The heart is one of the organs least affected by cancer in the world. A study published in the journal Science has just explained why and the answer is as simple as it is unexpected.
Lungs, breast, colon, prostate: cancers can affect almost all organs of the human body. Almost. Because there is one that almost entirely escapes disease: the heart. Tumors that grow directly in the heart muscle are seen in less than 1% of autopsies. Even the metastases that do reach it – up to 18% of autopsies – tend to remain small and silent, often discovered by chance. A study published on June 30 in the journal Science, led by Giulio Ciucci and Serena Zacchigna from the ICGEB in Trieste (Italy), and relayed by Medscape, has just given the key.
The answer is as simple as it is unexpected: it is thanks to its beats that the heart would protect against cancer. Each contraction of the heart generates mechanical pressure on the cells that compose it and it is precisely this pressure that prevents cancer cells from proliferating. To demonstrate this, the researchers first induced genetic alterations typical of many human tumors in the liver, skeletal muscle and heart of seven mice.
Tumors appeared in different areas, but never in the heart. To isolate the role of mechanical pressure, they then resorted to an ingenious experiment: grafting an additional heart into each mouse, connected to its blood vessels but never beating, therefore without mechanical load. By injecting cancer cells into both hearts – the native heart which beats, and the transplanted heart which does not beat – of the same animal, the result was clear. After fourteen days, in the non-beating heart, the tumor had replaced almost all of the healthy tissue. In the native heart, it only occupied barely 20% of the ventricle.
It was not a question of initial implantation, nor of greater cell death: only the potential for cancer cells to multiply had changed. When the heart beats, tumor cells simply cannot divide.
The researchers then identified how this mechanism works. The mechanical pressure of beating acts directly on the nucleus of cells and activates genes which slow down their division. They even identified the protein responsible for this process: by neutralizing it in the laboratory, the tumor cells began to proliferate again even in a beating heart. In other words, the heartbeat would not only be a vital function. It would constitute an environment actively hostile to the growth of tumors.
Concrete applications remain in the domain of research for the time being. Two avenues are being studied: portable robotic devices capable of imitating the heartbeat to apply mechanical stimuli to superficial tumors, and drugs capable of reproducing this effect on cells. “However, we are still at a very early experimental stage”warns Serena Zacchigna, coordinator of the study. A fundamental discovery which, if confirmed in humans, could open an entirely new path in the fight against cancer.
