In some ways, each one of our cells is a lot like us. Just as each person fulfills their specific niche, each cell plays an important role in keeping our bodies functioning as a whole. But even structurally, there are similarities. For our bodies to work properly, we have different organs that perform specific functions, making us whole. The heart pumps blood, circulating oxygen and essential nutrients throughout our body. Our liver helps filter our blood, keeping it clean so we don’t spread harmful material. The stomach helps us digest our food, breaking it down and providing us with nutrients for energy.

There’s what’s called the “plasma membrane”; it’s essentially the skin of the cell. It keeps everything together while also keeping harmful things out. The nucleus is like the brain of the cell. It contains DNA, which tells the cell what to do and when to do it. Then there’s the mitochondria. The mitochondria are organelles that break down nutrients and provide the cell with energy. In that sense, they’re sort of like the stomach of the cell. Our cells actually have a lot of little stomachs, so maybe in that way, they’re more like a cow… Either way, they’re important.

Energy production is really important for cancer. Just think about how important it is for us. Having energy is what lets us actually do… things. Going on hikes, jogs, or walking around the block all use energy. So we need to eat and fuel ourselves to do that. It’s the same for our cells. To migrate, divide, and spread throughout the body, they also need energy. But that goes for all cells, so why is cancer so different?

So, having more energy allows a cancerous cell to move around more or divide more quickly than normal cells. As the stomach of the cell, mitochondria supply the cell with energy. That makes them essential for a cancer to be a cancer, helping meet the high-energy needs of a cancer cell. More mitochondria means more energy produced.

Our cells only have so many mitochondria. They need to make their own mitochondria, much like how we have to make our own organs. Unlike us, they can keep making organelles, even once they’re mature. But that takes energy, and more energy spent on mitochondria means less time dividing. On top of that, mitochondria can be damaged. Once they’re damaged and no longer producing energy, mitochondria can be destroyed and recycled, but that’s one less organelle producing energy.

That’s right, cancer can actually take healthy organelles and use them for itself. By stealing mitochondria, cancer can access energy-producing organelles without spending the effort to make them. They can also take advantage of differences between mitochondria from different cells. The mitochondria that different cells carry can vary pretty dramatically. It depends on the type of cell and the environment they’re grown in. Cells in different organs are exposed to different nutrients, so their mitochondria need to account for that. But each cell type also has different energy costs, so one cell might have more mitochondria, or more efficient mitochondria to meet those needs. By selectively taking mitochondria from one cell over another, cancer cells can obtain more efficient mitochondria, giving them a notable advantage. Nerves, for example, have highly active mitochondria, and they’re good at metabolizing certain nutrients. An excellent paper by G. Hoover and colleagues showed that cancer cells can steal mitochondria from nerves and use them to supply themselves with energy. They also showed that stealing these mitochondria made the cancer more aggressive, giving it energy for rapid growth and migration.

This is a fascinating discovery, and it means a couple of things. For one, it shows that cancer doesn’t work on its own. It profits from its surroundings and can adapt to its environment. That adaptability is an essential part of cancer. Now we can see how cancer adapts by interacting directly with our healthy cells. Not only that, but it also shows that these interactions aren’t passive. Their theft of organelles actively made the cancer more aggressive. By itself, that’s a really important finding, but we also have to consider the cells that mitochondria are stolen from. More mitochondria for cancer means less energy for healthy cells, which can impair their function and affect their survival. In turn, that means less competition for the cancer. So really, cancer gets more energy while simultaneously hurting healthy cells… The good part is that now we know, and understanding it further will hopefully open the door to new therapies that take advantage of it, maybe even putting a stop to it.

There are a whole lot of other cells that cancer can steal from, too. Each has unique mitochondria and variation in energy production. In some cases, the purpose of the stolen mitochondria hasn’t been determined, but in many, and certainly for nerves, it helps supply the cancer with energy, making it more aggressive. In some ways, it’s just like a black market: stealing organs and using them for itself. It’s morbid, but it’s an exciting example of just how complex cancer can be. It doesn’t stand alone as a disease; it thrives off our healthy cells, using them for resources. Mitochondrial transfer is a recent discovery and a growing topic in cancer research. Because of that, a lot is being done to figure out exactly how mitochondria are transferred and why. This work could open the door to new strategies that take advantage of this phenomenon, using it to get back at cancer instead.

I hope you learned a little something this week, but next week the mitochondrial transfer continues (along with other topics) as we talk about how cells can escape immune cells. A little foreshadowing: it turns out it’s not always about energy…

See you next week!

Today, I’m excited to announce that this is the first issue featuring a photo taken by a graduate student at the Cross Cancer Institute, PhD Candidate Rana Karimpour. One of my goals with this project is to shed a little bit more light on what goes on in research; part of that is featuring actual images taken by researchers. Today, with Rana’s help, we get to do that. Rana studies how changes in the structure of the cell, the physical organization of DNA, and in mitochondria influence cancer and age-related disease. The image features mitochondria, in yellow, inside the cell. These pictures were taken with super-resolution microscopy, a technique so advanced that we can see details that are only a few billionths of a metre, giving researchers a much clearer picture than conventional microscopes. In this picture, there is a scale bar at the bottom right, showing a width in microns, which is a millionth of a metre. You’ll be able to read more about super-resolution microscopy in a few weeks, so keep an eye out for that issue! Unfortunately, cover photos aren’t included in the email newsletters, but if you click “Read Online" in the top right-hand corner of this email, you can see more mitochondria in all their majesty.

Again, thank you to Rana for sharing her image with me and letting me share it with all of you.

If you missed last week’s letter, you can read “Say ‘Cheese!’” to learn a little more about how we take images of cancer and use them for diagnosis and treatment.