The explanation is a lot simpler than you might think, but not obvious enough to realize at first.
Cancer, we’ve all heard of breast cancer, prostate cancer, lung cancer, but not many people get heart cancer. Why is that? To understand why the heart rarely forms cancer, we first have to understand cancer and the cells of the heart itself.
Cancer is a genetic disease, specifically caused by changes in cell function, especially growth and division. There is a discrepancy in what the cell is supposed to do. Somewhere in its genetics, there is a transgression of how the cell should replicate and when the cell should undergo apoptosis. Our cells are smart, but they do encounter errors. Many times, these errors are irrelevant, but when they add up, it can lead to drastic results like cancer.
There are 3 main gene alterations that conduce cancer, those being DNA repair genes, proto-oncogenes, and tumor suppressor genes. An abnormality in these genes is an increased likelihood of cancer.
DNA repair genes: There is a constantly occurring process where our cells use pathways to fix errors in DNA. Cells that have a mutation in a gene linked to that process leads to mutations in other genes because there is no way for the cell to find and repair the initial problem, which then cascades into other mutations. The 3 results that can happen with this mutated gene are: 1. The cell becomes dormant, useless, and eventually dies, 2. Apoptosis, or 3. Unregulated cell division (Cancer or tumor growth).
Proto-oncogenes: These genes signal when a cell should grow, divide, and also when to die. A clear error in these genes would cause the cell to grow and divide in conditions it should not.
Tumor suppressor genes: These genes are also involved in cell growth and replication. A mutation in this gene can cause a cell to divide uncontrollably.
Cancer can arise in any cell of the body, but some cells are more prone to cancer than others.
Epithelial Cells: Epithelial tissue lines the outside of our organs, blood vessels, and inner surfaces of many internal organs. An example can be the skin. Cancer-affected epithelial cells are called carcinomas and make up about 80-90% of cancers.
Cells that make up blood and the lymphatic system: The cancer of these cells are called leukemias and lymphomas. These cells can be found in lymph nodes, spleen, thymus, bone marrow, and other parts of the body. This accounts for about 5-10% of cancers.
Connective tissue cells: Cancer of muscles, bones, tendons, nerves, fat, and cartilage are referred to as sarcomas. This cancer accounts for about 1% of all cancer.
By looking at what cells cancer affects the most, one can conclude that cancer is more prominent in highly replicating cells. For example, there is a higher occurrence of skin cancer compared to cancer of the brain, simply because the cells in your skin replicate and die at a lot greater pace than the cells in your brain. How many times do you shed dry skin compared to a neuron? The more a cell replicates, the greater chance for mutations to occur.
Your heart is a muscle that pumps blood to your organs. The cells that make up your heart are muscle tissue. However, there is a difference between the muscle tissue that is in your heart compared to the ones around your organs, in your calves, biceps, and all the other muscles in your body. Skeletal muscle and smooth muscle have the ability to create new cells; unfortunately, your heart does not, or at most minimally. Since the cells in your heart do not replicate, it is extremely rare to develop cancer of the heart, according to Mayo Clinic, there is roughly 1 case a year of primary heart cancer. This, however, does have a drawback, the main issue with heart damage is associated with ischemic damage. When blood flow is lacking in the heart, it deprives cells of blood and oxygen, causing them to permanently die and scar over, think heart attack.
For hundreds of years, it was thought that the heart is just a pump that delivers blood throughout the body. Now we know that the heart is not only a muscle that pumps blood, but also has endocrine properties, secreting hormones such as ANP and BNP. ANP or Atrial natriuretic peptide is secreted by the atria in the heart as a response to stretching of the wall. I’d like to focus from here on specifically ANP. The main function of ANP is to lower blood pressure and maintain electrolyte homeostasis. It lowers blood pressure and maintains the electrolyte balance by causing your kidneys to excrete salt and water, vasodilation, and increase vascular permeability.
Relating this back to cancer, ANP has been shown in some research to actually decrease cancer occurrence and activity. There are a few studies I’d like to address; I’ll leave the links at the end of the post so you can take a look for yourselves. The studies showed promising effects of ANP against certain types of cancers. The studies examined ANP effects on cancer in vitro and vivo.
One study² showed a 97% elimination of pancreatic, breast, colon, prostate, ovarian, small cell lung, and squamous cell lung carcinoma in vitro. 80% of mice that had human pancreatic adenocarcinomas were rid of the cancer, and the cancer also did not return to the primary site in their lifespan. 86% of human small cell lung carcinomas were eliminated in mice. 67% of human breast carcinomas were eliminated in mice, with no primary recurrence within 12 months. The way ANP and other cardiac peptides eliminate cancer is through their ability to bind to receptors and inhibit metabolic pathways that are crucial to the formation of cancer cells. One of these pathways is the RAS-MEK ½-ERK ½ kinase cascade, which I won’t go into detail, but is associated with poor prognosis. Another concept the study addressed was the effect of the peptides on normal healthy human cells. It showed that the cardiac hormones were cytotoxic to human cancer cells while sparing healthy ones and the hormones caused the death of cancer cells, but spared human lung, kidney, and prostate cells from death.
Another study³ showed the effectiveness of adjunct ANP therapy to surgical therapy in treating cancer. The study states, “we demonstrate that cancer recurrence after lung cancer surgery was significantly lower in ANP-treated patients than in control patients (surgery alone)³.” ANP was able to prevent cancer metastasis by suppressing inflammation in epithelial cells, which then prevented cancer cell adhesion to vascular walls. The study found that the 2-year relapse-free survival of patients treated with ANP and surgery was 91% vs. patients treated with just surgery with 67%.
As more research is done, there will be more ways to treat cancer. Maybe in the future, ANP therapy will be a standard therapy. It is showing promising results; however, much more research has to be done to fully understand its mechanisms and safety for humans.
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