SOX2 Maintains the Stemness of Retinoblastoma Stem-like Cells Through Hippo/YAP Signaling Pathway

Background: Cancer stem cells are responsible for tumor initiation and progression in various types of cancer, while, although the existence of retinoblastoma stem cells had been reported, the mechanisms supporting retinoblastoma stemness are poorly understood. In this study, a modified method for isolating retinoblastoma stem-like cells for mechanistic study was first established and an important mechanism underlying SOX2-drived retinoblastoma stemness was subsequently revealed.Methods: The retinoblastoma stem-like cells were isolated by single cell cloning in combination of examination of sphere-forming capacities. The stemness of isolated retinoblastoma stem-like cells were characterized by sphere-forming capacities and the expression of cancer stem cell markers. The SOX2 gene was overexpressed or knocked down by lentivirus system. The transcriptional regulation was identified by qRT-PCR, luciferase reporter, nuclear run-on and DNA pull down assay. Spearman analysis was employed for correlation analysis of genes in tumor tissues of retinoblastoma patients. Results: The isolated retinoblastoma stem-like cells exhibited significantly enhanced sphere-forming capacity and constantly higher levels of CD44, ABCG2, SOX2 and PAX6, but not CD133. SOX2 positively regulated the stemness of retinoblastoma stem-like cells as identified by gene manipulation technology. SOX2 directly binds to the promoters of WWTR1 and YAP1, transcriptionally activates WWTR1 and YAP1, and thereby activating Hippo/YAP signaling. Knockdown of WWTR1 or YAP1 partially abolished the effect of SOX2 on the stemness of retinoblastoma stem-like cells. Conclusion: An effective method for isolation of retinoblastoma stem-like cells was established. The mechanistic study demonstrated that SOX2, as a key deriver, maintains retinoblastoma stemness by activating Hippo/YAP signaling. Inhibition of Hippo/YAP signaling would be an effective strategy for human retinoblastoma caused by aberrant upregulation of SOX2.

Development of an efficient single-cell cloning and expansion strategy for genome edited induced pluripotent stem cells

Disease-specific human induced pluripotent stem cells (hiPSCs) can be generated directly from individuals with known disease characteristics or alternatively be modified using genome editing approaches to introduce disease causing genetic mutations to study the biological response of those mutations. The genome editing procedure in hiPSCs is still inefficient, particularly when it comes to homology directed repair (HDR) of genetic mutations or targeted transgene insertion in the genome and single cell cloning of edited cells. In addition, genome editing processes also involve additional cellular stresses such as trouble with cell viability and genetic stability of hiPSCs. Therefore, efficient workflows are desired to increase genome editing application to hiPSC disease models and therapeutic applications. Apart from genome editing efficiency, hiPSC survival following single-cell cloning has proved to be challenging and has thus restricted the capability to easily isolate homogeneous clones from edited hiPSCs. To this end, we demonstrate an efficient workflow for feeder-free single cell clone generation and expansion in both CRISPR-mediated knock-out (KO) and knock-in (KI) hiPSC lines. Using StemFlex medium and CloneR supplement in conjunction with Matrigel cell culture matrix, we show that cell viability and expansion during single-cell cloning in edited and unedited cells is significantly enhanced. Our reliable single-cell cloning and expansion workflow did not affect the biology of the hiPSCs as the cells retained their growth and morphology, expression of various pluripotency markers and normal karyotype. This simplified and efficient workflow will allow for a new level of sophistication in generating hiPSC-based disease models to promote rapid advancement in basic research and also the development of novel cellular therapeutics.

An epigenetic GPI anchor defect impairs TLR4 signaling in the B cell transdifferentiation model for primary human monocytes BLaER1

Antigen-presenting myeloid cells like monocytes detect invading pathogens via pattern recognition receptors (PRRs) and initiate adaptive and innate immune responses. As analysis of PRR signaling in primary human monocytes is hampered by their restricted expandability, human monocyte models like THP-1 cells are commonly used for loss-of-function studies, such as with CRISPR-Cas9 editing. A recently developed transdifferentiation cell culture system, BLaER1, enables lineage conversion from malignant B cells to monocytes and was found superior to THP-1 in mimicking PRR signaling, thus being the first model allowing TLR4 and inflammasome pathway analysis. Here, we identified an important caveat when investigating TLR4-driven signaling in BLaER1 cells. We show that this model contains glycosylphosphatidylinositol (GPI) anchor-deficient cells, which lack CD14 surface expression when differentiated to monocytes, resulting in diminished LPS/TLR4 but not TLR7/TLR8 responsiveness. This GPI anchor defect is caused by epigenetic silencing of PIGH, leading to a random distribution of intact and PIGH-deficient clones after single-cell cloning. Overexpressing PIGH restored GPI-anchored protein (including CD14) expression and LPS responsiveness. When studying CD14- or other GPI-anchored protein-dependent pathways, researchers should consider this anomaly and ensure equal GPI-anchored protein expression when comparing cells that have undergone single-cell cloning, e. g. after CRISPR-Cas9 editing.

An epigenetic GPI anchor defect impairs TLR4 signaling in the B cell transdifferentiation model for primary human monocytes BLaER1

Antigen-presenting myeloid cells like monocytes detect invading pathogens via pattern recognition receptors (PRRs) and initiate adaptive and innate immune responses. As analysis of PRR signaling in primary human monocytes is hampered by their restricted expandability, human monocyte models like THP-1 cells are commonly used for loss-of-function studies, such as with CRISPR-Cas9 editing. A recently developed transdifferentiation cell culture system, BLaER1, enables lineage conversion from malignant B cells to monocytes and was found superior to THP1 in mimicking PRR signaling, thus being the first model allowing TLR4 and inflammasome pathway analysis. Here, we identified an important caveat when investigating TLR4-driven signaling in BLaER1 cells. We show that this model contains glycosylphosphatidylinositol (GPI) anchor-deficient cells, which lack CD14 surface expression when differentiated to monocytes, resulting in diminished LPS/TLR4 but not TLR7/TLR8 responsiveness. This GPI anchor defect is caused by epigenetic silencing of PIGH, leading to a random distribution of intact and PIGH-deficient clones after single-cell cloning. Overexpressing PIGH or 5-aza-2'-deoxycytidine treatment restored GPI-anchored protein (including CD14) expression and LPS responsiveness. When studying CD14- or other GPI-anchored protein-dependent pathways, researchers should consider this anomaly and ensure equal GPI-anchored protein expression when comparing cells that have undergone single-cell cloning, e. g. after CRISPR-Cas9 editing.

Generation of stably expressing IRF5 spliced isoform in Jurkat cells

Lentiviral transduction enables the generation of gain-of-function of a targeted gene in mammalian cells. Single-cell cloning through limiting dilution can establish a population of cells with homogenous transgene expression for exploring protein function. Here, we describe step by step optimized protocols for generating clonal stably expressing using crude lentiviral supernatant in Jurkat cells. Although the protocol is for general use, we will detail how to create stable cell lines based on Jurkat cells expressing IRF5 spliced isoform. These protocols will be broadly useful for researchers seeking to apply overexpression by viral transduction and generation of stable clone to study gene function in mammalian cells.

Irradiation-Induced Polyploidy Giant Cancer Cells Mediate Tumor Cell Repopulation via Neosis

Background Tumor repopulation generally describes the phenomenon that residual tumor cells surviving therapies tenaciously proliferate and reestablish the tumor, presenting an embarrassing plight for cancer treatment. However, the cellular and molecular mechanisms underlying this process remains poorly understood. In this study, we proposed polyploidy giant cancer cells (PGCCs)-mediated and neosis-based tumor repopulation after radiotherapy.Methods The formation of PGCCs after irradiation was examined in vitro and in vivo. The demise of X-ray irradiated cells was detected by flow cytometry, clonogenic cell survival assay and transmission electron microscopy. Western blot was used to test cell proliferation and death related protein expression level of these irradiated cells. Time lapse microscopy was adopted to observe the destiny of PGCCs. The property of these PGCCs was identified by TUNEL assay, Brdu chasing assay, western blot, immunocytochemical and immunofluorescence staining. The relationship of HMGB1 with PGCCs-derived tumor repopulation was conducted via HMGB1 chemical inhibitors. Finally, animal model was used to verify the formation of PGCCs, and the relevance of HMGB1 in this process was investigated by immunohistochemical staining.Results The majority of PGCCs induced by irradiation move towards cell demise, whereas some of them intriguingly possessed proliferative property. Utilizing time-lapse microscopy and single-cell cloning assay, we observed that neosis derived from those PGCCs with proliferative capacity contributed to tumor cell repopulation after irradiation. Using the conditioned media collected from dying tumor cells to perform single-cell cloning assay, we unexpectedly demonstrated that HMGB1 released from dying tumor cells participated the process of neosis-based tumor repopulation. In irradiation treated animal tumor bearing model, the expression level of HMGB1 increased after irradiation compare with non-irradiated group. Moreover, some PGCCs presented high HMGB1 expression. Interestingly, we also observed that the proliferation potential of PGCCs varied. Some PGCCs proliferated at early stage, while some PGCCs proliferated at late stage.Conclusion X-ray irradiation could induce the formation of PGCCs, which could move towards both cell death and survival; irradiation-generating PGCCs mediated tumor cell repopulation after irradiation via neosis; HMGB1 released from dying cells stimulated the process of neosis and participated in tumor repopulation after irradiation.

A Microfluidic Single-Cell Cloning (SCC) Device for the Generation of Monoclonal Cells

Single-cell cloning (SCC) is a critical step in generating monoclonal cell lines, which are widely used as in vitro models and for producing proteins with high reproducibility for research and the production of therapeutic drugs. In monoclonal cell line generation, the development time can be shortened by validating the monoclonality of the cloned cells. However, the validation process currently requires specialized equipment that is not readily available in general biology laboratories. Here, we report a disposable SCC device, in which single cells can be isolated, validated, and expanded to form monoclonal cell colonies using conventional micropipettes and microscopes. The monoclonal cells can be selectively transferred from the SCC chip to conventional culture plates, using a tissue puncher. Using the device, we demonstrated that monoclonal colonies of actin-GFP (green fluorescent protein) plasmid-transfected A549 cells could be formed in the device within nine days and subsequently transferred to wells in plates for further expansion. This approach offers a cost-effective alternative to the use of specialized equipment for monoclonal cell generation.