What Causes Cancer and How Does Cancer Form?

Millions of people die each year of cancer, but so many still don’t know how cancer cells form and what they can do to prevent them from getting cancer. We will know look at how cancer forms and what causes it.

There are over 100 different types of cancer, and each is classified by the type of cell that is initially affected. Each cancer is different according to its biology and pathophysiology. All animals and even plants are susceptible to cancers.

 

How Cancer Forms

The body is made up of trillions of living cells. These cells grow, divide, and die in an orderly fashion. This process is tightly regulated and is controlled by the DNA machinery within the cell. In a baby or a child normal cells divide rapidly to allow for growth. After the person becomes an adult, most cells divide only to replace worn-out or dying cells or to repair injuries.

When cells of the body at a particular site start to grow out of control, they may become cancerous. Cancer cell growth is different from normal cell growth. Instead of dying, cancer cells continue to grow and form new, abnormal cells. In addition, these cells can also invade other tissues. This is a property that normal cells do not possess.

Cancer cells originate from normal cells when their DNA (deoxyribonucleic acid) or blue prints within the cell nucleus is damaged. DNA is in every cell and it directs all the cell’s actions, growth, death, protein synthesis etc. when DNA is damaged in a normal cell the cell either repairs the damage or the cell dies.

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Normally, the body safeguards against cancer via numerous methods, such as: apoptosis or a process by which abnormal cells die on their own accord, helper molecules (some DNA polymerases), possibly senescence or aging, etc.

In cancer cells, the damaged DNA is not repaired, and the cell does not die. Instead it gives rise to more such abnormal cells with abnormal DNA. These new cells all have the same defective DNA of the original cancer cell.

Tumors can grow and interfere with the digestive, nervous, and circulatory systems, and they can release hormones that alter body function. Tumors that stay in one spot and demonstrate limited growth are generally considered to be benign.

More dangerous, or malignant, tumors form when two things occur:

  • a cancerous cell manages to move throughout the body using the blood or lymphatic systems, destroying healthy tissue in a process called invasion
  • that cell manages to divide and grow, making new blood vessels to feed itself in a process called angiogenesis.

When a tumor successfully spreads to other parts of the body and grows, invading and destroying other healthy tissues, it is said to have metastasized. This process itself is called metastasis, and the result is a serious condition that is very difficult to treat.

According to the American Cancer Society, Cancer is the second most common cause of death in the US and accounts for nearly 1 of every 4 deaths. The World Health Organization estimates that, worldwide, there were 14 million new cancer cases and 8.2 million cancer-related deaths in 2012 (their most recent data).

 
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Cancer Risk Factors

According to World Health Organization (WHO), common risk factors for cancer include:

  • Tobacco use
  • Alcohol use
  • Overweight and obesity
  • Dietary factors, including insufficient fruit and vegetable intake
  • Physical inactivity
  • Chronic infections from helicobacter pylori, hepatitis B virus (HBV), hepatitis C virus (HCV) and some types of human papilloma virus (HPV)
  • Environmental and occupational risks including ionizing and non-ionizing radiation

 

Cancer Cell Mutations

Mutations may be:

  • Those in the error-correcting machinery of a cell. This may cause accumulation of errors rapidly in the cell and its progeny.
  • Those in signaling (endocrine) machinery of the cell. This leads transmission of the error signals to nearby healthy cells as well.
  • Those that allow the cells to migrate and disrupt more healthy cells away from the primary site of origin.
  • Those that make the cell immortal so that the abnormal cell refuses to die.

 

Individual Types of Cancer

There are said to be over 200 different types of cancer. We have the following common cancer types written below:

The top 5 most-diagnosed cancers in men:

    1. Lung Cancer
    2. Prostate Cancer
    3. Colon/colorectal Cancer
    4. Stomach Cancer
    5. Liver Cancer

The top 5 most-diagnosed cancers in women:

    1. Breast Cancer
    2. Colon/colorectal Cancer
    3. Lung Cancer
    4. Cervix Cancer
    5. Stomach Cancer

 
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Cancer Causing Agents

Agents that may cause cancer include:
 

Genetically Modified Foods (GMOs)

The rapidly growing industry of genetically modified crops are infiltrating our food supply at an alarming rate. More than 90% of our corn and soy are now genetically modified. This fairly new practice is the source of many debates. Experts agree that adequate testing was not done before GMO foods were added to the ingredient listing of thousands of products. In other words, no one – including the growers and manufacturers of GMO foods – knows the long-term effect they will have on human health. Look for GMO-free labels whenever possible or buy organic (which always means a product is not genetically modified).
 

Chemical Carcinogens

Several chemicals and environmental toxins are responsible for changes in normal cellular DNA. Substances that cause DNA mutations are known as mutagens, and mutagens that cause cancers are known as carcinogens.

Particular substances have been linked to specific types of cancer. Tobacco smoking is associated with many forms of cancer, and causes 90% of lung cancer. Similarly, prolonged exposure to asbestos fibers is associated with mesothelioma.

Tobacco is also related to other cancers such as lung, larynx, head, neck, stomach, bladder, kidney, oesophagus and pancreas as it contains other known carcinogens, including nitrosamines and polycyclic aromatic hydrocarbons.
 

Ionizing Radiations

Radiations due to radon gas and prolonged exposure to ultraviolet radiation from the sun can lead to melanoma and other skin malignancies. Radiation therapy given for one type of cancer may also cause another type of cancer. For example, those who receive chest radiation therapy for lymphomas may later develop breast cancer.
 
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Viral and Bacterial Infections

Some cancers can be caused by infections with pathogens. Notable among these include liver cancers due to Hepatitic B and C infections; cervical cancer due to infections with Human Papilloma virus (HPV); Epstein Barr virus causing Burkitt’s lymphoma and gastric or stomach cancer due to Helicobacter pylori infection.
 

Genetic or Inherited Cancers

Common examples are inherited breast cancer and ovarian cancer genes including BRCA1 and 2. Li-Fraumeni syndrome includes defects in the p53 gene that leads to bone cancers, breast cancers, soft tissue sarcomas, brain cancers etc. Those with Down’s syndrome are known to develop malignancies such as leukemia and testicular cancer.
 

Hormonal Changes

Notable among these are changes in the female hormone levels estrogen. Excess estrogen promotes uterine cancer.
 

Immune System Dysfunction

Impaired immunity including HIV infection leads to several cancers including Kaposi’s sarcoma, non-Hodgkin’s lymphoma, and HPV-associated malignancies such as anal cancer and cervical cancer.

 
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Cancer Facts

Here are some key points about cancer:

More than 575,000 people die of cancer, and more than 1.5 million people are diagnosed with cancer per year in the US.

Cancer is considered to be one of the leading causes of morbidity and mortality worldwide.

The financial costs of cancer in the US per year are an estimated $263.8 billion in medical costs and lost productivity.

African Americans are more likely to die of cancer than people of any other race or ethnicity.

It is believed that cancer risk can be reduced by avoiding tobacco, limiting alcohol intake, limiting UV ray exposure from the sun and tanning beds and maintaining a healthy diet, level of fitness and seeking regular medical care.

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Screening can locate cervical cancer, colorectal cancer and breast cancer at an early, treatable stage.

Vaccines such as the human papillomavirus (HPV) vaccine assists in preventing some cervical, vaginal, vulvar, and oral cancers. A vaccine for hepatitis B can reduce liver cancer risk.

According to the World Health Organization (WHO), the numbers of new cancer cases is expected to rise by about 70% over the next 20 years.

The most common sites of cancer among men are lung, prostate, colon, rectum, stomach and liver.

The most common sites of cancer among women are breast, colon, rectum, lung, cervix and stomach.


Article Summary


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