The thing about sharks and cancer is interesting - because it seems sharks may rarely get cancer!

Sharks have an unusual immune system, because they don't have bones.  People and many other creatures produce immune cells in their bone marrow.  Instead of the bone marrow, sharks apparently use a special organ, the epigonal organ, to produce immune cells. The shark immune system eliminates some harmful compounds very fast. There's a marine laboratory that is trying to figure out how the shark immune system is so effective - perhaps this will lead to a cancer treatment for humans. 

Instead of bones, sharks have a skeleton made of cartilage instead!  Their swimming muscles attach to their very thick, tough skin instead of being attached to bones. 

Scientists aren't sure that sharks get cancer at a lower rate than other animals, because no systematic studies have been done.  The idea that they get cancer less often is based on people rarely finding tumors in sharks that are caught. 

Cartilage in general contains a compound that inhibits the formation of blood vessels, because cartilage doesn't have blood vessels. Many tumors have to induce the body to form new blood vessels in order to survive.  So some cancer patients take shark cartilage, hoping it will be anti-cancer. 

However, eating the cartilage doesn't work because the compound is destroyed by the digestive system.  It would at least have to get into the bloodstream or be applied directly to a tumor, to work.  Shark cartilage supplements have been studied in clinical trials, but haven't been particularly helpful against cancer.  There's a liquid shark cartilage extract that may have anti-cancer properties. 

Shark cartilage may actually be toxic, possibly causing Alzheimer's and ALS. 

So that's the actual reality of the shark cartilage for cancer stuff - somewhere between "magic cure for cancer" and "bogus fantasy".  As with many alternative-medicine treatments, it's based on a good idea that might eventually result in an effective treatment, after a lot of research. 

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I know, but a tumor in a shark is almost irrelevant to the supposed anticancer properties of shark cartilage.

So sharks do get cancer - but the next question is, do they only rarely get cancer? 

That seems likely, and that is still very interesting and might lead to human cancer treatments. 

Probably nothing except for dying totally prevents cancer.  But there are still cancer treatments. 

Hi Laura,

You'd be interested in the Blind Mole Rat also.

I just completed a 1st year Biology course at MIT. (Sounds good doesn't it, but I did it through Edx, and instead of getting 2 or 3 hours to complete an exam you get a whole week.) You can learn a lot from the course and it's free.

I mention Edx because it covers everything you want to know about cells. And has a whole series of lectures on cancer. 

How interesting Leveni!  According to your wikipedia link

After a specific amount of time (within 3 days according to a study conducted at the University of Rochester), the cells in blind mole rats release interferon-beta (which the immune system normally uses to counter viruses) in response to over-proliferation of cells caused by the suppression of apoptosis. In this case, the interferon-beta triggers cells to undergo necrosis, and this mechanism also kills cancer cells in blind mole rats. Because of tumor suppression mechanisms such as this, blind mole rats and other spalacids are resistant to cancer.


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