Lee and Zhao Labs: Overview

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Dissect Cancer Pathogenesis by iPSC Approaches

 

After leukemia and brain tumor, osteosarcoma is one of the leading cause of cancer mortality among children. Genetic alterations (e.g., p53 mutation and RB1 deletion) are strongly associated with osteosarcoma development. Patients with Li-Fraumeni syndrome (LFS), a genetically inherited autosomal dominant cancer disorder caused by germline mutations in the p53 tumor suppressor gene, have increased incidence of osteosarcoma development, which provides a perfect model system to study osteosarcoma.

Modeling human genetic disease has recently become feasible with induced pluripotent stem cell (iPSC) methodologies developed by Dr. Shinya Yamanaka in 2006. Characterized by their ability to self-renew indefinitely and differentiate into all cell lineages of an organism like embryonic stem (ES) cells, iPSCs provide a powerful and unlimited source of cells to generate differentiated cells that can be used to elucidate disease pathogenesis, for drug discovery and development, toxicology screening, personalized healthcare and eventually cell transplantation-based therapies.

Our laboratory is dedicated to understanding cancer pathological mechanisms by applying patient-specific iPSCs and/or engineered ESCs (Gingold J et al. Trends Cancer 2016). We have established the first human Li-Fraumeni syndrome (LFS) disease model by using LFS patient-specific iPSCs to delineate the pathological mechanisms caused by mutant p53 in osteosarcoma (Lee, et al, Cell 2015; Zhou et al. Trends Pharmacol Sci 2017; Kim et al. PNAS USA 2018). LFS iPSC-derived osteoblasts recapitulate osteosarcoma features including defective osteoblastic differentiation and tumorigenic ability, suggesting that our established LFS disease model is a “disease in a dish” platform for elucidating p53 mutation mediated disease pathogenesis. Since these iPSCs were generated from non-transformed fibroblasts, any recapitulated features of osteosarcoma must be due to the single gene alteration. The patient-specific iPSC model therefore provides a powerful system to elucidate unique gene function in tumor etiology. We continue applying patient-specific iPSCs and TALEN/CRISPR genetically engineered hESCs to illuminate cancer pathological mechanisms.

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Stem Cell Lab

Current Research projects

(1) Systems-level analyses and characterization of mutant p53 in LFS-associated cancers. We apply LFS iPSCs as well as TALENs and CRISPR/Cas9 genome editing tools to create p53 mutations in pluripotent stem cells (PSCs; e.g., iPSCs and ESCs). These engineered p53-mutation iPSCs resembling LFS will be differentiated to cancer original cells (e.g., osteoblasts for osteosarcoma,  myogenic progenitors for rhabdomyosarcoma, astrocytes for astrocytoma, and hepatocytes for liver cancer) and their genome-wide alterations examined by transcriptome, miRNA, interactome, and ChIP-seq approaches. Integrating these data provide insights into the tumor suppressor role of p53 in the development of multiple cancers and elucidate the universal pathological signaling induced by distinct p53 mutations.

(2) Model familial cancer syndrome with predisposition to cancers by patient-specific iPSC approaches. To explore the common features across multiple genetic cancer driver mutations, we establish multiple cancer-prone disease models to explore the central pathological mechanisms triggering cancer development. For instance, we currently model genetic diseases with predisposition to cancers including hereditary retinoblastoma (RB), Rothmund-Thomson syndrome (RTS), and Diamond-Blackfan anemia.

(3) To facilitate the future applications of iPSCs/hESCs for cancer research, tissue regeneration, and other clinical applications, we apply lineage-specific fluoresce reporters and artificial intelligent (AI) technology to develop and refine iPSC/hESC-derived 2D and 3D lineage differentiation methodologies. 

(4) To understand the fundamental of bone biology, we also apply systems analysis, next-generation sequencing technology, and mouse genetic models to understand osteoblast-specific gene regulation and how outside signaling impacts osteoblastic differentiation.

Elucidate Bone Formation and Regeneration by PSC Platform and Lineage Differentiation

 

Congenital and acquired bone diseases caused by dysregulation of bone homeostasis constitute a critical public health concern. Bone diseases associated with bone fracture and large bone defects are a common cause of disability, and recovery depends on effective bone regeneration. The last decades of applied research in bone biology have led to improved preventive and therapeutic interventions, including multiple classes of drugs, but illness, disability, and mortality caused by bone diseases have remained persistently high.

 

One of the main reasons is a lack of deep fundamental understandings of cells regulating bone homeostasis. Among them, osteoblasts, bone-forming cells, are the key cell types in positively regulating skeletal bone development and forming mineralized bone matrix. However, limited access to human bone tissue restricts our understanding of human osteoblasts and complicates validation of findings from in vivo rodent model systems. We have established a human pluripotent stem cell (hPSC) culture and differentiation system that allows us to generate functional human osteoblasts for in vitro studies, though the ability to purify and therefore characterize these osteoblasts has been limited by the lack of unique osteoblast surface antigens. Furthermore, it remains unclear how unique osteoblast surface antigens integrate extrinsic and intrinsic signaling to determine osteoblast cell fate and govern osteoblast identity.      

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Current Research projects

(1) Systematically identify unique human osteoblast surface markers, dissect their functions and help define molecular signaling networks used in bone formation and regeneration.

(2) Explore the essential transcription factors and their transcription regulatory networks involved in osteoblast differentiation and maturation.

(3) Apply bionanomaterials and PSC-derived osteoblasts for bone tissue engineering.

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Additional Lab information

Dr. Dung-Fang Lee (UTHealth website)

https://med.uth.edu/ibp/faculty/dung-fang-lee-phd/

Dr. Ruiying Zhao (UTHealth website)

https://med.uth.edu/ibp/faculty/ruiying-zhao-md-phd/

Modeling Cancer with Stem Cells

https://www.youtube.com/watch?v=88cl5Fpg6OI

JOVE Videos

https://www.jove.com/author/Dung-Fang_Lee

(1) Modeling Osteosarcoma Using Li-Fraumeni Syndrome Patient-derived Induced Pluripotent Stem Cells https://www.jove.com/t/57664/modeling-osteosarcoma-using-li-fraumeni-syndrome-patient-derived

The Lee and Zhao Labs locate in the McGovern Medical School at the University of Texas Health Science Center at Houston. Our research is made possible by funding from The University of Texas Health Science Center at Houston, National Cancer Institute, Cancer Prevention and Research Institute of Texas, Department of Defense, Rolanette and Berdon Lawrence Bone Disease Program of Texas, and The Pablove Foundation.

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