Cancer stem cells--old concepts, new insights

Modulatory effects of cancer stem cell-derived extracellular vesicles on the tumor immune microenvironment

Cancer stem cells (CSCs), accounting for only a minor cell proportion (< 1%) within tumors, have profound implications in tumor initiation, metastasis, recurrence, and treatment resistance due to their inherent ability of self-renewal, multi-lineage differentiation, and tumor-initiating potential. In recent years, accumulating studies indicate that CSCs and tumor immune microenvironment act reciprocally in driving tumor progression and diminishing the efficacy of cancer therapies. Extracellular vesicles (EVs), pivotal mediators of intercellular communications, build indispensable biological connections between CSCs and immune cells. By transferring bioactive molecules, including proteins, nucleic acids, and lipids, EVs can exert mutual influence on both CSCs and immune cells. This interaction plays a significant role in reshaping the tumor immune microenvironment, creating conditions favorable for the sustenance and propagation of CSCs. Deciphering the intricate interplay between CSCs and immune cells would provide valuable insights into the mechanisms of CSCs being more susceptible to immune escape. This review will highlight the EV-mediated communications between CSCs and each immune cell lineage in the tumor microenvironment and explore potential therapeutic opportunities.

The therapeutic effect of traditional Chinese medicine on breast cancer through modulation of the Wnt/β-catenin signaling pathway

Breast cancer, the most prevalent malignant tumor among women globally, is significantly influenced by the Wnt/β-catenin signaling pathway, which plays a crucial role in its initiation and progression. While conventional chemotherapy, the standard clinical treatment, suffers from significant drawbacks like severe side effects, high toxicity, and limited prognostic efficacy, Traditional Chinese Medicine (TCM) provides a promising alternative. TCM employs a multi-targeted therapeutic approach, which results in fewer side effects and offers a high potential for effective treatment. This paper presents a detailed analysis of the therapeutic impacts of TCM on various subtypes of breast cancer, focusing on its interaction with the Wnt/β-catenin signaling pathway. Additionally, it explores the effectiveness of both monomeric and compound forms of TCM in the management of breast cancer. We also discuss the potential of establishing biomarkers for breast cancer treatment based on key proteins within the Wnt/β-catenin signaling pathway. Our aim is to offer new insights into the prevention and treatment of breast cancer and to contribute to the standardization of TCM.

In silico identification and in vitro validation of alpha-hederin as a potent inhibitor of Wnt/β-catenin signaling pathway in breast cancer stem cells

Cancer stem cells (CSCs) play a vital role in metastasis, recurrence and chemoresistance in breast cancer. β-catenin, which is a frequently over activated protein in CSCs, binds to T-cell factor/lymphoid enhancer factor (Tcf/Lef) family transcription factors leading to ectopic expression of Wnt pathway responsive genes necessary for the maintenance and action of CSCs. With the aim of identifying a small molecules that can effectively eliminate CSCs, molecular docking studies were performed against the Tcf/Lef binding hotspot on β-catenin using a library of 100 natural or synthetic small molecules. Small molecule ligands giving docking energy better than - 7 kcal/mol were further investigated by binding interactions analysis and molecular dynamics (MD) simulations. These compounds were then investigated in vitro, for cytotoxicity against CSCs isolated from MDA-MB-231 triple negative breast cancer cells. Alpha-hederin (AH) was identified as the only compound in the selected library that has cytotoxicity against breast CSCs. AH was further investigated for it's ability to regulate Wnt pathway target genes (Cyclin D1 and CD44)and the tumor suppressor p53by real-time quantitative PCR. Absorption, distribution, metabolism, excretion and toxicity properties of the AH was predicted in silico. AH significantly down regulated the transcription of Cyclin D1 and CD44 while up-regulating the transcription of p53. AH was predicted to have acceptable drug likeness. Although AH is currently known to inhibit the growth of various cancer cells in vitro, present study demonstrated for the first time that it is a potent inhibitor of Wnt/β-catenin signaling pathway and induce apoptosis in breast CSCs.

Spontaneous Fusion with Transformed Mesenchymal Stromal Cells Results in Complete Heterogeneity in Prostate Cancer Cells

Tumor cells gain advantages in growth and survival by acquiring genotypic and phenotypic heterogeneity. Interactions with bystander cells in the tumor microenvironment contribute to the progression of heterogeneity. We have shown that fusion between tumor and bystander cells is one form of interaction, and that tumor-bystander cell fusion has contrasting effects. By trapping fusion hybrids in the heterokaryon or synkaryon state, tumor-bystander cell fusion prevents the progression of heterogeneity. However, if trapping fails, fusion hybrids will resume replication to form derivative clones with diverse genomic makeups and behavioral phenotypes. To determine the characteristics of bystander cells that influence the fate of fusion hybrids, we co-cultured prostate mesenchymal stromal cell lines and their spontaneously transformed sublines with LNCaP as well as HPE-15 prostate cancer cells. Subclones derived from cancer-stromal fusion hybrids were examined for genotypic and phenotypic diversifications. Both stromal cell lines were capable of fusing with cancer cells, but only fusion hybrids with the transformed stromal subline generated large numbers of derivative subclones. Each subclone had distinct cell morphologies and growth behaviors and was detected with complete genomic hybridization. The health conditions of the bystander cell compartment play a crucial role in the progression of tumor cell heterogeneity.

Paneth-like cells produced from OLFM4+ stem cells support OLFM4+ stem cell growth in advanced colorectal cancer

Tumor tissues consist of heterogeneous cells that originate from stem cells; however, their cell fate determination program remains incompletely understood. Using patient-derived organoids established from patients with advanced colorectal cancer (CRC), we evaluated the potential of olfactomedin 4 (OLFM4)+ stem cells to produce a bifurcated lineage of progenies with absorptive and secretory properties. In the early phases of organoid reconstruction, OLFM4+ cells preferentially gave rise to secretory cells. Additionally, we found that Paneth-like cells, which do not exist in the normal colon, were induced in response to Notch signaling inhibition. Video recordings of single OLFM4+ cells revealed that organoids containing Paneth-like cells were effectively propagated and that their selective ablation led to organoid collapse. In tumor tissues, Paneth-like cells were identified only in the region where tumor cells lost cell adhesion. These findings indicate that Paneth-like cells are directly produced by OLFM4+ stem cells and that their interaction contributes to tumor formation by providing niche factors. This study reveals the importance of the cell fate specification program for building a complete tumor cellular ecosystem, which might be targeted with novel therapeutics.

Therapeutic Approaches of Dual-targeted Nanomedicines for Tumor Multidrug Resistance

Currently, the main cause of cancer chemotherapy failure is multi-drug resistance (MDR), which involves a variety of complex mechanisms. Compared with traditional small-molecule chemotherapy, targeted nanomedicines offer promising alternative strategies as an emerging form of therapy, especially active targeted nanomedicines. However, although single-targeted nanomedicines have made some progress in tumor therapy, the complexity of tumor microenvironment and tumor heterogeneity limits their efficacy. Dual-targeted nanomedicines can simultaneously target two tumor-specific factors that cause tumor MDR, which have the potential in overcoming tumor MDR superior to single-targeted nanomedicines by further enhancing cell uptake and cytotoxicity in new forms, as well as the effectiveness of tumor-targeted delivery. This review discusses tumor MDR mechanisms and the latest achievements applied to dual-targeted nanomedicines in tumor MDR.

Purinergic Signaling and its Role in the Stem Cell Differentiation

Purinergic signaling is a mechanism in which extracellular purines and pyrimidines interact with specialized cell surface receptors known as purinergic receptors. These receptors are divided into two families of P1 and P2 receptors, each responding to different nucleosides and nucleotides. P1 receptors are activated by adenosine, while P2 receptors are activated by pyrimidine and purines. P2X receptors are ligand-gated ion channels, including seven subunits (P2X1-7). However, P2Y receptors are the G-protein coupled receptors comprising eight subtypes (P2Y1/2/4/6/11/12/13/14). The disorder in purinergic signaling leads to various health-related issues and diseases. In various aspects, it influences the activity of non-neuronal cells and neurons. The molecular mechanism of purinergic signaling provides insight into treating various human diseases. On the contrary, stem cells have been investigated for therapeutic applications. Purinergic signaling has shown promising effect in stem cell engraftment. The immune system promotes the autocrine and paracrine mechanisms and releases the significant factors essential for successful stem cell therapy. Each subtype of purinergic receptor exerts a beneficial effect on the damaged tissue. The most common effect caused by purinergic signaling is the proliferation and differentiation that treat different health-related conditions.

Targeting cancer stem cell plasticity in triple-negative breast cancer

Triple-negative breast cancer (TNBC) is a highly aggressive breast cancer subtype with limited treatment options. Cancer stem cells (CSCs) are thought to play a crucial role in TNBC progression and resistance to therapy. CSCs are a small subpopulation of cells within tumors that possess self-renewal and differentiation capabilities and are responsible for tumor initiation, maintenance, and metastasis. CSCs exhibit plasticity, allowing them to switch between states and adapt to changing microenvironments. Targeting CSC plasticity has emerged as a promising strategy for TNBC treatment. This review summarizes recent advances in understanding the molecular mechanisms underlying CSC plasticity in TNBC and discusses potential therapeutic approaches targeting CSC plasticity.

Purinergic system in cancer stem cells

Accumulating evidence supports the idea that cancer stem cells (CSCs) are those with the capacity to initiate tumors, generate phenotypical diversity, sustain growth, confer drug resistance, and orchestrate the spread of tumor cells. It is still controversial whether CSCs originate from normal stem cells residing in the tissue or cancer cells from the tumor bulk that have dedifferentiated to acquire stem-like characteristics. Although CSCs have been pointed out as key drivers in cancer, knowledge regarding their physiology is still blurry; thus, research focusing on CSCs is essential to designing novel and more effective therapeutics. The purinergic system has emerged as an important autocrine-paracrine messenger system with a prominent role at multiple levels of the tumor microenvironment, where it regulates cellular aspects of the tumors themselves and the stromal and immune systems. Recent findings have shown that purinergic signaling also participates in regulating the CSC phenotype. Here, we discuss updated information regarding CSCs in the purinergic system and present evidence supporting the idea that elements of the purinergic system expressed by this subpopulation of the tumor represent attractive pharmacological targets for proposing innovative anti-cancer therapies.

Recent progress in high-throughput droplet screening and sorting for bioanalysis

Owing to its ability to isolate single cells and perform high-throughput sorting, droplet sorting has been widely applied in several research fields. Compared with flow cytometry, droplet allows the encapsulation of single cells for cell secretion or lysate analysis. With the rapid development of this technology in the past decade, various droplet sorting devices with high throughput and accuracy have been developed. A droplet sorter with the highest sorting throughput of 30,000 droplets per second was developed in 2015. Since then, increased attention has been paid to expanding the possibilities of droplet sorting technology and strengthening its advantages over flow cytometry. This review aimed to summarize the recent progress in droplet sorting technology from the perspectives of device design, detection signal, actuating force, and applications. Technical details for improving droplet sorting through various approaches are introduced and discussed. Finally, we discuss the current limitations of droplet sorting for single-cell studies along with the existing gap between the laboratory and industry and provide our insights for future development of droplet sorters.

Chondrosarcoma Resistance to Radiation Therapy: Origins and Potential Therapeutic Solutions

Chondrosarcoma is a malignant cartilaginous tumor that is particularly chemoresistant and radioresistant to X-rays. The first line of treatment is surgery, though this is almost impossible in some specific locations. Such resistances can be explained by the particular composition of the tumor, which develops within a dense cartilaginous matrix, producing a resistant area where the oxygen tension is very low. This microenvironment forces the cells to adapt and dedifferentiate into cancer stem cells, which are described to be more resistant to conventional treatments. One of the main avenues considered to treat this type of tumor is hadrontherapy, in particular for its ballistic properties but also its greater biological effectiveness against tumor cells. In this review, we describe the different forms of chondrosarcoma resistance and how hadrontherapy, combined with other treatments involving targeted inhibitors, could help to better treat high-grade chondrosarcoma.

Purinergic signaling: Diverse effects and therapeutic potential in cancer

Regardless of improved biological insights and therapeutic advances, cancer is consuming multiple lives worldwide. Cancer is a complex disease with diverse cellular, metabolic, and physiological parameters as its hallmarks. This instigates a need to uncover the latest therapeutic targets to advance the treatment of cancer patients. Purines are building blocks of nucleic acids but also function as metabolic intermediates and messengers, as part of a signaling pathway known as purinergic signaling. Purinergic signaling comprises primarily adenosine triphosphate (ATP) and adenosine (ADO), their analogous membrane receptors, and a set of ectonucleotidases, and has both short- and long-term (trophic) effects. Cells release ATP and ADO to modulate cellular function in an autocrine or paracrine manner by activating membrane-localized purinergic receptors (purinoceptors, P1 and P2). P1 receptors are selective for ADO and have four recognized subtypes-A1, A2A, A2B, and A3. Purines and pyrimidines activate P2 receptors, and the P2X subtype is ligand-gated ion channel receptors. P2X has seven subtypes (P2X1-7) and forms homo- and heterotrimers. The P2Y subtype is a G protein-coupled receptor with eight subtypes (P2Y1/2/4/6/11/12/13/14). ATP, its derivatives, and purinoceptors are widely distributed in all cell types for cellular communication, and any imbalance compromises the homeostasis of the cell. Neurotransmission, neuromodulation, and secretion employ fast purinergic signaling, while trophic purinergic signaling regulates cell metabolism, proliferation, differentiation, survival, migration, invasion, and immune response during tumor progression. Thus, purinergic signaling is a prospective therapeutic target in cancer and therapy resistance.

Signaling pathways in the regulation of cancer stem cells and associated targeted therapy

Cancer stem cells (CSCs) are defined as a subpopulation of malignant tumor cells with selective capacities for tumor initiation, self-renewal, metastasis, and unlimited growth into bulks, which are believed as a major cause of progressive tumor phenotypes, including recurrence, metastasis, and treatment failure. A number of signaling pathways are involved in the maintenance of stem cell properties and survival of CSCs, including well-established intrinsic pathways, such as the Notch, Wnt, and Hedgehog signaling, and extrinsic pathways, such as the vascular microenvironment and tumor-associated immune cells. There is also intricate crosstalk between these signal cascades and other oncogenic pathways. Thus, targeting pathway molecules that regulate CSCs provides a new option for the treatment of therapy-resistant or -refractory tumors. These treatments include small molecule inhibitors, monoclonal antibodies that target key signaling in CSCs, as well as CSC-directed immunotherapies that harness the immune systems to target CSCs. This review aims to provide an overview of the regulating networks and their immune interactions involved in CSC development. We also address the update on the development of CSC-directed therapeutics, with a special focus on those with application approval or under clinical evaluation.

Inactivation of LATS1/2 drives luminal-basal plasticity to initiate basal-like mammary carcinomas

Basal-like breast cancers, an aggressive breast cancer subtype that has poor treatment options, are thought to arise from luminal mammary epithelial cells that undergo basal plasticity through poorly understood mechanisms. Using genetic mouse models and ex vivo primary organoid cultures, we show that conditional co-deletion of the LATS1 and LATS2 kinases, key effectors of Hippo pathway signaling, in mature mammary luminal epithelial cells promotes the development of Krt14 and Sox9-expressing basal-like carcinomas that metastasize over time. Genetic co-deletion experiments revealed that phenotypes resulting from the loss of LATS1/2 activity are dependent on the transcriptional regulators YAP/TAZ. Gene expression analyses of LATS1/2-deleted mammary epithelial cells notably revealed a transcriptional program that associates with human basal-like breast cancers. Our study demonstrates in vivo roles for the LATS1/2 kinases in mammary epithelial homeostasis and luminal-basal fate control and implicates signaling networks induced upon the loss of LATS1/2 activity in the development of basal-like breast cancer.

Cancer Metastasis and Treatment Resistance: Mechanistic Insights and Therapeutic Targeting of Cancer Stem Cells and the Tumor Microenvironment

Cancer metastasis and treatment resistance are the main causes of treatment failure and cancer-related deaths. Their underlying mechanisms remain to be fully elucidated and have been attributed to the presence of cancer stem cells (CSCs)-a small population of highly tumorigenic cancer cells with pluripotency and self-renewal properties, at the apex of a cellular hierarchy. CSCs drive metastasis and treatment resistance and are sustained by a dynamic tumor microenvironment (TME). Numerous pathways mediate communication between CSCs and/or the surrounding TME. These include a paracrine renin-angiotensin system and its convergent signaling pathways, the immune system, and other signaling pathways including the Notch, Wnt/β-catenin, and Sonic Hedgehog pathways. Appreciation of the mechanisms underlying metastasis and treatment resistance, and the pathways that regulate CSCs and the TME, is essential for developing a durable treatment for cancer. Pre-clinical and clinical studies exploring single-point modulation of the pathways regulating CSCs and the surrounding TME, have yielded partial and sometimes negative results. This may be explained by the presence of uninhibited alternative signaling pathways. An effective treatment of cancer may require a multi-target strategy with multi-step inhibition of signaling pathways that regulate CSCs and the TME, in lieu of the long-standing pursuit of a 'silver-bullet' single-target approach.

Chemotherapy induces feedback up-regulation of CD44v6 in colorectal cancer initiating cells through β-catenin/MDR1 signaling to sustain chemoresistance

Chemoresistance in colorectal cancer initiating cells (CICs) involves the sustained activation of multiple drug resistance (MDR) and WNT/β-catenin signaling pathways, as well as of alternatively spliced-isoforms of CD44 containing variable exon-6 (CD44v6). In spite of its importance, mechanisms underlying the sustained activity of WNT/β-catenin signaling have remained elusive. The presence of binding elements of the β-catenin-interacting transcription factor TCF4 in the MDR1 and CD44 promoters suggests that crosstalk between WNT/β-catenin/TCF4-activation and the expression of the CD44v6 isoform mediated by FOLFOX, a first-line chemotherapeutic agent for colorectal cancer, could be a fundamental mechanism of FOLFOX resistance. Our results identify that FOLFOX treatment induced WNT3A secretion, which stimulated a positive feedback loop coupling β-catenin signaling and CD44v6 splicing. In conjunction with FOLFOX induced WNT3A signal, specific CD44v6 variants produced by alternative splicing subsequently enhance the late wave of WNT/β-catenin activation to facilitate cell cycle progression. Moreover, we revealed that FOLFOX-mediated sustained WNT signal requires the formation of a CD44v6-LRP6-signalosome in caveolin microdomains, which leads to increased FOLFOX efflux. FOLFOX-resistance in colorectal CICs occurs in the absence of tumor-suppressor disabled-2 (DAB2), an inhibitor of WNT/β-catenin signaling. Conversely, in sensitive cells, DAB2 inhibition of WNT-signaling requires interaction with a clathrin containing CD44v6-LRP6-signalosome. Furthermore, full-length CD44v6, once internalized through the caveolin-signalosome, is translocated to the nucleus where in complex with TCF4, it binds to β-catenin/TCF4-regulated MDR1, or to CD44 promoters, which leads to FOLFOX-resistance and CD44v6 transcription through transcriptional-reprogramming. These findings provide evidence that targeting CD44v6-mediated LRP6/β-catenin-signaling and drug efflux may represent a novel approach to overcome FOLFOX resistance and inhibit tumor progression in colorectal CICs. Thus, sustained drug resistance in colorectal CICs is mediated by overexpression of CD44v6, which is both a functional biomarker and a therapeutic target in colorectal cancer.

Interplay Between Chemotherapy-Activated Cancer Associated Fibroblasts and Cancer Initiating Cells Expressing CD44v6 Promotes Colon Cancer Resistance

Cancer-initiating cells (CICs) drive colorectal tumor growth by their supportive niches where CICs interact with multiple cell types within the microenvironment, including cancer-associated fibroblasts (CAFs). We investigated the interplay between the CICs and the clinically relevant chemotherapeutic FOLFOX that creates the persistent tumorigenic properties of colorectal CICs, and stimulates the microenvironmental factors derived from the CAFs. We found that the CICs expressing an immunophenotype (CD44v6[+]) promote FOLFOX-resistance and that the CIC-immunophenotype was enhanced by factors secreted by CAFs after FOLFOX treatment These secreted factors included periostin, IL17A and WNT3A, which induced CD44v6 expression by activating WNT3A/β-catenin signaling. Blocking the interaction between CICs with any of these CAF-derived factors through tissue-specific conditional silencing of CD44v6 significantly reduced colorectal tumorigenic potential. To achieve this, we generated two unique vectors (floxed-pSico-CD44v6 shRNA plus Fabpl-Cre) that were encapsulated into transferrin coated PEG-PEI/(nanoparticles), which when introduced in vivo reduced tumor growth more effectively than using CD44v6-blocking antibodies. Notably, this tissue-specific conditional silencing of CD44v6 resulted in long lasting effects on self-renewal and tumor growth associated with a positive feedback loop linking WNT3A signaling and alternative-splicing of CD44. These findings have crucial clinical implications suggesting that therapeutic approaches for modulating tumor growth that currently focus on cell-autonomous mechanisms may be too limited and need to be broadened to include mechanisms that recognize the interplay between the stromal factors and the subsequent CIC-immunophenotype enrichment. Thus, more specific therapeutic approaches may be required to block a chemotherapy induced remodeling of a microenvironment that acts as a paracrine regulator to enrich CD44v6 (+) in colorectal CICs.

Impact of bevacizumab and secondary cytoreductive surgery on survival outcomes in platinum-sensitive relapsed ovarian clear cell carcinoma: A multicenter study in Korea

OBJECTIVE

This study investigated survival outcomes for platinum-sensitive relapsed ovarian clear cell carcinoma (OCCC) by treatment method.

METHODS

OCCC patients with platinum-sensitive recurrence that received secondary treatment at five institutions between July 2007 and June 2021 were included. Patient characteristics and survival outcomes were compared according to the use of bevacizumab (BEV) during second-line chemotherapy and secondary cytoreductive surgery (CRS).

RESULTS

138 patients were included. The BEV (n = 36) and non-BEV (n = 102) groups had similar initial FIGO stages and proportions of secondary CRS. The BEV group showed improved progression-free survival (PFS; median, 15.4 vs. 7.5 months; P = 0.042) and overall survival (OS; P = 0.043) compared to the non-BEV group. In multivariate analyses, BEV was identified as an independent prognostic factor for PFS (adjusted hazard ratio [aHR], 0.571; 95% confidence interval [CI], 0.354-0.921; P = 0.022) and OS (aHR, 0.435; 95%CI, 0.195-0.970; P = 0.042). The secondary CRS group (n = 42) had early-stage disease at diagnosis more frequently (P = 0.009) and multi-site metastasis (P < 0.001) at recurrence less frequently than the no surgery group (n = 96). The secondary CRS group showed significantly better PFS (median, 33.7 vs. 7.2 months; P < 0.001) and OS (P < 0.001). Secondary CRS was associated with a significantly improved PFS (aHR, 0.297; 95% CI, 0.183-0.481; P < 0.001) and OS (aHR, 0.276; 95% CI, 0.133-0.576; P = 0.001). The BEV and non-BEV groups showed similar PFS and OS among the patients who underwent secondary CRS. In contrast, the BEV group showed improved PFS and OS among patients who did not undergo surgery.

CONCLUSIONS

The use of BEV during second-line chemotherapy and secondary CRS may improve PFS and OS in patients with platinum-sensitive relapsed OCCC. Further prospective studies are warranted.

Identification of a neural development gene expression signature in colon cancer stem cells reveals a role for EGR2 in tumorigenesis

Recent evidence demonstrates that colon cancer stem cells (CSCs) can generate neurons that synapse with tumor innervating fibers required for tumorigenesis and disease progression. Greater understanding of the mechanisms that regulate CSC driven tumor neurogenesis may therefore lead to more effective treatments. RNA-sequencing analyses of ALDHPositive CSCs from colon cancer patient-derived organoids (PDOs) and xenografts (PDXs) showed CSCs to be enriched for neural development genes. Functional analyses of genes differentially expressed in CSCs from PDO and PDX models demonstrated the neural crest stem cell (NCSC) regulator EGR2 to be required for tumor growth and to control expression of homebox superfamily embryonic master transcriptional regulator HOX genes and the neural stem cell and master cell fate regulator SOX2. These data support CSCs as the source of tumor neurogenesis and suggest that targeting EGR2 may provide a therapeutic differentiation strategy to eliminate CSCs and block nervous system driven disease progression.

Immune- and Stemness-Related Genes Revealed by Comprehensive Analysis and Validation for Cancer Immunity and Prognosis and Its Nomogram in Lung Adenocarcinoma

Objective

Lung adenocarcinoma (LUAD) is a familiar lung cancer with a very poor prognosis. This study investigated the immune- and stemness-related genes to develop model related with cancer immunity and prognosis in LUAD.

Method

The Cancer Genome Atlas (TCGA) was utilized for obtaining original transcriptome data and clinical information. Differential expression, prognostic value, and correlation with clinic parameter of mRNA stemness index (mRNAsi) were conducted in LUAD. Significant mRNAsi-related module and hub genes were screened using weighted gene coexpression network analysis (WGCNA). Meanwhile, immune-related differential genes (IRGs) were screened in LUAD. Stem cell index and immune-related differential genes (SC-IRGs) were screened and further developed to construct prognosis-related model and nomogram. Comprehensive analysis of hub genes and subgroups, involving enrichment in the subgroup [gene set enrichment analysis (GSEA)], gene mutation, genetic correlation, gene expression, immune, tumor mutation burden (TMB), and drug sensitivity, used bioinformatics and reverse transcription polymerase chain reaction (RT-PCR) for verification.

Results

Through difference analysis, mRNAsi of LUAD group was markedly higher than that of normal group. Clinical parameters (age, gender, and T staging) were ascertained to be highly relevant to mRNAsi. MEturquoise and MEblue were found to be the most significant modules (including positive and negative correlations) related to mRNAsi via WGCNA. The functions and pathways of the two mRNAsi-related modules were mainly enriched in tumorigenesis, development, and metastasis. Combining stem cell index-related differential genes and immune-related differential genes, 30 prognosis-related SC-IRGs were screened via Cox regression analysis. Then, 16 prognosis-related SC-IRGs were screened to construct a LASSO regression model at last. In addition, the model was successfully validated by using TCGA-LUAD and GSE68465, whereas c-index and the calibration curves were utilized to demonstrate the clinical value of our nomogram. Following the validation of the model, GSEA, immune cell correlation, TMB, clinical relevance, etc., have found significant difference in high- and low-risk groups, and 16-gene expression of the SC-IRG model also was tested by RT-PCR. ADRB2, ANGPTL4, BDNF, CBLC, CX3CR1, and IL3RA were found markedly different expression between the tumor and normal group.

Conclusion

The SC-IRG model and the prognostic nomogram could accurately predict LUAD survival. Our study used mRNAsi combined with immunity that may lay a foundation for the future research studies in LUAD.

HMGA2-Snai2 axis regulates tumorigenicity and stemness of head and neck squamous cell carcinoma

Cancer stem cells (CSCs) are a tumorigenic cell subpopulation, which contributes to treatment resistance, tumor recurrence, and metastasis. This study aimed to investigate the role and underlying molecular targets of high mobility group AT-hook 2 (HMGA2) in the progression and CSCs regulation of head and neck squamous cell carcinoma (HNSCC). HMGA2 mRNA and protein expression levels were examined in HNSCC specimens and cells by qRT-PCR, Western blot, and immunohistochemistry. The roles of HMGA2 were validated via loss-of-function and exogenous overexpression experiments in vitro and in vivo, and CSCs properties were assessed by tumorsphere formation assay. Chromatin immunoprecipitation (ChIP) and luciferase reporter assays provided further insight into the molecular mechanisms by which HMGA2 regulates stemness. HMGA2 was abnormally overexpressed in HNSCC, and it promoted the expression of the CSCs markers including SOX2, CD133, CD44, ALDH1A1, and Bmi1. HMGA2 was correlated with stemness, malignant progression, and reduced survival in HNSCC. Luciferase reporter assay indicated that Snai2 was a direct downstream target gene of HMGA2. Mechanistically, ChIP-qPCR assay showed that HMGA2 was recruited to three binding sites on the Snai2 promoter, directly facilitating the transcription of Snai2 in HNSCC. Snai2 overexpression reversed the inhibitory effect of HMGA2 interference on the proliferation, invasion, and metastasis of HNSCC and CSC marker expression in vitro and in vivo. HMGA2 promoted the malignant progression of HNSCC and acquired CSCs properties through direct regulation of Snai2, thereby suggesting that targeting the HMGA2-Snai2 axis might be a promising therapeutic strategy for HNSCC.

The Role of Tumor Stem Cell Exosomes in Cancer Invasion and Metastasis

Exosomes are lipid membrane bilayer-encapsulated vesicles secreted by cells into the extracellular space. They carry abundant inclusions (such as nucleic acids, proteins, and lipids) that play pivotal roles in intercellular communication. Tumor stem cells are capable of self-renewal and are crucial for survival, proliferation, drug resistance, metastasis, and recurrence of tumors. The miRNAs (microRNAs) in exosomes have various functions, such as participating in inflammatory response, cell migration, proliferation, apoptosis, autophagy, and epithelial-mesenchymal transition. Tumor stem cells secrete exosomes that act as important messengers involved in various tumor processes and several studies provide increasing evidence supporting the importance of these exosomes in tumor recurrence and metastasis. This review primarily focuses on the production and secretion of exosomes from tumors and tumor stem cells and their effects on cancer progression. Cancer stem cancer derived exosome play an important massager in the tumor microenvironment. It also emphasizes on the study of tumor stem cell exosomes in the light of cancer metastasis and recurrence aiming to provide valuable insights and novel perspectives, which could be beneficial for developing effective diagnostic and treatment strategies.

Histone Acetylation Regulator-Mediated Acetylation Patterns Define Tumor Malignant Pathways and Tumor Microenvironment in Hepatocellular Carcinoma

Background

Histone acetylation modification is one of the most common epigenetic methods used to regulate chromatin structure, DNA repair, and gene expression. Existing research has focused on the importance of histone acetylation in regulating tumorigenicity, tumor progression, and tumor microenvironment (TME) but has not explored the potential roles and interactions of histone acetylation regulators in TME cell infiltration, drug sensitivity, and immunotherapy.

Methods

The mRNA expression and genetic alterations of 36 histone acetylation regulators were analyzed in 1599 hepatocellular carcinoma (HCC) samples. The unsupervised clustering method was used to identify the histone acetylation patterns. Then, based on their differentially expressed genes (DEGs), an HAscore model was constructed to quantify the histone acetylation patterns and related subtypes of individual samples. Lastly, the relationship between HAscore and transcription background, tumor clinical features, characteristics of TME, drug response, and efficacy of immunotherapy were analyzed.

Results

We identified three histone acetylation patterns characterized by high, medium, and low HAscore. Patients with HCC in the high HAscore group experienced worse overall survival time, and the cancer-related malignant pathways were more active in the high HAscore group, comparing to the low HAscore group. The high HAscore group was characterized by an immunosuppressive subtype because of the high infiltration of immunosuppressive cells, such as regulatory T cells and myeloid-derived suppressor cells. Following validation, the HAscore was highly correlated with the sensitivity of anti-tumor drugs; 116 therapeutic agents were found to be associated with it. The HAscore was also correlated with the therapeutic efficacy of the PD-L1 and PD-1 blockade, and the response ratio was significantly higher in the low HAscore group.

Conclusion

To the best of our knowledge, our study is the first to provide a comprehensive analysis of 36 histone acetylation regulators in HCC. We found close correlations between histone acetylation patterns and tumor malignant pathways and TME. We also analyzed the therapeutic value of the HAscore in targeted therapy and immunotherapy. This work highlights the interactions and potential clinical utility of histone acetylation regulators in treatment of HCC and improving patient outcomes.

Classification of lung adenocarcinoma based on stemness scores in bulk and single cell transcriptomes

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This study explores tumor stemness based on both bulk tumor and single cell transcriptome datasets.

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High-stemness tumors are less responsive to immunotherapy and targeted therapy compared with low-stemness tumors.

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Many high-stemness cells are at the beginning of the cell evolution trajectory, while most low-stemness cells are in the terminal or later phase.

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The correlations of tumor stemness with intratumor heterogeneity and tumor immunity were in the opposite direction between bulk tumors and single cells.

Tumor stemness is associated with tumor progression and therapy resistance. The recent advances in sequencing, genomics, and computational technologies have facilitated investigation into the tumor stemness cell-like characteristics. We identified subtypes of lung adenocarcinoma (LUAD) in bulk tumors or single cells based on the enrichment scores of 12 stemness signatures by clustering analysis of their transcriptomic profiles. Three stemness subtypes of LUAD were identified: St-H, St-M, and St-L, having high, medium, and low stemness signatures, respectively, consistently in six different datasets. Among the three subtypes, St-H was the most enriched in epithelial-mesenchymal transition, invasion, and metastasis signaling, genomically instable, irresponsive to immunotherapies and targeted therapies, and hence had the worst prognosis. We observed that intratumor heterogeneity was significantly higher in high-stemness than in low-stemness bulk tumors, but significantly lower in high-stemness than in low-stemness single cancer cells. Moreover, tumor immunity was stronger in high-stemness than in low-stemness cancer cells, but weaker in high-stemness than in low-stemness bulk tumors. These differences between bulk tumors and single cancer cells could be attributed to the non-tumor cells in bulk tumors that confounded the results of correlation analysis. Furthermore, pseudotime analysis showed that many St-H cells were at the beginning of the cell evolution trajectory, compared to most St-L cells in the terminal or later phase, suggesting that many low-stemness cells are originated from high-stemness cells. The stemness-based classification of LUAD may provide novel insights into the tumor biology as well as precise clinical management of this disease.

Single-cell RNA sequencing and bioinformatics as tools to decipher cancer heterogenicity and mechanisms of drug resistance

It is well known that cancer is an aggressive disease, often associated with relapse, in many cases due to drug resistance. Cancer stem cell and clonal evolution are frequently causes of innate or acquired drug resistance. Current RNA sequencing technologies do not distinguish gene expression of different cell lineages because they are based on bulk cell studies. Single-cell RNA sequencing technologies and related bioinformatics clustering and differential expression analysis represent a turning point in cancer research. They are emerging as essential tools for dissecting tumors at single-cell resolution and represent novel tools to understand carcinogenesis and drug response. In this review, we will outline the role of these new technologies in addressing cancer heterogeneity and cell lineage-dependent drug resistance.

Cancer Cell Fusion and Post-Hybrid Selection Process (PHSP)

Fusion of cancer cells either with other cancer cells (homotypic fusion) in local vicinity of the tumor tissue or with other cell types (e.g., macrophages, cancer-associated fibroblasts (CAFs), mesenchymal stromal-/stem-like cells (MSC)) (heterotypic fusion) represents a rare event. Accordingly, the clinical relevance of cancer-cell fusion events appears questionable. However, enhanced tumor growth and/or development of certain metastases can originate from cancer-cell fusion. Formation of hybrid cells after cancer-cell fusion requires a post-hybrid selection process (PHSP) to cope with genomic instability of the parental nuclei and reorganize survival and metabolic functionality. The present review dissects mechanisms that contribute to a PHSP and resulting functional alterations of the cancer hybrids. Based upon new properties of cancer hybrid cells, the arising clinical consequences of the subsequent tumor heterogeneity after cancer-cell fusion represent a major therapeutic challenge. However, cellular partners during cancer-cell fusion such as MSC within the tumor microenvironment or MSC-derived exosomes may provide a suitable vehicle to specifically address and deliver anti-tumor cargo to cancer cells.

Apatinib Suppresses Gastric Cancer Stem Cells Properties by Inhibiting the Sonic Hedgehog Pathway

The presence of gastric cancer stem cells (GCSCs) marks the onset of gastric carcinoma. The sonic hedgehog (SHH) pathway plays a vital role in the maintenance of GCSC characteristics. Apatinib has been approved in China for advanced gastric cancer (GC) treatment. However, whether apatinib can target GCSCs and affect the SHH pathway remains unclear. The present study aimed to investigate the underlying mechanism of apatinib’s antitumor effects on GC. The expression levels of GCSC markers and number of CD133⁺ cells were significantly elevated in the sphere-forming cells. Apatinib effectively suppressed GCSC traits by inhibiting tumorsphere formation and cell proliferation, suppressing GCSC markers expression and CD133⁺ cell number, and inducing apoptosis. Apatinib downregulated the activation of the SHH pathway; while upregulation of the SHH pathway attenuated the inhibitory effects of apatinib on GCSCs. Moreover, apatinib treatment significantly delayed tumor growth and inhibited GCSC characteristics in the xenograft model. Our data suggested that apatinib exhibited inhibitory effects on GCSCs by suppressing SHH pathway both in vitro and in vivo, thus providing new insights into the therapeutic application of apatinib in GCSC suppression and advanced gastric cancer treatment.

Future Match Making: When Pediatric Oncology Meets Organoid Technology

Unlike adult cancers that frequently result from the accumulation in time of mutational “hits” often linked to lifestyle, childhood cancers are emerging as diseases of dysregulated development through massive epigenetic alterations. The ability to reconstruct these differences in cancer models is therefore crucial for better understanding the uniqueness of pediatric cancer biology. Cancer organoids (i.e., tumoroids) represent a promising approach for creating patient-derived in vitro cancer models that closely recapitulate the overall pathophysiological features of natural tumorigenesis, including intra-tumoral heterogeneity and plasticity. Though largely applied to adult cancers, this technology is scarcely used for childhood cancers, with a notable delay in technological transfer. However, tumoroids could provide an unprecedented tool to unravel the biology of pediatric cancers and improve their therapeutic management. We herein present the current state-of-the-art of a long awaited and much needed matchmaking.

Insight into the role of multiple signaling pathways in regulating cancer stem cells of gynecologic cancers

Mounting evidence has demonstrated that a myriad of developmental signaling pathways, such as the Wnt, Notch, Hedgehog and Hippo, are frequently deregulated and play a critical role in regulating cancer stem cell (CSC) activity in human cancers, including gynecologic malignancies. In this review article, we describe an overview of various signaling pathways in human cancers. We further discuss the developmental roles how these pathways regulate CSCs from experimental evidences in gynecologic cancers. Moreover, we mention several compounds targeting CSCs in gynecologic cancers to enhance the treatment outcomes. Therefore, these signaling pathways might be the potential targets for developing targeted therapy in gynecologic cancers.

Drug Resistance in Metastatic Breast Cancer: Tumor Targeted Nanomedicine to the Rescue

Breast cancer, specifically metastatic breast, is a leading cause of morbidity and mortality in women. This is mainly due to relapse and reoccurrence of tumor. The primary reason for cancer relapse is the development of multidrug resistance (MDR) hampering the treatment and prognosis. MDR can occur due to a multitude of molecular events, including increased expression of efflux transporters such as P-gp, BCRP, or MRP1; epithelial to mesenchymal transition; and resistance development in breast cancer stem cells. Excessive dose dumping in chemotherapy can cause intrinsic anti-cancer MDR to appear prior to chemotherapy and after the treatment. Hence, novel targeted nanomedicines encapsulating chemotherapeutics and gene therapy products may assist to overcome cancer drug resistance. Targeted nanomedicines offer innovative strategies to overcome the limitations of conventional chemotherapy while permitting enhanced selectivity to cancer cells. Targeted nanotheranostics permit targeted drug release, precise breast cancer diagnosis, and importantly, the ability to overcome MDR. The article discusses various nanomedicines designed to selectively target breast cancer, triple negative breast cancer, and breast cancer stem cells. In addition, the review discusses recent approaches, including combination nanoparticles (NPs), theranostic NPs, and stimuli sensitive or “smart” NPs. Recent innovations in microRNA NPs and personalized medicine NPs are also discussed. Future perspective research for complex targeted and multi-stage responsive nanomedicines for metastatic breast cancer is discussed.

Acquisition of cancer stem cell capacities after spontaneous cell fusion

Background

Cancer stem/Initiating cell (CS/IC) hypothesis argues that CS/ICs are responsible of tumour initiation, drug resistance, metastasis or disease relapse. Their detection in several cancers supports this concept. However, their origin is still misunderstood. Cell fusion is shown to take part in the formation of CS/ICs, i.e. fusion between mesenchymal stem cell and cancer cell. In a previous paper, we described that fusion leads to hybrids with metastatic capacity. This process triggered genomic rearrangements in hybrid cells together with increased metastasis development. Here, we hypothesize that cell fusion could be strong enough to provoke a cellular reprogramming and the acquisition of CS/IC properties, promoting metastasis formation.

Methods

After spontaneous cell fusion between E6E7 (IMR90 with the oncogenes E6 and E7) and RST (IMR90 fully transformed) cell lines, hybrid cells were selected by dual antibiotic selection. Cancer stem cells capacities were evaluated regarding capacity to form spheres, expression of stem cell markers and the presence of ALDHhigh cells.

Results

Our data show that after cell fusion, all hybrids contain a percentage of cells with CS/ICs properties, regarding. Importantly, we lastly showed that NANOG inhibition in H1 hybrid decreases this migration capacity while having no effect on the corresponding parental cells.

Conclusions

Altogether these results indicate that the combination of CS/ICs properties and genomic rearrangement in hybrids is likely to be key to tumour progression.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-021-07979-2.

Identification of hub genes and compounds controlling ovarian cancer stem cell characteristics via stemness indices analysis

Background

Ovarian cancer (OC) is the most lethal gynecological malignancy. It has been reported that cancer stem cells (CSCs) play a crucial role in disseminated metastases in abdominal cavity and chemotherapy resistance of high-grade serous OC. However, the overall gene expression features of OC stem cells have not been clarified.

Methods

Expression datasets of 379 OC samples and 88 normal tissues were downloaded from The Cancer Genome Atlas (TCGA) and the Genotype Tissue Expression (GTEx) project. Differentially expressed genes (DEGs) were screened using the “limma” package in R software. Among the DEGs, modules and hub genes that were highly related to messenger RNA expression-based stemness index (mRNAsi) and epigenetically regulated mRNAsi indices were identified via weighted gene co-expression network analysis (WGCNA). These hub genes were considered to be associated with OC stem cells. The Gene Ontology (GO) project and the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis was used to identify the main biological processes that hub genes participated in. Finally, Connectivity Map (CMap) was used to predict compounds that disturb the hub genes.

Results

We identified 2,253 DEGs; of these, 31 had a significantly positive correlation to mRNAsi indices and were upregulated in OC, while 41 of them had a significantly negative correlation with mRNAsi indices and were downregulated in OC. Correlation analysis indicated that hub genes from the same module composed a dense interaction network. GO and KEGG enrichment analysis demonstrated that hub genes primarily play roles in cell division and proliferation. Moreover, the compounds that may disturb hub genes were identified. Of these, 11 compounds, including MS-275, DL-thiorphan, and GW-8510, which have never been studied in OC stem cells, were screened as underlying treatments targeting OC stem cells.

Conclusions

Altogether, 72 hub genes that were closely linked to OC stem cell characteristics were found to mainly participate in cell division and proliferation. Moreover, compounds that disturb these hub gens were identified and can be considered underlying targets for inhibiting OC stem cells.

Clinical Perspectives in Addressing Unsolved Issues in (Neo)Adjuvant Therapy for Primary Breast Cancer

The treatment of primary breast cancer has evolved over the past 50 years based on the concept that breast cancer is a systemic disease, with the escalation of adjuvant and neoadjuvant therapies and de-escalation of breast cancer surgery. Despite the development of these therapies, recurrence with distant metastasis during the 10 years after surgical treatment is observed, albeit infrequently. Recent advances in genomic analysis based on circulating tumor cells and circulating tumor DNA have enabled the development of targeted therapies based on genetic mutations in residual tumor cells. A paradigm shift involving the application of neoadjuvant chemotherapy (NAC) has enabled the prediction of treatment response and long-term prognoses; additional adjuvant chemotherapy targeting remaining tumor cells after NAC improves survival. The activation of antitumor immunity by anticancer agents may be involved in the eradication of residual tumor cells. Elucidation of the manner in which antitumor immunity is induced by anticancer agents and unknown factors, and the overcoming of drug resistance via the targeted eradication of residual tumor cells based on genomic profiles, will inevitably lead to the achievement of 0% distant recurrence and a complete cure for primary breast cancer.

SH3GL3 acts as a novel tumor suppressor in glioblastoma tumorigenesis by inhibiting STAT3 signaling

Glioblastoma (GBM) is the most severe malignant tumors of the central nervous system. Glioblastoma stem cells (GSCs) are considered to account for tumor initiation, therapeutic resistance, and tumor relapse. Yet the underlying mechanisms of GSC stemness maintenance remain largely unknown. Abnormal activation of STAT3 signaling is required for GBM tumorigenesis and GSC self-renewal. In this study, we provide evidence that SH3GL3 was weakly expressed in GBM and its high expression correlated with a favorable prognosis for GBM patients. Ectopic of SH3GL3 expression considerably inhibits GBM cell malignant behaviors, including GBM cell proliferation, migration as well as GSCs self-renewal ability. Mechanistically, we first found that SH3GL3 interacts with STAT3, which thereby inhibiting STAT3 nuclear localization. Overexpression of constitutively activated (STAT3-C) restored the growth, migration and self-renewal ability impaired by overexpression of SH3GL3. Together, our work shed insight on a critical regulatory mechanism mediated by SH3GL3 to decrease the stem cell-like property and tumorigenic potential.

FOLFOX Therapy Induces Feedback Upregulation of CD44v6 through YB-1 to Maintain Stemness in Colon Initiating Cells

Cancer initiating cells (CICs) drive tumor formation and drug-resistance, but how they develop drug-resistance characteristics is not well understood. In this study, we demonstrate that chemotherapeutic agent FOLFOX, commonly used for drug-resistant/metastatic colorectal cancer (CRC) treatment, induces overexpression of CD44v6, MDR1, and oncogenic transcription/translation factor Y-box-binding protein-1 (YB-1). Our study revealed that CD44v6, a receptor for hyaluronan, increased the YB-1 expression through PGE2/EP1-mTOR pathway. Deleting CD44v6, and YB-1 by the CRISPR/Cas9 system attenuates the in vitro and in vivo tumor growth of CICs from FOLFOX resistant cells. The results of DNA:CD44v6 immunoprecipitated complexes by ChIP (chromatin-immunoprecipitation) assay showed that CD44v6 maintained the stemness traits by promoting several antiapoptotic and stemness genes, including cyclin-D1,BCL2,FZD1,GINS-1, and MMP9. Further, computer-based analysis of the clones obtained from the DNA:CD44v6 complex revealed the presence of various consensus binding sites for core stemness-associated transcription factors “CTOS” (c-Myc, TWIST1, OCT4, and SOX2). Simultaneous expressions of CD44v6 and CTOS in CD44v6 knockout CICs reverted differentiated CD44v6-knockout CICs into CICs. Finally, this study for the first time describes a positive feedback loop that couples YB-1 induction and CD44 alternative splicing to sustain the MDR1 and CD44v6 expressions, and CD44v6 is required for the reversion of differentiated tumor cells into CICs.

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.

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.

Breast cancers, mammary stem cells, and cancer stem cells, characteristics, and hypotheses

The cellular heterogeneity of breast cancers still represents a major therapeutic challenge. The latest genomic studies have classified breast cancers in distinct clusters to inform the therapeutic approaches and predict clinical outcomes. The mammary epithelium is composed of luminal and basal cells, and this seemingly hierarchical organization is dependent on various stem cells and progenitors populating the mammary gland. Some cancer cells are conceptually similar to the stem cells as they can self-renew and generate bulk populations of nontumorigenic cells. Two models have been proposed to explain the cell of origin of breast cancer and involve either the reprogramming of differentiated mammary cells or the dysregulation of mammary stem cells or progenitors. Both hypotheses are not exclusive and imply the accumulation of independent mutational events. Cancer stem cells have been isolated from breast tumors and implicated in the development, metastasis, and recurrence of breast cancers. Recent advances in single-cell sequencing help deciphering the clonal evolution within each breast tumor. Still, few clinical trials have been focused on these specific cancer cell populations.

Biological roles of piRNAs in colorectal cancer

Colorectal cancer (CRC) is one of the most common malignancies worldwide and a major cause of cancer-related deaths. Numerous studies have suggested that piwi-interacting RNAs (piRNAs), a new type of non-coding RNA (ncRNA), are closely related to the occurrence and development of cancer. piRNAs have been shown to regulate the occurrence of CRC by modulating multiple molecular signaling pathways. Here, the roles of piRNAs in CRC were reviewed to provide evidence for their potential as molecular targets for CRC.

Differential mechanisms of autophagy in cancer stem cells: Emphasizing gastrointestinal cancers

Gastrointestinal (GI) cancers are one of the most common forms of malignancies and still are the most important cause of cancer-related mortality worldwide. Autophagy is a conserved catabolic pathway involving lysosomal degradation and recycling of whole cellular components, which is essential for cellular homeostasis. For instance, it acts as a pivotal intracellular quality control and repair mechanism but also implicated in cell reformation during cell differentiation and development. Indeed, GI cancer stem cells (CSCs) are thought to be responsible for tumour initiation, traditional therapies resistance, metastasis and tumour recurrence. Molecular mechanisms of autophagy in normal vs CSCs gain great interest worldwide. Here, we shed light on the role of autophagy in normal stem cells differentiation for embryonic progression and its role in maintaining the activity and self-renewal capacity of CSCs which offer novel viewpoints on promising cancer therapeutic strategies based on the differential roles of autophagy in CSCs.

Role of Wnt/β-Catenin Signaling in the Chemoresistance Modulation of Colorectal Cancer

Colorectal cancer (CRC) is a common malignancy with high morbidity and mortality worldwide. To date, chemotherapy plays an important role in the treatment of CRC patients. Multidrug resistance (MDR) is one of the major hurdles in chemotherapy for CRC, and the underlying mechanisms need to be explored. Studies have demonstrated that Wnt/β-catenin signaling plays a critical role in oncogenesis and tumor development, and its function in inhibiting apoptosis could facilitate tumor chemoresistance. Recent investigations have also suggested the regulatory effects of the Wnt/β-catenin signaling pathway in response to chemotherapeutic agents in CRC. Here, we particularly focus on reviewing the evidences suggesting the mechanisms of Wnt/β-catenin signaling in the chemoresistance modulation of colorectal cancer.

Dissecting pharmacological effects of chloroquine in cancer treatment: interference with inflammatory signaling pathways

Chloroquines are 4-aminoquinoline-based drugs mainly used to treat malaria. At pharmacological concentrations, they have significant effects on tissue homeostasis, targeting diverse signaling pathways in mammalian cells. A key target pathway is autophagy, which regulates macromolecule turnover in the cell. In addition to affecting cellular metabolism and bioenergetic flow equilibrium, autophagy plays a pivotal role at the interface between inflammation and cancer progression. Chloroquines consequently have critical effects in tissue metabolic activity and importantly, in key functions of the immune system. In this article, we will review the work addressing the role of chloroquines in the homeostasis of mammalian tissue, and the potential strengths and weaknesses concerning their use in cancer therapy.

Suppressing STAT5 signaling affects osteosarcoma growth and stemness

Osteosarcoma (OS) is the most common primary bone tumor that primarily affects children and adolescents. Studies suggested that dysregulation JAK/STAT signaling promotes the development of OS. Cells treated with pimozide, a STAT5 inhibitor suppressed proliferation and colony formation and induced sub G0/G1 cell cycle arrest and apoptosis. There was a reduction in cyclin D1 and CDK2 expression and Rb phosphorylation, and activation of Caspase-3 and PARP cleavage. In addition, pimozide suppressed the formation of 3-dimensional osteospheres and growth of the cells in the Tumor in a Dish lung organoid system. Furthermore, there was a reduction in expression of cancer stem cell marker proteins DCLK1, CD44, CD133, Oct-4, and ABCG2. More importantly, it was the short form of DCLK1 that was upregulated in osteospheres, which was suppressed in response to pimozide. We further confirmed by flow cytometry a reduction in DCLK1+ cells. Moreover, pimozide inhibits the phosphorylation of STAT5, STAT3, and ERK in OS cells. Molecular docking studies suggest that pimozide interacts with STAT5A and STAT5B with binding energies of −8.4 and −6.4 Kcal/mol, respectively. Binding was confirmed by cellular thermal shift assay. To further understand the role of STAT5, we knocked down the two isoforms using specific siRNAs. While knockdown of the proteins did not affect the cells, knockdown of STAT5B reduced pimozide-induced necrosis and further enhanced late apoptosis. To determine the effect of pimozide on tumor growth in vivo, we administered pimozide intraperitoneally at a dose of 10 mg/kg BW every day for 21 days in mice carrying KHOS/NP tumor xenografts. Pimozide treatment significantly suppressed xenograft growth. Western blot and immunohistochemistry analyses also demonstrated significant inhibition of stem cell marker proteins. Together, these data suggest that pimozide treatment suppresses OS growth by targeting both proliferating cells and stem cells at least in part by inhibiting the STAT5 signaling pathway.

Chronic exposure to cadmium induces a malignant transformation of benign prostate epithelial cells

Epidemiological evidence suggests that cadmium (Cd) is one of the causative factors of prostate cancer, but the effect of Cd on benign prostatic hyperplasia (BPH) remains unclear. This study aimed to determine whether Cd exposure could malignantly transform BPH1 cells and, if so, to dissect the mechanism of action. We deciphered the molecular signaling responsible for BPH1 transformation via RNA-sequencing and determined that Cd induced the expression of zinc finger of the cerebellum 2 (ZIC2) in BPH1 cells. We noted Cd exposure increased ZIC2 expression in the Cd-transformed BPH1 cells that in turn promoted anchorage-independent spheroids and increased expression of stem cell drivers, indicating their role in stem cell renewal. Subsequent silencing of ZIC2 expression in transformed cells inhibited spheroid formation, stem cell marker expression, and tumor growth in nude mice. At the molecular level, ZIC2 interacts with the glioma-associated oncogene family (GLI) zinc finger 1 (GLI1), which activates prosurvival factors (nuclear factor NFκB, B-cell lymphoma-2 (Bcl2), as well as an X-linked inhibitor of apoptosis protein (XIAP)) signaling in Cd-exposed BPH1 cells. Conversely, overexpression of ZIC2 in BPH1 cells caused spheroid formation confirming the oncogenic function of ZIC2. ZIC2 activation and GLI1 signaling induction by Cd exposure in primary BPH cells confirmed the clinical significance of this oncogenic function. Finally, human BPH specimens had increased ZIC2 versus adjacent healthy tissues. Thus, we report direct evidence that Cd exposure induces malignant transformation of BPH via activation of ZIC2 and GLI1 signaling.

TRIP6 enhances stemness property of breast cancer cells through activation of Wnt/β-catenin

BACKGROUND

The urgent problem in the treatment of breast cancer is the recurrence induced by breast cancer stem cells (CSCs). Understanding the role and molecular mechanism of specific molecules in breast cancer stem cells can provide a theoretical basis for better treatment. TRIP6 is an adapter protein which belongs to the zyxin family of LIM proteins and is important in regulating the functions of CSCs. The present study aims to investigate the effects and mechanism of TRIP6 in breast cancer.

METHODS

TRIP6 expression in breast cancer cells and tissues were detected by Real-Time PCR, western blot and immunohistochemistry (IHC). MTT assays, colony formation assays, Xenografted tumor model and mammosphere formation assays were performed to investigate the oncogenic functions of TRIP6 in the tumorigenic capability and the tumor-initiating cell-like phenotype of breast cancer cells in vitro and in vivo. Luciferase reporter, subcellular fractionation and immunofluorescence staining assays were performed to determine the underlying mechanism of TRIP6-mediated stemness of breast cancer cells.

RESULTS

TRIP6 expression was significantly upregulated in breast cancer, and was closely related to the clinicopathologic characteristics, poor overall survival (OS), relapse-free survival (RFS) and poor prognosis of breast cancer patients. Functional studies revealed that overexpression of TRIP6 significantly enhanced proliferative, tumorigenicity capability and the cancer stem cell-like properties of breast cancer in vitro and in vivo. On the contrary, silencing TRIP6 achieved the opposite results. Notably, we found that TRIP6 promoted Wnt/β-catenin signaling pathway in breast cancer to strengthen the tumor-initiating cell-like phenotype of breast cancer cells.

CONCLUSIONS

This study indicates that TRIP6 plays an important role in maintaining the stem cell-like characteristics of breast cancer cells, supporting the significance of TRIP6 as a novel potential prognostic biomarker and therapeutic target for diagnosis and treatment of breast cancer.

Foretinib Inhibits Cancer Stemness and Gastric Cancer Cell Proliferation by Decreasing CD44 and c-MET Signaling

Purpose

CD44 isoforms are highly expressed in cancer stem cells, initiating tumor growth and sustaining tumor self-renewal. Among these isoforms, CD44 variant 9 (CD44v9) is overexpressed in chronic inflammation-induced cancer. CD44 and the mesenchymal-to-epithelial transition (MET) receptor tyrosine kinase are coactivated in some gastric cancers (GCs). In this study, we characterized MET and CD44 expression and signaling in human GC cell lines and analyzed differences in the susceptibility of these lines to foretinib.

Patients and Methods

We analyzed cell viability and the rate of apoptotic cells using MTS assays and flow cytometry, respectively. Gene and protein expression were assessed by quantitative reverse-transcription polymerase chain reaction (qRT-PCR) and immunoblotting, respectively.

Results

Foretinib treatment resulted in dose-dependent inhibition of growth in c-MET-amplified MKN45 and SNU620 cells with concomitant induction of apoptosis, but not in c-MET-reduced MKN28 and AGS cells. Foretinib treatment also significantly reduced phosphor-c-MET, phosphor-AKT, beta-catenin, and COX-2 protein expression in MKN45 and SNU620 cells. Interestingly, foretinib significantly reduced CD44, CD44v9, COX-2, OCT3/4, CCND1, c-MYC, VEGFA, and HIF-1a gene expression in CD44 and MET coactivated MKN45 cells and increased CD44s gene expression; in contrast, these drugs were only slightly active against SNU620 cells.

Conclusion

The results of this study indicate that foretinib could be a therapeutic agent for the prevention or treatment of GCs positive for CD44v9 and c-MET.

Glycyrrhizic Acid-Induced Differentiation Repressed Stemness in Hepatocellular Carcinoma by Targeting c-Jun N-Terminal Kinase 1

Hepatocellular carcinoma (HCC) is one of the most common malignant cancers with poor prognosis and high incidence. Cancer stem cells play a vital role in tumor initiation and malignancy. The degree of differentiation of HCC is closely related to its stemness. Glycyrrhizic acid (GA) plays a critical role in inhibiting the degree of malignancy of HCC. At present, the effect of GA on the differentiation and stemness of HCC has not been reported, and its pharmacological mechanism remains to be elucidated. This study evaluated the effect of GA on the stemness of HCC and investigated its targets through proteomics and chemical biology. Results showed that GA can repress stemness and induce differentiation in HCC in vitro. GEO analysis revealed that cell differentiation and stem cell pluripotency were up-regulated and down-regulated after GA administration, respectively. Virtual screening was used to predict the c-Jun N-terminal kinase 1 (JNK1) as a direct target of GA. Moreover, chemical biology was used to verify the interaction of JNK1 and GA. Experimental data further indicated that JNK1 inhibits stemness and induces differentiation of HCC. GA exerts its function by targeting JNK1. Clinical data analysis from The Cancer Genome Atlas also revealed that JNK1 can aggravate the degree of malignancy of HCC. The results indicated that, by targeting JNK1, GA can inhibit tumor growth through inducing differentiation and repressing stemness. Furthermore, GA enhanced the anti-tumor effects of sorafenib in HCC treatment. These results broadened our insight into the pharmacological mechanism of GA and the importance of JNK1 as a therapeutic target for HCC treatment.

Targeting signalling pathways and the immune microenvironment of cancer stem cells - a clinical update

Cancer stem cells (CSCs) have important roles in tumour development, relapse and metastasis; the intrinsic self-renewal characteristics and tumorigenic properties of these cells provide them with unique capabilities to resist diverse forms of anticancer therapy, seed recurrent tumours, and disseminate to and colonize distant tissues. The findings of several studies indicate that CSCs originate from non-malignant stem or progenitor cells. Accordingly, inhibition of developmental signalling pathways that are crucial for stem and progenitor cell homeostasis and function, such as the Notch, WNT, Hedgehog and Hippo signalling cascades, continues to be pursued across multiple cancer types as a strategy for targeting the CSCs hypothesized to drive cancer progression - with some success in certain malignancies. In addition, with the renaissance of anticancer immunotherapy, a better understanding of the interplay between CSCs and the tumour immune microenvironment might be the key to unlocking a new era of oncological treatments associated with a reduced propensity for the development of resistance and with enhanced antimetastatic activity, thus ultimately resulting in improved patient outcomes. Herein, we provide an update on the progress to date in the clinical development of therapeutics targeting the Notch, WNT, Hedgehog and Hippo pathways. We also discuss the interactions between CSCs and the immune system, including the potential immunological effects of agents targeting CSC-associated developmental signalling pathways, and provide an overview of the emerging approaches to CSC-targeted immunotherapy.