Generation of iPSCs from cultured human malignant cells

Cell biological profiling of reprogrammed cancer stem cell-like colon cancer cells maintained in culture

Cancer stem cells (CSCs) are specific targets for therapeutic applications, but the rarity of CSCs within tumors makes the isolation of CSCs difficult. To overcome these problems, we generated CSCs in vitro using established reprogramming techniques. We transduced four previously established reprogramming factors, Oct3/4, Sox2, Klf4, and L-myc, into the colon cancer cell lines LoVo and OUMS-23, and investigated the biological characteristics of these lines. Tra-1-60+ cells were obtained from reprogrammed induced pluripotent stem (iPS) cell-like colonies and showed CSC properties, including colony formation, maintenance of colonies by repeated passages, and feeder cell dependency, as well as increased expressions of CSC markers such as CD133 and ALDH1. The CSC-like cells showed increased chemoresistance to 5-fluorouracil and elevated tumorigenicity upon transplantation into kidneys of immune-deficient mice. These tumors shifted to a poorly differentiated stage with many atypical cells, cytoplasmic mucin, and focal papillary components, with demonstrated dedifferentiation. The principal component analysis from DNA microarrays showed that though both cell lines moved to iPS cells after reprogramming, they were not completely identical to iPS cells. Significantly elevated gene expression of Decorin and CD90 was observed in CSC-like cells. Together, these results show that reprogramming of cancer cells produced not pluripotent stem cells but CSC-like cells, and these findings will provide biological information about genuine CSCs and help establish new CSC-targeted therapies.

Modeling Hematological Diseases and Cancer With Patient-Specific Induced Pluripotent Stem Cells

The advent of induced pluripotent stem cells (iPSCs) together with recent advances in genome editing, microphysiological systems, tissue engineering and xenograft models present new opportunities for the investigation of hematological diseases and cancer in a patient-specific context. Here we review the progress in the field and discuss the advantages, limitations, and challenges of iPSC-based malignancy modeling. We will also discuss the use of iPSCs and its derivatives as cellular sources for drug target identification, drug development and evaluation of pharmacological responses.

Identification of protein kinase inhibitors to reprogram breast cancer cells

Direct reversion of cancers into normal-like tissues is an ideal strategy for cancer treatment. Recent reports have showed that defined transcription factors can induce reprogramming of cancer cells into pluripotent stem cells, supporting this notion. Here, we have developed a reprogramming method that uses a conceptually unique strategy for breast cancer cell treatment. We have screened a kinase inhibitor library and found that Rho-associated protein kinase (ROCK) and mammalian target of rapamycin (mTOR) kinase inhibitors can substitute for all transcription factors to be sufficient to reprogram breast cancer cells into progenitor cells. Furthermore, ROCK–mTOR inhibitors could reprogram breast cancer cells to another terminal lineage-adipogenic cells. Genome-wide transcriptional analysis shows that the induced fat-like cells have a profile different from breast cancer cells and similar to that of normal adipocytes. In vitro and in vivo tumorigenesis assays have shown that induced fat-like cells lose proliferation and tumorigenicity. Moreover, reprogramming treatment with ROCK–mTOR inhibitors prevents breast cancer local recurrence in mice. Currently, ROCK–mTOR inhibitors are already used as antitumor drugs in patients, thus, this reprogramming strategy has significant potential to move rapidly toward clinical trials for breast cancer treatment.

Reprogramming glioblastoma multiforme cells into neurons by protein kinase inhibitors

Background

Reprogramming of cancers into normal-like tissues is an innovative strategy for cancer treatment. Recent reports demonstrate that defined factors can reprogram cancer cells into pluripotent stem cells. Glioblastoma multiforme (GBM) is the most common and aggressive malignant brain tumor in humans. Despite multimodal therapy, the outcome for patients with GBM is still poor. Therefore, developing novel therapeutic strategy is a critical requirement.

Methods

We have developed a novel reprogramming method that uses a conceptually unique strategy for GBM treatment. We screened a kinase inhibitor library to find which candidate inhibitors under reprogramming condition can reprogram GBM cells into neurons. The induced neurons are identified whether functional and loss of tumorigenicity.

Results

We have found that mTOR and ROCK kinase inhibitors are sufficient to reprogram GBM cells into neural-like cells and “normal” neurons. The induced neurons expressed neuron-specific proteins, generated action potentials and neurotransmitter receptor-mediated currents. Genome-wide transcriptional analysis showed that the induced neurons had a profile different from GBM cells and were similar to that of control neurons induced by established methods. In vitro and in vivo tumorigenesis assays showed that induced neurons lost their proliferation ability and tumorigenicity. Moreover, reprogramming treatment with ROCK-mTOR inhibitors prevented GBM local recurrence in mice.

Conclusion

This study indicates that ROCK and mTOR inhibitors-based reprogramming treatment prevents GBM local recurrence. Currently ROCK-mTOR inhibitors are used as anti-tumor drugs in patients, so this reprogramming strategy has significant potential to move rapidly toward clinical trials.

Electronic supplementary material

The online version of this article (10.1186/s13046-018-0857-5) contains supplementary material, which is available to authorized users.

Application of induced pluripotency in cancer studies

As soon as induced pluripotent stem cells (iPSCs) reprogramming of somatic cells were developed, the discovery attracted the attention of scientists, offering new perspectives for personalized medicine and providing a powerful platform for drug testing. The technology was almost immediately applied to cancer studies. As presented in this review, direct reprogramming of cancer cells with enforced expression of pluripotency factors have several basic purposes, all of which aim to explain the complex nature of cancer development and progression, therapy-resistance and relapse, and ultimately lead to the development of novel anti-cancer therapies. Here, we briefly present recent advances in reprogramming methodologies as well as commonalities between cell reprogramming and carcinogenesis and discuss recent outcomes from the implementation of induced pluripotency into cancer research.

ADAM8 Is an Antigen of Tyrosine Kinase Inhibitor-Resistant Chronic Myeloid Leukemia Cells Identified by Patient-Derived Induced Pluripotent Stem Cells

Properties of cancer stem cells involved in drug resistance and relapse have significant effects on clinical outcome. Although tyrosine kinase inhibitors (TKIs) have dramatically improved survival of patients with chronic myeloid leukemia (CML), TKIs have not fully cured CML due to TKI-resistant CML stem cells. Moreover, relapse after discontinuation of TKIs has not been predicted in CML patients with the best TKI response. In our study, a model of CML stem cells derived from CML induced pluripotent stem cells identified ADAM8 as an antigen of TKI-resistant CML cells. The inhibition of expression or metalloproteinase activity of ADAM8 restored TKI sensitivity in primary samples. In addition, residual CML cells in patients with optimal TKI response were concentrated in the ADAM8+ population. Our study demonstrates that ADAM8 is a marker of residual CML cells even in patients with optimal TKI response and would be a predictor of relapse and a therapeutic target of TKI-resistant CML cells.

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We established a model of CML stem cells derived from CML-iPSCs

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ADAM8 is identified as an antigen of TKI-resistant CML cells

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The inhibition of ADAM8 restored TKI sensitivity in primary samples

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ADAM8 is a marker of residual CML cells in patients with optimal TKI response

Modeling cancer using patient-derived induced pluripotent stem cells to understand development of childhood malignancies

In vitro modeling of complex diseases is now a possibility with the use of patient-derived induced pluripotent stem (iPS) cells. Their stem cell properties, including self-renewal and their potential to virtually differentiate into any cell type, emphasize their importance as a translational tool for modeling disorders that so far have been limited by the unavailability of primary cell lines, animal models, or inaccessible human materials. Around 100 genes with germline mutations have been described to be responsible for cancer predisposition. Familial cancers are usually diagnosed earlier in life since these patients already carry the first transforming hit. Deriving iPS cells from patients suffering from familial cancers provides a valuable tool for understanding the mechanisms underlying pediatric cancer onset and progression since they require less mutation recurrence than adult cancers to develop. At the same time, some familial mutations are found in sporadic cases and are a valuable prognostic tool. Patient-derived iPS cells from germline malignancies can also create new tools in developing specific drugs with more personalized-therapy strategies.

Induced Pluripotent Stem Cells in Disease Modeling and Gene Identification

Experimental modeling of human inherited disorders provides insight into the cellular and molecular mechanisms involved, and the underlying genetic component influencing, the disease phenotype. The breakthrough development of induced pluripotent stem cell (iPSC) technology represents a quantum leap in experimental modeling of human diseases, providing investigators with a self-renewing and, thus, unlimited source of pluripotent cells for targeted differentiation. In principle, the entire range of cell types found in the human body can be interrogated using an iPSC approach. Therefore, iPSC technology, and the increasingly refined abilities to differentiate iPSCs into disease-relevant target cells, has far-reaching implications for understanding disease pathophysiology, identifying disease-causing genes, and developing more precise therapeutics, including advances in regenerative medicine. In this chapter, we discuss the technological perspectives and recent developments in the application of patient-derived iPSC lines for human disease modeling and disease gene identification.

Induced Pluripotent Stem Cells: Advances in the Quest for Genetic Stability during Reprogramming Process

Evaluation of the extent and nature of induced pluripotent stem cell (iPSC) genetic instability is important for both basic research and future clinical use. As previously demonstrated regarding embryonic stem cells, such DNA aberrations might affect the differentiation capacity of the cells and increase their tumorigenicity. Here, we first focus on the contribution of multiple DNA damage response pathways during cellular reprogramming. We then discuss the origin and mechanisms responsible for the modification of genetic material in iPSCs (pre-existing variations in somatic cells, mutations induced by reprogramming factors, and mutations induced by culture expansion) and deepen the possible functional consequences of genetic variations in these cells. Lastly, we present some recent improvements of iPSC generation methods aimed at obtaining cells with fewer genetic variations.

Brief Report: Human Acute Myeloid Leukemia Reprogramming to Pluripotency Is a Rare Event and Selects for Patient Hematopoietic Cells Devoid of Leukemic Mutations

Induced pluripotent stem cell reprogramming has provided critical insights into disease processes by modeling the genetics and related clinical pathophysiology. Human cancer represents highly diverse genetics, as well as inter- and intra-patient heterogeneity, where cellular model systems capable of capturing this disease complexity would be invaluable. Acute myeloid leukemia (AML) represents one of most heterogeneous cancers and has been divided into genetic subtypes correlated with unique risk stratification over the decades. Here, we report our efforts to induce pluripotency from the heterogeneous population of human patients that represents this disease in the clinic. Using robust optimized reprogramming methods, we demonstrate that reprogramming of AML cells harboring leukemic genomic aberrations is a rare event with the exception of those with de novo mixed-lineage leukemia (MLL) mutations that can be reprogrammed and model drug responses in vitro. Our findings indicate that unlike hematopoietic cells devoid of genomic aberrations, AML cells harboring driver mutations are refractory to reprogramming. Expression of MLL fusion proteins in AML cells did not contribute to induced reprogramming success, which continued to select for patient derived cells devoid of AML patient-specific aberrations. Our study reveals that unanticipated blockades to achieving pluripotency reside within the majority of transformed AML patient cells. Stem Cells 2017;35:2095-2102.

Patient-derived induced pluripotent stem cells in cancer research and precision oncology

Together with recent advances in the processing and culture of human tissue, bioengineering, xenotransplantation and genome editing, Induced pluripotent stem cells (iPSCs) present a range of new opportunities for the study of human cancer. Here we discuss the main advantages and limitations of iPSC modeling, and how the method intersects with other patient-derived models of cancer, such as organoids, organs-on-chips and patient-derived xenografts (PDXs). We highlight the opportunities that iPSC models can provide beyond those offered by existing systems and animal models and present current challenges and crucial areas for future improvements toward wider adoption of this technology.

Induced pluripotent stem cell: A headway in reprogramming with promising approach in regenerative biology

Since the embryonic stem cells have knocked the doorsteps, they have proved themselves in the field of science, research, and medicines, but the hovered restrictions confine their application in human welfare. Alternate approaches used to reprogram the cells to the pluripotent state were not up to par, but the innovation of induced pluripotent stem cells (iPSCs) paved a new hope for the researchers. Soon after the discovery, iPSCs technology is undergoing renaissance day by day, i.e., from the use of genetic material to recombinant proteins and now only chemicals are employed to convert somatic cells to iPSCs. Thus, this technique is moving straightforward and productive at an astonishing pace. Here, we provide a brief introduction to iPSCs, the mechanism and methods for their generation, their prevailing and prospective applications and the future opportunities that can be expected from them.

Next-generation sequencing traces human induced pluripotent stem cell lines clonally generated from heterogeneous cancer tissue

AIM

To investigate genotype variation among induced pluripotent stem cell (iPSC) lines that were clonally generated from heterogeneous colon cancer tissues using next-generation sequencing.

METHODS

Human iPSC lines were clonally established by selecting independent single colonies expanded from heterogeneous primary cells of S-shaped colon cancer tissues by retroviral gene transfer (OCT3/4, SOX2, and KLF4). The ten iPSC lines, their starting cancer tissues, and the matched adjacent non-cancerous tissues were analyzed using next-generation sequencing and bioinformatics analysis using the human reference genome hg19. Non-synonymous single-nucleotide variants (SNVs) (missense, nonsense, and read-through) were identified within the target region of 612 genes related to cancer and the human kinome. All SNVs were annotated using dbSNP135, CCDS, RefSeq, GENCODE, and 1000 Genomes. The SNVs of the iPSC lines were compared with the genotypes of the cancerous and non-cancerous tissues. The putative genotypes were validated using allelic depth and genotype quality. For final confirmation, mutated genotypes were manually curated using the Integrative Genomics Viewer.

RESULTS

In eight of the ten iPSC lines, one or two non-synonymous SNVs in EIF2AK2, TTN, ULK4, TSSK1B, FLT4, STK19, STK31, TRRAP, WNK1, PLK1 or PIK3R5 were identified as novel SNVs and were not identical to the genotypes found in the cancer and non-cancerous tissues. This result suggests that the SNVs were de novo or pre-existing mutations that originated from minor populations, such as multifocal pre-cancer (stem) cells or pre-metastatic cancer cells from multiple, different clonal evolutions, present within the heterogeneous cancer tissue. The genotypes of all ten iPSC lines were different from the mutated ERBB2 and MKNK2 genotypes of the cancer tissues and were identical to those of the non-cancerous tissues and that found in the human reference genome hg19. Furthermore, two of the ten iPSC lines did not have any confirmed mutated genotypes, despite being derived from cancerous tissue. These results suggest that the traceability and preference of the starting single cells being derived from pre-cancer (stem) cells, stroma cells such as cancer-associated fibroblasts, and immune cells that co-existed in the tissues along with the mature cancer cells.

CONCLUSION

The genotypes of iPSC lines derived from heterogeneous cancer tissues can provide information on the type of starting cell that the iPSC line was generated from.

Modeling the process of human tumorigenesis

Modelling the genesis of human cancers is at a scientific turning point. Starting from primary sources of normal human cells, it is now possible to reproducibly generate several types of malignant cell populations. Powerful methods for clonally tracking and manipulating their appearance and progression in serially transplanted immunodeficient mice are also in place. These developments circumvent historic drawbacks inherent in analyses of cancers produced in model organisms, established human malignant cell lines, or highly heterogeneous patient samples. In this review, we survey the advantages, contributions and limitations of current de novo human tumorigenesis strategies and note several exciting prospects on the horizon.

A better understanding of the earliest stages of human cancer formation can enable future improvements in early detection, diagnosis and treatment. In this review, the authors summarize the methods enabling de novo tumorigenesis protocols to be applied to human cells and the insights derived from them to date, as well as the exciting and relevant technical developments anticipated to extend even further the utility of these strategies.

iTRAQ-based quantitative proteomic analysis of Yamanaka factors reprogrammed breast cancer cells

Cancer cells had been developed to be reprogrammed into embryonic stem like cells by induced pluripotent stem cells (iPSCs) technology, however, the tumor differentiation/dedifferentiation mechanisms had not yet been analyzed on a genome-wide scale. Here, we inserted the four stem cell transcription factor genes OCT4, SOX2, C-MYC and KLF4 into MCF cells (MCFs), represented a female breast cancer cell type, and obtained iPSCs (Mcfips) in about 3 weeks. By using the LC MS/MS iTRAQ technology, we analyzed the proteomic changes between MCFs and Mcfips. Of identified 4,616 proteins totally, 247 and 142 differentially expressed (DE) proteins were found in Mcfips compared with human induce pluripotent stem cells (Hips) and MCFs, respectively. 35 co-up and 10 co-down regulated proteins were recognized in DE proteins. Above DE proteins were categorized with GO functional classification annotation and KEGG metabolic pathway analysis into biological processes. In the protein interaction network, we found 37 and 39 hubs interacted with more than one protein in Mcfips comparing to Hips, in addition, 25 and 9 hubs were identified in Mcfips comparing to MCFs. Importantly, the mitochondria, ribosome and tumor suppressor proteins were found to be core regulators of tumor reprogramming, which might contribute to understand the mechanisms in relation to the occurrences and progression of a tumor. Thus, our study provided a valuable data for exploring the possibility to normalize the malignant phenotype.

Cancer cell reprogramming to identify the genes competent for generating liver cancer stem cells

The cancer stem cell (CSC) hypothesis postulates that cancer originates from the malignant transformation of stem/progenitor cells and is considered to apply to many cancers, including liver cancer. Identification that CSCs are responsible for drug resistance, metastasis, and secondary tumor appearance suggests that these populations are novel obligatory targets for the treatment of cancer. Here, we describe our new method for identifying potential CSC candidates. The reprogramming of cancer cells via induced pluripotent stem cell (iPSC) technology is a novel therapy for the treatment and for the study of CSC-related genes. This technology has advantages for studying the interactions between CSC-related genes and the cancer niche microenvironment. This technology may also provide a useful platform for studying the genes involved in the generation of CSCs before and after reprogramming, and for elucidating the mechanisms underlying cancer initiation and progression. The present review summarizes the current understanding of transcription factors involved in the generation of liver CSCs from liver cancer cell-derived iPSCs and how these contribute to oncogenesis, and discusses the modeling of liver cancer development.

Establishment of induced pluripotent stem cells from normal B cells and inducing AID expression in their differentiation into hematopoietic progenitor cells

B cell derived induced pluripotent stem cells (BiPSCs) were recently established from peripheral blood B cells by the simultaneous transfection of Yamanaka factors (Oct3/4, Sox2, Klf4, c-Myc) and C/EBPα using a Sendai virus vector. Here, using a different method, we established BiPSCs with immunoglobulin heavy chain (IgH) gene rearrangement from normal B cells purified from lymph nodes. The critical points of our method are pre-stimulation of B cells with IL-21 and CD40-ligand (CD40L), followed by consecutive transfection of highly concentrated Yamanaka factors using a retroviral vector. Following each transfection the cells were centrifuged onto a retronectin coated plate and the activated by IL-4, IL-2, and CD40L. Furthermore, we established BiPSCs (BiPSC-A) in which activation-induced cytidine deaminase (AID) could be induced using the doxycycline-controlled. Both the parental BiPSC and BiPSC-A showed the capability of differentiating into hematopoietic progenitor cells (HPCs) based on confirmation of CD34 expression and colony-formation from CD34-positive cells. The findings that BiPSC-A can differentiate into HPCs suggest that there is a possibility that induction of AID expression would result in chromosomal translocations in the process of differentiation from BiPSCs, and therefore that these BiPSCs could be useful in elucidating the tumor origin of abnormal B cells in myelomagenesis.

Susceptibility of Human Oral Squamous Cell Carcinoma (OSCC) H103 and H376 cell lines to Retroviral OSKM mediated reprogramming

Although numbers of cancer cell lines have been shown to be successfully reprogrammed into induced pluripotent stem cells (iPSCs), reprogramming Oral Squamous Cell Carcinoma (OSCC) to pluripotency in relation to its cancer cell type and the expression pattern of pluripotent genes under later passage remain unexplored. In our study, we reprogrammed and characterised H103 and H376 oral squamous carcinoma cells using retroviral OSKM mediated method. Reprogrammed cells were characterized for their embryonic stem cells (ESCs) like morphology, pluripotent gene expression via quantitative real-time polymerase chain reaction (RT-qPCR), immunofluorescence staining, embryoid bodies (EB) formation and directed differentiation capacity. Reprogrammed H103 (Rep-H103) exhibited similar ESCs morphologies with flatten cells and clear borders on feeder layer. Reprogrammed H376 (Rep-H376) did not show ESCs morphologies but grow with a disorganized morphology. Critical pluripotency genes Oct4, Sox2 and Nanog were expressed higher in Rep-H103 against the parental counterpart from passage 5 to passage 10. As for Rep-H376, Nanog expression against its parental counterpart showed a significant decrease at passage 5 and although increased in passage 10, the level of expression was similar to the parental cells. Rep-H103 exhibited pluripotent signals (Oct4, Sox2, Nanog and Tra-1-60) and could form EB with the presence of three germ layers markers. Rep-H103 displayed differentiation capacity into adipocytes and osteocytes. The OSCC cell line H103 which was able to be reprogrammed into an iPSC like state showed high expression of Oct4, Sox2 and Nanog at late passage and may provide a potential iPSC model to study multi-stage oncogenesis in OSCC.

Melanoma-Derived iPCCs Show Differential Tumorigenicity and Therapy Response

A point mutation in the BRAF gene, leading to a constitutively active form of the protein, is present in 45%–60% of patients and acts as a key driver in melanoma. Shortly after therapy induction, resistance to MAPK pathway-specific inhibitors develops, indicating that pathway inhibition is circumvented by epigenetic mechanisms. Here, we mimicked epigenetic modifications in melanoma cells by reprogramming them into metastable induced pluripotent cancer cells (iPCCs) with the ability to terminally differentiate into non-tumorigenic lineages. iPCCs and their differentiated progeny were characterized by an increased resistance against targeted therapies, although the cells harbor the same oncogenic mutations and signaling activity as the parental melanoma cells. Furthermore, induction of a pluripotent state allowed the melanoma-derived cells to acquire a non-tumorigenic cell fate, further suggesting that tumorigenicity is influenced by the cell state.

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Human melanoma cells reprogrammed toward an iPSC-like state (iPCCs)

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iPCCs differentiated into neurons and fibroblasts

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iPCC-derived fibroblasts show no tumorigenic potential

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iPCCs and iPCC-derived fibroblasts lose oncogene addiction

Application of Induced Pluripotent Stem Cell Technology to the Study of Hematological Diseases

The burst of reprogramming technology in recent years has revolutionized the field of stem cell biology, offering new opportunities for personalized, regenerative therapies. The direct reprogramming of somatic cells to induced pluripotent stem cells (iPSCs) has provided an invaluable tool to study and model a wide range of human diseases. Here, we review the transforming potential of such a strategy in research and in therapies applicable to the hematology field.

Advances and Challenges on Cancer Cells Reprogramming Using Induced Pluripotent Stem Cells Technologies

Cancer cells transformation into a normal state or into a cancer cell population which is less tumorigenic than the initial one is a challenge that has been discussed during last decades and it is still far to be solved. Due to the highly heterogeneous nature of cancer cells, such transformation involves many genetic and epigenetic factors which are specific for each type of tumor. Different methods of cancer cells reprogramming have been established and can represent a possibility to obtain less tumorigenic or even normal cells. These methods are quite complex, thus a simple and efficient method of reprogramming is still required. As soon as induced pluripotent stem cells (iPSC) technology, which allowed to reprogram terminally differentiated cells into embryonic stem cells (ESC)-like, was developed, the method strongly attracted the attention of researches, opening new perspectives for stem cell (SC) personalized therapies and offering a powerful in vitro model for drug screening. This technology is also used to reprogram cancer cells, thus providing a modern platform to study cancer-related genes and the interaction between these genes and the cell environment before and after reprogramming, in order to elucidate the mechanisms of cancer initiation and progression. The present review summarizes recent advances on cancer cells reprogramming using iPSC technology and shows the progress achieved in such field.

A human haploid gene trap collection to study lncRNAs with unusual RNA biology

Many thousand long non-coding (lnc) RNAs are mapped in the human genome. Time consuming studies using reverse genetic approaches by post-transcriptional knock-down or genetic modification of the locus demonstrated diverse biological functions for a few of these transcripts. The Human Gene Trap Mutant Collection in haploid KBM7 cells is a ready-to-use tool for studying protein-coding gene function. As lncRNAs show remarkable differences in RNA biology compared to protein-coding genes, it is unclear if this gene trap collection is useful for functional analysis of lncRNAs. Here we use the uncharacterized LOC100288798 lncRNA as a model to answer this question. Using public RNA-seq data we show that LOC100288798 is ubiquitously expressed, but inefficiently spliced. The minor spliced LOC100288798 isoforms are exported to the cytoplasm, whereas the major unspliced isoform is nuclear localized. This shows that LOC100288798 RNA biology differs markedly from typical mRNAs. De novo assembly from RNA-seq data suggests that LOC100288798 extends 289kb beyond its annotated 3' end and overlaps the downstream SLC38A4 gene. Three cell lines with independent gene trap insertions in LOC100288798 were available from the KBM7 gene trap collection. RT-qPCR and RNA-seq confirmed successful lncRNA truncation and its extended length. Expression analysis from RNA-seq data shows significant deregulation of 41 protein-coding genes upon LOC100288798 truncation. Our data shows that gene trap collections in human haploid cell lines are useful tools to study lncRNAs, and identifies the previously uncharacterized LOC100288798 as a potential gene regulator.

In vitro models of cancer stem cells and clinical applications

Cancer cells, stem cells and cancer stem cells have for a long time played a significant role in the biomedical sciences. Though cancer therapy is more effective than it was a few years ago, the truth is that still none of the current non-surgical treatments can cure cancer effectively. The reason could be due to the subpopulation called “cancer stem cells” (CSCs), being defined as those cells within a tumour that have properties of stem cells: self-renewal and the ability for differentiation into multiple cell types that occur in tumours.

The phenomenon of CSCs is based on their resistance to many of the current cancer therapies, which results in tumour relapse. Although further investigation regarding CSCs is still needed, there is already evidence that these cells may play an important role in the prognosis of cancer, progression and therapeutic strategy. Therefore, long-term patient survival may depend on the elimination of CSCs. Consequently, isolation of pure CSC populations or reprogramming of cancer cells into CSCs, from cancer cell lines or primary tumours, would be a useful tool to gain an in-depth knowledge about heterogeneity and plasticity of CSC phenotypes and therefore carcinogenesis. Herein, we will discuss current CSC models, methods used to characterize CSCs, candidate markers, characteristic signalling pathways and clinical applications of CSCs. Some examples of CSC-specific treatments that are currently in early clinical phases will also be presented in this review.

Development Refractoriness of MLL-Rearranged Human B Cell Acute Leukemias to Reprogramming into Pluripotency

Induced pluripotent stem cells (iPSCs) are a powerful tool for disease modeling. They are routinely generated from healthy donors and patients from multiple cell types at different developmental stages. However, reprogramming leukemias is an extremely inefficient process. Few studies generated iPSCs from primary chronic myeloid leukemias, but iPSC generation from acute myeloid or lymphoid leukemias (ALL) has not been achieved. We attempted to generate iPSCs from different subtypes of B-ALL to address the developmental impact of leukemic fusion genes. OKSM(L)-expressing mono/polycistronic-, retroviral/lentiviral/episomal-, and Sendai virus vector-based reprogramming strategies failed to render iPSCs in vitro and in vivo. Addition of transcriptomic-epigenetic reprogramming “boosters” also failed to generate iPSCs from B cell blasts and B-ALL lines, and when iPSCs emerged they lacked leukemic fusion genes, demonstrating non-leukemic myeloid origin. Conversely, MLL-AF4-overexpressing hematopoietic stem cells/B progenitors were successfully reprogrammed, indicating that B cell origin and leukemic fusion gene were not reprogramming barriers. Global transcriptome/DNA methylome profiling suggested a developmental/differentiation refractoriness of MLL-rearranged B-ALL to reprogramming into pluripotency.

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Neither primary B-ALL blasts nor leukemic B cell lines can be reprogrammed to iPSCs

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Global transcriptome and DNA methylome suggest a developmental refractoriness

Differentiation and transdifferentiation potentials of cancer stem cells

Tumor cells actively contribute to constructing their own microenvironment during tumorigenesis and tumor progression. The tumor microenvironment contains multiple types of stromal cells that work together with the extracellular matrix and local and systemic factors to coordinately contribute to tumor initiation and progression. Tumor cells and their stromal compartments acquire many genetic and/or epigenetic alternations to facilitate tumor growth and metastasis. The cancer stem cell (CSC) concept has been widely applied to interpreting tumor initiation, growth, metastasis, dormancy and relapse. CSCs have differentiation abilities to generate the original lineage cells that are similar to their normal stem cell counterparts. Interestingly, recent evidence demonstrates that CSCs also have the potential to transdifferentiate into vascular endothelial cells and pericytes, indicating that CSCs can transdifferentiate into other lineage cells for promoting tumor growth and metastasis in some tissue contexts instead of only recruiting stromal cells from local or distant tissues. Although the transdifferentiation of CSCs into tumor stromal cells provides a new dimension that explains tumor heterogeneity, many aspects of CSC transdifferentiation remain elusive. In this review, we summarize the multi-lineage differentiation and transdifferentiation potentials of CSCs as well as discuss their potential contributions to tumor heterogeneity and tumor microenvironment in tumor progression.

Linking Pluripotency Reprogramming and Cancer

Tumor development and the generation of induced pluripotent stem cells are highly comparable processes with striking similarities. Cellular plasticity is inherent to tumor evolution, rendering cells that acquire a stem cell-like phenotype, for which Sox2 activation has proved instrumental for the plastic acquisition of stemness properties in tumor cells. Understanding the molecular mechanisms underlying both events might uncover novel approaches for the development of anticancer therapeutics and constitute model systems for understanding tumor generation and ensuring the biosafety of cell-based therapies. Stem Cells Translational Medicine 2017;6:335-339.

Modeling of Chronic Myeloid Leukemia: An Overview of In Vivo Murine and Human Xenograft Models

Over the past years, a wide variety of in vivo mouse models have been generated in order to unravel the molecular pathology of Chronic Myeloid Leukemia (CML) and to develop and improve therapeutic approaches. These models range from (conditional) transgenic models, knock-in models, and murine bone marrow retroviral transduction models followed by transplantation. With the advancement of immunodeficient xenograft models, it has become possible to use human stem/progenitor cells for in vivo studies as well as cells directly derived from CML patients. These models not only mimic CML but also have been instrumental in uncovering various fundamental mechanisms of CML disease progression and tyrosine kinase inhibitor (TKI) resistance. With the availability of iPSC technology, it has become feasible to derive, maintain, and expand CML subclones that are at least genetically identical to those in patients. The following review provides an overview of all murine as well as human xenograft models for CML established till date.

Parallel reverse genetic screening in mutant human cells using transcriptomics

Reverse genetic screens have driven gene annotation and target discovery in model organisms. However, many disease‐relevant genotypes and phenotypes cannot be studied in lower organisms. It is therefore essential to overcome technical hurdles associated with large‐scale reverse genetics in human cells. Here, we establish a reverse genetic approach based on highly robust and sensitive multiplexed RNA sequencing of mutant human cells. We conduct 10 parallel screens using a collection of engineered haploid isogenic cell lines with knockouts covering tyrosine kinases and identify known and unexpected effects on signaling pathways. Our study provides proof of concept for a scalable approach to link genotype to phenotype in human cells, which has broad applications. In particular, it clears the way for systematic phenotyping of still poorly characterized human genes and for systematic study of uncharacterized genomic features associated with human disease.

Tumorigenic potential is restored during differentiation in fusion-reprogrammed cancer cells

Detailed understanding of the mechanistic steps underlying tumor initiation and malignant progression is critical for insights of potentially novel therapeutic modalities. Cellular reprogramming is an approach of particular interest because it can provide a means to reset the differentiation state of the cancer cells and to revert these cells to a state of non-malignancy. Here, we investigated the relationship between cellular differentiation and malignant progression by the fusion of four independent mouse cancer cell lines from different tissues, each with differing developmental potentials, to pluripotent mouse embryonic stem (ES) cells. Fusion was accompanied by loss of differentiated properties of the four parental cancer cell lines and concomitant emergence of pluripotency, demonstrating the feasibility to reprogram the malignant and differentiative properties of cancer cells. However, the original malignant and differentiative phenotypes re-emerge upon withdrawal of the fused cells from the embryonic environment in which they were maintained. cDNA array analysis of the malignant hepatoma progression implicated a role for Foxa1, and silencing Foxa1 prevented the re-emergence of malignant and differentiation-associated gene expression. Our findings support the hypothesis that tumor progression results from deregulation of stem cells, and our approach provides a strategy to analyze possible mechanisms in the cancer initiation.

Induction of artificial cancer stem cells from tongue cancer cells by defined reprogramming factors

Background

The cancer stem cells (CSCs), a small subpopulation of cells in tumor are responsible for the tumor initiation, growth, recurrence and metastasis of cancer, as well as resistance of cancers to drugs or radiotherapy. CSCs are an important target for the development of novel strategies in cancer treatment. However, CSCs-targeted new anti-cancer drug discovery is currently hindered by the lack of easy and reliable methods for isolating, collecting and maintaining sufficient number of CSCs. Here, we examined whether introduction of defined reprogramming factors (Oct4, shp53, Sox2, Klf4, l-Myc and Lin28) into HSC2 tongue cancer cells could transform the HSC2 into HSC2 with CSCs properties.

Methods

We introduced the defined reprogramming factors into HSC2 tongue cancer cells via episomal vectors by electroporation method to generate transfectant cells. We investigated the malignant properties of the transfectant cells by cell proliferation assay, migration assay, wound healing assay, sphere formation assay, chemosensitivity and radiosensitivity assay in vitro; and also examined the tumorigenic potential of the transfectants in vivo.

Results

The transfectant cells (HSC2/hOCT3/4-shp53-F, HSC2/hSK, HSC2/hUL, HSC2/hOCT3/4-shp53-F + hSK, HSC2/hOCT3/4-shp53-F + hUL, HSC2/hSK + hUL, HSC2/hOCT3/4-shp53-F + hSK + hUL) displayed a malignant phenotype in culture and form tumors on the back of nude mice more efficiently than parental HSC2 and control HSC2/EGFP transfectant cells. They exhibited increased resistance to chemotherapeutic agents; 5-fluorouracil, cisplatin, docetaxel, trifluorothymidine, zoledronic acid, cetuximab, bortezomib and radiation when compared with HSC2 and HSC2/EGFP. Among all the transfected cells, HSC2/hOCT3/4-shp53-F + hSK + hUL cell containing all of the reprogramming factors showed the most aggressive and malignant properties and presented the highest number of spheres in the culture medium containing human recombinant fibroblast Growth Factor-2 (FGF-2) and epidermal Growth Factor (EGF).

Conclusion

These findings suggest that artificial cancer stem cells obtained by the induction of cellular reprogramming may be useful for investigating the acquisition of potential malignancy as well as screening the CSCs-targeting drugs.

Mesenchymal to Epithelial Transition Induced by Reprogramming Factors Attenuates the Malignancy of Cancer Cells

Epithelial to mesenchymal transition (EMT) is a biological process of metastatic cancer. However, an effective anticancer therapy that directly targets the EMT program has not yet been discovered. Recent studies have indicated that mesenchymal to epithelial transition (MET), the reverse phenomenon of EMT, is observed in fibroblasts during the generation of induced pluripotent stem cells. In the present study, we investigated the effects of reprogramming factors (RFs) on squamous cell carcinoma (SCC) cells. RFs-introduced cancer cells (RICs) demonstrated the enhanced epithelial characteristics in morphology with altered expression of mRNA and microRNAs. The motility and invasive activities of RICs in vitro were significantly reduced. Furthermore, xenografts of RICs exhibited no lymph node metastasis, whereas metastasis was detected in parental SCC-inoculated mice. Thus, we concluded that RICs regained epithelial properties through MET and showed reduced cancer malignancy in vitro and in vivo. Therefore, the understanding of the MET process in cancer cells by introduction of RFs may lead to the designing of a novel anticancer strategy.

Effect of tyrosine kinase inhibitors on stemness in normal and chronic myeloid leukemia cells

Although tyrosine kinase inhibitors (TKIs) efficiently cure chronic myeloid leukemia (CML), they can fail to eradicate CML stem cells (CML-SCs). The mechanisms responsible for CML-SC survival need to be understood for designing therapies. Several previous studies suggest that TKIs could modulate CML-SC quiescence. Unfortunately, CML-SCs are insufficiently available. Induced pluripotent stem cells (iPSCs) offer a promising alternative. In this work, we used iPSCs derived from CML patients (Ph+). Ph+ iPSC clones expressed lower levels of stemness markers than normal iPSCs. BCR-ABL1 was found to be involved in stemness regulation and ERK1/2 to have a key role in the signaling pathway. TKIs unexpectedly promoted stemness marker expression in Ph+ iPSC clones. Imatinib also retained quiescence and induced stemness gene expression in CML-SCs. Our results suggest that TKIs might have a role in residual disease and confirm the need for a targeted therapy different from TKIs that could overcome the stemness-promoting effect caused by TKIs. Interestingly, a similar pro-stemness effect was observed in normal iPSCs and hematopoietic SCs. These findings could help to explain CML resistance mechanisms and the teratogenic side-effects of TKIs in embryonic cells.

Drug Delivery Using Nanoparticles for Cancer Stem-Like Cell Targeting

The theory of cancer stem-like cell (or cancer stem cell, CSC) has been established to explain how tumor heterogeneity arises and contributes to tumor progression in diverse cancer types. CSCs are believed to drive tumor growth and elicit resistance to conventional therapeutics. Therefore, CSCs are becoming novel target in both medical researches and clinical studies. Emerging evidences showed that nanoparticles effectively inhibit many types of CSCs by targeting various specific markers (aldehyde dehydrogenases, CD44, CD90, and CD133) and signaling pathways (Notch, Hedgehog, and TGF-β), which are critically involved in CSC function and maintenance. In this review, we briefly summarize the current status of CSC research and review a number of state-of-the-art nanomedicine approaches targeting CSC. In addition, we discuss emerging therapeutic strategies using epigenetic drugs to eliminate CSCs and inhibit cancer cell reprogramming.

Identification of Genes That Modulate Susceptibility to Formaldehyde and Imatinib by Functional Genomic Screening in Human Haploid KBM7 Cells

Though current functional genomic screening systems are useful for investigating human susceptibility to chemical toxicity, they have limitations. Well-established, high-throughput yeast mutant screens identify only evolutionarily conserved processes. RNA interference can be applied in human cells but is limited by incomplete gene knockout and off-target effects. Human haploid cell screening is advantageous as it requires knockdown of only a single copy of each gene. A human haploid cell mutant library (KBM7-Mu), derived from a chronic myeloid leukemia (CML) patient, was recently developed and has been used to identify genes that modulate sensitivity to infectious agents and pharmaceutical drugs. Here, we sought to improve the KBM7-Mu screening process to enable efficient screening of environmental chemicals. We developed a semi-solid medium based screening approach that cultures individual mutant colonies from chemically resistant cells, faster (by 2-3 weeks) and with less labor than the original liquid medium-based approach. As proof of principle, we identified genetic mutants that confer resistance to the carcinogen formaldehyde (FA, 12 genes, 18 hits) and the CML chemotherapeutic agent imatinib (6 genes, 13 hits). Validation experiments conducted on KBM7 mutants lacking each of the 18 genes confirmed resistance of 6 FA mutants (CTC1, FCRLA, GOT1, LPR5, M1AP, and MAP2K5) and 1 imatinib-resistant mutant (LYRM9). Despite the improvements to the method, it remains technically challenging to limit false positive findings. Nonetheless, our findings demonstrate the broad applicability of this optimized haploid approach to screen toxic chemicals to identify novel susceptibility genes and gain insight into potential mechanisms of toxicity.

Functional Genomic Strategies for Elucidating Human-Virus Interactions: Will CRISPR Knockout RNAi and Haploid Cells?

Over the last several years a wealth of transformative human–virus interaction discoveries have been produced using loss-of-function functional genomics. These insights have greatly expanded our understanding of how human pathogenic viruses exploit our cells to replicate. Two technologies have been at the forefront of this genetic revolution, RNA interference (RNAi) and random retroviral insertional mutagenesis using haploid cell lines (haploid cell screening), with the former technology largely predominating. Now the cutting edge gene editing of the CRISPR/Cas9 system has also been harnessed for large-scale functional genomics and is poised to possibly displace these earlier methods. Here we compare and contrast these three screening approaches for elucidating host–virus interactions, outline their key strengths and weaknesses including a comparison of an arrayed multiple orthologous RNAi reagent screen to a pooled CRISPR/Cas9 human rhinovirus 14–human cell interaction screen, and recount some notable insights made possible by each. We conclude with a brief perspective on what might lie ahead for the fast evolving field of human–virus functional genomics.

Echoes of the embryo: using the developmental biology toolkit to study cancer

The hallmark of embryonic development is regulation - the tendency for cells to find their way into organized and 'well behaved' structures - whereas cancer is characterized by dysregulation and disorder. At face value, cancer biology and developmental biology would thus seem to have little to do with each other. But if one looks beneath the surface, embryos and cancers share a number of cellular and molecular features. Embryos arise from a single cell and undergo rapid growth involving cell migration and cell-cell interactions: features that are also seen in the context of cancer. Consequently, many of the experimental tools that have been used to study embryogenesis for over a century are well-suited to studying cancer. This article will review the similarities between embryogenesis and cancer progression and discuss how some of the concepts and techniques used to understand embryos are now being adapted to provide insight into tumorigenesis, from the origins of cancer cells to metastasis.

An Overview of Direct Somatic Reprogramming: The Ins and Outs of iPSCs

Stem cells are classified into embryonic stem cells and adult stem cells. An evolving alternative to conventional stem cell therapies is induced pluripotent stem cells (iPSCs), which have a multi-lineage potential comparable to conventionally acquired embryonic stem cells with the additional benefits of being less immunoreactive and avoiding many of the ethical concerns raised with the use of embryonic material. The ability to generate iPSCs from somatic cells provides tremendous promise for regenerative medicine. The breakthrough of iPSCs has raised the possibility that patient-specific iPSCs can provide autologous cells for cell therapy without the concern for immune rejection. iPSCs are also relevant tools for modeling human diseases and drugs screening. However, there are still several hurdles to overcome before iPSCs can be used for translational purposes. Here, we review the recent advances in somatic reprogramming and the challenges that must be overcome to move this strategy closer to clinical application.

Human embryonic stem cells prevent T-cell activation by suppressing dendritic cells function via TGF-beta signaling pathway

Human embryonic stem cells (hESCs) represent a potential source of transplantable cells for regenerative medicine, but development of teratoma even in syngenic recipients represents a critical obstacle to safe stem cell-based therapies. We hypothesized that hESCs escape the immune surveillance by regulating the environmental immune system. Using cocultures of hESCs with allogenic peripheral blood mononuclear cells, we demonstrated that hESCs prevent proliferation and activation of human CD4+ T lymphocytes, an effect dependent upon monocytes. Altered expression of key signaling molecules responsible for the crosstalk of monocytes with T cells was detected in the presence of hESCs. Analyzing the mechanism of action, we demonstrated that hESCs were able to downregulate intracellular glutathione levels in both monocytes and CD4+ cells by suppressing glutamate cysteine ligase expression and to alter MHCII and CD80 expression in monocytes. These effects were achieved at least partially via TGF-beta signaling, and both monocyte phenotype and GCLC expression were affected by Caspase-3 proteolytic activity. Altogether, our results demonstrate a novel immune-suppressive mechanism used by hESCs.

Functional genomics to uncover drug mechanism of action

The upswing in US Food and Drug Administration and European Medicines Agency drug approvals in 2014 may have marked an end to the dry spell that has troubled the pharmaceutical industry over the past decade. Regardless, the attrition rate of drugs in late clinical phases remains high, and a lack of target validation has been highlighted as an explanation. This has led to a resurgence in appreciation of phenotypic drug screens, as these may be more likely to yield compounds with relevant modes of action. However, cell-based screening approaches do not directly reveal cellular targets, and hence target deconvolution and a detailed understanding of drug action are needed for efficient lead optimization and biomarker development. Here, recently developed functional genomics technologies that address this need are reviewed. The approaches pioneered in model organisms, particularly in yeast, and more recently adapted to mammalian systems are discussed. Finally, areas of particular interest and directions for future tool development are highlighted.

Differentiation of human neuroblastoma cells toward the osteogenic lineage by mTOR inhibitor

Current hypothesis suggest that tumors can originate from adult cells after a process of 'reprogramming' driven by genetic and epigenetic alterations. These cancer cells, called cancer stem cells (CSCs), are responsible for the tumor growth and metastases. To date, the research effort has been directed to the identification, isolation and manipulation of this cell population. Independently of whether tumors were triggered by a reprogramming of gene expression or seeded by stem cells, their energetic metabolism is altered compared with a normal cell, resulting in a high aerobic glycolytic 'Warburg' phenotype and dysregulation of mitochondrial activity. This metabolic alteration is intricately linked to cancer progression.The aim of this work has been to demonstrate the possibility of differentiating a neoplastic cell toward different germ layer lineages, by evaluating the morphological, metabolic and functional changes occurring in this process. The cellular differentiation reported in this study brings to different conclusions from those present in the current literature. We demonstrate that 'in vitro' neuroblastoma cancer cells (chosen as experimental model) are able to differentiate directly into osteoblastic (by rapamycin, an mTOR inhibitor) and hepatic lineage without an intermediate 'stem' cell step. This process seems owing to a synergy among few master molecules, metabolic changes and scaffold presence acting in a concerted way to control the cell fate.

Crosstalk between stem cell and cell cycle machineries

Pluripotent stem cells, defined by an unlimited self-renewal capacity and an undifferentiated state, are best typified by embryonic stem cells. These cells have a unique cell cycle compared to somatic cells as defined by a rapid progression through the cell cycle and a minimal time spent in G1. Recent reports indicate that pluripotency and cell cycle regulation are mechanistically linked. In this review, we discuss the reciprocal co-regulation of these processes, how this co-regulation may prevent differentiation, and how cellular reprogramming can re-establish the unique cell cycle regulation in induced pluripotent stem cells.

Discovery of survival factor for primitive chronic myeloid leukemia cells using induced pluripotent stem cells

A definitive cure for chronic myeloid leukemia (CML) requires identifying novel therapeutic targets to eradicate leukemia stem cells (LSCs). However, the rarity of LSCs within the primitive hematopoietic cell compartment remains a major limiting factor for their study in humans. Here we show that primitive hematopoietic cells with typical LSC features, including adhesion defect, increased long-term survival and proliferation, and innate resistance to tyrosine kinase inhibitor (TKI) imatinib, can be generated de novo from reprogrammed primary CML cells. Using CML iPSC-derived primitive leukemia cells, we discovered olfactomedin 4 (OLFM4) as a novel factor that contributes to survival and growth of somatic lin(-)CD34(+) cells from bone marrow of patients with CML in chronic phase, but not primitive hematopoietic cells from normal bone marrow. Overall, this study shows the feasibility and advantages of using reprogramming technology to develop strategies for targeting primitive leukemia cells.

Induced pluripotent stem cell technology for dissecting the cancer epigenome

Cancer arises through the accumulation of both genetic and epigenetic alterations. Although the causal role of genetic mutations on cancer development has been established in vivo, similar evidence for epigenetic alterations is limited. Moreover, mutual interactions between genetic mutations and epigenetic alterations remain unclear. Cellular reprogramming technology can be used to actively modify the epigenome without affecting the underlying genomic sequences. Here we introduce recent studies that have utilized this property for cancer research. We propose that just as it has potential for regenerative medicine and disease modeling, cell reprogramming could also be a powerful tool for dissecting the role of the cancer epigenome in the development and maintenance of cancer cells.

High-Throughput Silencing Using the CRISPR-Cas9 System: A Review of the Benefits and Challenges

The clustered regularly interspaced short palindromic repeats (CRISPR)/Cas system has been seized upon with a fervor enjoyed previously by small interfering RNA (siRNA) and short hairpin RNA (shRNA) technologies and has enormous potential for high-throughput functional genomics studies. The decision to use this approach must be balanced with respect to adoption of existing platforms versus awaiting the development of more "mature" next-generation systems. Here, experience from siRNA and shRNA screening plays an important role, as issues such as targeting efficiency, pooling strategies, and off-target effects with those technologies are already framing debates in the CRISPR field. CRISPR/Cas can be exploited not only to knockout genes but also to up- or down-regulate gene transcription-in some cases in a multiplex fashion. This provides a powerful tool for studying the interaction among multiple signaling cascades in the same genetic background. Furthermore, the documented success of CRISPR/Cas-mediated gene correction (or the corollary, introduction of disease-specific mutations) provides proof of concept for the rapid generation of isogenic cell lines for high-throughput screening. In this review, the advantages and limitations of CRISPR/Cas are discussed and current and future applications are highlighted. It is envisaged that complementarities between CRISPR, siRNA, and shRNA will ensure that all three technologies remain critical to the success of future functional genomics projects.

Compromising the 19S proteasome complex protects cells from reduced flux through the proteasome

Proteasomes are central regulators of protein homeostasis in eukaryotes. Proteasome function is vulnerable to environmental insults, cellular protein imbalance and targeted pharmaceuticals. Yet, mechanisms that cells deploy to counteract inhibition of this central regulator are little understood. To find such mechanisms, we reduced flux through the proteasome to the point of toxicity with specific inhibitors and performed genome-wide screens for mutations that allowed cells to survive. Counter to expectation, reducing expression of individual subunits of the proteasome's 19S regulatory complex increased survival. Strong 19S reduction was cytotoxic but modest reduction protected cells from inhibitors. Protection was accompanied by an increased ratio of 20S to 26S proteasomes, preservation of protein degradation capacity and reduced proteotoxic stress. While compromise of 19S function can have a fitness cost under basal conditions, it provided a powerful survival advantage when proteasome function was impaired. This means of rebalancing proteostasis is conserved from yeast to humans.

Susceptibility of pancreatic cancer stem cells to reprogramming

Previous reports have indicated that reprogramming technologies may be useful for altering the malignant phenotype of cancer cells. Although somatic stem cells in normal tissues are more sensitive to reprogramming induction than differentiated cells, it remains to be elucidated whether any specific subpopulations are sensitive to reprogramming in heterogeneous tumor tissues. Here we examined the susceptibility of pancreatic cancer stem cells (CSC) and non-CSC to reprogramming. To characterize CSC populations, we focused on c-Met signaling, which has been identified as a marker of CSC in mouse experiments in vivo. Cells that expressed high levels of c-Met showed higher CSC properties, such as tumor-initiating capacity, and resistance to gemcitabine. Real-time reverse transcription-polymerase chain reaction in cells expressing high levels of c-Met revealed endogenous expression of reprogramming factors, such as OCT3/4, SOX2, KLF4 and cMYC. Introduction of these four factors resulted in higher alkaline phosphatase staining in cells with high c-Met expression than in controls. Therefore, the study results demonstrate that cellular reprogramming may be useful for extensive epigenetic modification of malignant features of pancreatic CSC.

Sendai virus-mediated expression of reprogramming factors promotes plasticity of human neuroblastoma cells

Neuroblastoma (NB) is the most common extracranial solid tumor that originates from multipotent neural crest cells. NB cell populations that express embryonic stem cell-associated genes have been identified and shown to retain a multipotent phenotype. However, whether somatic reprogramming of NB cells can produce similar stem-cell like populations is unknown. Here, we sought to reprogram NB cell lines using an integration-free Sendai virus vector system. Of four NB cell lines examined, only SH-IN cells formed induced pluripotent stem cell-like colonies (SH-IN 4F colonies) at approximately 6 weeks following transduction. These SH-IN 4F colonies were alkaline phosphatase-positive. Array comparative genomic hybridization analysis indicated identical genomic aberrations in the SH-IN 4F cells as in the parental cells. SH-IN 4F cells had the ability to differentiate into the three embryonic germ layers in vitro, but rather formed NBs in vivo. Furthermore, SH-IN 4F cells exhibited resistance to cisplatin treatment and differentiated into endothelial-like cells expressing CD31 in the presence of vascular endothelial growth factor. These results suggest that SH-IN 4F cells are partially reprogrammed NB cells, and could be a suitable model for investigating the plasticity of aggressive tumors.