Cancer is bad. It is scary, sad, depressing, maddening, frustrating, terrifying, and so much more. It is a unique “disease” that can strike anyone at any age in any tissue. And despite the progress made in cancer research, we are still waiting for a complete “cure”.
But why is that? What is it about cancer that makes it such a widespread, common, and deadly disease? And why is it that there is so much cancer research and yet, we seem to still understand so little?
Cancer is a genetic disease that tampers with the cellular machinery of healthy cells. To understand what cancer is and why we haven’t cured it, we have to first understand how healthy cells work.
Cells are the basic building blocks of our bodies. One of the most important cellular structures is the nucleus. It contains most of the cells’ genetic material (DNA). The DNA is tightly coiled and stored in structures called chromosomes that act like a book filled with instructions (genes) that control the cell’s identity and actions.
In humans, there are two copies (alleles) of every gene – one from each biological parent. Among these genes include those that strictly deal with cell growth, division, and survival. When healthy cells are old, become damaged, or are no longer needed, they have genes that instruct repair or cell death (i.e apoptosis).
What goes wrong in cancer cells?
Changes in DNA, or mutations, happen. Generally, not all mutations are bad; they can actually be good! And all of us have mutations. It’s how we have genetic diversity. However, mutations in genes that control cell growth destroy the cell’s ability to detect damage and regulate growth. So you end up with uncontrolled cell growth and abnormal masses of cells, called tumors. Fortunately, not all odd cell masses are cancerous; they can be benign. Cancerous tumors are malignant, meaning they can spread to other tissues.
There are three main categories of genes that contribute to cancer.
Proto-oncogenes are genes important for cell growth and differentiation. In healthy cells, they regulate
necessary cell division and growth. They also control when cells stop dividing and take on more specific identities and functions (differentiation). If these genes are mutated, they can become an ‘oncogene’. Oncogenes promote uncontrolled cell growth. As you can imagine, oncogenes can lead to tumors.
Healthy cells also have tumor suppressor genes. A tumor suppressor gene tells cells to stop dividing and growing. Cells need to know when to stop cell growth, even under normal conditions. Damage to a tumor suppressor gene is often a “loss of function”: the cells lose their ability to stop growth. Usually these types of mutations are recessive, meaning that both copies of this gene (one from each parent) must be damaged to fully lose function.
The third category of genes commonly mutated or damaged in cancer is DNA repair genes. Normal cell division includes replication and manipulation of DNA with every cycle. Mistakes in DNA therefore occur regularly, but luckily there are DNA repair genes ready to correct and minimize damage. So, a mutation in ONE oncogene or tumor suppressor gene alone can be fixed to prevent disease. But remember- in cancer, if genes in all three categories of genes are damaged, all of the cellular checkpoints are broken, facilitating further DNA damage and cellular dysregulation.
What does this all mean?
Knowing that cancer is characterized by multiple mutations in multiple genes caused by multiple sources, how do we “cure cancer”? Each case is unique and can result from an endless combination of genetic changes. Mutations that cause cancer can be both sporadic or DNA damage caused by the environment. But even within those, the same cancer causing risks can create mutations in different genes for different people. Plus, there are so many cancer-causing factors and these are just the ones we know! We use the word ‘cancer’ as though it is one disease but it is not a singular disease.
This is part of the struggle scientists face. They can study patterns and correlations of specific genes and mutations and how they manifest in people or investigate if certain environmental factors increase risks but it will take time before scientists understand enough to make a “cure”, if it is possible. Luckily, scientists thrive on the challenge of the unknown. With this determination, scientists will continue to chase cancer to find a cure and continue to further the ever-evolving field of cancer biology.
But in the meantime, finding a cure for cancer will continue to be a bit complicated.