Life in the ER

Amy Lee is impacting the diagnosis and treatment of cancer by peering into the endoplasmic reticulum of cells under stress.

By Lori Oliwenstein

In the beginning, Amy Lee became a scientist for many of the usual reasons: She was curious, always asking questions, fascinated by trying to figure out the mechanisms of biological processes.

Raised in Hong Kong, Lee came to the United States and to the University of California at Berkeley for her undergraduate education and Caltech for her Ph.D., with plans to embark on a career in laboratory research.

Her initial focus was on doing science for the sake of science, more interested in the cell than in the organism around it. That all changed with her sister’s diagnosis and subsequent death from breast cancer, an event that turned Lee into a translational researcher, someone just as determined to impact the diagnoses and treatment of cancer as she is committed to figuring out its cellular origins.

These days, Lee, Ph.D., the Judy and Larry Freeman Chair in Basic Science in Cancer Research, is accomplishing both tasks by peering intently into the interior of cells both normal and malignant—and, in particular, at the endoplasmic reticulum, or ER.

The ER is the place in a cell where all the proteins that will ultimately be secreted or expressed on the cell’s surface are synthesized; it is also where calcium is stored. In the case of cancer, the ER is less critical in the genesis of a malignancy than it is in the cancer’s hardiness.

Tumor cells are feisty. Just when they seem to be beat, they somehow manage to regain the upper hand.

“When you look at the successful cancer therapies, they often lose efficacy over time because of resistance in the tumor cells,” Lee notes. “The majority of patients today die not from a primary tumor, but from a failure of the body to overcome the development of resistance to the drugs that treat that tumor.”

Cancer cells tend to fight back when they are threatened—and chemotherapy is certainly a threat. Lee says one of the main players in this response is the ER. “The environment of cancer includes oxygen and glucose starvation,” she explains. “This turns on the ER stress response.”

It is at this particular point in the process that Lee, professor of biochemistry and molecular biology at the Keck School of Medicine of USC and associate director for basic research at the USC/Norris Comprehensive Cancer Center, is currently focusing her studies of ER stress. She is concentrating on a protein called glucose regulated protein 78, or GRP78. What GRP78 does in a cell is bind calcium and chaperone proteins, folding them into proper forms and preventing them from aggregating. GRP78 is a master regulator of the ER since, as a chaperone, it can lock key ER proteins in an inactive state, preventing them from firing their signals from the ER.

“And, most significantly,” Lee notes, “in terms of cancer, it can block the cell death pathway.”

Lee is widely considered one of the leaders in the study of ER stress. She and her coworkers were the first in the world to clone the genes for GRP78 and the related protein GRP94, and to show just how those genes are regulated and transcribed, which means scientists can control the genes’ expression in cells. And that, says Lee, is “a very powerful tool.” This work has been continually supported by the National Cancer Institute since 1979 and also received additional recognition from the NCI in the form of a prestigious MERIT award.

And it is this work that has led Lee to focus on the way GRP78 is naturally expressed in cancer cells in response to stress, and to a new hypothesis published in the journal Cancer Research in July. In essence, the paper concludes that anti-angiogenesis drugs that target the formation and upkeep of blood vessels can starve cancer cells of glucose and oxygen. This can force the cancer cells into a survival mode in which they turn on genes such as the GRP78 gene that can help them both resist and survive the onslaught.

“Likewise, when a tumor—under the attack of conventional chemotherapy drugs that target the replicating cancer cells—is trying to survive and grow, the cells turn on this protective mechanism,” she says. “In fact, I think it’s an innate property of a cancer cell to exploit this survival mechanism, which is used to protect normal cells during stress.”

To emphasize that point, Lee cites a letter she and her colleagues published in the journal Nature Medicine in 2004, in which they showed, in a newly developed mouse model, that ER stress proteins are highly expressed in embryos in the organs that are under the most pressure to perform. “In embryos, the stress proteins help them to survive, so they are the good guys,” she says. “But if these cells become cancer cells, and are able to turn on this survival mechanism, they have a new kind of advantage.”

And that advantage can, when unopposed, give the cancer cells the ultimate victory. “The induction of these protective genes is a survival mechanism that allows a small number of cells to become resistant to the chemotherapy’s effects,” Lee explains. “When the therapy is withdrawn, these cells flourish.”

GRP78 levels also can be elevated in adult cells under stress conditions as a protective measure. Lee and her colleagues showed that GRP78 levels were greatly increased in breast cancer tumors that survived the action of anti-vascular drugs like combretastatin A4P and contortrostatin, an anti-tumor protein pioneered by Frank Markland, Ph.D., Keck School professor of biochemistry and molecular biology and associate dean of scientific affairs. “We further show that GRP78 is overexpressed in a panel of human breast cancer cells that has developed resistance to a variety of drug treatment regimens,” the paper’s authors add.

Also, Lee and her colleagues showed that tumor cells in which the GRP78 gene is suppressed are unable to mount a resistance to the chemotherapy drug etoposide, which damages replicating DNA.

Lee says the study shows a way to get around these cellular defenses. She says, “One approach is to create combination therapies using drugs to counteract stress proteins like GRP78.”

Lee is collaborating with colleagues at USC/Norris and in various departments throughout the Keck School of Medicine. For instance, she was awarded a grant from the Susan G. Komen Breast Cancer Foundation to investigate GRP78 as a predictor for drug resistance and survival, a study she is undertaking with Peter Nichols, M.D., professor of clinical pathology and director of the Norris Hospital Laboratories, Darcy Spicer, M.D. associate professor of medicine, and Mimi Yu, Ph.D., professor of preventive medicine. In an NCI-funded project, Lee and associate professor of neurosurgery Thomas Chen, M.D., will examine the role of GRP78 in drug resistance in brain tumors. As a recipient of a Department of Defense Concept Award, Lee will study how the GRP stress system might allow breast cancer cells to overcome anti-estrogen therapy, in conjunction with the Women’s Cancer Program at USC/Norris. Her laboratory also has ongoing collaborations with Jacek Pinski, M.D., Ph.D., assistant professor of medicine, and Richard Cote, M.D, professor of pathology and urology and director of the genitourinary cancer program, to study GRP78 and prostate cancer.

While GRP78 is the focus of Lee’s laboratory right now, it is not the only line of research. A bit of serendipity led to another area of research exploration underway with Robert Chow, M.D., Ph.D., Keck School associate professor of physiology and biophysics. Originally, Lee and her colleagues were creating a mouse model to study gene regulation in the whole organism. “Then, by accident,” Lee recalls, “one of the transgenes popped into one of the calcium receptor genes critical for calcium control in the ER of brain cells and pancreatic cells that produce insulin.”

This had some fairly significant implications. “When these mice age, they become obese and develop type 2 diabetes.” Lee says. Their level of obesity and hyperglycemia is about 30 percent above normal, which resembles what is seen in humans with the disease. The mouse model, she says, allows the study of how significant disturbance of calcium control in the brain and pancreas may bring on obesity and type 2 diabetes. A grant from the National Institute of Diabetes & Digestive & Kidney Disease supports this work.

Although Lee was led to this sort of hands-on, patient-centered research by her sister’s death, she still feels a great deal of gratitude for the people and institutions that have allowed her to continue to make such critical strides in research.

“It was sobering to realize that no matter how great you are as a scientist, there is so much more to learn to battle cancer and other crippling human diseases,” she says. In particular, Lee credits Brian Henderson, M.D., dean of the Keck School of Medicine, for “motivating me to move my lab to the USC/Norris Cancer Center. My colleagues at USC/Norris really opened up my eyes to all this translational potential,” Lee says.

Her shift in scientific focus and energy opened her eyes even wider. She says, “To make a discovery that presents a new paradigm, to move the field of cancer treatment forward, makes a big difference to me and, I hope, a big difference for the patients.”