Cancer stem cells as the source of tumor associated myoepithelial cells in the tumor microenvironment developing ductal carcinoma in situ

The heterogeneous cell population in the stromal microenvironment is considered to be attributed to the multiple sources from which the cells originate. Tumor associated myoepithelial cells (TAMEs) are one of the most important populations in the tumor microenvironment (TME) especially in breast cancer. On the other hand, cancer stem cells (CSCs) have previously been described to be the origin of tumor-associated cellular components in the TME. We prepared a cancer stem cell model converting mouse-induced pluripotent stem cells (miPSCs) in the presence of conditioned medium of breast cancer cell line MDA-MB-231 cells. The converted cells developed tumors progressing into invasive carcinoma with ductal carcinoma in situ (DCIS) like structure when transplanted into mouse mammary fat pads. The primary cultured cells from the tumor further exhibited markers of CSC such as Sox2, Oct3/4, - CD133 and EpCAM, and mammary gland-related TAME markers such as α-smooth muscle actin, cytokeratin 8, whey acidic protein, prolactin receptor and progesterone receptor as well. These results indicated that the CSCs could be an origin of TAMEs contributing to mammary gland epithelial cell differentiation and the progression to invasive carcinoma during tumor development. The gene expression profiles confirmed the enhanced signaling pathways of PI3K/AKT and MAPK, which have been demonstrated to be enriched in the CSC models, together with the estrogen receptor signaling which was peculiar to mammary gland-derived character.

GSK-3α/β and MEK inhibitors assist the microenvironment of tumor initiation

Induced pluripotent stem cells (iPSCs) are useful tools for modeling diseases and developing personalized medicine. We have been developing cancer stem cells (CSCs) from iPSCs with conditioned medium (CM) of cancer-derived cells as the mimicry of the microenvironment of tumor initiation. However, the conversion of human iPSCs has not always been efficient with only CM. In this study, human iPSCs reprogrammed from monocytes of healthy volunteers were cultured in a media containing 50% of the CM from human pancreatic cancer derived BxPC3 cells supplemented with a MEK inhibitor (AZD6244) and a GSK-3α/β inhibitor (CHIR99021). The survived cells were assessed for the characteristics of CSCs in vitro and in vivo. As a result, they exhibited CSC phenotypes of self-renewal, differentiation, and malignant tumorigenicity. Primary culture of the malignant tumors of the converted cells exhibited the elevated expression of CSC related genes CD44, CD24 and EPCAM maintaining the expression of stemness genes. In conclusion, the inhibition of GSK-3α/β and MEK and the microenvironment of tumor initiation mimicked by the CM can convert human normal stem cells into CSCs. This study could provide insights into establishing potentially novel personalized cancer models which could help investigate the tumor initiation and screening of personalized therapies on CSCs.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10616-023-00575-1.

Up-regulation of Dsg2 confered stem cells with malignancy through wnt/β-catenin signaling pathway

In the previous study, we originally developed cancer stem cells (CSCs) models from mouse induced pluripotent stem cells (miPSCs) by culturing miPSCs in the conditioned medium of cancer cell lines, which mimiced as carcinoma microenvironment. However, the molecular mechanism of conversion in detail remains to be uncovered. Microarray analysis of the CSCs models in this study revealed Dsg2, one of the members of the desmosomal cadherin family, was up-regulated when compared with the original miPSCs. Moreover, the expression of key factors in Wnt/β-catenin signaling pathway were also found up-regulated in one of the CSCs models, named miPS-LLCcm. An autocrine loop was implied between Dsg2 and Wnt/β-catenin signaling pathway when miPSCs were treated with Wnt/β-catenin signaling pathway activators, Wnt3a and CHIR99021, and when the CSCs model were treated with inhibitors, IWR-1 and IWP-2. Furthermore, the ability of proliferation and self-renewal in the CSCs model was markedly decreased in vitro and in vivo when Dsg2 gene was knocked down by shRNA. Our results showed that the Wnt/β-catenin signaling pathway is activated by the up-regulation of Dsg2 expresssion during the conversion of miPSCs into CSCs implying a potential mechanism of the tranformation of stem cells into malignant phenotype.

Cancer stem cells induced by chronic stimulation with prostaglandin E2 exhibited constitutively activated PI3K axis

Previously, our group has demonstrated establishment of Cancer Stem Cell (CSC) models from stem cells in the presence of conditioned medium of cancer cell lines. In this study, we tried to identify the factors responsible for the induction of CSCs. Since we found the lipid composition could be traced to arachidonic acid cascade in the CSC model, we assessed prostaglandin E2 (PGE2) as a candidate for the ability to induce CSCs from induced pluripotent stem cells (iPSCs). Mouse iPSCs acquired the characteristics of CSCs in the presence of 10 ng/mL of PGE2 after 4 weeks. Since constitutive Akt activation and pik3cg overexpression were found in the resultant CSCs, of which growth was found independent of PGE2, chronic stimulation of the receptors EP-2/4 by PGE2 was supposed to induce CSCs from iPSCs through epigenetic effect. The bioinformatics analysis of the next generation sequence data of the obtained CSCs proposed not only receptor tyrosine kinase activation by growth factors but also extracellular matrix and focal adhesion enhanced PI3K pathway. Collectively, chronic stimulation of stem cells with PGE2 was implied responsible for cancer initiation enhancing PI3K/Akt axis.

Optimization of production and characterization of a recombinant soluble human Cripto-1 protein inhibiting self-renewal of cancer stem cells

Human Cripto-1 is a member of the epidermal growth factor (EGF)-Cripto-FRL-1-Cryptic (CFC) family family and performs critical roles in cancer and various pathological and developmental processes. Recently we demonstrated that a soluble form of Cripto-1 suppresses the self-renewal and enhances the differentiation of cancer stem cells (CSCs). A functional form of soluble Cripto-1 was found to be difficult to obtain because of the 12 cysteine residues in the protein which impairs the folding process. Here, we optimized the protocol for a T7 expression system, purification from inclusion bodies under denatured conditions refolding of a His-tagged Cripto-1 protein. A concentrations of 0.2-0.4 mM isopropyl β-D-1-thiogalactopyranoside (IPTG) at 37°C was found to be the optimal concentration for Cripto-1 expression while imidazole at 0.5 M was the optimum concentration to elute the Cripto-1 protein from a Ni-column in the smallest volume. Cation exchange column chromatography of the Cripto-1 protein in the presence of 8 M urea exhibited sufficient elution profile at pH 5, which was more efficient at recovery. The recovery of the protein reached to more than 26.6% after refolding with arginine. The purified Cripto-1 exhibited high affinity to the anti-ALK-4 antibody and suppressed sphere forming ability of CSCs at high dose and induced cell differentiation.

Diphenyleneiodonium efficiently inhibits the characteristics of a cancer stem cell model derived from induced pluripotent stem cells

Diphenyleneiodonium (DPI) has long been evaluated as an anticancer drug inhibiting NADPH oxidase, the IC₅₀ in several cancer cell lines was reported 10 µM, which is too high for efficacy. In this study, we employed miPS-Huh7cmP cells, which we previously established as a cancer stem cell (CSC) model from induced pluripotent stem cells, to reevaluate the efficacy of DPI because CSCs are currently one of the main foci of therapeutic strategy to treat cancer, but generally considered resistant to chemotherapy. As a result, the conventional assay for the cell growth inhibition by DPI accounted for an IC₅₀ at 712 nM that was not enough to define the effectiveness as an anticancer drug. Simultaneously, the wound-healing assay revealed an IC₅₀ of approximately 500 nM. Comparatively, the IC₅₀ values shown on sphere formation, colony formation, and tube formation assays were 5.52, 12, and 8.7 nM, respectively. However, these inhibitory effects were not observed by VAS2780, also a reputed NADPH oxidase inhibitor. It is noteworthy that these three assays are evaluating the characteristic of CSCs and are designed in the three-dimensional (3D) culture methods. We concluded that DPI could be a suitable candidate to target mitochondrial respiration in CSCs. We propose that the 3D culture assays are more efficient to screen anti-CSC drug candidates and better mimic tumor microenvironment when compared to the adherent monolayer of 2D culture system used for a conventional assay, such as cell growth inhibition and wound-healing assays.

The significance of ErbB2/3 in the conversion of induced pluripotent stem cells into cancer stem cells

Cancer stem cells (CSCs) are suggested to be responsible for drug resistance and aggressive phenotypes of tumors. Mechanisms of CSC induction are still under investigation. Our lab has established a novel method to generate CSCs from iPSCs under a cancerous microenvironment mimicked by the conditioned medium (CM) of cancer-derived cells. Here, we analyzed the transcriptome of CSCs, which were converted from iPSCs with CM from pancreatic ductal adenocarcinoma cells. The differentially expressed genes were identified and used to explore pathway enrichment. From the comparison of the CSCs with iPSCs, genes with elevated expression were related to the ErbB2/3 signaling pathway. Inhibition of either ErbB2 with lapatinib as a tyrosine kinase inhibitor or ErbB3 with TX1-85-1 or siRNAs arrested cell proliferation, inhibited the in vitro tumorigenicity, and lead to loss of stemness in the converting cells. The self-renewal and tube formation abilities of cells were also abolished while CD24 and Oct3/4 levels were reduced, and the MAPK pathway was overactivated. This study shows a potential involvement of the ErbB2/ErbB3 pathway in CSC generation and could lead to new insight into the mechanism of tumorigenesis and the way of cancer prevention.

Different pancreatic cancer microenvironments convert iPSCs into cancer stem cells exhibiting distinct plasticity with altered gene expression of metabolic pathways

BACKGROUND

Cancer stem cells (CSCs) are generated under irregular microenvironment in vivo, of which mimic is quite difficult due to the lack of enough information of the factors responsible for cancer initiation. Here, we demonstrated that mouse induced pluripotent cells (miPSCs) reprogrammed from normal embryonic fibroblasts were susceptible to the microenvironment affected by cancer cells to convert into CSCs in vivo.

METHODS

Three different pancreatic cancer line cells, BxPC3, PANC1, and PK8 cells were mixed with miPSCs and subcutaneously injected into immunodeficient mice. Tumors were evaluated by histological analysis and cells derived from iPSCs were isolated and selected from tumors. The isolated cells were characterized for cancer stem cell characters in vitro and in vivo as well as their responses to anticancer drugs. The impact of co-injection of iPSCs with cancer cells on transcriptome and signaling pathways of iPSCs was investigated.

RESULTS

The injection of miPSCs mixed with human pancreatic cancer cells into immunodeficient mice maintained the stemness of miPSCs and changed their phenotype. The miPSCs acquired CSC characteristics of tumorigenicity and self-renewal. The drug responses and the metastatic ability of CSCs converted from miPSCs varied depending on the microenvironment of cancer cells. Interestingly, transcriptome profiles of these cells indicated that the pathways related with aggressiveness and energy production were upregulated from the levels of miPSCs.

CONCLUSIONS

Our result suggests that cancer-inducing microenvironment in vivo could rewire the cell signaling and metabolic pathways to convert normal stem cells into CSCs.

Functional and Molecular Characters of Cancer Stem Cells Through Development to Establishment

Cancer stem cells (CSCs) are small subpopulation sharing similar properties like normal stem such as self-renewal and differentiation potential to direct tumor growth. Last few years, scientists considered CSCs as the cause of phenotypic heterogeneity in diverse cancer types. Also, CSCs contribute to cancer metastasis and recurrence. The cellular and molecular regulators influence on the CSCs' phenotype changing their behaviors in different stages of cancer progression. CSC markers play significance roles in cancer diagnosis and characterization. We delineate the cross-talks between CSCs and the tumor microenvironment that supports their intrinsic properties including survival, stemness, quiescence and their cellular and molecular adaptation. An insight into the markers of CSCs specific to organs is described.

Cancer Stem Cells Contribute to Drug Resistance in Multiple Different Ways

Many tumors are resistant to conventional cancer therapies because a tumor is composed of heterogeneous cell population. Especially, subpopulation of cancer stem cells, which have self-renewal and differentiation properties and responsible for the tumor initiation, is generally considered resistant to chemo-, radio-, and immune therapy. Understanding the mechanism of drug resistance in cancer stem cells should lead to establish more effective therapeutic strategies. Actually, different molecular mechanisms are conceivable for cancer stem cells acquiring drug resistance. These mechanisms include not only cytoplasmic signaling pathways but also the intercellular communications in the tumor microenvironment. Recently, a great deal of successful reports challenged to elucidate the mechanisms of drug resistance and to develop novel treatments targeting cancer stem cells.

ERBB Signaling Pathway in Cancer Stem Cells

The epidermal growth factor receptor (EGFR) was first tyrosine kinase receptor linked to human cancers. EGFR or ERBB1 is a member of ERBB subfamily, which consists of four type I transmembrane receptor tyrosine kinases, ERBB1, 2, 3 and 4. ERBBs form homo/heterodimers after ligand binding except ERBB2 and consequently becomes activated. Different signal pathways, such as phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT), RAS/RAF/MEK/ERK, phospholipase Cγ and JAK-STAT, are triggered by ERBB activation. Since ERBBs, through these pathways, regulate stemness and differentiation of cancer stem cells (CSCs), their roles in CSC tumorigenicity have extensively been investigated. The hyperactivation of ERBBs and its downstream pathways stimulated by either genetic and/or epigenetic factors are frequently described in many types of human cancers. Their dysregulations make cells acquiring CSC characters such as survival, tumorigenicity and stemness. Because of the roles in tumor growth and progress, ERBBs are considered to be one of the drug targets as cancer treatment strategy. In this chapter, we will summarize the structure, function and roles of ERBB subfamily along with their relative pathways regulating the stemness and tumorigenicity of CSCs. Finally, we will discuss the targeting therapy strategies of cancer along with ERBBs in addition to some challenges and future perspectives.

Trauma-informed Approaches to Substance Use Interventions with Indigenous Peoples: A Scoping Review

Indigenous Peoples experience disproportionately higher rates of problematic substance use. These problems are situated in a context of individual and intergenerational trauma from colonization, residential schools, and racist and discriminatory practices, policies, and services. Therefore, substance use interventions need to adopt a trauma-informed approach. We aimed to synthesize and report the current literature exploring the intersection of trauma and substance use interventions for Indigenous Peoples. Fourteen databases were searched using keywords for Indigenous Peoples, trauma, and substance use. Of the 1373 sources identified, 117 met inclusion criteria. Literature on trauma and substance use with Indigenous Peoples has increased in the last 5 years (2012-2016, n = 29; 2017-2021, n = 48), with most literature coming from the United States and Canada and focusing on historical or intergenerational trauma. Few articles focused on intersectional identities such as 2SLGBTQIA+ (n = 4), and none focused on veterans. There were limited sources (n = 25) that reported specific interventions at the intersection of trauma and substance use. These sources advocate for multi-faceted, trauma-informed, and culturally safe interventions for use with Indigenous Peoples. This scoping review illuminates gaps in the literature and highlights a need for research reporting on trauma-informed interventions for substance use with Indigenous Peoples.

MEK1/2 is a bottleneck that induces cancer stem cells to activate the PI3K/AKT pathway

Cancer stem cells (CSCs) are responsible for cancer initiation, drug resistance, and aggressive tumor phenotypes. Our lab has established a novel method to induce CSCs from induced pluripotent stem (iPS) cells in a microenvironment mimicking chronic inflammation. The converted cells acquired CSC characteristics and developed malignant tumors. Recently, we demonstrated that nonmutagenic chemical inhibitors accelerated the conversion of mouse iPS (miPS) cells into CSCs. Here, we investigated the effects of AZD-6244, a MEK1/2-specific inhibitor, on the conversion of iPS cells into CSCs. The miPS cells were cultured for one week in the presence of the conditioned medium (CM) of Lewis lung carcinoma (LLC) cells and AZD-6244, PD0325901, a pan-MEK inhibitor, or GDC-0879, a B-Raf inhibitor. As a result, AZD-6244 enhanced the conversion of iPS cells into CSCs and upregulated AKT phosphorylation as same as GDC-0879 and PD0325901. The converted cells maintained their self-renewal ability and stemness gene expression. The expression of the CSC markers CD24, CD44 and CD133 was higher in the cells cultured with MAPK inhibitors than in those cultured without MAPK inhibitors. Moreover, converted cells gained migration and invasion abilities assessed by in vitro assays. Therefore, the inhibition of MEK1/2 was found to be critical for the conversion of normal stem cells into CSCs in the tumor-inducing microenvironment.

Chronic exposure to FGF2 converts iPSCs into cancer stem cells with an enhanced integrin/focal adhesion/PI3K/AKT axis

We previously demonstrated the conversion of normal stem cells, including induced pluripotent stem cells (iPSCs), into cancer stem cells (CSCs) without genetic manipulation. Herein, we designed a meta-analysis to assess gene expression profiles in different breast cancer cell lines focusing on the secretory factors responsible for conversion. As a result, fibroblast growth factor 2 (FGF2) was found to be the best candidate in T47D and BT549 cells, of which conditioned medium was previously successful in inducing CSCs. When treated with 3.1 μg/ml FGF2, mouse iPSCs not only maintained survival without LIF for three weeks but also acquired growth ability independent of FGF2. The resultant cells exhibited expression of stemness and cancer stem cell markers, sphere-forming ability, differentiation, and tumorigenicity with malignancy. The primary cultures of the tumor confirmed the signatures of CSCs with two different phenotypes with or without GFP expression under control of the Nanog promoter. Bioinformatic analysis of gene expression profiles suggested constitutive autocrine activation of the FGF receptor, integrins, focal adhesions, and PI3K/AKT pathways. FGF2 could potently initiate cancer as a component of the inflammatory microenvironment.

Correlation between temperature rise and auto-fluorescence: ex vivo study with Er:YAG laser, Quantum Molecular Resonance scalpel and Nd:YAG laser on hard and soft tissues

Surgical techniques of soft and hard oral tissues highly benefited from new technologies such as the Quantic Molecular Resonance (QMR) lancet, the Neodymium-doped Yttrium Aluminum Garnet (Nd:YAG) laser and the Erbium-doped Yttrium Aluminum Garnet (Er:YAG) laser. Increasingly, these technologies replace scalpel, conventional electrosurgery and traditional rotary surgery instruments due to their proven advantages. Features such as reduction of the surgical time, more efficient bleeding control resulting in higher intra-operative visibility and improvement of postoperative course with better Quality of Life score (QoL) are highlighted in numerous studies published in the literature. The thermal rise of tissues during surgical incision, performed with other instruments rather than traditional cold blade scalpels, is not to be ignored by the operator and it must take into consideration first when choosing the surgical instrument and then throughout all the surgical act. Auto-fluorescence (AF) is a property possessed by every cell that exposed to a specific wavelength can absorbance or reflect with peculiar characteristics and its direct examination has been proposed as a non-invasive visual tool for investigation of suspicious changes in oral mucosa. At the limit of our knowledge, few studies have been published in the literature regarding tissue's temperature variations and the interest in Infra-Red temperature detection has been shown in various medicine fields and none of published studies investigated the possible correlation between temperature raise and AF variations. This ex vivo study aims to analyse and compare through the use of a thermal imaging camera and simultaneous detection of AF, the possible correlation between temperature increase and auto-fluorescence.

Metformin suppresses self-renewal and stemness of cancer stem cell models derived from pluripotent stem cells

Metformin exhibits anti-cancer activities in various types of tumours while it is prescribed as the first-line drug for type 2 diabetes. Since new evidence has recently suggested that metformin could target cancer stem cells (CSCs) and prevent their recurrence, repositioning of metformin could be considered as a candidate for anti-CSC agent. In this study, we assessed the effect of metformin on the cancer stem cells developed from induced pluripotent stem cells. As the result, metformin significantly suppressed the self-renewal ability of CSCs when assessed by 3-(4,5-dimethythiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and cell counting methods exhibiting the IC₅₀ as approximately 20 mM, which suppressed tube formation by CSCs on Matrigel reducing the angiogenic potential of CSCs. Cell cycle analysis showed that metformin reduced the percentage of cells in the S phase increasing the percentage of cells in G0/G1 phase. Moreover, the tumorigenicity of CSCs was found to be attenuated when the cells were injected with metformin. From these results, we concluded that metformin could be promising for targeted therapy by repositioning the widely available drugs with safety. SIGNIFICANCE OF THE STUDY: Metformin could target CSCs and prevent their recurrence, repositioning of metformin could be considered as a candidate for the anti-CSC agent. In this paper, we assessed the effect of metformin on the CSCs developed from induced pluripotent stem cells. Here, we show that metformin suppresses the self-renewal and tube formation abilities of CSCs. We also show that metformin reduces the percentage of cells in the S phase increasing the percentage of cells in G0/G1 phase. Moreover, the tumorigenicity of CSCs was found to be attenuated when grafted in vivo after treatment with metformin.

Microenvironment of mammary fat pads affected the characteristics of the tumors derived from the induced cancer stem cells

Breast cancer is the first common cause of cancer-related death in women worldwide. Since the malignancy and aggressiveness of breast cancer have been correlated with the presence of breast cancer stem cells, the establishment of a disease model with cancer stem cells is required for the development of a novel therapeutic strategy. Here, we aimed to evaluate the availability of cancer stem cell models developed from mouse induced pluripotent stem cells with the conditioned medium of different subtypes of breast cancer cell lines, the hormonal-responsive T47D cell line and the triple-negative breast cancer BT549 cell line, to generate in vivo tumor models. When transplanted into the mammary fat pads of BALB/c nude mice, these two model cells formed malignant tumors exhibiting pronounced histopathological characteristics similar to breast cancers. Serial transplantation of the primary cultured cells into mammary fat pads evoked the same features of breast cancer, while this result was perturbed following subcutaneous transplantation. The tumors formed in the mammary fat pads exhibited immune reactivities to prolactin receptor, progesterone receptor, green florescent protein, Ki67, CD44, estrogen receptor α/β and cytokeratin 8, while all of the tumors and their derived primary cells exhibited immunoreactivity to estrogen receptor α/β and cytokeratin 8. Cancer stem cells can be developed from pluripotent stem cells via the secretory factors of cancer-derived cells with the capacity to inherit tissue specificity. However, cancer stem cells should be plastic enough to be affected by the microenvironment of specific tissues. In summary, we successfully established a breast cancer tumor model using mouse induced pluripotent stem cells developed from normal fibroblasts without genetic manipulation.

Cripto-1 as a Potential Target of Cancer Stem Cells for Immunotherapy

Simple Summary

Cancer immunotherapy is gaining attention as a potential fourth treatment following surgery, chemotherapy, and radiation therapy. Cancer stem cells have recently been recognized and validated as a key target for cancer treatment. Cripto-1, which is a GPI-anchored membrane-bound protein that functions as a co-receptor of Nodal, is a marker of cancer stem cells. Since Nodal is a member of the TGF-β family, which performs an important role in stem cells and cancer stem cells, the inhibition of Cripto-1 could be a strategy by which to block Nodal signaling and thereby suppress cancer stem cells. We propose that Cripto-1 may be a novel target for cancer immunotherapy.

Abstract

The immune system has been found to be suppressed in cancer patients. Cancer cells are extremely resistant to chemotherapeutic drugs, conventional immunotherapy, or cancer antigen vaccine therapy. Cancer immunotherapy, which is mainly based on immune checkpoint inhibitors, such as those for PD-1, PD-L1, and CTLA4, is an effective treatment method. However, no immunotherapeutic target has been found that retains validity in the face of tumor diversity. The transforming growth factor (TGF)-β cytokine family possesses broad biological activity and is involved in the induction and/or transdifferentiation of helper T cells, which are important in immunotherapy. Nodal is a member of the TGF-β family playing important roles in tissue stem cells and cancer stem cells (CSCs), interacting with the co-receptor Cripto-1, as well as with Activin type IB (Alk4) and Activin typeIIreceptors, and maintaining stemness and Notch and Wnt/β-catenin signaling in CSCs. In recent years, it has been reported that Cripto-1 could be a potential therapeutic target in CSCs. Here, we review the accumulated literature on the molecular mechanisms by which Cripto-1 functions in CSCs and discuss the potential of Cripto-1 as an immunotherapeutic target in CSCs.

Paclitaxel-Based Chemotherapy Targeting Cancer Stem Cells from Mono- to Combination Therapy

Paclitaxel (PTX) is a chemotherapeutical agent commonly used to treat several kinds of cancer. PTX is known as a microtubule-targeting agent with a primary molecular mechanism that disrupts the dynamics of microtubules and induces mitotic arrest and cell death. Simultaneously, other mechanisms have been evaluated in many studies. Since the anticancer activity of PTX was discovered, it has been used to treat many cancer patients and has become one of the most extensively used anticancer drugs. Regrettably, the resistance of cancer to PTX is considered an extensive obstacle in clinical applications and is one of the major causes of death correlated with treatment failure. Therefore, the combination of PTX with other drugs could lead to efficient therapeutic strategies. Here, we summarize the mechanisms of PTX, and the current studies focusing on PTX and review promising combinations.

How can we turn the PI3K/AKT/mTOR pathway down? Insights into inhibition and treatment of cancer

Introduction: The phosphatidylinositol 3-kinase/protein kinase-B/mammalian target of rapamycin (PI3K/AKT/mTOR) pathway is a fundamental regulator of cell proliferation and survival. Dysregulation in this pathway leads to the development of cancer. Accumulating evidence indicates that dysregulation in this pathway is involved in cancer initiation, progression, and recurrence. However, the pathway consists of various signal transducing factors related with cellular events, such as transformation, tumorigenesis, cancer progression, and drug resistance. Therefore, it is very important to determine the targets in this pathway for cancer therapy. Although many drugs inhibiting this signaling pathway are in clinical trials or have been approved for treating solid tumors and hematologic malignancies, further understanding of the signaling mechanism is required to achieve better therapeutic efficacy.Areas covered: In this review, we have describe the PI3K/AKT/mTOR pathway in detail, along with its critical role in cancer stem cells, for identifying potential therapeutic targets. We also summarize the recent developments in different types of signaling inhibitors.Expert opinion: Downregulation of the PI3K/AKT/mTOR pathway is very important for treating all types of cancers. Thus, further studies are required to establish novel prognostic factors to support the current progress in cancer treatment with emphasis on this pathway.

A Novel Artificially Humanized Anti-Cripto-1 Antibody Suppressing Cancer Cell Growth

Cripto-1 is a member of the EGF-CFC/FRL1/Cryptic family and is involved in embryonic development and carcinogenesis. We designed a novel anti-Cripto-1 artificial antibody and assessed the recognition to the antigen and the potential to suppress the growth of cancer stem cells. First, single chain antibody clones were isolated by bio-panning with the affinity to recombinant Cripto-1 protein from our original phage-display library. Then, the variable regions of heavy chain VH and light chain VL in each clone were fused to constant regions of heavy chain CH and light chain CL regions respectively. These fused genes were expressed in ExpiCHO-S cells to produce artificial humanized antibodies against Cripto-1. After evaluation of the expression levels, one clone was selected and the anti-Cripto-1 antibody was produced and purified. The purified antibody showed affinity to recombinant Cripto-1 at 1.1 pmol and immunoreactivity to cancer tissues and cell lines. The antibody was available to detect the immunoreactivity in tissue microarrays of malignant tumors as well as in Cripto-1 overexpressing cells. Simultaneously, the antibody exhibited the potential to suppress the growth of human colon cancer derived GEO cells overexpressing Cripto-1 with IC₅₀ at approximately 110 nM. The artificially humanized antibody is proposed to be a good candidate to target cancer cells overexpressing Cripto-1.

Isolation and characterization of cancer stem cells derived from human glioblastoma

Cancer stem cell (CSC) is considered as a cause of cancer recurrence and metastasis. Simultaneously CSCs are responsible for the heterogeneous population in tumor tissues due to their differentiation potential. However, the characterizations of CSCs are still not enough and cancer stem cell lines widely available is desired to be established for the advancement of cancer research. In this study, we tried to isolate and characterize stem like cells from human glioblastoma cell line U-251MG cells. U-251MG P1 cells, which was previously condensed in the presence of hyaluronic acid as CD44 positive population were subjected to single cell isolation procedure. Although 5 clones were isolated, only one clone exhibited high expression of CD44, Nanog, OCT3/4 and SOX2, and named U-251MGSC1. The sphere forming ability of U-251MGSC1 cell was significantly higher than the parental U-251MG cells. Tumorigenicity of U-251MG-SC1 cells were higher than that of U-251MG cells. U-251MGSC1 cells exhibited higher expression of CD44, SOX2, Nestin and A2B5 than U-251MG cells in vitro and in vivo. The expression of GFAP and NF-M was enhanced when the cells were treated with the conditioned medium of U-251MG cells indicating the potential of differentiation. Sphere forming ability was more efficient than that of U-251MG cells and was enhanced in the presence of hyaluronic acid, which enhanced the cell growth as well. U-251MGSC1 cells exhibited rapid growth tumor in nude mice and efficient metastatic ability in transmembrane assay when compared with U-251MG cells. As the result, we concluded U-251MGSC1 cell was a glioblastoma CSC line derived from the parental U-251MG cells. U-251MGSC1 cells will be a good tool to develop effective therapeutic agents against CSCs and to elucidate the properties of glioma derived CSCs and the mechanism of tumor development in brain.

Abstract PR001: Cancer stem cells as origin of tumor associated immune cells

Development of cancer stem cell (CSC) models from induced pluripotent stem cells (iPSCs) for different types of cancers will help to investigate the tumorigenesis and tumor microenvironment heterogeneity. In this context, our lab have developed a novel method to generate CSCs from iPSCs under cancer microenvironment using conditioned medium from different cancer cell lines. On the other hand, the ability of CSCs to exhibit different hematopoietic cells is still unclear. In our previous study, BT549 cell line conditioned media was used to obtain CSCs. CSCs (miPSCs-BT) converted from mouse iPSCs were tumorigenic and expressed stemmens and cancer stem cell markers. CSCs converted from miPSCs and injected into mice were used. CSCs isolated from malignant tumor were cultured in absence of Leukemia Inhibitory Factor(LIF) where undifferentiated cells were selected using puromycin. Non-adherent cells (NACs) arising from adherent CSCs collected and their viability, the morphology and the expression of hematopoietic cell markers were investigated. NACs were also injected into the tail vein of busulfan conditioned Balb/c nude mice. CSCs were also induced to differentiate into macrophages while using IL3 and SCF. The round nucleated NACs were viable, positive for hematopoietic lineage markers and had CD34 positive subpopulation as well as the ability of homing to the bone marrow. Moreover, after 4 weeks of injection, Wright-Giemsa staining showed that the number of white blood cells was higher in injected mice with NACs comparing to the control. CSCs also showed the ability to differentiate toward macrophages. In conclusion, CSCs were demonstrated to have the potential to provide progenies with hematopoietic markers, morphology, and homing ability to the bone marrow, which could give new insight into the tumor microenvironment according to the plasticity of CSCs.

This abstract is also being presented as PO057.

Citation Format: Ghmkin Hassan, Said M. Afify, Akimasa Seno, Masaharu Seno. Cancer stem cells as origin of tumor associated immune cells [abstract]. In: Abstracts: AACR Virtual Special Conference: Tumor Immunology and Immunotherapy; 2020 Oct 19-20. Philadelphia (PA): AACR; Cancer Immunol Res 2021;9(2 Suppl):Abstract nr PR001.

I. How can you choose the fate of iPSCs and stem cells, Regeneration or Carcinogenesis? A hypothetical insight.: II. Modelling human beta cell development with pluripotent stem cells

It is nowadays taken granted that induced pluripotent stem cells (iPSCs) are available for the regeneration therapy since iPSCs differentiate into any kind of phenotypes. If iPSCs can choose their fate in every way of differentiation why they do not choose cancer phenotype. As a body develops for one fertilized egg, embryonic stem cell must choose every phenotype of tissues such as blood, neuron, lung, liver, pancreas and so on depending on the stages. And sometimes the cells get cancer. So do iPSCs because iPSCs are almost equivalent to embryonic cells. Then how can the safety of the regeneration therapy be maintained with iPSCs? When inducing the differentiation of iPSCs it is considered important to choose the proper conditions of culture such as 3D-platform for embryoid, supplement of cytokines and growth factors, inhibition of signaling and so on. On the other hand, several conditions have been reported to induce cancer stem cells. The cancer inducing conditions are possibly summarized as the factors chronically exposed to iPSCs. It is further worthwhile noticing that the conditions do not appear to induce mutations but affecting the epigenetics. Collectively, to secure the safety of regeneration therapy, it appears the best way to avoid the conditions to induce cancer stem cells. Further insights in details will be discussed in the lecture. Type 1 Diabetes (T1D) is an autoimmune disease characterized by destruction of the pancreatic beta cells and loss of insulin. Using the Edmonton protocol, donor-derived islets seeded into the liver successfully restore glycemia in 58% of T1D patients. However, donor scarcity, risks associated with immunosuppressants and poor engraftment limit this therapeutic application to a small number of patients. To overcome these challenges, the developmental potential of human embryonic stem cells and human induced pluripotent stem cells is being harnessed to produce surrogate islets in vitro. We and others have been able to mimic human embryonic development and generate pancreatic progenitors (PP) that have the ability to mature into insulin-producing beta-like cells both in vitro and in vivo. Transplantation of pancreatic progenitors in the kidney capsule of immunodeficient mice leads to formation of islet-like structures that secrete human insulin. However, there are some limitations to the use of pancreatic progenitors for the treatment of T1D. First and foremost, their safety as the PP population can be heterogenous and highly proliferative, which might lead to formation of cellular outgrowth or teratoma after transplantation. Second, while insulin-producing cells develop in vivo 6 weeks after transplantation, restoration of normoglycemia occurs ~5 months later, suggesting that these "early" insulin-producing cells are immature, or poorly connected to the host vasculature. We have been addressing these two limitations and developed approaches to 1) improve safety by identifying markers to purify the PP populations and 2) accelerate functionality by improving vascularization at the time of transplantation.

An assay for cancer stem cell-induced angiogenesis on chick chorioallantoic membrane

Angiogenesis is generally involved in tumor growth and metastasis. Cancer stem cells (CSCs) are considered to facilitate the angiogenesis. Therefore, CSCs could be the effective targets to stop angiogenesis. Recently, our group successfully generated CSC models from induced pluripotent stem cells (iPSCs) in the presence of conditioned medium derived from cancer derived cells. These novel model CSCs has been characterized by highly tumorigenic, angiogenic and metastatic potentials in vivo. The angiogenic potential of CSCs has been explained by the expression of both angiogenic factors and their receptors implying the angiogenesis in autocrine manner. In this protocol we optimized the method to evaluate tumor angiogenesis with the CSC model, which was described effective to assess sorafenib as an antiangiogenic drug, on chick chorioallantoic membrane (CAM) assay. Our results demonstrate that CSCs developed from iPSCs and CAM assay are a robust and cost-effective tool to evaluate tumor angiogenesis with CSCs. Collectively, CSCs in CAM assay could serve as a very useful model for the screening of potential therapeutic agents targeting tumor angiogenesis.

Tumor-associated macrophages derived from cancer stem cells

Macrophages are the most abundant immune cells in the microenvironment of solid tumors. The present study displayed histological and immunohistochemical analyses of a malignant tumor model developed from cancer stem cells (CSCs) converted from human induced pluripotent stem cells (hiPSCs) in a cancer microenvironment prepared from the conditioned medium (CM) of a pancreatic cancer cell line. We focused on the localization and the origin of tumor-associated macrophages (TAMs), To the best of our knowledge this may be the first study to suggest the potential differentiation of CSCs to TAMs. hiPSCs were converted into CSCs in the presence of CM from PK8 cells. CSCs were then transplanted in vivo and formed primary tumors. Primary cultures for these tumors were serially transplanted again to obtain secondary tumors. Secondary tumors exhibited histopathological features of malignancy. Cells derived from tumors maintained the expression of endogenous stemness markers and pancreatic CSCs markers. Simultaneously, high immunoreactivity to anti-mouse CD68, anti-human CD68, CD206 and CD11b antibodies were detected revealing that the tumor tissue derived from CSCs was enriched for macrophages which can originate from both human and mouse cells. The model of CSCs highlighted the possibility of CSCs to differentiate into TAMs.

Abstract PO-037: The conversion of induced pluripotent stem cells into cancer stem cells under pancreatic cancer microenvironment is inhibiting by lapatinib

Cancer stem cells (CSCs) are suggested to be responsible for drug resistance and aggressive phenotypes of tumors. Mechanisms that regulating CSCs are still under investigation. Our lab has established a novel method to produce CSCs from induced pluripotent stem cells (iPSCs) under cancer microenvironment using conditioned medium (CM) from cancer cell lines. By treatment iPSCs with CM, cells gain CSC characteristics. Here, we analyzed transcriptome from CSCs, which converted from iPSCs using CM from pancreatic ductal adenocarcinoma cells, and differentially expressed genes were identified. Pathway enrichment was analyzed by the Kyoto Encyclopedia of Genes and Genomes (KEGG). Comparing iPSCs with CSCs converted from iPSCS showed elevated expression of genes related to ERBB2, ERBB3 and PI3K, while KEGG pathways revealed enrich of pathways known to be involved in cancer including ERBB2/ERBB3 signal pathway by conversion of iPSCs to CSCs. Inhibition of ERBB2 by lapatinib induced cell proliferation arrest and losing of tumorgenicity of converted cells. This study shows a potential involvement of ERBB2/ERBB3 pathway in CSCs generation and could lead to potentially new options for cancer treatment and prevention.

Citation Format: Ghmkin Hassan, Masaharu Seno. The conversion of induced pluripotent stem cells into cancer stem cells under pancreatic cancer microenvironment is inhibiting by lapatinib [abstract]. In: Proceedings of the AACR Virtual Special Conference on Pancreatic Cancer; 2020 Sep 29-30. Philadelphia (PA): AACR; Cancer Res 2020;80(22 Suppl):Abstract nr PO-037.

Abstract PO-094: Human pluripotent stem cells acquire malignancy under tumor microenvironment

Cancer stem cell (CSC) theory suggests that cancer tissue contains a subpopulation of stem-like cells with self-renewal and differentiation potential as normal stem cells maintain organs by self-renewing and differentiation. Even in both cases of malignancy and normal the stemness is affected by the niche surrounding the stem cells. In the initial stage no stem cells should be related with cancer. The most important question is “How come the stem cells acquire malignancy?” Here in this study, using human induced pluripotent stem cells (iPSCs) we tried to generate cancer stem cells in the presence of the conditioned medium (CM) derived from human liver cancer cell line Hep 3B cells and human breast cancer cell line BT459 cells. The CM from both cells was collected when the cells became confluent and sterilized by 0.22 micrometer filter. The colonies of human iPSCs were detached from a mitomycin treated fibroblast feeder layer by collagenase and manually dissected into small pieces which were transferred onto ultra-low-attachment dishes. After 7 days the formed embryoid bodies (EBs) of human iPSCs were plated on Matrigel coated plates and maintained in Repro FF2 medium containing 5 ng/ml of basic FGF. Just after 24 hours from plating on Matrigel, the EBs of human iPSCs were treated with CM mixed with Repro FF2, in the ratio of 1:1. The medium was changed every two days with CM for 4 weeks. EBs cultured in the complete Repro FF2 medium without CM were prepared as the control but did not survive for 4 weeks. The survived cells were analyzed by RT-qPCR analysis and Immunofluorescence (IF) staining to confirm the expression of stemness and CSC markers and evaluated the conversion of iPSCs into CSCs. Distinct expression of self-renewal and CSC markers, such as Nanog, SOX2, CD44 and EPCAM, were observed in the survived cells. Sphere formation assay further confirmed the potential of self-renewal in the survived cells. The survived cells possessed differentiation potential into vascular endothelial-like cells. Thus, we concluded the iPSCs were converted into CSCs (hiPS-CSCs). Through these experiments, 2 different conditions derived from 2 independent cell lines Hep3B and BT549 cells were successful to hiPS-CSCs as hiPS-Hep3Bcm and hiPS-BT549cm cells. Furthermore, being treated with paclitaxel, the hiPS-CSCs exhibited potential of chemo-resistance maintaining the intact clonogenic morphology when compared to hiPSC. This study tries to summarize human cancer disease by utilizing the tumor microenvironment in the form of conditioned medium without any genetic manipulation. This should pave the way for the establishment of effective therapeutic agents.

Citation Format: Said M. Afify, Ghmkin Hassan, Akimasa Seno, Yoshiaki Iwasaki, Masaharu Seno. Human pluripotent stem cells acquire malignancy under tumor microenvironment [abstract]. In: Proceedings of the AACR Virtual Special Conference on Tumor Heterogeneity: From Single Cells to Clinical Impact; 2020 Sep 17-18. Philadelphia (PA): AACR; Cancer Res 2020;80(21 Suppl):Abstract nr PO-094.

Abstract 6012: Cancer stem cells could be responsible for the chimeras of hematopoietic cells in the cancer microenvironment

Development of cancer stem cells (CSCs) model from iPSCs for different types of cancers will help to investigate the tumorigenesis and designing new therapies applicable to CSCs. In this context, our lab has developed a novel method to generate CSCs from iPSCs under cancer microenvironment using conditioned medium from different cancer cell lines. In our previous study, BT549 cell line conditioned media was used to convert iPSCs to CSCs (miPSCs-BTcscs). Here, we investigated the potential of adherent CSCs converted from iPSCs to give hematopoietic like cells. Cancer stem cells, miPSCs-BTcscs, were obtained by conversion of miPSCs (iPS MEF-Ng-20D-17) cells in the presence of conditioned medium from breast cancer cell line BT549 cells followed by the primary culture of the tumor formed in Balb/c nude mice. The stemness and tumorigenicity of miPSCs-BTcscs cells had previously been confirmed. miPSCs-BTcscs cells were cultured on gelatin coated dish in absence of Leukemia Inhibitory Factor (LIF) and select undifferentiated cells was done using puromycin. Non-adherent cells (NACs) arising from adherent CSCs collected and their viability, the morphology and the expression of hematopoietic cells markers were investigated using Giemsa staining, flow cytometry, immunofluorescence staining, and RT-PCR. Moreover, to assess the potential of clonogenicity in vivo and the engraftment of NACs, NACs were injected into the tail vein of busulfan conditioned Balb/c nude mice. The round nucleated NACs were found to be viable, positive for Lin markers and CD34 and expressed hematopoietic markers just like homing to the bone marrow. When NACs were injected into a mouse, Wright-Giemsa staining showed that the number of white blood cells got higher than those in the control mice after 4 weeks. As conclusion, CSCs were demonstrated to have the potential to provide progenies with hematopoietic markers, morphology and homing ability to bone marrow, which could give a new insight into tumor microenvironment according to the plasticity of CSCs.

Citation Format: Ghmkin Hassan, Said M Afify, Kazuki Kumon, Amira Osman, Maram H Zahra, Akimasa Seno, Masaharu Seno. Cancer stem cells could be responsible for the chimeras of hematopoietic cells in the cancer microenvironment [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 6012.

Signaling Inhibitors Accelerate the Conversion of mouse iPS Cells into Cancer Stem Cells in the Tumor Microenvironment

Cancer stem cells (CSCs) are a class of cancer cells characterized by self-renewal, differentiation and tumorigenic potential. We previously established a model of CSCs by culturing mouse induced pluripotent stem cells (miPSCs) for four weeks in the presence of a conditioned medium (CM) of cancer cell lines, which functioned as the tumor microenvironment. Based on this methodology of developing CSCs from miPSCs, we assessed the risk of 110 non-mutagenic chemical compounds, most of which are known as inhibitors of cytoplasmic signaling pathways, as potential carcinogens. We treated miPSCs with each compound for one week in the presence of a CM of Lewis lung carcinoma (LLC) cells. However, one-week period was too short for the CM to convert miPSCs into CSCs. Consequently, PDO325901 (MEK inhibitor), CHIR99021 (GSK-3β inhibitor) and Dasatinib (Abl, Src and c-Kit inhibitor) were found to confer miPSCs with the CSC phenotype in one week. The tumor cells that survived exhibited stemness markers, spheroid formation and tumorigenesis in Balb/c nude mice. Hence, we concluded that the three signal inhibitors accelerated the conversion of miPSCs into CSCs. Similarly to our previous study, we found that the PI3K-Akt signaling pathway was upregulated in the CSCs. Herein, we focused on the expression of relative genes after the treatment with these three inhibitors. Our results demonstrated an increased expression of pik3ca, pik3cb, pik3r5 and pik3r1 genes indicating class IA PI3K as the responsible signaling pathway. Hence, AKT phosphorylation was found to be up-regulated in the obtained CSCs. Inhibition of Erk1/2, tyrosine kinase, and/or GSK-3β was implied to be involved in the enhancement of the PI3K-AKT signaling pathway in the undifferentiated cells, resulting in the sustained stemness, and subsequent conversion of miPSCs into CSCs in the tumor microenvironment.

Blood and Cancer: Cancer Stem Cells as Origin of Hematopoietic Cells in Solid Tumor Microenvironments

The concepts of hematopoiesis and the generation of blood and immune cells from hematopoietic stem cells are some steady concepts in the field of hematology. However, the knowledge of hematopoietic cells arising from solid tumor cancer stem cells is novel. In the solid tumor microenvironment, hematopoietic cells play pivotal roles in tumor growth and progression. Recent studies have reported that solid tumor cancer cells or cancer stem cells could differentiate into hematopoietic cells. Here, we discuss efforts and research that focused on the presence of hematopoietic cells in tumor microenvironments. We also discuss hematopoiesis from solid tumor cancer stem cells and clarify the notion of differentiation of solid tumor cancer stem cells into non-cancer hematopoietic stem cells.

Cancer stem cell induction from mouse embryonic stem cells

Although cancers are often removed by surgery and treated by chemotherapy and/or radiation therapies, they often reoccur following treatment due to the presence of resistant residual cells such as cancer stem cells (CSCs). CSCs are characterized by their self-renewal, pluripotency, and tumorigenicity properties, and are promising therapeutic targets for the complete therapy of cancers; however, the number of CSCs in cancer tissue is typically too small to investigate fully. We have previously reported that CSCs could be established from induced pluripotent stem cells (iPSCs) using a conditioned medium during cancer cell culture. In the present study, mouse embryonic stem cells (mESCs) were observed to be converted to CSCs (mES-CSCs). This demonstrated that CSC induction does not exclusively occur following gene editing in somatic cells, and that conditioned medium from cancer cells may contain factors that can induce CSCs. Therefore, not only iPSCs but also mESCs, were demonstrated to be able to produce CSCs as one of the potentials of pluripotency of stem cells, suggesting that the conversion to CSCs is not specific to iPSCs. The resultant mES-CSCs would be also useful to generate tissue specific cancers and these naturally occurring cancers can contribute to drug screenings, but also undergo further investigation in order to reveal cancer mechanisms.

Conversion of Stem Cells to Cancer Stem Cells: Undercurrent of Cancer Initiation

Cancer stem cells (CSCs) also known as cancer-initiating cells (CIC), are responsible for the sustained and uncontrolled growth of malignant tumors and are proposed to play significant roles in metastasis and recurrence. Several hypotheses have proposed that the events in either stem and/or differentiated cells, such as genomic instability, inflammatory microenvironment, cell fusion, and lateral gene transfer, should be considered as the possible origin of CSCs. However, until now, the exact origin of CSC has been obscure. The development of induced pluripotent stem cells (iPSCs) in 2007, by Yamanaka's group, has been met with much fervency and hailed as a breakthrough discovery by the scientific and research communities, especially in regeneration therapy. The studies on the development of CSC from iPSCs should also open a new page of cancer research, which will help in designing new therapies applicable to CSCs. Currently most reviews have focused on CSCs and CSC niches. However, the insight into the niche before the CSC niche should also be of keen interest. This review introduces the novel concept of cancer initiation introducing the conversion of iPSCs to CSCs and proposes a relationship between the inflammatory microenvironment and cancer initiation as the key concept of the cancer-inducing niche responsible for the development of CSC.

A Novel Combination Cancer Therapy with Iron Chelator Targeting Cancer Stem Cells via Suppressing Stemness

Excess iron causes cancer and is thought to be related to carcinogenesis and cancer progression including stemness, but the details remain unclear. Here, we hypothesized that stemness in cancer is related to iron metabolism and that regulating iron metabolism in cancer stem cells (CSCs) may be a novel therapy. In this study, we used murine induced pluripotent stem cells that expressed specific stem cell genes such as Nanog, Oct3/4, Sox2, Klf4, and c-Myc, and two human cancer cell lines with similar stem cell gene expression. Deferasirox, an orally available iron chelator, suppressed expression of stemness markers and spherogenesis of cells with high stemness status in vitro. Combination therapy had a marked antitumor effect compared with deferasirox or cisplatin alone. Iron metabolism appears important for maintenance of stemness in CSCs. An iron chelator combined with chemotherapy may be a novel approach via suppressing stemness for CSC targeted therapy.

Use of DNA-generated gold nanoparticles to radiosensitize and eradicate radioresistant glioma stem cells

The surface reactivity of gold nanoparticles (AuNPs) is receiving attention as a radiosensitizer of cancer cells for radiation therapy and/or as a drug carrier to target cells. This study demonstrates the potential of DNA-AuNPs (prepared by mixing calf thymus DNA with HAuCl₄ solution) as a radiosensitizer of human glioma cells that have cancer stem cell (CSC)-like properties, to reduce their survival. CSC-like U251MG-P1 cells and their parental glioblastoma U251MG cells are treated with a prepared DNA-AuNP colloid. The radiosensitivity of the resultant AuNP-associated cells are significantly enhanced. To reveal the mechanism by which survival is reduced, the generation of reactive oxygen species (ROS), apoptosis induction, or DNA damage in the cells is assayed using the fluorescent dye DCFDA, annexin V-FITC/PI, and foci formation of γ-H2AX, respectively. X-ray irradiation with administration of AuNPs overcomes the radioresistance of U251MG-P1 cells. It does not induce ROS generation or apoptosis in the cells but enhances the number of abnormal nuclei with abundant γ-H2AX foci, which is judged as cell death by mitotic catastrophe. The AuNP association with the cells effectively induces mitotic catastrophe in x-ray-irradiated CSC-like cells, implicating that DNA-AuNPs might be a promising tool to develop an efficient radiosensitizer against CSC.

Daunorubicin can eliminate iPS-derived cancer stem cells via ICAD/CAD-independent DNA fragmentation

Aim: To identify a drug that can effectively eliminate these cancer stem cells (CSCs) and determine its mode of action.

Methods: CSCs were obtained from mouse induced pluripotent stem cells (miPSCs) using cancer cell-conditioned media. Drug screening was performed on these cells or after transplantation into mice. Apoptosis was analyzed by flow cytometry and western blotting.

Results: Drug screening studies showed that daunorubicin, a topoisomerase II inhibitor, is specifically cytotoxic to miPS-CSCs. Daunorubicin-induced apoptosis was found to be associated with p53 accumulation, activation of the caspase cascade, and oligonucleosomal DNA fragmentation. Treatment with the caspase inhibitor abolished daunorubicin-induced DNA fragmentation and was therefore considered to act downstream of caspase activation. This was also suppressed by treatment with a Ca²⁺-specific chelator, which suggested that CAD endonuclease does not contribute. Moreover, no obvious ICAD reduction/degradation was detected.

Conclusion: Daunorubicin effectively eliminated CSCs, which are dependent on the p53/caspase signaling cascade. The current findings provided the basis for further studies on CSC-targeted drugs for the development of cancer treatment strategies.

Five Fibrosis Biomarkers Together with Serum Ferritin Level to Diagnose Liver Fibrosis and Cirrhosis

BACKGROUND

Liver fibrosis is a dynamic procedure that results from an irregularity between fibrogenesis and fibrolysis. After time this procedure can lead to cirrhosis of the liver. Liver fibrosis and cirrhosis assessment is very important for both therapeutic decisions and prognostic evaluations. In this study, we tried to use serum ferritin (SF) together with five fibrosis tests (Age-Platelet index (API), aspartate aminotransferase to alanine aminotransferase ratio (AAR), AST to platelet ratio index (APRI), Fibrosis 4 score (FIB-4), and fibro-quotient (Fibro-Q)) to assess liver fibrosis and cirrhosis and estimate possible correlation between inflammation and SF.

METHODS

This study was carried out on eighty-eight patients infected with HCV and twenty healthy subjects as a control. Complete blood count (CBC), aspartate aminotransferase (AST), alanine aminotransferase (ALT), antiHCV antibody, detection of HCV RNA by real-time PCR, and serum ferritin (SF) were assessed. Then API, ARR, APRI, FIB-4, and Fibro-Q were calculated. Different fibrosis stages (mild fibrosis stage (F1), moderate fibrosis stage (F2), severe fibrosis stage (F3), cirrhotic stage (F4)) were assessed using transient elastography by Fibro Scan®.

RESULTS

FIB-4 index was significantly elevated (p < 0.01) with the progression of liver fibrosis at F1, F2, F3, and F4 when compared to healthy control group. The APRI score elevation between F0 and F3 and between F0 and F4 was significant (p < 0.01). SF was elevated in all fibrosis stages and significantly (p < 0.01) at F3 and F4 compared to controls.

CONCLUSIONS

APRI coupled with SF should be the best reliable biomarkers for liver cirrhosis. Simultaneously, from our data SF involved in all stages of inflammation. Therefore, down regulation of ferritin in the early stage of fibrosis should be helpful in decreasing the inflammatory effect of ferritin.

Five Fibrosis Biomarkers Together with Serum Ferritin Level to Diagnose Liver Fibrosis and Cirrhosis

BACKGROUND

Liver fibrosis is a dynamic procedure that results from an irregularity between fibrogenesis and fibrolysis. After time this procedure can lead to cirrhosis of the liver. Liver fibrosis and cirrhosis assessment is very important for both therapeutic decisions and prognostic evaluations. In this study, we tried to use serum ferritin (SF) together with five fibrosis tests (Age-Platelet index (API), aspartate aminotransferase to alanine aminotransferase ratio (AAR), AST to platelet ratio index (APRI), Fibrosis 4 score (FIB-4), and fibro-quotient (Fibro-Q)) to assess liver fibrosis and cirrhosis and estimate possible correlation between inflammation and SF.

METHODS

This study was carried out on eighty-eight patients infected with HCV and twenty healthy subjects as a control. Complete blood count (CBC), aspartate aminotransferase (AST), alanine aminotransferase (ALT), antiHCV antibody, detection of HCV RNA by real-time PCR, and serum ferritin (SF) were assessed. Then API, ARR, APRI, FIB-4, and Fibro-Q were calculated. Different fibrosis stages (mild fibrosis stage (F1), moderate fibrosis stage (F2), severe fibrosis stage (F3), cirrhotic stage (F4)) were assessed using transient elastography by Fibro Scan®.

RESULTS

FIB-4 index was significantly elevated (p < 0.01) with the progression of liver fibrosis at F1, F2, F3, and F4 when compared to healthy control group. The APRI score elevation between F0 and F3 and between F0 and F4 was significant (p < 0.01). SF was elevated in all fibrosis stages and significantly (p < 0.01) at F3 and F4 compared to controls.

CONCLUSIONS

APRI coupled with SF should be the best reliable biomarkers for liver cirrhosis. Simultaneously, from our data SF involved in all stages of inflammation. Therefore, down regulation of ferritin in the early stage of fibrosis should be helpful in decreasing the inflammatory effect of ferritin.

Suppression effect on IFN-γ of adipose tissue-derived mesenchymal stem cells isolated from β2-microglobulin-deficient mice

Administration of bone marrow-derived mesenchymal stem cells (MSCs) is a possible treatment for graft-versus-host disease (GVHD) following allogeneic hematopoietic stem cell transplantation and other inflammatory conditions. To address the mechanism of immunosuppression by MSCs, in particular those derived from adipose tissue (AMSCs), AMSCs were isolated from three different mouse strains, and the suppressive capacity of the AMSCs thus obtained to suppress interferon (IFN)-γ generation in mixed lymphocyte reaction cultures serving as an in vitro model of GVHD were assessed. It was revealed that the AMSCs had a potent capacity to suppress IFN-γ production regardless of their strain of origin and that such suppression was not associated with production of interleukin-10. In addition, the results demonstrated that β2-microglobulin (β2m)-deficient AMSCs from β2m^-/- mice were also potent suppressor cells, verifying the fact that the mechanism underlying the suppression by AMSCs is independent of major histocompatibility complex (MHC) class I expression or MHC compatibility. As AMSCs appear to have immunosuppressive properties, AMSCs may be a useful source of biological suppressor cells for the control of GVHD in humans.

Abstract 3055: A model of CSC converted from iPSC in the conditioned medium of HCC paving the way to establish HCC CSC

Hepatocellular carcinoma (HCC) represents the major histological subtype, accounting for 70%–85% of cases of primary liver cancer. Liver CSCs sustain their self-renewal remains largely unknown. The self-renewal and pluripotency of liver CSC are maintained by several signaling cascades. However, the mechanism of regulating these signaling is unknown.

In this study, we tried to convert mouse iPSCs into CSCs with the conditioned medium (CM) from human HCC cell line Huh7 cells without any genetic manipulation aiming at establishing liver CSCs.

First of all, CM was collected from confluent culture of Huh7 cells. Then, mouse iPSCs cells without MEF feeder cells were cultured in the presence of 50% CM for 4 weeks. The medium was changed every day with fresh medium containing 50% of CM. Mouse iPSCs cultured in the complete medium with LIF were used as a control.The survived cells (5x105 cells) were suspended in HBSS and injected into the liver of BALB/c nude mice. After 25 days malignant tumor was formed in the liver while benign teratoma was formed by the injection of iPSCs. Tumors were then excised and partly fixed in 10% neutral formalin buffer solution for HE staining and immunohistochemical analysis. The rest of tumors were subjected to rt-qPCR anaylsis and primary culture. Immunohistochemical analysis with GFP antibody showed that malignant tumor sustained GFP expression while teratoma from miPSCs did not. Immunocytochemistry of the primary cells from malignant tumor showed high expression of both glypican-3 (GPC3) and cytokeratin19 (CK19) when compared to that in miPSCs. Expression of stem cell markers (Nanog, Oct3/4, Sox2, Klf4) and CSC markers (CD44, EpCAM) were also confirmed by rt-qPCR in both the CSCs converted from iPSCs (miPS-Huh7cm cells) and the primary culture cells. These results indicate that the primary cells from the malignant tumor are rich in CSCs with high expression of GPC3 and CK19, which paves the way to establish a model of HCC CSC. This model should be very important and useful to assess the significant molecular mechanisms necessary to maintain HCC CSC, which will help develop effective therapy of liver cancer.

Citation Format: Said M Afify, Anna Sanchez Calle, Kazuki Kumon, Hend M Nawara, Apriliana C Khairani, Hafizah Mahmud, Aung Ko Ko Oo, Du Juan, Maram H Zahara, Akimasa Seno, Tomonari Kasai, Yoshiaki Iwasaki, Masaharu Seno. A model of CSC converted from iPSC in the conditioned medium of HCC paving the way to establish HCC CSC [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3055.

Abstract 2005: CSCs induced from iPSCs indicate the trace of cancer cell culture conditioned media

Cancer stem cells (CSCs) show drug resistance and could be a source of cancer cells. Although these cells are recently considered more important than ever in cancer studies, the extremely small number of CSCs in actual cancer tissues makes the analysis difficult. Previously, we demonstrated that CSCs could be differentiated from induced pluripotent stem cells (iPSCs) in the presence of cancer cell conditioned media. We have confirmed the conditioned media from various types of cancer cell lines were successful to convert iPSCs into CSCs showing self-renewal property, differentiation potential, and tumorigenicity. To identify their differences between the generated CSCs, gene expression was compared by spherical self-organizing map (sSOM). Comparing with more than 1000 cells including stem cells, induced CSCs, CSCs obtained from cancer tissue or cancer cell line, and cancer cells or cancer tissues, known cancer stem cell markers were found not enough to classify CSCs. In the sSOM analysis, “ideal probe” (IP), which was supposed to characteristically be expressed in each group, was set to nomiate the marker gene. The distance close to the IP depicted some candidate marker genes in each group. The gene expression commonly shared among different types of CSCs was also searched. This IP revealed known cancer related gene Endthelin 1 as a commonly expressed gene. Moreover, when the CSCs were compared with the parental hiPSC and cancer cells, of which conditioned media was used for the conversion, sSOM showed that CSCs were not always differentiated towards their origin, but which genes should be responsible for generating CSCs. These results indicate that the induced CSCs should be the initial state of cancer cells and imply some important role of Endothelin 1 in CSC development.

Citation Format: Akimasa Seno, Tomonari Kasai, Heizo Tokutaka, Masaharu Seno. CSCs induced from iPSCs indicate the trace of cancer cell culture conditioned media [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2005.

HSP-enriched properties of extracellular vesicles involve survival of metastatic oral cancer cells

Cancer cells often secrete extracellular vesicles (EVs) that carry heat shock proteins (HSPs) with roles in tumor progression. Oral squamous cell carcinoma (OSCC) belongs to head and neck cancers (HNC) whose lymph-node-metastases often lead to poor prognosis. We have examined the EV proteome of OSCC cells and found abundant secretion of HSP90-enriched EVs in lymph-node-metastatic OSCC cells. Double knockdown of HSP90α and HSP90β, using small interfering RNA significantly reduced the survival of the metastatic OSCC cells, although single knockdown of each HSP90 was ineffective. Elevated expression of these HSP90 family members was found to correlate with poor prognosis of HNC cases. Thus, elevated HSP90 levels in secreted vesicles are potential prognostic biomarkers and therapeutic targets in metastatic OSCC.

Cytokine Expression and Macrophage Localization in Xenograft and Allograft Tumor Models Stimulated with Lipopolysaccharide

T cell-deficient mice such as nude mice are often used to generate tumor xenograft for the development of anticancer agents. However, the functionality of the other immune cells including macrophages, dendritic cells (DCs), and myeloid-derived suppressor cells (MDSCs) in the xenograft are largely unknown. Macrophages and dendritic cells (DCs) acquire functionally distinct properties in response to various environmental stimuli; the interaction of these cells with MDSCs in tumor microenvironments regulates cancer progression. Nude mice are less likely to reject human cancer cells because of major histocompatibility complex (MHC) mismatches. The tumor microenvironment in a xenograft, comprising human and mouse cells, exhibits more complex bidirectional signaling and function than that of allograft. Here, we evaluated the differences of myeloid cells between them. Plasma interferon-γ and interleukin-18 concentrations in the xenograft tumor model after lipopolysaccharide (LPS) administration were significantly higher than those in the allograft tumor model. MHC class I, II, and CD80 expression levels were increased in CD11b⁺ and MDSC populations after LPS administration in the spleen of a xenograft tumor model but not in that of an allograft tumor model. Additionally, the number of CD80- and mannose receptor C type 1 (MRC1)-expressing cells was decreased upon LPS administration in the tumor of the xenograft tumor. These results suggest that functions of macrophages and DCs are sustained in the xenograft, whereas their functions in response to LPS were suppressed in the allograft. The findings will encourage the consideration of the effects of myeloid cells in the xenograft for drug development.

Up-Regulation of PI 3-Kinases and the Activation of PI3K-Akt Signaling Pathway in Cancer Stem-Like Cells Through DNA Hypomethylation Mediated by the Cancer Microenvironment

Previously, we have succeeded in converting induced pluripotent stem cells (iPSCs) into cancer stem cells (CSCs) by treating the iPSCs with conditioned medium of Lewis lung carcinoma (LLC) cells. The converted CSCs, named miPS-LLCcm cells, exhibited the self-renewal, differentiation potential, and potential to form malignant tumors with metastasis. In this study, we further characterized miPS-LLCcm cells both in vivo and in vitro. The tumors formed by subcutaneous injection showed the structures with pathophysiological features consisting of undifferentiated and malignant phenotypes generally found in adenocarcinoma. Metastasis in the lung was also observed as nodule structures. Excising from the tumors, primary cultured cells from the tumor and the nodule showed self-renewal, differentiation potential as well as tumor forming ability, which are the essential characters of CSCs. We then characterized the epigenetic regulation occurring in the CSCs. By comparing the DNA methylation level of CG rich regions, the differentially methylated regions (DMRs) were evaluated in all stages of CSCs when compared with the parental iPSCs. In DMRs, hypomethylation was found superior to hypermethylation in the miPS-LLCcm cells and its derivatives. The hypo- and hypermethylated genes were used to nominate KEGG pathways related with CSC. As a result, several categories were defined in the KEGG pathways from which most related with cancers, significant and high expression of components was PI3K-AKT signaling pathway. Simultaneously, the AKT activation was also confirmed in the CSCs. The PI3K-Akt signaling pathway should be an important pathway for the CSCs established by the treatment with conditioned medium of LLC cells.

Practical Liposomal Formulation for Taxanes with Polyethoxylated Castor Oil and Ethanol with Complete Encapsulation Efficiency and High Loading Efficiency

Taxanes including paclitaxel and docetaxel are effective anticancer agents preferably sufficient for liposomal drug delivery. However, the encapsulation of these drugs with effective amounts into conventional liposomes is difficult due to their high hydrophobicity. Therefore, an effective encapsulation strategy for liposomal taxanes has been eagerly anticipated. In this study, the mixture of polyethoxylated castor oil (Cremophor EL) and ethanol containing phosphate buffered saline termed as CEP was employed as a solvent of the inner hydrophilic core of liposomes where taxanes should be incorporated. Docetaxel-, paclitaxel-, or 7-oxacetylglycosylated paclitaxel-encapsulating liposomes were successfully prepared with almost 100% of encapsulation efficiency and 29.9, 15.4, or 29.1 mol% of loading efficiency, respectively. We then applied the docetaxel-encapsulating liposomes for targeted drug delivery. Docetaxel-encapsulating liposomes were successfully developed HER2-targeted drug delivery by coupling HER2-specific binding peptide on liposome surface. The HER2-targeting liposomes exhibited HER2-specific internalization and enhanced anticancer activity in vitro. Therefore, we propose the sophisticated preparation of liposomal taxanes using CEP as a promising formulation for effective cancer therapies.

A cancer stem cell model as the point of origin of cancer-associated fibroblasts in tumor microenvironment

Cancer-associated fibroblasts (CAFs) are one of the most prominent cell types in the stromal compartment of the tumor microenvironment. CAFs support multiple aspects of cancer progression, including tumor initiation, invasion, and metastasis. The heterogeneous nature of the stromal microenvironment is attributed to the multiple sources from which the cells in this compartment originate. The present study provides the first evidence that cancer stem cells (CSCs) are one of the key sources of CAFs in the tumor niche. We generated CSC-like cells by treating mouse induced pluripotent stem cells with conditioned medium from breast cancer cell lines. The resulting cell population expressed both CSC and pluripotency markers, and the sphere-forming CSC-like cells formed subcutaneous tumors in nude mice. Intriguingly, these CSC-like cells always formed heterogeneous populations surrounded by myofibroblast-like cells. Based on this observation, we hypothesized that CSCs could be the source of the CAFs that support tumor maintenance and survival. To address this hypothesis, we induced the differentiation of spheres and purified the myofibroblast-like cells. The resulting cells exhibited a CAF-like phenotype, suggesting that they had differentiated into the subpopulations of cells that support CSC self-renewal. These findings provide novel insights into the dynamic interplay between various microenvironmental factors and CAFs in the CSC niche.

Abstract 926: Generation of a potential breast cancer stem cell model from induced pluripotent stem cells

The role of cancer stem cells (CSC) in the present scenario of breast cancer research is perceived as indispensable in the development and progression of the disease. The CSC niche maintains a heirarchy of heterogeneous cells, which facilitates the inception of the tumor until its invasion. Therefore, our study focuses on the development of an effective breast cancer stem cell model from mouse induced pluripotent stem cells (miPSCs).

Taking into consideration the intertumor heterogeneity of breast cancer, three human breast cancer cell lines, namely BT549, SKBR3 and T47D representing three major hormone subtypes were used to derive respective conditioned medium. The miPSCs were treated with these conditioned media separately for a period of one month following the protocol previously established by our laboratory. The resulting survived cells were subcutaneously and orthotopically transplanted into Balb/c nude mice. Within a short span of 15-20 days, both subcutaneous and orthotopic tumors were developed. Serial transplantations in to nude mice also generated malignant tumors with same vigor. Histopathological studies of these tumors confirmed a malignant infiltrating ductal carcinoma with apparent desmoplasia in orthotopic tumor and Her2 expression in comparison with subcutaneous ones, all of which confirmed us the conversion of miPSCs to CSCs. Presence of lung metastatic nodes further ascertained the invasiveness of this in vitro generated CSCs. Marked expression of prominent CSC markers namely CD44, Nanog, Sox2 and CD49f were observed in primary cells generated from these tumors. Tumor sphere formation assay further confirmed the presence of a good population of self renewing CSC population in the tumor tissues.

This study attempts to recapitulate human breast cancer disease in mice without any genetic manipulation, but by exploiting the tumor microenvironment in the form of conditioned medium. This should pave the way for the establishment of personalized therapy and a model to assess effective therapeutic interventions.

Citation Format: Neha Nair, Anna Sanchez Calle, Maram Hussein Zahra, Aung Ko Ko Oo, Arun Vaidyanath, Shinobu Masuda, Tomonari Kasai, Masaharu Seno. Generation of a potential breast cancer stem cell model from induced pluripotent stem cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 926. doi:10.1158/1538-7445.AM2017-926