Drug Resistance Driven by Cancer Stem Cells and Their Niche

CEACAM7 Is an Effective Target for CAR T-cell Therapy of Pancreatic Ductal Adenocarcinoma

PURPOSE

To investigate whether CEACAM7 represents a novel therapeutic target for treating pancreatic ductal adenocarcinoma (PDAC) and to generate CEACAM7-targeting CAR T cells to test this hypothesis.

EXPERIMENTAL DESIGN

We identified CEACAM7 (CGM2), a member of the CEA family of proteins with expression restricted to the colon and pancreas, as a potential CAR T-cell target for PDAC. We probed a panel of PDAC tumor sections as well as patient-derived PDAC cell cultures for CEACAM7 expression. We generated CAR-targeting CEACAM7, and assessed antitumor efficacy of CEACAM7 CAR T cells using in vitro and in vivo models.

RESULTS

We show here that CEACAM7 is expressed in a large subset of PDAC tumors, with low to undetectable expression in all normal tissues tested. CEACAM7 is also expressed in primary PDAC cultures isolated from patient-derived tumors, with high expression within the cancer stem cell-enriched subset. CAR T cells targeting CEACAM7 are capable of targeting antigen-expressing tumor cells, and mediate remission in patient-derived xenograft tumors.

CONCLUSIONS

We identify CEACAM7 as a potential therapeutic target in PDAC and describe the development of CEACAM7-targeted CAR T cells with efficacy against PDAC.

Molecular Subtypes Based on the Stemness Index Predict Prognosis in Glioma Patients

Glioma is the common histological subtype of malignancy in the central nervous system, with high morbidity and mortality. Glioma cancer stem cells (CSCs) play essential roles in tumor recurrence and treatment resistance. Thus, exploring the stem cell-related genes and subtypes in glioma is important. In this study, we collected the RNA-sequencing (RNA-seq) data and clinical information of glioma patients from The Cancer Genome Atlas (TCGA) and Chinese Glioma Genome Atlas (CGGA) databases. With the differentially expressed genes (DEGs) and weighted gene correlation network analysis (WGCNA), we identified 86 mRNA expression-based stemness index (mRNAsi)-related genes in 583 samples from TCGA RNA-seq dataset. Furthermore, these samples from TCGA database could be divided into two significantly different subtypes with different prognoses based on the mRNAsi corresponding gene, which could also be validated in the CGGA database. The clinical characteristics and immune cell infiltrate distribution of the two stemness subtypes are different. Then, functional enrichment analyses were performed to identify the different gene ontology (GO) terms and pathways in the two different subtypes. Moreover, we constructed a stemness subtype-related risk score model and nomogram to predict the prognosis of glioma patients. Finally, we selected one gene (ETV2) from the risk score model for experimental validation. The results showed that ETV2 can contribute to the invasion, migration, and epithelial-mesenchymal transition (EMT) process of glioma. In conclusion, we identified two distinct molecular subtypes and potential therapeutic targets of glioma, which could provide new insights for the development of precision diagnosis and prognostic prediction for glioma patients.

Current methods in translational cancer research

Recent developments in pre-clinical screening tools, that more reliably predict the clinical effects and adverse events of candidate therapeutic agents, has ushered in a new era of drug development and screening. However, given the rapid pace with which these models have emerged, the individual merits of these translational research tools warrant careful evaluation in order to furnish clinical researchers with appropriate information to conduct pre-clinical screening in an accelerated and rational manner. This review assesses the predictive utility of both well-established and emerging pre-clinical methods in terms of their suitability as a screening platform for treatment response, ability to represent pharmacodynamic and pharmacokinetic drug properties, and lastly debates the translational limitations and benefits of these models. To this end, we will describe the current literature on cell culture, organoids, in vivo mouse models, and in silico computational approaches. Particular focus will be devoted to discussing gaps and unmet needs in the literature as well as current advancements and innovations achieved in the field, such as co-clinical trials and future avenues for refinement.

High dose acetaminophen inhibits STAT3 and has free radical independent anti-cancer stem cell activity

High-dose acetaminophen (AAP) with delayed rescue using n-acetylcysteine (NAC), the FDA-approved antidote to AAP overdose, has demonstrated promising antitumor efficacy in early phase clinical trials. However, the mechanism of action (MOA) of AAP's anticancer effects remains elusive. Using clinically relevant AAP concentrations, we evaluated cancer stem cell (CSC) phenotype in vitro and in vivo in lung cancer and melanoma cells with diverse driver mutations. Associated mechanisms were also studied. Our results demonstrated that AAP inhibited 3D spheroid formation, self-renewal, and expression of CSC markers when human cancer cells were grown in serum-free CSC media. Similarly, anti-CSC activity was demonstrated in vivo in xenograft models - tumor formation following in vitro treatment and ex-vivo spheroid formation following in vivo treatment. Intriguingly, NAC, used to mitigate AAP's liver toxicity, did not rescue cells from AAP's anti-CSC effects, and AAP failed to reduce glutathione levels in tumor xenograft in contrast to mice liver tissue suggesting nonglutathione-related MOA. In fact, AAP mediates its anti-CSC effect via inhibition of STAT3. AAP directly binds to STAT3 with an affinity in the low micromolar range and a high degree of specificity for STAT3 relative to STAT1. These findings have high immediate translational significance concerning advancing AAP with NAC rescue to selectively rescue hepatotoxicity while inhibiting CSCs. The novel mechanism of selective STAT3 inhibition has implications for developing rational anticancer combinations and better patient selection (predictive biomarkers) for clinical studies and developing novel selective STAT3 inhibitors using AAP's molecular scaffold.

Plasticity in Colorectal Cancer: Why Cancer Cells Differentiate

Simple Summary

The cancer stem cell hypothesis postulates that tumors arise from a few cells with self-renewal capabilities. The identification of stem cell markers, the development of mouse and human tumor organoids and their application in mouse models, allowing lineage tracing, helped to better understand the cancer stem cell model as well as the role of differentiation. This review aims at providing insights on the interplay between cancer stem cells and differentiated cells, as well as the importance of plasticity between the two states.

Abstract

The cancer stem cell hypothesis poses that the bulk of differentiated cells are non-tumorigenic and only a subset of cells with self-renewal capabilities drive tumor initiation and progression. This means that differentiation could have a tumor-suppressive effect. Accumulating evidence shows, however, that in some solid tumors, like colorectal cancer, such a hierarchical organization is necessary. The identification of Lgr5 as a reliable marker of normal intestinal epithelial stem cells, together with strategies to trace cell lineages within tumors and the possibility to selectively ablate these cells, have proven the relevance of Lgr5⁺ cells for cancer progression. On the contrary, the role of Lgr5⁻ cells during this process remains largely unknown. In this review, we explore available evidence pointing towards possible selective advantages of cancer cells organized hierarchically and its resulting cell heterogeneity. Clear evidence of plasticity between cell states, in which loss of Lgr5⁺ cells can be replenished by dedifferentiation of Lgr5⁻ cells, shows that cell hierarchies could grant adaptive traits to tumors upon changing selective pressures, including those derived from anticancer therapy, as well as during tumor progression to metastasis.

HDAC11 Regulates Glycolysis through the LKB1/AMPK Signaling Pathway to Maintain Hepatocellular Carcinoma Stemness

Hepatocellular carcinoma (HCC) contains a subset of cancer stem cells (CSC) that cause tumor recurrence, metastasis, and chemical resistance. Histone deacetylase 11 (HDAC11) mediates diverse immune functions and metabolism, yet little is known about its role in HCC CSCs. In this study, we report that HDAC11 is highly expressed in HCC and is closely related to disease prognosis. Depletion of HDAC11 in a conditional knockout mouse model reduced hepatocellular tumorigenesis and prolonged survival. Loss of HDAC11 increased transcription of LKB1 by promoting histone acetylation in its promoter region, thereby activating the AMPK signaling pathway and inhibiting the glycolysis pathway, which in turn leads to the suppression of cancer stemness and HCC progression. Furthermore, HDAC11 overexpression reduced HCC sensitivity to sorafenib. Collectively, these data propose HDAC11 as a new target for combination therapy in patients with kinase-resistant HCC. SIGNIFICANCE: This study finds that HDAC11 suppresses LKB1 expression in HCC to promote cancer stemness, progression, and sorafenib resistance, suggesting the potential of targeting HDAC11 to treat HCC and overcome kinase inhibitor resistance.

The Role of Cancer Stem Cells in Drug Resistance in Gastroesophageal Junction Adenocarcinoma

Gastroesophageal junction adenocarcinomas (GEJA) have dramatically increased in incidence in the western world since the mid-20^th century. Their prognosis is poor, and conventional anti-cancer therapies do not significantly improve survival outcomes. These tumours are comprised of a heterogenous population of both cancer stem cells (CSC) and non-CSCs, with the former playing a crucial role in tumorigenesis, metastasis and importantly drug resistance. Due to the ability of CSCs to self-replicate indefinitely, their resistance to anti-cancer therapies poses a significant barrier to effective treatment of GEJA. Ongoing drug development programmes aim to target and eradicate CSCs, however their characterisation and thus identification is difficult. CSC regulation is complex, involving an array of signalling pathways, which are in turn influenced by a number of entities including epithelial mesenchymal transition (EMT), microRNAs (miRNAs), the tumour microenvironment and epigenetic modifications. Identification of CSCs commonly relies on the expression of specific cell surface markers, yet these markers vary between different malignancies and indeed are often co-expressed in non-neoplastic tissues. Development of targeted drug therapies against CSCs thus requires an understanding of disease-specific CSC markers and regulatory mechanisms. This review details the current knowledge regarding CSCs in GEJA, with particular emphasis on their role in drug resistance.

Cancer stem cells and macrophages: molecular connections and future perspectives against cancer

Cancer stem cells (CSCs) have been considered the key drivers of cancer initiation and progression due to their unlimited self-renewal capacity and their ability to induce tumor formation. Macrophages, particularly tumor-associated macrophages (TAMs), establish a tumor microenvironment to protect and induce CSCs development and dissemination. Many studies in the past decade have been performed to understand the molecular mediators of CSCs and TAMs, and several studies have elucidated the complex crosstalk that occurs between these two cell types. The aim of this review is to define the complex crosstalk between these two cell types and to highlight potential future anti-cancer strategies.

Epigenetic dynamics in cancer stem cell dormancy

Cancer remains one of the most challenging diseases despite significant advances of early diagnosis and therapeutic treatments. Cancerous tumors are composed of various cell types including cancer stem cells capable of self-renewal, proliferation, differentiation, and invasion of distal tumor sites. Most notably, these cells can enter a dormant cellular state that is resistant to conventional therapies. Thereby, cancer stem cells have the intrinsic potential for tumor initiation, tumor growth, metastasis, and tumor relapse after therapy. Both genetic and epigenetic alterations are attributed to the formation of multiple tumor types. This review is focused on how epigenetic dynamics involving DNA methylation and DNA oxidations are implicated in breast cancer and glioblastoma multiforme. The emergence and progression of these cancer types rely on cancer stem cells with the capacity to enter quiescence also known as a dormant cellular state, which dictates the distinct tumorigenic aggressiveness between breast cancer and glioblastomas.

Possible Beneficial Effects of N-Acetylcysteine for Treatment of Triple-Negative Breast Cancer

N-acetylcysteine (NAC) is a widely used antioxidant with therapeutic potential. However, the cancer-promoting effect of NAC observed in some preclinical studies has raised concerns regarding its clinical use. Reactive oxygen species (ROS) can mediate signaling that results in both cancer-promoting and cancer-suppressing effects. The beneficial effect of NAC may depend on whether the type of cancer relies on ROS signaling for its survival and metastasis. Triple-negative breast cancer (TNBC) has aggressive phenotypes and is currently treated with standard chemotherapy as the main systemic treatment option. Particularly, basal-like TNBC cells characterized by inactivated BRCA1 and mutated TP53 produce high ROS levels and rely on ROS signaling for their survival and malignant progression. In addition, the high ROS levels in TNBC cells can mediate the interplay between cancer cells and the tissue microenvironment (TME) to trigger the recruitment and conversion of stromal cells and induce hypoxic responses, thus leading to the creation of cancer-supportive TMEs and increased cancer aggressiveness. However, NAC treatment effectively reduces the ROS production and ROS-mediated signaling that contribute to cell survival, metastasis, and drug resistance in TNBC cells. Therefore, the inclusion of NAC in standard chemotherapy could probably provide additional benefits for TNBC patients.

Cancer Stem Cells-Key Players in Tumor Relapse

Tumor relapse and treatment failure are unfortunately common events for cancer patients, thus often rendering cancer an uncurable disease. Cancer stem cells (CSCs) are a subset of cancer cells endowed with tumor-initiating and self-renewal capacity, as well as with high adaptive abilities. Altogether, these features contribute to CSC survival after one or multiple therapeutic approaches, thus leading to treatment failure and tumor progression/relapse. Thus, elucidating the molecular mechanisms associated with stemness-driven resistance is crucial for the development of more effective drugs and durable responses. This review will highlight the mechanisms exploited by CSCs to overcome different therapeutic strategies, from chemo- and radiotherapies to targeted therapies and immunotherapies, shedding light on their plasticity as an insidious trait responsible for their adaptation/escape. Finally, novel CSC-specific approaches will be described, providing evidence of their preclinical and clinical applications.

Dll1+ quiescent tumor stem cells drive chemoresistance in breast cancer through NF-κB survival pathway

Development of chemoresistance in breast cancer patients greatly increases mortality. Thus, understanding mechanisms underlying breast cancer resistance to chemotherapy is of paramount importance to overcome this clinical challenge. Although activated Notch receptors have been associated with chemoresistance in cancer, the specific Notch ligands and their molecular mechanisms leading to chemoresistance in breast cancer remain elusive. Using conditional knockout and reporter mouse models, we demonstrate that tumor cells expressing the Notch ligand Dll1 is important for tumor growth and metastasis and bear similarities to tumor-initiating cancer cells (TICs) in breast cancer. RNA-seq and ATAC-seq using reporter models and patient data demonstrated that NF-κB activation is downstream of Dll1 and is associated with a chemoresistant phenotype. Finally, pharmacological blocking of Dll1 or NF-κB pathway completely sensitizes Dll1⁺ tumors to chemotherapy, highlighting therapeutic avenues for chemotherapy resistant breast cancer patients in the near future.

Reversal of cisplatin sensitization and abrogation of cisplatin-enriched cancer stem cells in 5-8F nasopharyngeal carcinoma cell line through a suppression of Wnt/β-catenin-signaling pathway

Nasopharyngeal carcinoma (NPC) is one of the rare cancers in western countries but predominant in Southeast Asian countries including Thailand. One major cause for failure of NPC chemotherapeutic treatments is reportedly correlated with the elevation of cancer stem cell (CSC) fractions. Thus, this present study aims to investigate the effect of cisplatin (CDDP) treatment on the enrichment of cancer stem-like cells (CSCs) and its associated signaling pathway in EBV-negative NPC cells. Cisplatin-pretreated 5-8F NPC cells (5-8F CDDP) were first generated by treating the cells with 0.5 μM cisplatin for 48 h. After the instant treatment, 5-8F CDDP showed increased IC₅₀ values, demonstrating a decrease in CDDP sensitization. Besides, the proportion of NPC cells with cancer stem-like phenotypes comprising side population (SP), key stemness-related gene expressions including SOX2, ALDH1, CD24 was significantly enhanced. Additionally, 5-8F CDDP displayed the upregulation of β-catenin gene, suggesting its association with the CSC-initiating mechanism. Furthermore, a tankyrase inhibitor for Wnt/β-catenin pathway, XAV939, substantially reduced CSCs and retrieved the cisplatin sensitivity in 5-8F CDDP. This confirms that the Wnt/β-catenin signaling is accountable for rising of the CSC population in EBV-negative NPC. Finally, the combined treatment of CDDP and XAV939 exhibited lower 5-8F CDDP cell viability compared to the treatment of CDDP alone, suggesting the reversal of cisplatin sensitization. In conclusion, the enhancement of CSCs in 5-8F NPC cells caused by the instant cisplatin treatment is initially mediated through the upregulation of β-catenin and activation of Wnt/β-catenin signaling pathway. As a result, a primary chemotherapeutic treatment with closely monitoring the targeted Wnt/β-catenin signaling pathway could potentially prevent the development of CSCs and improve the treatment efficiency in NPC.

Circular RNAs as biomarkers and therapeutic targets in cancer

Circular RNAs (circRNAs) are a class of single-stranded closed non-coding RNA molecules (ncRNAs), which are formed as a result of reverse splicing of mRNAs. Despite their relative abundance, an interest in understanding their regulatory importance is rather recent. High stability, abundance and evolutionary conservation among species underline some of their important traits. CircRNAs perform a variety of cellular functions ranging from miRNA and proteins sponges to transcriptional modulation and splicing. Additionally, most circRNAs are expressed aberrantly in pathological conditions suggesting their possible exploitation as diagnostic biomarkers. Their covalent closed cyclic structure resulting in resistance to RNases further makes them suitable as cancer biomarkers. Studies involving human tumors have verified differences in the expression profiles of circRNAs, indicating a regulatory role in cancer pathogenesis and metastasis. As endogenous competitive RNA, circRNAs can regulate tumor proliferation and invasion. Further, some circRNAs located in the nucleus can regulate transcription of genes by binding to RNA polymerase II. In this review, we elaborate the characteristics, functions and mechanisms of action of circRNAs in cancer. We also discuss the possibility of using circRNAs as potential therapeutic targets and biomarkers for cancer.

Potential roles and prognostic significance of exosomes in cancer drug resistance

Drug resistance is a major impediment in cancer therapy which strongly reduces the efficiency of anti-cancer drugs. Exosomes are extracellular vesicles with cup or spherical shape with a size range of 40-150 nm released by eukaryotic cells that contain genetic materials, proteins, and lipids which mediate a specific cell-to-cell communication. The potential roles of exosomes in intrinsic and acquired drug resistance have been reported in several studies. Furthermore, a line of evidence suggested that the content of exosomes released from tumor cells in biological samples may be associated with the clinical outcomes of cancer patients. In this review, we highlighted the recent studies regarding the potential roles of exosomes in tumor initiation, progression, and chemoresistance. This study suggests the possible role of exosomes for drug delivery and their contents in prognosis and resistance to chemotherapy in cancer patients.

Effect of Menadione and Combination of Gemcitabine and Cisplatin on Cancer Stem Cells in Human Non-small Cell Lung Cancer (NSCLC) Cell Line A549

Non-small cell lung cancer (NSCLC) is the most common type of lung cancer. Chemotherapy-induced adverse effects and resistance of NSCLC to conventional drugs reduce the efficacy of current therapies. Tumors contain a small population of cancer stem cells (CSCs) that play a critical role in tumor initiation, maintenance, and drug resistance that finally lead to cancer recurrence. Therefore, CSC-targeting therapies can offer the best hope for developing curative cancer therapies. Vitamins have a high potential for cancer prevention and treatment. Vitamins also ameliorate the side effects which occur in chemo-radio therapy. Menadione (2-methyl-1,4-naphthoquinone/vitamin-K3) is a synthetic form of vitamin K that indicated antitumor activities. The purpose of this study was to evaluate the anti-CSCs effect of menadione and combination of cisplatin and gemcitabine as a first-line treatment in patients with NSCLC on the NSCLC cell line A549. MTT results displayed decreased cell survival after treatment with cisplatin/gemcitabine for 48 h treatment (IC₅₀ values 0.25 µM for cisplatin and 5 µM for gemcitabine). Menadione also inhibited the cell growth in A549 cells (IC₅₀: 16 µM). Quantitative RT-PCR showed significant downregulation of CSC markers (Oct4, Nanog, Sox2, Aldh1, Abcb1, CD44, and CD133) and Snail, epithelial-mesenchymal transition marker, after treatment with menadione and cisplatin/gemcitabine. Flow cytometry showed CD44-positive cells that constitute a high percentage (70%) of A549 cells reduced significantly after treatment with cisplatin/gemcitabine or menadione. However, A549 cells did not show a significant population positive for CD133 and ABCB1 (less than 0.05%), and these fractions did not change after treatment with two agents.

Breast Cancer Metastasis

Owing to increased awareness of the importance of mammogram and advances in surgical technology, survival rate of patients with primary breast cancer has dramatically increased. Despite all these advances in breast cancer treatment, there are no currently available treatments for this disease once it metastasizes to distant organs including bones, lungs, brain, and liver. This is mainly attributed to the complexity of metastatic process. Recent advances in technology enabled cancer biologists to dissect each step of the metastatic process, and this led to discovery of major players and molecules in this process. In this section, we will discuss recent discovery and advances in the field of breast cancer metastasis research.

MicroRNA-Assisted Hormone Cell Signaling in Colorectal Cancer Resistance

Despite substantial progress in cancer therapy, colorectal cancer (CRC) is still the third leading cause of cancer death worldwide, mainly due to the acquisition of resistance and disease recurrence in patients. Growing evidence indicates that deregulation of hormone signaling pathways and their cross-talk with other signaling cascades inside CRC cells may have an impact on therapy resistance. MicroRNAs (miRNAs) are small conserved non-coding RNAs thatfunction as negative regulators in many gene expression processes. Key studies have identified miRNA alterations in cancer progression and drug resistance. In this review, we provide a comprehensive overview and assessment of miRNAs role in hormone signaling pathways in CRC drug resistance and their potential as future targets for overcoming resistance to treatment.

Cancer Stem Cell Microenvironment Models with Biomaterial Scaffolds In Vitro

Defined by its potential for self-renewal, differentiation and tumorigenicity, cancer stem cells (CSCs) are considered responsible for drug resistance and relapse. To understand the behavior of CSC, the effects of the microenvironment in each tissue are a matter of great concerns for scientists in cancer biology. However, there are many complicated obstacles in the mimicking the microenvironment of CSCs even with current advanced technology. In this context, novel biomaterials have widely been assessed as in vitro platforms for their ability to mimic cancer microenvironment. These efforts should be successful to identify and characterize various CSCs specific in each type of cancer. Therefore, extracellular matrix scaffolds made of biomaterial will modulate the interactions and facilitate the investigation of CSC associated with biological phenomena simplifying the complexity of the microenvironment. In this review, we summarize latest advances in biomaterial scaffolds, which are exploited to mimic CSC microenvironment, and their chemical and biological requirements with discussion. The discussion includes the possible effects on both cells in tumors and microenvironment to propose what the critical factors are in controlling the CSC microenvironment focusing the future investigation. Our insights on their availability in drug screening will also follow the discussion.

Suppression of poised oncogenes by ZMYND8 promotes chemo-sensitization

The major challenge in chemotherapy lies in the gain of therapeutic resistance properties of cancer cells. The relatively small fraction of chemo-resistant cancer cells outgrows and are responsible for tumor relapse, with acquired invasiveness and stemness. We demonstrate that zinc-finger MYND type-8 (ZMYND8), a putative chromatin reader, suppresses stemness, drug resistance, and tumor-promoting genes, which are hallmarks of cancer. Reinstating ZMYND8 suppresses chemotherapeutic drug doxorubicin-induced tumorigenic potential (at a sublethal dose) and drug resistance, thereby resetting the transcriptional program of cells to the epithelial state. The ability of ZMYND8 to chemo-sensitize doxorubicin-treated metastatic breast cancer cells by downregulating tumor-associated genes was further confirmed by transcriptome analysis. Interestingly, we observed that ZMYND8 overexpression in doxorubicin-treated cells stimulated those involved in a good prognosis in breast cancer. Consistently, sensitizing the cancer cells with ZMYND8 followed by doxorubicin treatment led to tumor regression in vivo and revert back the phenotypes associated with drug resistance and stemness. Intriguingly, ZMYND8 modulates the bivalent or poised oncogenes through its association with KDM5C and EZH2, thereby chemo-sensitizing the cells to chemotherapy for better disease-free survival. Collectively, our findings indicate that poised chromatin is instrumental for the acquisition of chemo-resistance by cancer cells and propose ZMYND8 as a suitable epigenetic tool that can re-sensitize the chemo-refractory breast carcinoma.

Wnt/β‑catenin signaling: Causes and treatment targets of drug resistance in colorectal cancer (Review)

Colorectal cancer (CRC) is the third most common malignant tumor in humans. Chemotherapy is used for the treatment of CRC. However, the effect of chemotherapy remains unsatisfactory due to drug resistance. Growing evidence has shown that the presence of highly metastatic tumor stem cells, regulation of non-coding RNAs and the tumor microenvironment contributes to drug resistance mechanisms in CRC. Wnt/β-catenin signaling mediates the chemoresistance of CRC in these three aspects. Therefore, the present study analyzed the abundant evidence of the contribution of Wnt/β-catenin signaling to the development of drug resistance in CRC and discussed its possible role in improving the chemosensitivity of CRC, which may provide guidelines for its clinical treatment.

Long Noncoding RNA DANCR Activates Wnt/β-Catenin Signaling through MiR-216a Inhibition in Non-Small Cell Lung Cancer

Long noncoding RNA differentiation antagonizing nonprotein coding RNA (lncRNA-DANCR) is associated with poor prognosis in multiple cancers, and promotes cancer stemness and invasion. However, the exact mechanisms by which DANCR promotes non-small cell lung cancer (NSCLC) remain elusive. In this study, we determined that DANCR knockdown (KD) impeded cell migration and reduced stem-like characteristics in two NSCLC cell lines, A549 and H1755. Wnt signaling was shown to promote NSCLC proliferation, stemness, and invasion; therefore, we hypothesized that DANCR may regulate these activities through induction of the Wnt/β-catenin pathway. DANCR KD reduced β-catenin signaling and protein expression, and decreased the expression of β-catenin gene targets c-Myc and Axin2. One of the well-defined functions of lncRNAs is their ability to bind and inhibit microRNAs. Through in silico analysis, we identified tumor suppressor miR-216a as a potential binding partner to DANCR, and confirmed this binding through coimmunoprecipitation and luciferase-reporter assays. Furthermore, we show that DANCR-induced β-catenin protein expression may be blocked with miR-216a overexpression. Our findings illustrate a role of DANCR in NSCLC migration and stemness, and suggest a novel DANCR/miR-216a signaling axis in the Wnt/β-catenin pathway.

Survival impact of extended cycles of second-line chemotherapy in platinum-sensitive relapsed ovarian cancer patients with residual tumor after six cycles

Background

To determine if extended chemotherapy improves survival outcomes in patients with platinum-sensitive relapsed epithelial ovarian cancer (EOC) who have residual disease after six cycles of second-line chemotherapy.

Methods

In this study, 135 EOC patients who experienced platinum-sensitive recurrence after primary treatment between 2008 and 2018, and had a residual tumor ≥0.5 cm (detected on CT scans) after completing six cycles of second-line, platinum-based chemotherapy, were retrospectively reviewed. Based on the number of main therapy cycles (second-line chemotherapy), we divided patients into an extended group (>6 cycles, n = 52) or a standard group (6 cycles, n = 83) and compared patient characteristics and survival outcomes between these groups.

Results

The extended group had a shorter platinum-free interval after primary treatment than the standard group (median, 11.0 vs. 13.1 months; P = 0.018). Secondary debulking surgery was less frequently performed in the standard group (1.9% vs. 19.3%; P = 0.003). After six chemotherapy cycles, the extended and standard groups showed similar serum CA-125 levels (P = 0.122) and residual tumor sizes (P = 0.232). There was no difference in overall survival (OS) between the groups (P = 0.382), although the extended group had significantly worse progression-free survival (PFS) than the standard group (median, 13.9 vs. 15.1 months; P = 0.012). Multivariate analyses revealed that platinum-free interval was an independent prognostic factor for PFS and OS, but extended chemotherapy was not (PFS: HR, 1.25; 95% CI, 0.84–1.85; P = 0.279; and OS: HR, 1.36; 95% CI, 0.72–2.56; P = 0.342). We observed consistent results in the subset of patients who did not undergo secondary debulking surgery.

Conclusions

More than six cycles of platinum-based chemotherapy might not improve survival outcomes in patients with platinum-sensitive recurrent EOC who had a residual tumor ≥0.5 cm after six cycles of second-line chemotherapy.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-020-07658-8.

Report of the National Cancer Institute and the Eunice Kennedy Shriver National Institute of Child Health and Human Development-sponsored workshop: gynecology and women's health-benign conditions and cancer

The Division of Cancer Prevention and the Division of Cancer Biology at the National Cancer Institute and the Gynecologic Health and Disease Branch in the National Institute of Child Health and Human Development organized a workshop in April 2019 to explore current insights into the progression of gynecologic cancers from benign conditions. Working groups were formed based on 3 gynecologic disease types: (1) Endometriosis or Endometrial Cancer and Endometrial-Associated Ovarian Cancer, (2) Uterine Fibroids (Leiomyoma) or Leiomyosarcoma, and (3) Adenomyosis or Adenocarcinoma. In this report, we highlight the key questions and current challenges that emerged from the working group discussions and present potential research opportunities that may advance our understanding of the progression of gynecologic benign conditions to cancer.

Tumor heterogeneity in muscle-invasive bladder cancer

Muscle-invasive bladder cancer (MIBC), a highly heterogeneous disease, shows genomic instability and a high mutation rate. Clinical outcomes are variable and responses to conventional chemotherapy differ among patients (due to inter-patient tumor heterogeneity and inter-tumor heterogeneity) and even within each individual tumor (intra-tumor heterogeneity). Emerging evidence indicates that tumor heterogeneity may play an important role in cancer progression, resistance to therapy, and metastasis. Comprehensive molecular subtyping classifies MIBC into distinct categories that have potential to guide prognosis, patient stratification, and treatment. Genomic characterization of time-series analyses at the single cell level, and of cell-free circulating tumor DNA or circulating tumor cells, are emerging technologies that enable dissection of the complex clonal architecture of MIBC. This review provides insight into the clinical significance of the molecular mechanisms underlying heterogeneity, focusing on inter- and intra-tumor heterogeneity, with special emphasis on molecular classification and methods used to analyze the complex patterns involved.

Resveratrol, cancer and cancer stem cells: A review on past to future

Cancer remains to be an unresolved medical challenge despite of tremendous advancement in basic science research and clinical medicine. One of the major limitations is due to the side effects of chemotherapy which remains to be palliative without offering any permanent cure for cancer. Cancer stem cells (CSCs) are the subpopulation of cells in tumors that remain viable even after surgery, chemo- and radio-therapy that eventually responsible for tumor relapse. Hence, by eliminating non-stem cancer cells and cancer stem cells from the patient, permanent cure is expected. Phytochemicals have been under the intensive study to target these CSCs effectively and permanently as they do not cause any side effects. Resveratrol (RSV) is one such compound attaining lot of interest in recent days to target CSCs either alone or in combination. RSV has been used by several researchers to target cancer cells in a variety of disease models, however its CSC targeting abilities are under intensive study at present. This review is to summarize the effects of RSV under in vitro and in vivo conditions along with advantages and disadvantages of its uses against cancer cells and cancer stem cells. From the first reports on phytochemical applications against cancer and cancer stem cells in 1997 and 2002 respectively followed by later reports, up to date observations and developments are enlisted from PubMed in this comprehensive review. RSV is shown to be a potential compound having impact on altering the signal transduction pathways in cancer cells. However, the effects are variable under in vitro and in vivo conditions, and also with its use alone or in combination with other small molecules. Past research on RSV is emphasizing the importance of in vivo experimental models and clinical trials with different prospective combinations, is a hope for future promising treatment regimen.

Drug Delivery Systems Using Surface Markers for Targeting Cancer Stem Cells

The innate abilities of cancer stem cells (CSCs), such as multi-drug resistance, drug efflux, quiescence and ionizing radiation tolerance, protect them from most traditional chemotherapeutics. As a result, this small subpopulation of persistent cells leads to more aggressive and chemoresistant cancers, causing tumour relapse and metastasis. This subpopulation is differentiated from the bulk tumour population through a wide variety of surface markers expressed on the cell surface. Recent developments in nanomedicine and targeting delivery methods have given rise to new possibilities for specifically targeting these markers and preferentially eliminating CSCs. Herein, we first summarize the range of surface markers identifying CSC populations in a variety of cancers; then, we discuss recent attempts to actively target CSCs and their niches using liposomal, nanoparticle, carbon nanotube and viral formulations.

Astaxanthin Reduces Stemness Markers in BT20 and T47D Breast Cancer Stem Cells by Inhibiting Expression of Pontin and Mutant p53

Astaxanthin (AST) is a product made from marine organisms that has been used as an anti-cancer supplement. It reduces pontin expression and induces apoptosis in SKBR3, a breast cancer cell line. Using Western blotting and qRT-PCR analyses, this study revealed that in the T47D and BT20 breast cancer cell lines, AST inhibits expression of pontin and mutp53, as well as the Oct4 and Nanog cancer stem cell (CSC) stemness genes. In addition, we explored the mechanism by which AST eradicates breast cancer cells using pontin siRNAs. Pontin knockdown by pontin siRNA reduced proliferation, Oct4 and Nanog expression, colony and spheroid formation, and migration and invasion abilities in breast cancer cells. In addition, reductions in Oct4, Nanog, and mutp53 expression following rottlerin treatment confirmed the role of pontin in these cells. Therefore, pontin may play a central role in the regulation of CSC properties and in cell proliferation following AST treatment. Taken together, these findings demonstrate that AST can repress CSC stemness genes in breast cancer cells, which implies that AST therapy could be used to improve the efficacy of other anti-cancer therapies against breast cancer cells.

Mechanisms of docetaxel resistance in prostate cancer: The key role played by miRNAs

One of the main problems with the treatment of metastatic prostate cancer is that, despite an initial positive response, the majority of patients develop resistance and progress. In particular, the resistance to docetaxel, the gold standard therapy for metastatic prostate cancer since 2010, represents one of the main factors responsible for the failure of prostate cancer therapy. According to the present knowledge, different processes contribute to the appearance of docetaxel resistance and non-coding RNA seems to play a relevant role in them. In this review, a comprehensive overview of the miRNA network involved in docetaxel resistance is described, highlighting the pathway/s affected by their activity.

Mutant p53 in Cancer Progression and Targeted Therapies

TP53 is the most frequently mutated tumor suppressor gene in human cancer. The majority of mutations of p53 are missense mutations, leading to the expression of the full length p53 mutant proteins. Mutant p53 (Mutp53) proteins not only lose wild-type p53-dependent tumor suppressive functions, but also frequently acquire oncogenic gain-of-functions (GOF) that promote tumorigenesis. In this review, we summarize the recent advances in our understanding of the oncogenic GOF of mutp53 and the potential therapies targeting mutp53 in human cancers. In particular, we discuss the promising drugs that are currently under clinical trials as well as the emerging therapeutic strategies, including CRISPR/Cas9 based genome edition of mutant TP53 allele, small peptide mediated restoration of wild-type p53 function, and immunotherapies that directly eliminate mutp53 expressing tumor cells.

Breast cancer organoid model allowed to reveal potentially beneficial combinations of 3,3'-diindolylmethane and chemotherapy drugs

Epigenetic alterations represent promising therapeutic targets in cancer treatment. Recently it was revealed that small molecules have the potential to act as microRNA silencers. Capacity to bind the discrete stem-looped structure of pre-miR-21 and prevent its maturation opens opportunities to utilize such compounds for the prevention of initiation, progression, and chemoresistance of cancer. Molecular simulations performed earlier identified 3,3'-diindolylmethane (DIM) as a potent microRNA-21 antagonist. However, data on DIM and microRNA-21 interplay is controversial, which may be caused by the limitations of the cell lines.

Therapy Resistance, Cancer Stem Cells and ECM in Cancer: The Matrix Reloaded

The extracellular matrix (ECM) has remained an enigmatic component of the tumor microenvironment. It drives metastasis via its interaction with the integrin signaling pathway, contributes to tumor progression and confers therapy resistance by providing a physical barrier around the tumor. The complexity of the ECM lies in its heterogeneous composition and complex glycosylation that can provide a support matrix as well as trigger oncogenic signaling pathways by interacting with the tumor cells. In this review, we attempt to dissect the role of the ECM in enriching for the treatment refractory cancer stem cell population and how it may be involved in regulating their metabolic needs. Additionally, we discuss how the ECM is instrumental in remodeling the tumor immune microenvironment and the potential ways to target this component in order to develop a viable therapy.

SMAR1 repression by pluripotency factors and consequent chemoresistance in breast cancer stem-like cells is reversed by aspirin

The high abundance of drug efflux pumps in cancer stem cells (CSCs) contributes to chemotherapy resistance. The transcriptional regulator SMAR1 suppresses CSC expansion in colorectal cancer, and increased abundance of SMAR1 is associated with better prognosis. Here, we found in breast tumors that the expression of SMAR1 was decreased in CSCs through the cooperative interaction of the pluripotency factors Oct4 and Sox2 with the histone deacetylase HDAC1. Overexpressing SMAR1 sensitized CSCs to chemotherapy through SMAR1-dependent recruitment of HDAC2 to the promoter of the gene encoding the drug efflux pump ABCG2. Treating cultured CSCs or 4T1 tumor-bearing mice with the nonsteroidal anti-inflammatory drug aspirin restored SMAR1 expression and ABCG2 repression and enhanced tumor sensitivity to doxorubicin. Our findings reveal transcriptional mechanisms regulating SMAR1 that also regulate cancer stemness and chemoresistance and suggest that, by restoring SMAR1 expression, aspirin might enhance chemotherapeutic efficacy in patients with stem-like tumors.

Cancer-Associated Stemness and Epithelial-to-Mesenchymal Transition Signatures Related to Breast Invasive Carcinoma Prognostic

Simple Summary

Breast cancer is one of the most common oncological diseases in women, as its incidence is rapidly growing. In this study, we have investigated the mechanism of epithelial-to-mesenchymal transition (EMT) and cancer stem cells (CSCs), demonstrating presence of an interconnectedness between them. This interconnectedness plays important roles in patient prognostic, as well as in diagnostic and therapeutic targets. It is identified that there is a common signature between CSCs and EMT, and this is represented by ALDH1A1, SFRP1, miR-139, miR-21, and miR-200c. This finding will provide a better understanding of this mechanism, and will facilitate the development of novel treatment options.

Abstract

Breast cancer is one of the most common oncological diseases in women, as its incidence is rapidly growing, rendering it unpredictable and causing more harm than ever before on an annual basis. Alterations of coding and noncoding genes are related to tumorigenesis and breast cancer progression. In this study, several key genes associated with epithelial-to-mesenchymal transition (EMT) and cancer stem cell (CSC) features were identified. EMT and CSCs are two key mechanisms responsible for self-renewal, differentiation, and self-protection, thus contributing to drug resistance. Therefore, understanding of the relationship between these processes may identify a therapeutic vulnerability that can be further exploited in clinical practice, and evaluate its correlation with overall survival rate. To determine expression levels of altered coding and noncoding genes, The Cancer Omics Atlas (TCOA) are used, and these data are overlapped with a list of CSCs and EMT-specific genes downloaded from NCBI. As a result, it is observed that CSCs are reciprocally related to EMT, thus identifying common signatures that allow for predicting the overall survival for breast cancer genes (BRCA). In fact, common CSCs and EMT signatures, represented by ALDH1A1, SFRP1, miR-139, miR-21, and miR-200c, are deemed useful as prognostic biomarkers for BRCA. Therefore, by mapping changes in gene expression across CSCs and EMT, suggesting a cross-talk between these two processes, we have been able to identify either the most common or specific genes or miRNA markers associated with overall survival rate. Thus, a better understanding of these mechanisms will lead to more effective treatment options.

Cancer stem cell secretome in the tumor microenvironment: a key point for an effective personalized cancer treatment

Cancer stem cells (CSCs) represent a tumor subpopulation responsible for tumor metastasis and resistance to chemo- and radiotherapy, ultimately leading to tumor relapse. As a consequence, the detection and eradication of this cell subpopulation represent a current challenge in oncology medicine. CSC phenotype is dependent on the tumor microenvironment (TME), which involves stem and differentiated tumor cells, as well as different cell types, such as mesenchymal stem cells, endothelial cells, fibroblasts and cells of the immune system, in addition to the extracellular matrix (ECM), different in composition to the ECM in healthy tissues. CSCs regulate multiple cancer hallmarks through the interaction with cells and ECM in their environment by secreting extracellular vesicles including exosomes, and soluble factors such as interleukins, cytokines, growth factors and other metabolites to the TME. Through these factors, CSCs generate and activate their own tumor niche by recruiting stromal cells and modulate angiogenesis, metastasis, resistance to antitumor treatments and their own maintenance by the secretion of different factors such as IL-6, VEGF and TGF-ß. Due to the strong influence of the CSC secretome on disease development, the new antitumor therapies focus on targeting these communication networks to eradicate the tumor and prevent metastasis, tumor relapse and drug resistance. This review summarizes for the first time the main components of the CSC secretome and how they mediate different tumor processes. Lastly, the relevance of the CSC secretome in the development of more precise and personalized antitumor therapies is discussed.

Brachyury Is Associated with Glioma Differentiation and Response to Temozolomide

Glioblastomas (GBMs) are the most aggressive tumor type of the central nervous system, mainly due to their high invasiveness and innate resistance to radiotherapy and chemotherapy, with temozolomide (TMZ) being the current standard therapy. Recently, brachyury was described as a novel tumor suppressor gene in gliomas, and its loss was associated with increased gliomagenesis. Here, we aimed to explore the role of brachyury as a suppressor of glioma invasion, stem cell features, and resistance to TMZ. Using gene-edited glioma cells to overexpress brachyury, we found that brachyury-positive cells exhibit reduced invasive and migratory capabilities and stem cell features. Importantly, these brachyury-expressing cells have increased expression of differentiation markers, which corroborates the results from human glioma samples and in vivo tumors. Glioma cells treated with retinoic acid increased the differentiation status with concomitant increased expression of brachyury. We then selected TMZ-resistant (SNB-19) and TMZ-responsive (A172 and U373) cell lines to evaluate the role of brachyury in the response to TMZ treatment. We observed that both exogenous and endogenous brachyury activation, through overexpression and retinoic acid treatment, are associated with TMZ sensitization in glioma-resistant cell lines. In this study, we demonstrate that brachyury expression can impair aggressive glioma features associated with treatment resistance. Finally, we provide the first evidence that brachyury can be a potential therapeutic target in GBM patients who do not respond to conventional chemotherapeutic drugs.

MicroRNAs as mediators of drug resistance mechanisms

MicroRNAs are small RNA transcripts involved in fine-tuning of several cellular mechanisms and pathways crucial for maintaining cells' homeostasis like apoptosis, differentiation, inflammation and cell-cycle regulation. They act by regulation of gene expression at post-transcriptional level through fine-tuning of target proteins expression. Expression of microRNAs is cell-type specific and since their discovery they have been proven to be deregulated in various disorders including cancer. Several lines of evidence are emerging that link microRNAs to drug resistance mechanisms in tumours given their important role in modulating oncogenic and tumour suppressive mechanisms. This review will focus on latest knowledge of the roles and mechanisms of microRNAs as mediators to drug resistance and the implications for future therapies.

A Marine Collagen-Based Biomimetic Hydrogel Recapitulates Cancer Stem Cell Niche and Enhances Progression and Chemoresistance in Human Ovarian Cancer

Recent attention has focused on the development of an effective three-dimensional (3D) cell culture system enabling the rapid enrichment of cancer stem cells (CSCs) that are resistant to therapies and serving as a useful in vitro tumor model that accurately reflects in vivo behaviors of cancer cells. Presently, an effective 3D in vitro model of ovarian cancer (OC) was developed using a marine collagen-based hydrogel. Advantages of the model include simplicity, efficiency, bioactivity, and low cost. Remarkably, OC cells grown in this hydrogel exhibited biochemical and physiological features, including (1) enhanced cell proliferation, migration and invasion, colony formation, and chemoresistance; (2) suppressed apoptosis with altered expression levels of apoptosis-regulating molecules; (3) upregulated expression of crucial multidrug resistance-related genes; (4) accentuated expression of key molecules associated with malignant progression, such as epithelial–mesenchymal transition transcription factors, Notch, and pluripotency biomarkers; and (5) robust enrichment of ovarian CSCs. The findings indicate the potential of our 3D in vitro OC model as an in vitro research platform to study OC and ovarian CSC biology and to screen novel therapies targeting OC and ovarian CSCs.

Recent Progress of Nanocarrier-Based Therapy for Solid Malignancies

Conventional chemotherapy is still an important option of cancer treatment, but it has poor cell selectivity, severe side effects, and drug resistance. Utilizing nanoparticles (NPs) to improve the therapeutic effect of chemotherapeutic drugs has been highlighted in recent years. Nanotechnology dramatically changed the face of oncology by high loading capacity, less toxicity, targeted delivery of drugs, increased uptake to target sites, and optimized pharmacokinetic patterns of traditional drugs. At present, research is being envisaged in the field of novel nano-pharmaceutical design, such as liposome, polymer NPs, bio-NPs, and inorganic NPs, so as to make chemotherapy effective and long-lasting. Till now, a number of studies have been conducted using a wide range of nanocarriers for the treatment of solid tumors including lung, breast, pancreas, brain, and liver. To provide a reference for the further application of chemodrug-loaded nanoformulations, this review gives an overview of the recent development of nanocarriers, and the updated status of their use in the treatment of several solid tumors.

CD44+ cells determine fenofibrate-induced microevolution of drug-resistance in prostate cancer cell populations

Combinations of metabolic blockers (incl. fenofibrate) with chemotherapeutic drugs interfere with the drug-resistance of prostate cancer cells. However, their effect on cancer stem cells-dependent microevolution of prostate cancer malignancy remains unaddressed. Here, we hypothesize that the combined docetaxel/fenofibrate treatment prompts the selective expansion of cancer stem cells that affects the microevolution of their progenies. Accordingly, we adapted a combined in vitro/in vivo approach to identify biological and therapeutic consequences of this process. Minute subpopulations of docetaxel-resistant CD133high and/or CD44high cancer stem cell-like (SCL) cells were found in prostate cancer DU145 and PC3 cell populations. When pretreated with docetaxel, they readily differentiated into docetaxel-resistant CD44negative "bulk" cells, thus accounting for the microevolution of drug-resistant cell lineages. Combined docetaxel/fenofibrate treatment induced the generation of poly(morpho)nuclear giant cells and drug-resistant CD44high SCL cells. However, the CD44negative offspring of docetaxel- and docetaxel/fenofibrate-treated SCLs remained relatively sensitive to the combined treatment, while retaining enhanced resistance to docetaxel. Long-term propagation of drug-resistant SCL-derived lineages in the absence of docetaxel/fenofibrate resulted in their reverse microevolution toward the drug-sensitivity and invasive phenotype. Consequently, prostate tumors were able to recover from the combined docetaxel/fenofibrate stress after the initial arrest of their expansion in vivo. In conclusion, we have confirmed the potential of fenofibrate for the metronomic treatment of drug-resistant prostate tumors. However, docetaxel/fenofibrate-induced selective expansion of hyper-resistant CD44high SCL prostate cells and their "bulk" progenies prompts the microevolution of prostate tumor drug-resistance. This process can limit the implementation of metabolic chemotherapy in prostate cancer treatment.

Association of three factors (ABCB1 gene expression, steroid response, early response at day + 8) on the response to induction in patients with acute lymphoblastic leukemia

Treatment of acute lymphoblastic leukemia (ALL) requires the combination of multiple drugs to integrate a complete remission. The different prognostic factors (age, leukocytes, risk, cytogenetic alterations) allow identifying those patients with a high risk of relapse, but there are few described factors that impact the induction response. The objective was to identify the utility of different risk factors (overexpression of the ABCB1 drug resistance gene, favorable response to steroids (FRS) and early response at day + 8 of treatment) on the percentage of complete remissions and overall survival. This is a prospective, observational study in adult patients with B-ALL without specific cytogenetic alterations, who started induction treatment based on a pretreatment with prednisone and subsequently vincristine (1.6 mg/m² subcutaneous) plus daunorubicin (45 mg/m² subcutaneously) on days + 1, + 8, + 15. The ABCB1 resistance gene was evaluated at diagnosis, the FRS at the end of the pretreatment and the early response during day + 8. A total of 53 adult patients diagnosed with ALL Philadelphia negative chromosome (Ph^-), with immunophenotype B, with a normal karyotype, were studied. Cases with genetic abnormalities with a poor prognosis were excluded in order to reduce bias. The mean age was 48 years (range 17-68 years). 62.3% of patients were at high risk of relapse. When analyzing the risk factors, 30.2% showed high levels of the ABCB1 resistance gene, without showing an impact on the induction response (OR: 1.218, p = 0.743), but its overexpression was associated with a poor response to steroids as in the absence of early response. Individually, both the FRS (OR: 5.7, p = 0.004) and the absence of early response to day + 8 (OR: 6.42, p = 0.002) showed significance. By combining the different factors, having more than 2 was directly related to a failure (OR: 9.514, p = 0.000). The identification of factors such as FRS such as the persistence of blasts at the end of the first week of treatment is useful to identify patients at risk of failure in induction.

Significance of hematopoietic surface antigen CD34 in neuroblastoma prognosis and the genetic landscape of CD34-expressing neuroblastoma CSCs

High-risk neuroblastoma (HR-NB) is branded with hematogenous metastasis, relapses, and dismal long-term survival. Intensification of consolidation therapy with tandem/triple autologous stem cell (SC) rescue (with bone marrow [BM]/peripheral blood [PB] CD34⁺ selection) after myeloablative chemotherapy has improved long-term survival. However, the benefit is limited by the indication of NB cells in CD34⁺ PBSCs, CD34 expression in NB cells, and the risk of reinfusing NB cancer stem cells (NB CSCs) that could lead to post-transplant relapse. We investigated the association of CD34 surface expression (92 patients) with NB evolution/clinical outcomes. CD34 gene-level status in NB was assessed through RNA-Seq data mining (18 cohorts, n, 3324). Genetic landscape of CD34-expressing NB CSCs (CD133⁺CD34⁺) was compared with CD34^- CSCs (CD133⁺CD34^-). RNA-seq data revealed equivocal association patterns of CD34 expression with patient survival. Our immunohistochemistry data revealed definite, but rare (mean, 0.73%; range 0.00-7.87%; median, 0.20%) CD34 positivity in NB. CD34⁺ significantly associated with MYCN amplification (p, 0.003), advanced disease stage (p, 0.016), and progressive disease (PD, p < 0.0009) after clinical therapy. A general high-is-worse tendency was observed in patients with relapsed disease. High CD34⁺ correlated with poor survival in patients with N-MYC-amplified HR-NB. Gene expression analysis of CD34⁺-NB CSCs identified significant up (4631) and downmodulation (4678) of genes compared with NB CSCs that lack CD34. IPA recognized the modulation of crucial signaling elements (EMT, stemness maintenance, differentiation, inflammation, clonal expansion, drug resistance, metastasis) that orchestrate NB disease evolution in CD34⁺ CSCs compared with CD34^- CSCs. While the function of CD34 in NB evolution requires further in-depth investigation, careful consideration should be exercised for autologous stem cell rescue with CD34⁺ selection in NB patients. Graphical abstract.

Targeting the Id1-Kif11 Axis in Triple-Negative Breast Cancer Using Combination Therapy

The basic helix-loop-helix (bHLH) transcription factors inhibitor of differentiation 1 (Id1) and inhibitor of differentiation 3 (Id3) (referred to as Id) have an important role in maintaining the cancer stem cell (CSC) phenotype in the triple-negative breast cancer (TNBC) subtype. In this study, we aimed to understand the molecular mechanism underlying Id control of CSC phenotype and exploit it for therapeutic purposes. We used two different TNBC tumor models marked by either Id depletion or Id1 expression in order to identify Id targets using a combinatorial analysis of RNA sequencing and microarray data. Phenotypically, Id protein depletion leads to cell cycle arrest in the G0/G1 phase, which we demonstrate is reversible. In order to understand the molecular underpinning of Id proteins on the cell cycle phenotype, we carried out a large-scale small interfering RNA (siRNA) screen of 61 putative targets identified by using genomic analysis of two Id TNBC tumor models. Kinesin Family Member 11 (Kif11) and Aurora Kinase A (Aurka), which are critical cell cycle regulators, were further validated as Id targets. Interestingly, unlike in Id depletion conditions, Kif11 and Aurka knockdown leads to a G2/M arrest, suggesting a novel Id cell cycle mechanism, which we will explore in further studies. Therapeutic targeting of Kif11 to block the Id1–Kif11 axis was carried out using small molecular inhibitor ispinesib. We finally leveraged our findings to target the Id/Kif11 pathway using the small molecule inhibitor ispinesib in the Id+ CSC results combined with chemotherapy for better response in TNBC subtypes. This work opens up exciting new possibilities of targeting Id targets such as Kif11 in the TNBC subtype, which is currently refractory to chemotherapy. Targeting the Id1–Kif11 molecular pathway in the Id1+ CSCs in combination with chemotherapy and small molecular inhibitor results in more effective debulking of TNBC.

Ferroptosis: An emerging approach for targeting cancer stem cells and drug resistance

Resistance to chemotherapeutic agents remains a major challenge in the fierce battle against cancer. Cancer stem cells (CSCs) are a small population of cells in tumors that possesses the ability to self-renew, initiate tumors, and cause resistance to conventional anticancer agents. Targeting this population of cells was proven as a promising approach to eliminate cancer recurrence and improve the clinical outcome. CSCs are less susceptible to death by classical anticancer agents inducing apoptosis. CSCs can be eradicated by ferroptosis, which is a non-apoptotic-regulated mechanism of cell death. The induction of ferroptosis is an attractive strategy to eliminate tumors due to its ability to selectively target aggressive CSCs. The current review critically explored the crosstalk and regulatory pathways controlling ferroptosis, which can selectively induce CSCs death. In addition, successful chemotherapeutic agents that achieve better therapeutic outcomes through the induction of ferroptosis in CSCs were discussed to highlight their promising clinical impact.

Counteracting Chemoresistance with Metformin in Breast Cancers: Targeting Cancer Stem Cells

Despite the leaps and bounds in achieving success in the management and treatment of breast cancers through surgery, chemotherapy, and radiotherapy, breast cancer remains the most frequently occurring cancer in women and the most common cause of cancer-related deaths among women. Systemic therapeutic approaches, such as chemotherapy, although beneficial in treating and curing breast cancer subjects with localized breast tumors, tend to fail in metastatic cases of the disease due to (a) an acquired resistance to the chemotherapeutic drug and (b) the development of intrinsic resistance to therapy. The existence of cancer stem cells (CSCs) plays a crucial role in both acquired and intrinsic chemoresistance. CSCs are less abundant than terminally differentiated cancer cells and confer chemoresistance through a unique altered metabolism and capability to evade the immune response system. Furthermore, CSCs possess active DNA repair systems, transporters that support multidrug resistance (MDR), advanced detoxification processes, and the ability to self-renew and differentiate into tumor progenitor cells, thereby supporting cancer invasion, metastasis, and recurrence/relapse. Hence, current research is focusing on targeting CSCs to overcome resistance and improve the efficacy of the treatment and management of breast cancer. Studies revealed that metformin (1, 1-dimethylbiguanide), a widely used anti-hyperglycemic agent, sensitizes tumor response to various chemotherapeutic drugs. Metformin selectively targets CSCs and improves the hypoxic microenvironment, suppresses the tumor metastasis and inflammation, as well as regulates the metabolic programming, induces apoptosis, and reverses epithelial-mesenchymal transition and MDR. Here, we discuss cancer (breast cancer) and chemoresistance, the molecular mechanisms of chemoresistance in breast cancers, and metformin as a chemo-sensitizing/re-sensitizing agent, with a particular focus on breast CSCs as a critical contributing factor to acquired and intrinsic chemoresistance. The review outlines the prospects and directions for a better understanding and re-purposing of metformin as an anti-cancer/chemo-sensitizing drug in the treatment of breast cancer. It intends to provide a rationale for the use of metformin as a combinatory therapy in a clinical setting.