As we alluded to previously here, not everyone has the same risk of developing cancer. By studying the characteristics of patients who have bladder cancer, researchers have been able to identify groups of people who seem to develop the disease more often than others. These groups of people each have some risk factor that they are born with, things that predispose them to cancer no matter how carefully they live their lives. In fact, our genetic makeup probably plays the biggest role in deter-mining who among us is destined to get cancer.
Race: Different races have different risks of bladder cancer. Caucasian (white) Americans are twice as likely to develop transitional cell cancer (the most common type of bladder cancer), as are African Americans. For the more rare type of bladder cancer, called squamous cell cancer, however, the reverse is true; African Americans are twice as likely to develop squamous cell cancer of the bladder than are white individuals. Of all the different races, Caucasians seem to have the highest rate of bladder cancer.
Gender: Men are almost three times more likely to develop cancer than women. This is before taking into consideration modifiable risk factors such as smoking and workplace exposures to chemicals.
Age: More than 65% of bladder cancer occurs in patients who are older than 65. Patients in this age group are also more likely to develop more aggressive tumor types than are the younger bladder cancer patients.
Genetics: As you may remember from the prior discussion, cancer develops only after something goes haywire in the regulatory process of cell growth or cell death. Several different genes normally accomplish this regulation. In a normal, healthy cell, these genes promote growth or suppress growth or can even signal a cell to destroy itself in an appropriate situation. For a cell to become cancerous, many of these genes must be altered or destroyed simultaneously. Nature has even supplied our cells with other genes that are able to repair damaged genes. These “repairmen” genes are known as tumor suppressor genes.
Their job is to repair damaged DNA when possible or to drive a damaged cell to destroy itself. The net result of these processes is to strike a balance of new cell growth and old cell death. You can imagine that if there were damage to the process that removes cells, then these cells would begin to accumulate. If many other cells also were missing this signal, they might all live too long, causing an overgrowth of cells that we refer to as a tumor. If the cells simply accumulate, then we call the tumor benign. If the cells are able to escape from the main tumor and begin to accumulate in other organs, we refer to the tumor as malignant.
Fortunately, nature is not so easily beaten, and there are multiple redundant systems to regulate these cell cycles. For cancer to develop, there needs to be damage to multiple systems at the same time. When cancer runs in a family, it is usually because damage to one or more of these systems is present already, making it much easier to have a failure of regulation later in life. Examples of these genes are the p53 gene or the retinoblastoma (Rb) gene. Damage to p53 is a common genetic change in all types of cancers.Although these systems normally provide tight regulation of cell growth, your body does not always want tight regulation.
Sometimes cells need to be able to reproduce quickly without the constraints of the regulatory genes. Examples of this include the healing phase after an injury or surgery, or during normal growth in childhood. To accommodate these situations, there are other genes in each cell that when activated allow the cell to grow more vigorously. When you break a bone, new bone cells need to move in quickly and replace the damaged tissue.
Your body then needs a way “take off the brakes” to allow growth of certain cell types. A common signal to “hit the accelerator” is called epidermal growth factor and is often abnormal in bladder cancer, especially in more aggressive tumors. These types of genes are known as oncogenes. A gene named the p21 ras oncogene can be found in many bladder cancers. Although oncogenes are not well understood, they may play a role in determining how aggressively a tumor behaves. They appear able to change a low-grade tumor into a higher-grade, more aggressive tumor. Researchers are always identifying new genes and new proteins that are involved in bladder cancer, and each new finding provides a possible route of new therapy to prevent or treat bladder cancer.