No abstract

No abstract

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.

Senescence, defined as irreversible cell-cycle arrest, is the main driving force of aging and age-related diseases. Here, we performed high-throughput screening to identify compounds that alleviate senescence and identified the ataxia telangiectasia mutated (ATM) inhibitor KU-60019 as an effective agent. To elucidate the mechanism underlying ATM's role in senescence, we performed a yeast two-hybrid screen and found that ATM interacted with the vacuolar ATPase V subunits ATP6V1E1 and ATP6V1G1. Specifically, ATM decreased E-G dimerization through direct phosphorylation of ATP6V1G1. Attenuation of ATM activity restored the dimerization, thus consequently facilitating assembly of the V and V domains with concomitant reacidification of the lysosome. In turn, this reacidification induced the functional recovery of the lysosome/autophagy system and was coupled with mitochondrial functional recovery and metabolic reprogramming. Together, our data reveal a new mechanism through which senescence is controlled by the lysosomal-mitochondrial axis, whose function is modulated by the fine-tuning of ATM activity.

Human granulocytic anaplasmosis is caused by the obligate intracellular bacterium Anaplasma phagocytophilum. The bacterium avoids host innate defenses in part by infecting, surviving in, and propagating in neutrophils, as well as by inhibiting neutrophil apoptosis. However, the mechanisms of A. phagocytophilum survival in neutrophils and the inhibition of spontaneous apoptosis are not well understood. In this study, we demonstrated that antiapoptotic Mcl-1 protein (Bcl-2 family) expression is maintained and that inhibition of procaspase-3 processing occurs in A. phagocytophilum-infected human neutrophils. An evaluation of p38 mitogen-activated protein kinase (MAPK) showed evidence of increased phosphorylation with infection. Moreover, antagonism of p38 MAPK by the inhibitor SB203580 reversed apoptosis inhibition in live or heat-killed A. phagocytophilum-infected neutrophils. A role for the autocrine or paracrine production of antiapoptotic interleukin 8 (IL-8) expressed with A. phagocytophilum infection was excluded by the use of IL-8-, IL-8R1 (CXCR1)-, and IL-8R2 (CXCR2)-blocking antibodies. As previously demonstrated, the antiapoptotic effect was initially mediated by exposure to A. phagocytophilum components in heat-killed bacteria. However, an important role for active infection is demonstrated by the additional delay in apoptosis with intracellular growth and the refractory abrogation of this response by the p38 MAPK inhibitor 3 to 6 h after neutrophil infection. These results suggest that the initial activation of the p38 MAPK pathway leading to A. phagocytophilum-delayed neutrophil apoptosis is bypassed with active intracellular infection. Moreover, active intracellular infection contributes more to the overall delay in apoptosis than do components of heat-killed A. phagocytophilum alone.

The evolution of chemoresistance is a fundamental characteristic of cancer that ultimately defeats its clinical management. However, it may be possible improve patient outcomes significantly by defeating nodal resistance mechanisms which cancers rely upon during the evolution to an untreatable state.Here we report an essential role for upregulation of the stem cell reprogramming factor PBX1 in mediating chemoresistance in recurrent ovarian carcinomas. In clinical specimens, high levels of PBX1 expression correlated with shorter survival in post-chemotherapy ovarian cancer patients. In tumor cells with low endogenous expression of PBX1, its enforced expression promoted cancer stem cell-like phenotypes, including most notably an increase in resistance to platinum-based therapy used most commonly for management of this disease. Conversely, silencing PBX1 in platinum-resistant cells that overexpressed PBX1 sensitized them to platinum treatment and reduced their stem-likeproperties. An analysis of published genome-wide chromatin immunoprecipitation data indicated that PBX1 binds directly to promoters of genes involved in stem cell maintenance and the response to tissue injury. We confirmed direct regulation of one of these genes, STAT3, demonstrating that the PBX1 binding motif at its promoter acted to positively regulate STAT3 transcription. Pursing this connection, we determined that a STAT3/JAK2 inhibitor could potently sensitize platinum-resistant cells to carboplatin and suppress their growth in vivo. Our findings offer a mechanistic rationale to target the PBX1/STAT3 axis to defeat a key mechanism of chemoresistance in ovarian cancers and possibly other human cancers.3

No abstract