Sleep inducing hormone puts breast cancer cells to rest  

It’s pretty easy to connect the dots between a lack of sleep and an increased risk of a deadly car crash. But what about an increased risk of cancer? A 2012 study of 101 women newly diagnosed with breast cancer found that those with inadequate sleep were more likely to have more aggressive tumors. Though the results of this survey were statistically significant, the biological connection between sleep and breast cancer is not well understood.

melatonin

Melatonin, the sleep hormone, may help fight cancer. Image Credit

Now, a report in Genes and Cancer by a Michigan State University research team shows that the interplay between melatonin, a hormone involved in sleep-wake cycles, and breast cancer stem cells may provide an explanation. And, more importantly, the study points to melatonin’s potential use as a cancer therapeutic.

Mammospheres: cancer in a more natural environment
To carry out their lab experiments, the researchers grew breast cancer cells into three-dimensional aggregates, called mammospheres, that resemble the tumor cell composition seen in an actual tumor in the body. This cell mix includes breast cancer stem cells which are thought to drive the uncontrolled tumor growth and reccurrence. David Arnosti, a MSU professor and co-author on the study, used a helpful analogy in a university press release to explain the importance of using the mammosphere technique:

“You can watch bears in the zoo, but you only understand bear behavior by seeing them in the wild. Similarly, understanding the expression of genes in their natural environment reveals how they interact in disease settings. That’s what is so special about this work.”

 

Melatonin fighting cancer cells via their stem cell-like properties
The cancer cells used in this study are also categorized as so-called estrogen receptor (ER) -positive cells. This classification means that the cancer growth is largely stimulated by the hormone estrogen.  The first round of experiments analyzed melatonin’s effects on estrogen’s ability to increase the growth and size of the mammospheres. The team also tested Bisphenol A (BPA), a chemical used in the plastics industry that mimics estrogen’s effects. While estrogen or BPA alone caused a large increase in mammosphere size and number, addition of melatonin stunted these effects.

Next, the team went deeper and looked at melatonin’s impact from a genes and proteins perspective. Estrogen is a steroid hormone that acts by passing through the cell wall and binding to the estrogen receptor inside the cell. Once bound by estrogen, the receptor travels to a cell’s nucleus and binds particular regions of DNA which can activate genes. One of those activated genes is responsible for producing OCT4, a protein that plays a critical role in a stem cell’s ability to indefinitely makes copies of itself and to maintain its unspecialized, stem cell state. This cellular pathway is how estrogen helps drives the growth of ER-positive breast cancer cells. The researchers showed that estrogen- and BPA-stimulated binding of the estrogen receptor to the OCT4 gene in the mammospheres was inhibited when melatonin was added to the cells.

Melatonin: putting cancer stems to bed?
Putting these observations together, melatonin appears to suppress breast tumor growth by directing inhibiting genes responsible for driving the stem cell-like properties of the breast cancer stem cells within the mammosphere. Melatonin is produced by the brain’s pineal gland which is only active at night. Once released, melatonin helps induce sleep. So a disrupted sleep pattern, like insomnia, would reduce melatonin levels and as a consequence the block on estrogen driven cancer growth is removed. ­

James Trosko, whose MSU lab perfected the mammosphere technique, sees these breast cancer results in a larger perspective:

“This work establishes the principal by which cancer stem cell growth may be regulated by natural hormones, and provides an important new technique to screen chemicals for cancer-promoting effects, as well as identify potential new drugs for use in the clinic.”

 

Keep in mind that these are very preliminary studies and more work is needed before a potential clinical application sees the light of day. In the meantime, have a good day and get a good night’s sleep.

 

 

New stem cell could offer new ways to study birth defects

tony-parenti-stem-cell-2

Tony Parenti, MSU Ph.D student in cell and molecular biology

You never know what you are going to find in the trash. For a group of intrepid researchers at Michigan State University their discovery could lead to new ways of studying birth defects and other reproductive problems. Because what they found in what’s normally considered cellular trash was a new kind of stem cell.

The cell is called an induced extraembryonic endoderm stem (iXEN) cell. The team’s findings are reported in the journal Stem Cell Reports and here’s how lead author Tony Parenti described what they found:

“Other scientists may have seen these cells before, but they were considered to be defective, or cancer-like. Rather than ignore these cells that have been mislabeled as waste byproducts, we found gold in the garbage.”

Here’s the backstory to this discovery. For years researchers have considered embryonic stem cells as the “gold standard” for pluripotent cells, the kind that can be differentiated, or changed, into all kinds of cell in the body.

But studies in mice show that in addition to creating these pluripotent stem cells, the mouse embryo also produces extraembryonic endoderm or XEN cells. For a long time it was believed the gene expression of XEN cells affected the pluripotent stem cells, but the XEN cells were usually thought to be cancer-like, something that occurred as a byproduct of the developing embryo.

Searching through the trash

And that’s how things stayed until the research team at MSU noticed a bunch of XEN-like cells showing up every time they created induced pluripotent stem (iPS) cells – a kind of man-made equivalent of embryonic cells with the ability to turn into any other kind of cell but derived in a different way, reprogrammed from adult cells.

So they set out to see how important these, what they called induced or iXEN, cells were to the development of iPS cells. The researchers took  adult mouse cells and reprogrammed them into iPS cells and noticed colonies of iXEN cells in these cultures.

The first goal was to make sure these iXEN cells weren’t cancer-causing, as many researchers believed. This took six months but at the end of it not only were they able to demonstrate that the cells aren’t cancer-causing in a cell culture dish, but that they are a new type of stem cell.

Next step was to see how important endodermal genes are in the formation of iXEN cells. They found that decreasing endodermal gene expression led to a two-fold decrease in the number of iXEN cells and a significant increase in the number of iPS cells.

Competitors not collaborators

They concluded that the parallel pathways that generate pluripotent and XEN cells are in competition with each other and not in support of each other during reprogramming. By suppressing one they were able to boost the other. To their delight they had stumbled on a more efficient way of creating iPS cells.

While the discovery of a new kind of stem cell is always exciting there’s a catch to this; we still don’t know if XEN cells are found in humans. But this discovery gives the researchers additional tools to try and find the answer to that question.

Amy Ralston, a co-author of the study, said in a news release:

“It’s a missing tool that we don’t have yet. It’s true that XEN cells have characteristics that pluripotent stem cells do not have. Because of those traits, iXEN cells can shed light on reproductive diseases. If we can continue to unlock the secrets of iXEN cells, we may be able to improve induced pluripotent stem cell quality and lay the groundwork for future research on tissues that protect and nourish the human embryo.”

Normally the discovery of anything new, particularly when it over turns a long-held belief, is met with a degree of healthy skepticism at first. In science that’s a good thing. We all remember the eager way that STAP stem cells were hailed by many as a new way to create pluripotent stem cells until the research was discredited. But so far the Twitterverse and media outlets seems to share in the excitement about this discovery.