Cancer stem cell marker ALDH1 expression is associated with lymph node metastasis and poor survival in esophageal squamous cell carcinoma: a study from high incidence area of northern China

Potential markers of cancer stem-like cells in ESCC: a review of the current knowledge

In patients with esophageal squamous cell carcinoma (ESCC), the incidence and mortality rate of ESCC in our country are also higher than those in the rest of the world. Despite advances in the treatment department method, patient survival rates have not obviously improved, which often leads to treatment obstruction and cancer repeat. ESCC has special cells called cancer stem-like cells (CSLCs) with self-renewal and differentiation ability, which reflect the development process and prognosis of cancer. In this review, we evaluated CSLCs, which are identified from the expression of cell surface markers in ESCC. By inciting EMTs to participate in tumor migration and invasion, stem cells promote tumor redifferentiation. Some factors can inhibit the migration and invasion of ESCC via the EMT-related pathway. We here summarize the research progress on the surface markers of CSLCs, EMT pathway, and the microenvironment in the process of tumor growth. Thus, these data may be more valuable for clinical applications.

ALDEFLUOR activity, ALDH isoforms, and their clinical significance in cancers

High aldehyde dehydrogenase (ALDH) activity is a metabolic feature of adult stem cells and various cancer stem cells (CSCs). The ALDEFLUOR system is currently the most commonly used method for evaluating ALDH enzyme activity in viable cells. This system is applied extensively in the isolation of normal stem cells and CSCs from heterogeneous cell populations. For many years, ALDH1A1 has been considered the most important subtype among the 19 ALDH family members in determining ALDEFLUOR activity. However, in recent years, studies of many types of normal and tumour tissues have demonstrated that other ALDH subtypes can also significantly influence ALDEFLUOR activity. In this article, we briefly review the relationships between various members of the ALDH family and ALDEFLUOR activity. The clinical significance of these ALDH isoforms in different cancers and possible directions for future studies are also summarised.

Targeting the Retinoic Acid Pathway to Eradicate Cancer Stem Cells

All-trans retinoic acid is a morphogen during embryogenesis and a teratogen. Cancer is an error of development, and the retinoic acid receptors (RAR) for all-trans retinoic acid play a role in cancer. Expression of the cytosolic aldehyde dehydrogenases, which mediate the last step to the synthesis of all-trans retinoic acid, is deregulated in various human cancers. Inhibiting these enzymes using a variety of agents reduced the proliferation of lung cancer cells, reduced the proliferation and induced apoptosis of ovarian, prostate, squamous, and uterine cancer cells, and sensitised breast, colorectal and ovarian cancer cells to chemotherapeutic agents. RARγ is an oncogene within some cases of AML, cholangiocarcinoma, colorectal cancer, clear cell renal cell carcinoma, hepatocellular carcinoma, pancreatic ductal adenocarcinoma, prostate cancer, and ovarian cancer. Pan-RAR and RARγ antagonist inhibition of the action of RARγ led to necroptosis of human prostate and pediatric brain tumour cancer stem cells. Treatment of hepatocellular carcinoma cells with the flavenoid acacetin, which interferes with the action of RARγ, decreased cell growth and induced apoptosis. Targeting the retinoic acid pathway is promising regarding the development of new drugs to eradicate cancer stem cells.

The Concept of Cancer Stem Cells: Elaborating on ALDH1B1 as an Emerging Marker of Cancer Progression

Cancer is a multifactorial, complex disease exhibiting extraordinary phenotypic plasticity and diversity. One of the greatest challenges in cancer treatment is intratumoral heterogeneity, which obstructs the efficient eradication of the tumor. Tumor heterogeneity is often associated with the presence of cancer stem cells (CSCs), a cancer cell sub-population possessing a panel of stem-like properties, such as a self-renewal ability and multipotency potential. CSCs are associated with enhanced chemoresistance due to the enhanced efflux of chemotherapeutic agents and the existence of powerful antioxidant and DNA damage repair mechanisms. The distinctive characteristics of CSCs make them ideal targets for clinical therapeutic approaches, and the identification of efficient and specific CSCs biomarkers is of utmost importance. Aldehyde dehydrogenases (ALDHs) comprise a wide superfamily of metabolic enzymes that, over the last years, have gained increasing attention due to their association with stem-related features in a wide panel of hematopoietic malignancies and solid cancers. Aldehyde dehydrogenase 1B1 (ALDH1B1) is an isoform that has been characterized as a marker of colon cancer progression, while various studies suggest its importance in additional malignancies. Here, we review the basic concepts related to CSCs and discuss the potential role of ALDH1B1 in cancer development and its contribution to the CSC phenotype.

An anti-alcoholism drug, disulfiram and copper complex improves radio-resistance of tumor-initiating cells in esophageal squamous cell carcinoma

BACKGROUND

Esophageal squamous cell carcinoma (ESCC) is a malignant cancer with a poor prognosis. Chemoradiotherapy is one of the most important strategies for patients with locally advanced unresectable ESCC; however, its therapeutic effect is unsatisfactory. Tumor-initiating cells (TICs) have been reported to be resistant to conventional chemotherapy and radiotherapy so far. Therefore, we aimed to develop a treatment strategy targeting TICs in ESCC to improve radiosensitivity.

METHODS

First, we validated aldehyde dehydrogenase 1 (ALDH1) as a TIC marker and investigated its ability to mediate resistance in human ESCC cell lines using flow cytometry, Western blotting, and functional analyses. Then, we focused on disulfiram (DSF), an aldehyde dehydrogenase inhibitor, used to treat alcohol use disorder. We investigated the effect of DSF and copper (II) D-gluconate (Cu) on the radiosensitivity of ESCC in xenograft mouse models.

RESULTS

ALDH1-positive cells showed an upregulation of SOX2 and Nanog, exhibiting much stronger tumor-initiating properties than ALDH1-negative cells. Furthermore, inhibition of ALDH1 attenuated the tumor-initiating properties of ESCC cell lines. Our results also showed that ALDH1-positive cells were resistant to chemotherapy and radiotherapy, and the inhibition of ALDH1 led to the mitigation of therapeutic resistance. Our in vitro and in vivo studies revealed that the DSF/Cu complex could radiosensitize ALDH1-positive ESCC cells and downregulate the phosphoinositide 3-kinase/Akt pathway.

CONCLUSION

ALDH1 inhibition by the DSF/Cu complex enhances the radiosensitivity of TICs in ESCC. The drug repositioning approach using disulfiram is a potential treatment option to overcome radioresistance in patients with locally advanced ESCC.

Oral Cancer Stem Cells: Therapeutic Implications and Challenges

Head and neck squamous cell carcinoma (HNSCC) is currently one of the 10 most common malignancies worldwide, characterized by a biologically highly diverse group of tumors with non-specific biomarkers and poor prognosis. The incidence rate of HNSCC varies widely throughout the world, with an evident prevalence in developing countries such as those in Southeast Asia and Southern Africa. Tumor relapse and metastasis following traditional treatment remain major clinical problems in oral cancer management. Current evidence suggests that therapeutic resistance and metastasis of cancer are mainly driven by a unique subpopulation of tumor cells, termed cancer stem cells (CSCs), or cancer-initiating cells (CICs), which are characterized by their capacity for self-renewal, maintenance of stemness and increased tumorigenicity. Thus, more understanding of the molecular mechanisms of CSCs and their behavior may help in developing effective therapeutic interventions that inhibit tumor growth and progression. This review provides an overview of the main signaling cascades in CSCs that drive tumor repropagation and metastasis in oral cancer, with a focus on squamous cell carcinoma. Other oral non-SCC tumors, including melanoma and malignant salivary gland tumors, will also be considered. In addition, this review discusses some of the CSC-targeted therapeutic strategies that have been employed to combat disease progression, and the challenges of targeting CSCs, with the aim of improving the clinical outcomes for patients with oral malignancies. Targeting of CSCs in head and neck cancer (HNC) represents a promising approach to improve disease outcome. Some CSC-targeted therapies have already been proven to be successful in pre-clinical studies and they are now being tested in clinical trials, mainly in combination with conventional treatment regimens. However, some studies revealed that CSCs may not be the only players that control disease relapse and progression of HNC. Further, clinical research studying a combination of therapies targeted against head and neck CSCs may provide significant advances.

Weighted Correlation Network Analysis of Cancer Stem Cell-Related Prognostic Biomarkers in Esophageal Squamous Cell Carcinoma

Background: The role of cancer stem cells in esophageal squamous cell carcinoma (ESCC) remains unclear. Methods: The mRNA stemness index (mRNAsi) of 179 ESCC patients (GSE53625) was calculated using a machine learning algorithm based on their mRNA expression. Stemness-related genes were identified by weighted correlation network analysis (WGCNA) and LASSO regression, whose associations with mutation status, immune cell infiltrations, and potential compounds were also analyzed. The role of these genes in proliferation and their expressions was assessed in ESCC cell lines and 112 samples from our center. Results: The ESCC samples had significantly higher mRNAsi than the normal tissues. Patients with high mRNAsi exhibited higher worse OS. Seven stemness-related genes were identified by WGCNA and LASSO regression, based on which a risk-predicted score model was constructed. Among them, CST1, CILP, PITX2, F2RL2, and RIOX1 were favorable for OS, which were adverse for DPP4 and ZFHX4 in the GSE53625 dataset. However, RIOX1 was unfavorable for OS in patients from our center. In vitro assays showed that CST1, CILP, PITX2, F2RL2, and RIOX1 were pro-proliferated, which were opposite for DDP4 and ZFHX4. In addition, SMARCA4, NOTCH3, DNAH5, and KALRN were more mutated in the low-score group. The low-score group had significantly more memory B cells, monocytes, activated NK cells, and Tregs and less macrophages M2, resting mast cells, and resting dendritic cells. Conclusions: Seven stemness-related genes are significantly related to the prognosis, gene mutations, and immune cell infiltration of ESCC. Some potential anticancer compounds may be favorable for OS.

Molecular subclassification of gastrointestinal cancers based on cancer stem cell traits

Human gastrointestinal malignancies are highly heterogeneous cancers. Clinically, heterogeneity largely contributes to tumor progression and resistance to therapy. Heterogeneity within gastrointestinal cancers is defined by molecular subtypes in genomic and transcriptomic analyses. Cancer stem cells (CSCs) have been demonstrated to be a major source of tumor heterogeneity; therefore, assessing tumor heterogeneity by CSC trait-guided classification of gastrointestinal cancers is essential for the development of effective therapies. CSCs share critical features with embryonic stem cells (ESCs). Molecular investigations have revealed that embryonic genes and developmental signaling pathways regulating the properties of ESCs or cell lineage differentiation are abnormally active and might be oncofetal drivers in certain tumor subtypes. Currently, multiple strategies allow comprehensive identification of tumor subtype-specific oncofetal signatures and evaluation of subtype-specific therapies. In this review, we summarize current knowledge concerning the molecular classification of gastrointestinal malignancies based on CSC features and elucidate their clinical relevance. We also outline strategies for molecular subtype identification and subtype-based therapies. Finally, we explore how clinical implementation of tumor classification by CSC subtype might facilitate the development of more effective personalized therapies for gastrointestinal cancers.

ALDH1 expression predicts progression of premalignant lesions to cancer in Type I endometrial carcinomas

In type 1 endometrial cancer, unopposed estrogen stimulation is thought to lead to endometrial hyperplasia which precedes malignant progression. Recent data from our group and others suggest that ALDH activity mediates stemness in endometrial cancer, but while aldehyde dehydrogenase 1 (ALDH1) has been suggested as a putative cancer stem cell marker in several cancer types, its clinical and prognostic value in endometrial cancer remains debated. The aim of this study was to investigate the clinical value of ALDH1 expression in endometrial hyperplasia and to determine its ability to predict progression to endometrial cancer. Interrogation of the TCGA database revealed upregulation of several isoforms in endometrial cancer, of which the ALDH1 isoforms collectively constituted the largest group. To translate its expression, a tissue microarray was previously constructed which contained a wide sampling of benign and malignant endometrial samples. The array contained a metachronous cohort of samples from individuals who either developed or did not develop endometrial cancer. Immunohistochemical staining was used to determine the intensity and frequency of ALDH1 expression. While benign proliferative and secretory endometrium showed very low levels of ALDH1, slightly higher expression was observed within the stratum basalis. In disease progression, cytoplasmic ALDH1 expression showed a step-wise increase between endometrial hyperplasia, atypical hyperplasia, and endometrial cancer. ALDH1 was also shown to be an early predictor of EC development, suggesting that it can serve as an independent prognostic indicator of patients with endometrial hyperplasia with or without atypia who would progress to cancer (p = 0.012).

Prediction of Lymph Node Metastasis in Superficial Esophageal Cancer Using a Pattern Recognition Neural Network

Background or Purpose

It is important to predict nodal metastases in patients with early esophageal cancer to stratify patients for endoscopic resection or esophagectomy. This study was to establish a novel artificial neural network (ANN) and assess its ability by comparing it with a traditional logistic regression (LR) model for predicting lymph node (LN) metastasis in patients with superficial esophageal squamous cell carcinoma (SESCC).

Methods

A primary cohort was established, composed of 733 patients who underwent esophagectomy for SESCC from December 2012 to December 2019. The following steps were applied: (i) predictor selection; (ii) development of an ANN and a LR model, respectively; (iii) cross-validation; and (iv) evaluation of performance between the two models. The diagnostic assessment was performed with sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), accuracy, C-index, net reclassification improvement (NRI), and integrated discrimination improvement (IDI).

Results

The established ANN model had 6 significant predictors: a past habit of alcohol taking, tumor size, submucosal invasion, histologic grade, lymph-vessel invasion, and preoperative CT result. The ANN model performed better than the LR model in specificity (91.20% vs 72.59%, p=0.006), PPV (56.49% vs 39.78%, p=0.020), accuracy (90.72% vs 74.49%, p<0.0001), C-index (91.5% vs 86.8%, p<0.001), and IDI (improved by 23.3%, p<0.001). There were no differences between these two models in sensitivity (87.06% vs 83.21%, p=0.764), NPV (98.17% vs 95.21%, p=0.627), and NRI (improved by −1.1%, p=0.824).

Conclusion

This ANN model is superior to the LR model and may become a valuable tool for the prediction of LN metastasis in patients with SESCC.

Tumoral Expression of CD166 in Human Esophageal Squamous Cell Carcinoma: Implications for Cancer Progression and Prognosis

Accumulating data showed that cancer stem cells (CSCs) identified by cell surface markers contribute to the initiation, progression, and prognosis of human cancers. In this study, the expression of CSC candidates CD166, CD44, and Lgr5 in 65 cases of esophageal squamous cell carcinoma (ESCC) and 16 cases of control esophageal tissues were examined with immunohistochemistry (IHC). The correlation between tumoral expression levels of these CSC candidates and clinicopathological variables was analyzed. IHC results showed that the expression of CD166 in esophageal control tissues was completely negative, but it was in 87.69% (57/65) ESCC tissues. The expression of CD44 and Lgr5 did not differ between esophageal control tissues and ESCC tissues (p > 0.05). In addition, there were not correlations found among the expression levels of CD166, CD44, and Lgr5 in ESCC tissues. Clinicopathological analysis revealed that the tumoral expression level of CD166 correlated with lymph node involvement and TNM staging in patients with ESCC, and lower tumoral expression of CD44 was found in patients with advanced TNM staging. Kaplan-Meier survival curves suggested that expression level of CD166 appeared to have a negative impact on overall survival rate after surgery in patients with ESCC. Such impact was not found in other two CSC candidates. The authors therefore conclude that CD166 is a potential prognostic biomarker and correlates with advanced progression features in patients with ESCC.

SET domain-containing 5 is a potential prognostic biomarker that promotes esophageal squamous cell carcinoma stemness

SET domain-containing 5 (SETD5) is an uncharacterized member of the protein lysine methyltransferase family. Although it was reported that SETD5 gene mutations are associated with the several types of human cancer, its functional role in esophageal squamous cell carcinoma (ESCC) progression has not been fully elucidated. In the present study, we used tissue samples from 147 patients with ESCC and ESCC cell lines to determine the clinicopathological significance of SETD5 in ESCC and its effects on ESCC stemness. We performed immunohistochemical staining, immunofluorescence imaging, and tumor sphere formation, colony formation, flow cytometry, wound healing, Transwell, and western blotting assays. SETD5 expression was upregulated in ESCC tissue and associated with primary tumor (pT) stage, clinical stage, lymph node metastasis, shorter overall survival rate, and disease-free survival rate. Cox regression analyses indicated that SETD5 is an independent poor prognostic factor of ESCC. In addition, SETD5 expression was correlated with cancer stemness-related protein, hypoxia-inducible factor-1α (HIF-1α), and CD68 expression. Moreover, immunofluorescence analysis revealed that SETD5 was co-localized with CD44 and SOX2 in TE10 and TE11 cells and that exposing cells to cobalt chloride increased HIF-1α, SETD5, and stemness-related protein expression in a time-dependent manner. Furthermore, SETD5 expression was significantly correlated with the expression of cell cycle-related genes and PI3K/Akt signaling pathway-related proteins. Finally, knocking down SETD5 downregulated the expression of stemness-related and PI3K/Akt signaling pathway proteins, while inhibiting tumor spheroid formation, cell proliferation, migration, and invasion in ESCC cells. These results indicate that SETD5 expression is associated with cancer stemness and that SETD5 is a potential prognostic biomarker and therapeutic target for ESCC.

Detention and Identification of Cancer Stem Cells in Esophageal Squamous Cell Carcinoma

Cancer stem cells (CSCs) are a small subpopulation of cells associated with cancer initiation, progression, metastasis, therapy resistant, and recurrence. In esophageal squamous cell carcinoma (ESCC), several cell surface and intracellular markers, for example, CD44, ALDH, Pygo2, MAML1, Twist1, Musashi1, side population (SP), CD271, and CD90, have been proposed to identify CSCs. In addition, stem cell markers such as ALDH1, HIWI, Oct3/4, ABCG2, SOX2, SALL4, BMI-1, NANOG, CD133, and podoplanin were associated with pathological stages of cancer, cancer recurrence, prognosis, and therapy resistance of patients with ESCC. Identification and isolation of CSCs could play an important part of improved cancer management regime in ESCC. Furthermore, CSCs may be used as the predictive tool for chemoradiotherapy response in ESCC. Different methods such as in vitro functional assays, cell sorting using various intracellular, and cell surface markers and xenotransplantation techniques are frequently used for the identification and isolation of CSCs in different cancers, including ESCC. However, none of these methods solely can guarantee complete isolation of CSC population. Therefore, a combination of methods is used for reliable detection and isolation of CSCs. Herein, we describe the identification and isolation of CSCs from ESCC cells by cell sorting after Hoechst 33342 staining followed by in vitro functional assays and in vivo mouse xenotransplantation techniques.

Targeting cancer stem cells in squamous cell carcinoma

Head and neck squamous cell carcinoma (HNSCC) is a highly aggressive tumor and the sixth most common cancer worldwide. Current treatment strategies for HNSCC are surgery, radiotherapy, chemotherapy, immunotherapy or combinatorial therapies. However, the overall 5-year survival rate of HNSCC patients remains at about 50%. Cancer stem cells (CSCs), a small population among tumor cells, are able to self-renew and differentiate into different tumor cell types in a hierarchical manner, similar to normal tissue. In HNSCC, CSCs are proposed to be responsible for tumor initiation, progression, metastasis, drug resistance, and recurrence. In this review, we discuss the molecular and cellular characteristics of CSCs in HNSCC. We summarize current approaches used in the literature for identification of HNSCC CSCs, and mechanisms required for CSC regulation. We also highlight the role of CSCs in treatment failure and therapeutic targeting options for eliminating CSCs in HNSCC.

Cancer Stem Cells in Head and Neck Carcinomas: Identification and Possible Therapeutic Implications

The recurrence and/or lack of response of certain tumors to radio- and chemotherapy has been attributed to a small subpopulation of cells termed cancer stem cells (CSCs). CSCs have been identified in many tumors (including solid and hematological tumors). CSCs are characterized by their capacity for self-renewal, their ability to introduce heterogeneity within a tumor mass and its metastases, genomic instability, and their insensitivity to both radiation and chemotherapy. The latter highlights the clinical importance of studying this subpopulation since their resistance to traditional treatments may lead to metastatic disease and/or tumor relapse. Head and neck squamous cell carcinomas (HNSCCs) are the sixth most common malignancy worldwide with the highest incidence occurring in East Asia and eastern and southern Africa. Several cellular subpopulations believed to have CSC properties have been isolated from HNSCCs, but at present, identification and characterization of CSCs remains an experimental challenge with no established or standardized protocols in place to confirm their identity. In this review we discuss current approaches to the study of CSCs with a focus on HNSCCs, particularly in the context of what this might mean from a therapeutic perspective.

Etiology, cancer stem cells and potential diagnostic biomarkers for esophageal cancer

Esophageal cancer (EC) has been a leading cause of cancer death worldwide in part due to late detection and lack of precision treatment. EC includes two major malignancies, esophageal squamous cell carcinoma (ESCC) and esophageal adenocarcinoma (EAC). Recent studies reveal that ESCC and EAC have distinct cell of origin and contain cancer stem cells (also known as tumor initiating cells) expressing different cell surface markers. These biomarkers have potentially important values for both early detection and finding effective therapy. In this review we summarize the updated findings for cell of origin and provide an overview of cancer cell biomarkers that have been tested for ESCC and EAC. In addition, we also discuss recent progress in the study of molecular mechanisms leading to these malignancies.

Aldehyde Dehydrogenases: Not Just Markers, but Functional Regulators of Stem Cells

Aldehyde dehydrogenase (ALDH) is a superfamily of enzymes that detoxify a variety of endogenous and exogenous aldehydes and are required for the biosynthesis of retinoic acid (RA) and other molecular regulators of cellular function. Over the past decade, high ALDH activity has been increasingly used as a selectable marker for normal cell populations enriched in stem and progenitor cells, as well as for cell populations from cancer tissues enriched in tumor-initiating stem-like cells. Mounting evidence suggests that ALDH not only may be used as a marker for stem cells but also may well regulate cellular functions related to self-renewal, expansion, differentiation, and resistance to drugs and radiation. ALDH exerts its functional actions partly through RA biosynthesis, as all-trans RA reverses the functional effects of pharmacological inhibition or genetic suppression of ALDH activity in many cell types in vitro. There is substantial evidence to suggest that the role of ALDH as a stem cell marker comes down to the specific isoform(s) expressed in a particular tissue. Much emphasis has been placed on the ALDH1A1 and ALDH1A3 members of the ALDH1 family of cytosolic enzymes required for RA biosynthesis. ALDH1A1 and ALDH1A3 regulate cellular function in both normal stem cells and tumor-initiating stem-like cells, promoting tumor growth and resistance to drugs and radiation. An improved understanding of the molecular mechanisms by which ALDH regulates cellular function will likely open new avenues in many fields, especially in tissue regeneration and oncology.

Cancer Stem Cell based molecular predictors of tumor recurrence in Oral squamous cell carcinoma

OBJECTIVE

This study aimed to identify the cancer stem cell specific biomarkers that can be effective candidate prognosticators of oral squamous cell carcinoma.

DESIGN

Microarray-based meta-analysis derived transcriptional profile of head and neck cancers was compared with the Cancer Stem Cell database to arrive at a subset of markers. This subset was further co-related with clinico-pathological parameters, recurrence and survival of oral cancer patients (n = 313) in The Cancer Genome Atlas database and in oral cancer (n = 28) patients.

RESULTS

Meta-analysis in combination with database comparison identified a panel of 221 genes specific to head and neck cancers. Correlation of expression levels of these markers in the oral cancer cohort of The Cancer Genome Atlas (n = 313) with treatment outcome identified 54 genes (p < 0.05 or fold change >2) associated with disease recurrence, 8 genes (NQO1, UBE2C, EDNRB, FKBP4, STAT3, HOXA1, RIT1, AURKA) being significant with high fold change. Assessment of the efficacy of the subset (n = 54) as survival predictors identified an additional 4 genes (CDK1, GINS2, PHF5 A, ERBB2) that co-related with poor disease-free survival (p < 0.05). CDK1 showed a significant association with the clinical stage, margin status and with advanced pathological parameters. Initial patient validation indicated that CDK1 and NQO1 significantly co-related with the poor disease-free and overall survival (p < 0.05).

CONCLUSION

This panel of oral cancer specific, cancer stem cell associated markers identified in this study, a subset of which was validated, will be of clinical benefit subject to large scale validation studies.

FTO regulates the chemo-radiotherapy resistance of cervical squamous cell carcinoma (CSCC) by targeting β-catenin through mRNA demethylation

The role of N⁶ -methyladenosine (m⁶ A) demethylase fat mass and obesity-associated protein (FTO) in the regulation of chemo-radiotherapy resistance remains largely unknown. Here, we show that the mRNA level of FTO is elevated in cervical squamous cell carcinoma (CSCC) tissues when compared with respective adjacent normal tissues. FTO enhances the chemo-radiotherapy resistance both in vitro and in vivo through regulating expression of β-catenin by reducing m⁶ A levels in its mRNA transcripts and in turn increases excision repair cross-complementation group 1 (ERCC1) activity. Clinically, the prognostic value of FTO for overall survival is found to be dependent on β-catenin expression in human CSCC samples. Taken together, these findings uncover a critical function for FTO and its substrate m⁶ A in the regulation of chemo-radiotherapy resistance, which may bear potential clinical implications for CSCC treatment.

Role of ALDH1 in the prognosis of esophageal cancer and its relationship with tumor microenvironment

Aldehyde dehydrogenase 1 (ALDH1) is associated with tumorigenesis, and significantly increased in cancer stem-like cells. In the present study, the role of ALDH1 in esophageal squamous cell carcinoma (ESCC) was investigated. We retrospectively analyzed the clinical outcomes of 148 ESCC and examined its correlation with ALDH1 levels. Furthermore, we preformed cellular and animal experiments to investigate the role of ALDH1 in tumor progression and microenvironment. Our data revealed that ALDH1 staining was positively linked to a higher clinical stage, higher loco-regional failure rate, and shorter survival time. Furthermore, there was a positive link between ALDH1 expression and IL-6 signaling according to the data of clinical specimens and cellular experiments. Using animal model, ALDH1-positive tumors were associated with aggressive tumor growth, increased IL-6, augmented epithelial-mesenchymal transition (EMT), and activation of myeloid-derived suppressor cells (MDSCs). Blockade of COX-2 attenuated the aggressive tumor growth of ALDH1-positive cancer cells. In conclusion, our findings suggested that ALDH1 played an important role in tumor aggressiveness and associated with a tumor-promoting microenvironment in esophageal cancer. Directly targeting ALDH1 or using a COX-2 inhibitor could be a promising strategy for the treatment of ESCC.

Evaluation of the correlation of vasculogenic mimicry, ALDH1, KAI1 and microvessel density in the prediction of metastasis and prognosis in colorectal carcinoma

Background

Metastasis and recurrence are the most common reasons for treatment failure of colorectal carcinoma (CRC). Vasculogenic mimicry (VM, blood supply formation often seen in highly aggressive tumors), Aldehyde dehydrogenase 1 (ALDH1, a biomarker of cancer stem cells), KAI1 (a suppressor gene of tumor metastasis) are all valuable factors for metastasis and prognosis in diverse human cancers. However, the correlation of VM, ALDH1, KAI1 and microvessel density (MVD) in CRC is unclear. In this study, we analyzed the correlations among VM, ALDH1, KAI1 and MVD, as well as their respective correlations with clinicopathological parameters and survival in CRC.

Methods

The level of VM, ALDH1, KAI1 and MVD in 204 whole tissue samples of CRC were examined by immunhistochemistry. Clinical data was also collected.

Results

Levels of VM, ALDH1 and MVD were significantly higher, and levels of KAI1 significantly lower, in CRC tissues than in normal colorectal tissues. Levels of VM, ALDH1 and MVD were positively associated with invasion of depth, lymph node metastasis (LNM), distant metastasis and tumor-node-metastasis (TNM) stages, and negatively with patients’ overall survival (OS). Levels of KAI1 was negatively correlated with invasion of depth, LNM, distant metastasis and TNM stages, and the KAI1 positive expression subgroup had significantly longer OS than did the KAI1- subgroup. In multivariate analysis, high levels of VM, ALDH1 and KAI1, as well as TNM stages were independently correlated with lower OS in patients with CRC.

Conclusions

VM, MVD and the expression of ALDH1 and KAI1 may represent promising metastatic and prognostic biomarkers, as well as potential therapeutic targets for CRC.

Expression status of CD44 and CD133 as a prognostic marker in esophageal squamous cell carcinoma treated with neoadjuvant chemotherapy followed by radical esophagectomy

Cancer stem cells (CSCs) have self-renewal and pluripotency capabilities and contribute to cancer progression and chemoresistance. It has been proposed that the treatment resistance and heterogeneity of CSCs are deeply involved in the prognosis of patients with esophageal squamous cell carcinoma (ESCC). The objective of this study was to identify the influence of the expression status of the CSC markers CD44 and CD133 on chemotherapeutic efficacy and prognosis in ESCC patients who underwent radical esophagectomy after neoadjuvant chemotherapy (NAC). Endoscopically biopsied specimens taken before NAC and surgically resected specimens after NAC were immunohistochemically assessed for CD44 and CD133 expression for 47 ESCC patients who underwent NAC followed by radical esophagectomy. The correlation between CD44 and CD133 expression status and clinicopathological findings and the prognosis of ESCC patients after NAC followed by esophagectomy were analyzed. The percentages of CD44-positive cells and CD133-positive cells in specimens were increased after NAC. CD44 and CD133 expression status before NAC did not correlate with the degree of tumor progression and had no impact on the chemotherapeutic effect. However, strong expression of CD44 or CD133 and a high proportion of CD133-expressing cells before NAC were significantly associated with poorer esophageal cancer-specific survival. Patients with strong expression of CD44 or CD133 and those with a high ratio of CD133-positive tumor cells showed significantly poor prognosis regardless of the effect of chemotherapy. Multivariate analysis showed that simultaneous strong expression of CD44 and CD133 before NAC, a high rate of CD133-positive tumor cells before NAC, and primary tumor remission assessed by preoperative endoscopy were significant independent prognostic factors for ESCC. Our data indicate that CD44 and CD133 expression status prior to treatment dictates the malignant potential of ESCC and may be a novel predictor of recurrence and prognosis of ESCC patients after treatment.

Inhibition of SALL4 reduces tumorigenicity involving epithelial-mesenchymal transition via Wnt/β-catenin pathway in esophageal squamous cell carcinoma

BACKGROUND

Growing evidence suggests that SALL4 plays a vital role in tumor progression and metastasis. However, the molecular mechanism of SALL4 promoting esophageal squamous cell carcinoma (ESCC) remains to be elucidated.

METHODS

The gene and protein expression profiles- were examined by using quantitative real-time PCR, immunohistochemistry and western blotting. Small hairpin RNA was used to evaluate the role of SALL4 both in cell lines and in animal models. Cell proliferation, apoptosis and invasion were assessed by CCK8, flow cytometry and transwell-matrigel assays. Sphere formation assay was used for cancer stem cell derivation and characterization.

RESULTS

Our study showed that the transcription factor SALL4 was overexpressed in a majority of human ESCC tissues and closely correlated with a poor outcome. We established the lentiviral system using short hairpin RNA to knockdown SALL4 in TE7 and EC109 cells. Silencing of SALL4 inhibited the cell proliferation, induced apoptosis and the G1 phase arrest in cell cycle, decreased the ability of migration/invasion, clonogenicity and stemness in vitro. Besides, down-regulation of SALL4 enhanced the ESCC cells' sensitivity to cisplatin. Xenograft tumor models showed that silencing of SALL4 decreased the ability to form tumors in vivo. Furthermore, our study demonstrated that SALL4 played a vital role in modulating the stemness of ESCC cells via Wnt/β-catenin signaling pathway and in epithelial-mesenchymal transition.

CONCLUSIONS

Our results revealed that SALL4 might serve as a functional marker for ESCC cancer stem cell, a crucial marker for prognosis and an attractive candidate for target therapy of ESCC.

Esophageal cancer stem cells and implications for future therapeutics

Esophageal carcinoma (EC) is a lethal disease with high morbidity and mortality worldwide, and the incidence has been increasing in recent years. Although the diagnosis and treatment of EC have improved considerably, EC has rapidly progressed in the clinical setting and has a poor prognosis for its metastasis and recurrence. The general idea of cancer stem cells (CSCs) is primarily based on clinical and experimental observations, indicating the existence of a subpopulation of cells that can self-renew and differentiate. The EC stem cells, which can be isolated from normal pluripotent stem cells by applying similar biomarkers, may participate in promoting esophageal tumorigenesis through renewal and repair. In this review, major emphasis is given to CSC markers, altered CSC-specific pathways, and molecular targeting agents currently available to target CSCs of esophageal cancer. The roles of numerous markers (CD44, aldehyde dehydrogenase, CD133, and ATP-binding cassette subfamily G member 2) and developmental signaling pathways (Wnt/β-catenin, Notch, hedgehog, and Hippo) in isolating esophageal CSCs are discussed in detail. Targeting CSCs can be a logical strategy to treat EC, as these cells are responsible for carcinoma recurrence and chemoradiation resistance.

Cancer stem cells in oesophageal squamous cell carcinoma: Identification, prognostic and treatment perspectives

Cancer stem cells (CSCs) are a vital subpopulation of cells to target for the treatment of cancers. In oesophageal squamous cell carcinoma (ESCC), there are several markers such as CD44, ALDH, Pygo2, MAML1, Twist1, Musashi1, Side population (SP), CD271 and CD90 that have been proposed to identify the cancer stem cells in individual cancer masses. It has also been demonstrated that stem cell markers like ALDH1, HIWI, Oct3/4, ABCG2, SOX2, SALL4, BMI-1, NANOG, CD133 and podoplanin are associated with patient's prognosis, pathological stages, cancer recurrence and therapy resistance. Finding new cancer stem cell targets or designing drugs to manipulate the known molecular targets in CSCs could be useful for improvements in clinical outcomes of the disease. To conclude, data suggest that CSCs in oesophageal squamous cell carcinoma are related to resistance to therapy and poor prognosis of patients with ESCC. Therefore, innovative insights into CSC biology and CSC-targeted therapies will help to achieve more effective management of patients with oesophageal squamous cell carcinoma.

Aldehyde dehydrogenases in cancer: an opportunity for biomarker and drug development?

Aldehyde dehydrogenases (ALDHs) belong to a superfamily of 19 isozymes that are known to participate in many physiologically important biosynthetic processes including detoxification of specific endogenous and exogenous aldehyde substrates. The high expression levels of an emerging number of ALDHs in various cancer tissues suggest that these enzymes have pivotal roles in cancer cell survival and progression. Mapping out the heterogeneity of tumours and their cancer stem cell (CSC) component will be key to successful design of strategies involving therapeutics that are targeted against specific ALDH isozymes. This review summarises recent progress in ALDH-focused cancer research and discovery of small-molecule-based inhibitors.

ALDH1A1 overexpression is associated with the progression and prognosis in gastric cancer

BACKGROUND

Aldehyde dehydrogenase 1 family member A1 (ALDH1A1) is a cancer stem cell marker, and its expression correlates with prognosis in a number of malignancies. The aim of this study is to determine the relationship of ALDH1A1 expression with clinicopathological parameters and prognosis in gastric cancer.

METHODS

ALDH1A1 and matrix metallopeptidase 9 (MMP-9) was evaluated by immunohistochemistry in 216 gastric carcinoma samples. The association between expression of ALDH1A1 and MMP-9, clinicopathological parameters, and prognosis of gastric cancer was examined.

RESULTS

ALDH1A1 protein expression was significantly associated with depth invasion, lymph node metastasis and stage of disease (all P<0.05). Both univariate and multivariate analyses revealed that ALDH1A1 was an independent prognostic factor for both overall survival (OS) and recurrence-free survival (RFS) (both P<0.001). Furthermore, ALDH1A1 overexpression was associated with poor prognosis in patients subgroups stratified by tumor size, depth invasion and lymph node metastasis. Moreover, ALDH1A1 was significantly correlated with MMP-9 among 216 gastric cancer tissues (P<0.001). Patients who had ALDH1A1 overexpression, in which tumor cells displayed high invasiveness, had poor OS and shorter RFS.

CONCLUSION

ALDH1A1 plays an important role in tumor aggressiveness and prognosis, and may act as a promising target for prognostic prediction.

A retrospective review of the prognostic value of ALDH-1, Bmi-1 and Nanog stem cell markers in esophageal squamous cell carcinoma

Stem cell markers are upregulated in various cancers and have potential as prognostic indicators. The objective of this study was to determine the expression of three stem cell markers, aldehyde dehydrogenase 1 (ALDH-1), B cell-specific Moloney murine leukemia virus integration site 1 (Bmi-1), and Nanog, in esophageal squamous cell carcinoma (ESCC) tissues. Immunohistochemistry was used to measure the expression of ALDH-1, Bmi-1, and Nanog in ESCC tissues from 41 patients who received pre-operative chemoradiation. We evaluated the relationship between expression of these markers, and clinicopathological features, tumor regression grade (TRG), and 5-year overall survival (OS). There were no significant associations of ALDH-1 or Bmi-1 expression with age, gender, clinical stage, and treatments (p>0.05). However, patients with Nanog-positive tumors were significantly older than those whose tumors were Nanog-negative (p = 0.033). TRG after treatment was significantly associated with expression of ALDH-1 (p = 0.001), Bmi-1 (p = 0.004), and Nanog (p<0.001). Although OS was significantly better in patients with low TRGs (p = 0.001), there were no significant correlations between ALDH-1, Bmi-1, or Nanog with OS. Expression of ALDH-1, Bmi-1, and Nanog correlated with TRG, but not OS. Further large studies are necessary to fully elucidate the prognostic value of these stem cell markers for ESCC patients.

ALDH1A1 defines invasive cancer stem-like cells and predicts poor prognosis in patients with esophageal squamous cell carcinoma

Invasion and metastasis are the major cause of deaths in patients with esophageal cancer. In this study, we isolated cancer stem-like cells from an esophageal squamous cell carcinoma cell line EC109 based on aldehyde dehydrogenase 1A1 (ALDH1A1), and found that ALDH1A1(high) cells possessed the capacities of self-renewal, differentiation and tumor initiation, indications of stem cell properties. To support their stemness, ALDH1A1(high) cells exhibited increased potential of invasion and metastasis as compared with ALDH1A1(low) cells. ALDH1A1(high) esophageal squamous cell carcinoma cells expressed increased levels of mRNA for vimentin, matrix metalloproteinase 2, 7 and 9 (MMP2, MMP7 and MMP9), but decreased the level of E-cadherin mRNA, suggesting that epithelial-mesenchymal transition and secretary MMPs may be attributed to the high invasive and metastatic capabilities of ALDH1A1(high) cells. Furthermore, we examined esophageal squamous cell carcinoma specimens from 165 patients and found that ALDH1A1(high) cells were associated with esophageal squamous dysplasia and the grades, differentiation and invasion depth, lymph node metastasis and UICC stage of esophageal squamous cell carcinoma, as well as poor prognosis of patients. Our results provide the strong evidence that ALDH1A1(high) cancer stem-like cells contribute to the invasion, metastasis and poor outcome of human esophageal squamous cell carcinoma.

ALDH1 is a better clinical indicator for relapse of invasive ductal breast cancer than the CD44+/CD24- phenotype

Breast cancer stem cells are thought to be associated with metastasis and poor prognosis, but their clinical importance remains poorly understood. The aim of this study was to investigate whether certain phenotypes of breast cancer stem cells were clinically important factors regarding metastasis. Patients with primary breast cancer (n=121) were included in this study. Breast cancer stem cells were identified by immunohistochemical staining of CD44, CD24, and aldehyde dehydrogenase 1 (ALDH1) in tumor tissues from primary and recurrent or metastatic lesions. CD44+/CD24- cells and ALDH1+ cells were considered breast cancer stem cells. Sixty-five patients had metastatic or recurrent tumors. ALDH1+ tumors were significantly associated with a high rate of metastasis or recurrence (63.1%; P=0.026). Although there was no significant association between the proportion of CD44+/CD24- tumor cells and metastasis rates, a high proportion of CD44+/CD24- tumor cells was a risk factor for metastasis or recurrence (P=0.035). Changes in the proportion of CD44+/CD24- or ALDH1+ tumor cells between primary lesions and recurrent lesions were studied in 27 patients. The proportion of ALDH1+ tumor cells increased significantly (P=0.019) after recurrence, but the proportion of CD44+/CD24- tumor cells did not. Our findings suggest that ALDH1+ and CD44+/CD24- breast cancer stem cells play significant roles in metastasis. The rate of ALDH1+ cells appears to be a better predictive marker of breast cancer metastasis than the CD44+/CD24- phenotype.

Expansion of breast cancer stem cells with fibrous scaffolds

Cancer stem cells (CSCs) are hypothesized as tumor-initiating cells within tumors and main contributors of tumor growth, metastasis and recurrence. Mammary cancer cells, MCF-7 cells, were cultured on 3D polycaprolactone (PCL) fibrous scaffolds, showing an increased proportion of CSCs. The expression of stem cell markers, including OCT3/4 and SOX2, and breast CSC-specific markers, SOX4 and CD49f, was significantly upregulated, and the mammosphere-forming capability in cells cultured on PCL fibrous scaffolds increased. The fibrous scaffolds also induced the elongation of MCF-7 cells and extended cell proliferation. The increase of CSC properties after being cultured on fibrous scaffolds was further confirmed with two luminal-type mammary cell lines, T47D and SK-BR-3, and a basal-type cell line, MDA-MB-231, by ALDEFLUOR assay and mammosphere formation assay. Moreover, we observed the upregulation of epithelial to mesenchymal transition and increased invasive capability in cells cultured on PCL fibrous scaffolds. These data suggest that the increase of CSC proportion in a 3D culture system may account for the enhanced malignancy. Therefore, our PCL fibrous scaffolds can potentially be used for CSCs enrichment and anti-cancer drug screening.

ALDH-1 expression levels predict response or resistance to preoperative chemoradiation in resectable esophageal cancer patients

PURPOSE

Operable thoracic esophageal/gastroesophageal junction carcinoma (EC) is often treated with chemoradiation and surgery but tumor responses are unpredictable and heterogeneous. We hypothesized that aldehyde dehydrogenase-1 (ALDH-1) could be associated with response.

METHODS

The labeling indices (LIs) of ALDH-1 by immunohistochemistry in untreated tumor specimens were established in EC patients who had chemoradiation and surgery. Univariate logistic regression and 3-fold cross validation were carried out for the training (67% of patients) and validation (33%) sets. Non-clinical experiments in EC cells were performed to generate complimentary data.

RESULTS

Of 167 EC patients analyzed, 40 (24%) had a pathologic complete response (pathCR) and 27 (16%) had an extremely resistant (exCRTR) cancer. The median ALDH-1 LI was 0.2 (range, 0.01-0.85). There was a significant association between pathCR and low ALDH-1 LI (p ≤ 0.001; odds-ratio [OR] = 0.432). The 3-fold cross validation led to a concordance index (C-index) of 0.798 for the fitted model. There was a significant association between exCRTR and high ALDH-1 LI (p ≤ 0.001; OR = 3.782). The 3-fold cross validation led to the C-index of 0.960 for the fitted model. In several cell lines, higher ALDH-1 LIs correlated with resistant/aggressive phenotype. Cells with induced chemotherapy resistance upregulated ALDH-1 and resistance conferring genes (SOX9 and YAP1). Sorted ALDH-1+ cells were more resistant and had an aggressive phenotype in tumor spheres than ALDH-1- cells.

CONCLUSIONS

Our clinical and non-clinical data demonstrate that ALDH-1 LIs are predictive of response to therapy and further research could lead to individualized therapeutic strategies and novel therapeutic targets for EC patients.

Biomarkers for predicting future metastasis of human gastrointestinal tumors

The recent advances in surgery and radiation therapy have significantly improved the prognosis of patients with primary cancer, and the major challenge of cancer treatment now is metastatic disease development. The 5-year survival rate of cancer patients who have distant metastasis at diagnosis is extremely low, suggesting that prediction and early detection of metastasis would definitely improve their prognosis because suitable patient therapeutic management and treatment strategy can be provided. Cancer cells from a primary site give rise to a metastatic tumor via a number of steps which require the involvement and altered expression of many regulators. These regulators may serve as biomarkers for predicting metastasis. Over the past few years, numerous regulators have been found correlating with metastasis. In this review, we summarize the findings of a number of potential biomarkers that are involved in cadherin-catenin interaction, integrin signaling, PI3K/Akt/mTOR signaling and cancer stem cell identification in gastrointestinal cancers. We will also discuss how certain biomarkers are associated with the tumor microenvironment that favors cancer metastasis.

Colorectal micropapillary carcinomas are associated with poor prognosis and enriched in markers of stem cells

Colorectal micropapillary carcinoma has recently been reported as an aggressive variant of adenocarcinoma with a high incidence of lymph node metastasis, but has not been well investigated in terms of survival analysis. This study analyzed the clinicopathological characteristics, including survival data, of the patients with micropapillary carcinoma. We hypothesized that the aggressive features of micropapillary carcinoma might be related to the presence of more tumor cells with stem cell phenotype in colorectal cancer. Fifty-five (10%) micropapillary carcinoma cases were identified among 561 cases of colorectal cancer. We compared the clinicopathological characteristics, including survival data and immunohistochemical profiles of stem cell markers (SOX2, NOTCH3, CD44v6, CD166, ALDH1) of micropapillary carcinomas with those of randomly selected 112 conventional adenocarcinomas lacking micropapillary carcinoma components (non-micropapillary carcinoma) in the colorectum. To exclude the possibility of dilution of control group by patients with microsatellite instability-high carcinomas, we divided non-micropapillary carcinomas into microsatellite instability-high carcinoma and microsatellite stable tumors. Micropapillary carcinomas were characterized by more frequent lymphovascular invasion (P<0.0001) and lymph node metastasis (P<0.0001), higher pathological T and tumor node metastasis stages (P=0.047 and P=0.001), and more frequent SOX2 (P=0.038) and NOTCH3 expressions (P=0.005). Overall 5-year survival rate for patients with micropapillary carcinoma (37%) was significantly lower than for microsatellite instability-high carcinoma and microsatellite stable carcinoma patients (92 and 72%, P<0.0001). The presence of the micropapillary carcinoma component was shown to be associated with a significantly worse survival rate in univariate (P<0.0001) and multivariate (P=0.003, Cox hazard ratio 2.402) analyses. In conclusion, recognition of the micropapillary carcinoma component in colonic adenocarcinoma is very important, because the micropapillary carcinoma has been associated with a significantly worse prognosis. We also found a higher expression rate of cancer stem cell markers in micropapillary carcinomas, suggesting their potential contribution to the survival disadvantage of micropapillary carcinoma.

Relevance of cancer initiating/stem cells in carcinogenesis and therapy resistance in oral cancer

Oral squamous cell carcinoma (OSCC) acquires the top most position among the other malignancies and patients die with this disease complication within 5years. One of the causes behind this scenario is the identified sub-population in heterogeneous tumor mass that are purported as cancer stem cells (CSCs) or tumor-initiating cells (TICs). Oral CSCs populations show upregulation of the stem cell related genes Oct-4, Nanog, Nestin, CK19, BMI-1, CD117 (c-kit), CD44 and CD133 with sunken expression of involucrin and CK13. This small proportion of tumor cells can sustain tumor growth, proliferation, invasion and distant metastasis playing a pivotal role in relapse of oral cancer. Unanimous risk factors include prevalent use of cigarette smoking, tobacco chewing with less explored HPV infection play an important role in origin of CSCs. Moreover, highly apoptotic resistant oral CSCs show enhanced protective autophagy for survival. Several studies report them to be more chemo and radiation resistant than non-stem cell population implicating the failure of the present cancer therapy. This resistance associated with normal stem cell protective mechanisms including increased expression of drug efflux pumps, alteration in program cell death, cell cycle, and DNA repair mechanisms. Notably, CSCs appear to play a major role in tumor recurrence and metastatic spread, common causes of the high morbidity and ultimately the death of the majority of patients with oral cancer. In this review we would like to highlight the intricate crosstalk of the cancer initiating/stem cells involved in carcinogenesis and potential hurdle to oral cancer therapy.

Progress in research of markers for cancer stem cells in esophageal squamous cell carcinoma

Esophageal squamous cell carcinoma (ESCC) is one of the most common malignant tumors in China, with high morbidity or mortality. In recent years, there has been a growing amount of evidence supporting the existence of a rare proportion of tumor cells termed cancer stem cells (CSCs) in diverse solid malignancies including ESCC. CSCs are closely related to the poor biological behaviors and drug resistance of ESCC. Markers for CSCs play an important role in the separation of CSCs, and the research on CSC markers can help clarify the mechanisms behind tumor development and guide tumor treatment.

A CD90(+) tumor-initiating cell population with an aggressive signature and metastatic capacity in esophageal cancer

Tumor-initiating cells (TIC), also known as cancer stem cells, are regarded widely as a specific subpopulation of cells needed for cancer initiation and progression. TICs have yet to be identified in esophageal tumors that have an increasing incidence in developed countries. Here, we report a CD90(+) cell population found in esophageal squamous cell carcinoma (ESCC), which is endowed with stem cell-like properties and high tumorigenic and metastatic potential. mRNA profiling of these cells suggested pathways through which they drive tumor growth and metastasis, with deregulation of an Ets-1/MMP signaling pathway and epithelial-mesenchymal transition figuring prominently. These cells possessed higher self-renewal activity and were sufficient for tumor growth, differentiation, metastasis, and chemotherapeutic resistance. CD90(+) TICs were isolated and characterized from ESCC clinical specimens as well as ESCC cell lines. In freshly resected clinical specimens, they represented a rare cell population, the levels of which correlated with strong family histories and lymph node metastasis. Our results prompt further study of this CD90(+) population of esophageal TICs as potential therapeutic targets.

ALDH1 expression indicates chemotherapy resistance and poor outcome in node-negative rectal cancer

The cancer stem cell marker aldehyde dehydrogenase 1 (ALDH1) associates with treatment resistance and adverse outcome in several human cancers. We studied ALDH1 expression in rectal cancer, with special emphasis on its association with treatment response and disease outcome. Immunohistochemical staining for ALDH1 was conducted for 64 biopsies and 209 operative samples from rectal cancer patients treated with short- (n = 89) or long-course (n = 46) (chemo)radiotherapy plus surgery, or with surgery only (n = 74). The staining results were compared to clinicopathological variables, tumor regression grade (TRG) and disease outcome. Nuclear β-catenin expression pattern was analyzed from 197 operative samples. Positive ALDH1 expression was present in 149 operative samples (71%), correlating with deficient nuclear β-catenin regulation (P = .018). In a pairwise comparison of respective biopsy and operative samples, ALDH1 expression remained stable or increased after preoperative (chemo)radiotherapy in most of the cases, while it decreased in few cases only (P = .02 for positive/negative category; P <.001 for intensity). ALDH1 expression did not, however, relate to tumor regression grade. In node-negative rectal cancer, ALDH1 expression was an independent predictor of short disease-free and disease-specific survival (P = .044; P = .049), specifically among patients treated with adjuvant chemotherapy. We conclude that ALDH1 associates with deregulated β-catenin signaling, supporting the role of ALDH1 in rectal cancer stemness. ALDH1 expression relates to poor outcome in early stage rectal cancer, a group where new prognostic tools are particularly needed, and may indicate chemo- and radioresistance.

The effect of several intertrial intervals on the 1 Hz interference effect

Gynecologic cancers cause over 600,000 deaths annually in women worldwide. The development of chemoresistance after initial rounds of chemotherapy contributes to tumor relapse and death due to gynecologic malignancies. In this regard, cancer stem cells (CSCs), a subpopulation of stem cells with the ability to undergo self-renewal and clonal evolution, play a key role in tumor progression and drug resistance. Aldehyde dehydrogenases (ALDH) are a group of enzymes shown to be robust CSC markers in gynecologic and other malignancies. These enzymes also play functional roles in CSCs, including detoxification of aldehydes, scavenging of reactive oxygen species (ROS), and retinoic acid (RA) signaling, making ALDH an attractive therapeutic target in various clinical scenarios. In this review, we discuss the critical roles of the ALDH in driving stemness in different gynecologic malignancies. We review inhibitors of ALDH, both general and isoform-specific, which have been used to target CSCs in gynecologic cancers. Many of these inhibitors have been shown to be effective in preclinical models of gynecologic malignancies, supporting further development in the clinic. Furthermore, ALDH inhibitors, including 673A and CM037, synergize with chemotherapy to reduce tumor growth. Thus, ALDH-targeted therapies hold promise for improving patient outcomes in gynecologic malignancies.