Over the last quarter of a century, I’ve written about a lot of different aspects of science and medical research. Cancer features a lot, the Big C is prominent in human misery and more common than many other diseases. Often I’ll use a phrase such as “treating liver, bowel, lung, breast, prostate and other cancers”. One phrase I don’t think I’ve ever written, until today is “heart cancer”.
Heart cancer? Do people even get heart cancer? Almost every other organ from skin to brain from gonads to liver, from head and neck to bone and blood, there’s a cancer. Experts repeatedly explain that cancer isn’t a single disease (well it is really, it’s always just runaway cell division of a specific tissue). But, it occurred to me that one of those tissues, cardiac tissue, is rarely mentioned. I then wondered whether or not the lack of malignant tumours in this vital organ might offer clues as to why other organs develop cancers. If there’s some sort of cardioprotection might that be exploited in preventative measures or treatment of cancers elsewhere in the body.
The Mayo Clinic website, always a trustworthy medical resource has this to say about heart cancer in its FAQ:
Cancerous (malignant) tumors that begin in the heart are most often sarcomas, a type of cancer that originates in the soft tissues of the body. The vast majority of heart tumors are noncancerous (benign).
Indeed a study of autopsies on 12000 cadavers revealed only seven cases of primary cardiac tumour. Rare indeed, then, and presumably why we don’t often hear about breakthroughs and new treatments for heart cancer, Big Pharma really won’t profit much from rare disease compared with breast, prostate and other far more common cancers. However, cancers in other parts of the body, such as the lungs, do metastatise (spread) to the heart. Indeed, breast, kidney, lung cancers, leukaemia, lymphoma and melanoma can spread to the heart. But, the fact that heart cancer is so rare must be a clue, the heart is special when it comes to runaway cell division in some way, surely?
The Cancer Research UK site recently published a debunking of the notion that cancer is mostly down to bad luck rather than lifestyle factors that increase risk. They explain that a study in mice showed that there needs to be an alignment of factors for cancer to develop. They add that “We can still stack the odds in our favour, for example by stopping smoking, keeping a healthy weight, eating healthily, drinking less alcohol, keeping active and enjoying the sun safely.” But, what are the risk factors for heart cancer, if indeed there are any?
The US National Cancer Institute has also asked the same question, why are heart cancers so rare? The answer perhaps lies in the fact that unlike other organs when they are damaged, the heart is almost incapable of repairing its tissues, the cells of the heart, the cardiac myocytes, are terminally differentiated and so after a certain point in life they stop replicating (cell replication is both the key to tissue repair and, when it goes awry, the problem in cancer).
This latter point suggests to me that there is probably no way to exploit the heart’s lack of cancer in protecting other organs, although who knows? It’s a double-edged sword, you really wouldn’t want damage to not be repaired elsewhere in the body, such as the liver or kidneys. But perhaps the repair process could be temporarily switched off somehow when a tumour develops there. Block the replication instead of simply killing the rapidly replicating cancer cells. If this was done temporarily while a parallel gene therapy type approach was used to fix the cancer-causing mutations in the cells in that tissue we might find a viable treatment. I’m speculating here…anyone know enough to point out the flaw in my argument?