Paclitaxel- an Example of the Intricate Connection Between Human Health and the Natural World

I've said it before and I will continue to say it- plants are just the coolest. They are complex life that can feed themselves, fend off disease, and dodge predators all while being immobile- that alone makes them pretty awesome. They're also crazy diverse, yet share many core molecular mechanisms that keep them alive, like respiration and photosynthesis.

And yes I might be a little biased because of my houseplant addiction- but trust me, this goes well beyond the green goddess energy that plants contribute to our homes.

I admit I don't know who this girl is- but I love the energy, and this is really good starting material for this plant-themed post!

Plants also do a whole lot more for us then we give them credit for. If you're reading this sitting at a table in a coffee shop, for instance, even if there are no actual living plants around you, you are surrounded by the products of plants. That table you're sitting at? Made out of wood, which comes from the bark and stem on trees (unless it's plastic which it could be but humor me here). The coffee you're drinking? Brewed with coffee beans, picked from a coffee plant, then carefully roasted for your tasting pleasure. Maybe there's a soft cushion on the chair you're sitting on? That fabric is (hopefully) made out of cotton fibers, which serve to protect seeds on cotton plants in the wild. Even if there's no cushion on your chair, or if it's made of synthetic fiber, I'll bet your underwear or your shirt or your jeans are made of natural cotton fibers. If you're wearing shoes (which, if you're at a coffee shop, let's hope), there's probably some sort of rubber on that shoe to protect your feet, and that rubber is either derived from or modeled after a substance derived from the inside of tropical and subtropical trees.

From Encyclopedia Brittannica- rubber tree tapped for latex. Seriously, plants are so wild with the variety of different chemicals, compounds, and materials they can synthesize!

In case I haven't driven the point home enough- plants and plant products are everywhere.

I could go on, and on, and on (just ask my fiancé) about how interesting and bizarre plants are- but what I want to get into today is a, perhaps, unexpected way that plants make an impact on our lives. Plants and plant products make up a huge part of the world around us- but they also have the potential to help with the world inside us. That is, plants are intricately connected to human health.

Which, if you really think about it, isn't a huge shocker. I'm sure you know someone who is allergic to peanuts? Which are seeds for peanut plants. Or maybe someone who has seasonal allergies? Who probably gets the sniffles in the spring as a reaction to pollen in the air, which is essentially a vessel of transport for plant sperm. So just like plants can make our bodies react with sneezes or sniffles or coughs- plants can help our bodies boost up our immune systems, and fight infections, and overall function on a higher level than they would otherwise.

So, without further ado, we're going to talk about one of my favorite plant stories- the story of paclitaxel.

This story starts when, back in the 1960s, the National Cancer Institute (NCI) wanted to find some new anti-tumor compounds, or things that they thought might be helpful at treating cancer. And, they thought plants might be a good place to start this hunt. And when I say "treating cancer", that can mean anything from stopping tumor progression to increasing cancer patient lifespan to decreasing the rate at which cancer cells replicate. So really, they were looking for anything in plants that might help cancer patients live longer with or beat their cancer altogether.

Image courtesy of Morgan-Keller Constriction- the National Cancer Institute research lab located in Frederick, MD.

One of the scientists that went on this search for the NCI was Dr. Arthur Barclay, a botanist working at the USDA in Maryland in the New Crops Research Branch. Dr. Barclay wasn't working on cancer, or even medicinal plants- most of his work up until this point was focused on looking for new oilseed crops and collecting samples from South Africa and the South Western United States. But he went on this trip, where around 35,000 plant specimens were collected, and one of the plants he happened to collect bark from was the Pacific yew.

The Pacific yew actually has a somewhat rough history with people, and its relatives in England are known as "graveyard trees", since nearly every part of the tree is very poisonous. Lucky for us, however, Dr. Barclay braved the collection of bark and stem from this tree and sent the samples back to scientists at Research Triangle Park in North Carolina for testing to see if, along with all the other thousands of plant samples collected, they could be useful in helping with the treatment of cancer patients.

Pacific Yew tree, with lots of crazy-bright red berries!

These plant tissues were broken up to create crude cell extracts, and cancer cells were exposed to these extracts to determine if anything from the various plant cells could effectively fight cancer growth. The Pacific Yew was one of the extracts that appeared to work, so chemists Monroe Wall and Mansukh Wani went about identifying what compound in the Pacific Yew extract was responsible for this activity.

And this lead them to paclitaxel.

Turns out, the way paclitaxel fights cancer cells is simply stopping cell division. Cancer is, by definition, the uncontrollable growth of cells, specifically where they aren't supposed to be which can lead to them moving around in a persons body (you might have heard this called "metastatic" cancer). Paclitaxel is an antimitotic agent, which means it inhibits mitosis- the process by which most of the cells in our bodies divide. It does this by keeping microtubules from attaching to chromosomes during metaphase, which keeps the chromosomes from separating properly.

Courtesy of Wikipedia- a general idea of how the mitotic checkpoint works. The red line with a bar at the end is the biology way of saying "Inhibits", so the mitotic checkpoint (if it's triggered, like if paclitaxel is present) will inhibit the transition from metaphase to anaphase.

Cells have all sorts of checkpoints that they go through during mitosis to make sure everything is running smoothly, and this disruption means the cells cannot get past their checkpoint. This leads to cell death in the form of apoptosis, which as the name implies, means the cells die by bursting open (or, popping!).

So there you have it, plants can help fight cancer, which is just another reason on a very long list as to why plants are so awesome. And paclitaxel is not the only example- apparently Dr. Monroe Wall was such a big proponent of using natural chemicals for disease treatment, he found another compound called camptothecin, which I learned about as I was writing this post! Absolutely wild- science definitely has a way of keeping you on your toes!

With that in mind, keep being curious y'all, and hopefully this is the start of some more consistent content here soon :)