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Natural products, or compounds isolated from plants/microorganisms, have been used as herbal medicines throughout human history. These compounds have many measurable effects. In fact, ⅓ of the top selling pharmaceuticals are natural products or their derivatives. Many antibiotics were discovered from screening these compounds and recently have shown efficacy against cancer. This discovery has become an exciting topic and is often talked about in the news.
Microbial products have already been approved and used in the treatment of cancer. Actinomycin D was first approved from the treatment of Wilms tumor in pediatric cancer. However, like many chemotherapies, treatment results in severe side effects, such as immune cell suppression, vomiting, and hair loss. The real intriguing question is, can cancer be combatted using compounds isolated from food? Are there compounds that will only kill tumor cells and not healthy cells? And can these be used effectively as a cancer therapy? The answer to these questions is, maybe?
The anti-cancer mechanism of these natural products depend on the compound itself. The most widely studied plant based natural product for cancer research is curcumin. Curcumin is a compound isolated from tumeric and has been used as an herbal supplement in chinese medicine, as well as, in food coloring and flavoring. Curcumin works through inducing autophagy and cell death. It has been shown to induce cell death specifically in cancer cells, leaving healthy tissue unharmed. A similar mechanism is true for resveratrol, a compound isolated from grapes and can also been found in red wine. A slew of traditional chinese medicines isolated from plants have anti-cancer effects through inhibiting well known cancer causing proteins. This includes polyphenols’ ability to inhibit p-53, which is associated with colon, pancreatic, and lung cancer. Other natural compounds can be used in combination with chemotherapy, as they assist in their mechanism. One of the ways cancer cells resist chemotherapy induced death is through utilizing the P-gp protein. P-gp is a protein on the surface of cells that can pump unwanted materials out. Some cancers cells increase the number of P-gp to pump out the chemotherapy. Natural products have been shown to inhibit this protein and therefore, when used in combination with chemotherapy, can increase their efficacy.
There are some drawbacks to using natural products for cancer treatment. One drawback is that large doses of these drugs are needed to see an anti-cancer effect. In fact, 3.6 g of curcumin per day is needed to obtain measurable serum levels of the drug. And this is not unique to curcumin, other common natural products such as polyphenols and flavonoids also required high daily doses to see levels in the blood as well. This is due to the lipophilic nature of many natural compounds. To combat this issue, scientists have encapsulated curcumin, and other natural products, into particle delivery systems in order to increase their biological activity. However, encapsulating the particles could result in different issues. Delivering the particles using a oral administration would be difficult using a particle delivery system. An i.v. route of administration would probably be required, limiting the ease of delivery. Another issue could be in the particles themselves. Using particles could affect the overall safety profile. More investigating needs to be done before natural products can be used as a first line anti-cancer treatment. However, their availability and low toxicity profile make them an ideal candidate. If more research continues, it is possible that in the future, we will have safe drugs derived from plants that specifically kill tumor cells.
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