In their tireless search for genes responsible for prostate cancers that run in families, William Isaacs, Ph.D., Jun Luo, Ph.D., and Jianfeng Xu, Ph.D., of NorthShore University, and their team have found another gene: MMS22L.

MMS22L is a protective gene: its job is to fix damage to the DNA that can lead to cancer. When this gene, like BRCA2, is knocked out of commission by a faulty genetic code, DNA damage can run amok. “When it’s mutated,” says Isaacs, “it not only increases the lifetime risk of developing aggressive prostate cancer, but has a 50-percent chance of being passed on to the next generation.”

Fortunately, now that MMS22L has been identified, it can be tested for: “We have a simple saliva test that detects some of the defective genetic codes that shut down genes important in protecting our genome, such as BRCA2,” says Luo. “MMS22L can be added to the saliva test.”

MMS22L is probably not responsible for nearly as many cases of prostate cancer as BRCA2, notes Luo, but it is important for those who have this mutation to be aware. Luo likens the team’s long hunt for rare prostate cancer genes to explorations in remote areas. “We say many roads lead to Rome, and now that the major roads are mapped, what about the less-traveled paths? We are essentially trying to map many of these less-traveled paths to Rome. We suspect there are more prostate cancer genes out there. The problem is, it is difficult to identify them because, fortunately, the defective codes are quite rare.”

Isaacs explains: “We have in front of us a map of the human genome that has three billion codes. Our task has been, to a large extent, hunting down the culprits and pinpointing the precise location of the defective codes on the map.” Every code found, he adds, “increases our ability to help patients and their families.”

Every code found, he adds, “increases our ability to help patients and their families.”

In the case of MMS22L, the team discovered a defective code in eight families participating in research within the Patrick C. Walsh Hereditary Prostate Cancer Program. The defective code shuts down this gene. Knowledge is power, and "in men who carry the defective code but have yet to develop the disease, early screening will detect prostate cancer at a time when a cure is possible," says Luo. “In addition, there are promising drugs, such as PARP inhibitors, that may be used to target cancer with these specific types of defective genes.”