Cancer Cell Biology Program Scientific Achievements, 2008-2009
Overview
From Oct.1st, 2008-Oct.31st, 2009, members of Cell Biology published more than 105 full-length, peer-reviewed cancer-related papers. Of these, 27 (36%) were inter-programmatic collaborative publications, 1 (1%) were intra-programmatic publications; 15 (14%) were both intra-programmatic and inter- and intra-programmatic publications.Therefor 43 (41%) were collaborative publications. Seventeen of the manuscripts appeared in high-visibility journals, including Blood, Cancer Research, Cell, EMBO Journal, Genes and Dev, Molecular Cell, Molecular Cellular Biology, Oncogene, PNAS, and Nature. View the list of publications..
Program activities are critical to the scientific progress of the Program membership because they promote interactions that would not otherwise take place. Activities occur at two levels: (1) a seminar program and mini-symposia for the entire Cell Biology membership (and other Cancer Center members). The program also collaborates with other programs in sponsoring events and (2) discussion groups and journal clubs within the program's three subgroups.
The seminar program entitled "Cells, Development and Cancer" features seminars by outstanding invited speakers. A consortium of four interest groups (Departments of Pediatrics, Oral Craniofacial Biology and Cell Biology, Stem Cells and Development and the CCB program) including the Cancer Center, has made this series possible. Examples of important speakers in last year are Dr. Virginia Zakian (Princeton), "Maintaining Telomeres and distinguishing them from Double Strand Breaks", Dr. Zena Werb (UCSF), "The role of stem and progenitor cells as an origin of breast cancer", and Dr. Joseph Nevins (Duke) "Genomic Dissection of Cell Signaling Pathways - Opportunities for Personalized Cancer Therapy". Dr. Werb was also co-sponsored by the HRM program.
The Cancer Cell Biology Program co-sponsored two translational Mini-Symposia with the Molecular Oncology and Developmental Therapeutics Programs: "Structural Biology in Cancer Drug Design" in 2008 and "RNA and Cancer" in 2009.
"Structural Biology in Cancer Drug Design" invited the following plenary speakers: John Kuriyan (U. California Berkeley), Kate Ferguson (U. Penn.), David Cowburn (NY Structural Biology Center) Tomi Sawyer (Aileron Therapeutics) Stephen Burley (SGX Pharmaceutical), Brian Blagg (U. Kansas), Maurizio Pellecchia (Burnham Institute) and Rick Artis (Plexxikon).
"RNA and Cancer" invited the following plenary speakers: Drs. Nahum Sonneberg (McGill University, Quebec, Canada), Muneesh Tewari (Fred Hutchinson Cancer Center), Robert Schneider (NYU), Eric Olson (U. Texas SW), Johan Slog (Mass. Gen. Hospital) and Stuart Peltz (PTC Therapeutics,NJ).
Cancer Cell Biology Principal Investigator / Program Director (Last, First, Middle): Byers, T.E. (P30 CA046934)
Proliferation and Apoptosis
The major effort of the Proliferation and Apoptosis focus group continues to be in signal transduction, cell cycle control and cell death by apoptosis and autophagy, working from the hypothesis that drugs affecting these processes could be potential targeted cancer therapies and also could be used in cancer chemoprevention.
Dr. Hansen (CB) in collaboration with Drs. Tyler (MO) and Lucia (HRM) published a study in Nature (1) demonstrating that acetylation of histone H3 on K56 is an important biomarker in cancer cells. In this high-profile translational study, a molecular biologist (Dr. Tyler), a pathologist (Dr. Lucia) and a proteomics biochemist (Dr. Hansen) collaborated. They showed that in response to DNA damage, histones bearing acetylated K56 are assembled into chromatin in Drosophila and human cells, forming foci that co-localize with sites of DNA repair. Furthermore, acetylation of H3K56 is increased in multiple types of cancer, correlating with increased levels of ASF1A in these tumors.
Dr. Hansen (CB) is also collaborating with Dr. Thorburn (CB) in studying autophagy (2). Dr. Thorburn (CB) is an expert in apoptosis, autophagy and in TRAIL-mediated killing of cancer cells. (3,4,5).
Drs. Graham (CB) and Keating (CB) collaborated with Dr. DeRyckere (DT) to show that the oncogenic Mer receptor tyrosine kinase is a novel therapeutic target in acute lymphoblastic leukemia (ALL) (6). In this paper, they show that ectopic expression of Mer increased the sensitivity of B-ALL cells to cytotoxic agents in vitro by promoting apoptosis, and delayed disease onset in a mouse model of leukemia. Their results identify Mer as a novel therapeutic target in ALL and suggest that inhibitors of Mer will interact synergistically with currently used therapies. This strategy may allow for dose reduction resulting in decreased toxicity and increased survival rates. Mer is aberrantly expressed in numerous other malignancies suggesting that this approach may have broad applications.
Dr. DeGregori (CB) collaborated with Drs. Porter (DT), Hodges (MO) and Eisenmesser (MO) to solve the solution structure of the extracellular region of CD147 with enzyme ligand cyclophilin A (7). The CD147 receptor plays an integral role in numerous diseases by stimulating the expression of several protein families and serving as the receptor for extracellular cyclophilins. In cancer, CD147 overexpression underlies tumorigenesis and CD147-mediated stimulation of MMPs (matrix metalloproteinases) is a critical part of metastasis. They characterized the solution behavior of the two most prevalent CD147 extracellular isoforms through biochemical methods that include gel-filtration and native gel analysis as well as directly through multiple NMR methods. All methods indicate that the extracellular immunoglobulin-like domains are monomeric in solution and, thus, suggest that CD147 homophilic interactions in vivo are mediated through other partners. Additionally, using multiple NMR techniques, we have identified and characterized the cyclophilin target site on CD147 and have shown for the first time that CD147 is also a substrate of its primary cyclophilin enzyme ligand, cyclophilin A.
Dr. Espinosa (CB), who was awarded a prestigious Howard Hughes Medical Institute (HHMI) career development award, continues his productive collaboration with Dr. Taatjes (MO). They showed that the oncoprotein CDK8 forms a complex with cyclin C, Med12, and Med13 to form a stable "CDK8 subcomplex" in cells. This complex is an important regulator of transcription by RNA polymerase II. Mass spectrometry analysis of the endogenous CDK8 subcomplex reveals several associated factors, including GCN1L1 and the TRiC chaperonin, which may help control its biological function and provide insight into CDK8’s role in cellular transformation (8).
Dr. Shellman (CB) in collaboration with Drs. Norris (II) and Fujita (II) demonstrated that the BH3 mimetic ABT-737 and a proteasome inhibitor synergistically kill melanomas through Noxa-dependent apoptosis (9). The Bcl-2 family is important in modulating sensitivity to anticancer drugs in many cancers, including melanomas. The BH3 mimetic ABT-737 is a potent small molecule inhibitor of the anti-apoptotic proteins Bcl-2/Bcl-X(L)/Bcl-w. Their findings demonstrate that ABT-737 combined with MG-132 synergistically induced Noxa-dependent mitochondrial-mediated apoptosis. In summary, this study indicates promising therapeutic potential of targeting anti-apoptotic Bcl-2 family members in treating melanoma, and it validates rational molecular approaches that target anti-apoptotic defenses when developing cancer treatments.Cancer Cell Biology Principal Investigator / Program Director (Last, First, Middle): Byers, T.E. (P30 CA046934)
Dr. Maller (CB-HHMI), an expert in the role of protein kinases in cell cycle regulation, has found that Aurora A kinase, a known oncogene, is activated by TPX2 kinase, which is in turn activated by phosphorylation by Plx1 (polo like kinase) (10). His laboratory proposes a model in which Plx1 and Aurora A activate each other in a positive feedback loop for entry into mitosis. TPX-2 kinase also regulates the p53 oncogene through its regulation of Aurora A kinase (11). Based on these results, targeting of TPX2 might be an effective strategy for specifically inhibiting the phosphorylation of Aurora A substrates, including p53. Drs. Maller (CB) and Schiemann (CB) have started a collaboration to study the DNA damage checkpoint regulator Repo-Man in breast cancer cells. Repo-Man is a phosphatase that inhibits checkpoint activation. They find that Repo-Man is overexpressed in many breast cancers and cell lines, suggesting that inhibition of checkpoint activation leads to genomic instability and tumorigenesis.
Dr. Sclafani (CB) continues his successful collaboration with Dr. R. Agarwal (PC, HRM) and Dr. C. Agarwal (PC) in studying the mechanism of cancer chemoprevention by the natural products with NCI-support. They showed that the CDK (cyclin-dependent kinase) inhibitors p21/Cip1 and p27/Kip1 are essential molecular targets of inositol hexaphosphate (IP6) for its antitumor efficacy against prostate cancer (12). In tumor xenograft studies, IP6 caused a comparable reduction in tumor volume and tumor cell proliferation in DU145 prostate cancer tumors but lost most of its effect in cells in which both p21 and p27 were knocked-down. IP6-caused apoptosis also occurred in a Cip/Kip-dependent manner because double p21 p27 knockdown cells were completely resistant to IP6-induced apoptosis both in cell culture and xenograft. In contrast, single p21 ro p27 knockdowns had no effect. In this publication, they provide evidence for the critical role of p21 and p27 in mediating the anticancer efficacy of IP6, and suggest their redundant role in the anti-proliferative and pro-apoptotic effects of IP6 in p53-negative human prostate cancer cells.
Drs. Sclafani (CB) and Agarwal (PC, HRM) are also are interacting with both clinical investigators, Drs. Raben (LHN, DT), and Jimeno (DT) and with other basic scientists (Frederick (DT)) to use a pre-clinical animal model to test if the natural compound Resveratrol can be used to increase the efficacy of radiation in treatment of head and neck cancers. Their studies are based on their previous work showing that Resveratrol activates the DNA damage checkpoint in ovarian cancer cells (13). Along these lines, Dr. Sclafani obtained a grant from the NCI-supported CCTSI (Colorado Clinical and Translational Sciences Institute- UL1-RR025780) to investigate the effect of Resveratrol on Radiation in Head and Neck Cancer cells. They are interacting with the Head and Neck cancer group under the supervision of Dr. Xiao-Jing Wang in the Department of Pathology, who is an expert in animal models of head and neck cancers. Dr. Wang (LHN) is also interacting with Dr. Roop (CB), whom she has collaborated with for many years. Both Drs. Roop and Dr. Wang were recruited to UCCC just several years ago.
Membrane Receptors and Traffic
This focus group continues to be important in cancer research especially with the advent of growth factor therapies that employ EGF and erbB2 inhibitors such as gefitinib (Iressa) and trastuzumab (Herceptin), respectively. These receptors are transmembrane proteins that are selectively accumulated in clathrin-coated pits at the plasma membrane and rapidly internalized in clathrin-coated vesicles. Many cancer cells may become resistant to these therapies because of defects on normal receptor turnover and recycling. Furthermore, endocytic membrane traffic is also important for cell movement, a hallmark of invasive and metastatic cancer cells.
Dr. Sorkin (CB) is a leader in this field (14). His laboratory performed a high-throughput RNA interference screen to identify proteins that regulate the levels of epidermal growth factor receptor EGFR in squamous cell carcinoma (15). Elevated expression EGFR contributes to the progression of many types of cancer and is the target of therapy in several cancers. They identified Usp18, which is a member of the ubiquitin-specific protease family and propose a novel mechanism of EGFR regulation at the translational step of receptor synthesis.
Dr. Prekeris (CB) is studying the cell adhesion and motility, which are very dynamic processes that require the temporal and spatial coordination of many cellular structures. He showed that ADP-ribosylation factor 6 (Arf6) has emerged as master regulator of endocytic membrane traffic and cytoskeletal dynamics during breast cancer cell movement (16,17). He proposes that FIP3 protein affects cell motility by regulating Arf6 localization to the plasma membrane of the leading edge, thus regulating polarized Rac1 activation and actin dynamics.Cancer Cell Biology Principal Investigator / Program Director (Last, First, Middle): Byers, T.E. (P30 CA046934)
Development and Cancer
It is clear that many proteins important during normal cell development and differentiation are mis-regulated in cancer cells. Several groups are studying these molecules and how they affect tumorigenesis. The group has great expertise in mouse molecular genetics and in using and creating new mouse models to study cancer. Especially relevant is the EMT, in which there is a change of cells from an epithelial to a mesenchymal morphology, similar to invasive, metastatic tumor cells. Drs. Schiemann (CB) and Nemenoff (CB, LHN) are collaborating in the study of factors that regulate the EMT.
Dr. Schiemann (CB) continued his collaboration with Dr. Nemenoff (CB, LHN). Dr. Schiemann is an expert in determining the mechanism of how Transforming growth factor-beta (TGF-beta) acts master regulator of EMT in normal mammary epithelial cells (MECs). Dr. Nemenoff is an expert in the role of cyclooxygenases in cancer. They investigated the mechanism by which mammary tumorigenesis converts TGF-beta from a tumor suppressor to a tumor promoter (18). Aberrant upregulation of the inducible cyclooxygenase, Cox-2, occurs frequently in breast cancers and is associated with increasing disease severity and the acquisition of metastasis. They show that TGF-beta induced Cox-2 expression in MECs during their acquisition of an EMT phenotype. Cox-2 may act as a novel antagonist of Smad2/3 signaling in normal and malignant MECs and chemotherapeutic targeting of Cox-2 may offer new inroads in restoring the tumor-suppressing activities of TGF-beta in malignant, metastatic breast cancers.
Dr. Schiemann (CB) also showed that Fibulin-5 initiates epithelial-mesenchymal transition (EMT) and enhances EMT induced by TGF-beta in mammary epithelial cells via an MMP-dependent mechanism (19). Fibulin-5 promoted anchorage-independent growth in normal and malignant MECs, as well as enhanced the growth of tumors in mice. Their findings identify a novel EMT and tumor-promoting function for Fibulin-5 in developing and progressing breast cancers.
Stem Cells and Cancer
Epithelial tissues are constantly being renewed in response to injury. Since epithelial tumors are though to arise as the result of the accumulation of genetic damage over many decades, it is logical to conclude that adult stem cells, which are the only cells to remain in these tissues throughout life, are the most likely targets to accumulate enough damage to eventually result in tumor formation. Dr. Roop has been able to use his inducible models to introduce genetic changes in adult somatic stem cells in the skin and recapitulate events that are known to occur in the development of human skin cancers. The p53 tumor suppressor gene is the most frequently mutated gene in human skin squamous cell carcinomas (SCCs). Interestingly, over 70% of p53 mutations found in human SCCs are missense substitutions that result in the expression of mutant forms of p53, rather than loss-of-function mutations. Some of these missense mutations may exhibit gain-of-function (GOF) properties. Using his inducible mouse model, Dr. Roop has obtained the strongest genetic evidence to date that p53 GOF mutations confer poorer prognosis than loss of p53 function in skin cancer. SCCs from GOF p53 mice showed hallmark features of genomic instability such as supernumerary centrosomes, aneuploidy and numerous genomic alterations. His findings highlight the importance of determining the p53 mutation status in an individual patient’s tumor, since the future design of therapies for treatment of tumors that carry p53 GOF mutations should address not only reactivation of the wild type p53 function, but also inactivation of the GOF properties of mutant p53 (20). Dr. Roop has also recently shown that Aurora-A kinase is frequently overexpressed in human skin SCCs (21), and he has generated an inducible mouse model that allows the overexpression of a genetic variant of Aurora A that has been implicated as a cancer susceptibility gene. This mouse model develops aggressive and metastatic SCCs that exhibit centrosome amplification and genomic alterations, indicating that Aurora-A overexpression induces a high level of genomic instability. This is the first mouse model to show enhanced metastasis associated with Aurora-A overexpression, consistent with human studies showing a correlation between Aurora-A overexpression and metastasis, and this model will be useful for testing Aurora A inhibitors (21).
Although it is now generally accepted that adult stem cells which have acquired genetic alterations can expand and cause cancer, the idea that tumors themselves may actually be maintained by cancer stem cells is relatively new and even controversial (22). Dr. Roop and his collaborators, Drs. Wang, Refaeli, Fujita and Jimeno are actively working to prove or disprove the cancer stem cell hypothesis using approaches outlined in Refaeli el al 2009 (22). Cancer Cell Biology Principal Investigator / Program Director (Last, First, Middle): Byers, T.E. (P30 CA046934)
Program Planning and Strategic Development:
As discussed above, following the advice of the UCCC External Advisory board, the Carcinogenesis and Chemoprevention (CC) program was eliminated and members whose research was appropriate for CB program were invited to join the program. The UCCC External Advisory board also recommended that the CB program was too big and needed additional management and leadership. Therefore, Dr. Roop, who was the leader of CC became co-director of CB with Dr. Sclafani.
Dr. Roop and Dr. Sclafani communicate about program membership and both attend the monthly UCCC meetings. Both program leaders are involved with the ongoing search to recruit a new UCCC director, in several faculty searches in several Departments. They are also are involved in the mentoring of junior faculty. The goal of the mentoring program is to produce successful independent basic science and clinical scientists, who collaborate successfully to translate their discoveries into useful information for cancer patient diagnosis, prognosis and therapy.
Planning for a Head and Neck cancer group with the goal of obtaining a Head and Neck Cancer SPORE grant is underway. In addition, Dr. Roop together with Dr. David Norris (program?), Dr. Mayumi Fujita (program?), Dr. Yosef Refaeli (program?) and Dr. Antonio Jimeno (program?) are submitting a Skin Cancer SPORE with Dr. Marianne Berwick of the University of New Mexico in January, 2010. Cell Biology program leaders Drs. Sclafani and Roop attend the bi-weekly Head and Neck cancer research seminars that are organized by Dr. Wang (LHN) to this end.
UCCC Cores:
Cancer Cell Biology members could not accomplish their work without using the various Shared Resources; especially the Tissue Culture, Flow Cytometry, DNA Sequencing and Analysis, Structure, Proteomics, Small Animal Imaging and Laboratory Animal Cores. The program leaders communicate with Dr. Thorburn, Associate Director of Basic Sciences regarding any problems with these cores. They also query the membership about any problems or desired new technologies and then meet with both core directors and Dr. Thorburn.