Detailed Guide: Bile Duct Cancer
Do We Know What Causes Bile Duct Cancer?
While we do not know the exact cause of most bile duct cancers, researchers have found several risk factors that make a person more likely to develop bile duct cancer. There seems to be a definite connection between this cancer and anything that irritates the bile duct, whether it‘s chronic inflammation or infestation with a parasite.
Even when a person with bile duct cancer has one or more risk factors, it is not possible to be sure which if any risk factors actually caused the disease. And many people who do not have any apparent risk factors still develop this cancer.
Recently, scientists have begun to understand how risk factors produce certain changes in the DNA of cells, causing them to grow abnormally and form cancers. DNA is the genetic material that carries the instructions for nearly everything our cells do. We usually resemble our parents because they passed their DNA on to us. However, DNA affects more than our outward appearance. Some genes (parts of our DNA) contain instructions for controlling when cells grow and divide.
Genes that promote cell division are called proto-oncogenes. When they become abnormal in a cancer cell, they are called oncogenes. Genes that slow down cell division or cause cells to die at the appropriate time are called tumor suppressor genes.
It is known that cancers can be caused by DNA mutations (defects) that activate (turn on) oncogenes or inactivate (turn off) tumor suppressor genes. Some people inherit DNA mutations from their parents that greatly increase their risk for developing breast, ovarian, colorectal, and other cancers. However, inherited oncogene or tumor suppressor gene mutations are not believed to cause bile duct cancers.
Every time a cell prepares to divide into 2 new cells, it must duplicate its DNA. This process is not perfect and copying errors occur. Fortunately, cells have repair enzymes that proofread the DNA, but some errors may slip past. Some people may have faulty DNA repair mechanisms that make them especially vulnerable to cancer-causing chemicals and radiation. Acquired mutations may result from chronic inflammation in the bile duct. Oncogene and tumor suppressor gene mutations related to cancer usually develop during life. Several of these mutations have been found in bile duct cancers. This is different from inherited mutations, which are present before birth.
http://www.cancer.org/docroot/CRI/content/CRI_2_4_2X_Do_we_know_what_causes_bile_duct_cancer_69.asp?rnav=cri