A tumor hypoxic niche protects human colon cancer stem cells from chemotherapy

18F-Fluoroazomycin Arabinoside (FAZA) PET/MR as a Biomarker of Hypoxia in Rectal Cancer: A Pilot Study

Tumor hypoxia is a negative prognostic factor in many tumors and is predictive of metastatic spread and poor responsiveness to both chemotherapy and radiotherapy. Purpose: To assess the feasibility of using 18F-Fluoroazomycin arabinoside (FAZA) PET/MR to image tumor hypoxia in patients with locally advanced rectal cancer (LARC) prior to and following neoadjuvant chemoradiotherapy (nCRT). The secondary objective was to compare different reference tissues and thresholds for tumor hypoxia quantification. Patients and Methods: Eight patients with histologically proven LARC were included. All patients underwent 18F-FAZA PET/MR prior to initiation of nCRT, four of whom also had a second scan following completion of nCRT and prior to surgery. Tumors were segmented using T2-weighted MR. Each voxel within the segmented tumor was defined as hypoxic or oxic using thresholds derived from various references: ×1.0 or ×1.2 SUVmean of blood pool [BP] or left ventricle [LV] and SUVmean +3SD for gluteus maximus. Correlation coefficient (CoC) between HF and tumor SUVmax/reference SUVmean TRR for the various thresholds was calculated. Hypoxic fraction (HF), defined as the % hypoxic voxels within the tumor volume was calculated for each reference/threshold. Results: For all cases, baseline and follow-up, the CoCs for gluteus maximus and for BP and LV (×1.0) were 0.241, 0.344, and 0.499, respectively, and HFs were (median; range) 16.6% (2.4-33.8), 36.8% (0.3-72.9), and 30.7% (0.8-55.5), respectively. For a threshold of ×1.2, the CoCs for BP and LV as references were 0.611 and 0.838, respectively, and HFs were (median; range) 10.4% (0-47.6), and 4.3% (0-20.1%), respectively. The change in HF following nCRT ranged from (-18.9%) to (+54%). Conclusions: Imaging of hypoxia in LARC with 18F-FAZA PET/MR is feasible. Blood pool as measured in the LV appears to be the most reliable reference for calculating the HF. There is a wide range of HF and variable change in HF before and after nCRT.

Hypoxia-Inducible Factor-Dependent and Independent Mechanisms Underlying Chemoresistance of Hypoxic Cancer Cells

In hypoxic regions of malignant solid tumors, cancer cells acquire resistance to conventional therapies, such as chemotherapy and radiotherapy, causing poor prognosis in patients with cancer. It is widely recognized that some of the key genes behind this are hypoxia-inducible transcription factors, e.g., hypoxia-inducible factor 1 (HIF-1). Since HIF-1 activity is suppressed by two representative 2-oxoglutarate-dependent dioxygenases (2-OGDDs), PHDs (prolyl-4-hydroxylases), and FIH-1 (factor inhibiting hypoxia-inducible factor 1), the inactivation of 2-OGDD has been associated with cancer therapy resistance by the activation of HIF-1. Recent studies have also revealed the importance of hypoxia-responsive mechanisms independent of HIF-1 and its isoforms (collectively, HIFs). In this article, we collate the accumulated knowledge of HIF-1-dependent and independent mechanisms responsible for resistance of hypoxic cancer cells to anticancer drugs and briefly discuss the interplay between hypoxia responses, like EMT and UPR, and chemoresistance. In addition, we introduce a novel HIF-independent mechanism, which is epigenetically mediated by an acetylated histone reader protein, ATAD2, which we recently clarified.

Sohlh2 Regulates the Stemness and Differentiation of Colon Cancer Stem Cells by Downregulating LncRNA-H19 Transcription

Colon cancer stem cells (CSC) are tumor-initiating cells that drive tumorigenesis and progression through self-renewal and various differentiation potency. Therefore, the identification of factors critical for colon CSC function is vital for the development of therapies. Sohlh2 belongs to the superfamily of bhlh transcription factors and serves as a tumor suppressor in several tumors. The role of Sohlh2 in CSCs remains unknown. Here we demonstrated that Sohlh2 was related to the inhibition of LncRNA-H19/miR-141/β-catenin signaling and led to the consequent suppression of colon CSC stemness and the promotion of colon CSC differentiation in vitro and in vivo. Moreover, Sohlh2 could directly bind to the promoter of LncRNA-H19 and repress its transcription activity. LncRNA-H19 mediated the effects of Sohlh2 on colon CSC stemness and differentiation. Clinically, we observed a significant inverse correlation between Sohlh2 and LncRNA-H19, β-catenin, Lgr5, CD133 expression levels, and positive correlation between Sohlh2 and MUC2, TFF2 expression in colon cancer tissues. Collectively, our findings suggest an important role of the Sohlh2/LncRNA-H19/miR-141/β-catenin pathway in regulating colon CSC stemness and differentiation, suggesting potential therapeutic targets for colon cancer.

IMPLICATIONS

This study identifies that Sohlh2 directly manipulates LncRNA-H19 transcription and suppresses the β-catenin signaling pathway and the Sohlh2/LncRNA-H19/miR-141/β-catenin signaling pathway plays an essential role in the stemness of colon CSCs.

Biomarkers of Cancer Stem Cells for Experimental Research and Clinical Application

The use of biomarkers in cancer diagnosis, therapy, and prognosis has been highly effective over several decades. Studies of biomarkers in cancer patients pre- and post-treatment and during cancer progression have helped identify cancer stem cells (CSCs) and their related microenvironments. These analyses are critical for the therapeutic application of drugs and the efficient targeting and prevention of cancer progression, as well as the investigation of the mechanism of the cancer development. Biomarkers that characterize CSCs have thus been identified and correlated to diagnosis, therapy, and prognosis. However, CSCs demonstrate elevated levels of plasticity, which alters their functional phenotype and appearance by interacting with their microenvironments, in response to chemotherapy and radiotherapeutics. In turn, these changes induce different metabolic adaptations of CSCs. This article provides a review of the most frequently used CSCs and stem cell markers.

Immunofluorescence-Based Method to Assess Cancer Biomarker in the Hypoxic Region of the Tumor

The development of novel imaging technologies allows the analysis of the expression and spatial distribution of multiple markers simultaneously, providing necessary information about a cellular identity and the surrounding microenvironment. This chapter describes the utilization of immunofluorescence to identify such biomarkers in fixed tissue from prostate cancer (PCa) xenografts. One such marker detectable by immunofluorescence is pimonidazole, which has been utilized to locate areas of low oxygen (hypoxia). Pimonidazole, in combination with other biomarkers, could be utilized to identify "niches" in the microenvironment harboring more aggressive cells both within and outside hypoxic areas. Specifically, we describe the method to use pimonidazole for the identification of hypoxic regions in PCa xenograft tumors along with CPT1A (carnitine palmitoyltransferase 1A) expression, an indicator of β-oxidation. This approach could be useful to characterize various biomarkers in the complex hypoxic tumor microenvironment.

Hypoxia and the Receptor for Advanced Glycation End Products (RAGE) Signaling in Cancer

Hypoxia is characterized by an inadequate supply of oxygen to tissues, and hypoxic regions are commonly found in solid tumors. The cellular response to hypoxic conditions is mediated through the activation of hypoxia-inducible factors (HIFs) that control the expression of a large number of target genes. Recent studies have shown that the receptor for advanced glycation end products (RAGE) participates in hypoxia-dependent cellular adaptation. We review recent evidence on the role of RAGE signaling in tumor biology under hypoxic conditions.

Cyclodextrin-based host-guest complexes loaded with regorafenib for colorectal cancer treatment

The malignancy of colorectal cancer (CRC) is connected with inflammation and tumor-associated macrophages (TAMs), but effective therapeutics for CRC are limited. To integrate therapeutic targeting with tumor microenvironment (TME) reprogramming, here we develop biocompatible, non-covalent channel-type nanoparticles (CNPs) that are fabricated through host-guest complexation and self-assemble of mannose-modified γ-cyclodextrin (M-γ-CD) with Regorafenib (RG), RG@M-γ-CD CNPs. In addition to its carrier role, M-γ-CD serves as a targeting device and participates in TME regulation. RG@M-γ-CD CNPs attenuate inflammation and inhibit TAM activation by targeting macrophages. They also improve RG's anti-tumor effect by potentiating kinase suppression. In vivo application shows that the channel-type formulation optimizes the pharmacokinetics and bio-distribution of RG. In colitis-associated cancer and CT26 mouse models, RG@M-γ-CD is proven to be a targeted, safe and effective anti-tumor nanomedicine that suppresses tumor cell proliferation, lesions neovascularization, and remodels TME. These findings indicate RG@M-γ-CD CNPs as a potential strategy for CRC treatment.

Cancer Stem Cell Niche in Colorectal Cancer and Targeted Therapies

Cancer stem cells (CSCs), also known as tumor-initiating cells, are a sub-population of tumor cells found in many human cancers that are endowed with self-renewal and pluripotency. CSCs may be more resistant to conventional anticancer therapies than average cancer cells, as they can easily escape the cytotoxic effects of standard chemotherapy, thereby resulting in tumor relapse. Despite significant progress in related research, effective elimination of CSCs remains an unmet clinical need. CSCs are localized in a specialized microenvironment termed the niche, which plays a pivotal role in cancer multidrug resistance. The niche components of CSCs, such as the extracellular matrix, also physically shelter CSCs from therapeutic agents. Colorectal cancer is the most common malignancy worldwide and presents a relatively transparent process of cancer initiation and development, making it an ideal model for CSC niche research. Here, we review recent advances in the field of CSCs using colorectal cancer as an example to illustrate the potential therapeutic value of targeting the CSC niche. These findings not only provide a novel theoretical basis for in-depth discussions on tumor occurrence, development, and prognosis evaluation, but also offer new strategies for the targeted treatment of cancer.

Metabolic Potential of Cancer Cells in Context of the Metastatic Cascade

The metastatic cascade is a highly plastic and dynamic process dominated by cellular heterogeneity and varying metabolic requirements. During this cascade, the three major metabolic pillars, namely biosynthesis, RedOx balance, and bioenergetics, have variable importance. Biosynthesis has superior significance during the proliferation-dominated steps of primary tumour growth and secondary macrometastasis formation and only minor relevance during the growth-independent processes of invasion and dissemination. Consequently, RedOx homeostasis and bioenergetics emerge as conceivable metabolic key determinants in cancer cells that disseminate from the primary tumour. Within this review, we summarise our current understanding on how cancer cells adjust their metabolism in the context of different microenvironments along the metastatic cascade. With the example of one-carbon metabolism, we establish a conceptual view on how the same metabolic pathway can be exploited in different ways depending on the current cellular needs during metastatic progression.

How Reciprocal Interactions Between the Tumor Microenvironment and Ion Transport Proteins Drive Cancer Progression

Solid tumors comprise two major components: the cancer cells and the tumor stroma. The stroma is a mixture of cellular and acellular components including fibroblasts, mesenchymal and cancer stem cells, endothelial cells, immune cells, extracellular matrix, and tumor interstitial fluid. The insufficient tumor perfusion and the highly proliferative state and dysregulated metabolism of the cancer cells collectively create a physicochemical microenvironment characterized by altered nutrient concentrations and varying degrees of hypoxia and acidosis. Furthermore, both cancer and stromal cells secrete numerous growth factors, cytokines, and extracellular matrix proteins which further shape the tumor microenvironment (TME), favoring cancer progression.Transport proteins expressed by cancer and stromal cells localize at the interface between the cells and the TME and are in a reciprocal relationship with it, as both sensors and modulators of TME properties. It has been amply demonstrated how acid-base and nutrient transporters of cancer cells enable their growth, presumably by contributing both to the extracellular acidosis and the exchange of metabolic substrates and waste products between cells and TME. However, the TME also impacts other transport proteins important for cancer progression, such as multidrug resistance proteins. In this review, we summarize current knowledge of the cellular and acellular components of solid tumors and their interrelationship with key ion transport proteins. We focus in particular on acid-base transport proteins with known or proposed roles in cancer development, and we discuss their relevance for novel therapeutic strategies.

Intravenous iron administration for post-operative anaemia management after colorectal cancer surgery in clinical practice: a single-centre, retrospective study

BACKGROUND

Evidence on the role of intravenous iron (IVI) supplementation after colorectal cancer (CRC) surgery is rather scant. This study was aimed at assessing the benefit of post-operative IVI administration after elective CRC surgery at our institution.

MATERIALS AND METHODS

This was a single-centre, retrospective observational study including all patients who underwent CRC surgery during 2014. Anaemia was defined as a haemoglobin (Hb) <13 g/dL, regardless of gender. Anaemic patients received 200 mg IVI up to three times a week to cover iron deficiency (IVI group). Those who did not receive IVI were placed on standard care (NIVI group). The primary outcome was the proportion of anaemic patients on post-operative day (POD)1 and POD30. Secondary outcomes included Hb changes from POD1 to POD30, transfusion requirements and complication rates.

RESULTS

Of the 159 patients studied, 139 (87%) presented with anaemia: 47 (34%) of these received post-operative IVI and 92 (66%) did not. Patients in the IVI group had lower POD1 Hb levels compared to those in the NIVI group (p=0.001). On POD30, only 103 had their Hb measured (34 IVI, 69 NIVI). Anaemia was more prevalent and more severe among the patients in the IVI group (p=0.027), despite their greater increment in Hb (2.0±1.5 g/dL vs 1.1±1.2 g/dL; p=0.001). Eleven patients needed post-operative transfusions (7 IVI, 4 NIVI; p=0.044). There were no differences in post-operative complication rates between the groups. No IVI-related adverse events were recorded DISCUSSION: Compared with standard care, post-operative IVI administration to anaemic patients improved the recovery of Hb levels at POD30, without increasing post-operative complications.

Administration of Hypoxia-Activated Prodrug Evofosfamide after Conventional Adjuvant Therapy Enhances Therapeutic Outcome and Targets Cancer-Initiating Cells in Preclinical Models of Colorectal Cancer

Purpose: Cancer-initiating cells (C-IC) have been described in multiple cancer types, including colorectal cancer. C-ICs are defined by their capacity to self-renew, thereby driving tumor growth. C-ICs were initially thought to be static entities; however, recent studies have determined these cells to be dynamic and influenced by microenvironmental cues such as hypoxia. If hypoxia drives the formation of C-ICs, then therapeutic targeting of hypoxia could represent a novel means to target C-ICs.Experimental Design: Patient-derived colorectal cancer xenografts were treated with evofosfamide, a hypoxia-activated prodrug (HAP), in combination with 5-fluorouracil (5-FU) or chemoradiotherapy (5-FU and radiation; CRT). Treatment groups included both concurrent and sequential dosing regimens. Effects on the colorectal cancer-initiating cell (CC-IC) fraction were assessed by serial passage in vivo limiting dilution assays. FAZA-PET imaging was utilized as a noninvasive method to assess intratumoral hypoxia.Results: Hypoxia was sufficient to drive the formation of CC-ICs and colorectal cancer cells surviving conventional therapy were more hypoxic and C-IC-like. Using a novel approach to combination therapy, we show that sequential treatment with 5-FU or CRT followed by evofosfamide not only inhibits tumor growth of xenografts compared with 5-FU or CRT alone, but also significantly decreases the CC-IC fraction. Furthermore, noninvasive FAZA-PET hypoxia imaging was predictive of a tumor's response to evofosfamide.Conclusions: Our data demonstrate a novel means to target the CC-IC fraction by adding a HAP sequentially after conventional adjuvant therapy, as well as the use of FAZA-PET as a biomarker for hypoxia to identify tumors that will benefit most from this approach. Clin Cancer Res; 24(9); 2116-27. ©2018 AACR.

Concise Review: Cancer Cells, Cancer Stem Cells, and Mesenchymal Stem Cells: Influence in Cancer Development

Tumors are composed of different types of cancer cells that contribute to tumor heterogeneity. Among these populations of cells, cancer stem cells (CSCs) play an important role in cancer initiation and progression. Like their stem cells counterpart, CSCs are also characterized by self-renewal and the capacity to differentiate. A particular population of CSCs is constituted by mesenchymal stem cells (MSCs) that differentiate into cells of mesodermal characteristics. Several studies have reported the potential pro-or anti-tumorigenic influence of MSCs on tumor initiation and progression. In fact, MSCs are recruited to the site of wound healing to repair damaged tissues, an event that is also associated with tumorigenesis. In other cases, resident or migrating MSCs can favor tumor angiogenesis and increase tumor aggressiveness. This interplay between MSCs and cancer cells is fundamental for cancerogenesis, progression, and metastasis. Therefore, an interesting topic is the relationship between cancer cells, CSCs, and MSCs, since contrasting reports about their respective influences have been reported. In this review, we discuss recent findings related to conflicting results on the influence of normal and CSCs in cancer development. The understanding of the role of MSCs in cancer is also important in cancer management. Stem Cells Translational Medicine 2017;6:2115-2125.

Time-lapse microscopic observation of non-dividing cells in cultured human osteosarcoma MG-63 cell line

Cancer stem cells resemble normal tissue-specific stem cells in many aspects, such as self-renewal and plasticity. Like their non-malignant counterparts, cancer stem cells are suggested to exhibit a relative quiescence. The established cancer cell lines reportedly harbor slow-proliferating cells that are positive for some cancer stem cells markers. However, the fate of these cells and their progeny remains unknown. We used time-lapse microscopy and the contrast-based segmentation algorithm to identify and monitor actively dividing and non-dividing cells in human osteosarcoma MG-63 cell line. Within the monitored field of view the non-dividing cells were represented by three cells that never divided, and one cell that attempted to divide, but failed cytokinesis, and later, after significantly prolonged division, produced the progeny with enlarged segmented nuclei, thus pointing to a possible mitotic catastrophe. Together, these cells initially constituted about 6.2% of the total number of seeded cells, yet only 0.02% of all cells at the end of the observation period when cells became confluent. Non-dividing cells were characterized by rounded shape, dark nuclei, random cytoplasmic streaming and subtle oscillatory movement, however, they did not migrate and rarely formed cell-cell contacts as compared to actively dividing cells. Our data indicate that the observed non-dividing MG-63 cells do not have a growth advantage over other cells and, therefore, they do not contribute to the cancer stem cells pool.

Molecular Pathways: Metabolic Control of Histone Methylation and Gene Expression in Cancer

Epigenetic alterations contribute to tumor development, progression, and therapeutic response. Many epigenetic enzymes use metabolic intermediates as cofactors to modify chromatin structure. Emerging evidence suggests that fluctuation in metabolite levels may regulate activities of these chromatin-modifying enzymes. Here, we summarize recent progress in understanding the cross-talk between metabolism and epigenetic control of gene expression in cancer. We focus on how metabolic changes, due to diet, genetic mutations, or tumor microenvironment, regulate histone methylation status and, consequently, affect gene expression profiles to promote tumorigenesis. Importantly, we also suggest some potential therapeutic approaches to target the oncogenic role of metabolic alterations and epigenetic modifications in cancer. Clin Cancer Res; 23(15); 4004-9. ©2017 AACR.

Clonal Heterogeneity and Tumor Evolution: Past, Present, and the Future

Intratumor heterogeneity, which fosters tumor evolution, is a key challenge in cancer medicine. Here, we review data and technologies that have revealed intra-tumor heterogeneity across cancer types and the dynamics, constraints, and contingencies inherent to tumor evolution. We emphasize the importance of macro-evolutionary leaps, often involving large-scale chromosomal alterations, in driving tumor evolution and metastasis and consider the role of the tumor microenvironment in engendering heterogeneity and drug resistance. We suggest that bold approaches to drug development, harnessing the adaptive properties of the immune-microenvironment while limiting those of the tumor, combined with advances in clinical trial-design, will improve patient outcome.

Targeting therapy-resistant cancer stem cells by hyperthermia

Eradication of all malignant cells is the ultimate but challenging goal of anti-cancer treatment; most traditional clinically-available approaches fail because there are cells in a tumour that either escape therapy or become therapy-resistant. A subpopulation of cancer cells, the cancer stem cells (CSCs), is considered to be of particular significance for tumour initiation, progression and metastasis. CSCs are considered in particular to be therapy-resistant and may drive disease recurrence, which positions CSCs in the focus of anti-cancer research, but successful CSC-targeting therapies are limited. Here, we argue that hyperthermia - a therapeutic approach based on local heating of a tumour - is potentially beneficial for targeting CSCs in solid tumours. First, hyperthermia has been described to target cells in hypoxic and nutrient-deprived tumour areas where CSCs reside and ionising radiation and chemotherapy are least effective. Second, hyperthermia can modify factors that are essential for tumour survival and growth, such as the microenvironment, immune responses, vascularisation and oxygen supply. Third, hyperthermia targets multiple DNA repair pathways, which are generally upregulated in CSCs and protect them from DNA-damaging agents. Addition of hyperthermia to the therapeutic armamentarium of oncologists may thus be a promising strategy to eliminate therapy-escaping and -resistant CSCs.

Targeting Glioblastoma with the Use of Phytocompounds and Nanoparticles

Glioblastoma multiforme (GBM) are extremely lethal and still poorly treated primary brain tumors, characterized by the presence of highly tumorigenic cancer stem cell (CSC) subpopulations, considered responsible for tumor relapse. In order to successfully eradicate GBM growth and recurrence, new anti-cancer strategies selectively targeting CSCs should be designed. CSCs might be eradicated by targeting some of their cell surface markers and transporters, inducing their differentiation, impacting their hyper-glycolytic metabolism, inhibiting CSC-related signaling pathways and/or by targeting their microenvironmental niche. In this regard, phytocompounds such as curcumin, isothiocyanates, resveratrol and epigallocatechin-3-gallate have been shown to prevent or reverse cancer-related epigenetic dysfunctions, reducing tumorigenesis, preventing metastasis and/or increasing chemotherapy and radiotherapy efficacy. However, the actual bioavailability and metabolic processing of phytocompounds is generally unknown, and the presence of the blood brain barrier often represents a limitation to glioma treatments. Nowadays, nanoparticles (NPs) can be loaded with therapeutic compounds such as phytochemicals, improving their bioavailability and their targeted delivery within the GBM tumor bulk. Moreover, NPs can be designed to increase their tropism and specificity toward CSCs by conjugating their surface with antibodies specific for CSC antigens, with ligands or with glucose analogues. Here we discuss the use of phytochemicals as anti-glioma agents and the applicability of phytochemical-loaded NPs as drug delivery systems to target GBM. Additionally, we provide some examples on how NPs can be specifically formulated to improve CSC targeting.

Regional glutamine deficiency in tumours promotes dedifferentiation through inhibition of histone demethylation

Poorly organized tumour vasculature often results in areas of limited nutrient supply and hypoxia. Despite our understanding of solid tumour responses to hypoxia, how nutrient deprivation regionally affects tumour growth and therapeutic response is poorly understood. Here, we show that the core region of solid tumours displayed glutamine deficiency compared with other amino acids. Low glutamine in tumour core regions led to dramatic histone hypermethylation due to decreased α-ketoglutarate levels, a key cofactor for the Jumonji-domain-containing histone demethylases. Using patient-derived (V600E)BRAF melanoma cells, we found that low-glutamine-induced histone hypermethylation resulted in cancer cell dedifferentiation and resistance to BRAF inhibitor treatment, which was largely mediated by methylation on H3K27, as knockdown of the H3K27-specific demethylase KDM6B and the methyltransferase EZH2 respectively reproduced and attenuated the low-glutamine effects in vitro and in vivo. Thus, intratumoral regional variation in the nutritional microenvironment contributes to tumour heterogeneity and therapeutic response.

The Role of Hypoxia and Cancer Stem Cells in Renal Cell Carcinoma Pathogenesis

The cancer stem cell (CSC) model has recently been approached also in renal cell carcinoma (RCC). A few populations of putative renal tumor-initiating cells (TICs) were identified, but they are indifferently understood; however, the first and most thoroughly investigated are CD105-positive CSCs. The article presents a detailed comparison of all renal CSC-like populations identified by now as well as their presumable origin. Hypoxic activation of hypoxia-inducible factors (HIFs) contributes to tumor aggressiveness by multiple molecular pathways, including the governance of immature stem cell-like phenotype and related epithelial-to-mesenchymal transition (EMT)/de-differentiation, and, as a result, poor prognosis. Due to intrinsic von Hippel-Lindau protein (pVHL) loss of function, clear-cell RCC (ccRCC) develops unique pathological intra-cellular pseudo-hypoxic phenotype with a constant HIF activation, regardless of oxygen level. Despite satisfactory evidence concerning pseudo-hypoxia importance in RCC biology, its influence on putative renal CSC-like largely remains unknown. Thus, the article discusses a current knowledge of HIF-1α/2α signaling pathways in the promotion of undifferentiated tumor phenotype in general, including some experimental findings specific for pseudo-hypoxic ccRCC, mostly dependent from HIF-2α oncogenic functions. Existing gaps in understanding both putative renal CSCs and their potential connection with hypoxia need to be filled in order to propose breakthrough strategies for RCC treatment.

Chronic Myeloid Leukemia and Hepatoblastoma: Two Cancer Models to Link Metabolism to Stem Cells

Low oxygen tension is a critical aspect of the stem cell niche where stem cells are long-term maintained. In “physiologically hypoxic” stem cell niches, low oxygen tension restrains the clonal expansion of stem cells without blocking their cycling, thereby contributing substantially to favor their self-renewal. The capacity of stem cells, hematopoietic stem cells in particular, to reside in low oxygen is likely due to their specific metabolic profile. A strong drive to the characterization of this profile emerges from the notion that cancer stem cells (CSC), like normal stem cells, most likely rely on metabolic cues for the balance between self-renewal/maintenance and clonal expansion/differentiation. Accordingly, CSC homing to low oxygen stem cell niches is the best candidate mechanism to sustain the so-called minimal residual disease. Thus, the metabolic profile of CSC impacts long-term cancer response to therapy. On that basis, strategies to target CSC are intensely sought as a means to eradicate neoplastic diseases. Our “metabolic” approach to this challenge was based on two different experimental models: (A) the Yoshida’s ascites hepatoma AH130 cells, a highly homogeneous cancer cell population expressing stem cell features, used to identify, in CSC adapted to oxygen and/or nutrient shortage, metabolic features of potential therapeutic interest; (B) chronic myeloid leukemia, used to evaluate the impact of oxygen and/or nutrient shortage on the expression of an oncogenetic protein, the loss of which determines the refractoriness of CSC to oncogene-targeting therapies.

Cancer Stem Cells

The cancer stem cell model in solid tumors has evolved significantly from the early paradigm shifting work highlighting parallels between the stem cell hierarchy in hematologic malignancies and solid tumors. Putative stem cells can dedifferentiated, be induced by context, and be the result of accumulated genetic mutations. The simple hypothesis that stem cell therapies will overcome the minority of cells that lead to recurrence has evolved with it. Nevertheless, the body of evidence that this field is clinically relevant in patients and patient care has grown with the complexity of the hypotheses, and numerous clinical strategies to target these cells have been identified. Herein we review this progress and highlight the work still outstanding.

Agent-Based Modeling in Systems Pharmacology

Modeling and simulation (M&S) techniques provide a platform for knowledge integration and hypothesis testing to gain insights into biological systems that would not be possible a priori. Agent‐based modeling (ABM) is an M&S technique that focuses on describing individual components rather than homogenous populations. This tutorial introduces ABM to systems pharmacologists, using relevant case studies to highlight how ABM‐specific strengths have yielded success in the area of preclinical mechanistic modeling.

Spatial and functional heterogeneities shape collective behavior of tumor-immune networks

Tumor growth involves a dynamic interplay between cancer cells and host cells, which collectively form a tumor microenvironmental network that either suppresses or promotes tumor growth under different conditions. The transition from tumor suppression to tumor promotion is mediated by a tumor-induced shift in the local immune state, and despite the clinical challenge this shift poses, little is known about how such dysfunctional immune states are initiated. Clinical and experimental observations have indicated that differences in both the composition and spatial distribution of different cell types and/or signaling molecules within the tumor microenvironment can strongly impact tumor pathogenesis and ultimately patient prognosis. How such “functional” and “spatial” heterogeneities confer such effects, however, is not known. To investigate these phenomena at a level currently inaccessible by direct observation, we developed a computational model of a nascent metastatic tumor capturing salient features of known tumor-immune interactions that faithfully recapitulates key features of existing experimental observations. Surprisingly, over a wide range of model formulations, we observed that heterogeneity in both spatial organization and cell phenotype drove the emergence of immunosuppressive network states. We determined that this observation is general and robust to parameter choice by developing a systems-level sensitivity analysis technique, and we extended this analysis to generate other parameter-independent, experimentally testable hypotheses. Lastly, we leveraged this model as an in silico test bed to evaluate potential strategies for engineering cell-based therapies to overcome tumor associated immune dysfunction and thereby identified modes of immune modulation predicted to be most effective. Collectively, this work establishes a new integrated framework for investigating and modulating tumor-immune networks and provides insights into how such interactions may shape early stages of tumor formation.

Over the course of tumor growth, cancer cells interact with normal cells via processes that are difficult to understand by experiment alone. This challenge is particularly pronounced at early stages of tumor formation, when experimental observation is most limited. Elucidating such interactions could inform both understanding of cancer and clinical practice. To address this need we developed a computational model capturing the current understanding of how individual metastatic tumor cells and immune cells sense and contribute to the tumor environment, which in turn enabled us to investigate the complex, collective behavior of these systems. Surprisingly, we discovered that tumor escape from immune control was enhanced by the existence of small differences (or heterogeneities) in the responses of individual immune cells to their environment, as well as by heterogeneities in the way that cells and the molecules they secrete are arranged in space. These conclusions held true over a range of model formulations, suggesting that this is a general feature of these tumor-immune networks. Finally, we used this model as a test bed to evaluate potential strategies for enhancing immunological control of early tumors, ultimately predicting that specifically modulating tumor-associated immune dysfunction may be more effective than simply enhanced tumor killing.

Biomarkers and signaling pathways of colorectal cancer stem cells

The progression of colorectal cancer is commonly characterized by accumulation of genetic or epigenetic abnormalities, altering regulation of gene expression as well as normal protein structures and functions. Nonetheless, there are some questions that remain to be elucidated, such as the origin of cancer cells and populations of cells initiating and propagating tumor development. Currently, there are two rival theories describing the process of carcinogenesis. One is the stochastic model, arguing that any cell is capable of initiating and triggering the development of cancer. Meanwhile, the cancer stem cell model hypothesizes that only a small fraction of stem cells possesses cancer-promoting properties. Typically, colorectal cancer stem cells (CSCs) share the same molecular signaling profiles with normal stem cells or embryonic stem cells, such as Wnt, Notch, TGF-β, and Hedgehog. Nevertheless, CSCs differ from normal stem cells and the bulk of tumor cells in their tumorigenic potential and susceptibility to chemotherapeutic drugs. This may be a possible explanation of the high percentage of cancer recurrence in patients who underwent chemotherapeutic treatment and surgery. This review article focuses on the colorectal cancer stem cell biomarkers and the role of upregulated signaling pathways implicated in the initiation and progression of colorectal cancer.

RAGE mediates S100A4-induced cell motility via MAPK/ERK and hypoxia signaling and is a prognostic biomarker for human colorectal cancer metastasis

Survival of colorectal cancer patients is strongly dependent on development of distant metastases. S100A4 is a prognostic biomarker and inducer for colorectal cancer metastasis. Besides exerting intracellular functions, S100A4 is secreted extracellularly. The receptor for advanced glycation end products (RAGE) is one of its interaction partners. The impact of the S100A4-RAGE interaction for cell motility and metastasis formation in colorectal cancer has not been elucidated so far. Here we demonstrate the RAGE-dependent increase in migratory and invasive capabilities of colorectal cancer cells via binding to extracellular S100A4. We show the direct interaction of S100A4 and RAGE, leading to hyperactivated MAPK/ERK and hypoxia signaling. The S100A4-RAGE axis increased cell migration (P<0.005) and invasion (P<0.005), which was counteracted with recombinant soluble RAGE and RAGE-specific antibodies. In colorectal cancer patients, not distantly metastasized at surgery, high RAGE expression in primary tumors correlated with metachronous metastasis, reduced overall (P=0.022) and metastasis-free survival (P=0.021).

In summary, interaction of S100A4-RAGE mediates S100A4-induced colorectal cancer cell motility. RAGE by itself represents a biomarker for prognosis of colorectal cancer. Thus, therapeutic approaches targeting RAGE or intervening in S100A4-RAGE-dependent signaling early in tumor progression might represent alternative strategies restricting S100A4-induced colorectal cancer metastasis.

RNA interference targeting hypoxia-inducible factor 1α via a novel multifunctional surfactant attenuates glioma growth in an intracranial mouse model

OBJECT

High-grade gliomas are the most common form of adult brain cancer, and patients have a dismal survival rate despite aggressive therapeutic measures. Intratumoral hypoxia is thought to be a main contributor to tumorigenesis and angiogenesis of these tumors. Because hypoxia-inducible factor 1α (HIF-1α) is the major mediator of hypoxia-regulated cellular control, inhibition of this transcription factor may reduce glioblastoma growth.

METHODS

Using an orthotopic mouse model with U87-LucNeo cells, the authors used RNA interference to knock down HIF-1α in vivo. The small interfering RNA (siRNA) was packaged using a novel multifunctional surfactant, 1-(aminoethyl) iminobis[N-(oleicylcysteinylhistinyl-1-aminoethyl)propionamide] (EHCO), a nucleic acid carrier that facilitates cellular uptake and intracellular release of siRNA. Stereotactic injection was used to deliver siRNA locally through a guide-screw system, and delivery/uptake was verified by imaging of fluorescently labeled siRNA. Osmotic pumps were used for extended siRNA delivery to model a commonly used human intracranial drug-delivery technique, convection-enhanced delivery.

RESULTS

Mice receiving daily siRNA injections targeting HIF-1α had a 79% lower tumor volume after 50 days of treatment than the controls. Levels of the HIF-1 transcriptional targets vascular endothelial growth factor (VEGF), glucose transporter 1 (GLUT-1), c-MET, and carbonic anhydrase-IX (CA-IX) and markers for cell growth (MIB-1 and microvascular density) were also significantly lower. Altering the carrier EHCO by adding polyethylene glycol significantly increased the efficacy of drug delivery and subsequent survival.

CONCLUSIONS

Treating glioblastoma with siRNA targeting HIF-1α in vivo can significantly reduce tumor growth and increase survival in an intracranial mouse model, a finding that has direct clinical implications.

Hypercoagulation in colorectal cancer: what can platelet indices tell us?

Colorectal cancer, as all solid malignancies, is accompanied by changes in the haemostatic mechanism favoring the establishment of a thrombotic potential, with platelets playing a key-role in this framework; they further link colorectal cancer progression and hypercoagulation with the immune-response against the neoplastic spread. Under this rationale, various studies have assessed the use of platelet indices as prognostic markers of the biological behavior of colorectal cancer, demonstrating significant results. We herein attempt to summarize in a narrative and critical approach the relevant available data and the underlying pathophysiology, stressing the necessity of a more thorough understanding and future implementation of platelet indices in all stages of care we deliver to colorectal cancer patients.

Orphan nuclear receptor Nur77 promotes colorectal cancer invasion and metastasis by regulating MMP-9 and E-cadherin

Nur77, an orphan member of the nuclear receptor superfamily, has been implicated in tumorigenesis. However, its contributions to colorectal cancer (CRC) invasion and metastasis are largely under characterized. Here, we present the first evidence that the invasion and metastasis of CRC is regulated by Nur77. High expression of Nur77 was observed in clinical CRC tissues, and this elevated expression was significantly associated with advanced tumor, lymph nodes, distant metastasis stage (P = 0.003), lymph node metastasis (P = 0.001) and poor survival (P = 0.03). Overexpression of Nur77 in CRC cells enhanced cell invasion in vitro, whereas knockdown of Nur77 diminished cell invasion and metastasis both in vitro and in vivo. In studying the possible mechanism by which overexpression of Nur77 contributes to CRC invasion and metastasis, we observed that the nuclear protein Nur77 promoted the expression of matrix metalloproteinase (MMP)-9, a novel downstream target of Nur77, and subsequently decreased the expression of E-cadherin. Examination of clinical samples further showed that Nur77 expression is positively correlated with MMP-9, whereas negatively correlated with E-cadherin. Interestingly, Nur77-mediated CRC invasion via MMP-9 and E-cadherin could be mimicked by some metastasis-inducible factors including hypoxia and prostaglandin E2. Collectively, our study demonstrated that Nur77 could promote the invasion and metastasis of CRC cells through regulation of MMP-9/E-cadherin signaling. These observations provide a possible new strategy for potentially treating or preventing the metastasis of CRC through targeting of Nur77.

Defining normoxia, physoxia and hypoxia in tumours-implications for treatment response

Tumour hypoxia is increasingly recognized as a major deleterious factor in cancer therapies, as it compromises treatment and drives malignant progression. This review seeks to clarify the oxygen levels that are pertinent to this issue. It is argued that normoxia (20% oxygen) is an extremely poor comparator for "physoxia", i.e. the much lower levels of oxygen universally found in normal tissues, which averages about 5% oxygen, and ranges from about 3% to 7.4%. Importantly, it should be recognized that the median oxygenation in untreated tumours is significantly much lower, falling between approximately 0.3% and 4.2% oxygen, with most tumours exhibiting median oxygen levels <2%. This is partially dependent on the tissue of origin, and it is notable that many prostate and pancreatic tumours are profoundly hypoxic. In addition, therapy can induce even further, often unrecognized, changes in tumour oxygenation that may vary longitudinally, increasing or decreasing during treatment in ways that are not always predictable. Studies that fail to take cognizance of the actual physiological levels of oxygen in tissues (approximately 5%) and tumours (approximately 1%) may fail to identify the real circumstances driving tumour response to treatment and/or malignant progression. This can be of particular importance in genetic studies in vitro when comparison to human tumours is required.

The colon cancer stem cell microenvironment holds keys to future cancer therapy

BACKGROUND

Colorectal cancer remains the most common gastrointestinal cancer. While screening combined with effective surgical treatment has reduced its mortality, we still do not have effective means to prevent recurrence nor to treat metastatic disease. What we know about cancer biology has gone through revolutionary changes in recent decades. The advent of the cancer stem cell theory has accelerated our understanding of the cancer cell. However, there is increasing evidence that cancer cells are influenced by their surrounding microenvironment.

PURPOSE

This review divides the tumor microenvironment into four functional components-the stem cell niche, cancer stroma, immune cells, and vascular endothelia-and examines their individual and collective influence on the growth and metastasis of the colon cancer stem cell. The discussion will highlight the need to fully exploit the tumor microenvironment when designing future prognostic tools and therapies.

Cancer stem cells in colorectal cancer from pathogenesis to therapy: Controversies and perspectives

Colorectal cancer remains one of the most common and lethal malignancies worldwide despite the use of various therapeutic strategies. A better understanding of the mechanisms responsible for tumor initiation and progression is essential for the development of novel, more powerful therapies. The traditional, so-called “stochastic model” of tumor development, which assumes that each cancer cell is tumorigenic, has been deeply challenged during the past decade by the identification of cancer stem cells (CSCs), a biologically distinct subset of cells within the bulk of tumor mass. This discovery led to the development of the hierarchical model of tumorigenesis which assumes that only CSCs have the ability to initiate tumor growth, both at primary and metastatic sites. This model implies that the elimination of all CSCs is fundamental to eradicate tumors and that failure to do so might be responsible for the occurrence of relapses and/or metastases frequently observed in the clinical management of colorectal cancer patients. Identification and isolation of CSCs is essential for a better understanding of their role in the tumorigenetic process and for the development of CSC-specific therapies. Several methods have been used for this purpose and many efforts have been focused on the identification of specific CSC-surface markers. This review provides an overview of the proposed roles of CSC in human colorectal tumorigenesis focusing on the most important molecules identified as CSC-specific markers in colorectal cancer and on the potential strategies for the development of CSC-targeted therapy.

Hypoxia triggers a Nur77-β-catenin feed-forward loop to promote the invasive growth of colon cancer cells

Background:

β-Catenin is a potent oncogenic protein in colorectal cancer (CRC), but the targets and regulation of this important signalling molecule are not completely understood. Hypoxia is a prominent feature of solid tumours that contributes to cancer progression.

Methods:

Here, we analysed the regulation between Nur77 and β-catenin under hypoxic conditions. Cell proliferation, migration, and invasion assays were performed to assess functional consequences.

Results:

We showed that hypoxia stimulated co-upregulation of β-catenin and Nur77 in a number of human CRC cell lines. Interestingly, expression of β-catenin and Nur77 by hypoxia formed a mutual feedback regulation circuits that conferred aggressive growth of CRC. Overexpression of β-catenin increased Nur77 transcription through hypoxia-inducible factor-1α rather than T-cell factor. Nur77-mediated activation of β-catenin by hypoxia was independent of both DNA binding and transactivation. Further, we showed that hypoxic activation of β-catenin was independent of the classical adenomatous polyposis coli and p53 pathways, but stimulated by phosphatidylinositol 3-kinase/Akt in a Nur77-dependent manner. Under hypoxic conditions, enhanced β-catenin and Nur77 expression synergistically stimulated CRC cell migration, invasion, and epithelial–mesenchymal transition.

Conclusion:

These findings provide a novel molecular mechanism for hypoxic CRCs that may contribute to tumour progression, and its targeting may represent an effective therapeutic avenue.

Influence of tumour micro-environment heterogeneity on therapeutic response

Tumour formation involves the co-evolution of neoplastic cells together with extracellular matrix, tumour vasculature and immune cells. Successful outgrowth of tumours and eventual metastasis is not determined solely by genetic alterations in tumour cells, but also by the fitness advantage such mutations confer in a given environment. As fitness is context dependent, evaluating tumours as complete organs, and not simply as masses of transformed epithelial cells, becomes paramount. The dynamic tumour topography varies drastically even throughout the same lesion. Heterologous cell types within tumours can actively influence therapeutic response and shape resistance.

Critical research gaps and translational priorities for the successful prevention and treatment of breast cancer

INTRODUCTION

Breast cancer remains a significant scientific, clinical and societal challenge. This gap analysis has reviewed and critically assessed enduring issues and new challenges emerging from recent research, and proposes strategies for translating solutions into practice.

METHODS

More than 100 internationally recognised specialist breast cancer scientists, clinicians and healthcare professionals collaborated to address nine thematic areas: genetics, epigenetics and epidemiology; molecular pathology and cell biology; hormonal influences and endocrine therapy; imaging, detection and screening; current/novel therapies and biomarkers; drug resistance; metastasis, angiogenesis, circulating tumour cells, cancer 'stem' cells; risk and prevention; living with and managing breast cancer and its treatment. The groups developed summary papers through an iterative process which, following further appraisal from experts and patients, were melded into this summary account.

RESULTS

The 10 major gaps identified were: (1) understanding the functions and contextual interactions of genetic and epigenetic changes in normal breast development and during malignant transformation; (2) how to implement sustainable lifestyle changes (diet, exercise and weight) and chemopreventive strategies; (3) the need for tailored screening approaches including clinically actionable tests; (4) enhancing knowledge of molecular drivers behind breast cancer subtypes, progression and metastasis; (5) understanding the molecular mechanisms of tumour heterogeneity, dormancy, de novo or acquired resistance and how to target key nodes in these dynamic processes; (6) developing validated markers for chemosensitivity and radiosensitivity; (7) understanding the optimal duration, sequencing and rational combinations of treatment for improved personalised therapy; (8) validating multimodality imaging biomarkers for minimally invasive diagnosis and monitoring of responses in primary and metastatic disease; (9) developing interventions and support to improve the survivorship experience; (10) a continuing need for clinical material for translational research derived from normal breast, blood, primary, relapsed, metastatic and drug-resistant cancers with expert bioinformatics support to maximise its utility. The proposed infrastructural enablers include enhanced resources to support clinically relevant in vitro and in vivo tumour models; improved access to appropriate, fully annotated clinical samples; extended biomarker discovery, validation and standardisation; and facilitated cross-discipline working.

CONCLUSIONS

With resources to conduct further high-quality targeted research focusing on the gaps identified, increased knowledge translating into improved clinical care should be achievable within five years.

Cancer stem cell gene profile as predictor of relapse in high risk stage II and stage III, radically resected colon cancer patients

Clinical data indicate that prognostic stratification of radically resected colorectal cancer based on disease stage only may not be always be adequate. Preclinical findings suggest that cancer stem cells may influence the biological behaviour of colorectal cancer independently from stage: objective of the study was to assess whether a panel of stemness markers were correlated with clinical outcome in resected stage II and III colon cancer patients. A panel of 66 markers of stemness were analysed and thus patients were divided into two groups (A and B) with most patients clustering in a manner consistent with different time to relapse by using a statistical algorithm. A total of 62 patients were analysed. Thirty-six (58%) relapsed during the follow-up period (range 1.63–86.5 months). Twelve (19%) and 50 (81%) patients were allocated into group A and B, respectively. A significantly different median relapse-free survival was observed between the 2 groups (22.18 vs 42.85 months, p = 0.0296). Among of all genes tested, those with the higher “weight” in determining different prognosis were CD44, ALCAM, DTX2, HSPA9, CCNA2, PDX1, MYST1, COL1A1 and ABCG2. This analysis supports the idea that, other than stage, biological variables, such as expression levels of colon cancer stem cell genes, may be relevant in determining an increased risk of relapse in resected colorectal cancer patients.