We still do not know exactly what causes most bladder cancers. But researchers have found some risk factors (see the section, "What are the risk factors for bladder cancer?") and are beginning to understand how these factors cause cells in the bladder to become cancerous. /ssLINK/bladder-cancer-risk-factors
During the past few years, scientists have made a lot of progress in understanding how certain changes in DNA can cause normal bladder cells to grow abnormally and form cancers. DNA is the chemical in each of our cells that makes up our genes – the instructions for how our cells function. We usually look like our parents because they are the source of our DNA. However, DNA affects more than how we look.
Some genes have instructions for controlling when cells grow and divide. Genes that promote cell division are called oncogenes. Genes that slow down cell division or cause cells to die at the right time are called tumor suppressor genes. Cancers can be caused by DNA changes that turn on oncogenes or turn off tumor suppressor genes. Several different genes usually need to have changes for a cell to become cancerous.
Some people inherit DNA changes from their parents that greatly increase their risk for developing certain cancers. However, bladder cancer does not often run in families, and inherited gene mutations are not thought to be a major cause of this disease.
DNA changes related to bladder cancer usually develop during a person's life rather than having been inherited before birth. These acquired DNA mutations may result from exposure to cancer-causing chemicals. For example, chemicals in tobacco smoke can be absorbed into the blood, filtered by the kidneys, and end up the urine, where they may affect bladder cells. Other chemicals may reach the bladder in a similar way. But in some cases, gene changes may just be random events that sometimes happen inside a cell, without having an external cause.
There does not seem to be a single pathway to bladder cancer that is the same in all cases. Acquired changes in certain genes, such as the p53 or Rb1 tumor suppressor genes and the FGFR oncogene, are thought to be important in the development of some bladder cancers. Changes of these and similar genes may also make some bladder cancers more likely to grow and invade more rapidly than others. Current research in this field is aimed at developing tests that can find bladder cancers at an early stage by recognizing their DNA changes.
Bladder cancers do not often result from inherited mutations in oncogenes or tumor suppressor genes, but some people seem to inherit a reduced ability to detoxify (break down) certain types of cancer-causing chemicals. These people are more sensitive to the cancer-causing effects of tobacco smoke and certain industrial chemicals. Researchers are developing tests that may help identify such people, but these tests are not routinely done. It is not certain how these test results would be used since doctors recommend that all people avoid tobacco smoke and hazardous industrial chemicals.
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