Clonogenic Cancer Stem Cells Research Articles

Abstract NT-115: PRE-EXISTENCE OF POLY-RESISTANT CANCER STEM CELLS IN HIGH-GRADE OVARIAN CANCER

Abstract INTRODUCTION: High-grade ovarian cancer (HGOC) shows excellent responses to standard-of-care surgery and paclitaxel/carboplatin therapy only to relapse 6-24 months later with typically resistant disease. While the origin of this recurrent, resistant disease is unclear, most believe it is acquired by the action of chemotherapeutics. Using novel stem cell technology that enables the cloning of cancer stem cells (CSCs) from epithelial cancers, we have generated large libraries of CSCs from multiple cases of HGOC. And while the vast majority of these CSC clones are killed by standard-of-care chemotherapeutic drugs, a minor fraction shows profound resistance not only to paclitaxel/carboplatin but to a wide range of structurally unrelated chemotherapeutic drugs to which these cells had no prior exposure. We describe screens for drugs that selectively target this resistant CSC population. METHODS: Libraries of 10- to 100,000 CSC clones were generated from individual, therapy naïve, HGOC resections using technology we developed for cloning so-called “adult” stem cells from normal columnar epithelia (Wang et al., 2015, Nature, 522, 173). RESULTS: Paclitaxel/carboplatin resistant CSCs were identified in CSC libraries derived from therapy naïve tumors at ratios of 1:50 to 1:300. By copy number variation, these resistant variant clones proved distinct from the bulk of CSCs, and by gene expression analysis varied from sensitive clones by more than 700 differentially expressed genes. Independent resistant clones from the same library clustered with other resistant clones by both copy number variation and gene expression profiles, suggesting the possibility that resistance within a single tumor is dominated by a single type of resistant CSCs. Clones resistant to paclitaxel/carboplatin were screened in a 384-well format against a wide range of experimental drug-like molecules. These pre-existing resistant clones also proved to be profoundly resistant to a large number of structurally unrelated chemotherapeutic drugs. This same screening program identified drugs that act alone or in combination with paclitaxel to eliminate these resistant clones, suggesting a route to personalized medicine for addressing the problem of recurrent disease in HGOC. CONCLUSIONS: Tumors from patients with HGOC possess clonogenic CSCs including variants that are resistant to a broad spectrum of chemotherapeutics to which they have not been exposed. It is likely that such CSCs would survive standard-of-care chemotherapy and contribute to the recurrent disease seen in HGOC. We have identified known and experimental drugs that specifically eliminate these resistant variants and the overall platform represents a potential strategy to addressing the problem of recurrent disease in these patients. Citation Format: Jingzhong Xie, Yusuke Yamamoto, Marcin Duleba, Bailiang Wang, Rajasekaran Mahalingam, Shan Wang, Wei Rao, Suchan Niroula, Clifford Stephan, Peter Davies, Amir Jazaeri, Giulio Draetta, Molly Brewer, Matt L. Anderson, Christopher P. Crum, Frank McKeon, and Wa Xian. PRE-EXISTENCE OF POLY-RESISTANT CANCER STEM CELLS IN HIGH-GRADE OVARIAN CANCER [abstract]. In: Proceedings of the 12th Biennial Ovarian Cancer Research Symposium; Sep 13-15, 2018; Seattle, WA. Philadelphia (PA): AACR; Clin Cancer Res 2019;25(22 Suppl):Abstract nr NT-115.

Feeding the Data Monster: Data Science in Head and Neck Cancer for Personalized Therapy

ObjectiveHead and neck carcinomas are clinically challenging malignancies because of tumor heterogeneities and resilient tumor subvolumes that require individualized treatment planning and delivery for an improved outcome. Although current approaches to diagnosis and therapy have boosted locoregional control, the long-term survival in this patient group remains unchanged over the last decades. A new approach to head and neck cancer management is therefore needed to better identify patient subgroups that are responsive to specific therapies. The aim of this article is to review the current status of knowledge and practice utilizing big data toward personalized therapy in head and neck cancers based on CT and PET imaging modalities. MethodsLiterature published in English since 2000 was searched using Medline. Additional articles were retrieved via pearling of identified literature. Publications were reviewed and summarized in tabulated format. ResultsStudies based on big data in head and neck cancer are limited; however, the field of radiomics is under continuous development and provides valuable input for personalized treatment. Using PET/PET CT biomarkers for patient treatment individualization and response prediction seems promising, especially in regard to detection of hypoxia and clonogenic cancer stem cells. Literature shows that macroscopic changes in medical images (whether structural or functional) are correlated with biologic and biochemical changes within a tumor. ConclusionCurrent trends in data science suggest that the ideal model for decision support in head and neck cancers should be based on human-machine collaboration, namely, on (1) software-based algorithms, (2) physician innovation collaboratives, and (3) clinician mix optimization.

Imaging of Tumor Characteristics and Molecular Pathways With PET: Developments Over the Last Decade Toward Personalized Cancer Therapy

Improvements in personalized therapy are made possible by the advances in molecular biology that led to developments in molecular imaging, allowing highly specific invivo imaging of biological processes. Positron emission tomography (PET) is the most specific and sensitive imaging technique for invivo molecular targets and pathways, offering quantification and evaluation of functional properties of the targeted anatomy. This work is an integrative research review that summarizes and evaluates the accumulated current status of knowledge of recent advances in PET imaging for cancer diagnosis and treatment, concentrating on novel radiotracers and evaluating their advantages and disadvantages in cancer characterization. Medline search was conducted, limited to English publications from 2007 onward. Identified manuscripts were evaluated for most recent developments in PET imaging of cancer hypoxia, angiogenesis, proliferation, and clonogenic cancer stem cells (CSC). There is an expansion observed from purely metabolic-based PET imaging toward antibody-based PET to achieve more information on cancer characteristics to identify hypoxia, proangiogenic factors, CSC, and others. 64Cu-ATSM, for example, can be used both as a hypoxia and a CSC marker. Progress in the field of functional imaging will possibly lead to more specific tumor targeting and personalized treatment, increasing tumor control and improving quality of life.

Abstract PL07-02: Tumor hypoxia and radiation resistance: Anything new on the horizon?

Abstract Hypoxia is one of the key factors influencing clinical outcome after radiotherapy responsible for reduced local control that will influence overall survival, as may the hypoxic conditions by increasing malignant progression. In sharp contrast with the progresses and the rapid diffusion of functional imaging to characterize hypoxic tumors and the fact that experimental correction of tumor tumor hypoxia reverses tumor resistance to irradiation, there is no approved concomitant therapy in order to maximize response to radiotherapy for the treatment of hypoxic tumors. For decades, hypoxia was thought to act primarily on intrinsic tumor cells resistance, namely the number of clonogenic cancer stem cells surviving after radiation treatment. In the meantime, improvements into the understanding of the mechanisms triggered by hypoxia have unveiled novel molecular targets for potential combination to radiation therapy such as the interplay between STAT3 signaling and adaptation to hypoxia while the impact of tumor hypoxia on tumor microenvironment changes have expand to the immune network. Increased cellular turnover and hypoxia promote the production and release of large amounts of immunosupressive adenosine into the local microenvironment. Hypoxia can induce HIF-1a-dependent expression of arginase-1 and M2 polarization of macrophages. The spectrum of candidate therapies to target hypoxic tumors has moved from bioreductive cytotoxic agents to HIF-1, STAT3 inhibitors while growing number of immunological tools are becoming available for targeting the immune component. The ongoing EORTC 1219-ROG-HNCG/DAHANCA project 29 has gained form the past clinical attempts to target hypoxic tumors and will provide the methodology way for future clinical development of such novel combos based on optimal patients selection using biological and/or imaging criteria. Citation Format: Eric Deutsch, CYrus Chargari. Tumor hypoxia and radiation resistance: Anything new on the horizon? [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2015 Nov 5-9; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl 2):Abstract nr PL07-02.

In vivo epigenetic reprogramming of primary human colon cancer cells enhances metastases.

How metastases develop is not well understood and no genetic mutations have been reported as specific metastatic drivers. Here we have addressed the idea that epigenetic reprogramming by GLI-regulated pluripotent stemness factors promotes metastases. Using primary human colon cancer cells engrafted in mice, we find that transient expression of OCT4, SOX2, KLF4 +/− cMYC establishes an enhanced pro-metastatic state in the primary tumor that is stable through sequential engraftments and is transmitted through clonogenic cancer stem cells. Metastatic reprogramming alters NANOG methylation and stably boosts NANOG and NANOGP8 expression. Metastases and reprogrammed EMT-like phenotypes require endogenous NANOG, but enhanced NANOG is not sufficient to induce these phenotypes. Finally, reprogrammed tumors enhance GLI2, and we show that GLI2high and AXIN2low, which are markers of the metastatic transition of colon cancers, are prognostic of poor disease outcome in patients. We propose that metastases arise through epigenetic reprogramming of cancer stem cells within primary tumors.

Imaging hypoxia to improve radiotherapy outcome

Reduced oxygen levels (hypoxia) is one of the most important factors influencing clinical outcome after radiotherapy. This is primarily because hypoxic cells are resistant to radiation treatment; hence, the greater the number of clonogenic cancer stem cells that exist under hypoxia, the lower the local tumour control. Reduced local control will influence overall survival, as may the hypoxic conditions by increasing malignant progression; however, to fight hypoxia, we should first be able to see it. We need noninvasive approaches that can accurately and reliably image hypoxia in tumours, especially using techniques that are routinely available in the clinic, such as PET, MRI and CT. All these imaging methods are already under clinical evaluation in this context. Such data should allow us to identify those patients on an individual basis who have hypoxic tumours and, thus, at the very least should receive some form of hypoxic modifier in conjunction with radiotherapy. Alternatively, the radiation dose could be either increased to the whole tumour or, if the imaging is accurate enough, only to the hypoxic subvolumes. The aim of this Review is to critically assess the potential use of imaging to help improve clinical outcome to radiotherapy.

Cancer Stem Cell Activity in Mantle Cell Lymphoma Is Inhibited by TLR9 Activation

Patients with Mantle Cell Lymphoma (MCL) often respond to initial cytotoxic therapy, but invariably relapse. This clinical pattern suggests that standard therapies fail to eliminate a population of chemoresistant cells responsible for tumor regrowth and disease relapse. Studies in myeloid leukemias and multiple myeloma have suggested that cancer stem cells (CSC) are relatively quiescent and that this property promotes drug resistance. Therefore, the induction of CSC proliferation may increase their susceptibility to anti-cancer treatment. Unmethylated CpG DNA sequences induce the activation and differentiation of normal B cells through toll like receptor 9 (TLR9), and synthetic CpG oligonucleotides (ODN) are currently undergoing clinical trials in MCL and other B cell non-Hodgkin's lymphomas. We initially examined the effects of TLR9 agonists on the clonogenic growth of the human MCL cell lines Granta 519, Jeko-1, and Rec-1 and found that the unmethylated CpG ODN 2006 (5ug/mL, 48 hours) significantly inhibited the ability of each of these cell lines to form colonies in methylcellulose (p<0.01). We previously demonstrated that clonogenic CSC in multiple myeloma and Hodgkin's lymphoma may be identified based on the relative activity of the intracellular detoxification enzyme aldehydedehydrogenase (ALDH). Similarly, each of the MCL cell lines contained small populations (0.5−2.3%) of ALDH+ cells that were enriched for in vitro clonogenic growth upon primary and secondary plating in methylcellulose. Following treatment with CpG ODN 2006, the population of ALDH+ cells was significantly reduced in each cell line (p<0.05). The self-renewal potential of normal and cancer stem cells is lost through the process of differentiation, and treatment of the MCL cell lines with CpG ODN 2006 resulted in the loss of CD19 and CD20 expression and induction of the plasma cell antigen CD138 by FACS. Similarly, RT-PCR for regulators of B cell differentiation revealed decreased PAX-5 and BCL-6 expression coupled with increased transcription of BLIMP-1 and XBP-1. We hypothesized that the plasma cell differentiation induced by TLR9 agonists may improve the efficacy of anti-tumor agents with known activity against plasma cells, specifically the proteosome inhibitor bortezomib. Treatment with CpG ODN 2006 or bortezomib (10–100nM, 48 hours) alone induced apoptosis in a small percentage of cells within each MCL line, but the combination of these agents synergistically increased the proportion of Annexin V+ cells. In summary, cellular activation by CpG ODN 2006 reduces MCL clonogenicity and stem cell function through the induction of differentiation. In turn, plasma cell maturation appears to increases the sensitivity of MCL to bortezomib and suggests a novel mechanism for the anti-tumor activity of CpG ODN.

Cyclopamine-Mediated Hedgehog Pathway Inhibition Depletes Stem-Like Cancer Cells in Glioblastoma

Brain tumors can arise following deregulation of signaling pathways normally activated during brain development and may derive from neural stem cells. Given the requirement for Hedgehog in non-neoplastic stem cells, we investigated whether Hedgehog blockade could target the stem-like population in glioblastoma multiforme (GBM). We found that Gli1, a key Hedgehog pathway target, was highly expressed in 5 of 19 primary GBM and in 4 of 7 GBM cell lines. Shh ligand was expressed in some primary tumors, and in GBM-derived neurospheres, suggesting a potential mechanism for pathway activation. Hedgehog pathway blockade by cyclopamine caused a 40%-60% reduction in growth of adherent glioma lines highly expressing Gli1 but not in those lacking evidence of pathway activity. When GBM-derived neurospheres were treated with cyclopamine and then dissociated and seeded in media lacking the inhibitor, no new neurospheres formed, suggesting that the clonogenic cancer stem cells had been depleted. Consistent with this hypothesis, the stem-like fraction in gliomas marked by both aldehyde dehydrogenase activity and Hoechst dye excretion (side population) was significantly reduced or eliminated by cyclopamine. In contrast, we found that radiation treatment of our GBM neurospheres increased the percentage of these stem-like cells, suggesting that this standard therapy preferentially targets better-differentiated neoplastic cells. Most importantly, viable GBM cells injected intracranially following Hedgehog blockade were no longer able to form tumors in athymic mice, indicating that a cancer stem cell population critical for ongoing growth had been removed. Disclosure of potential conflicts of interest is found at the end of this article.