Cancer Basics
Cancer can appear in any part of the human body, with many common locations in the skin, brain, stomach, pancreas, lungs, and breast. Cancer is typically caused by a cell mutation that leads to abnormal cell division. When a mutation gives cells a growth advantage, it is able to outperform normal cells. If it acquires more mutations that also benefit its reproductive advantage, as well as skips over key checkpoints or damages its repair genes, then the cell is able to divide indefinitely. Uncontrolled cell division leads to widespread proliferation, generating a tumor consisting of many cancerous cells. Cancer cells in one part of the body may spread to other parts through the blood and lymphatic systems, known as metastasizing. However, not all cancerous cells are able to metastasize. To spread, cells must be able to penetrate normal barriers, so they can enter and exit blood/lymph vessels.
To date, over 100 different types of cancer have been identified, most of them named for the primary organ where they were found growing. According to the National Cancer Institute, cancer is categorized into broad categories including:
- Sarcoma
- Carcinoma
- Lymphoma and Myeloma
- Leukemia
- Central Nervous System
Carcinomas are cancers that originate in the tissues or skin that line or protect internal organs. Sarcoma cancers are those that originate in the connective or supportive tissues of the body such as the muscles, cartilage, bones, blood vessels or fat. Lymphomas and myelomas are cancers that originate in the immune system. Leukemias are cancers that often originate in blood-forming tissues including bone marrow. Leukemia does not produce tumors but affects body parts and organs that depend on healthy red and white blood cells for optimal health.
There are many cells within the human body that divide and grow in a controlled method and, when these cells die, healthy new cells replace them. An example of this is the continuous replacement of the skin layer. Unfortunately, in some cases, this process goes wrong and the genetic makeup of cells can be damaged or altered in a way that produces a mutation. The end result is an effect on typical growth, development, and division of a damaged cell.
Uncontrolled Growth
Defective cancerous cells do not die, and as a result, continue to proliferate until they form a mass called a tumor. In most cases, tumors may be identified as benign or malignant. A benign tumor is deemed not cancerous while a malignant tumor is cancerous. Malignant tumors may spread to other body parts, even if the bulk of the tumor is removed.
Uncontrolled growth is caused by a malfunction in a cell’s regulation of its own growth. Genetic mutations prevent the cell from dividing (reproducing) in a regular manner; the cell continues to divide without stopping. As a result, the daughter cells also divide without stopping, leading to tumor formation.
These genetic changes can be caused by a variety of factors, including errors in cell replication, damage to DNA from harmful substances in the environment (smoking, UV rays, etc.), and through inheritance from one’s parents. Normally, the body is able to remove these errors and defects, but its ability to do so can change, like with age. This is why there is a higher risk for cancer at older ages (https://www.cancer.gov/about-cancer/understanding/what-is-cancer)
Clinical Difficulties – Mutations
Cancer growth can be fast or slow, but the main issue is that cells continue to divide in a process that is difficult to halt. All cancers develop or stem from a single ancestral cell and are less differentiated than normal tissue cells. Cancer cells are believed to develop from what are known as precursor cells, in various tissues. As cell regeneration happens, DNA of cancerous cells gets damaged more than surrounding cells. Eventually, the mutations overcome regulation and lead to uncontrollable cancer cell growth.
Cancer research is an extremely rich and diverse investigational field. Experiments performed in this area include xenograft animal models, research into apoptosis, the lack of cancer cell becoming senescent, testing novel chemotherapeutics, and determining the toxicity of cancer treatments. In addition, the development of novel stable cell lines aids in cell-based research.