Explore the basics of cancer- what it is and what can cause it. Discover details of two subtypes of lung cancer and the biomarkers uniquely found on each.
What is cancer?
Cancer is a disease in which abnormal cells divide uncontrollably and destroy body tissue. Once the cells start growing into large masses, also known as tumors, the cells can start to move to other parts of the body, a process called metastasis. These cancer cells grow uncontrollably because there has been a change, or mutation, in the genes that regulate division.
Genes and Cancer
Every time a cell has to divide to make more cells, the DNA must be copied. This allows each cell at the end to have the appropriate DNA to keep functioning. As the DNA is copied, mistakes can sometimes be made, these are called mutations. Some mutations don’t change anything but others might prevent an important part of the cell from being made or functioning. Often times, one mutation doesn’t have much effect because humans have 2 copies of most genes, one from each chromosome in a pair. When there are multiple mutations in both copies, the gene stops working. Mutations happen in our cells very often, but the cell can usually detect the change and repair it. Though our cells are very good at catching these mistakes, some slip through the cracks.
Even if your cells never mutated through replication, they may still mutate based on your environment. Things like cigarette smoke, radiation, and UV light can cause the DNA to change. Because of their ability to affect the DNA, these are called carcinogens, meaning that they can cause cancer. The more a person is exposed to these carcinogens, the more likely they are to develop cancer.
Humans have two sponge-like organs in the chest to help us breathe. To breathe, air comes in through the nose and mouth and travels down the trachea (windpipe). The trachea divides into tubes called bronchi which enter the lungs and divide into smaller tubes until the air reaches a tiny sac known as alveoli. The alveoli are very thin covered in blood vessels to help get oxygen into the blood stream and carbon dioxide out.
Lung Cancer Causes
Smoking tobacco is the leading cause of lung cancer. This includes secondhand exposure to smoke. Other risk factors for lung cancer include radon, asbestos, diesel exhaust, and air pollution.
Lung Cancer Biomarkers
Lung cancers typically start in the cells lining of the bronchi and can spread to other parts of the lungs or body depending on the subtype.
All lung cancers have a protein on the outside of the cells called carcinoembryonic antigen (CEA). CEA is an important protein in fetus development but is usually found at low levels in adults. Both lung cancer subtypes, SCLC and NSCLC, have CEA present on the outside of their cells. CEA will be used to help diagnose that a patient has lung cancer before trying to determine its subtype.
Small Cell Lung Cancer (SCLC)
Small cell lung cancer (SCLC) accounts for 10-15% of all lung cancer cases. Small cell lung cancer cases generally start in the large breathing tubes of the lungs, the bronchi. Like it’s name indicates, small cell lung cancer has smaller cells than non-small cell lung cancer. The small cells make the disease spread faster, metastasizing quickly to other body parts.
Pro-gastrin releasing peptide (proGRP), is a biomarker that is found on the exterior of only small cell lung cancer cells. proGRP is usually expressed in the nervous system and digestive tract but is seen at high levels when a patient has SCLC.
Non-Small Cell Lung Cancer (NSCLC)
Non-small cell lung cancer (NSCLC) is more common, accounting for 80-85% of lung cancer cases. Non-small cell lung cancer starts in the center of the lungs and sometimes the peripheral edges of the lungs. This cancer is also more common amongst people who smoke or have smoked in the past. We also see that women are diagnosed with non-small cell lung cancer more than men and that younger people are diagnosed with it more than those that are older.
The marker neuron specific enolase (NSE) is a biomarker that is found on the exterior of only non-small cell lung cancer cells.