Faculty Spotlight: Amy S. Lee

Amy S. Lee (Photo courtesy of USC)
Amy S. Lee (Photo courtesy of USC)

Amy S. Lee’s major research focus is in the area of endoplasmic reticulum (ER) stress and, in particular, the ER chaperone proteins GRP78 and GRP94. Lee was the first to clone human GRP78 and elucidate its regulation and function. The GRPs play essential roles in cellular homeostasis, mammalian development, organ integrity as well as cancer progression and therapeutic resistance. Her laboratory also investigated the regulation and function of GRP94. Currently, she and her collaborators are developing and testing therapeutics targeting GRP78 for application into cancer and other human diseases.

Lee joined USC in 1979 and was the recipient of the American Cancer Society (ACS) Junior Faculty Research Award from 1980-1983 and the ACS Faculty Research Award from 1983–1988. Lee received the MERIT Award from the National Cancer Institute in 1988 for her leading research on the GRPs. In recognition of her pioneering work on ER stress and its impact on cell and cancer biology, she was elected Fellow of the American Association for the Advancement of Sciences (AAAS) in 2006. She was the recipient of the Chinese American Faculty Association of Southern California Achievement Award in 2008. Lee chaired a Major Symposium on the Unfolded Protein Response in Cancer at the American Association for Cancer Research (AACR) Annual Meeting in 2011. In 2012, Lee was the recipient of the USC Mellon Mentoring Award for mentoring of junior faculty members at USC and her commitment to the training mission of USC.

Lee received her Bachelor of Arts degree in Bacteriology and Immunology (Valedictorian) from the Universty of California, Berkeley and her PhD in Biology from the California Institute of Technology. She subsequently received her postdoctoral training and served as a senior research associate at the California Institute of Technology.

We asked Lee, who is also a principal investigator with USC Stem Cell, to answer a few questions about what influenced her decision to focus on her research area, her thoughts on future research and her role as Associate Director for Basic Research at USC Norris Comprehensive Cancer Center.

Your laboratory was first to clone Glucose Regulated Proteins GRP78 and GRP94. What led you to clone these particular proteins?

When I was a graduate student at Caltech, the ability to clone individual genes from mammalian cells ushered in a new era of molecular biology and I was fascinated by it. Thus, when I was offered a faculty position at USC, I started to search for a model system in mammalian cells to study how genes that are not physically linked could be coordinately regulated. The idealism in me urged me to look for something that was entirely new, which had the added advantage that I would have no competitor. As I labored at the Caltech library, an article in a 1978 issue of the journal Nature caught my eye. There, Jose Melero, PhD, and Alan Smith, PhD, of the Imperial Cancer Research Fund, UK, described the coordinated new synthesis of three specific proteins (94, 78 and 58 kilodaltons) of unknown identity in a temperature-sensitive mutant Chinese hamster K12 cell line. Seizing upon this opportunity to uncover the mystery of the K12 system as the cornerstone of my new laboratory and my first National Institute of Health grant, I contacted Melero and he generously supplied the K12 cells. The National Cancer Institute also liked the novelty so I was in business. In 1981, I succeeded in making a small but amazingly high quality cDNA library of K12 cells. Using hybrid selection followed by in vitro translation, I also identified the clones encoding for the 78 and 94 kDa proteins induced in the K12 cells.

At around the time the K12 mutant was isolated in 1977, Ira Pastan, MD, of the National Cancer Institute reported the induction of two viral transformation-sensitive proteins (78 and 94 kDa) in normal fibroblasts by a block in glycoprotein synthesis or glucose starvation, and hence named the proteins “glucose regulated proteins” or GRP78 and GRP94. With near identical molecular masses, we quickly determined the two sets of proteins were identical and hence, serendipitously, I had cloned the first mammalian cDNA encoding GRP78 and GRP94. Importantly, between 1983 and 1986, utilizing the cDNA clones for GRP78 and GRP94 as molecular probes, we demonstrated that ER stress-induced levation of the GRPs stemmed from an increase in mRNA levels. This provided the first clue of the existence of a monitoring system that allows cells to sense ER stress and initiate a transcription program in the nucleus to carry out adaptive measures.

What is the significance of these discoveries in cellular biology?

It turns out GRP78 is no ordinary protein. In 1986, Hugh Pelham, PhD, of the Medical Research Council, UK, isolated an unusual cDNA clone containing a signal peptide, p72, when he was searching for cohorts of the heat shock HSP70 protein family. Strikingly, the mature amino terminal sequence of GRP78 reported by us in 1984 matched the predicted sequence of p72, which Pelham further matched with the immunoglobulin heavy chain binding protein BiP, which functions as a chaperone protein. In 1988, Mary Jane Gething, PhD, and Joe Sambrook, PhD, of the University of Texas Southwestern Medical Center, further demonstrated that malfolded protein induced the synthesis of GRP78 and GRP94. Thus, the two lines of investigation, stress response and chaperone protein merged and in 1992, the term “unfolded protein response” or UPR was born.

The UPR is an intracellular quality control system that senses harmful malfolded protein accumulating in the ER and triggers transcription in the nucleus leading to activation of adaptive pathways for survival, or when the stress is too severe, apoptotic death. The protective mechanisms of the UPR include increasing chaperone protein production and degrading the malfolded proteins. The UPR research area is of high significance in both health and disease, as the UPR can protect normal organs against proteotoxic stress, but can also be usurped by cancer cells, enabling them to thrive and overcome resistance to therapy. Now GRP78 is widely recognized as a benchmark of UPR, a multifunctional protein controlling not only the ER stress sensors but also a range of other pathways inside and outside the ER, and plays critical roles in the many facets of human diseases.
You started out looking for a novel gene regulation mechanism. Did you achieve that goal?

Yes, and the impact is huge. First, we isolated the promoter of the GRP78 and GRP94 genes from different species and looked for conserved sequence motifs. After much hard work, we finally cracked the genetic code for their stress induction. In 1998, at a meeting in Kyoto, Kazutoshi Mori, PhD, of the HSP Research Institute in Kyoto, Japan and I announced, independently, the discovery of the ER stress inducible promoter element common to UPR mammalian target genes. This was a gratifying moment considering that two laboratories, working continents apart, reached the same conclusion. This was a highly significant advancement in UPR research since this made it possible to work backwards and identify molecular pathways leading to their transcription and then, step by step, find the key players mediating the regulation.
Much of your research is in cancer. What influenced your decision to focus in this area?

As the UPR research field exploded in the 1990s, I decided that while in vitro studies can provide clean and elegant readouts in a timely manner, the relevance of the UPR in human disease is largely unknown. My interest in cancer was sparked when Brian Henderson, MD, then the director of USC Norris, convinced me to move my laboratory there in 1993. Since the cancer center is interdisciplinary, the cross-fertilization of ideas with immunologists, pathologists, physician scientists and epidemiologists expanded my horizon beyond gene regulation and UPR biochemistry. In 1996, we obtained the first solid clue linking the UPR and cancer when we injected GRP78-knockdown fibrosarcoma cells into syngeneic, immune competent mice. We were totally amazed that tumors either did not form or they quickly regressed. Armed with this fantastic early result, we proceeded to elucidate the underlying mechanisms and created multiple cancer mouse models to prove that GRP78 is critical for tumorigenesis.

On a personal level, I lost my younger sister Gloria in 1998 to metastatic breast cancer. Her struggle with cancer inspired me to expand my basic research into something more tangible towards a cure for cancer. After many years of persistent pursuit, both in my lab and others, GRP78 has now emerged as a biomarker for aggressive cancer in general and a novel target to combat tumor growth, metastasis and drug resistance.

What other areas of research have you collaborated and how have these collaborations advanced or influenced your own research?

I have the good fortune to collaborate with many colleagues both inside and outside of USC to expand our research beyond cancer. Utilizing the traditional and conditional knockout mouse models for GRP78 and GRP94 created in our lab, we and USC colleagues Louis Dubeau and David Hinton established an essential role of GRP78 in neuronal protection. Other participants in this collaboration was Richard Thompson on neuro-conditioning, Jeannie Chen on retinal degeneration, Gregor Adams and Si Ye Chen on hematopoietic stem cell biology, Beiyun Zhou and Zea Borok on lung fibrosis and Valter Longo on aging. We have also a long term and fruitful collaboration with Jason Kim, PhD, from the University of Massachusetts on understanding the role of GRP78 in diabetes, obesity and insulin resistance. Work from these collaborations and others in the field illustrate beautifully the yin and yang of GRP78 in human biology. Thus, while GRP78 inhibitors can be anticancer, upregulators of GRP78 could confer protection against neurological or metabolic disorders. On that front, we are excited that GRP78 has been recently chosen as a target for drug discovery in a joint effort between USC Norris and the Broad Center for Regenerative Medicine and Stem Cell Research.

What do you think will be the next big advances in your field and what do you think Keck School of Medicine (KSOM) can do to position itself to be a leader in this area?

With new technological advances, we are poised to explore novel angles of GRP and UPR biology. There are many unanswered questions on how and where the GRPs exert their multi-faceted effects. Viewed from this angle, KSOM is wise to upgrade basic science core facilities including superresolution imaging, mass spectrometry and transgenic/genomic editing, as well as maintain momentum in genomics and bioinformatics. On the therapeutic front, the exciting discovery that GRP78 is preferably expressed on the surface of cancer cells suggest that it can be therapeutically targeted as well as serve as a conduit for cancer-specific drug delivery. Here at USC, Parkash Gill, MD, co-leader of the Translational and Clinical Sciences Program at USC Norris, in collaboration with our lab, has isolated a monoclonal antibody against cell surface GRP78 capable of suppressing PI3K/AKT signaling, tumor growth and metastasis. This approach was recently selected for accelerated clinical development in conjunction with the USC Norris – Pfizer Center for Therapeutic Innovation. In the meantime, drugs against UPR pathways are also actively being exploited in the scientific community as novel agents in treating cancer and other diseases. To advance the GRP and UPR field in medicine, we need to move into the patient arena and KSOM should invest in bioengineering, imaging, clinical trials support and in-house facilities for production of therapeutic agents, as well as seek partnership with biotech firms and the pharmaceutical industry.

What advice would you give to junior faculty about being competitive in getting grant funding?

For a grant to be funded in the current climate, you need novelty in the proposed ideas and high impact in your field and beyond. Grants that highlight unusual collaboration of diverse expertise (scientifically and/or technically) to break new ground in the field and can generate excitement. Focus like a laser on your key hypothesis and do not fall into the trap of being over-ambitious by being all over the map.
Finally, you serve as Associate Director for Basic Research at USC Norris. What are your responsibilities and how do they benefit the KSOM community?

One thing that stands out at KSOM is the high level of interactions and collaborations among our faculty members. In my capacity as the Associate Director for Basic Research, I oversee three basic science programs (Molecular Genetics, Epigenetics and Regulation and Tumor Microenvironment), while also providing input to the Translational and Clinical Sciences Program. It is a pleasure to work with the leaders of these programs who bring their passion and commitment to foster interactions and collaborations. I help organize the annual retreat for USC Norris, which brings together researchers from various disciplines (population, basic science and clinical) and highlights a team approach to science and technological advances in cancer research. In many cases, retreat participants yield new ideas and approaches, and lay a foundation for new joint grants and publications.

I also supervise the Basic Science Support Core Facilities funded by USC Norris, which include Molecular and Cell Biology Support, Bioreagent and Cell Culture, Cell and Tissue Imaging, Flow Cytometry and Immune Monitoring, Transgenic/Knockout Rodent and Small Animal Imaging. The cores provide invaluable resources for the whole KSOM community and introduce the latest technology. I actively participate in faculty recruitment efforts related to USC Norris. It has been rewarding to see new faculty members bring in fresh expertise and energy to KSOM and to witness their professional growth throughout the years. Collectively, these activities enhance the scientific environment for the whole KSOM community and help elevate the level of research for all members of KSOM.