What Causes Bladder Cancer?

Researchers do not know exactly what causes most bladder cancers. But they have found some risk factors (see Bladder Cancer Risk Factors ) and are starting to understand how they cause cells in the bladder to become cancer.

Certain changes in the DNA inside normal bladder cells can make them grow abnormally and form cancers. DNA is the chemical in our cells that makes up our genes, which control how our cells function. We usually look like our parents because they are the source of our DNA, but DNA affects more than just how we look.

Some genes control when cells grow, divide into new cells, and die:

• Genes that help cells grow, divide, and stay alive are called oncogenes.
• Genes that normally help control cell division, repair mistakes in DNA, or cause cells to die at the right time are called tumor suppressor genes.

Cancers can be caused by DNA changes (gene mutations) that turn on oncogenes or turn off tumor suppressor genes. Several different gene changes are usually needed for a cell to become cancer.

Acquired gene mutations

Most gene mutations related to bladder cancer develop during a person’s life rather than having been inherited before birth. Some of these acquired gene mutations result from exposure to cancer-causing chemicals or radiation. For example, chemicals in tobacco smoke can be absorbed into the blood, filtered by the kidneys, and end up in urine, where they can affect bladder cells. Other chemicals may reach the bladder the same way. But sometimes, gene changes may just be random events that sometimes happen inside a cell, without having an outside cause.

The gene changes that lead to bladder cancer are not the same in all people. Acquired changes in certain genes, such as the TP53 or RB1 tumor suppressor genes and the FGFR and RAS oncogenes, are thought to be important in the development of some bladder cancers. Changes in these and similar genes may also make some bladder cancers more likely to grow and spread into the bladder wall than others. Research in this field is aimed at developing tests that can find bladder cancers at an early stage by finding their DNA changes.

Inherited gene mutations

Some people inherit gene changes from their parents that increase their risk of bladder cancer. But bladder cancer does not often run in families, and inherited gene mutations are not thought to be a major cause of this disease.

Some people seem to inherit a reduced ability to detoxify (break down) and get rid of certain types of cancer-causing chemicals. These people are more sensitive to the cancer-causing effects of tobacco smoke and certain industrial chemicals. Researchers have developed tests to identify such people, but these tests are not routinely done. It’s not certain how helpful the results of such tests might be, since doctors already recommend that all people avoid tobacco smoke and hazardous industrial chemicals.