Lessons from common markers of tumor-initiating cells in solid cancers

Molecular mechanisms and therapeutic strategies in overcoming chemotherapy resistance in cancer

Cancer remains a leading cause of mortality globally and a major health burden, with chemotherapy often serving as the primary therapeutic option for patients with advanced-stage disease, partially compensating for the limitations of non-curative treatments. However, the emergence of chemotherapy resistance significantly limits its efficacy, posing a major clinical challenge. Moreover, heterogeneity of resistance mechanisms across cancer types complicates the development of universally effective diagnostic and therapeutic approaches. Understanding the molecular mechanisms of chemoresistance and identifying strategies to overcome it are current research focal points. This review provides a comprehensive analysis of the key molecular mechanisms underlying chemotherapy resistance, including drug efflux, enhanced DNA damage repair (DDR), apoptosis evasion, epigenetic modifications, altered intracellular drug metabolism, and the role of cancer stem cells (CSCs). We also examine specific causes of resistance in major cancer types and highlight various molecular targets involved in resistance. Finally, we discuss current strategies aiming at overcoming chemotherapy resistance, such as combination therapies, targeted treatments, and novel drug delivery systems, while proposing future directions for research in this evolving field. By addressing these molecular barriers, this review lays a foundation for the development of more effective cancer therapies aimed at mitigating chemotherapy resistance.

Overcoming resistance in small-cell lung cancer

INTRODUCTION

Small-cell lung cancer (SCLC) accounts for 15% of lung cancers and has a dismal prognosis due to early dissemination and acquired chemoresistance. The initial good response to chemotherapy is followed by refractory relapses within 1-2 years. Mechanisms leading to chemoresistance are not clear and progress is poor.

AREAS COVERED

This article reviews the current evidence of the resistance of SCLCs at the cellular level including alteration of key proteins and the possible presence of cancer stem cells (CSCs). Without compelling evidence for cellular mechanisms and clinical failures of novel approaches, the study of SCLC has advanced to the role of 3D tumor cell aggregates in chemoresistance.

EXPERT OPINION

The scarcity of viable tumor specimen from relapsed SCLC patients has hampered the investigations of acquired chemoresistance but a panel of nine SCLC circulating tumor cell (CTC) cell lines have revealed characteristics of SCLC in the advanced refractory states. The chemoresistance of relapsed SCLC seems to be linked to the spontaneous formation of large spheroids, termed tumorospheres, which contain resistant quiescent and hypoxic cells shielded by a physical barrier. So far, drugs to tackle large tumor spheroids are in preclinical and early clinical development.

LncRNA PCAT6 is a predictor of poor prognosis of colorectal cancer

BACKGROUND

The long non-coding RNA (lncRNA) prostate cancer-associated transcript 6 (PCAT6) has been studied in many cancers, yet its relationship with colorectal cancer (CRC) remains poorly defined. Here, we conducted an analysis of The Cancer Genome Atlas (TCGA) database to better clarify the role of PCAT6 in this cancer type.

METHODS

Wilcoxon rank-sum tests were utilized to assess relative levels of PCAT6 in CRC tumors and normal tissues, while logistic regression analyses were utilized to compare the relationships between PCAT6 levels and clinicopathological findings. Kaplan-Meier curves and Cox regression analyses were used to gauge correlations between PCAT6 and patient survival outcomes, while the biological roles of this lncRNA were investigated via a gene set enrichment analysis (GSEA) approach. The expression level of PCAT6 in CRC cell lines was detected by quantitative reverse transcription polymerase chain reaction (qRT-PCR).

RESULTS

PCAT6 levels were significantly correlated with CRC patient lymph node metastasis (N) stage [odds ratio (OR) =1.8 for N1 & N2 vs. N0], lymphatic invasion [OR =1.9 for yes vs. no), distant metastasis (M stage) (OR =2.1 for M1 vs. M0), carcinoembryonic antigen (CEA) level (OR =1.9 for >5 vs. ≤5), perineural invasion (OR =1.9 for yes vs. no), pathologic stage (OR =1.9 for stage III/IV vs. stage I/II), and neoplasm type (OR =2.1 for rectal adenocarcinoma vs. colon adenocarcinoma) (all P<0.05). CRC patients expressing higher PCAT6 levels exhibited poorer survival outcomes than those expressing low levels of this lncRNA (P=0.017), and in univariate analyses, higher PCAT6 levels were linked to worse overall survival [hazard ratio (HR) =1.540; 95% confidence interval (CI): 1.079-2.199; P=0.017], with this relationship also being preserved in a multivariate analysis (HR =6.892; 95% CI: 1.713-27.727, P=0.007). GSEA revealed high PCAT6 expression to be linked to differential DNA methylation enrichment, with high PCAT6 levels being associated with changes in base excision repair, cellular senescence, G2/M DNA damage checkpoint, chromatin-modifying enzyme, and gene silencing by RNA activity. The high expression of lncRNA PCAT6 in CRC cell lines was demonstrated by PCR experiments.

CONCLUSIONS

PCAT6 represents a promising prognostic biomarker of poor CRC patient survival outcomes, with DNA methylation and RNA-mediated gene silencing being potentially promising mechanistic pathways whereby this lncRNA may shape patient outcomes.

Phenotypic and functional characterization of subpopulation of Imatinib resistant chronic myeloid leukemia cell line

PURPOSE

Chronic myeloid leukemia (CML) is a hematological malignancy characterized by the presence of BCR-ABL protein. Imatinib (IMA) is considered as the first line therapy in management of CML which particularly targets the BCR-ABL tyrosine kinase protein. However, emergence of resistance to IMA hinders its clinical efficiency. Hence, identifying novel targets for therapeutic approaches in CML treatment is of great importance. Here, we characterize a new subpopulation of highly adherent IMA-resistant CML cells that express stemness and adhesion markers compared to naive counterparts.

MATERIALS AND METHODS

We performed several experimental assays including FISH, flow cytometry, and gene expression assays. Additionally, bioinformatics analysis was performed by normalized web-available microarray data (GSE120932) to revalidate and introduce probable biomarkers. Protein-protein interactions (PPI) network was analyzed by the STRING database employing Cytoscape v3.8.2.

RESULTS

Our findings demonstrated that constant exposure to 5 ​μM IMA led to development of the adherent phenotype (K562R-adh). FISH and BCR-ABL expression analysis indicated that K562R-adh cells were derived from the original cells (K562R). In order to determine the role of various genes involved in epithelial-mesenchymal transition (EMT) and stem cell characterization, up/down-regulation of various genes including cancer stem cell (CSC), adhesion and cell surface markers and integrins were observed which was similar to the findings of the GSE120932 dataset.

CONCLUSION

Treating CML patients with tyrosine kinase inhibitors (TKIs) as well as targeting adhesion molecules deemed to be effective approaches in prevention of IMA resistance emergence which in turn may provide promising effects in the clinical management of CML patients.

Update on Chemoresistance Mechanisms to First-Line Chemotherapy for Gallbladder Cancer and Potential Reversal Strategies

OBJECTIVE

Gallbladder cancer (GBC) mortality remains high and chemoresistance is increasing. This review consolidates what is known about the mechanisms of chemoresistance to inform and accelerate the development of novel GBC-specific chemotherapies.

METHODS

Studies related to GBC-related chemoresistance were systematically screened in PubMed using the advanced search function. Search terms included GBC, chemotherapy, and signaling pathway.

RESULTS

Analysis of existing studies showed that GBC has poor sensitivity to cisplatin, gemcitabine (GEM), and 5-fluorouracil. DNA damage repair-related proteins, including CHK1, V-SCR, and H2AX, are involved in tumor adaptation to drugs. GBC-specific chemoresistance is often accompanied by changes in the apoptosis and autophagy-related molecules, BCL-2, CRT, and GBCDRlnc1. CD44 + and CD133 + GBC cells are less resistant to GEM, indicating that tumor stem cells are also involved in chemoresistance. In addition, glucose metabolism, fat synthesis, and glutathione metabolism can influence the development of drug resistance. Finally, chemosensitizers such as lovastatin, tamoxifen, chloroquine, and verapamil are able improve the therapeutic effect of cisplatin or GEM in GBC.

CONCLUSIONS

This review summarizes recent experimental and clinical studies of the molecular mechanisms of chemoresistance, including autophagy, DNA damage, tumor stem cells, mitochondrial function, and metabolism, in GBC. Information on potential chemosensitizers is also discussed. The proposed strategies to reverse chemoresistance should inform the clinical use of chemosensitizers and gene-based targeted therapy for this disease.

The role of stem cells in small-cell lung cancer: evidence from chemoresistance to immunotherapy

Small cell lung cancer (SCLC) is the most aggressive subtype of lung cancer, accounting for approximately 15% among all lung cancers. Despite the ability of chemotherapy, the first-line treatment for SCLC, to rapidly shrink tumors, nearly all patients experience recurrence and metastasis within a few months. Cancer stem cells (CSCs) are a small population of tumor cells responsible for tumorigenesis, metastasis, and recurrence after treatment, which play a crucial role in chemoresistance by promoting DNA repair and expression of drug resistance-associated proteins. Thus, targeting CSCs has been successful in certain malignancies. Tumor therapy has entered the era of immunotherapy and numerous preclinical trials have demonstrated the effectiveness of immunotherapeutic approaches targeting CSCs, such as tumor vaccines and chimeric antigen receptor (CAR) T cell, and the feasibility of combining them with chemotherapy. Therefore, a deeper understanding of the interaction between CSCs and immune system is essential to facilitate the advances of new immunotherapies approaches targeting CSCs as well as combination with standard drugs such as chemotherapy. This narrative review summarizes the mechanisms of chemoresistance of CSCs in SCLC and the latest advances in targeted therapies. Thereafter, we discuss the effects of CSCs on tumor immune microenvironment in SCLC and corresponding immunotherapeutic approaches. Eventually, we propose that the combination of immunotherapy targeting CSCs with standard drugs is a promising direction for SCLC therapies.

MiR-942-3p as a Potential Prognostic Marker of Gastric Cancer Associated with AR and MAPK/ERK Signaling Pathway

Gastric cancer is a common tumor with high morbidity and mortality. MicroRNA (miRNA) can regulate gene expression at the translation level and various tumorigenesis processes, playing an important role in tumor occurrence and prognosis. This study aims to screen miRNA associated with gastric cancer prognosis as biomarkers and explore the regulatory genes and related signaling pathways. In this work, R language was used for the standardization and differential analysis of miRNA and mRNA expression profiles. Samples were randomly divided into a testing group and a training group. Subsequently, we built the five miRNAs (has-miR-9-3p, has-miR-135b-3p, has-miR-143-5p, has-miR-942-3p, has-miR-196-3p) prognostic modules, verified and evaluated their prediction ability by the Cox regression analysis. They can be used as an independent factor in the prognosis of gastric cancer. By predicting and analyzing potential biological functions of the miRNA target genes, this study found that the AR gene was not only a hub gene in the PPI network, but also associated with excessive survival of patients. In conclusion, this study demonstrated that hsa-miR-942-3p could be a potential prognostic marker of gastric cancer associated with the AR and MAPK/ERK signaling pathways. The results of this study provide insights into the occurrence and development of gastric cancer.

Impaired differentiation potential of CD34-positive cells derived from mouse hair follicles after long-term culture

Hair follicle epithelial stem cells (HFSCs), which exist in the bulge region, have important functions for homeostasis of skin as well as hair follicle morphogenesis. Although several methods for isolation of HFSCs using a variety of stem cell markers have been reported, few investigations regarding culture methods or techniques to yield long-term maintenance of HFSCs in vitro have been conducted. In the present study, we screened different types of commercially available culture medium for culturing HFSCs. Among those tested, one type was shown capable of supporting the expression of stem cell markers in cultured HFSCs. However, both the differentiation potential and in vivo hair follicle-inducing ability of HFSCs serially passaged using that optimal medium were found to be impaired, probably because of altered responsiveness to Wnt signaling. The changes noted in HFSCs subjected to a long-term culture suggested that the Wnt signaling-related environment must be finely controlled for maintenance of the cells.

Identification of a subpopulation of long-term tumor-initiating cells in colon cancer

Long-term tumor-initiating cells (LT-TICs) are viewed as a quantifiable target for colon cancer therapy owing to their extensive self-renewal and tumorigenic and metastatic capacities. However, it is unknown which subpopulation of colon cancer cells contains LT-TICs. Here, based on the methods for isolating and identifying cancer stem cells (CSCs) and the functional features of LT-TICs, we aimed to identify a subpopulation of LT-TICs. Among the six cell lines assessed, our results showed that CD133 and CD44 coexpression was only detected in HCT116 and HT29 cell lines. In HCT116 and HT29 cells, CD133⁺CD44⁺ cells not only shared the extensive tumorigenic potential of LT-TICs but also functionally reproduced the behaviors of LT-TICs that drive tumor metastasis (TM) formation, suggesting that CD133⁺CD44⁺ cells are a typical representation of LT-TICs in colon cancer. Mechanistically, the enhanced capacity of CD133⁺CD44⁺ cells to drive metastasis involves the up-regulated expression of Wnt-, epithelial–mesenchymal transition (EMT)-, and metastasis-related genes in these cells. Additionally, CD133⁺CD44⁺ cells presented significant chemoresistance compared with corresponding nontumorigenic CD133⁻CD44⁻ cells following exposure to oxaliplatin (OXLP) or 5-fluorouracil (5-FU). Accordingly, CD133⁺CD44⁺ cells contained lower reactive oxygen species (ROS) levels than CD1133⁻CD44⁻ cells, and the low ROS levels in CD133⁺CD44⁺ cells were related to the enhancement of antioxidant defense systems. More importantly, CD133⁺CD44⁺ cells developed less DNA damage after exposure to chemotherapeutics than CD133⁻CD44⁻ cells. In conclusion, we identified a subpopulation of LT-TICs in colon cancer.

The critical role of peroxiredoxin-2 in colon cancer stem cells

Colon cancer stem cells (CCSCs) play an important role in facilitating colon cancer occurrence, metastasis and drug resistance. The results of our previous studies confirmed that the well-studied antioxidant gene peroxiredoxin-2 (PRDX2) promotes colon cancer progression. However, the underlying function and mechanisms associated with PRDX2 remodeling in the context of CCSCs have remained poorly studied. In our present study, we demonstrated that PRDX2 is highly expressed in CD133/CD44-positive colon cancer tissues and spheroid CD133+CD44+ CCSCs. PRDX2 overexpression was shown to be closely correlated with CD133+CD44+ CCSCs in colon cancer. Furthermore, PRDX2 depletion markedly suppressed CD133+CD44+ CCSC stemness maintenance, tumor initiation, migration and invasion and liver metastasis. Furthermore, the expression of various EMT markers and Wnt/β-catenin signaling proteins was altered after PRDX2 inhibition. In addition, PRDX2 knockdown led to increased ROS production in CD133+CD44+ CCSCs, sensitizing CCSCs to oxidative stress and chemotherapy. These results suggest that PRDX2 could be a possible therapeutic target in CCSCs.

Abnormal expression of ABCD3 is an independent prognostic factor for colorectal cancer

ATP binding cassette subfamily D member 3 (ABCD3) is a member of the superfamily of ATP-binding cassette (ABC) transporters, which serve crucial roles in the process of tumor cell resistance to chemotherapy. The present study investigated the diagnostic and prognostic capabilities of ABCD3 in colorectal cancer (CRC) by bioinformatics analysis. Gene expression data and corresponding clinical information of patients with CRC were collected from The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) databases. The results demonstrated that ABCD3 mRNA level was decreased in CRC tissues compared with normal tissues following Wilcoxon test analysis. Furthermore, ABCD3 protein expression was significantly higher in normal colon tissues compared with colon adenocarcinoma tissues according to the Human Protein Atlas. In addition, the area under the Receiver Operating Characteristic curve based on comparison between the tumor and normal groups derived from TCGA and GEO databases demonstrated that the use of ABCD3 mRNA level may be used for the diagnosis of CRC. ABCD3 expression was significantly associated with clinical stage, T stage, and lymph node status following Kruskal-Wallis test or Wilcoxon rank sum test, logistic regression and χ² test. Furthermore, the results from Kaplan-Meier survival analysis indicated that low ABCD3 mRNA expression had a poorer prognosis value compared with ABCD3 high expression in patients with CRC. In addition, results from univariate Cox regression analysis indicated that ABCD3 mRNA expression was associated with overall survival (OS), and results from multivariate Cox analysis indicated that ABCD3 mRNA expression may be considered an independent prognostic factor from other clinical factors, such as clinical stage, sex and age. The results from Gene Set Enrichment Analysis demonstrated that the ABCD3 high-expression phenotype was differentially enriched in five biological processes, including apoptosis, cell cycle, renal cell carcinoma, thyroid cancer and colorectal cancer. The findings from this study demonstrated that ABCD3 mRNA expression may be considered as a potential diagnostic and prognostic biomarker in patients with CRC. ABCD3 expression levels may participate in the regulation of cell apoptosis and cell cycle. In addition, GSEA analysis identified Kyoto Encyclopaedia of Genes and Genomes pathways for renal cell carcinoma, thyroid cancer and CRC involving ABCD3.

A Five-microRNA Signature as Prognostic Biomarker in Colorectal Cancer by Bioinformatics Analysis

Mounting evidence has demonstrated that a lot of miRNAs are overexpressed or downregulated in colorectal cancer (CRC) tissues and play a crucial role in tumorigenesis, invasion, and migration. The aim of our study was to screen new biomarkers related to CRC prognosis by bioinformatics analysis. By using the R language edgeR package for the differential analysis and standardization of miRNA expression profiles from The Cancer Genome Atlas (TCGA), 502 differentially expressed miRNAs (343 up-regulated, 159 down-regulated) were screened based on the cut-off criteria of p < 0.05 and |log2FC|>1, then all the patients (421) with differentially expressed miRNAs and complete survival time, status were then randomly divided into train group (212) and the test group (209). Eight miRNAs with p < 0.005 were revealed in univariate cox regression analysis of train group, then stepwise multivariate cox regression was applied for constituting a five-miRNA (hsa-miR-5091, hsa-miR-10b-3p, hsa-miR-9-5p, hsa-miR-187-3p, hsa-miR-32-5p) signature prognostic biomarkers with obviously different overall survival. Test group and entire group shown the same results utilizing the same prescient miRNA signature. The area under curve (AUC) of receiver operating characteristic (ROC) curve for predicting 5 years survival in train group, test group, and whole cohort were 0.79, 0.679, and 0.744, respectively, which demonstrated better predictive power of prognostic model. Furthermore, Univariate cox regression and multivariate cox regression considering other clinical factors displayed that the five-miRNA signature could serve as an independent prognostic factor. In order to predict the potential biological functions of five-miRNA signature, target genes of these five miRNAs were analyzed by Kyoto Encyclopedia of Genes and Genomes (KEGG) signaling pathway and Gene Ontology (GO) enrichment analysis. The top 10 hub genes (ESR1, ADCY9, MEF2C, NRXN1, ADCY5, FGF2, KITLG, GATA1, GRIA1, KAT2B) of target genes in protein protein interaction (PPI) network were screened by string database and Cytoscape 3.6.1 (plug-in cytoHubba). In addition, 19 of target genes were associated with survival prognosis. Taken together, the current study showed the model of five-miRNA signature could efficiently function as a novel and independent prognosis biomarker and therapeutic target for CRC patients.

Rationales for the Use of Cancer Stem Cells Markers in the Staging of Papillary Thyroid Carcinoma

Fine needle aspiration biopsy (FNAB) is a standard procedure for the detection of thyroid nodules malignancy, yet 10-25% of the sample diagnosed may go undetermined or suspicious. The utility of cancer stem cell markers (CSCM) as a differential diagnosis molecular marker in nodules of suspicious decision in FNAB was hypothesized. Papillary thyroid carcinoma (PTC) and thyroid fibroadenoma (TFA) samples were selected to test the hypothesis. The samples employed in this study were from patients who had thyroid hyperplasia and a suspicious or undetermined diagnosis by FNAB. The patient underwent a successful thyroidectomy at Al-Yarmouk Teaching Hospital in Baghdad between January 2015 and December 2017. All nodule samples underwent a systematic histopathological examination after resection. Tumors diagnosed as PTC and those diagnosed as fibroadenoma (TFA) were selected for this study. Collectively 39 PTC and 11 TFA nodules were included. Quantitative reverse transcriptase real-time PCR (qRT-PCR) and immunohistochemistry (IHC) were used to determine levels of mRNA and proteins of CSCM ALDH1A1, CD44, ABCG2, and Oct3/4 in both types of tumors were used. This study revealed that the expression levels of CSCM were significantly increased in PTC tissues when compared to benign tissues and the positive correlation was found between the CSCM expression levels and tumor stage, size, and gender. In conclusion, for a more precise diagnosis, we suggest these markers be included in what is currently available to characterize malignancy from what is not in thyroid cancer, as well as for the staging process of PTC.

Chronic CagA-positive Helicobacter pylori infection with MNNG stimulation synergistically induces mesenchymal and cancer stem cell-like properties in gastric mucosal epithelial cells

A CagA-positive Helicobacter pylori (H. pylori) infection can cause malignant transformation of human gastric mucosal epithelial cells, and N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) is a chemical carcinogen that induces gastric carcinogenesis. Whether this environmental chemocarcinogen may synergistically enhance the risk of H. pylori-infected gastric cancer remains unclear. In this study, we adopted a chronic CagA-positive H. pylori infection with or without MNNG coinduction to establish a cellular model in GES-1 cells and an animal model in C57BL/6J mice. The proliferation, cell phenotype, apoptosis, epithelial-mesenchymal transition (EMT), stemness and tumorigenicity of gastric mucosal epithelial cells were analyzed in vitro and in vivo. The results showed that chronic H. pylori-infected GES-1 cells displayed inhibited apoptosis, abnormal proliferation, enhanced invasion, and migration, increased EMT/mesenchymal phenotype, colony formation and stem cell-like properties, and enhanced tumorsphere-formatting efficiency as well as CD44 expression, a known gastric cancer stem cell (CSC) marker. MNNG synergistically promoted the above actions of chronic H. pylori infection. Further studies in chronic H. pylori-infected C57BL/6J mice models showed that an increased incidence of premalignant lesions in the gastric mucosa tissue of the H. pylori-infected mice had occurred, the mouse gastric mucosa cells exhibited similar mesenchymal and CSC-like properties in the above GES-1 cells, and precancerous lesions and EMT/CSC-like phenotypes were reinforced by the synergistic action of MNNG stimulation. H. pylori infection and/or MNNG induction were capable of causing enhanced expression and activation of Wnt2 and β-catenin, indicating that the Wnt/β-catenin pathway is involved in the actions of H. pylori and MNNG. Taken together, these findings suggest that chronic CagA-positive H. pylori infection with MNNG stimulation synergistically induces mesenchymal and CSC-like properties of gastric mucosal epithelial cells.

The most reliable surface marker for the identification of colorectal cancer stem-like cells: A systematic review and meta-analysis

Several surface markers have been proposed for the identification and characterization of colorectal cancer stem-like cells (CR-CSLCs). However, their reliability in CR-CSLCs identification remains controversial. This study evaluated the correlation between all candidate surface marker's expression and CSLCs properties (tumorigenicity) through monitoring in vivo tumor incidence and final tumor volume. PubMed, Web of Science, and Scopus databases were systematically searched until November 2017. A total of 27 studies were found that met the inclusion criteria for cluster of differentiation 133 (CD133) and CD44 markers. Results indicated that either CD133 or CD44 positive cells caused about twofold increase in tumor volume compared with the negative cells (p < 0.05). In two groups of cells derived from primary tumors and cell lines, CD133 + cells had 25 and 1.45 times higher tumor incidence potential than CD133 - cells, respectively ( p < 0.05). Also, cohort evaluation showed that CD133 overexpression at protein level is a marker of poor overall survival in colorectal cancer (CRC) patients. While CD44 + cells displayed twofold tumorigenicity compared with the negative cells ( p < 0.05), combination of CD44 and CD133 showed about sevenfold tumorigenicity potential ( p < 0.05). In conclusion, the present meta-analysis suggests that CD133 is a robust biomarker to identify primary tumor CSLCs and can be proposed as a prognostic marker of CRC patient whereas it should be used with caution in cell lines. It seems to be more reliable to use CD133 in combination with CD44 as target biomarkers for the isolation of CR-CSLCs in both cell line and primary tumor cells populations.

LncRNA MIR4435-2HG predicts poor prognosis in patients with colorectal cancer

BACKGROUND

LncRNA MIR4435-2HG is observed in a variety of cancers, while its role in colorectal cancer is unknown. We aimed to demonstrate the relationship between MIR4435-2HG and colorectal cancer based on The Cancer Genome Atlas (TCGA) database.

MATERIALS AND METHODS

Patients with colorectal cancer were collected from TCGA. We compared the expression of MIR4435-2HG in colorectal cancer and normal tissues with Wilcoxon rank sum test, and logistic regression was used to evaluate the relationship between MIR4435-2HG and clinicopathological characters. Moreover, Kaplan-Meier and Cox regression was performed to evaluate the correlation between MIR4435-2HG and survival rate. Gene set enrichment analysis (GSEA) was also conducted to annotate biological function of MIR4435-2HG.

RESULTS

MIR4435-2HG level was elevated in colorectal cancer tissues. Increased level of MIR4435-2HG was significantly correlated with TNM stage (OR = 1.66 for T1/T2 vs. T3/T4; OR = 1.68 for N0 vs. N1/N2), stage (OR = 1.66 for stage 1/2 vs. stage 3/4), and carcinoembryonic antigen level before treatment (OR = 1.70 for <5 vs. ≥5) (all P-value <0.05). High MIR4435-2HG expression had a poorer progression-free survival (p = 0.048), and overall survival (OS) (P = 0.028), which were validated in the GSE92921 and GSE29621 datasets. MIR4435-2HG expression (P = 0.040, HR = 1.955 (95% CI [1.031-3.710])) was independently correlated with OS. GSEA demonstrated that the P38/MAPK pathway, the VEGF pathway, the cell adhesion molecules cams, the NOD-like receptor signaling pathway, the cell surface interactions at the vascular wall, and integrin cell surface interactions were differentially enriched in MIR4435-2HG high expression phenotype.

CONCLUSIONS

Increased MIR4435-2HG might be a potential biomarker for the diagnosis and prognosis of colorectal cancer. Moreover, MIR4435-2HG might participate in the development of colorectal cancer via the P38/MAPK and VEGF pathway.

Circulating and disseminated tumor cells: diagnostic tools and therapeutic targets in motion

Enumeration of circulating tumor cells (CTCs) in peripheral blood with the gold standard CellSearchTM has proven prognostic value for tumor recurrence and progression of metastatic disease. Therefore, the further molecular characterization of isolated CTCs might have clinical relevance as liquid biopsy for therapeutic decision-making and to monitor disease progression. The direct analysis of systemic cancer appears particularly important in view of the known disparity in expression of therapeutic targets as well as epithelial-to-mesenchymal transition (EMT)-based heterogeneity between primary and systemic tumor cells, which all substantially complicate monitoring and therapeutic targeting at present. Since CTCs are the potential precursor cells of metastasis, their in-depth molecular profiling should also provide a useful resource for target discovery. The present review will discuss the use of systemically spread cancer cells as liquid biopsy and focus on potential target antigens.

CBP501 suppresses macrophage induced cancer stem cell like features and metastases

CBP501 is an anti-cancer drug candidate which has been shown to increase cis-diamminedichloro-platinum (II) (CDDP) uptake into cancer cell through calmodulin (CaM) inhibition. However, the effects of CBP501 on the cells in the tumor microenvironment have not been addressed. Here, we investigated new aspects of the potential anti-tumor mechanism of action of CBP501 by examining its effects on the macrophages. Macrophages contribute to cancer-related inflammation and sequential production of cytokines such as IL-6 and TNF-α which cause various biological processes that promote tumor initiation, growth and metastasis (1). These processes include the epithelial to mesenchymal transition (EMT) and cancer stem cell (CSC) formation, which are well-known, key events for metastasis. The present work demonstrates that CBP501 suppresses lipopolysaccharide (LPS)-induced production of IL-6, IL-10 and TNF-α by macrophages. CBP501 also suppressed formation of the tumor spheroids by culturing with conditioned medium from the LPS-stimulated macrophage cell line RAW264.7. Moreover, CBP501 suppressed expression of ABCG2, a marker for CSCs, by inhibiting the interaction between cancer cells expressing VCAM-1 and macrophages expressing VLA-4. Consistently with these results, CBP501 in vivo suppressed metastases of a tumor cell line, 4T1, one which is insensitive to combination treatment of CBP501 and CDDP in vitro. Taken together, these results offer potential new, unanticipated advantages of CBP501 treatment in anti-tumor therapy through a mechanism that entails the suppression of interactions between macrophages and cancer cells with suppression of sequential CSC-like cell formation in the tumor microenvironment.

Human mesenchymal stem cells preferentially migrate toward highly oncogenic human hepatocellular carcinoma cells with activated EpCAM signaling

The epithelial cell adhesion molecule (EpCAM) is a type I transmembrane glycoprotein that is regarded as one of the markers for tumor initiating cells (TIC) in human hepatocellular carcinoma (HCC). Much work has been directed towards targeting these TICs as a mean of placing these master regulators of cell proliferation and drug resistance under control. Human bone marrow-derived mesenchymal stem cells are known to exhibit an innate property of tumor tropism. However, the possible relationship between MSC and TIC is not well understood. In this study, we show that MSC migration to HCC can be effectively inhibited by TACE and γ-secretase inhibitors that stop the activation of EpCAM signaling event. Silencing of EpCAM expression through siRNA and antibody approaches also resulted in impaired MSC migration. By contrast, increase levels of EpICD proteins in HCC cells and HCC mouse xenografts resulted in enhanced MSC migration. Taken together, these findings show that MSC is drawn to the more oncogenic population of HCC, and could potentially serve as a cell-based carrier of therapeutic genes to target EpICD-enriched hepatic tumor cells.

ALDH1 and podoplanin expression patterns predict the risk of malignant transformation in oral leukoplakia

Oral leukoplakia (OL) is a clinically diagnosed preneoplastic lesion of the oral cavity with an increased oral cancer risk. However, the risk of malignant transformation is still difficult to assess. The objective of the present study was to examine the expression patterns of aldehyde dehydrogenase 1 (ALDH1) and podoplanin in OL, and to determine their roles in predicting oral cancer development. In the present study, the expression patterns of ALDH1 and podoplanin were determined in samples from 79 patients with OL. The association between protein expression and clinicopathological parameters, including oral cancer-free survival, was analyzed during a mean follow-up period of 3.4 years. Expression of ALDH1 and podoplanin was observed in 61 and 67% patients, respectively. Kaplan-Meier analysis demonstrated that the expression of the proteins was correlated with the risk of progression to oral cancer. Multivariate analysis revealed that expression of ALDH1 and podoplanin was associated with 3.02- and 2.62-fold increased risk of malignant transformation, respectively. The malignant transformation risk of OL was considerably higher in cases with expression of both proteins. Point-prevalence analysis revealed that 66% of patients with co-expression of ALDH1 and podoplanin developed oral cancer. Taken together, our data indicate that ALDH1 and podoplanin expression patterns in OL are associated with oral cancer development, suggesting that ALDH1 and podoplanin may be useful biomarkers to identify OL patients with a substantially high oral cancer risk.

Pancreatic cancer stem cell markers and exosomes - the incentive push

Pancreatic cancer (PaCa) has the highest death rate and incidence is increasing. Poor prognosis is due to late diagnosis and early metastatic spread, which is ascribed to a minor population of so called cancer stem cells (CSC) within the mass of the primary tumor. CSC are defined by biological features, which they share with adult stem cells like longevity, rare cell division, the capacity for self renewal, differentiation, drug resistance and the requirement for a niche. CSC can also be identified by sets of markers, which for pancreatic CSC (Pa-CSC) include CD44v6, c-Met, Tspan8, alpha6beta4, CXCR4, CD133, EpCAM and claudin7. The functional relevance of CSC markers is still disputed. We hypothesize that Pa-CSC markers play a decisive role in tumor progression. This is fostered by the location in glycolipid-enriched membrane domains, which function as signaling platform and support connectivity of the individual Pa-CSC markers. Outside-in signaling supports apoptosis resistance, stem cell gene expression and tumor suppressor gene repression as well as miRNA transcription and silencing. Pa-CSC markers also contribute to motility and invasiveness. By ligand binding host cells are triggered towards creating a milieu supporting Pa-CSC maintenance. Furthermore, CSC markers contribute to the generation, loading and delivery of exosomes, whereby CSC gain the capacity for a cell-cell contact independent crosstalk with the host and neighboring non-CSC. This allows Pa-CSC exosomes (TEX) to reprogram neighboring non-CSC towards epithelial mesenchymal transition and to stimulate host cells towards preparing a niche for metastasizing tumor cells. Finally, TEX communicate with the matrix to support tumor cell motility, invasion and homing. We will discuss the possibility that CSC markers are the initial trigger for these processes and what is the special contribution of CSC-TEX.

Palmitoylated claudin7 captured in glycolipid-enriched membrane microdomains promotes metastasis via associated transmembrane and cytosolic molecules

In epithelial cells claudin7 (cld7) is a major component of tight junctions, but is also recovered from glycolipid-enriched membrane microdomains (GEM). In tumor cells, too, cld7 exists in two stages. Only GEM-located cld7, which is palmitoylated, promotes metastasis. Searching for the underlying mechanism(s) revealed the following.The metastatic capacity of the rat pancreatic adenocarcinoma cell line ASML is lost by a knockdown (kd) of cld7 and is not regained by rescuing cld7 with a mutated palmitoylation site (cld7mPalm). ASML-cld7kd and ASML-cld7mPalm cells show reduced motility and invasiveness. This is due to cld7, but not cld7mPalm associating with α6β4, ezrin, uPAR and MMP14, which jointly support motility and invasion. Palmitoylated cld7 also is engaged in drug resistance by repressing Pten, allowing activation of the antiapoptotic PI3K/Akt pathway. An association of cld7mPalm with the major Pten phosphorylating kinases does not restore apoptosis resistance as phosphorylated Pten is not guided towards GEM to compete with non-phosphorylated Pten. The pathway whereby palmitoylated cld7 supports expression of several EMT genes and nuclear translocation of EMT transcription factors remains to be unraveled. An association with Notch, reduced in ASML-cld7mPalm cells, might be the starting point. Finally, GEM-located, palmitoylated cld7 associates with several components of vesicle transport machineries engaged in exosome biogenesis.Taken together, prerequisites for cld7 acting as a cancer-initiating cell marker are GEM location and palmitoylation, which support a multitude of associations and integration into exosomes. The latter suggests palmitoylated cld7 contributing to message transfer via exosomes.

Near infrared fluorescent nanoparticles based on hyaluronic acid: Self-assembly, optical properties, and cell interaction

Fluorescent imaging agents that can specifically highlight tumor cells could have a significant impact on image-guided tumor removal. Here, fluorescent nanoparticles (NPs) derived from hyaluronic acid (HA) are investigated. HA is a ligand for the receptor CD44, which is a common biomarker present on many primary tumor cells, cancer-initiating cells, and tumor-associated fibroblasts. In addition, a family of enzymes that degrade HA, called hyaluronidases (HYALs), are also overexpressed with increased activity in many tumors. We report the design and development of a panel of targeted imaging agents using the near-infrared (NIR) dye, Cy7.5, that was directly conjugated to hydrophobically-modified HA. Two different molecular weights of HA, 10kDa and 100kDa, and three different degrees of hydrophobic moiety conjugation (0, 10, and 30mol%) were utilized to develop a panel of NPs with variable size that ranged from 50 to 400nm hydrodynamic diameter (HD) depending HA molecular weight, extent of fluorescence quenching (25-50%), kinetics of cellular uptake, and targeting to CD44+ cells. The kinetics and energy-dependence of cellular uptake in breast and prostate cancer cell lines, MDA-MB 231 and PC-3 cells, respectively, showed increased uptake with longer incubation times (at 4 and 8h compared to 1h), as well as uptake at 37°C but not 4°C, which indicated energy-dependent endocytosis. NP uptake studies in the presence of excess free HA showed that pre-treatment of cells with excess high molecular weight (MW) free HA decreased NP uptake by up to 50%, while no such trend was observed with low MW HA. These data lay the foundation for selection of optimized HA-derived NPs for image-guided surgery.

STATEMENT OF SIGNIFICANCE

Here, hyaluronic acid (HA), a well-studied biomacromolecule, is modified with a near infrared fluorophore and a hydrophobic moiety. The significance of this work, especially for imaging applications, is that the impact of HA molecular weight and the hydrophobic moiety conjugation degree on fluorescence and cell interaction can be predicted. With respect to existing literature, the eventual use of these HA-based NPs is image-guided surgery; thus, we focus on the dye, Cy7.5, for conjugation, which is more NIR than most existing HA literature. Furthermore, HA is a ligand for CD44, which is associated with cancer and tumor microenvironment cells. Systematic studies in this work highlight that HA can be tuned to maximize or minimize CD44 binding.

Interplay between Cellular and Molecular Inflammatory Mediators in Lung Cancer

Inflammation is a component of the tumor microenvironment and represents the 7th hallmark of cancer. Chronic inflammation plays a critical role in tumorigenesis. Tumor infiltrating inflammatory cells mediate processes associated with progression, immune suppression, promotion of neoangiogenesis and lymphangiogenesis, remodeling of extracellular matrix, invasion and metastasis, and, lastly, the inhibition of vaccine-induced antitumor T cell response. Accumulating evidence indicates a critical role of myeloid cells in the pathophysiology of human cancers. In contrast to the well-characterized tumor-associated macrophages (TAMs), the significance of granulocytes in cancer has only recently begun to emerge with the characterization of tumor-associated neutrophils (TANs). Recent studies show the importance of CD47 in the interaction with macrophages inhibiting phagocytosis and promoting the migration of neutrophils, increasing inflammation which can lead to recurrence and progression in lung cancer. Currently, therapies are targeted towards blocking CD47 and enhancing macrophage-mediated phagocytosis. However, antibody-based therapies may have adverse effects that limit its use.

Sonic hedgehog in oral squamous cell carcinoma: An immunohistochemical study

BACKGROUND

Recent studies have revealed the involvement of hedgehog (Hh) signaling component in proliferation and invasive behavior of many carcinomas.

AIM

This study aims to identify the expression of sonic Hh (SHH) protein of SHH pathway in oral epithelial dysplasia and oral squamous cell carcinoma (OSCC) using SHH (H-160) (Santa Cruz, sc-9042) which could have therapeutic implication in future.

MATERIALS AND METHODS

A total of 250 cases comprising 50 normal oral mucosa, 50 cases of oral epithelial dysplasia, 50 well, 50 moderate and 50 poorly differentiated OSCCs were included in the study. Immunohistochemical evaluation of SHH protein expression was conducted using monoclonal antibody. Interpretation of the expression was done by immunoreactive score of Remmele and Stegner (IRS) scoring method.

STATISTICAL ANALYSIS

Chi-Square test was used to analyze the results.

RESULTS

The study showed that SHH signaling molecules are highly expressed in OSCC, and their expression was mainly in the cytoplasm of epithelial cells.

CONCLUSION

The SHH signaling component is associated with the pathological parameter in OSCC and oral epithelial dysplasia.

Adamantinomatous craniopharyngiomas express tumor stem cell markers in cells with activated Wnt signaling: further evidence for the existence of a tumor stem cell niche?

INTRODUCTION

Early disease onset, clinical manifestation, histomorphology, and increased tendency to relapse distinguish the adamantinomatous craniopharyngioma (adaCP) from the more favorable papillary variant (papCP). A molecular hallmark of adaCP is the activated Wnt signaling pathway indicated by nuclear β-catenin accumulation in a subset of tumor cells. A mouse model recently illustrated that these cells are the driving force in tumorigenesis of adaCP. This observation and the peculiar growth pattern points to the existence of a specific tumor stem cell (TSC) population in human CP.

MATERIALS AND METHODS

To prove this hypothesis, the TSC markers CD133 (Prominin1) and CD44 were examined in papCP (n = 8) and adaCP (n = 25) on mRNA level using quantitative real time PCR of total tumor RNA. Furthermore, we investigated protein expression performing immunohistochemical analyses of formalin-fixed paraffin embedded tumor samples.

RESULTS

PapCP revealed a homogenous CD44 expression pattern predominantly at the cell membrane, whereas CD133 labeling was hardly detectable. In adaCP, on the other hand all markers were consistently and predominantly co-expressed in nuclear β-catenin accumulating cell clusters, which was confirmed by double immunofluorescence staining. Overall expression of CD44 was significantly decreased in adaCP versus papCP, whereas CD133 showed significantly higher protein and mRNA levels in adaCP.

CONCLUSIONS

Our results indicate tumor stem cell-like characteristics of β-catenin accumulating cell clusters in adaCP, which may represent a tumor stem cell niche and might contribute to tumor recurrence. The potential impact of these special cell groups in regard to future CP management, including postoperative follow-up and additional treatment remains to be explored.

Influence of interferon-α on the expression of the cancer stem cell markers in pancreatic carcinoma cells

The cytokine interferon-α (IFNα) belongs to the group of type I interferons already used in cancer therapy. This drug possesses radio- and chemo-sensitizing, and shows anti-angiogenic properties. Cancer stem cells (CSC) are a unique population of tumor cells that initiate secondary tumors, and are responsible for metastasis formation. Patients with pancreatic ductal adenocarcinoma (PDAC) have an especially poor prognosis, with 5-year survival rates of only ~1% and median survival of 4-6 months. PDAC is characterized by the presence of CSC. In this work we demonstrate for the first time that IFNα up-regulates the expression of the CSC markers CD24, CD44 and CD133 in in vitro and in vivo models of PDAC. We showed the IFNα effects on the migration and invasion of PDAC cells, which is associated with the level of the CSC marker expression. In vivo, this drug inhibits tumor growth but promotes metastasis formation in the early stage of tumor growth. We propose that IFNα may enhance the enrichment of CSC in PDAC tumors. Additionally we also suggest that in combination therapy of solid tumors with IFNα, this drug should be given to patients prior to chemotherapy to achieve the CSC activation.

EPCAM deletion carriers constitute a unique subgroup of Lynch syndrome patients

Lynch syndrome, one of the most common cancer susceptibility syndromes, is caused by germline mutations of genes affecting the mismatch repair proteins MLH1, MSH2, MSH6 or PMS2. Most of these mutations disrupt the open reading frame of the genes involved and, as such, lead to constitutive inactivation of the mutated allele. In a subset of Lynch syndrome patients MSH2 was found to be specifically inactivated in cell lineages exhibiting EPCAM expression. These patients carry deletions of the 3' end of the EPCAM gene, including its polyadenylation signal. Due to concomitant transcriptional read-through of EPCAM, the promoter of MSH2 15 kb further downstream becomes inactivated through hypermethylation. As these 3' EPCAM deletions occur in the germline, this MSH2 promoter methylation ('epimutation') is heritable. Worldwide, numerous EPCAM 3' end deletions that differ in size and location have been detected. The risk of colorectal cancer in carriers of such EPCAM deletions is comparable to that of MSH2 mutation carriers, and is in accordance with a high expression of EPCAM in colorectal cancer stem cells. The risk of endometrial cancer in the entire group of EPCAM deletion carriers is significantly lower than that in MSH2 mutation carriers, but the actual risk appears to be dependent on the size and location of the EPCAM deletion. These observations may have important implications for the surveillance of EPCAM deletion carriers and, thus, calls for an in-depth assessment of clinically relevant genotype-phenotype correlations and its underlying molecular mechanism(s).

p53 orchestrates between normal differentiation and cancer

During recent years, it is becoming more and more evident that there is a tight connection between abnormal differentiation processes and cancer. While cancer and stem cells are very different, especially in terms of maintaining genomic integrity, these cell types also share many similar properties. In this review, we aim to provide an over-view of the roles of the key tumor suppressor, p53, in regulating normal differentiation and function of both stem cells and adult cells. When these functions are disrupted, undifferentiated cells may become transformed. Understanding the function of p53 in stem cells and its role in maintaining the balance between differentiation and malignant transformation can help shed light on cancer initiation and propagation, and hopefully also on cancer prevention and therapy.

Multidrug resistance and cancer stem cells in neuroblastoma and hepatoblastoma

Chemotherapy is one of the major modalities in treating cancers. However, its effectiveness is limited by the acquisition of multidrug resistance (MDR). Several mechanisms could explain the up-regulation of MDR genes/proteins in cancer after chemotherapy. It is known that cancer stem cells (CSCs) play a role as master regulators. Therefore, understanding the mechanisms that regulate some traits of CSCs may help design efficient strategies to overcome chemoresistance. Different CSC phenotypes have been identified, including those found in some pediatric malignancies. As solid tumors in children significantly differ from those observed in adults, this review aims at providing an overview of the mechanistic relationship between MDR and CSCs in common solid tumors, and, in particular, focuses on clinical as well as experimental evidence of the relations between CSCs and MDR in neuroblastoma and hepatoblastoma. Finally, some novel approaches, such as concomitant targeting of multiple key transcription factors governing the stemness of CSCs, as well as nanoparticle-based approaches will also be briefly addressed.

Clinicopathologic implications of EpCAM and Sox2 expression in breast cancer

BACKGROUND

The purpose of this study was to investigate the clinicopathologic significance of EpCAM and Sox2 expression in breast cancer and to study their correlation during breast cancer progression.

PATIENTS AND METHODS

EpCAm and Sox2 expression were assessed using immunohistochemistry in ductal carcinoma insitu (DCIS), invasive breast cancer (IBC) and matched lymph node metastasis (LNM), if present.

RESULTS

EpCAM overexpression was found in 63.2% of DCIS, 72.2% of IBC and 74.4% of LNM. In IBC cases, EpCAM overexpression was associated with high grade (P < .001), large tumor size (P = .051), poor Nottingham Prognostic Index (NPI) (P = .006), histological tumor types (P = .044) and the triple negative phenotype (P = .008). LNM frequently reflected the expression phenotype of the matched primary tumors with no significant differences between LNM and their primary tumors (P = .564). Sox2 expression was detected in 47.4%, 33.3% and 54.7% of DCIS, IBC and LNM respectively. In DCIS group, Sox2 expression was significantly associated with comedo type (P = .037), negative ER (P = .012) and PR (P = .037) and the triple negative phenotype (P = .006). In IBC cases, Sox2 expression showed significant associations with high grade (P = .045), nodal spread (P = .037), poor NPI (P = .018) and the triple negative phenotype (P < .001). LNM showed significantly higher Sox2 expression rates than primary tumors (P < .001). Significant positive associations between EpCAM overexpression and Sox2 positivity in DCIS (P = .027), IBC (P = .001) and LNM (P < .001) were found.

CONCLUSION

This study emphasized the potential role of EpCAM and Sox2 in breast carcinogenesis and revealed their involvement during breast cancer progression and LN metastases.

Colorectal adenoma stem-like cell populations: associations with adenoma characteristics and metachronous colorectal neoplasia

Cancer stem cells have tumor-initiation and tumor-maintenance capabilities. Stem-like cells are present in colorectal adenomas, but their relationship to adenoma pathology and patient characteristics, including metachronous development of an additional adenoma ("recurrence"), has not been studied extensively. We evaluated the expression of aldehyde dehydrogenase isoform 1A1 (ALDH1A1), a putative stem cell marker, in baseline adenomas from the placebo arm of chemoprevention trial participants with colonoscopic follow-up. An exploratory set of 20 baseline adenomas was analyzed by ALDH1A1 immunohistochemistry with morphometry, and a replication set of 89 adenomas from 76 high-risk participants was evaluated by computerized image analysis. ALDH1A1-labeling indices (ALI) were similar across patient characteristics and in advanced and nonadvanced adenomas. There was a trend toward higher ALIs in adenomas occurring in the right than left colon (P = 0.09). ALIs of synchronous adenomas were correlated (intraclass correlation coefficient 0.67). Participants in both sample sets who developed a metachronous adenoma had significantly higher ALIs in their baseline adenoma than participants who remained adenoma free. In the replication set, the adjusted odds for metachronous adenoma increased 1.46 for each 10% increase in ALIs (P = 0.03). A best-fit algorithm-based cutoff point of 22.4% had specificity of 75.0% and positive predictive value of 70.0% for metachronous adenoma development. A larger population of ALDH1A1-expressing cells in an adenoma is associated with a higher risk for metachronous adenoma, independent of adenoma size or histopathology. If confirmed, ALDH1A1 has potential as a novel biomarker in risk assessment and as a potential stem cell target for chemoprevention.

Wnt/β-catenin signalling induces MLL to create epigenetic changes in salivary gland tumours

We show that activation of Wnt/β-catenin and attenuation of Bmp signals, by combined gain- and loss-of-function mutations of β-catenin and Bmpr1a, respectively, results in rapidly growing, aggressive squamous cell carcinomas (SCC) in the salivary glands of mice. Tumours contain transplantable and hyperproliferative tumour propagating cells, which can be enriched by fluorescence activated cell sorting (FACS). Single mutations stimulate stem cells, but tumours are not formed. We show that β-catenin, CBP and Mll promote self-renewal and H3K4 tri-methylation in tumour propagating cells. Blocking β-catenin-CBP interaction with the small molecule ICG-001 and small-interfering RNAs against β-catenin, CBP or Mll abrogate hyperproliferation and H3K4 tri-methylation, and induce differentiation of cultured tumour propagating cells into acini-like structures. ICG-001 decreases H3K4me3 at promoters of stem cell-associated genes in vitro and reduces tumour growth in vivo. Remarkably, high Wnt/β-catenin and low Bmp signalling also characterize human salivary gland SCC and head and neck SCC in general. Our work defines mechanisms by which β-catenin signals remodel chromatin and control induction and maintenance of tumour propagating cells. Further, it supports new strategies for the therapy of solid tumours.

A common MicroRNA signature consisting of miR-133a, miR-139-3p, and miR-142-3p clusters bladder carcinoma in situ with normal umbrella cells

miRNAs are small noncoding RNAs with critical roles in a large variety of biological processes such as development and tumorigenesis. miRNA expression profiling has been reported to be a powerful tool to classify tissue samples, including cancers, based on their developmental lineage. In this study, we have profiled the expression of miRNAs in bladder carcinoma in situ (CIS) and distinct cell compartments of the normal bladder, namely umbrella and basal-intermediate urothelial cells, as well as the muscularis propria. We identified several miRNAs differentially expressed between umbrella and basal-intermediate cells (miR-133a, miR-139-3p, miR-142-3p, miR-199b-5p, and miR-221). In situ hybridization confirmed the expression of miR-133a and miR-139-3p in umbrella cells, and miR-142-3p in basal-intermediate cells. Strikingly, miRNA expression levels of CIS most closely resembled the miRNA profile of umbrella cells. Finally, we examined well-established umbrella and basal-intermediate cell immunohistochemical biomarkers in an independent series of CIS samples. Again, this analysis revealed the significant expression of umbrella-specific markers in CIS when compared to non-CIS lesions. Overall, our studies represent a comprehensive and accurate description of the different miRNAs expressed in CIS tumors and three distinct histological areas of the urinary bladder. Notably, this study provides evidence of the possible origin relationship between CIS and normal umbrella cells.

CD133 in the selection of epidermal stem cells in mice: steps in the right direction

Charruyer and colleagues (this issue) report two significant advances to the field of cutaneous keratinocyte stem cells: a pair of new selectable markers that recognize a subset of α6(+)CD34(+) label-retaining cells, and an in vivo limiting dilution assay for keratinocyte stem cells with long-term repopulating ability. This work has important implications for keratinocyte stem cell identification and assay, as well as for the identification of target cells in non-melanoma skin cancer.

MMP7 is a target of the tumour-associated antigen EpCAM

Epithelial cell adhesion molecule (EpCAM) is a single-transmembrane protein, which is involved in numerous cellular processes including cell adhesion, proliferation, maintenance of stemness of embryonic cells and progenitors, migration and invasion. Activation of signal transduction by EpCAM is warranted by regulated intramembrane proteolysis and nuclear translocation of the intracellular domain EpICD. Here, we describe matrix metalloproteinase 7 (MMP7) as a target gene of EpCAM signalling viaEpICD nuclear translocation. EpCAM and MMP7 expression pattern and levels positively correlated in vitro and in vivo, and were strongly elevated in primary carcinomas of the head and neck area. Hence, MMP7 is a novel target of EpCAM signalling.

CD133 induces tumour-initiating properties in HEK293 cells

The pentaspan protein CD133 (Prominin-1) is part of the signature of tumour-initiating cells for various cancer entities. The aim of the present study was to investigate the impact of ectopic CD133 expression on tumourigenic properties of otherwise CD133-negative, non-tumourigenic cells in vitro and in vivo. CD133 was stably transfected into human embryonic kidney 293 (HEK293) which was then sorted for the expression of CD133. The effects of CD133 on cell proliferation were assessed upon standard cell counting of sorted cells at various time points. Severe combined immunodeficient (SCID) mice (n = 30) were injected with HEK293 CD133(high) and CD133(low) transfectants (5 × 10(3), 1 × 10(5), or 5 × 10(6) cells per injection). The expression of CD133, Ki67, CD44s, CD44v6, and EpCAM was analysed upon immunohistochemical staining of cryosections with specific antibodies. In vitro, ectopic expression of CD133 did influence neither cell proliferation nor cell cycle distribution of otherwise CD133-negative HEK293 cells. However, CD133(high) cells generated tumours in vivo in SCID mice with at least 1,000-fold increased frequency compared to CD133(low) cells. Tumour load was also significantly increased in CD133(high) cells as compared to those tumours formed by high numbers of CD133(low) cells. Immunohistochemistry stainings disclosed no changes in Ki67, CD44s, CD44v6, or EpCAM once tumours were formed by either cell type. CD133 induces tumour-initiating properties in HEK293 cells in vivo and is potentially involved in the regulation of tumourigenicity. Future research will aim at the elucidation of molecular mechanisms of CD133-induced tumourigenicity.

DNA methyltransferase 1 is essential for initiation of the colon cancers

DNA methyltransferase 1 (Dnmt1) is essential for the maintenance of hematopoietic and somatic stem cells in mice; however, its roles in human cancer stem-like cells (CSCs)/cancer-initiating cells (CICs) are still elusive. In the present study, we investigated DNMT1 functions in the maintenance of human colon CSCs/CICs using the human colon cancer cell line HCT116 (HCT116 w/t) and its DNMT1 knockout cell line (DNMT1(-/-)). The rates of CSCs/CICs were evaluated by side population (SP) analysis, ALDEFLUOR assay and expression of CD44 and CD24. SP, ALDEFLUOR-positive (ALDEFLUOR(+)) and CD44-positive and CD24-positive (CD44(+)CD24(+)) cell rates were lower in DNMT1(-/-) cells than in HCT116 w/t cells. Since CSCs/CICs have higher tumor-initiating ability than that of non-CSCs/CICs, the tumor-initiating abilities were addressed by injecting immune deficient (NOD/SCID) mice. DNMT1(-/-) cells showed less tumor-initiating ability than did HCT116 w/t cells, whereas the growing rate of DNMT1(-/-) cells showed no significant difference from that of HCT116 cells both in vitro and in vivo. Similar results were obtained for cells in which DNMT1 had been transiently knocked-down using gene-specific siRNAs. Taken together, these results indicate that DNMT1 is essential for maintenance of colon CSCs/CICs and that short-term suppression of DNMT1 might be sufficient to disrupt CSCs/CICs.

Protein markers of cancer-associated fibroblasts and tumor-initiating cells reveal subpopulations in freshly isolated ovarian cancer ascites

BACKGROUND

In ovarian cancer, massive intraperitoneal dissemination is due to exfoliated tumor cells in ascites. Tumor-initiating cells (TICs or cancer stem cells) and cells showing epithelial-mesenchymal-transition (EMT) are particularly implicated. Spontaneous spherical cell aggregates are sometimes observed, but although similar to those formed by TICs in vitro, their significance is unclear.

METHODS

Cells freshly isolated from malignant ascites were separated into sphere samples (S-type samples, n=9) and monolayer-forming single-cell suspensions (M-type, n=18). Using western blot, these were then compared for expression of protein markers of EMT, TIC, and of cancer-associated fibroblasts (CAFs).

RESULTS

S-type cells differed significantly from M-type by expressing high levels of E-cadherin and no or little vimentin, integrin-β3 or stem cell transcription factor Oct-4A. By contrast, M-type samples were enriched for CD44, Oct-4A and for CAF markers. Independently of M- and S-type, there was a strong correlation between TIC markers Nanog and EpCAM. The CAF marker α-SMA correlated with clinical stage IV. This is the first report on CAF markers in malignant ascites and on SUMOylation of Oct-4A in ovarian cancer.

CONCLUSIONS

In addition to demonstrating potentially high levels of TICs in ascites, the results suggest that the S-type population is the less tumorigenic one. Nanog(high)/EpCAM(high) samples represent a TIC subset which may be either M- or S-type, and which is separate from the CD44(high)/Oct-4A(high) subset observed only in M-type samples. This demonstrates a heterogeneity in TIC populations in vivo which has practical implications for TIC isolation based on cell sorting. The biological heterogeneity will need to be addressed in future therapeutical strategies.

CD133+, CD166+CD44+, and CD24+CD44+ phenotypes fail to reliably identify cell populations with cancer stem cell functional features in established human colorectal cancer cell lines

Increasing evidence that cancers originate from small populations of so-called cancer stem cells (CSCs), capable of surviving conventional chemotherapies and regenerating the original tumor, urges the development of novel CSC-targeted treatments. Screening of new anticancer compounds is conventionally conducted on established tumor cell lines, providing sufficient material for high-throughput studies. Whether tumor cell lines might comprise CSC populations resembling those of primary tumors, however, remains highly debated. We have analyzed the expression of defined phenotypic profiles, including CD133+, CD166+CD44+, and CD24+CD44+, reported as CSC-specific in human primary colorectal cancer (CRC), on a panel of 10 established CRC cell lines and evaluated their correlation with CSC properties. None of the putative CSC phenotypes consistently correlated with stem cell-like features, including spheroid formation ability, clonogenicity, aldehyde dehydrogenase-1 activity, and side population phenotype. Importantly, CRC cells expressing putative CSC markers did not exhibit increased survival when treated with chemotherapeutic drugs in vitro or display higher tumorigenicity in vivo. Thus, the expression of CD133 or the coexpression of CD166/CD44 or CD24/CD44 did not appear to reliably identify CSC populations in established CRC cell lines. Our findings question the suitability of cell lines for the screening of CSC-specific therapies and underline the urgency of developing novel platforms for anticancer drug discovery.

Acetylation modulates the STAT signaling code

A fascinating question of modern biology is how a limited number of signaling pathways generate biological diversity and crosstalk phenomena in vivo. Well-defined posttranslational modification patterns dictate the functions and interactions of proteins. The signal transducers and activators of transcription (STATs) are physiologically important cytokine-induced transcription factors. They are targeted by a multitude of posttranslational modifications that control and modulate signaling responses and gene expression. Beyond phosphorylation of serine and tyrosine residues, lysine acetylation has recently emerged as a critical modification regulating STAT functions. Interestingly, acetylation can determine STAT signaling codes by various molecular mechanisms, including the modulation of other posttranslational modifications. Here, we provide an overview on the acetylation of STATs and how this protein modification shapes cellular cytokine responses. We summarize recent advances in understanding the impact of STAT acetylation on cell growth, apoptosis, innate immunity, inflammation, and tumorigenesis. Furthermore, we discuss how STAT acetylation can be targeted by small molecules and we consider the possibility that additional molecules controlling STAT signaling are regulated by acetylation. Our review also summarizes evolutionary aspects and we show similarities between the acetylation-dependent control of STATs and other important molecules. We propose the concept that, similar to the 'histone code', distinct posttranslational modifications and their crosstalk orchestrate the functions and interactions of STAT proteins.

Concise review: self-renewal in the central nervous system: neural stem cells from embryo to adult

The recent discovery of neural stem cells (NSCs) in the adult mammalian brain has fostered a plethora of translational and preclinical studies to investigate future therapeutic approaches for the cure of neurodegenerative diseases. These studies are finally at the clinical stage, and some of them are already under way. The definition of a bona fide stem cell has long been the object of much debate focused on the establishment of standard and univocal criteria to distinguish between stem and progenitor cells. It is commonly accepted that NSCs have to fulfill two basic requirements, the capacity for long-term self-renewal and the potential for differentiation, which account for their physiological role, namely central nervous system tissue homeostasis. Strategies such as immortalization or reprogramming of somatic cells to the embryonic-like stage of pluripotency indicate the relevance of extensive self-renewal ability of NSCs either in vitro or in vivo. Moreover, the discovery of stem-like tumor cells in brain tumors, such as gliomas, accompanied by the isolation of these cells through the same paradigm used for related healthy cells, has provided further evidence of the key role that self-renewal plays in the development and progression of neurodegenerative diseases and cancer. In this review we provide an overview of the current understanding of the self-renewal capacity of nontransformed human NSCs, with or without immortalization or reprogramming, and of stem-like tumor cells, referring to both research and therapeutic studies.