Physical Carcinogenesis

Carcinogenesis is defined as the process of cancer growth. Specifically, the term refers to the process by which normal cells in the body mutate into cancer cells. In order for carcinogenesis to occur, damages in healthy cell DNA must occur. For this reason, carcinogenesis is often tied to genetics. However, exposure to certain chemicals and other hazardous materials can also cause cell damage that can lead to cancer.

Factors That Contribute to Carcinogenesis

While the factors that contribute to cancer growth are complex and still being studied by the research community, a number of contributing factors have been identified that increase a cell’s risk for carcinogenesis. These factors include genetics, environmental exposure and age. Regardless of the instigating cause of cancer growth, proliferation is dependent on the ability of the cancer cells to:

  • Grow quickly and inappropriately
  • Avoid cell death via the body’s defense systems
  • Stimulate their microenvironment
  • Spread to new areas of the body

Based on research, the biological contributing factors that foster carcinogenesis include:

  • Errors in gene expression due to faulty chromatin structure
  • Improper signal transduction between cells
  • Unhealthy hormone exposure
  • Improper metabolism of fatty acid
  • Damaged DNA or repair responses

The Importance of Proto-Oncogenes

Proto-oncogenes are a specific subcategory of genes that are responsible for inducing cell growth. A series of mutations in this key gene category is typically where carcinogenesis begins. Due to one or several of the contributing factors listed above, these proto-oncogenes become damaged in a way that accelerates cell growth. This, in turn, provides the rapid growth necessary for cancer cells to flourish, grow and spread throughout the body at such a rate that the natural immune system cannot adequately defend itself.

Damage to tumor suppressor genes often works in tandem with damaged proto-oncogenes to create cancer. Tumor suppressor genes are designed to clean up any DNA damage that may occur during cell replication. When damage to these tumor suppressors occurs, DNA damage proliferates, which can lead to mutations that ultimately give rise to cancer cells.

Other Instigators of Cancer

Mutation of proto-oncogenes and tumor suppressor genes are thought to be the most common cause of carcinogenesis. However, there are other non-mutagenic effects that also are believed to cause cancer. For example, an increase in estrogen in the body is thought to increase the rate of cell mitosis without causing gene mutation. This increase in mitosis proliferates cell growth much in the same way as damaged proto-oncogenes. Excessive consumption of alcohol can also stimulate mitosis.

To a lesser degree, bacteria and viruses have also been known to spur carcinogenesis. For example, HPV, Hepatitis B and EBV are all known illnesses that can directly cause cancer. It is believed that the reason for this is the virus’ ability to promote cell proliferation by inserting a portion of its own DNA into healthy human cells.

Difference Between Benign and Malignant Tumors

There are three stages of carcinogenesis – initiation, promotion and progression. Initiation results when a cell experiences damaged DNA. Promotion exacerbates cell damage and growth by altering gene expression, suppressing an immune response and enhancing cell division. While in the promotion stage, tumor cells are said to be benign. This means that they are non-cancerous, yet still unhealthy and growing at an abnormal rate.

Once the damaged cells begin to exchange DNA between chromosomes, express oncogenes and exhibit additional mutations, the progression stage of carcinogenesis is achieved. It is in this third stage that malignant tumors begin to grow.

Resource:

http://www.niehs.nih.gov/research/atniehs/labs/escbl/

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