Acquisition of tumorigenic potential and therapeutic resistance in CD133+ subpopulation of prostate cancer cells exhibiting stem-cell like characteristics

Translating preclinical insights into clinical strategies: Targeting cancer stem cells and stemness in prostate cancer

CSCs represent a unique group within the tumor microenvironment (TME) elevating the tumorigenesis. The cause of cancer recurrence can also be investigated in the function of CSCs possessing self-renewing capabilities and differentiation into various types of cells. Prostate cancer (PCa) is a malignant disease of the urogenital system characterized by aggressive behavior and heterogeneous nature due to the dysregulation of molecular pathways and the interactions among cells within the TME. The PCa can quickly become resistant to standard chemotherapy and other kinds of therapies such as radiotherapy along with ability to mediate immune evasion. The focus of biology has been on the molecular and cellular alterations in PCa. The CSCs have been recognized as potential biomarkers for predicting the outcome of prostate PCa. Furthermore, a positive correlation exists between CSCs and the metastatic growth and stemness of PCa. The existence of hypoxia enhances the stemness of PCa, and CSCs play a role in dormancy. Genomic and epigenetic elements, including non-coding RNAs, can influence CSCs and the advancement of PCa. Additionally, therapeutic agents and nanotechnology methods aimed at targeting CSCs have been developed to inhibit CSCs in PCa treatment.

Integrative Chinese-Western medicine strategy to overcome docetaxel resistance in prostate cancer

ETHNOPHARMACOLOGICAL RELEVANCE

Traditional Chinese Medicines (TCMs) have emerged as a promising complementary therapy in the management of prostate cancer (PCa), particularly in addressing resistance to Docetaxel (DTX) chemotherapy.

AIM OF THE REVIEW

This review aims to elucidate the mechanisms underlying the development of resistance to DTX in PCa and explore the innovative approach of integrating TCMs in PCa treatment to overcome this resistance. Key areas of investigation include alterations in microtubule proteins, androgen receptor and androgen receptor splice variant 7, ERG rearrangement, drug efflux mechanisms, cancer stem cells, centrosome clustering, upregulation of the PI3K/AKT signaling pathway, enhanced DNA damage repair capability, and the involvement of neurotrophin receptor 1/protein kinase C.

MATERIALS AND METHODS

With "Prostate cancer", "Docetaxel", "Docetaxel resistance", "Natural compounds", "Traditional Chinese medicine", "Traditional Chinese medicine compound", "Medicinal plants" as the main keywords, PubMed, Web of Science and other online search engines were used for literature retrieval.

RESULTS

Our findings underscore the intricate interplay of molecular alterations that collectively contribute to the resistance of PCa cells to DTX. Moreover, we highlight the potential of TCMs as a promising complementary therapy, showcasing their ability to counteract DTX resistance and enhance therapeutic efficacy.

CONCLUSION

The integration of TCMs in PCa treatment emerges as an innovative approach with significant potential to overcome DTX resistance. This review not only provides insights into the mechanisms of resistance but also presents new prospects for improving the clinical outcomes of patients with PCa undergoing DTX therapy. The comprehensive understanding of these mechanisms lays the foundation for future research and the development of more effective therapeutic interventions.

Exploiting Matrix Stiffness to Overcome Drug Resistance

Drug resistance is arguably one of the biggest challenges facing cancer research today. Understanding the underlying mechanisms of drug resistance in tumor progression and metastasis are essential in developing better treatment modalities. Given the matrix stiffness affecting the mechanotransduction capabilities of cancer cells, characterization of the related signal transduction pathways can provide a better understanding for developing novel therapeutic strategies. In this review, we aimed to summarize the recent advancements in tumor matrix biology in parallel to therapeutic approaches targeting matrix stiffness and its consequences in cellular processes in tumor progression and metastasis. The cellular processes governed by signal transduction pathways and their aberrant activation may result in activating the epithelial-to-mesenchymal transition, cancer stemness, and autophagy, which can be attributed to drug resistance. Developing therapeutic strategies to target these cellular processes in cancer biology will offer novel therapeutic approaches to tailor better personalized treatment modalities for clinical studies.

Extracellular vesicles and cancer stem cells: a deadly duo in tumor progression

The global incidence of cancer is increasing, with estimates suggesting that there will be 26 million new cases and 17 million deaths per year by 2030. Cancer stem cells (CSCs) and extracellular vesicles (EVs) are key to the resistance and advancement of cancer. They play a crucial role in tumor dynamics and resistance to therapy. CSCs, initially discovered in acute myeloid leukemia, are well-known for their involvement in tumor initiation, progression, and relapse, mostly because of their distinct characteristics, such as resistance to drugs and the ability to self-renew. EVs, which include exosomes, microvesicles, and apoptotic bodies, play a vital role in facilitating communication between cells within the tumor microenvironment (TME). They have a significant impact on cellular behaviors and contribute to genetic and epigenetic changes. This paper analyzes the mutually beneficial association between CSCs and EVs, emphasizing their role in promoting tumor spread and developing resistance mechanisms. This review aims to investigate the interaction between these entities in order to discover new approaches for attacking the complex machinery of cancer cells. It highlights the significance of CSCs and EVs as crucial targets in the advancement of novel cancer treatments, which helps stimulate additional research, promote progress in ideas for cancer treatment, and provide renewed optimism in the effort to reduce the burden of cancer.

Cancer-associated fibroblasts and prostate cancer stem cells: crosstalk mechanisms and implications for disease progression

The functional heterogeneity and ecological niche of prostate cancer stem cells (PCSCs), which are major drivers of prostate cancer development and treatment resistance, have attracted considerable research attention. Cancer-associated fibroblasts (CAFs), which are crucial components of the tumor microenvironment (TME), substantially affect PCSC stemness. Additionally, CAFs promote PCSC growth and survival by releasing signaling molecules and modifying the surrounding environment. Conversely, PCSCs may affect the characteristics and behavior of CAFs by producing various molecules. This crosstalk mechanism is potentially crucial for prostate cancer progression and the development of treatment resistance. Using organoids to model the TME enables an in-depth study of CAF-PCSC interactions, providing a valuable preclinical tool to accurately evaluate potential target genes and design novel treatment strategies for prostate cancer. The objective of this review is to discuss the current research on the multilevel and multitarget regulatory mechanisms underlying CAF-PCSC interactions and crosstalk, aiming to inform therapeutic approaches that address challenges in prostate cancer treatment.

Cancer stem cells: advances in knowledge and implications for cancer therapy

Cancer stem cells (CSCs), a small subset of cells in tumors that are characterized by self-renewal and continuous proliferation, lead to tumorigenesis, metastasis, and maintain tumor heterogeneity. Cancer continues to be a significant global disease burden. In the past, surgery, radiotherapy, and chemotherapy were the main cancer treatments. The technology of cancer treatments continues to develop and advance, and the emergence of targeted therapy, and immunotherapy provides more options for patients to a certain extent. However, the limitations of efficacy and treatment resistance are still inevitable. Our review begins with a brief introduction of the historical discoveries, original hypotheses, and pathways that regulate CSCs, such as WNT/β-Catenin, hedgehog, Notch, NF-κB, JAK/STAT, TGF-β, PI3K/AKT, PPAR pathway, and their crosstalk. We focus on the role of CSCs in various therapeutic outcomes and resistance, including how the treatments affect the content of CSCs and the alteration of related molecules, CSCs-mediated therapeutic resistance, and the clinical value of targeting CSCs in patients with refractory, progressed or advanced tumors. In summary, CSCs affect therapeutic efficacy, and the treatment method of targeting CSCs is still difficult to determine. Clarifying regulatory mechanisms and targeting biomarkers of CSCs is currently the mainstream idea.

Identification of placenta-specific protein 1 (PLAC-1) expression on human PC-3 cell line-derived prostate cancer stem cells compared to the tumor parental cells

Placenta-specific protein 1 (PLAC-1) is a gene primarily expressed in the placenta and the testis. Interestingly, it is also found to be expressed in many solid tumors, and it is involved in malignant cell features. However, no evidence has been reported regarding the relationship between PLAC-1 and cancer stem cells (CSCs). In the current research, we explored the expression of the PLAC-1 molecule in prostate cancer stem cells (PCSCs) derived from the human PC-3 cell line. The enrichment of PCSCs was achieved using a three-dimensional cell culture technique known as the sphere-formation assay. To confirm the identity of PCSCs, we examined the expression of genes associated with stemness and pluripotency, such as SOX2, OCT4, Nanog, C-Myc, and KLF-4, as well as stem cell differentiation molecules like CD44 and CD133. These evaluations were conducted in both the PCSCs and the original tumor cells (parental cells) using real-time PCR and flow cytometry. Subsequently, we assessed the expression of the PLAC-1 molecule in both enriched cells and parental tumor cells at the gene and protein levels using the same techniques. The tumor cells from the PC-3 cell line formed spheroids with CSC characteristics in a non-adherent medium. The expression of SOX2, OCT4, Nanog, and C-Myc genes (p < 0.01), and the molecules CD44 and CD133 (p < 0.05) were significantly elevated in PCSCs compared to the parental cells. The expression of the PLAC-1 molecule in PCSCs showed a significant increase compared to the parental cells at both gene (p < 0.01) and protein (p < 0.001) levels. In conclusion, it was indicated for the first time that PLAC-1 is up-regulated in PCSCs derived from human PC-3 cell line. This study may propose PLAC-1 as a potential target in targeted therapies, which should be confirmed through further studies.

CD44 and CD133 protein expression might serve as a prognostic factor for early occurrence castration-resistant prostate cancer

BACKGROUND

The occurrence of castration-resistant prostate cancer (CRPC) varies in patients with advanced prostate cancer (PCa) undergoing androgen deprivation therapy (ADT). The rate of occurrence of CRPC may be related to the presence of prostate cancer stem cells (CSC). Thus, this study aims to evaluate the presence of CSC markers (CD44 and CD133) in histopathology tissue at the time of diagnosis and their correlation with the occurrence of CRPC in patients with advanced PCa within 2 years of ADT.

METHOD

A retrospective case-control study was conducted to evaluate the incidence of CRPC within 2 years. The inclusion criteria were patients with PCa who had received treatment with ADT and a first-generation anti-androgen (AA) for 2 years. We classified patients based on whether they developed CRPC within 2 years (CRPC) of the therapy or did not experience CRPC within 2 years (non-CRPC) of the therapy. We performed immunohistochemical (IHC) staining for CD44 and CD133 on the prostate biopsy tissue samples.

RESULTS

Data were collected from records spanning 2011-2019. We analyzed a total of 65 samples, including 22 patients with CRPC and 43 patients with non-CRPC who had received treatment with LHRH agonists and AA for up to 2 years. Our findings showed a significant H-score difference in CD44 protein expression between CRPC prostate adenocarcinoma samples 869 (200-1329) and non-CRPC 524 (154-1166) (p = 0.033). There was no significant difference in CD133 protein expression between the two groups (p = 0.554). However, there was a significant difference in the nonoccurrence of CRPC between the high expressions of both CD44 and CD133 groups with other expressions of CD44/CD133 groups (25% vs. 75%; p = 0.011; odds ratio = 4.29; 95% confidence interval [1.34, 13.76]).

CONCLUSION

This study found a low expression of at least one CD44/CD133 protein in the patients without early occurrence of CRPC. This result might suggest that CD44/CD133 may function as a potential prognostic marker for PCa, especially in a low expression, to identify patients who have a better prognosis regarding the occurrence of early CRPC.

Biomolecular fingerprints of the effect of zoledronic acid on prostate cancer stem cells: Comparison of 2D and 3D cell culture models

Revealing the potential of candidate drugs against different cancer types without disrupting normal cells depends on the drug mode of action. In the current study, the drug response of prostate cancer stem cells (PCSCs) to zoledronic acid (ZOL) grown in two-dimensional (2D) and three-dimensional (3D) culture systems was compared using Fourier transform-infrared (FT-IR) spectroscopy which is a vibrational spectroscopic technique, supporting by biochemical assays and imaging techniques. Based on our data, in 2D cell culture conditions, the ZOL treatment of PCSCs isolated according to both C133 and CD44 cell surface properties induced early/late apoptosis and suppressed migration ability. The CD133 gene expression and protein levels were altered, depending on culture systems. CD133 expression was significantly reduced in 2D cells upon ZOL treatment. FT-IR data revealed that the integrity, fluidity, and ordering/disordering states of the cell membrane and nucleic acid content were altered in both 2D and 3D cells after ZOL treatment. Regular protein structures decrease in 2D cells while glycogen and protein contents increase in 3D cells, indicating a more pronounced cytotoxic effect of ZOL for 2D cells. Untreated 3D PCSCs exhibited an even different spectral profile associated with IR signals of lipids, proteins, nucleic acids, and glycogen in comparison to untreated 2D cells. Our study revealed significant differences in the drug response and cellular constituents between 2D and 3D cells. Exploring molecular targets and/or drug-action mechanisms is significant in cancer treatment approaches; thus, FT-IR spectroscopy can be successfully applied as a novel drug-screening method in clinical research.

RUNX2 prompts triple negative breast cancer drug resistance through TGF-β pathway regulating breast cancer stem cells

Triple-negative breast cancer (TNBC) stands out as the most aggressive subtype within the spectrum of breast cancer. The current clinical guidelines propose treatment strategies involving cytotoxic agents like epirubicin or paclitaxel. However, the emergence of acquired resistance frequently precipitates secondary tumor recurrence or the spread of metastasis. In recent times, significant attention has been directed toward the transcription factor RUNX2, due to its pivotal role in both tumorigenesis and the progression of cancer. Previous researches suggest that RUNX2 might be intricately linked to the development of resistance against chemotherapy, with its mechanism of action possibly intertwined with the signaling of TGF-β. Nevertheless, the precise interplay between their effects and the exact molecular mechanisms underpinning chemoresistance in TNBC remain elusive. Therefore, we have taken a multifaceted approach from in vitro and in vivo experiments to validate the relationship between RUNX2 and TGF-β and to search for their pathogenic mechanisms in chemoresistance. In conclusion, we found that RUNX2 affects chemoresistance by regulating cancer cell stemness through direct binding to TGF-β, and that TGF-β dually regulates RUNX2 expression. The important finding will provide a new reference for clinical reversal of the development of chemoresistance in breast cancer.

Carborane-Based ABCG2-Inhibitors Sensitize ABC-(Over)Expressing Cancer Cell Lines for Doxorubicin and Cisplatin

The ABCG2 transporter protein, as part of several known mechanisms involved in multidrug resistance, has the ability to transport a broad spectrum of substrates out of the cell and is, therefore, considered as a potential target to improve cancer therapies or as an approach to combat drug resistance in cancer. We have previously reported carborane-functionalized quinazoline derivatives as potent inhibitors of human ABCG2 which effectively reversed breast cancer resistance protein (BCRP)-mediated mitoxantrone resistance. In this work, we present the evaluation of our most promising carboranyl BCRP inhibitors regarding their toxicity towards ABCG2-expressing cancer cell lines (MCF-7, doxorubicin-resistant MCF-7 or MCF-7 Doxo, HT29, and SW480) and, consequently, with the co-administration of an inhibitor and therapeutic agent, their ability to increase the efficacy of therapeutics with the successful inhibition of ABCG2. The results obtained revealed synergistic effects of several inhibitors in combination with doxorubicin or cisplatin. Compounds DMQCa, DMQCc, and DMQCd showed a decrease in IC50 value in ABCB1- and ABCG2-expressing SW480 cells, suggesting a possible targeting of both transporters. In an HT29 cell line, with the highest expression of ABCG2 among the tested cell lines, using co-treatment of doxorubicin and DMQCd, the effective inhibitory concentration of the antineoplastic agent could be reduced by half. Interestingly, co-treatment of compound QCe with cisplatin, which is not an ABCG2 substrate, showed synergistic effects in MCF-7 Doxo and HT29 cells (IC50 values halved or reduced by 20%, respectively). However, a literature-known upregulation of cisplatin-effluxing ABC transporters and their effective inhibition by the carborane derivatives emerges as a possible reason.

A novel CircRNA Circ_0001722 regulates proliferation and invasion of osteosarcoma cells through targeting miR-204-5p/RUNX2 axis

BACKGROUND

Osteosarcoma (OS) is the most prevalent primary fatal bone neoplasm in adolescents and children owing to limited therapeutic methods. Circular RNAs (circRNAs) are identified as vital regulators in a variety of cancers. However, the roles of circRNAs in OS are still unclear.

METHODS

Firstly, we evaluate the differentially expressed circRNAs in 3 paired OS and corresponding adjacent nontumor tissue samples by circRNA microarray assay, finding a novel circRNA, circ_001722, significantly upregulated in OS tissues and cells. The circular structure of candidate circRNA was confirmed through Sanger sequencing, divergent primer PCR, and RNase R treatments. Proliferation of OS cells was evaluated in vitro and in vivo. The microRNA (miRNA) sponge mechanism of circRNAs was verified by dual-luciferase assay and RNA immunoprecipitation assay.

RESULTS

A novel circRNA, circ_001722, is significantly upregulated in OS tissues and cells. Downregulation of circ_0001722 can suppress proliferation and invasion of human OS cells in vitro and in vivo. Computational algorithms predict miR-204-5p can bind with circ_0001722 and RUNX2 mRNA 3'UTR, which is verified by Dual-luciferase assay and RNA immunoprecipitation assay. Further functional experiments show that circ_0001722 competitively binds to miR-204-5p and prevents it to decrease the level of RUNX2, which upregulates proliferation and invasion of human OS cells.

CONCLUSION

Circ_001722 is a novel tumor promotor in OS, and promotes the progression of OS via miR-204-5p/RUNX2 axis.

Tissue-specific cancer stem/progenitor cells: Therapeutic implications

Surgical resection, chemotherapy, and radiation are the standard therapeutic modalities for treating cancer. These approaches are intended to target the more mature and rapidly dividing cancer cells. However, they spare the relatively quiescent and intrinsically resistant cancer stem cells (CSCs) subpopulation residing within the tumor tissue. Thus, a temporary eradication is achieved and the tumor bulk tends to revert supported by CSCs' resistant features. Based on their unique expression profile, the identification, isolation, and selective targeting of CSCs hold great promise for challenging treatment failure and reducing the risk of cancer recurrence. Yet, targeting CSCs is limited mainly by the irrelevance of the utilized cancer models. A new era of targeted and personalized anti-cancer therapies has been developed with cancer patient-derived organoids (PDOs) as a tool for establishing pre-clinical tumor models. Herein, we discuss the updated and presently available tissue-specific CSC markers in five highly occurring solid tumors. Additionally, we highlight the advantage and relevance of the three-dimensional PDOs culture model as a platform for modeling cancer, evaluating the efficacy of CSC-based therapeutics, and predicting drug response in cancer patients.

Glucocorticoid Receptor and β-Catenin Interact in Prostate Cancer Cells and Their Co-Inhibition Attenuates Tumorsphere Formation, Stemness, and Docetaxel Resistance

Therapy resistance hinders the efficacy of anti-androgen therapies and taxane-based chemotherapy for advanced prostate cancer (PCa). Glucocorticoid receptor (GR) signaling mediates resistance to androgen receptor signaling inhibitors (ARSI) and has also been recently implicated in PCa resistance to docetaxel (DTX), suggesting a role in therapy cross-resistance. Like GR, β-catenin is upregulated in metastatic and therapy-resistant tumors and is a crucial regulator of cancer stemness and ARSI resistance. β-catenin interacts with AR to promote PCa progression. Given the structural and functional similarities between AR and GR, we hypothesized that β-catenin also interacts with GR to influence PCa stemness and chemoresistance. As expected, we observed that treatment with the glucocorticoid dexamethasone promotednuclear accumulation of GR and active β-catenin in PCa cells. Co-immunoprecipitation studies showed that GR and β-catenin interact in DTX-resistant and DTX-sensitive PCa cells. Pharmacological co-inhibition of GR and β-catenin, using the GR modulator CORT-108297 and the selective β-catenin inhibitor MSAB, enhanced cytotoxicity in DTX-resistant PCa cells grown in adherent and spheroid cultures and decreased CD44+/CD24- cell populations in tumorspheres. These results indicate that GR and β-catenin influence cell survival, stemness, and tumorsphere formation in DTX-resistant cells. Their co-inhibition could be a promising therapeutic strategy to overcome PCa therapy cross-resistance.

Anti-Cancer Stem-Cell-Targeted Therapies in Prostate Cancer

Prostate cancer (PCa) is the second-most commonly diagnosed cancer in men around the world. It is treated using a risk stratification approach in accordance with the National Comprehensive Cancer Network (NCCN) in the United States. The main treatment options for early PCa include external beam radiation therapy (EBRT), brachytherapy, radical prostatectomy, active surveillance, or a combination approach. In those with advanced disease, androgen deprivation therapy (ADT) is considered as a first-line therapy. However, the majority of cases eventually progress while receiving ADT, leading to castration-resistant prostate cancer (CRPC). The near inevitable progression to CRPC has spurred the recent development of many novel medical treatments using targeted therapies. In this review, we outline the current landscape of stem-cell-targeted therapies for PCa, summarize their mechanisms of action, and discuss avenues of future development.

Alteration of the HIF-1α/VEGF Signaling Pathway and Disruption of the Cell Cycle by Second Generation Carbosilan Dendrimers

Current therapies against prostate cancer (PCa) disease, such as surgery, radiotherapy, or in last term chemical castration by androgen deprivation, have led to significant reduction of the incidence of PCa throughout the world. Worse prognosis is found in those patients which exhibit castration resistance, relapsing into the disease with even greater aggressiveness. Hypoxia cancer cell adaption has been observed to be closely connected to fatal prognostic tumor features. Therefore, hypoxia adaptive mechanisms of cancer cells have attracted large interest as a relevant biological target for treatment-resistant patients. Dendrimers have been established as a promising nanotechnological tool owing to their beneficial physicochemical features such as multivalency and monodispersity. Herein, we have completed a thorough study to better understand the effect within the cell of the already published ruthenium(II)-N-heterocyclic carbene metallodendrimer (G₂Ru) that was able to drastically reduce HIF-1α stabilization and exhibited antiproliferative capability against androgen-sensitive (LNCaP) and androgen-resistant prostate cancer cells (LNFLU) in vitro. G₂Ru, as well as its cationic imidazolium precursor (G₂P), displayed scavenging properties against intracellular and externally stimulated ROS levels, which would presumably hinder the stabilization of HIF-1α by prolyl hydroxylase (PHD) inhibition. Furthermore, these dendrimers have shown considerably beneficial properties against tumor progression capability in terms of apoptosis, cell cycle, CSCs expression, and epithelial phenotype promotion. Taken all together, in this study we could demonstrate the extraordinary anticancer properties of NHC-based carbosilane dendrimers against androgen-resistant prostate cancer cells in vitro.

Prostate Cancer Stem Cells: The Role of CD133

Prostate cancer stem cells (PCSCs), possessing self-renewal properties and resistance to anticancer treatment, are possibly the leading cause of distant metastasis and treatment failure in prostate cancer (PC). CD133 is one of the most well-known and valuable cell surface markers of cancer stem cells (CSCs) in many cancers, including PC. In this article, we focus on reviewing the role of CD133 in PCSC. Any other main stem cell biomarkers in PCSC reported from key publications, as well as about vital research progress of CD133 in CSCs of different cancers, will be selectively reviewed to help us inform the main topic.

Resistance to prostate cancer treatments

A review of the current treatment options for prostate cancer and the formation of resistance to these regimens has been compiled including primary, acquired, and cross-resistance. The diversification of the pathways involved and the escape routes the tumor is utilizing have been addressed. Whereas early stages of tumor can be cured, there is no treatment available after a point of no return has been reached, leaving palliative treatment as the only option. The major reasons for this outcome are the heterogeneity of tumors, both inter- and intra-individually and the nearly endless number of escape routes, which the tumor can select to overcome the effects of treatment. This means that more focus should be applied to the individualization of both diagnosis and therapy of prostate cancer. In addition to current treatment options, novel drugs and ongoing clinical trials have been addressed in this review.

Flavokawain A Reduces Tumor-Initiating Properties and Stemness of Prostate Cancer

We have previously demonstrated the in vivo chemopreventive efficacy of flavokawain A (FKA), a novel chalcone from the kava plant, in prostate carcinogenesis models. However, the mechanisms of the anticarcinogenic effects of FKA remain largely unknown. We evaluated the effect of FKA on prostate tumor spheroid formation by prostate cancer stem cells, which were sorted out from CD44+/CD133+ prostate cancer cells 22Rv1 and DU145. FKA treatment significantly decreased both the size and numbers of the tumor spheroids over different generations of spheroid passages. In addition, the dietary feeding of FKA-formulated food to Nonobese diabetic/severe combined immunodeficiency (NOD/SCID) mice bearing CD44+/CD133+ 22Rv1 xenograft tumors resulted in a significant reduction of tumor growth compared to those fed with vehicle control food–fed mice. Furthermore, the expression of stem cell markers, such as Nanog, Oct4, and CD44, were markedly downregulated in both tumor spheroids and tumor tissues. We also observed that FKA inhibits Ubc12 neddylation, c-Myc, and keratin-8 expression in both CD44+/CD133+ prostate tumor spheroids and xenograft tumors. Our results suggest that FKA can reduce the tumor-initiating properties and stemness of prostate cancer, which provides a new mechanism for the chemoprevention efficacy of FKA.

Role of prostate cancer stem-like cells in the development of antiandrogen resistance

Androgen deprivation therapy (ADT) is the standard of care treatment for advance stage prostate cancer. Treatment with ADT develops resistance in multiple ways leading to the development of castration-resistant prostate cancer (CRPC). Present research establishes that prostate cancer stem-like cells (CSCs) play a central role in the development of treatment resistance followed by disease progression. Prostate CSCs are capable of self-renewal, differentiation, and regenerating tumor heterogeneity. The stemness properties in prostate CSCs arise due to various factors such as androgen receptor mutation and variants, epigenetic and genetic modifications leading to alteration in the tumor microenvironment, changes in ATP-binding cassette (ABC) transporters, and adaptations in molecular signaling pathways. ADT reprograms prostate tumor cellular machinery leading to the expression of various stem cell markers such as Aldehyde Dehydrogenase 1 Family Member A1 (ALDH1A1), Prominin 1 (PROM1/CD133), Indian blood group (CD44), SRY-Box Transcription Factor 2 (Sox2), POU Class 5 Homeobox 1(POU5F1/Oct4), Nanog and ABC transporters. These markers indicate enhanced self-renewal and stemness stimulating CRPC evolution, metastatic colonization, and resistance to antiandrogens. In this review, we discuss the role of ADT in prostate CSCs differentiation and acquisition of CRPC, their isolation, identification and characterization, as well as the factors and pathways contributing to CSCs expansion and therapeutic opportunities.

Cancer Stem Cell Markers for Urinary Carcinoma

Cancer stem cell (CSC) refers to cancer cells with stem cell properties, that is, they have the ability of “self-renewal” and “differentiation.” Cancer stem cells exist in cancer cells and are the “culprit” of cancer recurrence and metastasis. It is difficult to be found because of its small amount, and it is difficult for anticancer drugs to produce effects on it. At present, the isolation and identification of cancer stem cells from many solid tumors are still quite difficult, mainly due to the lack of specific molecular markers of cancer stem cells. In this review, cancer stem cell surface markers and functional markers in urinary system were summarized. These markers can provide molecular targets for cancer therapy.

HN1L promotes stem cell-like properties by regulating TGF-β signaling pathway through targeting FOXP2 in prostate cancer

Dysregulated hematological and neurological expressed 1-like (HN1L) has been implicated in carcinogenesis of difference cancers, including hepatocellular carcinoma and breast cancer. However, the role of HN1L in the progression of prostate cancer (PCA) remains unknown. Therefore, we aimed to investigate the role of HN1L in stemness and progression of PCA. The expression of HN1L in PCA tissues and cells was determined by quantitative reverse-transcription polymerase chain reaction (qRT-PCR), western blot analysis, and/or immunohistochemistry (IHC). CD133+ cells were sorted from PCA cells using magnetic fluorescence cell sorting technology and were considered as cancer stem cells (CSCs). Sphere formation assays, transwell assays, and animal experiments were conducted to assess cell stemness, migration, invasion, and in vivo tumorigenesis, respectively. The results showed that HN1L expression was higher in PCA tissues and cells as compared with normal tissues and cells, as well as in CD133+ cells as compared with CD133- cells. HN1L knockdown significantly decreased the expression levels of CSC markers including OCT4 (POU class 5 homeobox 1), CD44, and SRY-box transcription factor 2, inhibited cell migration, invasion, and tumorigenesis and decreased the number of tumor spheroids and CD133+ cell population. Furthermore, we found that HN1L could bind to forkhead box P2 (FOXP2) and positively regulated transforming growth factor-β (TGF-β) expression via upregulation of FOXP2. In addition, the overexpression of TGF-β in HN1L-knockdown PCA cells increased the number of tumor spheroids and CD133+ cell population, as well as enhanced cell migration and invasion. Collectively, this study demonstrates that HN1L promotes stem cell-like properties and cancer progression by targeting FOXP2 through TGF-β signaling pathway in PCA.

The Mangrove-Derived Diterpenoid Diaporthe B Inhibits the Stemness and Increases the Efficacy of Docetaxel in Prostate Cancer PC-3 Cells

The absolute configuration of diaporthe B, a pimarane diterpene isolated from the mangrove derived endophytic fungus Eutypella sp #3E, was determined by a single-crystal x-ray diffraction study. The present study aimed to investigate the effects of diaporthe B on docetaxel-resistant prostate cancer PC-3 cells. Results of our studies showed that docetaxel-resistant PC-3 cells had higher sphere-forming efficiency and an increase in adherence to collagen-coated culture plates. The protein levels of cancer stem cell (CSC)-related markers CD44, CD133, and ALDH1A1 were higher in the docetaxel-resistant PC-3 cells than in the parental cells. Treatment with diaporthe B dose-dependently inhibited the growth and induced apoptosis in the resistant cells. Moreover, diaporthe B treatment decreased the sphere-forming efficiency and the adherence to collagen-coated plates in docetaxel-resistant PC-3 cells. Diaporthe B also decreased the protein levels of CSC-related markers CD44, CD133, and ALDH1A1 in the resistant cells. In addition, a combination of diaporthe B and docetaxel had a more potent effect on growth inhibition and apoptosis in the resistant cells than either agent alone. Our studies suggest that diaporthe B inhibits the stemness of prostate cancer cells and may have therapeutic potential for enhancing the efficacy of docetaxel in docetaxel-resistant prostate cancer cells.

Repurposing of Anticancer Stem Cell Drugs in Brain Tumors

Brain tumors in adults may be infrequent when compared with other cancer etiologies, but they remain one of the deadliest with bleak survival rates. Current treatment modalities encompass surgical resection, chemotherapy, and radiotherapy. However, increasing resistance rates are being witnessed, and this has been attributed, in part, to cancer stem cells (CSCs). CSCs are a subpopulation of cancer cells that reside within the tumor bulk and have the capacity for self-renewal and can differentiate and proliferate into multiple cell lineages. Studying those CSCs enables an increasing understanding of carcinogenesis, and targeting CSCs may overcome existing treatment resistance. One approach to weaponize new drugs is to target these CSCs through drug repurposing which entails using drugs, which are Food and Drug Administration-approved and safe for one defined disease, for a new indication. This approach serves to save both time and money that would otherwise be spent in designing a totally new therapy. In this review, we will illustrate drug repurposing strategies that have been used in brain tumors and then further elaborate on how these approaches, specifically those that target the resident CSCs, can help take the field of drug repurposing to a new level.

Reduced DAPK1 Expression Promotes Stem Cell-Like Characteristics of Prostate Cancer Cells by Activating ZEB1 via Hippo/YAP Signaling Pathway

Prostate cancer (PCa) is a malignant tumor that originates in the male genitourinary system. Downregulation of death-associated protein kinase 1 (DAPK1) is closely related to PCa. Little is known about the functional role of DAPK1 in regulating cancer stem cell (CSC)-like characteristics of PCa cells, and we have conducted research on this topic. Compared with tumor-adjacent normal tissues, DAPK1 was severely downregulated in tumor tissues of PCa patients. DAPK1 expression was also reduced in PCa cell lines with respect to that in normal prostate cells. Moreover, we sorted PCa-CSCs (PCa-CD133⁺ cells) from PCa cells. PCa-CD133⁺ cells also exhibited a reduced DAPK1 level and elevated levels of stem cell markers (CD44, OCT4, and SOX2). DAPK1 knockdown promoted sphere formation and enhanced the proportions of PCa-CD133⁺/PCa-CD133^- cells. Inhibition of DAPK1 also accelerated migration and invasion of PCa-CD133⁺ cells. In addition, DAPK1 interacted with zinc finger E-box-binding homeobox-1 (ZEB1) and repressed ZEB1 expression in PCa-CD133⁺ cells. DAPK1 suppressed Hippo/YAP signaling pathway by interacting with ZEB1. Finally, we generated a tumor xenograft model to verify the effect of PCa-CD133⁺ cells following DAPK1 overexpression on tumor growth of PCa. DAPK1 overexpression inhibited tumor growth of PCa and repressed the expression of ZEB1, YAP, and TAZ in the tumor tissues of PCa mice. In conclusion, reduced DAPK1 expression promoted stem cell-like characteristics of PCa cells through activating ZEB1 via Hippo/YAP signaling pathway. Taken together, this work sheds lights on the potential of DAPK1 as a target for PCa therapeutics from bench to clinic.

Androgen Receptor, Although Not a Specific Marker For, Is a Novel Target to Suppress Glioma Stem Cells as a Therapeutic Strategy for Glioblastoma

Targeting androgen receptor (AR) has been shown to be promising in treating glioblastoma (GBM) in cell culture and flank implant models but the mechanisms remain unclear. AR antagonists including enzalutamide are available for treating prostate cancer patients in clinic and can pass the blood-brain barrier, thus are potentially good candidates for GBM treatment but have not been tested in GBM orthotopically. Our current studies confirmed that in patients, a majority of GBM tumors overexpress AR in both genders. Enzalutamide inhibited the proliferation of GBM cells both in vitro and in vivo. Although confocal microscopy demonstrated that AR is expressed but not specifically in glioma cancer stem cells (CSCs) (CD133+), enzalutamide treatment significantly decreased CSC population in cultured monolayer cells and spheroids, suppressed tumor sphere-forming capacity of GBM cells, and downregulated CSC gene expression at mRNA and protein levels in a dose- and time-dependent manner. We have, for the first time, demonstrated that enzalutamide treatment decreased the density of CSCs in vivo and improved survival in an orthotopic GBM mouse model. We conclude that AR antagonists potently target glioma CSCs in addition to suppressing the overall proliferation of GBM cells as a mechanism supporting their repurposing for clinical applications treating GBM.

Anlotinib exerts anti-cancer efficiency on lung cancer stem cells in vitro and in vivo through reducing NF-κB activity

Anlotinib is a multi-target tyrosine kinase inhibitor. Previous studies confirmed that anlotinib exerts anti-cancer efficiency. However, the functional roles of anlotinib on cancer stem cells (CSCs) are yet to be elucidated. In this study, lung CSCs were isolated and identified in vitro, and mouse xenografts were established in vivo. MTT assays, tumour sphere formation assays, TdT-mediated dUTP nick-end labelling (TUNEL) staining, Annexin V-FITC/PI staining, immunofluorescence analysis and Western blot were performed to investigate the anti-cancer effects of anlotinib on lung CSCs. The results showed that anlotinib inhibits the growth of lung CSCs in vitro and in vivo. In addition, anlotinib induced apoptosis of these cells along with down-regulated expression level of Bcl-2 whereas up-regulated Bax and cleaved caspase-3 expression. It also sensitized lung CSCs to the cytotoxicity of cisplatin and paclitaxel; the tumour sphere formation and expression levels of multiple stemness-associated markers, such as ALDH1 and CD133, were also decreased. Furthermore, the underlying mechanism indicated that anlotinib reduces the phosphorylated levels of NF-κB p65 and IκB-α in lung CSCs. Taken together, these findings suggested that anlotinib exerts potent anti-cancer effects against lung CSCs through apoptotic induction and stemness phenotypic attenuation. The mechanism could be associated with the suppression of NF-κB activity.

The key roles of cancer stem cell-derived extracellular vesicles

Cancer stem cells (CSCs), the subpopulation of cancer cells, have the capability of proliferation, self-renewal, and differentiation. The presence of CSCs is a key factor leading to tumor progression and metastasis. Extracellular vesicles (EVs) are nano-sized particles released by different kinds of cells and have the capacity to deliver certain cargoes, such as nucleic acids, proteins, and lipids, which have been recognized as a vital mediator in cell-to-cell communication. Recently, more and more studies have reported that EVs shed by CSCs make a significant contribution to tumor progression. CSCs-derived EVs are involved in tumor resistance, metastasis, angiogenesis, as well as the maintenance of stemness phenotype and tumor immunosuppression microenvironment. Here, we summarized the molecular mechanism by which CSCs-derived EVs in tumor progression. We believed that the fully understanding of the roles of CSCs-derived EVs in tumor development will definitely provide new ideas for CSCs-based therapeutic strategies.

Inhibition of Bone Morphogenetic Protein 2 Suppresses the Stemness Maintenance of Cancer Stem Cells in Hepatocellular Carcinoma via the MAPK/ERK Pathway

Background

Hepatocellular carcinoma (HCC) remains a life-threatening malignant tumor. Cancer stem cells (CSCs) harbor tumor-initiating capacity and can be used as a therapeutic target for human malignancies. Bone morphogenetic proteins (BMPs) play a regulatory role in CSCs. This study investigated the role and mechanism of BMP2 in CSCs in HCC.

Methods

BMP2 expression in HCC tissues and cells, and CSCs from HepG2 cells and SMMC7721 cells (HepG2-CSCs and SMMC7721-CSCs) was measured. The association between BMP2 expression and prognosis of HCC patients was analyzed. CSCs were interfered with BMP2 to evaluate the abilities of colony and tumor sphere formation, levels of stemness-related markers, epithelial-mesenchymal transition (EMT), and invasion and migration. Levels of MAPK/ERK pathway-related proteins in HepG2-CSCs were detected after BMP2 knockdown. The effect of the activated MAPK/ERK pathway on HepG2-CSCs was assessed. Finally, the effect of BMP2 inhibition on CSCs in HCC was verified in vivo.

Results

BMP2 showed obvious upregulation in HCC tissues and cells and was further upregulated in CSCs in HCC, with its higher expression indicative of worse prognosis. Silencing BMP2 inhibited colony and tumor sphere formation, levels of stemness-related markers, as well as EMT, invasion and migration of HepG2-CSCs and SMMC7721-CSCs. The MAPK/ERK pathway was suppressed after BMP2 knockdown, and its activation reversed the inhibitory effect of shBMP2 on hepatic CSCs. BMP2 accelerated tumor growth and EMT of CSCs in HCC in vivo.

Conclusion

We concluded that BMP2 knockdown inhibited the EMT, proliferation and invasion of CSCs in HCC, thereby hindering the stemness maintenance via suppressing the MAPK/ERK pathway.

Androgen Deprivation Induces Transcriptional Reprogramming in Prostate Cancer Cells to Develop Stem Cell-Like Characteristics

Enzalutamide, an antiandrogen, is approved for therapy of castration resistant prostate cancer. Clinical applications have shown that approximately 30% of patients acquire resistance after a short period of treatment. However, the molecular mechanisms underlying this resistance is not completely understood. To identify transcriptomic signatures associated with acquisition of drug resistance we profiled gene expression of paired enzalutamide sensitive and resistant human prostate cancer LNCaP (lymph node carcinoma of the prostate) and C4-2B cells. Overlapping genes differentially regulated in the enzalutamide resistant cells were ranked by Ingenuity Pathway Analysis and their functional validation was performed using ingenuity knowledge database followed by confirmation to correlate transcript with protein expression. Analysis revealed that genes associated with cancer stem cells, such as POU5F1 (OCT4), SOX2, NANOG, BMI1, BMP2, CD44, SOX9, and ALDH1 were markedly upregulated in enzalutamide resistant cells. Amongst the pathways enriched in the enzalutamide-resistant cells were those associated with RUNX2, hedgehog, integrin signaling, and molecules associated with elastic fibers. Further examination of a patient cohort undergoing ADT and its comparison with no-ADT group demonstrated high expression of POU5F1 (OCT4), ALDH1, and SOX2 in ADT specimens, suggesting that they may be clinically relevant therapeutic targets. Altogether, our approach exhibits the potential of integrative transcriptomic analyses to identify critical genes and pathways of antiandrogen resistance as a promising approach for designing novel therapeutic strategies to circumvent drug resistance.

Transcriptome Remodeling in Gradual Development of Inverse Resistance between Paclitaxel and Cisplatin in Ovarian Cancer Cells

Resistance to anti-cancer drugs is the main challenge in oncology. In pre-clinical studies, established cancer cell lines are primary tools in deciphering molecular mechanisms of this phenomenon. In this study, we proposed a new, transcriptome-focused approach, utilizing a model of isogenic cancer cell lines with gradually changing resistance. We analyzed trends in gene expression in the aim to find out a scaffold of resistance development process. The ovarian cancer cell line A2780 was treated with stepwise increased concentrations of paclitaxel (PTX) to generate a series of drug resistant sublines. To monitor transcriptome changes we submitted them to mRNA-sequencing, followed by the identification of differentially expressed genes (DEGs), principal component analysis (PCA), and hierarchical clustering. Functional interactions of proteins, encoded by DEGs, were analyzed by building protein-protein interaction (PPI) networks. We obtained human ovarian cancer cell lines with gradually developed resistance to PTX and collateral sensitivity to cisplatin (CDDP) (inverse resistance). In their transcriptomes, we identified two groups of DEGs: (1) With fluctuations in expression in the course of resistance acquiring; and (2) with a consistently changed expression at each stage of resistance development, constituting a scaffold of the process. In the scaffold PPI network, the cell cycle regulator-polo-like kinase 2 (PLK2); proteins belonging to the tumor necrosis factor (TNF) ligand and receptor family, as well as to the ephrin receptor family were found, and moreover, proteins linked to osteo- and chondrogenesis and the nervous system development. Our cellular model of drug resistance allowed for keeping track of trends in gene expression and studying this phenomenon as a process of evolution, reflected by global transcriptome remodeling. This approach enabled us to explore novel candidate genes and surmise that abrogation of the osteomimic phenotype in ovarian cancer cells might occur during the development of inverse resistance between PTX and CDDP.

Targeted Delivery of Therapeutics to Urological Cancer Stem Cells

Urological cancer refers to cancer in organs of the urinary system and the male reproductive system. It mainly includes prostate cancer, bladder cancer, renal cancer, etc., seriously threatening patients' survival. Although there are many advances in the treatment of urological cancer, approved targeted therapies often result in tumor recurrence and therapy failure. An increasing amount of evidence indicated that cancer stem cells (CSCs) with tumor-initiating ability were the source of treatment failure in urological cancer. The development of CSCstargeted strategy can provide a possibility for the complete elimination of urological cancer. This review is based on a search of PubMed, Google scholar and NIH database (http://ClinicalTrials.gov/) for English language articles containing the terms: "biomarkers", "cancer stem cells", "targeting/targeted therapy", "prostate cancer", bladder cancer" and "kidney cancer". We summarized the biomarkers and stem cell features of the prostate, bladder and renal CSCs, outlined the targeted strategies for urological CSCs from signaling pathways, cytokines, angiogenesis, surface markers, elimination therapy, differentiation therapy, immunotherapy, microRNA, nanomedicine, etc., and highlighted the prospects and future challenges in this research field.

Molecular tracing of prostate cancer lethality

Prostate cancer is diagnosed mostly in men over the age of 50 years, and has favorable 5-year survival rates due to early cancer detection and availability of curative surgical management. However, progression to metastasis and emergence of therapeutic resistance are responsible for the majority of prostate cancer mortalities. Recent advancement in sequencing technologies and computational capabilities have improved the ability to organize and analyze large data, thus enabling the identification of novel biomarkers for survival, metastatic progression and patient prognosis. Large-scale sequencing studies have also uncovered genetic and epigenetic signatures associated with prostate cancer molecular subtypes, supporting the development of personalized targeted-therapies. However, the current state of mainstream prostate cancer management does not take full advantage of the personalized diagnostic and treatment modalities available. This review focuses on interrogating biomarkers of prostate cancer progression, including gene signatures that correspond to the acquisition of tumor lethality and those of predictive and prognostic value in progression to advanced disease, and suggest how we can use our knowledge of biomarkers and molecular subtypes to improve patient treatment and survival outcomes.

Molecular mechanisms of docetaxel resistance in prostate cancer

Docetaxel (DTX) chemotherapy offers excellent initial response and confers significant survival benefit in patients with castration-resistant prostate cancer (CRPC). However, the clinical utility of DTX is compromised when primary and acquired resistance are encountered. Therefore, a more thorough understanding of DTX resistance mechanisms may potentially improve survival in patients with CRPC. This review focuses on DTX and discusses its mechanisms of resistance. We outline the involvement of tubulin alterations, androgen receptor (AR) signaling/AR variants, ERG rearrangements, drug efflux/influx, cancer stem cells, centrosome clustering, and phosphoinositide 3-kinase/AKT signaling in mediating DTX resistance. Furthermore, potential biomarkers for DTX treatment and therapeutic strategies to circumvent DTX resistance are reviewed.

Androgen Deprivation Induces Reprogramming of Prostate Cancer Cells to Stem-Like Cells

In the past few years, cell plasticity has emerged as a mode of targeted therapy evasion in prostate adenocarcinoma. When exposed to anticancer therapies, tumor cells may switch into a different histological subtype, such as the neuroendocrine phenotype which is associated with treatment failure and a poor prognosis. In this study, we demonstrated that long-term androgen signal depletion of prostate LNCaP cells induced a neuroendocrine phenotype followed by re-differentiation towards a “stem-like” state. LNCaP cells incubated for 30 days in charcoal-stripped medium or with the androgen receptor antagonist 2-hydroxyflutamide developed neuroendocrine morphology and increased the expression of the neuroendocrine markers βIII-tubulin and neuron specific enolase (NSE). When cells were incubated for 90 days in androgen-depleted medium, they grew as floating spheres and had enhanced expression of the stem cell markers CD133, ALDH1A1, and the transporter ABCB1A. Additionally, the pluripotent transcription factors Nanog and Oct4 and the angiogenic factor VEGF were up-regulated while the expression of E-cadherin was inhibited. Cell viability revealed that those cells were resistant to docetaxel and 2-hidroxyflutamide. Mechanistically, androgen depletion induced the decrease in AMP-activated kinase (AMPK) expression and activation and stabilization of the hypoxia-inducible factor HIF-1α. Overexpression of AMPK in the stem-like cells decreased the expression of stem markers as well as that of HIF-1α and VEGF while it restored the levels of E-cadherin and PGC-1α. Most importantly, docetaxel sensitivity was restored in stem-like AMPK-transfected cells. Our model provides a new regulatory mechanism of prostate cancer plasticity through AMPK that is worth exploring.

XRCC1 Is a Promising Predictive Biomarker and Facilitates Chemo-Resistance in Gallbladder Cancer

Gallbladder cancer is a relatively uncommon human malignant tumor with an extremely poor prognosis. Currently, no biomarkers can accurately diagnose gallbladder cancer and predict patients' prognosis. XRCC1 is involved in tumorigenesis, progression, and chemo-resistance of several human cancers, but the role of XRCC1 in gallbladder cancer is never reported. In this study, we investigated the expression of XRCC1 and its clinicopathological and prognostic significance in gallbladder cancer, and explored the biological role of XRCC1 in gallbladder cancer cells. We found that XRCC1 was significantly up-regulated in gallbladder cancer in protein and mRNA levels. Positive XRCC1 expression was correlated with aggressive clinicopathological features and was an independent poor prognostic factor in gallbladder cancer. The ROC curves suggested that XRCC1 expression had potential clinicopathological diagnostic value in gallbladder cancer. In vitro, XRCC1 was overexpression in CD133⁺GBC-SD cells compared to GBC-SD cells. In functional experiment, XRCC1 knockdown had a non-significant impact on proliferation, migration, invasion, and apoptosis of CD133⁺GBC-SD cells. But, XRCC1 knockdown could significantly improve the sensitivity of CD133⁺GBC-SD cells to 5-Fluorouracil via promoting cell necrosis and apoptosis. Thus, this study indicates that XRCC1 may be a promising predictive biomarker of gallbladder cancer and a potential therapeutic target for gallbladder cancer.

NANOG helps cancer cells escape NK cell attack by downregulating ICAM1 during tumorigenesis

Background

At the beginning of tumorigenesis, newly born cancer cells must successfully avoid attack by the immune system. Although most abnormal cells are efficiently identified and destroyed by the immune system, particularly by NK cells, the molecular mechanisms by which newly born cancer cells evade NK cell surveillance are not fully understood.

Methods

NK cell resistance of highly tumorigenic population of human prostate cancer (PCa) cells were confirmed by xenograft in SCID mice with or without NK cell neutralization. The mechanisms by which the tumorigenic PCa cells evaded NK cell attack were investigated by RNAseq, ChIPseq, generation of several transformants and xenograft in SCID mice.

Results

Here, we show that PCa cells have a strengthened ability to escape NK cell attack due to NANOG, a pluripotent-related transcription factor, mediating the repression of ICAM1, a cell adhesion molecule, during tumorigenesis. Mechanistically, NANOG directly binds to the region upstream of ICAM1. As the binding between NANOG and the upstream ICAM1 region increases, p300 binding to this region is diminished, resulting in decreased ICAM1 expression. High NANOG expression confers PCa cells the ability to resist NK cell attack via the repression of ICAM1. Consistent with these results, low ICAM1 expression is significantly correlated with a high recurrence rate in patients with PCa.

Conclusions

Our findings indicate that repression of ICAM1 is a critical mechanism by which cancer cells evade attack from NK cells during tumorigenesis. These results suggest a pivotal role of NANOG in establishing a gene expression profile for escaping the immune system.

Cellular and Molecular Mechanisms Underlying Prostate Cancer Development: Therapeutic Implications

Prostate cancer is the most frequent nonskin cancer and second most common cause of cancer-related deaths in man. Prostate cancer is a clinically heterogeneous disease with many patients exhibiting an aggressive disease with progression, metastasis, and other patients showing an indolent disease with low tendency to progression. Three stages of development of human prostate tumors have been identified: intraepithelial neoplasia, adenocarcinoma androgen-dependent, and adenocarcinoma androgen-independent or castration-resistant. Advances in molecular technologies have provided a very rapid progress in our understanding of the genomic events responsible for the initial development and progression of prostate cancer. These studies have shown that prostate cancer genome displays a relatively low mutation rate compared with other cancers and few chromosomal loss or gains. The ensemble of these molecular studies has led to suggest the existence of two main molecular groups of prostate cancers: one characterized by the presence of ERG rearrangements (~50% of prostate cancers harbor recurrent gene fusions involving ETS transcription factors, fusing the 5' untranslated region of the androgen-regulated gene TMPRSS2 to nearly the coding sequence of the ETS family transcription factor ERG) and features of chemoplexy (complex gene rearrangements developing from a coordinated and simultaneous molecular event), and a second one characterized by the absence of ERG rearrangements and by the frequent mutations in the E3 ubiquitin ligase adapter SPOP and/or deletion of CDH1, a chromatin remodeling factor, and interchromosomal rearrangements and SPOP mutations are early events during prostate cancer development. During disease progression, genomic and epigenomic abnormalities accrued and converged on prostate cancer pathways, leading to a highly heterogeneous transcriptomic landscape, characterized by a hyperactive androgen receptor signaling axis.

Transcriptional Reprogramming and Novel Therapeutic Approaches for Targeting Prostate Cancer Stem Cells

Prostate cancer is the most common malignancy in men and the second cause of cancer-related deaths in western countries. Despite the progress in the treatment of localized prostate cancer, there is still lack of effective therapies for the advanced forms of the disease. Most patients with advanced prostate cancer become resistant to androgen deprivation therapy (ADT), which remains the main therapeutic option in this setting, and progress to lethal metastatic castration-resistant prostate cancer (mCRPC). Current therapies for prostate cancer preferentially target proliferating, partially differentiated, and AR-dependent cancer cells that constitute the bulk of the tumor mass. However, the subpopulation of tumor-initiating or tumor-propagating stem-like cancer cells is virtually resistant to the standard treatments causing tumor relapse at the primary or metastatic sites. Understanding the pathways controlling the establishment, expansion and maintenance of the cancer stem cell (CSC) subpopulation is an important step toward the development of more effective treatment for prostate cancer, which might enable ablation or exhaustion of CSCs and prevent treatment resistance and disease recurrence. In this review, we focus on the impact of transcriptional regulators on phenotypic reprogramming of prostate CSCs and provide examples supporting the possibility of inhibiting maintenance and expansion of the CSC pool in human prostate cancer along with the currently available methodological approaches. Transcription factors are key elements for instructing specific transcriptional programs and inducing CSC-associated phenotypic changes implicated in disease progression and treatment resistance. Recent studies have shown that interfering with these processes causes exhaustion of CSCs with loss of self-renewal and tumorigenic capability in prostate cancer models. Targeting key transcriptional regulators in prostate CSCs is a valid therapeutic strategy waiting to be tested in clinical trials.

The Contributions of Prostate Cancer Stem Cells in Prostate Cancer Initiation and Metastasis

Research in the last decade has clearly revealed a critical role of prostate cancer stem cells (PCSCs) in prostate cancer (PC). Prostate stem cells (PSCs) reside in both basal and luminal layers, and are the target cells of oncogenic transformation, suggesting a role of PCSCs in PC initiation. Mutations in PTEN, TP53, and RB1 commonly occur in PC, particularly in metastasis and castration-resistant PC. The loss of PTEN together with Ras activation induces partial epithelial–mesenchymal transition (EMT), which is a major mechanism that confers plasticity to cancer stem cells (CSCs) and PCSCs, which contributes to metastasis. While PTEN inactivation leads to PC, it is not sufficient for metastasis, the loss of PTEN concurrently with the inactivation of both TP53 and RB1 empower lineage plasticity in PC cells, which substantially promotes PC metastasis and the conversion to PC adenocarcinoma to neuroendocrine PC (NEPC), demonstrating the essential function of TP53 and RB1 in the suppression of PCSCs. TP53 and RB1 suppress lineage plasticity through the inhibition of SOX2 expression. In this review, we will discuss the current evidence supporting a major role of PCSCs in PC initiation and metastasis, as well as the underlying mechanisms regulating PCSCs. These discussions will be developed along with the cancer stem cell (CSC) knowledge in other cancer types.

Role of OCT4 in cancer stem-like cells and chemotherapy resistance

Cancer stem-like cells (CSCs) contribute to the tumorigenicity, progression, and chemoresistance of cancers. It is not known whether CSCs arise from normal stem cells or if they arise from differentiated cancer cells by acquiring self-renewal features. These CSCs share stem cell markers that normal stem cells express. There is a rising interest in octamer-binding transcription factor 4 (OCT4), one of the stem cell factors that are essential in embryogenesis and pluripotency. OCT4 is also overexpressed in CSCs of various cancers. Although the majority of the studies in CSCs reported a positive association between the expression of OCT4 and chemoresistance and an inverse correlation between OCT4 and clinical prognosis, there are studies rebuking these findings, possibly due to the sparsity of stem cells within tumors and the heterogeneity of tumors. In addition, post-translational modification of OCT4 affects its activity and warrants further investigation for its association with chemoresistance and prognosis.

Cancer stem cell impact on clinical oncology

Cancer is a widespread worldwide chronic disease. In most cases, the high mortality rate from cancer correlates with a lack of clear symptoms, which results in late diagnosis for patients, and consequently, advanced tumor disease with poor probabilities for cure, since many patients will show chemo- and radio-resistance. Several mechanisms have been studied to explain chemo- and radio-resistance to anti-tumor therapies, including cell signaling pathways, anti-apoptotic mechanisms, stemness, metabolism, and cellular phenotypes. Interestingly, the presence of cancer stem cells (CSCs), which are a subset of cells within the tumors, has been related to therapy resistance. In this review, we focus on evaluating the presence of CSCs in different tumors such as breast cancer, gastric cancer, lung cancer, and hematological neoplasias, highlighting studies where CSCs were identified in patient samples. It is evident that there has been a great drive to identify the cell surface phenotypes of CSCs so that they can be used as a tool for anti-tumor therapy treatment design. We also review the potential effect of nanoparticles, drugs, natural compounds, aldehyde dehydrogenase inhibitors, cell signaling inhibitors, and antibodies to treat CSCs from specific tumors. Taken together, we present an overview of the role of CSCs in tumorigenesis and how research is advancing to target these highly tumorigenic cells to improve oncology patient outcomes.

Cytoglobin ameliorates the stemness of hepatocellular carcinoma via coupling oxidative-nitrosative stress signals

Cancer stem cells (CSCs) account for tumor self-renewal and heterogeneity. Oxidative-nitrosative stress (ONS) is an independent etiologic factor throughout tumorigenesis. Emerging evidences indicated that the interaction of ONS with CSCs contributes to tumor progression and resistance to chemoradiotherapy. Cytoglobin (Cygb) is a member of human hexacoordinate hemoglobin family and acts as a dynamic mediator of redox homeostasis. We observed that Cygb is significantly deregulated in human hepatocellular carcinoma (HCC) tissue and its decrease aggravates the growth of liver cancer stem cells (LCSCs) and increases the subpopulation of CD133(+) LCSCs. Cygb restoration inhibits HCC proliferation and LCSC growth, and decreases the subpopulation of CD133 (+) LCSCs in vitro. We found that Cygb absence promotes LCSC phenotypes and PI3 K/AKT activation, whereas Cygb restoration inhibits LCSC phenotypes and PI3 K/AKT activation. Furthermore, exogenous antioxidants can eliminate the inhibitory effect of Cygb to LCSC growth and phenotypes, as well as PI3 K/AKT activation. Collectively, this study demonstrated that cytoglobin functions as a tumor suppressor and targets CSCs at an ONS-dependent manner. Thus, Cygb restoration could be a novel and promising therapeutic strategy against HCC with aberrant ROS/RNS accumulation.

Somatic Pluripotent Genes in Tissue Repair, Developmental Disease, and Cancer

Embryonic stem cells possess the ability to differentiate into all cell types of the body. This pliable developmental state is achieved by the function of a series of pluripotency factors, classically identified as OCT4, SOX2, and NANOG. These pluripotency factors are responsible for activating the larger pluripotency networks and the self-renewal programs which give ES cells their unique characteristics. However, during differentiation pluripotency networks become downregulated as cells achieve greater lineage specification and exit the cell cycle. Typically the repression of pluripotency is viewed as a positive factor to ensure the fidelity of cellular identity by restricting cellular pliancy. Consistent with this view, the expression of pluripotency factors is greatly restricted in somatic cells. However, there are examples whereby cells either maintain or reactivate pluripotency factors to preserve the increased potential for the healing of wounds or tissue homeostasis. Additionally there are many examples where these pluripotency factors become reactivated in a variety of human pathologies, particularly cancer. In this review, we will summarize the somatic repression of pluripotency factors, their role in tissue homeostasis and wound repair, and the human diseases that are associated with pluripotency factor misregulation with an emphasis on their role in the etiology of multiple cancers.