Causes of Cancer

Causes of Cancer

Cancer is caused by agents called carcinogens. Carcinogens cause cancer by damaging DNA which can no longer code for the important regulatory functions of the cell cycle. Some viruses can also increase the likelihood of getting certain types of cancer. Human papillomavirus (HPV), the disease that causes genital warts, can increase a woman’s risk of cervical cancer, and infection with hepatitis B or C increases the risk of liver cancer.

In addition, some people are born with genetic mutations that they have inherited from their parents that increase their chances of getting cancer. However a genetic predisposition to cancer does not mean that you will get cancer. If you have a family history of cancer it simply means it is more important for you to limit your exposure to carcinogens. Examples of some carcinogens include:

  • cigarette smoke
  • radiation
  • x-rays
  • UV light
  • food additives
  • several dangerous chemicals


Carcinogens can cause a DNA mutation that occurs in one of several genes that normally function to control growth. E.g the BRCA1, or “Breast Cancer Gene”. The BRCA1 gene normally functions to suppress tumour formation; but if a genetic mutation occurs it does not work properly, and tumour formation can begin. Mutations in this gene does not mean that a person will develop breast cancer, but they have an increased risk for breast cancer.


Image credit: Public domain

Beliefs and Attitudes Concerning Cancer

There are some common misconceptions about cancer

  • It is people’s fault if they get cancer: although there are ways to try and decrease your risk of getting cancer, it is not always possible. Cancer is caused by random mutations in DNA, and sometimes people get cancer purely by chance.
  • Cancer is a death sentence: sometimes when the cancer is very advanced there is not much to be done to save a person, but there are many cancers that respond well to treatment when detected early. Depending on the type and the stage of the cancer, people can survive cancer and go on to live healthy happy lives.
  • If someone in your family has cancer you might get it too: although there are some cancers that are more common in certain families due to an inherited genetic mutation, a family history of cancer does not mean than you will also get cancer. However, if a certain type of cancer runs in your family it is good to see a doctor for regular screenings.
  • Cancer is contagious and you can catch it from others: cancer cannot be spread from one person to another.
  • A positive attitude can cure cancer: there is plenty of evidence that a positive attitude can help a person with cancer feel better and stay healthier for longer, however it is not the only factor that determines whether someone will recover or not.
  • Only old people get cancer: although cancer is more common in older people, children and babies can also get cancer. Leukaemia is a common childhood cancer.
  • Only females get breast cancer: although breast cancer is more common in females, males can also get breast cancer.
  • Only pale people get skin cancer: although skin cancer is more common in people with light skin (melanin, the pigment that makes your skin dark is also protective), people with dark skin can also get skin cancer.

Video: How does cancer spread through the body?

Cancer usually begins with one tumor in a specific area of the body. But if the tumor is not removed, cancer has the ability to spread to nearby organs as well as places far away from the origin, like the brain. How does cancer move to these new areas and why are some organs more likely to get infected than others? Ivan Seah Yu Jun explains the three common routes of metastasis in the TED-Ed video below.

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