Multiple myeloma is notoriously difficult to treat. The cancer forms when a plasma cell — the very type of white blood cell we rely on to keep us healthy by defending against dangerous pathogens — mutates and begins dividing uncontrollably, embedding into the bone marrow at various points throughout the body. The onslaught of abnormal myeloma cells crowds out healthy cells that carry oxygen and fight infection, causing anemia, fatigue, bone pain, kidney failure, and a compromised immune system.

The outlook for the 15,000 patients who are diagnosed annually with multiple myeloma is grim. They can expect to live for three to four years at most. It's been a generation since any new therapies have been developed. Treatment usually takes a one-size-fits-all approach, involving untargeted drugs that may have little effect on the cancer cells they are intended to kill, while often causing a number of serious side effects including nausea, fatigue, diarrhea, cramping, and more.

"Right now, treatment for multiple myeloma is not personalized," says P. Lief Bergsagel, M.D., one of the lead investigators in the Mayo Clinic's Multiple Myeloma Research Program.

A New Center Bears Fruit

Recognizing the need for new multiple myeloma treatments, Mayo Clinic united three pioneers in the genetics of myeloma at Mayo's Scottsdale campus in 2005. Dr. Bergsagel is internationally recognized for identifying genetic changes which cause myeloma. Rafael Fonseca, M.D., researches the clinical significance of these genetic changes and the implications on patient care. Keith Stewart, M.B.Ch.B. (the U.K. equivalent of M.D.) identifies drugs to target the genes involved in the majority of cases.

In collaboration with colleagues at the Translational Genomics Research Institute (TGen) they are focusing their research on drug development and genomics. TGen is a non-profit organization that uses innovative advances arising from the Human Genome Project and applies them to the development of earlier diagnostic tools and more effective treatments.

The collaboration is bearing fruit. The research team has been instrumental in a series of discoveries that are helping to reveal:

• Genetic events that initiate multiple myeloma
• Therapies that specifically target myeloma's genetic abnormalities to stop cancer growth
• How to tailor drug treatments to increase effectiveness and minimize side effects

"Our goal is to deliver individualized care based on the latest genomic information and drugs available," Dr. Bergsagel says. "We intend to find ways to offer the right drug to the right patient each time. And we're set to be among the first to make it happen for patients with multiple myeloma."

Flicking the Switch

In 2003, the Food and Drug Administration approved the drug bortezomib—manufactured under the name Velcade®—to be used in clinical trials for patients with multiple myeloma who were treated unsuccessfully with at least two courses of chemotherapy. Administered in high intravenous doses, bortezomib killed tumors in some myeloma patients, but not others. The Mayo researchers wondered why. "By learning how bortezomib kills cancer, we can identify the patients it works best in," says Dr. Stewart. "And we can tailor the medication so it's less toxic and more effective."

Different drugs affect various genetic pathways—the set of interactions between a group of genes—by turning genes "on" or "off" and thereby changing the role those genes play in the human body. Bortezomib is a proteasome inhibitor: it disables groups of enzymes that control cell function and growth. The drug works through a genetic pathway called Nuclear Factor kappa B (NFkB), which plays a key role in regulating immune system processes. And it's the immune system gone awry that helps spawn multiple myeloma.

Scientists have long known that certain genes play an important role in cancer development, and had previously noted that the NFkB pathway is active in a number of cancers. However, no genetic proof of abnormal NFkB activity had been linked with multiple myeloma. Working with the knowledge that high doses of bortezomib kill myeloma in some cases and that it affects the NFkB pathway responsible for immune cell growth, the group set out to investigate its potential for targeted therapy.

Finding Their Target

To learn how bortezomib works, the research team employed a recently-developed process known as RNA interference (RNAi) screening. Genes normally do their job by converting a DNA sequence into messenger RNA, which then serves as a template to create functional cellular proteins. RNAi controls how genes work by using short strands of DNA as chemical "scissors" to clip a gene into pieces, thereby stopping it from being converted to functioning cellular proteins. It's similar to cutting a phone line in order to keep two people from calling each other. The gene experiencing RNAi is chemically turned "off," masked or inactivated, and is unable to communicate with or influence the rest of the pathway. Scientists can manufacture RNAi "scissors" to affect any gene in the body.

The investigators pool resources with fellow members of the Mayo Clinic Cancer Center. The center is located in three sites: Jacksonville, Fla., Rochester, Minn., and Scottsdale, Ariz. and is the only NCI-designated cancer center with a national presence. The joint effort has secured multiple myeloma cells from 68 patients and 42 unique human myeloma cell lines. Using an arrayer robot, the investigators screened the myeloma cells into individual wells, and then added a different RNAi "scissor" to each well, each one designed to deactivate a specific kinase gene in the pathway. Kinases are enzymes that have profound effects on the activity levels of individual cells. They belong to the single largest family of enzymes, numbering over 500 and accounting for almost two percent of the total proteins encoded by the human genome.

"And then we look to see if the cancer cell dies when we turn the gene off," Dr. Stewart explains. "Then we turn off the next gene—did that kill the cancer cell? And so forth."

The investigators hoped that systematically using RNAi to shut down each protein kinase gene in the cancer cell would identify which active genetic components were necessary for the disease to survive and proliferate.

Most researchers use RNAi screening to examine one gene at a time, but the framework provided by the Mayo Clinic Cancer Center, in collaboration with other strategic partners, allowed the investigators to examine the more than 500 types of kinases.

Satisfying Results

The investigators discovered a number of genetic mutations that correlate to cell function, including alterations in the NFkB pathway, as well as nine genetic mutations in the cancer cells themselves. For the first time, the investigators were able determine a genetic basis for inappropriate NFkB activation in almost half of multiple myeloma patients. Several new genes that regulate cell growth were identified. Turning these "off" activated the NFkB pathway, which spurred uncontrolled myeloma cell growth. When the genes were turned back "on," the cancer cells stopped growing and died.

"These genetic mutations make myeloma more dependent on the NFkB pathway," says Dr. Fonseca. "And that makes them more susceptible to bortezomib treatment."

"Before this study, bortezomib seemed to work in only about one-third of the patients and it was difficult to predict which ones," Dr. Bergsagel explains. "But reversing the myeloma-specific mutations that we identified increased the patients who respond to the drug to 95 percent. .Now we're working on a simple way to identify patients who are the best candidates for use of proteasome inhibitors such as bortezomib." The discoveries increase the potential for the development of drugs that will effectively turn "off" the cancer-causing genes with limited side effects, and thereby ramp up the power of radiation and chemotherapy to kill cancer cells.