Genesis Of Cancer Stem Cells Research Articles

OncomicroRNAs-Mediated Tumorigenesis: Implication in Cancer Diagnosis and Targeted Therapy.

MicroRNAs (miRNAs) control the expression of approximately 60% of protein-coding genes and regulate cell metabolism, proliferation, differentiation, and apoptosis. Notably, aberrant expression of miRNAs contributes to several diseases including cancer. Accumulating evidence indicates that miRNAs play important roles in EMT, genesis of cancer stem cells, cancer metabolism and carcinogenesis. Aberrant expression of miRNAs triggers tumor initiation, progression and poor prognosis of cancer patients. Accordingly, oncogenic miRNAs have emerged as diagnostic biomarkers and targets for novel anti-cancer drug discovery. However, the mechanisms of miRNAs contriving tumorigenesis are not completely understood. This review aims to clarify the identification of tumorspecific miRNAs, verification of oncogenic miRNA signatures, and dynamic study of oncogenic miRNAs in cancer initiation and development. Despite sound progress in miRNA-mediated anticancer therapy, several barriers like drug stability, immunogenicity, off-target effects and toxicities still remain. We hope our review could stimulate the further study of miRNAs in cancer research field, which may lead to new insights into the mechanisms of carcinogenesis and create new avenues for targeted cancer therapy.

Abstract SY08-02: Normal and neoplastic stem cells

Abstract The transition from single cell species to multicellular organisms led to organ and tissue development. The development and maintenance of organs/tissues in multicellular organisms has resulted in the emergence of specialized cells that self-renew as well as differentiate; these rare cells are stem cells. Following embryonic development, most of our tissues and organs are continuously regenerated from tissue/organ specific stem cells. The principal property that distinguishes such stem cells from their daughter cells is self-renewal; when stem cells divide they give rise to stem cells (by self-renewal) and progenitors (by differentiation). In most tissues only the primitive stem cells self-renew. Even within a particular tissue, stem cells may be diverse, and subject to stem cell competition for their niche. We have documented both germline stem cell and somatic stem cell competition in species as diverse as colonial protochordates and humans. Stem cell isolation and transplantation is the basis for regenerative medicine. Self-renewal is dangerous, and therefore strictly regulated. Poorly regulated self-renewal can lead to the genesis of cancer stem cells, the only self-renewing cells in the cancerous tumor. The Weissman lab has followed the progression from hematopoietic stem cells (HSCs) to myelogenous leukemias. They have found that the developing cancer clones progress at the stage of HSCs, until they become fully malignant. At this point, the “leukemia” stem cell is at a stage of a downstream oligolineage or multilineage progenitor that has evaded programmed cell death and programmed cell removal, while acquiring or keeping self-renewal. In the case of chronic myeloid leukemia, bcr-abl+ HSC clones outcompete normal HSCs in the chronic phase. The transition from the chronic phase to myeloid blast crisis results in the leukemia stem cells appearing in the granulocyte-macrophage progenitor (GMP) stage. While there are many ways to defeat programmed cell death and senescence, there appears to be one dominant method to avoid programmed cell removal—the expression of the cell surface “don't eat me” protein CD47, the ligand for macrophage SIRPα. All cancers tested express CD47 to overcome expression of “eat me” signals such as calreticulin. Antibodies that block the CD47-SIRPα interaction enable phagocytosis and killing of the tumor cells in vitro and in vivo. All tested human solid tumors and lymphomas/leukemias/myelomas express CD47 and are susceptible to phagocytosis in the presence of anti-CD47 blocking antibodies. Citation Format: Irving L. Weissman. Normal and neoplastic stem cells. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr SY08-02.

Origin of tumor stem cells

Cancer stem cells (CSCs) are units in cancer evolution. The elucidation the origin of CSCs has great significance on prevention and treatment of cancers. This paper discusses possible origins, genetic pathways and mechanisms of CSC on the basis of the literature and authors' research. Normal stem cells could be malignantly transformed to CSC through long term accumulation of gene mutations. Induction to pluripotent stem cells by reprogramming is a possible pathway for somatic cells to become CSCs. Dedifferentiation of cancer cells to CSCs is another pathway. Epithelial-mesenchymal transition (EMT), which is an important mechanism for cellular plasticity, plays important roles in cancer metastasis and stemness of cancer cells. Cell-fusion inducing EMT could be a mechanism for the genesis of CSCs. Infection of some virus is also related to the genesis of CSCs. The complexity of cancer biology was also discussed. Key words: Cancer stem cell; Cancer clonal evolution; Cellular plasticity; Cancer biology

Abstract 3016: Characterization of cancer stem-like cells derived from mouse induced pluripotent stem cells transformed by tumor-derived exosomes/microvesicles

Abstract It is widely accepted that the microenvironment/niche exert genetic and/or epigenetic effects on stem cells. Current studies have demonstrated that an aberrant microenvironment may contribute to the genesis of cancer stem cells (CSCs). In the case of cancer, growing evidence indicate a cancerous niche can play an active role in the regulation of tumor cell maintenance and progression through exosomes/microvesicles-based intercellular communication. It has not been reported, however, whether this vesicle-mediated communication induces the malignant transformation of normal stem cells/differentiating progenitors, result in CSC generation. Recentry, we have reported that the conditioned medium derived from the mouse Lewis Lung Carcinoma (LLC) cell line can convert mouse induced pluripotent stem cells (miPSCs) into CSCs. Here, we investigated the contribution of tumor-derived exosomes/microvesicles (TEMVs) that are secreted from LLC cells to induce the transformation of miPSCs into CSCs. The differentiating miPSCs were exposed to TEMVs derived from LLC cells for 4 weeks. We used Nanog-GFP miPS, in which GFP expression is under control of Nanog promoter, indicative of undifferentiation state. During this period, we observed the reemergence of the GFP-positive colonies, whereas most of cells were differentiated and GFP-negative without TEMV-treatment. The resultant TEMVs treated cells (miPS-LLCemv) expressed Nanog and Oct3/4 proteins comparable to miPSCs assessed by Western blotting. The sphere formation of the miPS-LLCemv cells in suspension culture indicated the selfrenewal capacity of the miPS-LLCemv cells. When the miPSLLCemv cells were subcutaneously allografted into immunodeficient mice, malignant tumors with extensive angiogenesis developed. Phathological features such as vementin, Ki67, PPAR gamma expression, and accumulation of lipid droplets in tumor revealed these tumors were liposarcomas. Tumor cells established from liposarcomas showed the capacity of spheroid formation in suspension culture and the capacity of differntiation into adipocytes and endothelial cells. These results indicate that miPS-LLCemv cells and established tumor cells possess CSC properties. Interestingly, these cells expressed Sox2 and Klf4 genes significantly higher than parental miPS cells, might be related to selfrenewal and addipogenesis. Thus, we concluded that TEMVs should have the potential to induce CSC properties in normal stem cells. Citation Format: Yan Ting, Junko Masuda, Akifumi Mizutani, Ling Chen, Tsukasa Shigehiro, Shuichi Matsuda, Tomonari Kasai, Takayuki Kudoh, Hiroshi Murakami, Mary J.C. Hendrix, Luigi Strizzi, David S. Salomon, Li Fu, Masaharu Seno. Characterization of cancer stem-like cells derived from mouse induced pluripotent stem cells transformed by tumor-derived exosomes/microvesicles. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3016. doi:10.1158/1538-7445.AM2014-3016

Abstract PL02-02: Investigating inhibition of the CD47 “don't eat me” signal to enable tumor phagocytic removal and augmented cross presentation to T cells

Abstract Following embryonic development, most of our tissues and organs are continuously regenerated from tissue/organ specific stem cells. The principal property that distinguishes such stem cells from their daughter cells is self-renewal; when stem cells divide they give rise to stem cells (by self-renewal) and progenitors (by differentiation). In most tissues only the primitive stem cells self-renew. Stem cell isolation and transplantation is the basis for regenerative medicine. In the 1990s, we isolated mouse and human hematopoietic (blood-forming) stem cells (HSCs), and found that their method of isolation depleted all detectable cancer cells from mobilized peripheral blood (MPB) from patients with breast cancer. We used patients' MPB or cancer-free HSCs in autologous transplantations to rescue the hematopoietic system of women who underwent high dose combination chemotherapy for stage IV breast cancer. The results with MPB autologous transplantation were similar to those reported previously, with a 12-15-year overall survival rate of ∼7%. In contrast, for contemporaneous patients in a small phase I/II trial at Stanford who received autologous transplants with cancer-free HSCs, this survival rate was ∼33%. By chi-square analysis, MPB vs. cancer-free HSC transplantations were significantly different in terms of both progression-free and overall survival at all time points tested from 20 months to 12-15 years after transplantation. In considering stem cells and cancer, self-renewal is dangerous and therefore strictly regulated. Poorly regulated self-renewal can lead to the genesis of cancer stem cells, the only self-renewing cells in the cancerous tumor. We have followed the progression from HSCs to myelogenous leukemias and found that the developing cancer clones progress at the stage of HSCs, until they become fully malignant. At this point, the “leukemia” stem cell moves to a stage of a downstream oligolineage or multilineage progenitor that has evaded programmed cell death and programmed cell removal, while acquiring or keeping self-renewal. In the case of chronic myeloid leukemia, bcr-abl+ HSC clones outcompete normal HSCs in the chronic phase. The transition from the chronic phase to myeloid blast crisis results in the leukemia stem cells appearing in the granulocyte-macrophage progenitor (GMP) stage, and is accompanied by cell intrinsic activation of β-catenin, inhibitable by transfection with axin. In 4 of 7 patients studied, this resulted from stage-specific (GMP) mis-splicing of the glycogen synthase kinase-3β message, deleting the kinase domain. With the Majeti and Quake labs, we have shown that the mutations/indels (insertions or deletions) in 5 FLT3-ITD (internal tandem duplication) acute myeloid leukemias (AMLs) occur successively in HSC clones, including the penultimate FLT3-ITD itself. Of interest, many of the founder mutations are in epigenetic modifier genes such as TET2. While there are many ways to defeat programmed cell death and senescence, there appears to be one dominant method to avoid programmed cell removal_the expression of the cell surface “don't eat me” protein CD47, the ligand for macrophage SIRPα. All cancers we tested express CD47 to overcome expression of “eat me” signals such as calreticulin. In leukemias and lymphomas, calreticulin is the “eat me” signal countermanded by the CD47 “don't eat me” signal. In myelodysplastic syndrome (MDS), we found that MDS-initiating HSC clones outcompete normal HSC clones in the patient and in mice that receive xenotransplants of patient HSC samples. However, the oligolineage progenitors downstream of HSCs (e.g., GMPs) express calreticulin but not CD47, leading to our hypothesis that the blood-cell deficiencies in MDS occur because the progenitors are phagocytosed in vivo. When CD47 is upregulated in the MDS clone, MDS progresses to refractive anemia with excess blasts or AML. Other labs have also found mutations in the calreticulin gene in myeloproliferative neoplasms and MDS. Antibodies that block the CD47-SIRPα interaction enable phagocytosis and killing of the tumor cells in vitro and in vivo. All tested human solid tumors and lymphomas/leukemias/myelomas express CD47 and are susceptible to phagocytosis in the presence of anti-CD47 blocking antibodies, including a humanized antibody of the IgG4 isotype. We expect to have the anti-CD47 therapies in phase I trials in 2014. Citation Format: Irving L. Weissman. Investigating inhibition of the CD47 “don't eat me” signal to enable tumor phagocytic removal and augmented cross presentation to T cells. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr PL02-02. doi:10.1158/1538-7445.AM2014-PL02-02

Proliferation and enrichment of CD133+ glioblastoma cancer stem cells on 3D chitosan-alginate scaffolds

Emerging evidence implicates cancer stem cells (CSCs) as primary determinants of the clinical behavior of human cancers, representing an ideal target for next-generation anti-cancer therapies. However CSCs are difficult to propagate in vitro, severely limiting the study of CSC biology and drug development. Here we report that growing cells from glioblastoma (GBM) cell lines on three dimensional (3D) porous chitosan-alginate (CA) scaffolds dramatically promotes the proliferation and enrichment of cells possessing the hallmarks of CSCs. CA scaffold-grown cells were found more tumorigenic in nude mouse xenografts than cells grown from monolayers. Growing in CA scaffolds rapidly promoted expression of genes involved in the epithelial-to-mesenchymal transition that has been implicated in the genesis of CSCs. Our results indicate that CA scaffolds have utility as a simple and inexpensive means to cultivate CSCs in vitro in support of studies to understand CSC biology and develop more effective anti-cancer therapies.

Regulated Splicing of the α6 Integrin Cytoplasmic Domain Determines the Fate of Breast Cancer Stem Cells

Although the α6β1 integrin has been implicated in thefunction of breast and other cancer stem cells (CSCs), little is known about its regulation and relationship to mechanisms involved in the genesis of CSCs. We report that a CD44(high)/CD24(low) population, enriched for CSCs, is comprised of distinct epithelial and mesenchymal populations that differ in expression of the two α6 cytoplasmic domain splice variants: α6A and α6B. α6Bβ1 expression defines the mesenchymal population and is necessary for CSC function, a function that cannot be executed by α6Aintegrins. The generation of α6Bβ1 is tightly controlled and occurs as a consequence of an autocrine vascular endothelial growth factor (VEGF) signaling that culminates in the transcriptional repression of a key RNA-splicing factor. These data alter our understanding of how α6β1 contributes tobreast cancer, and they resolve ambiguities regarding the use of total α6 (CD49f) expression as a biomarker for CSCs.

Decoding the Knots of Initiation of Oncogenic Epithelial-Mesenchymal Transition in Tumor Progression

Oncogenic epithelial-mesenchymal transition (oncEMT) plays important roles in the genesis of cancer stem cells (CSCs), malignant tumor initiation and progression, cancer metastasis, and drug resistance. Although the role of oncEMT in tumorigenesis has recently been extensively studied, the initiation of oncEMT is not clearly understood, and its mechanisms of action are still unknown. Emerging evidence suggests that oncEMT is a complex process, which involves multiple endogenous and exogenous factors. Overexpression of several oncogenes and reprogramming factors in precancerous and cancerous cells, including Ras, Myc, Bmi-1, Oct4, Nanog, Slug, Twist, Zeb1, and Zeb2, may initiate oncEMT and tumorigenesis. Defects in key tumor suppressors, such as p53, PTEN, CCN6 protein, and p21 also are associated with oncEMT. MicroRNA (miRNA) may also play a role in the oncEMT. Furthermore, exogenous factors, including chemical carcinogens, viruses, radiation, hypoxia, and acidic microenvironment, can drive oncEMT. Moreover, various growth factors derived from either malignant tumor cells or tumor-associated non-tumor cells in the cancer microenvironment can promote oncEMT. Together, the endogenous and exogenous factors, as well as a hostile cancer microenvironment, initiate the oncEMT program through diverse signaling pathways and networks. However, the dynamic process of initiating oncEMT and the mechanisms are still incompletely understood. Further characterization of the dynamics and mechanisms of the oncEMT will provide new insights into oncogenesis, as well as identify specific oncEMT markers and targets for early diagnosis of cancer and novel anti-cancer drug discovery.

Ovarian and Breast Cancer Spheres Are Similar in Transcriptomic Features and Sensitive to Fenretinide

Cancer stem cells (CSCs) are resistant to chemotherapy and are ability to regenerate cancer cell populations, thus attracting much attention in cancer research. In this report, we first demonstrated that sphere cells from ovarian cancer cell line A2780 shared many features of CSCs, such as resistance to cisplatin and able to initiate tumors in an efficient manner. Then, we conducted cDNA microarray analysis on spheres from ovarian A2780 cells, and from breast MCF7 and SUM159 cells, and found that molecular pathways underlying spheres from these cancer cell lines were similar to a large extent, suggesting that similar mechanisms are involved in the genesis of CSCs in both ovarian and breast cancer types. In addition, we showed that spheres from these cancer types were highly sensitive to fenretinide, a stimulus of oxidative stress-mediated apoptosis in cancer cells. Thus, our results not only provide important insights into mechanisms underlying CSCs in ovarian and breast cancer, but also lead to the development of more sophisticated protocols of cancer therapy in near future.

Expression and Functional Role of ALDH1 in Cervical Carcinoma Cells

Tumor formation and growth is dictated by a very small number of tumor cells, called cancer stem cells, which are capable of self-renewal. The genesis of cancer stem cells and their resistance to conventional chemotherapy and radiotherapy via mechanisms such as multidrug resistance, quiescence, enhanced DNA repair abilities and anti-apoptotic mechanisms, make it imperative to develop methods to identify and use these cells as diagnostic or therapeutic targets. Aldehyde dehydrogenase 1 (ALDH1) is used as a cancer stem cell marker. In this study, we evaluated ALDH1 expression in CaSki, HeLa and SiHa cervical cancer cells using the Aldefluor method to isolate ALDH1-positive cells. We showed that higher ALDH1 expression correlated with significantly higher rates of cell proliferation, microsphere formation and migration. We also could demonstrate that SiHa-ALDH1- positive cells were significantly more tumorigenic compared to SiHa-ALDH1-negative cells. Similarly, SiHa cells overexpressing ALDH1 were significantly more tumorigenic and showed higher rates of cell proliferation and migration compared to SiHa cells where ALDH1 expression was knocked down using a lentivirus vector. Our data suggested that ALDH1 is a marker of cervical cancer stem cells and expand our understanding of its functional role.

Normal & neoplastic stem cell (ML15)

Following embryonic development, most of our tissues and organs are continuously regenerated from tissue/organ specific stem cells. The principal property that distinguishes such stem cells from their daughter cells is self-renewal; when stem cells divide they give rise to stem cells (by self-renewal) and progenitors (by differentiation). In most tissues only the primitive stem cells self-renew. Stem cell isolation and transplantation is the basis for regenerative medicine. Self-renewal is dangerous, and therefore strictly regulated. Poorly regulated self-renewal can lead to the genesis of cancer stem cells, the only self-renewing cells in the cancerous tumor.