact and affect each other’s activity. They did this for normal mouse tissues, and also for the mammary (breast) glands of genetically engineered mice which develop mammary tumours.

In order to identify the key genes which are involved in the earliest stages of tumour development, the researchers looked at what genetic changes occur in the genetically engineered mice’s mammary glands at eight weeks old. Once they found a gene that looked like it might be involved in starting tumour development, they studied this gene more closely. They looked at whether this gene was also more active in human breast cancer cells than in normal human breast cells using information on gene activity from tissue samples from people with breast cancer. This included DCIS and other forms of breast cancer.

Then, they looked at what happened if they stopped this gene from working in the genetically engineered mice’s mammary tumour cells in the lab, in the living mice, and in human breast cancer cells in the lab. They did this using what are called “small interfering RNAs” or siRNAs. These are small pieces of genetic material that mimic part of the genetic code of the gene being targeted. They stop the gene from working by blocking that specific gene’s “messages” to the protein making machinery of the cell.

In the genetically engineered mice, they injected siRNAs targeting HoxA1 into the mammary glands twice a week from the age of 12 weeks, for a total of nine weeks. This siRNA was packed into tiny particles – nanoparticles – surrounded by a layer of fatty molecules. Injecting the siRNAs into the mammary tissue reduces the chance of the treatment spreading through the body and having an effect in other, healthy, tissues. They also injected some mice with an inactive control solution in the same way, and compared the effects.

What were the basic results?

The researchers found that a gene called HoxA1 seemed to be one of the first genes involved in the development of abnormal mammary cells in the genetically engineered mice which develop mammary tumours. They also found that this gene was more active in some samples of human breast cancer tissue (DCIS and other kinds of breast cancer) than in normal human breast tissue. This suggested that it might well be playing a role in human breast cancer development.

When researchers stopped this gene from working in the genetically engineered mice’s mammary tumour cells and human breast cancer cells in the lab, the tumour cells behaved more like normal mammary cells and less like tumour cells. This meant that the tumour cells divided less. They also began to form organised balls of tissue with hollow centres like normal cells, rather than the usual disorganised solid bundles of cells that tumour cells form. 

Stopping HoxA1 from working in genetically engineered mice’s mammary glands seemed to slow the development of tumours.

All of the mice given the inactive control treatment developed mammary tumours by 21 weeks of age, but only a quarter of the mice given the HoxA1-blocking treatment developed tumours at this age.

At 21 weeks the mice given the HoxA1-blocking treatment did still have abnormal cells in their mammary glands, but these had not formed tumours. The mice were not assessed at later ages, so the researchers did not know whether these abnormal cells could eventually develop into tumours. The treatment did not appear to cause obvious side effects such as damage to the mice’s mammary tissues or weight loss.

How did the researchers interpret the results?

The researchers concluded that the approach they used could successfully identify genes involved in human breast cancer development, and that these could be potential targets for new minimally invasive siRNA treatments. They said that the same approach could potentially be used to identify genes involved in other types of tumour.


This research has identified the HoxA1 gene as potentially playing a role in human breast cancer. It has also shown that interfering with this gene using siRNA can slow tumour formation in genetically engineered mice that usually develop tumours in the mammary glands. The same technique was found to make human breast cancer cells behave more like normal human breast cells in the lab.

Though the research is related to better understanding the development and progression of ductal carcinoma in situ (DCIS) in humans, study is at a very early stage. The researchers themselves note that they will need to carry out more research before this finding could potentially be tested in humans. For example, they also need to study the long-term effects of siRNA treatment in mice – for example, whether the treatment just slows rather than stops tumour formation.

They also need to understand more about the role of HoxA1 in human breast cancer, as they have only limited information so far. Should these additional experiments continue to suggest that this approach could be promising for human use, the researchers will also need to work out how it might be used.

For example, would it be effective in women who have not yet developed DCIS or invasive breast cancer but who are considered to be at high risk for these conditions? Or could it also be used as part of the treatment for DCIS or breast cancer?

However, these questions are likely to remain unanswered for some time. We definitely don’t know for sure whether this treatment will “spare thousands of women the trauma of surgery”.

Despite these issues, this research shows the continuing efforts of researchers to develop new ways to prevent and treat disease using new approaches such as siRNAs.

Analysis by Bazian
Edited by NHS Website