Taking a bite out of shark cartilage - an evaluation of shark cartilage as an alternative therapy for the prevention and cure of cancer

A tremendous amount of marketing has accompanied the sale of shark cartilage as a preventive and cure for cancer. Do the claims far outstrip the evidence?

A Tale of Two Wills

Recently I heard a fascinating story about a man we will call Wilhelm, a German POW imprisoned in the Arizona desert during World War II. He stole a local map and was elated to find that there was a river close to the prison camp. Armed with this knowledge, Wilhelm eagerly recruited several other prisoners with the promise of freedom. They invested a great deal of time and energy digging a tunnel and constructing a small boat that would carry them down the river to Mexico. There was some reason to believe that the plan might succeed. The river was only a few minutes from the tunnel opening, and Mexico was only a few miles away. Finally, they finished their tunnel and escaped into the desert night with Wilhelm leading them toward the river.

The saga of Dr. William Lane and the shark-cartilage cure for cancer parallels this story to a large extent. Lane stumbled onto an interesting idea that held out the promise of freedom from the pain and suffering of cancer. The plan was not without some merit, for it was based on sound scientific research. Studies done at Harvard, MIT, and elsewhere had shown that under certain conditions cartilage sometimes prevented cancer from spreading in laboratory animals (Brem and Folkman 1975). Just as Wilhelm had little trouble convincing hopeless prisoners that his plan was workable, so Lane was able to convince cancer victims that shark cartilage offered them some hope.

Both men found success early on. Wilhelm was able to conceal both the tunnel and the boat from his captors. Lane proclaimed the news of studies in Mexico and Cuba that suggested the ingestion of shark cartilage might reduce the size of cancerous tumors (Lane and Comac 1992; McSweeney 1994). Wilhelm actually escaped with his followers and made it all the way to the river without being detected or pursued. William's book, Sharks Don't Get Cancer (Lane and Comac 1992), sold so well that it led to a sequel, Sharks Still Don't Get Cancer (Lane and Comac 1996). He generated so much interest in shark cartilage that funding was given to researchers to study its effects on human cancer patients under controlled conditions.

But here things take a dramatic turn for the worse for both Wills. When Wilhelm and his compatriots got to the riverbank, they were shocked to find that there was no water. Their seemingly wonderful plan had a serious flaw, and they were recaptured within days. The many critics of William Lane believe that there are serious flaws in his reasoning. They are doubtful that shark cartilage taken orally will ever prove to be a major weapon in the war on cancer. To understand why they are skeptical, let us go back to the beginning of the shark cartilage story.

The Background

Beginning in the early 1970s, Judah Folkman and several colleagues at Harvard and MIT published a series of research papers detailing the use of cartilage as a means of slowing the growth of cancerous tumors. See Folkman and Klagsbrun (1987) for an overview of this research. In some of these studies, the cartilage source was rabbits. In others, it was cattle (bovine); later, sharks. They demonstrated that the growth of a tumor is dependent on a "process through which tumors . . . encourage blood vessel growth in order to supply themselves with nutrients so that they can expand" (Shark cartilage/angiogenesis 1992). This process is called angiogenesis. In other words, solid tumors need a blood supply in order to grow large. Since cartilage usually contains no blood vessels, it was reasoned that something in the cartilage might prevent angiogenesis.

The basic strategy was to implant tumors in laboratory animals and then determine if cartilage delayed angiogenesis. In the Brem and Folkman (1975) study, for example, cartilage was placed between the tumor and a blood supply, and observations were made over a period of time in order to determine if the cartilage slowed or stopped the growth of blood vessels needed to "feed" the tumor. Some control groups received no cartilage, while others received boiled (inactivated) cartilage. The purpose of the latter was to show that the effect was not due to cartilage, per se, but some active chemicals (proteins) in the cartilage. They were able to show that some proteins found in cartilage either halted or (in most cases) delayed angiogenesis slightly.

Langer and colleagues (1976) carried this a step further when they extracted chemicals from bovine cartilage and used the extract alone to inhibit the growth of tumors in rabbits. Injecting the extract into the bloodstreams of rabbits and mice with cancerous tumors greatly inhibited angiogenesis (Langer et al. 1980).

I have read several of the papers authored by Folkman and his colleagues - papers that have appeared in research journals with reputations for publishing top-quality work. In my opinion, their work is quite good, and those experts on cancer research to whom I have talked agree.