Jiyoon Lee

Generation of inner ear organoids containing functional hair cells from human pluripotent stem cells

The derivation of human inner ear tissue from pluripotent stem cells would enable in vitro screening of drug candidates for the treatment of hearing and balance dysfunction and may provide a source of cells for cell-based therapies of the inner ear. Here we report a method for differentiating human pluripotent stem cells to inner ear organoids that harbor functional hair cells. Using a three-dimensional culture system, we modulate TGF, BMP, FGF, and WNT signaling to generate multiple otic-vesicle-like structures from a single stem-cell aggregate. Over 2 months, the vesicles develop into inner ear organoids with sensory epithelia that are innervated by sensory neurons. Additionally, using CRISPR–Cas9, we generate an ATOH1-2A-eGFP cell line to detect hair cell induction and demonstrate that derived hair cells exhibit electrophysiological properties similar to those of native sensory hair cells. Our culture system should facilitate the study of human inner ear development and research on therapies for diseases of the inner ear.

Tissue Transglutaminase Mediated Tumor–Stroma Interaction Promotes Pancreatic Cancer Progression

Purpose: Aggressive pancreatic cancer is commonly associated with a dense desmoplastic stroma, which forms a protective niche for cancer cells. The objective of the study was to determine the functions of tissue transglutaminase (TG2), a Ca2+-dependent enzyme that cross-links proteins through transamidation and is abundantly expressed by pancreatic cancer cells in the pancreatic stroma. Experimental Design: Orthotopic pancreatic xenografts and coculture systems tested the mechanisms by which the enzyme modulates tumor–stroma interactions. Results: We show that TG2 secreted by cancer cells effectively molds the stroma by cross-linking collagen, which, in turn, activates fibroblasts and stimulates their proliferation. The stiff fibrotic stromal reaction conveys mechanical cues to cancer cells, leading to activation of the YAP/TAZ transcription factors, promoting cell proliferation and tumor growth. Stable knockdown of TG2 in pancreatic cancer cells leads to decreased size of pancreatic xenografts. Conclusions: Taken together, our results demonstrate that TG2 secreted in the tumor microenvironment orchestrates the cross-talk between cancer cells and stroma fundamentally affecting tumor growth. Our study supports TG2 inhibition in the pancreatic stroma as a novel strategy to block pancreatic cancer progression. Clin Cancer Res; 21(19); 4482–93. ©2015 AACR.

Abstract POSTER-BIOL-1306: DNA methylation changes during epithelial-to-mesenchymal transition in ovarian cancer cells

Epithelial-to-mesenchymal transition (EMT) is an important step in the process of metastasis and has been linked to cancer cell stemness. We hypothesize that aside from defined genetic changes associated with EMT, epigenetic mechanisms are involved and have not been fully elucidated. We determined DNA methylation in SKOV3 ovarian cancer (OC) cells during EMT induced by TGF-s using the Infinium HumanMethylation450 array. Methylation levels of CpG sites were expressed as s-values ranging from 0 (totally unmethylated) to 1 (totally methylated). Methylation of 468 and 390 sites changed (P Citation Format: Horacio Cardenas, Edyta Vieth, Jiyoon Lee, Yunlong Liu, Kenneth P. Nephew, Daniela Matei. DNA methylation changes during epithelial-to-mesenchymal transition in ovarian cancer cells [abstract]. In: Proceedings of the 10th Biennial Ovarian Cancer Research Symposium; Sep 8-9, 2014; Seattle, WA. Philadelphia (PA): AACR; Clin Cancer Res 2015;21(16 Suppl):Abstract nr POSTER-BIOL-1306.