Self-Renewal Signalling Pathway Inhibitors: Perspectives on Therapeutic Approaches for Cancer Stem Cells

Key roles of ubiquitination in regulating critical regulators of cancer stem cell functionality

The ubiquitin (Ub) system, a ubiquitous presence across eukaryotes, plays a crucial role in the precise orchestration of diverse cellular protein processes. From steering cellular signaling pathways and orchestrating cell cycle progression to guiding receptor trafficking and modulating immune responses, this process plays a crucial role in regulating various biological functions. The dysregulation of Ub-mediated signaling pathways in prevalent cancers ushers in a spectrum of clinical outcomes ranging from tumorigenesis and metastasis to recurrence and drug resistance. Ubiquitination, a linchpin process mediated by Ub, assumes a central mantle in molding cellular signaling dynamics. It navigates transitions in biological cues and ultimately shapes the destiny of proteins. Recent years have witnessed an upsurge in the momentum surrounding the development of protein-based therapeutics aimed at targeting the Ub system under the sway of cancer stem cells. The article provides a comprehensive overview of the ongoing in-depth discussions regarding the regulation of the Ub system and its impact on the development of cancer stem cells. Amidst the tapestry of insights, the article delves into the expansive roles of E3 Ub ligases, deubiquitinases, and transcription factors entwined with cancer stem cells. Furthermore, the spotlight turns to the interplay with pivotal signaling pathways the Notch, Hedgehog, Wnt/β-catenin, and Hippo-YAP signaling pathways all play crucial roles in the regulation of cancer stem cells followed by the specific modulation of Ub-proteasome.

Deciphering the Role of Cancer Stem Cells: Drivers of Tumor Evolution, Therapeutic Resistance, and Precision Medicine Strategies

Cancer stem cells (CSCs) play a central role in tumor progression, recurrence, and resistance to conventional therapies, making them a critical focus in oncology research. This review provides a comprehensive analysis of CSC biology, emphasizing their self-renewal, differentiation, and dynamic interactions with the tumor microenvironment (TME). Key signaling pathways, including Wnt, Notch, and Hedgehog, are discussed in detail to highlight their potential as therapeutic targets. Current methodologies for isolating CSCs are critically examined, addressing their advantages and limitations in advancing precision medicine. Emerging technologies, such as CRISPR/Cas9 and single-cell sequencing, are explored for their transformative potential in unraveling CSC heterogeneity and informing therapeutic strategies. The review also underscores the pivotal role of the TME in supporting CSC survival, promoting metastasis, and contributing to therapeutic resistance. Challenges arising from CSC-driven tumor heterogeneity and dormancy are analyzed, along with strategies to mitigate these barriers, including novel therapeutics and targeted approaches. Ethical considerations and the integration of artificial intelligence in designing CSC-specific therapies are discussed as essential elements of future research. The manuscript advocates for a multi-disciplinary approach that combines innovative technologies, advanced therapeutics, and collaborative research to address the complexities of CSCs. By bridging existing gaps in knowledge and fostering advancements in personalized medicine, this review aims to guide the development of more effective cancer treatment strategies, ultimately improving patient outcomes.

SLC7A11 Inhibitors Represent a Promising Therapeutic Target by Facilitating the Induction of Ferroptosis in Breast Cancer

It is predicted with near certainty that an estimated 310,720 women will be diagnosed with invasive breast carcinoma in 2024, while the number of men will be significantly lower at around 2,800, highlighting the alarming prevalence of this cancer across the sexes. The Solute Carrier Family 7 Member 11(SLC7A11) gene is vital for the exchange of extracellular cystine for glutamate at a 1:1 ratio and its expression is significantly increased in various tumors. Numerous research studies have shown that SLC7A11 expression is fine-tuned at several levels, contributing to its pharmacological functions in tumors, such as maintaining cellular redox balance, promoting cell proliferation, and influencing ferroptosis. Many studies suggest that reducing SLC7A11 expression and activity may be beneficial for cancer treatment, making it a promising target for therapy. However, recent findings also suggest that inhibiting SLC7A11 in certain scenarios may increase the survival of cancer cells and promote drug resistance. This review begins with a brief overview of the properties of SLC7A11, including its structural features and physiological functions, followed by a summary of its potential regulators. We then delve deeper into its role in cancer, particularly breast cancer, and explore the relationships between SLC7A11 and ferroptosis, proliferation, metastasis, and therapeutic resistance. Consequently, more customized therapeutic approaches should be considered when targeting SLC7A11 in the context of breast cancer. Thus, high expression of SLC7A11 is associated with poor prognosis in breast cancer, and various inhibitors have been identified that can effectively target this transporter. Innovative therapeutic strategies, including immunotherapies targeting SLC7A11, can potentially reduce tumor growth and metastasis in breast cancer models.

Boric Acid Affects the Expression of DNA Double-Strand Break Repair Factors in A549 Cells and A549 Cancer Stem Cells: An In Vitro Study

DNA double-strand break (DSB) repair genes interact with tumor stemness- and resistance-associated processes in cancer stem cells (CSCs). Therefore, targeting DNA DSB genes in cancer treatment is important for the CSC phenotype. Although the anti-cancer effect of boric acid (BA) has been studied, its effect on DNA DSB is unclear. Moreover, no studies investigate BA's effects on DNA DSB of lung cancer stem cells (LC-SCs). To fill the gap, we aimed to assess the effects of BA on A549 cancer stem cells. CSCs were isolated from human non-small cell lung cancer cells (A549) and characterized by flow cytometry. Different concentrations of BA (at doses ranging from 1 to 100 mM) were applied to cancer stem cells. Cytotoxic activities were determined using the cell viability assay (MTT assay) at 24 and 48 h. Expression levels of DNA DSB genes that BRCA1, BRCA2, RAD51, KU70/80, ATM, and XRCC4 were evaluated by RT-qPCR. Additionally, immunofluorescence staining analysis was exploited for caspase-3 and E-cadherin. ATM expression increased significantly (p < 0.001). No significant change was observed in the expression of other genes. Moreover, BA up-regulated caspase-3 and E-cadherin expression. Consequently, we can say that BA affects DNA DSB and the apoptotic abilities of LC-SCs.

Unravelling the Mysteries of the Sonic Hedgehog Pathway in Cancer Stem Cells: Activity, Crosstalk and Regulation

The Sonic Hedgehog (Shh) signalling pathway plays a critical role in normal development and tissue homeostasis, guiding cell differentiation, proliferation, and survival. Aberrant activation of this pathway, however, has been implicated in the pathogenesis of various cancers, largely due to its role in regulating cancer stem cells (CSCs). CSCs are a subpopulation of cancer cells with the ability to self-renew, differentiate, and initiate tumour growth, contributing significantly to tumorigenesis, recurrence, and resistance to therapy. This review focuses on the intricate activity of the Shh pathway within the context of CSCs, detailing the molecular mechanisms through which Shh signalling influences CSC properties, including self-renewal, differentiation, and survival. It further explores the regulatory crosstalk between the Shh pathway and other signalling pathways in CSCs, highlighting the complexity of this regulatory network. Here, we delve into the upstream regulators and downstream effectors that modulate Shh pathway activity in CSCs. This review aims to cast a specific focus on the role of the Shh pathway in CSCs, provide a detailed exploration of molecular mechanisms and regulatory crosstalk, and discuss current and developing inhibitors. By summarising key findings and insights gained, we wish to emphasise the importance of further elucidating the interplay between the Shh pathway and CSCs to develop more effective cancer therapies.

Dynamic interplay of nuclear receptors in tumor cell plasticity and drug resistance: Shifting gears in malignant transformations and applications in cancer therapeutics

Recent advances have brought forth the complex interplay between tumor cell plasticity and its consequential impact on drug resistance and tumor recurrence, both of which are critical determinants of neoplastic progression and therapeutic efficacy. Various forms of tumor cell plasticity, instrumental in facilitating neoplastic cells to develop drug resistance, include epithelial-mesenchymal transition (EMT) alternatively termed epithelial-mesenchymal plasticity, the acquisition of cancer stem cell (CSC) attributes, and transdifferentiation into diverse cell lineages. Nuclear receptors (NRs) are a superfamily of transcription factors (TFs) that play an essential role in regulating a multitude of cellular processes, including cell proliferation, differentiation, and apoptosis. NRs have been implicated to play a critical role in modulating gene expression associated with tumor cell plasticity and drug resistance. This review aims to provide a comprehensive overview of the current understanding of how NRs regulate these key aspects of cancer biology. We discuss the diverse mechanisms through which NRs influence tumor cell plasticity, including EMT, stemness, and metastasis. Further, we explore the intricate relationship between NRs and drug resistance, highlighting the impact of NR signaling on chemotherapy, radiotherapy and targeted therapies. We also discuss the emerging therapeutic strategies targeting NRs to overcome tumor cell plasticity and drug resistance. This review also provides valuable insights into the current clinical trials that involve agonists or antagonists of NRs modulating various aspects of tumor cell plasticity, thereby delineating the potential of NRs as therapeutic targets for improved cancer treatment outcomes.

Progress in Glioma Stem Cell Research

Glioblastoma multiforme (GBM) represents a diverse spectrum of primary tumors notorious for their resistance to established therapeutic modalities. Despite aggressive interventions like surgery, radiation, and chemotherapy, these tumors, due to factors such as the blood-brain barrier, tumor heterogeneity, glioma stem cells (GSCs), drug efflux pumps, and DNA damage repair mechanisms, persist beyond complete isolation, resulting in dismal outcomes for glioma patients. Presently, the standard initial approach comprises surgical excision followed by concurrent chemotherapy, where temozolomide (TMZ) serves as the foremost option in managing GBM patients. Subsequent adjuvant chemotherapy follows this regimen. Emerging therapeutic approaches encompass immunotherapy, including checkpoint inhibitors, and targeted treatments, such as bevacizumab, aiming to exploit vulnerabilities within GBM cells. Nevertheless, there exists a pressing imperative to devise innovative strategies for both diagnosing and treating GBM. This review emphasizes the current knowledge of GSC biology, molecular mechanisms, and associations with various signals and/or pathways, such as the epidermal growth factor receptor, PI3K/AKT/mTOR, HGFR/c-MET, NF-κB, Wnt, Notch, and STAT3 pathways. Metabolic reprogramming in GSCs has also been reported with the prominent activation of the glycolytic pathway, comprising aldehyde dehydrogenase family genes. We also discuss potential therapeutic approaches to GSC targets and currently used inhibitors, as well as their mode of action on GSC targets.

Lysine Demethylase KDM2A Promotes Proteasomal Degradation of TCF/LEF Transcription Factors in a Neddylation-Dependent Manner

Canonical Wnt signaling is essential for a plethora of biological processes ranging from early embryogenesis to aging. Malfunctions of this crucial signaling pathway are associated with various developmental defects and diseases, including cancer. Although TCF/LEF transcription factors (TCF/LEFs) are known to be essential for this pathway, the regulation of their intracellular levels is not completely understood. Here, we show that the lysine demethylase KDM2A promotes the proteasomal destabilization of TCF/LEFs independently of its demethylase domain. We found that the KDM2A-mediated destabilization of TCF/LEFs is dependent on the KDM2A zinc finger CXXC domain. Furthermore, we identified the C-terminal region of TCF7L2 and the CXXC domain of KDM2A as the domains responsible for the interaction between the two proteins. Our study is also the first to show that endogenous TCF/LEF proteins undergo KDM2A-mediated proteasomal degradation in a neddylation-dependent manner. Here, we reveal a completely new mechanism that affects canonical Wnt signaling by regulating the levels of TCF/LEF transcription factors through their KDM2A-promoted proteasomal degradation.

High-fat diet intake ameliorates the expression of hedgehog signaling pathway in adult rat liver

BACKGROUND

Disproportionate fatty diet intake provokes hepatic lipid accumulation that causes non-alcoholic fatty liver disease, triggering the embryonically conserved Hedgehog (Hh) pathway in the adult liver. The present study incorporates exploring the impact of chronically administered unsaturated (D-1) and saturated (D-2) fat-enriched diets on hematological parameters, liver functioning, and lipid profile in the rat model. Besides, hepatohistology and real time gene expression analysis of Hh signaling pathway genes i.e., Shh, Ihh, Hhip, Ptch1, Smo, Gli1, Gli2, and Gli3 were carried out.

METHODS AND RESULTS

Fifteen Rattus norvegicus (♂) of 200 ± 25 g weight were grouped into control, D-1, and D-2. Animals were fed on their respective diets for 16 weeks. Fatty diet intake resulted in neutropenia, lymphocytosis, monocytosis, polycythemia, and macrocytosis in both experimental groups. Altered liver injury biomarkers, hypertriglyceridemia, and significantly increased very-low-density lipoprotein VLDL were also noted in both high-fat diet (HFD) groups as compared to control. Hepatohistological examination showed disrupted microarchitecture, infiltration of inflammatory cells, cellular necrosis, widened sinusoidal spaces, and microvesicular steatotic hepatocytes in D-1 and D-2. Collagen deposition in both HFD groups marks the extent of fibrosis. Significant upregulation of hedgehog pathway genes was found in fatty diet groups. In comparison with the control group, Shh Ihh, Hhip, Ptch1, Smo, Gli1, Gli2, and Gli3 were upregulated in D-1. In D-2 Shh, Hhip, and Smo expressions were upregulated, Ihh exhibited downregulation as compared to control.

CONCLUSION

Excess fat deposits in liver due to chronic consumption of high-fat diet results in anomalous architecture and functioning. High-fat diet induced significant variations in Hh pathway genes expression; especially Shh, Ihh, Hhip, Ptch1, Smo, Gli1, Gli2, and Gli3 were upregulated. Infiltration of inflammatory cells ( ), widened sinusoidal spaces (▲), cellular necrosis, and micro vesicular steatotic hepatocytes (*) were shown in the liver. Significant collagen deposition in both HFD groups i.e. D-1 and D-2 confirmed liver fibrosis. Excessive intake of dietary fats impaired normal liver functioning and liver inflammation triggered Hh signaling in adult rats.

Targeting the IGF-1R in prostate and colorectal cancer: reasons behind trial failure and future directions

IGF-1Rs enact a significant part in cancer growth and its progress. IGF-1R inhibitors were encouraged in the early trials, but the patients did not benefit due to the unavailability of predictive biomarkers and IGF-1R system complexity. However, the linkage between IGF-1R and cancer was reported three decades ago. This review will shed light on the IGF-1R system, targeting IGF-1R through monoclonal antibodies, reasons behind IGF-1R trial failure and future directions. This study presented that targeting IGF-1R through monoclonal antibodies is still effective in cancer treatment, and there is a need to look for future directions. Cancer patients may benefit from using mAbs that target existing and new cancer targets, evidenced by promising results. It is also essential that the academician, trial experts and pharmaceutical companies play their role in finding a treatment for this deadly disease.

Metal complexes against breast cancer stem cells

With the highest incidence, breast cancer is the leading cause of cancer deaths among women in the world. Tumor metastasis is the major contributor of high mortality in breast cancer, and the existence of cancer stem cells (CSCs) has been proven to be the cause of tumor metastasis. CSCs are a small proportion of tumor cells, and they are associated with self-renewal and tumorigenic potential. Given the significance of CSCs in tumor initiation, expansion, relapse, resistance, and metastasis, studies should investigate and discover effective anticancer agents that can not only inhibit the proliferation of differentiated tumor cells but also reduce the tumorigenic capability of CSCs. Thus, new therapies must be discovered to treat and prevent this severely hazardous disease of human beings. The success of platinum complexes in cancer treatment has laid the basic foundation for the utilization of metal complexes in the treatment of malignant cancers, in particular the highly aggressive triple-negative breast cancer. Importantly, metal complexes currently have diverse and versatile competences in the therapeutic targeting of CSCs. The anti-CSC properties provide a strong impetus for the development of novel metal-based compounds for the targeting of CSCs and treatment of chemotherapy-resistant and relapsed tumors. In this review, we provide the latest advances in metal complexes including platinum, ruthenium, osmium, iridium, manganese, cobalt, nickel, copper, zinc, palladium, and tin complexes against breast CSCs obtained over the past decade, with pertinent literature including those published until 2021.

Ellagitannins, promising pharmacological agents for the treatment of cancer stem cells

Human tumors comprise subpopulations of cells called cancer stem cells (CSCs) that possess stemness properties. CSCs can initiate tumors and cause recurrence, metastasis and are also responsible for chemo- and radio-resistance. CSCs may use signaling pathways similar to normal stem cells, including Notch, JAK/STAT, Wnt and Hedgehog pathways. Ellagitannins (ETs) are a broad group of substances with chemopreventive and anticancer activities. The antitumor activity of ETs and their derivatives are mainly related to their antiinflammatory capacity. They are therefore able to modulate secretory growth factors and pro-inflammatory mediators such as IL-6, TGF-β, TNF-α, IL-1β and IFN-γ. Evidence suggests that ETs display their anticancer effect by targeting CSCs and disrupting stem cell signaling. However, there are still few studies in this field. Therefore, high-quality studies are needed to firmly establish the clinical efficacy of the ETs on CSCs. This paper reviews the structures, sources and pharmacokinetics of ETs. It also focuses on the function of ETs and their effects on CSCs-related cytokines and the relationship between ETs and signaling pathways in CSCs.

Piperine Targets Different Drug Resistance Mechanisms in Human Ovarian Cancer Cell Lines Leading to Increased Sensitivity to Cytotoxic Drugs

Our goal was to examine the anticancer effects of piperine against the resistant human ovarian cancer cells and to explore the molecular mechanisms responsible for its anticancer effects. Our study used drug-sensitive ovarian cancer cell line W1 and its sublines resistant to paclitaxel (PAC) and topotecan (TOP). We analyzed the cytotoxic effect of piperine and cytostatic drugs using an MTT assay. The impact of piperine on protein expression was determined by immunofluorescence and Western blot. We also examined its effect on cell proliferation and migration. We noticed a different level of piperine resistance between cell lines. Piperine increases the cytotoxic effect of PAC and TOP in drug-resistant cells. We observed an increase in PTPRK expression correlated with decreased pTYR level after piperine treatment and downregulation of P-gp and BCRP expression. We also noted a decrease in COL3A1 and TGFBI expression in investigated cell lines and increased COL3A1 expression in media from W1PR2 cells. The expression of Ki67 protein and cell proliferation rate decreased after piperine treatment. Piperine markedly inhibited W1TR cell migration. Piperine can be considered a potential anticancer agent that can increase chemotherapy effectiveness in cancer patients.

Signaling pathways governing breast cancer stem cells behavior

Breast cancer is the second common cancer and the leading cause of malignancy among females overall. Breast cancer stem cells (BCSCs) are a small population of breast cancer cells that play a critical role in the metastasis of breast cancer to other organs in the body. BCSCs have both self-renewal and differentiation capacities, which are thought to contribute to the aggressiveness of metastatic lesions. Therefore, targeting BCSCs can be a suitable approach for the treatment and metastasis of breast cancer. Growing evidence has indicated that the Wnt, NFκB, Notch, BMP2, STAT3, and hedgehog (Hh) signaling pathways govern epithelial-to-mesenchymal transition (EMT) activation, growth, and tumorigenesis of BCSCs in the primary regions. miRNAs as the central regulatory molecules also play critical roles in BCSC self-renewal, metastasis, and drug resistance. Hence, targeting these pathways might be a novel therapeutic approach for breast cancer diagnosis and therapy. This review discusses known signaling mechanisms involved in the stimulation or prevention of BCSC self-renewal, metastasis, and tumorigenesis.

Short overview on the relevance of microRNA-reactive oxygen species (ROS) interactions and lipid peroxidation for modulation of oxidative stress-mediated signalling pathways in cancer treatment

OBJECTIVES

Modulation of oxidative stress-mediated signalling pathways is constantly getting more attention as a valuable therapeutic strategy in cancer treatment. Although complexity of redox signalling pathways might represent a major hurdle, the development of advanced -omics technologies allow thorough studies on cancer-specific biology, which is essential to elucidate the impact of these signalling pathways in cancer cells. The scope of our review is to provide updated information about recent developments in cancer treatment.

KEY FINDINGS

In recent years identifying oxidative stress-mediated signalling pathways is a major goal of cancer research assuming it may provide novel therapeutic approaches through the development of agents that may have better tissue penetration and therefore affect specific redox signalling pathways. In this review, we discuss some recent studies focussed on the modulation of oxidative stress-related signalling pathways as a novel anti-cancer treatment, with a particular emphasis on the induction of lipid peroxidation.

CONCLUSIONS

Characterization and modulation of oxidative stress-mediated signalling pathways and lipid peroxidation products will continue to foster novel interest and further investigations, which may pave the way for more effective, selective, and personalized integrative biomedicine treatment strategies.

Notch Signaling Pathway in Pancreatobiliary Tumors

Background and Objectives: The Notch signaling pathway plays an important role both in the development of the ductal systems of the pancreas and the bile ducts as well as in cancer development and progression. The aim of this study was to examine the expression of central proteins of the Notch signaling pathway in pancreatobiliary tumors and its influence on patient survival. Materials and Methods: We compared the receptors (Notch1, Notch4), activating splicing factors (ADAM17), and target genes (HES1) of the Notch pathway and progenitor cell markers with relevance for the Notch signaling pathway (CD44, MSI1) between pancreatic adenocarcinomas (PDAC, n = 14), intrahepatic cholangiocarcinoma (iCC, n = 24), and extrahepatic cholangiocarcinoma (eCC, n = 22) cholangiocarcinomas via immunohistochemistry and ImageJ software-assisted analysis. An Immunohistochemistry (IHC)-score was determined by the percentage and intensity of stained (positive) cells (scale 0–7) and normal and malignant tissue was compared. In the IHC results, patients’ (gender, age) and tumor (TNM Classification of Malignant Tumors, Union Internationale contre le Cancer (UICC) stages, grading, and lymphangitic carcinomatosa) characteristics were correlated to patient survival. Results: For eCC, the expression of CD44 (p = 0.043, IHC-score 3.94 vs. 3.54) and for iCC, the expression of CD44 (p = 0.026, IHC-score 4.04 vs. 3.48) and Notch1 (p < 0.001, IHC-score 2.87 vs. 1.78) was significantly higher in the tumor compared to non-malignant tissue. For PDAC, the expression of ADAM17 (p = 0.008, IHC-score 3.43 vs. 1.73), CD44 (p = 0.012, IHC-score 3.64 vs. 2.27), Notch1 (p = 0.012, IHC-score 2.21 vs. 0.64), and Notch4 (p = 0.008, IHC-score 2.86 vs. 0.91) was significantly higher in the tumor tissue. However, none of the analyzed Notch-signaling related components showed an association to patient survival. Conclusion: A significant overexpression of almost all studied components of the Notch signaling pathway can be found in the tumor tissue, however, without a significant influence on patient survival. Therefore, further studies are warranted to draw conclusions on Notch pathway’s relevance for patient survival.

Cancer Stem Cell (CSC) Inhibitors in Oncology-A Promise for a Better Therapeutic Outcome: State of the Art and Future Perspectives

Cancer stem cells (CSCs), a subpopulation of cancer cells endowed with self-renewal, tumorigenicity, pluripotency, chemoresistance, differentiation, invasive ability, and plasticity, reside in specialized tumor niches and are responsible for tumor maintenance, metastasis, therapy resistance, and tumor relapse. The new-age "hierarchical or CSC" model of tumor heterogeneity is based on the concept of eradicating CSCs to prevent tumor relapse and therapy resistance. Small-molecular entities and biologics acting on various stemness signaling pathways, surface markers, efflux transporters, or components of complex tumor microenvironment are under intense investigation as potential anti-CSC agents. In addition, smart nanotherapeutic tools have proved their utility in achieving CSC targeting. Several CSC inhibitors in clinical development have shown promise, either as mono- or combination therapy, in refractory and difficult-to-treat cancers. Clinical investigations with CSC marker follow-up as a measure of clinical efficacy are needed to turn the "hype" into the "hope" these new-age oncology therapeutics have to offer.

Dysregulation of Stemness Pathways in HPV Mediated Cervical Malignant Transformation Identifies Potential Oncotherapy Targets

Human papillomavirus (HPV) infection is associated with a range of malignancies that affect anogenital and oropharyngeal sites. α-HPVs dominantly infect basal epithelial cells of mucosal tissues, where they dysregulate cell division and local immunity. The cervix is one of the mucosal sites most susceptible to HPV infections. It consists of anatomically diverse regions, and the majority of cervical intraepithelial neoplasia and cancers arise within the cervical squamo-columnar junction where undifferentiated basal progenitor cells with stem cell properties are found. The cancer stem cell theory particularly associates tumorigenesis, invasion, dissemination, and metastasis with cancer cells exhibiting stem cell properties. In this perspective, we discuss evidence of a cervical cancer stem cell niche and explore the association of stemness related genes with 5-year survival using a publicly available transcriptomic dataset of a cervical cancer cohort. We report that poor prognosis in this cohort correlates with overexpression of a subset of stemness pathway genes, a majority of which regulate the central Focal Adhesion pathway, and are also found to be enriched in the HPV infection pathway. These observations support therapeutic targeting of stemness genes overexpressed by mucosal cells infected with high-risk HPVs.

Emerging agents that target signaling pathways in cancer stem cells

Cancer stem cells (CSCs) contribute to the initiation, recurrence, and metastasis of cancer; however, there are still no drugs targeting CSCs in clinical application. There are several signaling pathways playing critical roles in CSC progression, such as the Wnt, Hedgehog, Notch, Hippo, and autophagy signaling pathways. Additionally, targeting the ferroptosis signaling pathway was recently shown to specifically kill CSCs. Therefore, targeting these pathways may suppress CSC progression. The structure of small-molecule drugs shows a good spatial dispersion, and its chemical properties determine its good druggability and pharmacokinetic properties. These characteristics make small-molecule drugs show a great advantage in drug development, which is increasingly popular in the market. Thus, in this review, we will summarize the current researches on the small-molecule compounds suppressing CSC progression, including inhibitors of Wnt, Notch, Hedgehog, and autophagy pathways, and activators of Hippo and ferroptosis pathways. These small-molecule compounds emphasize CSC importance in tumor progression and propose a new strategy to treat cancer in clinic via targeting CSCs.