CAMTA1 is a novel tumour suppressor regulated by miR-9/9* in glioblastoma stem cells

Cancer stem cells or cancer initiating cells are believed to contribute to cancer recurrence after therapy. MicroRNAs (miRNAs) are short RNA molecules with fundamental roles in gene regulation. The role of miRNAs in cancer stem cells is only poorly understood. Here, we report miRNA expression profiles of glioblastoma stem cell-containing CD133(+) cell populations. We find that miR-9, miR-9(*) (referred to as miR-9/9(*)), miR-17 and miR-106b are highly abundant in CD133(+) cells. Furthermore, inhibition of miR-9/9(*) or miR-17 leads to reduced neurosphere formation and stimulates cell differentiation. Calmodulin-binding transcription activator 1 (CAMTA1) is a putative transcription factor, which induces the expression of the anti-proliferative cardiac hormone natriuretic peptide A (NPPA). We identify CAMTA1 as an miR-9/9(*) and miR-17 target. CAMTA1 expression leads to reduced neurosphere formation and tumour growth in nude mice, suggesting that CAMTA1 can function as tumour suppressor. Consistently, CAMTA1 and NPPA expression correlate with patient survival. Our findings could provide a basis for novel strategies of glioblastoma therapy.

Tumor induced inactivation of natural killer cell cytotoxic function; implication in growth, expansion and differentiation of cancer stem cells

Accumulated evidence indicates that cytotoxic function of immune effectors is largely suppressed in the tumor microenvironment by a number of distinct effectors and their secreted factors. The aims of this review are to provide a rationale and a potential mechanism for immunosuppression in cancer and to demonstrate the significance of such immunosuppression in cellular differentiation and progression of cancer. To that end, we have recently shown that NK cells mediate significant cytotoxicity against primary oral squamous carcinoma stem cells (OSCSCs) as compared to their more differentiated oral squamous carcinoma cells (OSCCs). In addition, human embryonic stem cells (hESCs), Mesenchymal Stem Cells (hMSCs), dental pulp stem cells (hDPSCs) and induced pluripotent stem cells (hiPSCs) were all significantly more susceptible to NK cell mediated cytotoxicity than their differentiated counterparts or parental cells from which they were derived. We have also reported that inhibition of differentiation or reversion of cells to a less-differentiated phenotype by blocking NFκB or targeted knock down of COX2 in primary monocytes in vivo significantly augmented NK cell function. Total population of monocytes and those depleted of CD16(+) subsets were able to substantially prevent NK cell mediated lysis of OSCSCs, MSCs and DPSCs. Taken together, our results suggest that stem cells are significant targets of the NK cell cytotoxicity. The concept of split anergy in NK cells and its contribution to tissue repair and regeneration and in tumor resistance and progression will be discussed in this review.

Progesterone and estrogen receptor expression and activity in human non-small cell lung cancer

Lung cancer is the most common cause of cancer mortality in male and female patients in the US. Although it is clear that tobacco smoking is a major cause of lung cancer, about half of all women with lung cancer worldwide are never-smokers. Despite a declining smoking population, the incidence of non-small cell lung cancer (NSCLC), the predominant form of lung cancer, has reached epidemic proportions particularly in women. Emerging data suggest that factors other than tobacco, namely endogenous and exogenous female sex hormones, have a role in stimulating NSCLC progression. Aromatase, a key enzyme for estrogen biosynthesis, is expressed in NSCLC. Clinical data show that women with high levels of tumor aromatase (and high intratumoral estrogen) have worse survival than those with low aromatase. The present and previous studies also reveal significant expression and activity of estrogen receptors (ERα, ERβ) in both extranuclear and nuclear sites in most NSCLC. We now report further on the expression of progesterone receptor (PR) transcripts and protein in NSCLC. PR transcripts were significantly lower in cancerous as compared to non-malignant tissue. Using immunohistochemistry, expression of PR was observed in the nucleus and/or extranuclear compartments in the majority of human tumor specimens examined. Combinations of estrogen and progestins administered in vitro cooperate in promoting tumor secretion of vascular endothelial growth factor and, consequently, support tumor-associated angiogenesis. Further, dual treatment with estradiol and progestin increased the numbers of putative tumor stem/progenitor cells. Thus, ER- and/or PR-targeted therapies may offer new approaches to manage NSCLC.

Immunotherapy of prostate cancer: should we be targeting stem cells and EMT?

Cancer stem cells have been implicated in a number of solid malignancies including prostate cancer. In the case of localised prostate cancer, patients are often treated with surgery (radical prostatectomy) and/or radiotherapy. However, disease recurrence is an issue in about 30% of patients, who will then go on to receive hormone ablation therapy. Hormone ablation therapy is often palliative in a vast proportion of individuals, and for hormone-refractory patients, there are several immunotherapies targeting a number of prostate tumour antigens which are currently in development. However, clinical responses in this setting are inconsistent, and it is believed that the failure to achieve full and permanent tumour eradication is due to a small, resistant population of cells known as 'cancer stem cells' (CSCs). The stochastic and clonal evolution models are among several models used to describe cancer development. The general consensus is that cancer may arise in any cell as a result of genetic mutations in oncogenes and tumour suppressor genes, which consequently result in uncontrolled cell growth. The cancer stem cell theory, however, challenges previous opinion and proposes that like normal tissues, tumours are hierarchical and only the rare subpopulation of cells at the top of the hierarchy possess the biological properties required to initiate tumourigenesis. Furthermore, where most cancer models infer that every cell within a tumour is equally malignant, i.e. equally capable of reconstituting new tumours, the cancer stem cell theory suggests that only the rare cancer stem cell component possess tumour-initiating capabilities. Hence, according to this model, cancer stem cells are implicated in both tumour initiation and progression. In recent years, the role of epithelial--mesenchymal transition (EMT) in the advancement of prostate cancer has become apparent. Therefore, CSCs and EMT are both likely to play critical roles in prostate cancer tumourigenesis. This review summarises the current immunotherapeutic strategies targeting prostate tumour antigens taking into account the need to consider treatments that target cancer stem cells and cells involved in epithelial--mesenchymal transition.

Expression of nodal and nodal receptors in prostate stem cells and prostate cancer cells: autocrine effects on cell proliferation and migration

BACKGROUND

Nodal, a TGFβ like growth factor, functions as an embryonic morphogen that maintains the pluripotency of embryonic stem cells. Nodal has been implicated in cancer progression; however, there is no information on expression and functions of Nodal in prostate cancer. In this study, we have investigated the expression of Nodal, its receptors, and its effects on proliferation and migration of human prostate cells.

METHODS

RT-PCR, qPCR, and Western blot analyses were performed to analyze expression of Nodal and Nodal receptors and its effects on phosphorylation of Smad2/3 in prostate cells. The effects on proliferation and migration were determined by (3) H-Thymidine incorporation and cell migration assays in the presence or absence of Nodal receptor inhibitor (SB431542).

RESULTS

Nodal was highly expressed in WPE, DU145, LNCaP, and LNCaP-C81 cells with low expression in RWPE1 and RWPE2 cells, but not in PREC, PC3 and PC3M cells. Nodal receptors are expressed at varying levels in all prostate cells. Treatment with exogenous Nodal induced phosphorylation of Smad2/3 in WPE, DU145, and PC3 cells, which was blocked by SB431542. Nodal dose-dependently inhibited proliferation of WPE, RWPE1 and DU145 cells, but not LNCaP and PC3 cells. Nodal induced cell migration in PC3 cells, which was inhibited by SB431542; Nodal had no effect on cell migration in WPE and DU145 cells. The effects of Nodal on cell proliferation and migration are mediated via ALK4 and ActRII/ActRIIB receptors and Smad 2/3 phosphorylation.

CONCLUSIONS

Nodal may function as an autocrine regulator of proliferation and migration of prostate cancer cells.

Therapeutic targeting of cancer stem cells

Recent breakthroughs in translational oncology are opening new perspectives for the treatment of cancer. The advent of targeted therapies has provided the proof-of-concept to selectively turn-off deregulated oncogenic proteins, while the identification and validation of predictive biomarkers of response has allowed to improve, at least in some cases, their performance. Moreover, a subpopulation of tumor-propagating cells has been identified from many solid and hematological tumors. These cells share functional properties of normal stem cells, and are commonly referred to as cancer stem cells (CSCs). It is emerging that CSCs are defended against broadly used anticancer agents by means of different, partly interconnected, mechanisms. However, CSCs rely on specific pathways involved in self-renewal that can be pharmacologically antagonized by experimental molecular targeted agents, some of which have recently entered early phases of clinical development. Here, we discuss the spectrum of pharmacological strategies under clinical or preclinical development for CSCs targeting.

The human DEK oncogene stimulates β-catenin signaling, invasion and mammosphere formation in breast cancer

Breast cancer is a major cause of cancer-related deaths in American women; therefore, the identification of novel breast cancer-related molecules for the discovery of new markers and drug targets remains essential. The human DEK gene, which encodes a chromatin-binding protein and DNA topology regulator, is upregulated in many types of cancer. DEK has been implicated as an oncogene in breast cancer based on mRNA expression studies, but its functional significance in breast cancer growth and progression has not yet been tested directly. We demonstrate that DEK is highly expressed in breast cancer cells compared with normal tissue, and functionally important for cellular growth, invasion and mammosphere formation. DEK overexpression in non-tumorigenic MCF10A cells resulted in increased growth and motility, with a concomitant downregulation of E-cadherin. Conversely, DEK knockdown in MCF7 and MDA-MB-468 breast cancer cells resulted in decreased growth and motility with upregulation of E-cadherin. The use of DEK-proficient and -deficient breast cancer cells in orthotopic xenografts provided further in vivo evidence that DEK contributes to tumor growth. Activation of the β-catenin signaling pathway is important for normal and cancer stem cell character, growth and metastasis. We show that DEK expression stimulated, and DEK knockdown repressed β-catenin nuclear translocation and activity. Importantly, the expression of constitutively active β-catenin rescued breast cancer invasion defects of DEK knockdown cells. Together, our data indicate that DEK expression stimulates the growth, stem cell character and motility of breast cancer cells, and that DEK-dependent cellular invasion occurs at least in part via β-catenin activation.

Matrix stiffness modulates proliferation, chemotherapeutic response, and dormancy in hepatocellular carcinoma cells

There is increasing evidence that the physical environment is a critical mediator of tumor behavior. Hepatocellular carcinoma (HCC) develops within an altered biomechanical environment, and increasing matrix stiffness is a strong predictor of HCC development. The aim of this study was to establish whether changes in matrix stiffness, which are characteristic of inflammation and fibrosis, regulate HCC cell proliferation and chemotherapeutic response. Using an in vitro system of "mechanically tunable" matrix-coated polyacrylamide gels, matrix stiffness was modeled across a pathophysiologically relevant range, corresponding to values encountered in normal and fibrotic livers. Increasing matrix stiffness was found to promote HCC cell proliferation. The proliferative index (assessed by Ki67 staining) of Huh7 and HepG2 cells was 2.7-fold and 12.2-fold higher, respectively, when the cells were cultured on stiff (12 kPa) versus soft (1 kPa) supports. This was associated with stiffness-dependent regulation of basal and hepatocyte growth factor-stimulated mitogenic signaling through extracellular signal-regulated kinase, protein kinase B (PKB/Akt), and signal transducer and activator of transcription 3. β1-Integrin and focal adhesion kinase were found to modulate stiffness-dependent HCC cell proliferation. Following treatment with cisplatin, we observed reduced apoptosis in HCC cells cultured on stiff versus soft (physiological) supports. Interestingly, however, surviving cells from soft supports had significantly higher clonogenic capacity than surviving cells from a stiff microenvironment. This was associated with enhanced expression of cancer stem cell markers, including clusters of differentiation 44 (CD44), CD133, c-kit, cysteine-X-cysteine receptor 4, octamer-4 (CXCR4), and NANOG.

CONCLUSION

Increasing matrix stiffness promotes proliferation and chemotherapeutic resistance, whereas a soft environment induces reversible cellular dormancy and stem cell characteristics in HCC. This has implications for both the treatment of primary HCC and the prevention of tumor outgrowth from disseminated tumor cells. (HEPATOLOGY 2011;).

Advances in ovarian cancer screening: health and medicine for women: a multidisciplinary, evidence-based review of mid-life health concerns

Early detection is imperative for improving survival from ovarian cancer, the leading cause of death from gynecological cancer in the United States. At the Health and Medicine for Women continuing medical education (CME) conference at Yale in September 2010, Dr. Gil Mor, a researcher in the Department of OB/GYN at Yale, presented recent advances on the pathophysiology of ovarian cancer. These advances, and particularly our growing understanding of cancer stem cells, may help overcome the limitations of current ovarian cancer detection and treatment methods.

Association of TP53 mutations with stem cell-like gene expression and survival of patients with hepatocellular carcinoma

BACKGROUND & AIMS

Mutations in TP53, a tumor suppressor gene, are associated with prognosis of many cancers. However, the prognostic values of TP53 mutation sites are not known for patients with hepatocellular carcinoma (HCC) because of heterogeneity in their geographic and etiologic backgrounds.

METHODS

TP53 mutations were investigated in a total of 409 HCC patients, including Chinese (n = 336) and white (n = 73) patients, using the direct sequencing method.

RESULTS

A total of 125 TP53 mutations were found in Chinese patients with HCC (37.2%). HCC patients with TP53 mutations had a shorter overall survival time compared with patients with wild-type TP53 (hazard ratio [HR], 1.86; 95% confidence interval [CI]: 1.37-2.52; P < .001). The hot spot mutations R249S and V157F were significantly associated with worse prognosis in univariate (HR, 2.11; 95% CI: 1.51-2.94; P < .001) and multivariate analyses (HR, 1.79; 95% CI: 1.29-2.51; P < .001). Gene expression analysis revealed the existence of stem cell-like traits in tumors with TP53 mutations. These findings were validated in breast and lung tumor samples with TP53 mutations.

CONCLUSIONS

TP53 mutations, particularly the hot spot mutations R249S and V157F, are associated with poor prognosis for patients with HCC. The acquisition of stem cell-like gene expression traits might contribute to the aggressive behavior of tumors with TP53 mutation.

High-throughput lectin microarray-based analysis of live cell surface glycosylation

Lectins, plant-derived glycan-binding proteins, have long been used to detect glycans on cell surfaces. However, the techniques used to characterize serum or cells have largely been limited to mass spectrometry, blots, flow cytometry, and immunohistochemistry. While these lectin-based approaches are well established and they can discriminate a limited number of sugar isomers by concurrently using a limited number of lectins, they are not amenable for adaptation to a high-throughput platform. Fortunately, given the commercial availability of lectins with a variety of glycan specificities, lectins can be printed on a glass substrate in a microarray format to profile accessible cell-surface glycans. This method is an inviting alternative for analysis of a broad range of glycans in a high-throughput fashion and has been demonstrated to be a feasible method of identifying binding-accessible cell surface glycosylation on living cells. The current unit presents a lectin-based microarray approach for analyzing cell surface glycosylation in a high-throughput fashion.

Infection, stem cells and cancer signals

The association of cancer with preceding parasitic infections has been observed for over 200 years. Some such cancers arise from infection of tissue stem cells by viruses with insertion of viral oncogenes into the host DNA (mouse polyoma virus, mouse mammary tumor virus). In other cases the virus does not insert its DNA into the host cells, but rather commandeers the metabolism of the infected cells, so that the cells continue to proliferate and do not differentiate (human papilloma virus and cervical cancer). Cytoplasmic Epstein Barr virus infection is associated with a specific gene translocation (Ig/c-myc) that activates proliferation of affected cells (Burkitt lymphoma). In chronic osteomyelitis an inflammatory reaction to the infection appears to act through production of inflammatory cytokines and oxygen radical formation to induce epithelial cancers. Infection with Helicobacter pylori leads to epigenetic changes in methylation and infection by a parasite. Clonorchis sinensis also acts as a promoter of cancer of the bile ducts of the liver (cholaniocarcinoma). The common thread among these diverse pathways is that the infections act to alter tissue stem cell signaling with continued proliferation of tumor transit amplifying cells.

Administration of embryonic stem cells generates effective antitumor immunity in mice with minor and heavy tumor load

The history of immunizing animals with fetal tissues to generate an antitumor response dates back a century ago. Subsequent reports supported the idea that vaccination with embryonic materials could generate cancer-specific immunity and protect animals from transplantable and chemically induced tumors. In our study, we found C57 BL/6 mice vaccinated with embryonic stem cells (ESCs) received obvious antitumor immunity, which protected them from the formation and development of lung cancer. Furthermore, we investigated the antitumor effects of administration of ESCs in mice with minor and/or heavy tumor load. The tumor growth was monitored, the proliferation of lymphocytes and secretion of cytokines were examined, and finally the tissue sections were approached by immunohistochemical and apoptosis staining. The results suggested that mice injected with ESCs received obvious tumor inhibition and retardation due to significant lymphocyte proliferation and cytokine secretion, which help to rebuild the host's immunity against cancer to some extent and comprise the main part of antitumor immunity. Moreover, mice with minor tumor load received stronger antitumor effect compared with mice with heavy tumor load, may be due to relatively intact immune system. Thus, besides their function as prophylactic vaccines, administration of ESCs could be a potential treatment for cancer, which obviously prevent and control the proliferation and development of malignant tumors.

Glioma cancer stem cells induce immunosuppressive macrophages/microglia

Macrophages (MΦs)/microglia that constitute the dominant tumor-infiltrating immune cells in glioblastoma are recruited by tumor-secreted factors and are induced to become immunosuppressive and tumor supportive (M2). Glioma cancer stem cells (gCSCs) have been shown to suppress adaptive immunity, but their role in innate immunity with respect to the recruitment and polarization of MΦs/microglia is unknown. The innate immunosuppressive properties of the gCSCs were characterized based on elaborated MΦ inhibitory cytokine-1 (MIC-1), transforming growth factor (TGF-β1), soluble colony-stimulating factor (sCSF), recruitment of monocytes, inhibition of MΦ/microglia phagocytosis, induction of MΦ/microglia cytokine secretion, and the inhibition of T-cell proliferation. The role of the signal transducer and activator of transcription 3 (STAT3) in mediating innate immune suppression was evaluated in the context of the functional assays. The gCSCs produced sCSF-1, TGF-β1, and MIC-1, cytokines known to recruit and polarize the MΦs/microglia to become immunosuppressive. The gCSC-conditioned medium polarized the MΦ/microglia to an M2 phenotype, inhibited MΦ/microglia phagocytosis, induced the secretion of the immunosuppressive cytokines interleukin-10 (IL-10) and TGF-β1 by the MΦs/microglia, and enhanced the capacity of MΦs/microglia to inhibit T-cell proliferation. The inhibition of phagocytosis and the secretion of IL-10 were reversed when the STAT3 pathway was blocked in the gCSCs. The gCSCs modulate innate immunity in glioblastoma by inducing immunosuppressive MΦs/microglia, and this capacity can be reversed by inhibiting phosphorylated STAT3.

Lung cancer therapeutics that target signaling pathways: an update

Claiming more than 150,000 lives each year, lung cancer is the deadliest cancer in the USA. First-line treatments in lung cancer include surgical resection and chemotherapy, the latter of which offers only modest survival benefits at the expense of often severe and debilitating side effects. Recent advances in elucidating the molecular biology of lung carcinogenesis have elucidated novel drug targets, and treatments are rapidly evolving into specialized agents that hone in on specific aspects of the disease. Of particular interest is blocking tumor growth by targeting the physiological processes surrounding angiogenesis, pro-tumorigenic growth factor activation, anti-apoptotic cascades and other cancer-promoting signal transduction events. This article looks at several areas of interest to lung cancer therapeutics and considers the current state of affairs surrounding the development of these therapies.

Harnessing the cell death pathway for targeted cancer treatment

Genotoxic agents have long targeted apoptotic cell death as a primary means of treating cancer. However, the presence of cellular defects in many cancers has contributed to an acquired resistance to apoptotic cell death, lowering the effectiveness of chemo- and radiotherapies. The mechanisms by which cells achieve this resistance to treatment are still being investigated, but an alternative approach is the study of cell death pathways that are mechanistically distinct from apoptosis. These pathways, including autophagy and necrosis, have arisen as attractive targets for cancer therapy. This review will discuss apoptosis, autophagy, and necrosis in the context of tumorigenesis and drug resistance, as well as provide an up-to-date preclinical and clinical review of inhibitors targeting these cell death pathways for multiple cancer types. The goal of these studies is to identify molecular targets that will enhance the efficacy and specificity of current cancer therapies.

Perspective beyond cancer genomics: bioenergetics of cancer stem cells

Although the notion that cancer is a disease caused by genetic and epigenetic alterations is now widely accepted, perhaps more emphasis has been given to the fact that cancer is a genetic disease. It should be noted that in the post-genome sequencing project period of the 21st century, the underlined phenomenon nevertheless could not be discarded towards the complete control of cancer disaster as the whole strategy, and in depth investigation of the factors associated with tumorigenesis is required for achieving it. Otto Warburg has won a Nobel Prize in 1931 for the discovery of tumor bioenergetics, which is now commonly used as the basis of positron emission tomography (PET), a highly sensitive noninvasive technique used in cancer diagnosis. Furthermore, the importance of the cancer stem cell (CSC) hypothesis in therapy-related resistance and metastasis has been recognized during the past 2 decades. Accumulating evidence suggests that tumor bioenergetics plays a critical role in CSC regulation; this finding has opened up a new era of cancer medicine, which goes beyond cancer genomics.

Epigenetic regulation of cancer stem cells in liver cancer: current concepts and clinical implications

The two dominant models of carcinogenesis postulate stochastic (clonal evolution) or hierarchic organization of tumor (cancer stem cell model). According to the latter, at the germinal center of tumor evolution is a cancer stem cell (CSC) which, similar to normal adult stem cells, possesses the capacity of self-renewal and a differentiation potential. Over the past few years, compelling evidence has emerged in support of the hierarchic cancer model for many solid tumors including hepatocellular cancers. The CSCs are posited to be responsible not only for tumor initiation but also for the generation of distant metastasis and relapse after therapy. These characteristics are particularly relevant for a multi-resistant tumor entity like human hepatocellular carcinoma and may herald a paradigm shift in the management of this deadly disease. Identification and detailed characterization of liver CSCs is therefore imperative for improving prevention approaches, enhancing early detection, and extending the limited treatment options. Despite the current progress in understanding the contribution of CSCs to the generation of heterogeneity of tumors, the molecular complexity and exact regulation of CSCs is poorly understood. This review focuses on the genetic and epigenetic mechanisms that regulate and define the unique CSC properties with an emphasis on key regulatory pathways of liver CSCs and their clinical significance.

Targeting miRNAs involved in cancer stem cell and EMT regulation: An emerging concept in overcoming drug resistance

Although chemotherapy is an important therapeutic strategy for cancer treatment, it fails to eliminate all tumor cells due to intrinsic or acquired drug resistance, which is the most common cause of tumor recurrence. Emerging evidence suggests an intricate role of cancer stem cells (CSCs) and epithelial-mesenchymal transition (EMT)-type cells in anticancer drug resistance. Recent studies also demonstrated that microRNAs (miRNAs) play critical roles in the regulation of drug resistance. Here we will discuss current knowledge regarding CSCs, EMT and the role of regulation by miRNAs in the context of drug resistance, tumor recurrence and metastasis. A better understanding of the molecular intricacies of drug-resistant cells will help to design novel therapeutic strategies by selective targeting of CSCs and EMT-phenotypic cells through alterations in the expression of specific miRNAs towards eradicating tumor recurrence and metastasis. A particular promising lead is the potential synergistic combination of natural compounds that affect critical miRNAs, such as curcumin or epigallocatechin-3-gallate (EGCG) with chemotherapeutic agents.

Decreasing glioma recurrence through adjuvant cancer stem cell inhibition

Gliomas remain one of the most challenging solid organ tumors to treat and are marked clinically by invariable recurrence despite multimodal intervention (surgery, chemotherapy, radiation). This recurrence perhaps, is as a consequence of the failure to eradicate a tumor cell subpopulation, termed cancer stem cells. Isolating, characterizing, and understanding these tumor-initiating cells through cellular and molecular markers, along with genetic and epigenetic understanding will allow for selective targeting through therapeutic agents and holds promise for decreasing glioma recurrence.

NCI first International Workshop on the biology, prevention, and treatment of relapse after allogeneic hematopoietic stem cell transplantation: report from the committee on the biological considerations of hematological relapse following allogeneic stem cell transplantation unrelated to graft-versus-tumor effects: state of the science

Hematopoietic malignant relapse still remains the major cause of death following allogeneic hematopoietic stem cell transplantation (HSCT). Although there has been a large focus on the immunologic mechanisms responsible for the graft-versus-tumor (GVT) effect or lack thereof, there has been little attention paid to investigating the biologic basis of hematologic malignant disease relapse following allogeneic HSCT. There are a large number of factors that are responsible for the biologic resistance of hematopoietic tumors following allogeneic HSCT. We have focused on 5 major areas including clonal evolution of cancer drug resistance, cancer radiation resistance, genomic basis of leukemia resistance, cancer epigenetics, and resistant leukemia stem cells. We recommend increased funding to pursue 3 broad areas that will significantly enhance our understanding of the biologic basis of malignant relapse after allogeneic HSCT, including: (1) genomic and epigenetic alterations, (2) cancer stem cell biology, and (3) clonal cancer drug and radiation resistance.

Notch1 signaling is activated in cells expressing embryonic stem cell proteins in human primary nasopharyngeal carcinoma

OBJECTIVE

To explore the expression of Notch1 signaling pathway in nasopharyngeal carcinoma (NPC).

METHODS

We performed immunocytochemistry on surgically resected NPC using antibodies against embryonic stem (ES) cell proteins and against Notch1 signaling components.

RESULTS

We found that ES cell protein markers SOX2 and OCT4 were expressed in a subpopulation of cells for all three subtypes of NPC but barely in the normal control. Double immunostaining shows that SOX2- and OCT4-positive cells coexpressed proliferative markers, suggesting that human NPC may contain cancer stem-like cells. In addition, we found that Notch1 signaling was activated in NPC. Confocal images show that the Notch1 signaling activated form and Hes1, a downstream target of Notch1 signaling, was predominantly found in SOX2- and OCT4-positive cells.

CONCLUSION

Our findings suggest that the Notch1 signaling pathway might be a regulator of cancer stem-like cells in NPC.

Radiation resistance of cancer stem cells: the 4 R's of radiobiology revisited

There is compelling evidence that many solid cancers are organized hierarchically and contain a small population of cancer stem cells (CSCs). It seems reasonable to suggest that a cancer cure can be achieved only if this population is eliminated. Unfortunately, there is growing evidence that CSCs are inherently resistant to radiation, and perhaps other cancer therapies. In general, success or failure of standard clinical radiation treatment is determined by the 4 R's of radiobiology: repair of DNA damage, redistribution of cells in the cell cycle, repopulation, and reoxygenation of hypoxic tumor areas. We relate recent findings on CSCs to these four phenomena and discuss possible consequences.

CD133, Trop-2 and alpha2beta1 integrin surface receptors as markers of putative human prostate cancer stem cells

Cancer stem cells (CSCs) play a key role in initiation and development of cancer and are attractive targets for therapy. The identification of CSC surface receptors to be used as therapeutic targets in vivo remains a difficult task. In this study, we assessed the expression pattern of three surface receptors: CD133, Trop-2 and alpha2beta1 integrin in human prostate cancer in order to identify CSC-niches. CD133 was found to be expressed in small clusters of cells localized in focal areas of benign as well as malignant lesions, suggesting that this protein is a bona fide marker of the prostate stem/progenitor compartment. Trop-2 was localized in both basal and luminal layers of benign glands and was highly expressed in malignant lesions. Moreover, isolated cells in benign and malignant areas were found to co-express both CD133 and Trop-2. alpha2beta1 integrin was expressed in the prostatic epithelium as well as in the surrounding stroma, limiting its utility as a marker of CSCs. In summary, we demonstrate that the combination of CD133 and Trop-2 is useful to mark putative CSC-containing compartments in human prostate.

Challenges in the development of future treatments for breast cancer stem cells

The recurrence of tumors after years of disease-free survival has spurred interest in the concept that cancers may have a stem cell basis. Current speculation holds that as few as 0.1% of the tumor mass may be chemoresistant and radioresistant, harboring stem-like properties that drive tumor survival, development, and metastasis. There are intense investigations to characterize cancer stem cells on the basis of self-renewal and multi-lineage differentiation. Thus far, no successful targeted therapies have been developed and reached the clinic, but as these cells are isolated and characterized, insights may be unraveled. In this review, we discuss the controversy over the origins of the cancer stem cell hypothesis and the unforeseen factors that may facilitate breast cancer stem cell survival and metastasis. We discuss the role of tumor microenvironment, including carcinoma-associated fibroblasts, epigenetic factors, and the Th1/Th2 balance, in supporting breast cancer stem cells. In addition, we have incorporated ideas on the epithelial-to-mesenchymal transition in metastatic dissemination of epithelial malignancies. This area is relevant since breast cancer stem cells have been suggested to revert to a mesenchymal phenotype during the progression of cancer. Finally we discuss prospects of developing targeted therapy including novel treatment modalities such as oncolytic viral therapy, differentiation therapy, and nanotechnology.

Tumor initiation in human malignant melanoma and potential cancer therapies

Cancer stem cells (CSCs), also known as tumor-initiating cells, have been identified in several human malignancies, including human malignant melanoma. The frequency of malignant melanoma-initiating cells (MMICs), which are identified by their expression of ATP-binding cassette (ABC) family member ABCB5, correlates with disease progression in human patients. Furthermore, targeted MMIC ablation through ABCB5 inhibits tumor initiation and growth in preclinical xenotransplantation models, pointing to potential therapeutic promise of the CSC concept. Recent advances also show that CSCs can exert pro-angiogenic roles in tumor growth and serve immunomodulatory functions related to the evasion of host anti-tumor immunity. Thus, MMICs might initiate and sustain tumorigenic growth not only as a result of CSC-intrinsic self-renewal, differentiation and proliferative capacity, but also based on pro-tumorigenic interactions with the host environment.

Stem cells in hepatocarcinogenesis: evidence from genomic data

Increasing evidence suggests that many, perhaps all solid tumors contain a subset of cells that possess functional properties similar to the normal tissue stem cells, including self-renewal, unlimited proliferative capacity, and pluripotency. The hierarchical cancer model that places a cancer stem cell (CSC) population at the apex of tumor formation is based on this notion. The cancer stem cell hypothesis posits that CSCs are responsible not only for tumor initiation, but also generation of metastasis and local recurrence after therapy. Current definitions of the CSC are based only on functional properties regardless of potential cellular origin. Histopathology investigations of chronic liver diseases and experimental studies support the existence of CSCs in liver cancer. In particular, recent advances in microarray technologies utilizing integrative comparative genomic analysis of human hepatocellular carcinoma specimens, cancer cell lines, and transgenic models establish the molecular similarities between CSC and normal tissue stem cells and highlight the importance of CSC for the prognosis of liver cancer patients. The results have also uncovered the key "stemness" and oncogenic pathways frequently disrupted during hepatocarcinogenesis providing the basis for identifying novel therapeutic targets against CSC.

Defined factors induce reprogramming of gastrointestinal cancer cells

Although cancer is a disease with genetic and epigenetic origins, the possible effects of reprogramming by defined factors remain to be fully understood. We studied the effects of the induction or inhibition of cancer-related genes and immature status-related genes whose alterations have been reported in gastrointestinal cancer cells. Retroviral-mediated introduction of induced pluripotent stem (iPS) cell genes was necessary for inducing the expression of immature status-related proteins, including Nanog, Ssea4, Tra-1-60, and Tra-1-80 in esophageal, stomach, colorectal, liver, pancreatic, and cholangiocellular cancer cells. Induced cells, but not parental cells, possessed the potential to express morphological patterns of ectoderm, mesoderm, and endoderm, which was supported by epigenetic studies, indicating methylation of DNA strands and the histone H3 protein at lysine 4 in promoter regions of pluripotency-associated genes such as NANOG. In in vitro analysis induced cells showed slow proliferation and were sensitized to differentiation-inducing treatment, and in vivo tumorigenesis was reduced in NOD/SCID mice. This study demonstrated that pluripotency was manifested in induced cells, and that the induced pluripotent cancer (iPC) cells were distinct from natural cancer cells with regard to their sensitivity to differentiation-inducing treatment. Retroviral-mediated introduction of iPC cells confers higher sensitivity to chemotherapeutic agents and differentiation-inducing treatment.

Arsenic exposure transforms human epithelial stem/progenitor cells into a cancer stem-like phenotype

BACKGROUND

Inorganic arsenic is a ubiquitous environmental carcinogen affecting millions of people worldwide. Evolving theory predicts that normal stem cells (NSCs) are transformed into cancer stem cells (CSCs) that then drive oncogenesis. In humans, arsenic is carcinogenic in the urogenital system (UGS), including the bladder and potentially the prostate, whereas in mice arsenic induces multi-organ UGS cancers, indicating that UGS NSCs may represent targets for carcino-genic initiation. However, proof of emergence of CSCs induced by arsenic in a stem cell population is not available.

METHODS

We continuously exposed the human prostate epithelial stem/progenitor cell line WPE-stem to an environmentally relevant level of arsenic (5 microM) in vitro and determined the acquired cancer phenotype.

RESULTS

WPE-stem cells rapidly acquired a malignant CSC-like phenotype by 18 weeks of exposure, becoming highly invasive, losing contact inhibition, and hyper-secreting matrix metalloproteinase-9. When hetero-transplanted, these cells (designated As-CSC) formed highly pleomorphic, aggressive tumors with immature epithelial- and mesenchymal-like cells, suggesting a highly pluripotent cell of origin. Consistent with tumor-derived CSCs, As-CSCs formed abundant free-floating spheres enriched in CSC-like cells, as confirmed by molecular analysis and the fact that only these floating cells formed xeno-graft tumors. An early loss of NSC self-renewal gene expression (p63, ABCG2, BMI-1, SHH, OCT-4, NOTCH-1) during arsenite exposure was sub-sequently reversed as the tumor suppressor gene PTEN was progressively suppressed and the CSC-like phenotype acquired.

CONCLUSIONS

Arsenite transforms prostate epithelial stem/progenitor cells into CSC-like cells, indicating that it can produce CSCs from a model NSC population.

Nanotechnology-based molecular photoacoustic and photothermal flow cytometry platform for in-vivo detection and killing of circulating cancer stem cells

In-vivo multicolor photoacoustic (PA) flow cytometry for ultrasensitive molecular detection of the CD44+ circulating tumor cells (CTCs) is demonstrated on a mouse model of human breast cancer. Targeting of CTCs with stem-like phenotype, which are naturally shed from parent tumors, was performed with functionalized gold and magnetic nanoparticles. Results in vivo were verified in vitro with a multifunctional microscope, which integrates PA, photothermal (PT), fluorescent and transmission modules. Magnet-induced clustering of magnetic nanoparticles in individual cells significantly amplified PT and PA signals. The novel noninvasive platform, which integrates multispectral PA detection and PT therapy with a potential for multiplex targeting of many cancer biomarkers using multicolor nanoparticles, may prospectively solve grand challenges in cancer research for diagnosis and purging of undetectable yet tumor-initiating cells in circulation before they form metastasis.

Effects of the sesquiterpene lactone parthenolide on prostate tumor-initiating cells: An integrated molecular profiling approach

Recent evidence suggests tumor-initating cells (TICs), also called cancer stem cells, are responsible for tumor initiation and progression; therefore, they represent an important cell population for development of future anti-cancer therapies. In this study, we show that the sesquiterpene lactone parthenolide (PTL) is cytotoxic to prostate TICs isolated from prostate cancer cell lines: DU145, PC3, VCAP, and LAPC4, as well as primary prostate TICs. Furthermore, PTL inhibited TIC-driven tumor formation in mouse xenografts. Using an integrated molecular profiling approach encompassing proteomics, profiles of activated transcription factors and genomics we ascertained the effects of PTL on prostate cancer cells. In addition to the previously described effects of PTL, we determined that the non-receptor tyrosine kinase src, and many src signaling components, including: Csk, FAK, beta1-arrestin, FGFR2, PKC, MEK/MAPK, CaMK, ELK-1, and ELK-1-dependent genes are novel targets of PTL action. Furthermore, PTL altered the binding of transcription factors important in prostate cancer including: C/EBP-alpha, fos related antigen-1 (FRA-1), HOXA-4, c-MYB, SNAIL, SP1, serum response factor (SRF), STAT3, X-box binding protein-1 (XBP1), and p53. In summary, we show PTL is cytotoxic to prostate TICs and describe the molecular events of PTL-mediated cytotoxicity. Therefore, PTL represents a promising therapeutic for prostate cancer treatment.

Cancer stem/progenitor cell active compound 8-quinolinol in combination with paclitaxel achieves an improved cure of breast cancer in the mouse model

Increasing evidence suggests that breast cancer is caused by cancer stem cells and the cure of breast cancer requires eradication of breast cancer stem cells. In this study, we established and characterized a sphere culture model derived from side population cells from the human breast cancer cell line MCF7. The sphere culture could be maintained long term and was enriched in cells expressing known breast cancer stem cell marker CD44+CD24-. These sphere cells showed higher colony formation ability in vitro and higher tumorigenicity in vivo than MCF7 cells, suggesting the enrichment of breast cancer stem/progenitor cells. To identify compounds that preferentially inhibit the sphere cells, we performed a compound library screening. Two lead compounds, NSC24076 and NSC125034 and an analog of NSC125034, 8-quinolinol (8Q), were identified as having preferential activity against the sphere cells. 8Q showed some antitumor activity alone but had much better therapeutic effect and relapse prevention when combined with paclitaxel than either 8Q or paclitaxel alone in both MCF7 and MDA-MB-435 xenograft models. We propose that compounds selectively targeting cancer stem/progenitor cells when combined with standard chemotherapy drugs may produce an improved treatment of cancer without significant relapse.

Cancer stem cells: relevance to SCT

The cancer stem cell (CSC) hypothesis suggests that clonogenic growth potential within an individual tumor is restricted to a specific and phenotypically defined cell population. Evidence for CSC in human tumors initially arose from studies of AML, but functionally similar cell populations have been identified in an increasing number of malignancies. Despite these findings, controversy surrounds the CSC hypothesis, especially the generalization that clonogenic tumor cells are rare. Nevertheless, efforts to define the cellular processes regulating self-renewal and resistance to anticancer therapeutics, two of the major properties ascribed to CSC, are likely to provide useful insights into tumor biology as a whole. BMT has been at the forefront of clinically translating basic stem cell concepts starting with the original hypothesis that normal hematopoietic precursors could rescue patients from myeloablative doses of radiation or chemotherapy. Even today, a better understanding of CSC may enhance ongoing efforts to induce specific and effective anti-tumor immune responses in both the allogeneic and autologous setting. It is also likely that new clinical research approaches will be required to accurately evaluate novel CSC-targeting strategies. Owing to the capacity to produce remissions in most diseases, SCT may provide the ideal clinical platform to carry out these investigations by studying the ability of anti-CSC agents to prolong relapse free and overall survival.

Stem cells and the origin of gliomas: A historical reappraisal with molecular advancements

The biology of both normal and tumor development clearly possesses overlapping and parallel features. Oncogenes and tumor suppressors are relevant not only in tumor biology, but also in physiological developmental regulators of growth and differentiation. Conversely, genes identified as regulators of developmental biology are relevant to tumor biology. This is particularly relevant in the context of brain tumors, where recent evidence is mounting that the origin of brain tumors, specifically gliomas, may represent dysfunctional developmental neurobiology. Neural stem cells are increasingly being investigated as the cell type that originally undergoes malignant transformation – the cell of origin – and the evidence for this is discussed.

Measurement of multiple drug resistance transporter activity in putative cancer stem/progenitor cells

Multiple drug resistance, mediated by the expression and activity of ABC-transporters, is a major obstacle to antineoplastic therapy. Normal tissue stem cells and their malignant counterparts share MDR transporter activity as a major mechanism of self-protection. Although MDR activity is upregulated in response to substrate chemotherapeutic agents, it is also constitutively expressed on both normal tissue stem cells and a subset of tumor cells prior to the initiation of therapy, representing a built-in obstacle to therapeutic ratio. Constitutive and induced MDR activity can be detected in cellular subsets of disaggregated tissues, using the fluorescent substrates Rhodamine 123 and Hoechst 33342 for ABCB1 (also known as P-gp and MDR1) and ABCG2 (BCRP1). In this chapter, we will describe the complete procedure for the detection of MDR activity, including: (1) Preparing single-cell suspensions from tumor and normal tissue specimens; (2) An efficient method to perform cell surface marker staining on large numbers of cells; (3) Flow cytometer setup and controls; (4) Simultaneous measurement of Hoechst 33342 and Rhodamine123 transport; and (5) Data acquisition and analysis.

The stem cell-associated antigen CD133 (Prominin-1) is a molecular therapeutic target for metastatic melanoma

CD133 (Prominin-1) is considered the most important cancer stem cell (CSC)-associated marker identified so far, with increased expression in the CSC fraction of a large variety of human malignancies, including melanoma. Here we investigated the effects of CD133 downregulation in vitro and in vivo in human metastatic melanoma. The average number of CD133 molecules on the cell surface of FEMX-I melanoma cells was decreased by 8.7-fold and 1.8-fold using two different short hairpin RNAs. Downregulation of CD133, confirmed by immunocytochemistry, Western blotting, microarray analysis, and reverse transcription-polymerase chain reaction, resulted in slower cell growth, reduced cell motility, and decreased capacity to form spheroids under stem cell-like growth conditions. Clonal analysis revealed that the reduction in growth rate was proportional to the extent of CD133 downregulation. Monoclonal antibodies directed against two different epitopes of the CD133 protein induced a specific, dose-dependent cytotoxic effect in FEMX-I cells. The downregulation of CD133 severely reduced the capacity of the cells to metastasize, particularly to the spinal cord. In the CD133 downregulated cells, microarray analysis revealed expression changes for only 143 annotated genes (76 up- and 67 downregulated). Ten of the 76 upregulated genes coded for Wnt inhibitors, suggesting an interaction between CD133 and the canonical Wnt pathway. We conclude that CD133, in addition to its role as a CSC marker, is an important therapeutic target for metastatic melanoma and, potentially, for other CD133-expressing cancer types.

Exploring the origins of the normal prostate and prostate cancer stem cell

Prostate epithelial stem cells (PSCs) are primed by the urogenital mesenchyme to initiate bud formation and branching morphogenesis, ultimately culminating in a glandular structure composed of luminal, basal and neuroendocrine cells. Identity of this cell has remained elusive however cell populations enriched for cells exhibiting stem cell characteristics express the stem cell markers CD133(+), alpha2beta1(hi), CD44 and Sca-1 along with embryonic stem cell factors including Oct-1, Nanog, Sox2 and nestin. Androgens are critical to prostate organogenesis and play a major role in normal prostate function and the development of prostate cancer. Cell lineage is another variable in the development of prostate cancer. This review discusses the embryonic prostate stem cell niche, normal prostate development, isolation and characterization of normal prostate and prostate cancer stem cells, and current concepts on the origin of prostate cancer.

Resistance to chemotherapy: new treatments and novel insights into an old problem

Resistance to cancer chemotherapeutic treatment is a common phenomenon, especially in progressive disease. The generation of cellular models of drug resistance has been pivotal in unravelling the main effectors of resistance to traditional chemotherapy at the molecular level (i.e. intracellular drug inactivation, detoxifying systems, defects in DNA repair, apoptosis evasion, membrane transporters and cell adhesion). The development of targeted therapies has also been followed by resistance, reminiscent of an evolutionary arms race, as exemplified by imatinib and other BCR-ABL inhibitors for the treatment of chronic myelogenous leukaemia. Although traditionally associated with the last stages of the disease, recent findings with minimally transformed pretumorigenic primary human cells indicate that the ability to generate drug resistance arises early during the tumorigenic process, before the full transformation. Novel technologies, such as genome profiling, have in certain cases predicted the outcome of chemotherapy and undoubtedly have tremendous potential for the future. In addition, the novel cancer stem cell paradigm raises the prospect of cell-targeted therapies instead of treatment directed against the whole tumour.

Minds That Matter: 2007 Gairdner International Awards Lectures

On October 25 and 26, 2007, at the University of Toronto, the Gairdner Foundation in partnership with Canadian Institutes of Health Research presented a two-day international symposium titled Minds That Matter. The symposium featured academic lectures by Gairdner Award winners past and present and by other leading biomedical scientists. These distinguished researchers share many characteristics in common: creativity, vision, tenacity, and driving curiosity to illuminate discovery with high degree of relevance. The present article summarizes the 2007 Gairdner Award lectures.

Selective induction of chemotherapy resistance of mammary tumors in a conditional mouse model for hereditary breast cancer

We have studied in vivo responses of "spontaneous" Brca1- and p53-deficient mammary tumors arising in conditional mouse mutants to treatment with doxorubicin, docetaxel, or cisplatin. Like human tumors, the response of individual mouse tumors varies, but eventually they all become resistant to the maximum tolerable dose of doxorubicin or docetaxel. The tumors also respond well to cisplatin but do not become resistant, even after multiple treatments in which tumors appear to regrow from a small fraction of surviving cells. Classical biochemical resistance mechanisms, such as up-regulated drug transporters, appear to be responsible for doxorubicin resistance, rather than alterations in drug-damage effector pathways. Our results underline the promise of these mouse tumors for the study of tumor-initiating cells and of drug therapy of human cancer.

Ovarian cancer side population defines cells with stem cell-like characteristics and Mullerian Inhibiting Substance responsiveness

The recent identification of "side population" (SP) cells in a number of unrelated human cancers and their normal tissue sources has renewed interest in the hypothesis that cancers may arise from somatic stem/progenitor cells. The high incidence of recurrence attributable to multidrug resistance and the multiple histologic phenotypes indicative of multipotency suggests a stem cell-like etiology of ovarian cancer. Here we identify and characterize SP cells from two distinct genetically engineered mouse ovarian cancer cell lines. Differential efflux of the DNA-binding dye Hoechst 33342 from these cell lines defined a human breast cancer-resistance protein 1-expressing, verapamil-sensitive SP of candidate cancer stem cells. In vivo, mouse SP cells formed measurable tumors sooner than non-SP (NSP) cells when equal numbers were injected into the dorsal fat pad of nude mice. The presence of Mullerian Inhibiting Substance (MIS) signaling pathway transduction molecules in both SP and NSP mouse cells led us to investigate the efficacy of MIS against these populations in comparison with traditional chemotherapies. MIS inhibited the proliferation of both SP and NSP cells, whereas the lipophilic chemotherapeutic agent doxorubicin more significantly inhibited the NSP cells. Finally, we identified breast cancer-resistance protein 1-expressing verapamil-sensitive SPs in three of four human ovarian cancer cell lines and four of six patient primary ascites cells. In the future, individualized therapy must incorporate analysis of the stem cell-like subpopulation of ovarian cancer cells when designing therapeutic strategies for ovarian cancer patients.