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Patient-specific induced pluripotent stem cells (iPSCs) represent a potential source for developing novel drugand cell- therapies. Although increasing numbers of disease-specific iPSCs have been generated, there has been limited progress in iPSC-based drug screening/discovery for liver diseases, and the low gene targeting efficiency in human iPSCs warrants further improvement. Using iPSC lines from patients with alpha-1 antitrypsin (AAT) deficiency, for which there is currently no drug- or gene- therapy available, we established a platform to discover new drug candidates and to correct disease-causing mutation with a high efficiency. A high-throughput format screening assay based on our hepatic differentiation protocol was implemented to facilitate automated quantification of cellular AAT accumulation using a 96-well immunofluorescence reader. To expedite the eventual application of lead compounds to patients, we conducted drug screening utilizing our established library of clinical compounds, the Johns Hopkins Drug Library, with extensive safety profiles. Through a blind large-scale drug screening, five clinical drugs were identified to reduce AAT accumulation in diverse patient iPSC-derived hepatocyte-like cells. In addition, using the recently developed transcription activator-like effector nuclease (TALEN) technology, we achieved high gene targeting efficiency in AAT-deficiency patient iPSCs with 25–33% of the clones demonstrating simultaneous targeting at both diseased alleles. The hepatocyte-like cells derived from the gene-corrected iPSCs were functional without the mutant AAT accumulation. This highly efficient and cost-effective targeting technology will broadly benefit both basic and translational applications. Conclusions: Our results demonstrated the feasibility of effective large-scale drug screening using an iPSC-based disease model and highly robust gene targeting in human iPSCs; both of which are critical for translating the iPSC technology into novel therapies for untreatable diseases.

Amplification of the Notch3 locus has been detected in ovarian high-grade serous carcinoma (HGSC), the most common and malignant type of ovarian cancer. We have previously demonstrated that ovarian cancer cells, which amplified and overexpressed Notch3, were dependent on Notch3 signaling for cellular survival and growth. In this study, we provide new evidence that Notch3 expression is associated with recurrent postchemotherapy HGSCs. Moreover, patients with recurrent HGSCs in effusion with high Notch3 expression had a significantly worse clinical outcome, including reduced overall survival and shortened progression-free survival than did patients with low Notch3 expressing HGSC. Ectopic expression of the Notch3 intracellular domain led to an increase in IC 50 for carboplatin in an ovarian surface epithelial cell line and in a low-grade serous carcinoma cell line that expressed undetectable levels of Notch3. Interestingly, expression of the Notch3 intracellular domain increased expression of several genes associated with embryonic stem cells including Nanog, Oct4, Klf4, Rex1, Rif1, Sall4, and NAC1 as well as an ATP-dependent transporter gene, ABCB1. Knockdown of Notch3 resulted in sensitization to carboplatin in OVCAR3 that expresses abundant Notch3. Taken together , the above findings suggest that Notch3 pathway activation reprograms tumor cells to assume an array of embryonic stem cell markers and participates in development of chemoresistance in HGSC.