Myths and Misconceptions: Sharks don’t get cancer

With Shark Week just past, it seemed fitting to delve into the mysterious world of the super-fish that haunts our summer beach trips. There’s something about sharks that elicits a potent mixture of fear and fascination in us. Perhaps it’s their impressive rows of razor-edged teeth. Maybe it’s their sheer power and speed, slicing through the water. I like to think it’s their beady black eyes – fathomless abysses signifying five letters. D-E-A-T-H. It’s like sharks are better than us. Like we know deep down, if they were bipedal and land-dwelling, they’d dominate us. Case in point: everyone knows sharks are immune to cancer, right?

 

Well, not quite right. While sharks are pretty damn awesome, they’re not so awesome that they can escape the Big C. A study over ten years ago found that sharks can fall victim to at least 40 different tumour types, including 12 malignant kinds. Having said this, it is believed that sharks display lower rates of cancer and disease in general. One possible explanation for this resides in their oceanic habitat: they live in a comparatively uncontaminated environment. This means that their exposure to carcinogenic pollutants is lower. Realistically, we aren’t well informed about shark cancer rates due to the lack of scientific, systematic studies in this area.

 

So, where did this myth come from? It turns out that its origins lie in anti-cancer research dating back to the 70s. Scientists noticed that cartilage, the connective tissue found in places like your nose, could potentially inhibit the formation of new blood vessels. We call this blood vessel formation “angiogenesis”, and it’s an essential component for the growth of cancerous tumours. Interestingly, a shark’s skeleton is composed entirely of this cartilage stuff. This led a crazy, mad scientist to believe that cartilage skeletons were the reason sharks had such low incidence rates of cancer. He was so convinced of the idea that he advocated for the use of shark cartilage as an oral treatment for human cancer. He even wrote a book about it; Sharks Don’t Get Cancer: How Shark Cartilage Could Save Your Life. Unsurprisingly, this sensationalist new “cure for cancer,” backed up by a single, shoddy scientific study, garnered a fair amount of media attention.

 

Since then, the multimillion dollar shark cartilage market has emerged, selling vulnerable cancer patients a “cure” that has been scientifically disproven by several clinical trials. What’s more, shark populations worldwide have been decimated. These slow-growing warriors of the ocean can’t withstand such intense fishing pressure. All this ecological devastation for a pill that doesn’t even work.

 

This myth came as a bit of a shock to me, as I’d just been explaining to a friend recently why sharks freak me out so much. “Yeah, but dude, sharks can’t get cancer! They’re like super-evolved killing machines!” But hey, that’s the great thing about science. It bestows upon us facts and wisdom that enlighten and enrich our lives. Now both you and I are enlightened: sharks aren’t invincible killing machines. In fact, humans are the ruthless killing machines in this story. Just like us, sharks too can suffer the misfortune of cancer. Let’s show our fearsome fishy friends a bit of respect, and make sure we look after them.