The effects of the location of cancer stem cell marker CD133 on the prognosis of hepatocellular carcinoma patients

Targeting Hepatic Cancer Stem Cells (CSCs) and Related Drug Resistance by Small Interfering RNA (siRNA)

Tumor recurrence after curative therapy and hepatocellular carcinoma (HCC) cells' resistance to conventional therapies is the reasons for the worse clinical results of HCC patients. A tiny population of cancer cells with a strong potential for self-renewal, differentiation, and tumorigenesis has been identified as cancer stem cells (CSCs). The discovery of CSC surface markers and the separation of CSC subpopulations from HCC cells have been made possible by recent developments in the study of hepatic (liver) CSCs. Hepatic CSC surface markers include epithelial cell adhesion molecules (EpCAM), CD133, CD90, CD13, CD44, OV-6, ALDH, and K19. CSCs have a significant influence on the development of cancer, invasiveness, self-renewal, metastasis, and drug resistance in HCC, and thus provide a therapeutic chance to treat HCC and avoid its recurrence. Therefore, it is essential to develop treatment approaches that specifically and effectively target hepatic stem cells. Given this, one potential treatment approach is to use particular small interfering RNA (siRNA) to target CSC, disrupting their behavior and microenvironment as well as changing their epigenetic state. The characteristics of CSCs in HCC are outlined in this study, along with new treatment approaches based on siRNA that may be used to target hepatic CSCs and overcome HCC resistance to traditional therapies.

Interferon-α induces differentiation of cancer stem cells and immunosuppression in hepatocellular carcinoma by upregulating CXCL8 secretion

Interferon-alpha (IFN-α) is widely used in the clinical treatment of patients with chronic hepatitis B and hepatocellular carcinoma (HCC). However, high levels of CXCL8 are associated with resistance to IFN-α therapy and poorer prognosis in advanced cancers. In this study, we investigated whether IFN-α could directly induce the production of CXCL8 in HCC cells and whether CXCL8 could antagonize the antitumor activity of IFN-α. We found that IFN-α not only upregulated the expression of the inducible genes CXCL9, CXCL10, CXCL11 and PD-L1, but also significantly stimulated CXCL8 secretion in HCC cells. Mechanically, IFN-α induces CXCL8 expression by activating the AKT and JNK pathways. In addition, our results demonstrate that IFN-α exposure significantly increases the differentiation of HCC stem cells, but this effect is reversed by the addition of the CXCL8 receptor CXCR1/2 inhibitor Reparixin and STAT3 inhibitor Stattic. Besides, our study reveals that the cytokine CXCL8 secreted by IFN-α-induced HCC cells inhibits T-cell function. Conversely, inhibition of CXCL8 promotes TNF-α and IFN-γ secretion by T cells. Finally, liver cancer patients who received anti-PD-1/PD-L1 immunotherapy with high CXCL8 expression had a lower immunotherapy efficacy. Overall, our findings clarify that IFN-α triggers immunosuppression and cancer stem cell differentiation in hepatocellular carcinoma by upregulating CXCL8 secretion. This discovery provides a novel approach to enhance the effectiveness of HCC treatment in the future.

Emerging roles of prominin-1 (CD133) in the dynamics of plasma membrane architecture and cell signaling pathways in health and disease

Prominin-1 (CD133) is a cholesterol-binding membrane glycoprotein selectively associated with highly curved and prominent membrane structures. It is widely recognized as an antigenic marker of stem cells and cancer stem cells and is frequently used to isolate them from biological and clinical samples. Recent progress in understanding various aspects of CD133 biology in different cell types has revealed the involvement of CD133 in the architecture and dynamics of plasma membrane protrusions, such as microvilli and cilia, including the release of extracellular vesicles, as well as in various signaling pathways, which may be regulated in part by posttranslational modifications of CD133 and its interactions with a variety of proteins and lipids. Hence, CD133 appears to be a master regulator of cell signaling as its engagement in PI3K/Akt, Src-FAK, Wnt/β-catenin, TGF-β/Smad and MAPK/ERK pathways may explain its broad action in many cellular processes, including cell proliferation, differentiation, and migration or intercellular communication. Here, we summarize early studies on CD133, as they are essential to grasp its novel features, and describe recent evidence demonstrating that this unique molecule is involved in membrane dynamics and molecular signaling that affects various facets of tissue homeostasis and cancer development. We hope this review will provide an informative resource for future efforts to elucidate the details of CD133's molecular function in health and disease.

Functional Roles of CD133: More than Stemness Associated Factor Regulated by the Microenvironment

CD133 protein has been one of the most used surface markers to select and identify cancer cells with stem-like features. However, its expression is not restricted to tumoral cells; it is also expressed in differentiated cells and stem/progenitor cells in various normal tissues. CD133 participates in several cellular processes, in part orchestrating signal transduction of essential pathways that frequently are dysregulated in cancer, such as PI3K/Akt signaling and the Wnt/β-catenin pathway. CD133 expression correlates with enhanced cell self-renewal, migration, invasion, and survival under stress conditions in cancer. Aside from the intrinsic cell mechanisms that regulate CD133 expression in each cellular type, extrinsic factors from the surrounding niche can also impact CD33 levels. The enhanced CD133 expression in cells can confer adaptive advantages by amplifying the activation of a specific signaling pathway in a context-dependent manner. In this review, we do not only describe the CD133 physiological functions known so far, but importantly, we analyze how the microenvironment changes impact the regulation of CD133 functions emphasizing its value as a marker of cell adaptability beyond a cancer-stem cell marker.

Can CD133 Be Regarded as a Prognostic Biomarker in Oncology: Pros and Cons

The CD133 cell membrane glycoprotein, also termed prominin-1, is expressed on some of the tumor cells of both solid and blood malignancies. The CD133-positive tumor cells were shown to exhibit higher proliferative activity, greater chemo- and radioresistance, and enhanced tumorigenicity compared to their CD133-negative counterparts. For this reason, CD133 is regarded as a potential prognostic biomarker in oncology. The CD133-positive cells are related to the cancer stem cell subpopulation in many types of cancer. Recent studies demonstrated the involvement of CD133 in the regulation of proliferation, autophagy, and apoptosis in cancer cells. There is also evidence of its participation in the epithelial-mesenchymal transition associated with tumor progression. For a number of malignant tumor types, high CD133 expression is associated with poor prognosis, and the prognostic significance of CD133 has been confirmed in a number of meta-analyses. However, some published papers suggest that CD133 has no prognostic significance or even demonstrate a certain correlation between high CD133 levels and a positive prognosis. This review summarizes and discusses the existing evidence for and against the prognostic significance of CD133 in cancer. We also consider possible reasons for conflicting findings from the studies of the clinical significance of CD133.

Inhibition of Autophagy Promotes the Elimination of Liver Cancer Stem Cells by CD133 Aptamer-Targeted Delivery of Doxorubicin

Doxorubicin is the most frequently used chemotherapeutic agent for the treatment of hepatocellular carcinoma. However, one major obstacle to the effective management of liver cancer is the drug resistance derived from the cancer stem cells. Herein, we employed a CD133 aptamer for targeted delivery of doxorubicin into liver cancer stem cells to overcome chemoresistance. Furthermore, we explored the efficacy of autophagy inhibition to sensitize liver cancer stem cells to the treatment of CD133 aptamer-doxorubicin conjugates based on the previous observation that doxorubicin contributes to the survival of liver cancer stem cells by activating autophagy. The kinetics and thermodynamics of aptamer-doxorubicin binding, autophagy induction, cell apoptosis, and self-renewal of liver cancer stem cells were studied using isothermal titration calorimetry, Western blot analysis, annexin V assay, and tumorsphere formation assay. The aptamer-cell binding andintracellular accumulation of doxorubicin were quantified via flow cytometry. CD133 aptamer-guided delivery of doxorubicin resulted in a higher doxorubicin concentration in the liver cancer stem cells. The combinatorial treatment strategy of CD133 aptamer-doxorubicin conjugates and an autophagy inhibitor led to an over 10-fold higher elimination of liver cancer stem cells than that of free doxorubicin in vitro. Future exploration of cancer stem cell-targeted delivery of doxorubicin in conjunction with autophagy inhibition in vivo may well lead to improved outcomes in the treatment of hepatocellular carcinoma.

Differential expression of hepatic cancer stemness and hypoxia markers in residual cancer after locoregional therapies for hepatocellular carcinoma

Transarterial chemoembolization (TACE) and transarterial radioembolization (TARE) treatment to hepatocellular carcinoma (HCC) are effective tools to control tumor growth, prolong survival, palliate symptoms, and improve quality of life for patients with intermediate-stage HCC. Nevertheless, there is high variability of local HCC responses to locoregional therapies; therefore, better and personalized prediction of tumor response to TACE is necessary for management of patients with HCC, especially when these modalities of treatment are used to bridge patients for liver transplant. Here, we investigated differential expression of hepatic cancer stem cell and hypoxia in residual HCC after TACE treatment in comparison with TARE. A publicly available gene data set was screened for differentially expressed genes (DEGs) in TACE_Response compared with TACE_Non-response HCC. Analysis of the GSE104580 data set displayed a total of 406 DEGs, including 196 down-regulated and 210 up-regulated DEGs. Of the 196 down-regulated DEGs, three hepatic cancer stem cell (CSC) markers and 11 hypoxia-related genes were identified. Immunohistochemical staining of hepatic CSC and hypoxia markers on explant liver tissues exhibited more intense positive staining of hepatic CSC markers (CD24, EpCAM) and hypoxia marker carbonic anhydrase 9 (CA9) in residual tumor nodule from patients with HCC treated with TACE compared with nontreated patients. Furthermore, Pearson's correlation analysis revealed the significant correlation between hepatic CSC markers and hypoxia marker, CA9. Conclusion: Hepatic CSC and hypoxia markers predict nonresponse to TACE and are differentially expressed in residual tumor after TACE compared with TARE. In the long term, TACE-induced hypoxia may select an aggressive HCC phenotype.

Metabolic Reprogramming and Lipophagy Mediates Survival of Ascites Derived Metastatic Ovarian Cancer Cells

OBJECTIVE

The study was aimed at understanding the survival of metastatic ovarian cancer spheroids in the malignant ascites microenvironment.

METHODS

All the assays were performed using aseptically collected patient samples. The cells were characterized for the expression of ovarian and cancer stem cell markers using immunocytochemistry. The presence of lipid in the primary metastatic cancer spheroids were confirmed by neutral fat staining using Oil Red-O and transmission electron microscopy. The mRNA expression of autophagy and lipid metabolism genes was analyzed using RT-PCR. The lipid content was analyzed using lipidomics analysis. Etomoxir and chloroquine were used to study the effect of inhibition of autophagy in the metastatic cells. The data were analyzed using appropriate statistical tools and a p-value <0.05 was considered to be statistically significant.

RESULTS

Metastatic ovarian cancer spheroids exhibit cancer stem like properties and undergo a metabolic reprogramming when they disseminate from the primary tumor. We report here the accumulation of numerous cytoplasmic lipid droplets and lipophagic vesicles in the metastatic cells in contrast to their primary tumors. In addition we also report that these cells depend on lipophagy for the utilization of lipids rather than the conventional lipolytic pathway. The lipidomics analysis data reveals that the metastatic cells possess high levels of unsaturated fatty acids. We have also reported the occurrence of distinct accumulation of multiple nuclei in the patient derived metastatic cells. Inhibition of beta-oxidation and autophagic machinery using etomoxir and chloroquine resulted in cell death suggesting a potential mode to suppress metastatic cancer cells.

CONCLUSION

Metabolic reprogramming is a characteristic feature of the metastatic ovarian cancer cells that are persisting in the malignant ascites. Targeting of the metastatic by gaining an insight into the various metabolic and molecular changes that occur in the metastatic niche provides a promising therapeutic approach in management of the disease.

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.

Identifying novel transcript biomarkers for hepatocellular carcinoma (HCC) using RNA-Seq datasets and machine learning

BACKGROUND

Hepatocellular carcinoma (HCC) is one of the leading causes of cancer death in the world owing to limitations in its prognosis. The current prognosis approaches include radiological examination and detection of serum biomarkers, however, both have limited efficiency and are ineffective in early prognosis. Due to such limitations, we propose to use RNA-Seq data for evaluating putative higher accuracy biomarkers at the transcript level that could help in early prognosis.

METHODS

To identify such potential transcript biomarkers, RNA-Seq data for healthy liver and various HCC cell models were subjected to five different machine learning algorithms: random forest, K-nearest neighbor, Naïve Bayes, support vector machine, and neural networks. Various metrics, namely sensitivity, specificity, MCC, informedness, and AUC-ROC (except for support vector machine) were evaluated. The algorithms that produced the highest values for all metrics were chosen to extract the top features that were subjected to recursive feature elimination. Through recursive feature elimination, the least number of features were obtained to differentiate between the healthy and HCC cell models.

RESULTS

From the metrics used, it is demonstrated that the efficiency of the known protein biomarkers for HCC is comparatively lower than complete transcriptomics data. Among the different machine learning algorithms, random forest and support vector machine demonstrated the best performance. Using recursive feature elimination on top features of random forest and support vector machine three transcripts were selected that had an accuracy of 0.97 and kappa of 0.93. Of the three transcripts, two were protein coding (PARP2-202 and SPON2-203) and one was a non-coding transcript (CYREN-211). Lastly, we demonstrated that these three selected transcripts outperformed randomly taken three transcripts (15,000 combinations), hence were not chance findings, and could then be an interesting candidate for new HCC biomarker development.

CONCLUSION

Using RNA-Seq data combined with machine learning approaches can aid in finding novel transcript biomarkers. The three biomarkers identified: PARP2-202, SPON2-203, and CYREN-211, presented the highest accuracy among all other transcripts in differentiating the healthy and HCC cell models. The machine learning pipeline developed in this study can be used for any RNA-Seq dataset to find novel transcript biomarkers. Code: www.github.com/rajinder4489/ML_biomarkers.

MAT2A Localization and Its Independently Prognostic Relevance in Breast Cancer Patients

(1) Background: methionine cycle is not only essential for cancer cell proliferation but is also critical for metabolic reprogramming, a cancer hallmark. Hepatic and extrahepatic tissues methionine adenosyltransferases (MATs) are products of two genes, MAT1A and MAT2A that catalyze the formation of S-adenosylmethionine (SAM), the principal biological methyl donor. Glycine N-methyltransferase (GNMT) further utilizes SAM for sarcosine formation, thus it regulates the ratio of SAM:S-adenosylhomocysteine (SAH). (2) Methods: by analyzing the TCGA/GTEx datasets available within GEPIA2, we discovered that breast cancer patients with higher MAT2A had worse survival rate (p = 0.0057). Protein expression pattern of MAT1AA, MAT2A and GNMT were investigated in the tissue microarray in our own cohort (n = 252) by immunohistochemistry. MAT2A C/N expression ratio and cell invasion activity were further investigated in a panel of breast cancer cell lines. (3) Results: GNMT and MAT1A were detected in the cytoplasm, whereas MAT2A showed both cytoplasmic and nuclear immunoreactivity. Neither GNMT nor MAT1A protein expression was associated with patient survival rate in our cohort. Kaplan–Meier survival curves showed that a higher cytoplasmic/nuclear (C/N) MAT2A protein expression ratio correlated with poor overall survival (5 year survival rate: 93.7% vs. 83.3%, C/N ratio ≥ 1.0 vs. C/N ratio < 1.0, log-rank p = 0.004). Accordingly, a MAT2A C/N expression ratio ≥ 1.0 was determined as an independent risk factor by Cox regression analysis (hazard ratio = 2.771, p = 0.018, n = 252). In vitro studies found that breast cancer cell lines with a higher MAT2A C/N ratio were more invasive. (4) Conclusions: the subcellular localization of MAT2A may affect its functions, and elevated MAT2A C/N ratio in breast cancer cells is associated with increased invasiveness. MAT2A C/N expression ratio determined by IHC staining could serve as a novel independent prognostic marker for breast cancer.

CD133 Expression in the Nucleus Is Associated with Endometrial Carcinoma Staging and Tumor Angioinvasion

BACKGROUND

(1) Endometrial cancer is one of the most common cancers affecting women, with a growing incidence. To better understand the different behaviors associated with endometrial cancer, it is necessary to understand the changes that occur at a molecular level. CD133 is one of the factors that regulate tumor progression, which is primarily known as the transmembrane glycoprotein associated with tumor progression or cancer stem cells. The aim of our study was to assess the impact of subcellular CD133 expression on the clinical course of endometrial cancer. (2) Methods: CD133 expression in the plasma membrane, nucleus, and cytoplasm was assessed by immunohistochemical staining in a group of 64 patients with endometrial cancer representing FIGO I-IV stages, grades 1-3 and accounting for tumor angioinvasion. (3) Results: Nuclear localization of CD133 expression was increased in FIGO IB-IV stages compared to FIGO IA. Furthermore, CD133 expression in the nucleus and plasma membrane is positively and negatively associated with a higher grade of endometrial cancer and angioinvasion, respectively. (4) Conclusions: Our findings suggest that positive nuclear CD133 expression in the tumor may be related to a less favorable prognosis of endometrial carcinoma patients and has emerged as a useful biomarker of a high-risk group.

The role of CD133 in hepatocellular carcinoma

Cancer stem cells (CSCs) represent a small subpopulation of cells found within tumors that exhibit properties of self-renewal, like normal stem cells. CSCs have been defined as a crucial factor involved in driving cancer relapse, chemoresistance and metastasis. Prominin-1 (CD133) is one of the most well-characterized markers of CSCs in various tumor types, including hepatocellular carcinoma (HCC). CD133+ cells have been demonstrated to be involved in metastasis, tumorigenesis, tumor recurrence, and resistance to treatment in HCC. CD133-related clinical prognosis prediction, and targeted therapy have highlighted the clinical significance of CD133 in HCC. However, there remains controversy over the role of CD133 in experimental and clinical research involving HCC. In this article, we summarize the fundamental cell biology of CD133 in HCC cells and discuss the important characteristics of CD133+ in HCC cells. Furthermore, the prognostic value of CD133, and therapeutic strategies for its targeting in HCC, is also reviewed.

A pan-cancer perspective analysis reveals the opposite prognostic significance of CD133 in lower grade glioma and papillary renal cell carcinoma

CD133 is a valuable prognostic marker in multiple types of cancer. However, the expression, methylation levels, and prognostic relevance of CD133 have not been evaluated in a pan-cancer perspective. The expression and methylation levels of CD133 across different types of cancer were determined using The Cancer Genome Atlas (TCGA) dataset. Univariate cox regression and Kaplan-Meier survival were used to determine the prognostic significance of CD133 expression and methylation. CD133 was highly expressed in papillary renal cell carcinoma (PRCC) or pancreatic adenocarcinoma (PAAD). Correspondingly, PAAD and PRCC had low CD133 methylation levels. Through pan-cancer perspective analysis, we found that CD133 high expression was a poor prognostic factor in lower grade glioma (LGG), while, CD133 high expression was a good prognostic factor in PRCC. Moreover, genes positively correlated with CD133 expression were associated with the poor clinical outcomes of LGG. In PRCC, genes negatively correlated with CD133 expression were correlated with the poor overall survival. Furthermore, CD133 expression levels were highly correlated with the CD133 methylation levels in LGG or PRCC. Correspondingly, CD133 hypermethylation was a good prognostic factor in LGG. On the contrary, CD133 hypomethylation was a good prognostic factor in PRCC. We also found that CD133 was highly expressed and hypomethylated in wild type IDH subgroup of LGG. CD133 was highly expressed and hypomethylated in low stages and type1 of PRCC. CD133 high expression and hypomethylation were bad prognostic factors in LGG, while, CD133 high expression and hypomethylation were good prognostic factors in PRCC.

Prominin-1-Radixin axis controls hepatic gluconeogenesis by regulating PKA activity

Prominin-1 (Prom1) is a major cell surface marker of cancer stem cells, but its physiological functions in the liver have not been elucidated. We analyzed the levels of mRNA transcripts in serum-starved primary WT (Prom1+/+ ) and KO (Prom1-/- ) mouse hepatocytes using RNA sequencing (RNA-seq) data, and found that CREB target genes were downregulated. This initial observation led us to determine that Prom1 deficiency inhibited cAMP response element-binding protein (CREB) activation and gluconeogenesis, but not cyclic AMP (cAMP) accumulation, in glucagon-, epinephrine-, or forskolin-treated liver tissues and primary hepatocytes, and mitigated glucagon-induced hyperglycemia. Because Prom1 interacted with radixin, Prom1 deficiency prevented radixin from localizing to the plasma membrane. Moreover, systemic adenoviral knockdown of radixin inhibited CREB activation and gluconeogenesis in glucagon-treated liver tissues and primary hepatocytes, and mitigated glucagon-elicited hyperglycemia. Based on these results, we conclude that Prom1 regulates hepatic PKA signaling via radixin functioning as an A kinase-anchored protein (AKAP).

SNP rs2240688 in CD133 gene on susceptibility and clinicopathological features of hepatocellular carcinoma

Background

CD133 is one of the important cancer stem cells (CSCs) markers of hepatocellular carcinoma (HCC). The aim of this study was to explore the relationship between CD133 single-nucleotide polymorphisms (SNPs) and risk factors associated with HCC susceptibility and clinicopathological features in HCC cases and healthy controls from the Guangxi region of southern China.

Methods

A case control study was conducted, including 565 HCC patients and 561 control subjects. The genotyping of rs2240688 was performed using the SNaPshot method. Unconditional logistic regression was used to correct for gender, age, and other confounding factors. Odds ratio (OR) and its 95% confidence interval (CI) were calculated to analyze the relationship between allele and genotype frequency and the risk of HCC.

Results

The distribution frequencies of CD133 alleles and genotypes in the HCC case group and the control group were statistically significant (P<0.05). The CA heterozygous (P=0.003, OR =1.463, 95% CI: 1.134–1.887) and CC homozygous genotypes (P=0.036, OR =1.910, 95% CI: 1.044–3.493), as well as C carrier status (P=0.004, OR =1.465, 95% CI: 1.136–1.889) and C alleles (P=0.004, OR =1.465, 95% CI: 1.136–1.889), were associated with an increased risk of HCC. Additionally, in the subgroup analysis of CD133 rs2240688 polymorphism and clinical characteristics, the results showed that the genotype distribution of CD133 rs2240688 was significantly different in genotype distribution of metastasis and alanine aminotransferase (ALT).

Conclusions

the expression of miRNA binding site rs2240688 of tumor stem cell marker gene CD133 in HCC may be a promising marker for the prediction of HCC, but larger studies are still needed.

Targeting Liver Cancer Stem Cells: An Alternative Therapeutic Approach for Liver Cancer

The first report of cancer stem cell (CSC) from Bruce et al. has demonstrated the relatively rare population of stem-like cells in acute myeloid leukemia (AML). The discovery of leukemic CSCs prompted further identification of CSCs in multiple types of solid tumor. Recently, extensive research has attempted to identity CSCs in multiple types of solid tumors in the brain, colon, head and neck, liver, and lung. Based on these studies, we hypothesize that the initiation and progression of most malignant tumors rely largely on the CSC population. Recent studies indicated that stem cell-related markers or signaling pathways, such as aldehyde dehydrogenase (ALDH), CD133, epithelial cell adhesion molecule (EpCAM), Wnt/β-catenin signaling, and Notch signaling, contribute to the initiation and progression of various liver cancer types. Importantly, CSCs are markedly resistant to conventional therapeutic approaches and current targeted therapeutics. Therefore, it is believed that selectively targeting specific markers and/or signaling pathways of hepatic CSCs is an effective therapeutic strategy for treating chemotherapy-resistant liver cancer. Here, we provide an overview of the current knowledge on the hepatic CSC hypothesis and discuss the specific surface markers and critical signaling pathways involved in the development and maintenance of hepatic CSC subpopulations.

Evaluation of Sialyl-Lactotetra as a Marker for Epithelial Ovarian Tumors

Ovarian carcinoma is a heterogeneous disease with distinct molecular and histological profiles, ranging from low grade atypia to highly aggressive tumors associated with a poor prognosis. In the present study, glycosphingolipids were isolated from human high-grade serous ovarian carcinoma, whereby the novel stem cell marker Sialyl-lactotetra (S-Lc4) was characterized in two out of three cases. The presence and level of S-Lc4 was further evaluated immunohistochemically in a cohort of patients with ovarian tumors ranging from benign lesions to high grade serous carcinoma (n = 478). Its expression was assessed in association with tumor grade, stage, histology, and survival. The data showed that S-Lc4 is most common and highly expressed in borderline type tumors and carcinomas with low levels of aggressiveness, such as mucinous, endometrioid, and low grade serous. Accordingly, S-Lc4-positivity was associated with better disease-free survival. The expression of S-Lc4 was seemingly associated with lineage continuity and could be traced from premalignant lesions to carcinoma, suggesting inheritance by a stem cell lineage that gives rise to generally indolent tumors.

Cancer Stem Cells-Origins and Biomarkers: Perspectives for Targeted Personalized Therapies

The use of biomarkers in diagnosis, therapy and prognosis has gained increasing interest over the last decades. In particular, the analysis of biomarkers in cancer patients within the pre- and post-therapeutic period is required to identify several types of cells, which carry a risk for a disease progression and subsequent post-therapeutic relapse. Cancer stem cells (CSCs) are a subpopulation of tumor cells that can drive tumor initiation and can cause relapses. At the time point of tumor initiation, CSCs originate from either differentiated cells or adult tissue resident stem cells. Due to their importance, several biomarkers that characterize CSCs have been identified and correlated to diagnosis, therapy and prognosis. However, CSCs have been shown to display a high plasticity, which changes their phenotypic and functional appearance. Such changes are induced by chemo- and radiotherapeutics as well as senescent tumor cells, which cause alterations in the tumor microenvironment. Induction of senescence causes tumor shrinkage by modulating an anti-tumorigenic environment in which tumor cells undergo growth arrest and immune cells are attracted. Besides these positive effects after therapy, senescence can also have negative effects displayed post-therapeutically. These unfavorable effects can directly promote cancer stemness by increasing CSC plasticity phenotypes, by activating stemness pathways in non-CSCs, as well as by promoting senescence escape and subsequent activation of stemness pathways. At the end, all these effects can lead to tumor relapse and metastasis. This review provides an overview of the most frequently used CSC markers and their implementation as biomarkers by focussing on deadliest solid (lung, stomach, liver, breast and colorectal cancers) and hematological (acute myeloid leukemia, chronic myeloid leukemia) cancers. Furthermore, it gives examples on how the CSC markers might be influenced by therapeutics, such as chemo- and radiotherapy, and the tumor microenvironment. It points out, that it is crucial to identify and monitor residual CSCs, senescent tumor cells, and the pro-tumorigenic senescence-associated secretory phenotype in a therapy follow-up using specific biomarkers. As a future perspective, a targeted immune-mediated strategy using chimeric antigen receptor based approaches for the removal of remaining chemotherapy-resistant cells as well as CSCs in a personalized therapeutic approach are discussed.

The Rational Development of CD133-Targeting Immunotherapies for Glioblastoma

CD133 marks self-renewing cancer stem cells (CSCs) in a variety of solid tumors, and CD133+ tumor-initiating cells are known markers of chemo- and radio-resistance in multiple aggressive cancers, including glioblastoma (GBM), that may drive intra-tumoral heterogeneity. Here, we report three immunotherapeutic modalities based on a human anti-CD133 antibody fragment that targets a unique epitope present in glycosylated and non-glycosylated CD133 and studied their effects on targeting CD133+ cells in patient-derived models of GBM. We generated an immunoglobulin G (IgG) (RW03-IgG), a dual-antigen T cell engager (DATE), and a CD133-specific chimeric antigen receptor T cell (CAR-T): CART133. All three showed activity against patient-derived CD133+ GBM cells, and CART133 cells demonstrated superior efficacy in patient-derived GBM xenograft models without causing adverse effects on normal CD133+ hematopoietic stem cells in humanized CD34+ mice. Thus, CART133 cells may be a therapeutically tractable strategy to target CD133+ CSCs in human GBM or other treatment-resistant primary cancers.

Cancer Stem Cell Functions in Hepatocellular Carcinoma and Comprehensive Therapeutic Strategies

Hepatocellular carcinoma (HCC) is a significant cause of cancer-related mortality owing to resistance to traditional treatments and tumor recurrence after therapy, which leads to poor therapeutic outcomes. Cancer stem cells (CSC) are a small subset of tumor cells with the capability to influence self-renewal, differentiation, and tumorigenesis. A number of surface markers for liver cancer stem cell (LCSC) subpopulations (EpCAM, CD133, CD44, CD13, CD90, OV-6, CD47, and side populations) in HCC have been identified. LCSCs play critical roles in regulating HCC stemness, self-renewal, tumorigenicity, metastasis, recurrence, and therapeutic resistance via genetic mutations, epigenetic disruption, signaling pathway dysregulation, or alterations microenvironment. Accumulating studies have shown that biomarkers for LCSCs contribute to diagnosis and prognosis prediction of HCC, supporting their utility in clinical management and development of therapeutic strategies. Preclinical and clinical analyses of therapeutic approaches for HCC using small molecule inhibitors, oncolytic measles viruses, and anti-surface marker antibodies have demonstrated selective, efficient, and safe targeting of LCSC populations. The current review focuses on recent reports on the influence of LCSCs on HCC stemness, tumorigenesis, and multiple drug resistance (MDR), along with LCSC-targeted therapeutic strategies for HCC.

Cancer Stem Cells: A Potential Breakthrough in HCC-Targeted Therapy

Cancer stem cells (CSCs) are subpopulations of cells with stem cell characteristics that produce both cancerous and non-tumorigenic cells in tumor tissues. The literature reports that CSCs are closely related to the development of hepatocellular carcinoma (HCC) and promote the malignant features of HCC such as high invasion, drug resistance, easy recurrence, easy metastasis, and poor prognosis. This review discusses the origin, molecular, and biological features, functions, and applications of CSCs in HCC in recent years; the goal is to clarify the importance of CSCs in treatment and explore their potential value in HCC-targeted therapy.

Overexpression of Epcam and CD133 Correlates with Poor Prognosis in Dual-phenotype Hepatocellular Carcinoma

Background: Dual-phenotype hepatocellular carcinoma (DPHCC) is associated with high rate of post-operative recurrence and low rate of survival, which may reflect the post-operative persistence of cancer stem cells (CSCs). Here we explored the potential correlation between DPHCC and expression of CSCs markers. Methods: In this retrospective study, we included 19 patients with DPHCC and 61 patients with non-DPHCC treated in 2015 by liver resection. Paraffin-embedded tumor tissue specimens were analyzed using immunohistochemistry as well as immunofluorescence double-staining. Rates of recurrence-free survival and overall survival were compared between the two groups using the Kaplan-Meier method, and expression of the CSC markers CD133, CD90, and EpCAM were compared using real-time quantitative PCR and western blotting. Results: Overall survival rates were significantly lower for patients with DPHCC than patients with non-DPHCC at 1 year (78.9% vs 93.4%), 2 years (52.6% vs 72.1%), and 3 years (42.1% vs 67.2%) (P = 0.019). Multivariate Cox proportional hazard modeling identified CK19 positivity (P = 0.016) and multiple nodules (P = 0.023) as independent predictors of poor recurrence-free survival. Independent predictors of poor overall survival were CK19 positivity (P = 0.032), Barcelona Clinic Liver Cancer stage C (P = 0.025) and carbohydrate antigen 19-9 (CA19-9) >37 ng/ml (P = 0.016). Expression of CD133 and EpCAM mRNA and protein were significantly higher in DPHCC tissue than non-DPHCC tissue, while CD90 expression was similar between the groups. Conclusions: These results suggest that DPHCC is associated with significantly lower overall survival than non-DPHCC, and that the poor prognosis among DPHCC patients may be related to the presence of CSCs expressing CD133 and EpCAM.

Clinical implications of cancer stem cells in digestive cancers: acquisition of stemness and prognostic impact

Digestive system cancers are the most frequent cancers worldwide and often associated with poor prognosis because of their invasive and metastatic characteristics. Recent studies have found that the plasticity of cancer cells can impart cancer stem-like properties via the epithelial-mesenchymal transition (EMT). Cancer stem-like properties such as tumor initiation are integral to the formation of metastasis, which is the main cause of poor prognosis. Numerous markers of cancer stem cells (CSCs) have been identified in many types of cancer. Therefore, CSCs, via their stem cell-like functions, may play an important role in prognosis after surgery. While several reports have described prognostic analysis using CSC markers, few reviews have summarized CSCs and their association with prognosis. Herein, we review the prognostic potential of eight CSC markers, CD133, CD44, CD90, ALDH1A1, EPCAM, SOX2, SOX9, and LGR5, in digestive cancers including those of the pancreas, colon, liver, gastric, and esophagus.

Hypoxia induced Sonic Hedgehog signaling regulates cancer stemness, epithelial-to-mesenchymal transition and invasion in cholangiocarcinoma

Aberrant activation of Sonic Hedgehog (SHH) pathway has been implicated in a variety of cancers including cholangiocarcinoma (CC); however, the influencing factors are still unknown. Additionally, intratumoral hypoxia is known to contribute towards therapeutic resistance through modulatory effects on various pathways. In this study, we investigated the relationship between hypoxia and SHH pathway activation and the effect of this interplay on cancer stemness and epithelial-to- mesenchymal transition (EMT) during cholangiocarcinogenesis. Hypoxia promoted SHH pathway activation, evidenced by upregulated SHH and SMO levels, and enhanced glioma-associated oncogene homolog 1 (GLI1) nuclear translocation; whereas silencing of HIF-1α impaired SHH upregulation. Hypoxia also enhanced the expression of cancer stem cell (CSC) transcription factors (NANOG, Oct4, SOX2), CD133 and EMT markers (N-cadherin, Vimentin), thereby supporting invasion. Cyclopamine treatment suppressed hypoxia induced SHH pathway activation, consequently reducing invasiveness by downregulating the expression of CSC transcription factors, CD133 and EMT. Cyclopamine induced apoptosis in CC cells under hypoxia, suggesting that hypoxia induced activation of SHH pathway has modulatory effects on CC progression. Therefore, SHH signaling is proposed as a target for CC treatment, which is refractory to standard chemotherapy.

Aquaporin 3 maintains the stemness of CD133+ hepatocellular carcinoma cells by activating STAT3

An increasing interest in liver cancer stemness arises owing to its aggressive behavior and poor prognosis. CD133, a widely known liver cancer stem cell marker, plays critical roles in the maintenance of liver cancer stemness. Thus, exploring the regulatory mechanism of CD133 expression is significant. In the present study, we proved the carcinogenesis roles of aquaporin 3 (AQP3) in hepatocellular carcinoma (HCC) and demonstrated that AQP3 promotes the stem cell-like properties of hepatoma cells by regulating CD133 expression. In addition, AQP3 promoted the stimulation and nuclear translocation of signal transducer and activator of transcription 3 (STAT3) with a subsequent increase in the level of CD133 promoter-acetylated histone H3. This phenomenon accelerated CD133 transcription. Next, whether AQP3 acted as an oncogenic gene in HCC and maintained the stemness of CD133+ hepatoma cells were elucidated; also, a novel mechanism underlying the AQP3/STAT3/CD133 pathway in HCC was deduced.

Recycling endosomal CD133 functions as an inhibitor of autophagy at the pericentrosomal region

CD133 is a transmembranous protein that mainly localises to the plasma membrane in haematopoietic and neural stem cells as well as cancer stem cells. Although CD133 also localises to the cytoplasm, the mechanism of action and function of cytoplasmic CD133 currently remain unknown. We herein demonstrated that when Src family kinase activity is weak, CD133 interacts with HDAC6 and is transported to the pericentrosomal region after internalization and endosome formation via the dynein-based traffic system. Pericentrosomal CD133 is then recycled to the plasma membrane via recycling endosomes. At the pericentrosomal region, endosomal CD133 captures GABARAP, an initiator of autophagy, and inhibits GABARAP-mediated ULK1 activation and the subsequent initiation of autophagy. Furthermore, pericentrosomal CD133 suppresses cell differentiation, such as primary cilium formation and neurite outgrowth, by inhibiting autophagy. Thus, the present results provide evidence to suggest that pericentrosomal CD133 has the unique property of maintaining the undifferentiated status of cells by inhibiting autophagy.

Heterogeneity of Hepatic Cancer Stem Cells

Hepatocellular carcinoma (HCC) is one of the most common cancers with high mortality rate. It is a heterogeneous cancer with diverse inter- and intra-heterogeneity, also in terms of histology, prognosis, and molecular profiles. A rapidly growing evidence has demonstrated that some HCCs, if not all, were caused by the activation of the cancer stem cells (CSC), a small population within the cancer that is responsible for the initiation and maintenance of cancer growth. Until now, various populations of hepatic CSC with more than ten different phenotypical protein markers, such as CD133, CD90, EpCAM, CD24, and CD13, have been identified and validated in xenotransplantation models. They are associated with risk factors, prognosis, chemo-resistance, and metastasis. This chapter summarizes available data on different hepatic CSC markers for the development of potential future therapy.

Cancer stem cells in hepatocellular carcinoma: an overview and promising therapeutic strategies

The poor clinical outcome of hepatocellular carcinoma (HCC) patients is ascribed to the resistance of HCC cells to traditional treatments and tumor recurrence after curative therapies. Cancer stem cells (CSCs) have been identified as a small subset of cancer cells which have high capacity for self-renewal, differentiation and tumorigenesis. Recent advances in the field of liver CSCs (LCSCs) have enabled the identification of CSC surface markers and the isolation of CSC subpopulations from HCC cells. Given their central role in cancer initiation, metastasis, recurrence and therapeutic resistance, LCSCs constitute a therapeutic opportunity to achieve cure and prevent relapse of HCC. Thus, it is necessary to develop therapeutic strategies to selectively and efficiently target LCSCs. Small molecular inhibitors targeting the core stemness signaling pathways have been actively pursued and evaluated in preclinical and clinical studies. Other alternative therapeutic strategies include targeting LCSC surface markers, interrupting the CSC microenvironment, and altering the epigenetic state. In this review, we summarize the properties of CSCs in HCC and discuss novel therapeutic strategies that can be used to target LCSCs.

4Mu Decreases CD47 Expression on Hepatic Cancer Stem Cells and Primes a Potent Antitumor T Cell Response Induced by Interleukin-12

The tumor microenvironment (TME) represents a complex interplay between different cellular components, including tumor cells and cancer stem cells (CSCs), with the associated stroma; such interaction promotes tumor immune escape and sustains tumor growth. Several experimental approaches for cancer therapy are focused on TME remodeling, resulting in increased antitumor effects. We previously demonstrated that the hyaluronan synthesis inhibitor 4-methylumbelliferone (4Mu) decreases liver fibrosis and induces antitumor activity in hepatocellular carcinoma (HCC). In this work, 4Mu, in combination with an adenovirus encoding interleukin-12 genes (AdIL-12), elicited a potent antitumor effect and significantly prolonged animal survival (p < 0.05) in an orthotopic HCC model established in fibrotic livers. In assessing the presence of CSCs, we found reduced mRNA levels of CD133⁺, CD90⁺, EpCAM⁺, CD44⁺, and CD13⁺ CSC markers within HCC tumors (p < 0.01). Additionally, 4Mu downregulated the expression of the CSC marker CD47⁺ on HCC cells, promoted phagocytosis by antigen-presenting cells, and, combined with Ad-IL12, elicited a potent cytotoxic-specific T cell response. Finally, animal survival was increased when CD133^low HCC cells, generated upon 4Mu treatment, were injected in a metastatic HCC model. In conclusion, the combined strategy ameliorates HCC aggressiveness by targeting CSCs and as a result of the induction of anticancer immunity.

Neuroblastoma Origin and Therapeutic Targets for Immunotherapy

Neuroblastoma is a pediatric solid cancer of heterogeneous clinical behavior. The unique features of this type of cancer frequently hamper the process of determining clinical presentation and predicting therapy effectiveness. The tumor can spontaneously regress without treatment or actively develop and give rise to metastases despite aggressive multimodal therapy. In recent years, immunotherapy has become one of the most promising approaches to the treatment of neuroblastoma. Still, only one drug for targeted immunotherapy of neuroblastoma, chimeric monoclonal GD2-specific antibodies, is used in the clinic today, and its application has significant limitations. In this regard, the development of effective and safe GD2-targeted immunotherapies and analysis of other potential molecular targets for the treatment of neuroblastoma represents an important and topical task. The review summarizes biological characteristics of the origin and development of neuroblastoma and outlines molecular markers of neuroblastoma and modern immunotherapy approaches directed towards these markers.

The role of CD133 in cancer: a concise review

Despite the abundant ongoing research efforts, cancer remains one of the most challenging diseases to treat globally. Due to the heterogenous nature of cancer, one of the major clinical challenges in therapeutic development is the cancer’s ability to develop resistance. It has been hypothesized that cancer stem cells are the cause for this resistance, and targeting them will lead to tumor regression. A pentaspan transmembrane glycoprotein, CD133 has been suggested to mark cancer stem cells in various tumor types, however, the accuracy of CD133 as a cancer stem cell biomarker has been highly controversial. There are numerous speculations for this, including differences in cell culture conditions, poor in vivo assays, and the inability of current antibodies to detect CD133 variants and deglycosylated epitopes. This review summarizes the most recent and relevant research regarding the controversies surrounding CD133 as a normal stem cell and cancer stem cell biomarker. Additionally, it aims to establish the overall clinical significance of CD133 in cancer. Recent clinical studies have shown that high expression of CD133 in tumors has been indicated as a prognostic marker of disease progression. As such, a spectrum of immunotherapeutic strategies have been developed to target these CD133^pos cells with the goal of translation into the clinic. This review compiles the current therapeutic strategies targeting CD133 and discusses their prognostic potential in various cancer subtypes.

Nuclear CD133 expression predicts poor prognosis for hepatocellular carcinoma

Cancer stem cells (CSCs) are responsible for cancer recurrence and metastasis and are related to poor prognosis in patients with hepatocellular carcinoma (HCC). CD133 is one of the most commonly used CSC markers. In this study, expression and the biological significance of CSC marker CD133 was evaluated in HCC, at mRNA and protein levels. We demonstrate that both mRNA and protein levels of CD133 are significantly elevated in HCC relative to that in adjacent non-cancerous tissue based on bioinformatics and immunohistochemical analysis, respectively (P < 0.01). Intriguingly, we detected nuclear distribution of CD133 and found that nuclear CD133 expression was indicative of poor patient prognosis (median survival 12 months versus 34.5 months) (Log-Rank, P = 0.0258). Meanwhile, our findings suggest that nuclear CD133 expression is positively correlated with tumor size and serves as an independent prognostic factor for HCC after surgical resection (HR = 0.564, 95% CI 0.313-1.018, P = 0.057). Nuclear CD133 expression can potentially serve as a biomarker for clinical diagnosis and prognosis of HCC.

Prominin-1/CD133: Lipid Raft Association, Detergent Resistance, and Immunodetection

The cell surface antigen prominin‐1 (alias CD133) has gained enormous interest in the past 2 decades and given rise to debates as to its utility as a biological stem and cancer stem cell marker. Important and yet often overlooked knowledge that is pertinent to its physiological function has been generated in other systems given its more general expression beyond primitive cells. This article briefly discusses the importance of particular biochemical features of CD133 with relation to its association with membrane microdomains (lipid rafts) and proper immunodetection. It also draws attention toward the adequate use of detergents and caveats that may apply to the interpretation of the results generated. Stem Cells Translational Medicine2018;7:155–160