What Cancers are Genetic? Inherited Genes and Cancer Types
The term “cancer” has come to be an umbrella term for all the different types of cancers that exist, depending on which part of the body is affected. Depending on where in the body the cancer is, its severity and speed of progression all differ. More aggressive cancers are said to progress much faster, affect many more body parts and are difficult to treat and/or manage. And yet other cancers that are not quite as aggressive can be managed and treated and those who are affectedcan lead normal lives.
Before getting in the genetic aspect of cancer, let’s first go a bit into what exactly causes it and how it progresses. Cancer is a very intelligent and relentless mistress that constantly deceives the body into believing that everything isOK and as such ensures its survival. Every cell in the human body contains DNA that contains the basic instructions that cells and tissues rely on in order to maintain proper function. DNA is packaged into the 23 pairs of chromosomes in each cell, or 46 chromosomes, whereby one half of that is inherited from the mother and the other half from the father. Scattered across these chromosomes are approximately 25,000 genes that are used by the cells to produce proteins as well as other substances that are vital for the maintenance of proper functions, and cells must maintain proper functions in order to divide and multiply properly. If any of the substances that are responsible for proper cell division and multiplication are not functioning correctly, the cell goes into apoptosis, or programmed cell death. This means that each cell has a mechanism in place that orders it to die if it is not functioning properly. In the case of cancer, this mechanism of programmed cell death does not function properly. As such, dysfunctional cells do not have the means by which to recognize a sick cell. This, in turn, means that the cell does not go into apoptosis and instead hangs around. If this is the case in many cells in the body, this leads to an amassment of dysfunctional cells that keep dividing and multiplying. This culminates in a mass of cells that is referred to as a tumor.
To put genetics into all of this, the mechanism that tells each dysfunctional cell to go into programmed death is driven by signals that are directed by our genes. There are checkpoints along the way that constantly seek signals of improper cell function, for example. Therefore, mutations in the genes that control such important processes in the body compromise those processes, meaning that these checkpoints cannot go on as usual. This eventually leads to tumors or, in other words, to certain cancers or hereditary cancer.
Cancer being the umbrella term for several different kinds of the disorder contains cancer types that are inherited as well as spontaneous, meaning that some of us have inherited genetic markers for hereditary cancer and others have not but are still at risk. While technological and scientific advancements have greatly improved our understanding of the genetic background of cancers such as cancer of the breast, thyroid cancer, and prostate cancer, the majority of types of cancer are still developed by chance. And while everyone is at some risk of developing cancer, there are individuals who have a higher predisposition than others and as such have a higher risk for it than the general public.
Cancer usually begins with a genetic mutation that takes place randomly in one or many cells in the body. These mutations are referred to as “somatic” and they are a consequence of several factors such as aging or when DNA damage has occurred. These mutations are also termed as “acquired” mutations and they are typically not passed on from parents to their offspring. However, only a small fraction have inherited cancer as a result of having inherited a mutation from either the mother or the father or, in some cases, both. These mutations are called “germline” mutations as they come from either the egg or the sperm DNA. It is important to highlight at this point that individuals whose parents have suffered from a germline-type cancer are at an increased risk of developing the disease rather than it being completely certain that they will develop cancer. This is why it is important for individuals who have cancer in their family to perhaps conduct genetic testing and see if they are carriers of any cancer mutations. This is practical for two main reasons. One, knowing that there is a higher risk for developing the disease may make management easier or may trigger precautionary measures. Another reason genetic testing may be a valuable option is for other family members as well as possible future children—it is just good information to have.
So, what are the most common germline cancers affecting the population?
The most prominent one is breast cancer and it is widely known that it runs in families. Breast cancer is caused by several genetic mutations in two genes, namely BRCA1 (breast cancer 1) and BRCA (breast cancer 2). Women who have mutations in those genes are at high risk of being diagnosed with breast cancer or ovarian cancer or both. Other cancers that have been associated with mutations in BRCA1 and BRCA2 include pancreatic cancer, stomach cancer, and prostate cancer as well as colon cancer. (Men who are BRCA-carriers are twice as likely to develop prostate cancer than non-carriers.) Other cancers include melanomas (skin cancer) as well as acute and chronic myelogenous leukemias.
Overall, as with many other conditions that have been highlighted to have a hereditary and/or genetic underpinning, cancer is associated with several markers that are incredibly informative about one’s chances of developing the disease. Again, genetic testing, as well as a discussion with a genetic counselor, may be very helpful in determining what is best to do and how to move forward.