Biology of Cancer

Cancer is a collection of conditions that can affect any organ in the body and is characterized by abnormal cells that divide and grow uncontrollably. This can lead to the development of masses of tissue called tumors that can spread, or metastasize, throughout the body.

Okay, as a brief review, there are some key attributes that characterize normal, functional cells. An important characteristic is differentiation, meaning normal cells become specialized in their structure, location, and specific function.

For example, muscle cells have different shapes and functions than brain cells, and they’re found in different parts of the body. Normal cells also have a uniform shape; they tend to stick together; and have an orderly arrangement within their specific tissue.

Another characteristic is that normal cells age naturally over time, and undergo apoptosis, or programmed cell death, when they become old or damaged.

Lastly, normal cells grow and divide only when necessary. In fact, they can’t divide indefinitely because the process of growth and division is regulated by two types of genes, called proto-oncogenes and tumor suppressor genes.

When needed, proto-oncogenes activate cell growth and division, a process known as proliferation; whereas tumor suppressor genes suppress uncontrolled cell proliferation.

Alright, now cancer results from gene mutations, or changes to the DNA sequence, which can be inherited or develop spontaneously. Mutations are more likely to occur when risk factors are present, which can be either modifiable or non-modifiable.

Modifiable risk factors include lifestyle choices that involve exposure to carcinogens, or substances that can initiate the development of cancer, like tobacco, alcohol, ultraviolet light, and high-fat foods. Additionally, exposure to certain hormones, chemicals, and viruses can heighten cancer risk. For example, estrogen is associated with endometrial cancer; harmful chemicals like asbestos can lead to lung cancer; and high-risk strains of the human papillomavirus can lead to cervical cancer.

On the other hand, non-modifiable risk factors cannot be changed and include a family history of cancer, advanced age, and previous cancer diagnosis. Interestingly, most cancers are caused by a complex mix of factors, and sometimes cancer develops when there are no known risk factors.

Now, carcinogenesis, or the transformation of healthy cells into cancer cells, occurs in three main stages: initiation, promotion, and progression.