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. Ok.

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 All right. 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 papilloma virus can lead to cervical cancer.

On the other hand, nonmodifiable 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.

First, there's initiation where agents called carcinogens cause mutations to proto oncogenes or tumor suppressor genes causing them to lose their regulatory function.

When a proto-oncogene mutates, it becomes an oncogene which will cause cells to proliferate uncontrollably. Likewise, mutated tumor suppressor genes lose their ability to suppress uncontrolled proliferation.

These mutations pave the way for the next stage called promotion. During promotion.

The mutated cell proliferates. Promotion usually involves factors called promoters like substances in the environment or hormonal growth factors.

These promoters don't change DNA structure but enhance the development of cancer in various ways. Resulting in telomerase production.

Telomerase is an enzyme that maintains telomeres which are like caps at the end of chromosomes that protect them from damage.

Normally as cells divide telomeres shorten ultimately leading to cellular apoptosis. However, with cancerous cells, telomerase prevents telomeres from shortening, allowing unchecked proliferation of cancer cells.

Lastly progression occurs when cancer cells continue to grow and begin invading surrounding tissue cancer cells also secrete growth factors that stimulate angiogenesis or the formation of new blood vessels which allows oxygen and other nutrients to reach the cancer cells and support tumor growth.

Eventually, cancer cells can detach from the primary cancer site and spread to distant sites through blood and lymph vessels.

A process called metastasis. Now, in addition to their ability to proliferate uncontrollably invade surrounding tissue and metastasize cancer cells differ from normal cells in other ways.

In contrast to normal cells, cancer cells are anaplastic, which means they are undifferentiated. So they look and function differently from the normal cells in the tissue where the cancer is growing.

They're also pleomorphic, meaning they have an irregular size and shape. For example, cancer cells often have large dark colored nuclei with scarce organelles within the cytoplasm.

Tumors also lack normal tissue structure. So they have a disorganized haphazard arrangement.

Now, clinical manifestations depend on the type and location of the cancer and the degree of metastasis early on the cancer may not cause any symptoms.

But as the cancer grows, the immune system is activated in an attempt to eliminate the cancer cells. This results in nonspecific manifestations such as night sweats, fever and fatigue.

Many cancers are also associated with cachexia or severe tissue wasting. This is related to factors like anorexia or loss of appetite, changes in taste and altered metabolism of nutrients.

Infection is also a common problem caused by cancer. Since cancer cells can secrete substances that depress the immune system.

As cancer cells invade organs, bones and other tissues. Pain receptors are activated, tissue is destroyed and inflammation occurs.

Tumors may also compress or obstruct tissues and organs contributing to pain and restricting the flow of blood or lymph leading to ulceration, edema and organ dysfunction.

Lastly, local tumor invasion and subsequent bleeding can cause bruising hemoptysis, hematuria, melena and anemia. All right.

As a quick recap, 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.

Carcinogenesis occurs in three main stages. Initiation promotion and progression.

Clinical cancer manifestations depend on the location, type and degree of metastasis.