Robert Oshima graduated from the University of California Santa Barbara in Cellular Biology. He earned his PhD from the University of California at San Diego in 1973 with Paul Price. He joined Dr. Jerry Schneider’s laboratory in the UCSD Medical School to work on the biochemistry of cystinosis, a genetic lysosomal storage disease. During that time, he contributed to the development of a treatment that extends the life of patients greatly. He acquired expertise in developmental biology and stem cells in the laboratories of Drs. Boris Ephrussi and Mary Weiss at the Centre National Recherche Scientifique, Gif-sur-Yvette, France in 1975. He continued those studies upon returning to UCSD and then moved to MIT in 1979 where he purified two markers of mouse stem cell differentiation that are widely used in the cancer pathology and developmental studies. He joined the Sanford Burnham Prebys (formerly known as the La Jolla Cancer Research Foundation) in 1982 where he acted as Associate Scientific Director, a Program Director in the NCI designated Cancer Center, Postdoctoral Training Program Director, started the Tumor Analysis Shared Service and directed research on stem cells and cancer that resulted in over 100 publications. He also served as a reviewer for multiple cancer research granting agencies and taught at UC San Diego as an Adjunct Professor of Pathology from 1997. He is currently Professor Emeritus (2015) and continues to advise and consult in cancer research. His particular cancer research interest is in methods of directing premalignant cancer cells to adopt a normal benign cell fate instead of becoming invasive malignant cancer.
Related Disease
Breast Cancer, Colorectal Cancer, Crohn’s Disease (Colitis), Preeclampsia
Cancer and development are closely related processes. The Oshima laboratory investigates the differences between normal stem cells and cancer stem cells. Furthermore, we are searching for genes and chemical compounds that control the differentiation of cancer cells and persuading them to adopt a normal developmental fate. Differentiation therapy has the promise of causing fewer deleterious side effects than killing cancer cells.
Robert Oshima’s Research Report
Stem Cells in Breast Cancer and Placental Development
Ets2 is one of a family of transcription factors that all utilize a conserved Ets protein domain for DNA binding. Like its Drosophila homologs, pointed and yan, Ets2 is regulated by growth factors and oncogenes that use Ras signaling pathways. The phosphorylation of a single threonine residue in an evolutionarily conserved protein-docking domain of Ets2 results in transcriptional activation and the induction of Ets2-dependent genes.
Early mouse placental development is dependent on the function of the Ets2 transcription factor. Ets2 regulates trophoblast stem (TS) cell self-renewal and thus placental development. One of the genes regulated by Ets2 in TS cells is the Cdx2 homeobox transcription factor. In collaboration with Dr. Mana Parast at UCSD, we extended our interest in placental development by developing a model system of human placental development. Human embryonic stem cells (ESC) and induced pluripotent stem cells (IPSC) can differentiate in culture to a trophoblast like derivative. We are screening chemical libraries by high content antibody staining methods for chemicals that improve the yield of trophoblast progenitors and direct their differentiation to either extra villous, invasive trophoblast cells or synchiotrophoblast layers.
Recently, we developed methods for the selective propagation of mouse mammary cancer stem cells in culture (Castro et al. Stem Cells 2013). These cells were shown to be capable of differentiation to a benign luminal epithelial-like fate both in culture and in animals. Inhibition of ROCK1 kinase inhibited both their spontaneous differentiation to luminal epithelial cells and their adoption of a mesenchymal tumorigenic phenotype.
Previously, in collaboration with Dr. Alexey Terskikh, we investigated the role of the Maternal Embyronic Leucine Zipper Kinase (MELK) in normal mammary epithelial stem cells and mouse mammary cancer. Using a transgenic reporter gene for Melk expression, we found that Melk expression is preferentially expressed in proliferative mammary epithelial progenitor cells and tumor cells. Both tumorsphere formation in culture and tumor formation in vivo is suppressed by knocking down Melk expression with Lentiviral-mediated shRNA in MMTV-Wnt1 tumor cells. These results have recently been confirmed in human triple negative breast cancer cells.
Furthermore, the development of differentiation therapy came from a collaborative project with Pfizer. Administration of bosutinib, a Src family inhibitor, to mice with mammary tumors caused by the MMTV-PyMT oncogene greatly restricted tumor progression by inducing differentiation of the tumor to epidermal and lactational cell fates without widespread cell death. This is an example of the possibility of restricting cancer by inducing differentiation.
Figure 1. Regulation of cancer stem cell differentiation by low oxygen atmosphere. Single cancer stem cells were plated in two different concentrations of O2 and stained for markers of luminal (K8) or basal (K14) epithelial cells. In 20 percent O2 differentiated cells expressing only K8 or K14 are observed. (Castro et al. 2013)
Figure 2. Presumptive trophoblast derivatives on the top of an hES cell colony, identified by keratin 7 staining (red). Nuclei stained by DAPI (blue). (Maurer et al. 2008)
