Cancer Stem Cells, Models of Study and Implications of Therapy Resistance Mechanisms

In an increasing number of cancers, tumor populations called cancer stem cells (CSCs), or tumor-initiating cells, have been defined in functional assays of self-renewal and tumor initiation. Moreover, recent work in several different cancers has suggested the CSC population as a source of chemotherapy and radiation-therapy resistance within tumors. Work in glioblastoma and breast cancers supports the idea that CSCs may possess innate resistance mechanisms against radiation- and chemotherapy-induced cancer cell death, allowing them to survive and initiate tumor recurrence. Several resistance mechanisms have been proposed, including amplified checkpoint activation and DNA damage repair as well as increased Wnt/β-catenin and Notch signaling. Novel targeted therapies against the DNA damage checkpoint or stem-cell maintenance pathways may sensitize CSCs to radiation or other therapies. Another important category of cancer therapies are antiangiogenic and vascular targeting agents, which are also becoming integrated in the treatment paradigm of an increasing number of cancers. Recent results from our laboratory and others support a role for CSCs in the angiogenic drive as well as the mechanism of antiangiogenic agents. Identifying and targeting the molecular mechanisms responsible for CSC therapeutic resistance may improve the efficacy of current cancer therapies.

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Behind the Adaptive and Resistance Mechanisms of Cancer Stem Cells to TRAIL

Pharmaceutics ◽

10.3390/pharmaceutics13071062 ◽

2021 ◽

Vol 13 (7) ◽

pp. 1062

Author(s):

Adriana G. Quiroz-Reyes ◽

Paulina Delgado-Gonzalez ◽

Jose Francisco Islas ◽

Juan Luis Delgado Gallegos ◽

Javier Humberto Martínez Martínez Garza ◽

...

Keyword(s):

Stem Cells ◽

Cancer Stem Cells ◽

Cancer Progression ◽

Molecular Mechanisms ◽

Therapy Resistance ◽

Resistance Mechanisms ◽

Invasion Pathways ◽

Trail Resistance ◽

Novel Strategy ◽

Cancer Remission

Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL), also known as Apo-2 ligand (Apo2L), is a member of the TNF cytokine superfamily. TRAIL has been widely studied as a novel strategy for tumor elimination, as cancer cells overexpress TRAIL death receptors, inducing apoptosis and inhibiting blood vessel formation. However, cancer stem cells (CSCs), which are the main culprits responsible for therapy resistance and cancer remission, can easily develop evasion mechanisms for TRAIL apoptosis. By further modifying their properties, they take advantage of this molecule to improve survival and angiogenesis. The molecular mechanisms that CSCs use for TRAIL resistance and angiogenesis development are not well elucidated. Recent research has shown that proteins and transcription factors from the cell cycle, survival, and invasion pathways are involved. This review summarizes the main mechanism of cell adaption by TRAIL to promote response angiogenic or pro-angiogenic intermediates that facilitate TRAIL resistance regulation and cancer progression by CSCs and novel strategies to induce apoptosis.

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Targeting cancer stem cells for reversing therapy resistance: mechanism, signaling, and prospective agents

Signal Transduction and Targeted Therapy ◽

10.1038/s41392-020-00430-1 ◽

2021 ◽

Vol 6 (1) ◽

Cited By ~ 1

Author(s):

He-Ming Zhou ◽

Ji-Gang Zhang ◽

Xue Zhang ◽

Qin Li

Keyword(s):

Stem Cells ◽

Cancer Stem Cells ◽

Patient Outcomes ◽

Resistance Mechanism ◽

Therapy Resistance ◽

Resistance Mechanisms ◽

Clinical Perspective ◽

Differentiation Potential ◽

Underlying Processes ◽

Improve Patient

AbstractCancer stem cells (CSCs) show a self-renewal capacity and differentiation potential that contribute to tumor progression and therapy resistance. However, the underlying processes are still unclear. Elucidation of the key hallmarks and resistance mechanisms of CSCs may help improve patient outcomes and reduce relapse by altering therapeutic regimens. Here, we reviewed the identification of CSCs, the intrinsic and extrinsic mechanisms of therapy resistance in CSCs, the signaling pathways of CSCs that mediate treatment failure, and potential CSC-targeting agents in various tumors from the clinical perspective. Targeting the mechanisms and pathways described here might contribute to further drug discovery and therapy.

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PIK3C3 Inhibition Promotes Sensitivity to Colon Cancer Therapy by Inhibiting Cancer Stem Cells

Cancers ◽

10.3390/cancers13092168 ◽

2021 ◽

Vol 13 (9) ◽

pp. 2168

Author(s):

Balawant Kumar ◽

Rizwan Ahmad ◽

Swagat Sharma ◽

Saiprasad Gowrikumar ◽

Mark Primeaux ◽

...

Keyword(s):

Stem Cells ◽

Colon Cancer ◽

Cancer Therapy ◽

Cancer Stem Cells ◽

Side Population ◽

Therapy Resistance ◽

Fluorescent Reporter ◽

Combination Treatments ◽

Gsk 3Β ◽

Resistance To Chemotherapy

Background: Despite recent advances in therapies, resistance to chemotherapy remains a critical problem in the clinical management of colorectal cancer (CRC). Cancer stem cells (CSCs) play a central role in therapy resistance. Thus, elimination of CSCs is crucial for effective CRC therapy; however, such strategies are limited. Autophagy promotes resistance to cancer therapy; however, whether autophagy protects CSCs to promote resistance to CRC-therapy is not well understood. Moreover, specific and potent autophagy inhibitors are warranted as clinical trials with hydroxychloroquine have not been successful. Methods: Colon cancer cells and tumoroids were used. Fluorescent reporter-based analysis of autophagy flux, spheroid and side population (SP) culture, and qPCR were done. We synthesized 36-077, a potent inhibitor of PIK3C3/VPS34 kinase, to inhibit autophagy. Combination treatments were done using 5-fluorouracil (5-FU) and 36-077. Results: The 5-FU treatment induced autophagy only in a subset of the treated colon cancer. These autophagy-enriched cells also showed increased expression of CSC markers. Co-treatment with 36-077 significantly improved efficacy of the 5-FU treatment. Mechanistic studies revealed that combination therapy inhibited GSK-3β/Wnt/β-catenin signaling to inhibit CSC population. Conclusion: Autophagy promotes resistance to CRC-therapy by specifically promoting GSK-3β/Wnt/β-catenin signaling to promote CSC survival, and 36-077, a PIK3C3/VPS34 inhibitor, helps promote efficacy of CRC therapy.

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The plasticity of pancreatic cancer stem cells: implications in therapeutic resistance

Cancer and Metastasis Reviews ◽

10.1007/s10555-021-09979-x ◽

2021 ◽

Author(s):

Kalyani Patil ◽

Farheen B. Khan ◽

Sabah Akhtar ◽

Aamir Ahmad ◽

Shahab Uddin

Keyword(s):

Pancreatic Cancer ◽

Stem Cells ◽

Cancer Stem Cells ◽

Disease Recurrence ◽

Resistance Mechanisms ◽

Cytotoxic Agents ◽

Plastic State ◽

Metastatic Progression ◽

Acquired Drug Resistance ◽

Natural Agents

AbstractThe ever-growing perception of cancer stem cells (CSCs) as a plastic state rather than a hardwired defined entity has evolved our understanding of the functional and biological plasticity of these elusive components in malignancies. Pancreatic cancer (PC), based on its biological features and clinical evolution, is a prototypical example of a CSC-driven disease. Since the discovery of pancreatic CSCs (PCSCs) in 2007, evidence has unraveled their control over many facets of the natural history of PC, including primary tumor growth, metastatic progression, disease recurrence, and acquired drug resistance. Consequently, the current near-ubiquitous treatment regimens for PC using aggressive cytotoxic agents, aimed at ‘‘tumor debulking’’ rather than eradication of CSCs, have proven ineffective in providing clinically convincing improvements in patients with this dreadful disease. Herein, we review the key hallmarks as well as the intrinsic and extrinsic resistance mechanisms of CSCs that mediate treatment failure in PC and enlist the potential CSC-targeting ‘natural agents’ that are gaining popularity in recent years. A better understanding of the molecular and functional landscape of PCSC-intrinsic evasion of chemotherapeutic drugs offers a facile opportunity for treating PC, an intractable cancer with a grim prognosis and in dire need of effective therapeutic advances.

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Genome-wide CRISPR-Cas9 screen identified KLF11 as a druggable suppressor for sarcoma cancer stem cells

Science Advances ◽

10.1126/sciadv.abe3445 ◽

2021 ◽

Vol 7 (5) ◽

pp. eabe3445

Author(s):

Yicun Wang ◽

Jinhui Wu ◽

Hui Chen ◽

Yang Yang ◽

Chengwu Xiao ◽

...

Keyword(s):

Stem Cells ◽

Cancer Stem Cells ◽

Negative Feedback ◽

Direct Interaction ◽

Therapy Resistance ◽

Negative Regulator ◽

Chemotherapy Response ◽

Genome Wide

Cancer stem cells (CSCs) are involved in tumorigenesis, recurrence, and therapy resistance. To identify critical regulators of sarcoma CSCs, we performed a reporter-based genome-wide CRISPR-Cas9 screen and uncovered Kruppel-like factor 11 (KLF11) as top candidate. In vitro and in vivo functional annotation defined a negative role of KLF11 in CSCs. Mechanistically, KLF11 and YAP/TEAD bound to adjacent DNA sites along with direct interaction. KLF11 recruited SIN3A/HDAC to suppress the transcriptional output of YAP/TEAD, which, in turn, promoted KLF11 transcription, forming a negative feedback loop. However, in CSCs, this negative feedback was lost because of epigenetic silence of KLF11, causing sustained YAP activation. Low KLF11 was associated with poor prognosis and chemotherapy response in patients with sarcoma. Pharmacological activation of KLF11 by thiazolidinedione effectively restored chemotherapy response. Collectively, our study identifies KLF11 as a negative regulator in sarcoma CSCs and potential therapeutic target.

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Therapeutic Targeting of Cancer Stem Cells in Lung, Head and Neck, and Bladder Cancers

Cancers ◽

10.3390/cancers13205098 ◽

2021 ◽

Vol 13 (20) ◽

pp. 5098

Author(s):

Sarah E. Mudra ◽

Pritam Sadhukhan ◽

M. Talha Ugurlu ◽

Shorna Alam ◽

Mohammad O. Hoque

Keyword(s):

Stem Cells ◽

Cancer Stem Cells ◽

Acquired Resistance ◽

Therapy Resistance ◽

Stem Cell Population ◽

Molecular Characteristics ◽

Targeted Agents ◽

Regulatory Pathways ◽

Lineage Differentiation ◽

Solid Malignancies

Resistance to cancer therapy remains a significant obstacle in treating patients with various solid malignancies. Exposure to current chemotherapeutics and targeted agents invariably leads to therapy resistance, heralding the need for novel agents. Cancer stem cells (CSCs)—a subpopulation of tumor cells with capacities for self-renewal and multi-lineage differentiation—represent a pool of therapeutically resistant cells. CSCs often share physical and molecular characteristics with the stem cell population of the human body. It remains challenging to selectively target CSCs in therapeutically resistant tumors. The generation of CSCs and induction of therapeutic resistance can be attributed to several deregulated critical growth regulatory signaling pathways such as WNT/β-catenin, Notch, Hippo, and Hedgehog. Beyond growth regulatory pathways, CSCs also change the tumor microenvironment and resist endogenous immune attack. Thus, CSCs can interfere with each stage of carcinogenesis from malignant transformation to the onset of metastasis to tumor recurrence. A thorough review of novel targeted agents to act against CSCs is fundamental for advancing cancer treatment in the setting of both intrinsic and acquired resistance.

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Cancer stem cells - important players in tumor therapy resistance

FEBS Journal ◽

10.1111/febs.13023 ◽

2014 ◽

Vol 281 (21) ◽

pp. 4779-4791 ◽

Cited By ~ 145

Author(s):

Selcuk Colak ◽

Jan P. Medema

Keyword(s):

Stem Cells ◽

Cancer Stem Cells ◽

Tumor Therapy ◽

Therapy Resistance

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Role of Exosomal miRNAs and the Tumor Microenvironment in Drug Resistance

Cells ◽

10.3390/cells9061450 ◽

2020 ◽

Vol 9 (6) ◽

pp. 1450 ◽

Cited By ~ 3

Author(s):

Patrick Santos ◽

Fausto Almeida

Keyword(s):

Stem Cells ◽

Drug Resistance ◽

Tumor Microenvironment ◽

Cancer Stem Cells ◽

Cancer Cells ◽

Extracellular Vesicles ◽

Therapy Resistance ◽

Chemotherapeutic Agents ◽

Exosomal Mirnas ◽

Key Factor

Tumor microenvironment (TME) is composed of different cellular populations, such as stromal, immune, endothelial, and cancer stem cells. TME represents a key factor for tumor heterogeneity maintenance, tumor progression, and drug resistance. The transport of molecules via extracellular vesicles emerged as a key messenger in intercellular communication in the TME. Exosomes are small double-layered lipid extracellular vesicles that can carry a variety of molecules, including proteins, lipids, and nucleic acids. Exosomal miRNA released by cancer cells can mediate phenotypical changes in the cells of TME to promote tumor growth and therapy resistance, for example, fibroblast- and macrophages-induced differentiation. Cancer stem cells can transfer and enhance drug resistance in neighboring sensitive cancer cells by releasing exosomal miRNAs that target antiapoptotic and immune-suppressive pathways. Exosomes induce drug resistance by carrying ABC transporters, which export chemotherapeutic agents out of the recipient cells, thereby reducing the drug concentration to suboptimal levels. Exosome biogenesis inhibitors represent a promising adjunct therapeutic approach in cancer therapy to avoid the acquisition of a resistant phenotype. In conclusion, exosomal miRNAs play a crucial role in the TME to confer drug resistance and survivability to tumor cells, and we also highlight the need for further investigations in this promising field.

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