The stem cell marker CD133 associates with enhanced colony formation and cell motility in colorectal cancer

Production of a Ribosome-Displayed Mouse scFv Antibody Against CD133, Analysis of Its Molecular Docking, and Molecular Dynamic Simulations of Their Interactions

The pentaspan transmembrane glycoprotein CD133, prominin-1, is expressed in cancer stem cells in many tumors and is promising as a novel target for the delivery of cytotoxic drugs to cancer-initiating cells. In this study, we prepared a mouse library of single-chain variable fragment (scFv) antibodies using mRNAs isolated from mice immunized with the third extracellular domain of a recombinant CD133 (D-EC3). First, the scFvs were directly exposed to D-EC3 to select a new specific scFv with high affinity against CD133 using the ribosome display method. Then, the selected scFv was characterized by the indirect enzyme-linked immunosorbent assay (ELISA), immunocytochemistry (ICC), and in silico analyses included molecular docking and molecular dynamics simulations. Based on ELISA results, scFv 2 had a higher affinity for recombinant CD133, and it was considered for further analysis. Next, the immunocytochemistry and flow cytometry experiments confirmed that the obtained scFv could bind to the CD133 expressing HT-29 cells. Furthermore, the results of in silico analysis verified the ability of the scFv 2 antibody to bind and detect the D-EC3 antigen through key residues employed in antigen-antibody interactions. Our results suggest that ribosome display could be applied as a rapid and valid method for isolation of scFv with high affinity and specificity. Also, studying the mechanism of interaction between CD133's scFv and D-EC3 with two approaches of experimental and in silico analysis has potential importance for the design and development of antibody with improved properties.

Melatonin regulates cancer migration and stemness and enhances the anti-tumour effect of cisplatin

Melatonin, a lipophilic hormone released from the pineal gland, has oncostatic effects on various types of cancers. However, its cancer treatment potential needs to be improved by deciphering its corresponding mechanisms of action and optimising therapeutic strategy. In the present study, melatonin inhibited gastric cancer cell migration and soft agar colony formation. Magnetic-activated cell sorting was applied to isolate CD133⁺ cancer stem cells. Gene expression analysis showed that melatonin lowered the upregulation of LC3-II expression in CD133⁺ cells compared to CD133^- cells. Several long non-coding RNAs and many components in the canonical Wnt signalling pathway were altered in melatonin-treated cells. In addition, knockdown of long non-coding RNA H19 enhanced the expression of pro-apoptotic genes, Bax and Bak, induced by melatonin treatment. Combinatorial treatment with melatonin and cisplatin was investigated to improve the applicability of melatonin as an anticancer therapy. Combinatorial treatment increased the apoptosis rate and induced G0/G1 cell cycle arrest. Melatonin can regulate migration and stemness in gastric cancer cells by modifying many signalling pathways. Combinatorial treatment with melatonin and cisplatin has the potential to improve the therapeutic efficacy of both.

Piperine and Celecoxib synergistically inhibit colon cancer cell proliferation via modulating Wnt/β-catenin signaling pathway

BACKGROUND

Celecoxib (CXB), a selective COX-2 inhibitor NSAID, has exhibited prominent anti-proliferative potential against numerous cancers. However, its low bioavailability and long term exposure related cardiovascular side effects, limit its clinical application. In order to overcome these limitations, natural bioactive compounds with lower toxicity profile are used in combination with therapeutic drugs. Therfore, in this study Piperine (PIP), a natural chemo-preventive agent possessing drug bioavailability enhancing properties, was considered to be used in combination with low doses of CXB.

PURPOSE

We hypothesized that the combination of PIP with CXB will have a synergistic anti-proliferative effect on colon cancer cells.

STUDY DESIGN

The potency of PIP and CXB alone and in combination was evaluated in HT-29 human colon adenocarcinoma cells and mechanism of growth inhibition was investigated by analyzing the players in apoptotic and Wnt/β-catenin signaling pathways.

METHODS

The effect of PIP on the oral bioavailability of CXB in mice was investigated using HPLC analysis. The study investigated the synergistic anti-proliferative effect of CXB and PIP on HT-29 cells and IEC-6 non-tumorigenic rat intestinal epithelial cells by SRB cell viability assay. Further, the cellular and molecular mechanism(s) involved in the anti-proliferative combinatorial effect was extensively explored in HT-29 cells by flow cytometry and western blotting. The in vivo efficacy of this combination was studied in CT26.WT tumor syngeneic Balb/c mice model.

RESULTS

PIP as a bioenhancer increased the oral bioavailability of CXB (129%). The IC50 of CXB and PIP were evaluated to select doses for combination treatment of HT-29 cells. The drug combinations having combination index (CI) less than 1 were screened using CompuSyn software. These combinations were significantly cytotoxic to HT-29 cells but IEC-6 were least effected. Further, the mechanism behind CXB and PIP mediated cell death was explored. The co-treatment led to reactive oxygen species generation, mitochondrial dysfunction, caspase activation and enhanced apoptosis in HT-29 cells. Additionally, the combination treatment synergistically modulated Wnt/β-catenin pathway, downregulated the stemness markers and boosted therapeutic response in CT26 syngeneic Balb/c mice.

CONCLUSION

The outcomes of the study suggests that combining CXB and PIP offers a novel approach for the treatment of colon cancer.

LSD1 as a Biomarker and the Outcome of Its Inhibitors in the Clinical Trial: The Therapy Opportunity in Tumor

Tumors are the foremost cause of death worldwide. As a result of that, there has been a significant enhancement in the investigation, treatment methods, and good maintenance practices on cancer. However, the sensitivity and specificity of a lot of tumor biomarkers are not adequate. Hence, it is of inordinate significance to ascertain novel biomarkers to forecast the prognosis and therapy targets for tumors. This review characterized LSD1 as a biomarker in different tumors. LSD1 inhibitors in clinical trials were also discussed. The recent pattern advocates that LSD1 is engaged at sauce chromatin zones linking with complexes of multi-protein having an exact DNA-binding transcription factor, establishing LSD1 as a favorable epigenetic target, and also gives a large selection of therapeutic targets to treat different tumors. This review sturdily backing the oncogenic probable of LSD1 in different tumors indicated that LSD1 levels can be used to monitor and identify different tumors and can be a useful biomarker of progression and fair diagnosis in tumor patients. The clinical trials showed that inhibitors of LSD1 have growing evidence of clinical efficacy which is very encouraging and promising. However, for some of the inhibitors such as GSK2879552, though selective, potent, and effective, its disease control was poor as the rate of adverse events (AEs) was high in tumor patients causing clinical trial termination, and continuation could not be supported by the risk-benefit profile. Therefore, we propose that, to attain excellent clinical results of inhibitors of LSD1, much attention is required in designing appropriate dosing regimens, developing in-depth in vitro/in vivo mechanistic works of LSD1 inhibitors, and developing inhibitors of LSD1 that are reversible, safe, potent, and selective which may offer safer profiles.

Farnesyl dimethyl chromanol targets colon cancer stem cells and prevents colorectal cancer metastasis

The activation and growth of tumour-initiating cells with stem-like properties in distant organs characterize colorectal cancer (CRC) growth and metastasis. Thus, inhibition of colon cancer stem cell (CCSC) growth holds promise for CRC growth and metastasis prevention. We and others have shown that farnesyl dimethyl chromanol (FDMC) inhibits cancer cell growth and induces apoptosis in vitro and in vivo. We provide the first demonstration that FDMC inhibits CCSC viability, survival, self-renewal (spheroid formation), pluripotent transcription factors (Nanog, Oct4, and Sox2) expression, organoids formation, and Wnt/β-catenin signalling, as evidenced by comparisons with vehicle-treated controls. In addition, FDMC inhibits CCSC migration, invasion, inflammation (NF-kB), angiogenesis (vascular endothelial growth factor, VEGF), and metastasis (MMP9), which are critical tumour metastasis processes. Moreover, FDMC induced apoptosis (TUNEL, Annexin V, cleaved caspase 3, and cleaved PARP) in CCSCs and CCSC-derived spheroids and organoids. Finally, in an orthotopic (cecum-injected CCSCs) xenograft metastasis model, we show that FDMC significantly retards CCSC-derived tumour growth (Ki-67); inhibits inflammation (NF-kB), angiogenesis (VEGF and CD31), and β-catenin signalling; and induces apoptosis (cleaved PARP) in tumour tissues and inhibits liver metastasis. In summary, our results demonstrate that FDMC inhibits the CCSC metastatic phenotype and thereby supports investigating its ability to prevent CRC metastases.

Cancer associated fibroblasts-derived exosomes contribute to radioresistance through promoting colorectal cancer stem cells phenotype

Radioresistance observed in patients with colorectal cancer (CRC) may be related to the presence of cancer stem cells (CSCs), but the underlying mechanism(s) remain unclear. Cancer-associated fibroblasts (CAFs) can regulate the stemness of cancer cells and tumor radiosensitivity. In addition, exosomes have been reported to modify treatment response by mediating cell-cell communication. In this study, we aimed to investigate whether exosomes derived from CAFs (CAF-exosomes) are involved in mediating resistance to radiotherapy in colorectal cancer and to explore the underlying mechanism. We found that CSCs were inherently resistant to cell death induced by radiotherapy. CAF-derived CM promoted clonogenicity and radioresistance of CRC cells. Further investigations revealed that exosomes isolated from CM induced the above effects whereas exosome-depleted CM (solution) was not able to induce clonogenicity and radioresistance. Finally, exosomes could activate transforming growth factor-β (TGF-β) signaling pathway and TGFβ1-neutralizing antibody inhibit this effect and decrease clonogenicity and expression levels of stemness genes. In conclusion,our findings suggest CAFs promote stemness of CRC cells and thus increase radiation resistance. Exosomes derived from CAFs play a crucial role through activating TGF-β signaling pathway in this process.

Knocking down LSD1 inhibits the stemness features of colorectal cancer stem cells

As a top leading cause of cancer death in many countries, colorectal cancer (CRC) has drawn increasing attention to the study of the pathological mechanism. According to the “cancer stem cell hypothesis”, malignancies originate from a small fraction of cancer cells that show self-renewal properties to initiate and sustain tumor growth and tumor metastasis. Therefore, these cancer stem cells (CSC) probably play important roles in tumor recurrence, metastasis, and drug resistance. Previous research reported that lysine-specific histone demethylase 1 (LSD1) maintains cancer stemness through up-regulating stemness markers SOX2 and OCT4. CD133 is believed to be the most robust surface marker for CRC stem cells, however the regulatory effect of LSD1 on stemness of CD133+ CRC has never been reported. In this study, our objectives included: 1) to isolate pure CD133+ and CD133− cells from SW620 cell line; 2) to investigate the effect of LSD1 on the characteristics of CD133+ stem cancer cells by knocking down the target gene. Results suggested that the SW620 cell line had both CD133+ and CD133− subsets. The CD133+ subset exhibited more CSC-like characteristics compared with the CD133− subset with higher viability, colony formation rate, migration and invasion rate, resistance to anti-cancer drugs, and apoptosis in vitro. The CD133+ also induced faster tumor formation and larger tumors in vivo. In the LSD1-knockdown CD133+ cells, the CSC-like characteristics had been all weakened. We conclude that LSD1 was important for CSCs to maintain their “stemness” features, which could be a potential therapeutic target of CRC.

CD133 suppression increases the sensitivity of prostate cancer cells to paclitaxel

One of the major barriers in cancer therapy is the resistance to conventional therapies and cancer stem cells (CSCs) are among the main causes of this problem. CD133 as a CSC marker displays stem cell-like properties, tumorigenic capacity, and drug resistance in various cancers. However, the molecular mechanism behind CD133 function in prostate cancer (PC) still remains unclear. This research aimed to illustrate the probabilistic mechanism of CD133-siRNA and paclitaxel in the reduction of chemoresistance in PC cells. To measure the cell viability, migratory capacity, CSCs properties, invasive potential, apoptosis and cell cycle progression of the cells, the MTT, wound healing, spheroid assay, colony formation assay, DAPI staining and flow cytometry assays were applied in the LNCaP cell line, respectively. Also, quantitative real-time PCR (qRT-PCR) and western blot method were used for measuring the expression of CD133 and the effects of CD133 silencing on the AKT/mTOR/c-myc axis and pro-metastatic genes expression. We showed that the CD133-siRNA considerably decreased the CD133 expression. Moreover, CD133-siRNA and paclitaxel treatment significantly decreased cell proliferation and also inhibited the ability of cell migration and invasion and reduced pro-metastatic genes expression. Additionally, we found that the simultaneous use of CD133-siRNA and paclitaxel increased the paclitaxel-induced apoptosis. Our results confirmed that CD133 silencing combined with paclitaxel synergistically could suppress cell migration, invasion, and proliferation and enhance the chemosensitivity compared with mono treatment. Therefore, CD133 silencing therapy could be viewed as a promising and efficient strategy in PC targeted therapies.

miR-194 Inhibits the Proliferation of SW620 Colon Cancer Stem Cells Through Downregulation of SSH2 Expression

Purpose

Colorectal cancer (CRC) stem cells are tumorigenic, capable of self-renewal, and resistant to therapy. Although the expression pattern and functions of micro RNA (miR)-194 in CRC cells have been widely investigated, little is known about its role in CRC stem cells. Therefore, the aim of this study was to investigate the potential role of miR-194 in CRC stem cells.

Materials and methods

CRC stem cells were isolated from the SW620 colon cancer cell line using microbeads. The expression levels of miR-194 and slingshot 2 (SSH2) in CRC stem cells were detected by RT-PCR and Western blot. A luciferase reporter assay was performed to confirm that miR-194 directly targets SSH2. Proliferation of CRC stem cells was examined by colony formation and MTT assays. Apoptosis in CRC stem cells was detected by cell cycle and apoptosis assays. The role of miR-194 in tumor growth was determined in vivo.

Results

Cells positive for CD44 and CD133 accounted for approximately 88.7% of the isolated population after microbead isolation. We reveal for the first time that miR-194 expression is decreased in CRC stem cells. Specifically, miR-194 is involved in inhibiting the proliferation of CRC stem cells and promoting CRC stem cell apoptosis by directly targeting SSH2. Furthermore, overexpression of miR-194 resulted in blocking the G1/S transition, the induction of cellular apoptotic process, thereby suppressing the malignant behaviors of CRC stem cells.

Conclusion

This study represents a novel characterization of miR-194 function in CRC stem cells, which may aid in the development of promising therapeutic strategies targeting CRC.

The oncogenic roles of 27-hydroxycholesterol in glioblastoma

Glioblastoma is the most frequent primary malignant brain tumor in adults. Oxysterols are oxidation products of cholesterol generated by enzymatic reactions. 27-hydroxycholesterol (27-HC), an oxysterol, is an abundant metabolite of cholesterol. 27-HC significantly accelerates mammary cancer growth, proliferation and progression in experimental models. However, to the best of our knowledge, the effect of 27-HC on glioblastoma has not been studied. Therefore, the present study aimed to determine the exact role of 27-HC in glioblastoma. The present study demonstrated that 27-HC promoted proliferation, epithelial to mesenchymal transition, colony formation, migration and invasion of U251 and U118 MG glioblastoma cells. Treatment with 27-HC was also associated with an increase in the formation of glioblastoma-initiating cells in U251 and U118 MG cell lines. Additionally, it was observed that high levels of 27-HC in glioblastoma tissues were associated with poor outcome in patients. In conclusion, 27-HC, a primary metabolite of cholesterol, may serve an important role in the progression of glioblastoma.

Simulated microgravity increases polyploid giant cancer cells and nuclear localization of YAP

Physical cues are vital in determining cellular fate in cancer. In vitro 3D culture do not replicate forces present in vivo. These forces including tumor interstitial fluid pressure and matrix stiffness behave as switches in differentiation and metastasis, which are intricate features of cancer stem cells (CSCs). Gravity determines the effect of these physical factors on cell fate and functions as evident from microgravity experiments on space and ground simulations. Here, we described the role of simulation of microgravity (SMG) using rotary cell culture system (RCCS) in increasing stemness in human colorectal cancer cell HCT116. We observed distinct features of cancer stem cells including CD133/CD44 dual positive cells and migration in SMG which was not altered by autophagy induction or inhibition. 3D and SMG increased autophagy, but the flux was staggered under SMG. Increased unique giant cancer cells housing complete nuclear localization of YAP were observed in SMG. This study highlights the role of microgravity in regulating stemness in CSC and importance of physical factors in determining the same.

The effects of adipose-derived stem cells on CD133-expressing bladder cancer cells

Mesenchymal stem cells (MSCs) hold great promise as therapeutic agents in regenerative medicine. They are also considered as a preferred cell source for urinary tract reconstruction. However, as MSCs exhibit affinity to tumor microenvironment, possible activation of tumor-initiating cells remains a major concern in the application of stem cell-based therapies for patients with a bladder cancer history. To analyze the influence of adipose-derived stem cells (ASCs) on bladder cancer cells with stem cell-like properties, we isolated CD133-positive bladder cancer cells and cultured them in conditioned medium from ASCs (ASC-CM). Our results showed that parental 5637 and HB-CLS-1 cells showed induced clonogenic potential when cultured in ASC-CM. Soluble mediators secreted by ASCs increased proliferation and viability of unsorted cells as well as CD133+ and CD133- subpopulations. Furthermore, incubation with ASC-CM modulated activation of intracellular signaling pathways. Soluble mediators secreted by ASCs increased phosphorylation of AKT1/2/3 (1.4-fold, P < 0.05), ERK1/2 (1.6-fold, P < 0.02), and p70 S6K (1.4-fold) in CD133+ cells isolated from 5637 cell line. In turn, decreased phosphorylation of those three proteins involved in PI3K/Akt and MAPK signaling was observed in CD133+ cells isolated from HB-CLS-1 cell line. Our results revealed that bladder cancer stem-like cells are responsive to signals from ASCs. Paracrine factors secreted by locally-delivered ASCs may, therefore, contribute to the modulation of signaling pathways involved in cancer progression, metastasis, and drug resistance.

Co-expression and prognostic significance of putative CSC markers CD44, CD133, wild-type EGFR and EGFRvIII in metastatic colorectal cancer

The presence of colorectal cancer stem cells (CSCs) have been associated with tumour initiation and resistance to therapy. This study investigated the co-expression and prognostic significance of the CSCs biomarkers CD44 and CD133 with wild-type EGFR (wtEGFR) and EGFRvIII in colorectal cancer (CRC). The expression of these biomarkers were determined in tumours from 70 patients with metastatic CRC by immunohistochemistry, and in a panel of human CRC cell lines, and their variants with acquired-resistance to EGFR inhibitors, by flow cytometry. The expression of CD44, CD133, wtEGFR and EGFRvIII were present in 17%, 23%, 26% and 13% of cases and the co-expression of CD44/CD133 with wtEGFR and EGFRvIII were present in 9% and 3% of the cases respectively. Only co-expression of CSCs/EGFRvIII (P = 0.037), and amphiregulin (P = 0.017) were associated with worse overall survival. Interestingly, disease-free survival was improved in BTC expressing patients (P = 0.025). In vitro CD133 expression and its co-expression with CD44 were associated with primary-resistance to irinotecan and acquired-resistance to anti-EGFR inhibitors respectively. Our results suggest co-expression of CSCs and EGFRvIII could be potential biomarkers of worse overall survival and resistance to therapy in patients with mCRC and warrants further validation in a larger cohort.

Tumidulin, a Lichen Secondary Metabolite, Decreases the Stemness Potential of Colorectal Cancer Cells

Lichens produce various unique chemicals that are used in the pharmaceutical industry. To screen for novel lichen secondary metabolites that inhibit the stemness potential of colorectal cancer cells, we tested acetone extracts of 11 lichen samples collected in Chile. Tumidulin, isolated from Niebla sp., reduced spheroid formation in CSC221, DLD1, and HT29 cells. In addition, mRNA expressions and protein levels of cancer stem markers aldehyde dehydrogenase-1 (ALDH1), cluster of differentiation 133 (CD133), CD44, Lgr5, and Musashi-1 were reduced after tumidulin treatment. Tumidulin decreased the transcriptional activity of the glioma-associated oncogene homolog zinc finger protein (Gli) promoter in reporter assays, and western blotting confirmed decreased Gli1, Gli2, and Smoothened (SMO) protein levels. Moreover, the tumidulin activity was not observed in the presence of Gli and SMO inhibitors. Together, these results demonstrate for the first time that tumidulin is a potent inhibitor of colorectal cancer cell stemness.

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.

MLF1 protein is a potential therapy target for lung adenocarcinoma

Myeloid leukemia factor 1 (MLF1) is a protein involved in myeloid cell differentiation which regulates the cell cycle and the expression of numerous genes. The role of MLF1 in hematologic cancers is well established; however, its role in lung adenocarcinoma is unknown. Here, we investigated the role of MLF1 in lung adenocarcinoma using a variety of cell lines along with patient samples to determine whether MLF1 plays a significant role in this devastating disease. Lung cancer cell lines (A549, H1975, HCC827, and NCI-H460) and primary lung tissue were used to assess the relative levels of MLF1 in lung adenocarcinoma. The lung adenocarcinoma cell line A549 was infected with a lentivirus to knockdown MLF1, and successful knockdown was confirmed by a real-time polymerase chain reaction (qPCR). Cell proliferation was assessed through fluorescence imaging and MTT assays. Cell cycle analysis was performed utilizing flow cytometry and formation of cell colonies evaluated microscopically. Proliferation of A549 cells was significantly inhibited in cells where MLF1 was silenced compared to controls. Cell cycle analysis indicated that cell cycle phases were not significantly changed upon the silencing of MLF1 in lung adenocarcinoma cells. A significant increase in apoptosis was observed in MLF1-knockdown cells, while a significant decrease in the number of cell colonies formed was observed in MLF1-knockdown cells compared to controls. In most, but not all, human lung adenocarcinoma tissue samples, MLF1 was upregulated. The results show that MLF1 promotes the proliferation and colony forming abilities of lung adenocarcinoma cells and significantly decreases apoptosis while having no impact on the cell cycle. Further studies with larger sample sizes are needed 1) to conclude whether human lung adenocarcinoma upregulates MLF1, 2) to reveal the mechanism of action for MLF1 in lung carcinogenesis and 3) to investigate MLF1 gene therapy for the treatment of lung adenocarcinoma.

Knockdown of miR-27a sensitizes colorectal cancer stem cells to TRAIL by promoting the formation of Apaf-1-caspase-9 complex

MicroRNAs have been proved to participate in multiple biological processes in cancers. For developing resistance to cytotoxic drug, cancer cells, especially the cancer stem cells, usually change their microRNA expression profile to survive in hostile environments. In the present study, we found that expression of microRNA-27a was increased in colorectal cancer stem cells. High level of microRNA-27a was indicated to induce the resistance to TNF-related apoptosis-inducing ligand (TRAIL). Knockdown of microRNA-27a resensitized colorectal cancer stem cells to TRAIL-induced cell death. Mechanically, the gene of Apaf-1, which is associated with the mitochondrial apoptosis, was demonstrated to be the target of microRNA-27a in colorectal cancer stem cells. Knockdown of microRNA-27a increased the expression level of Apaf-1, thus enhancing the formation of Apaf-1-caspase-9 complex and subsequently promoting the TRAIL-induced apoptosis in colorectal cancer stem cells. These findings suggested that knockdown of microRNA-27a in colorectal cancer stem cells by the specific antioligonucleotides was potential to reverse the chemoresistance to TRAIL. It may represent a novel therapeutic strategy for treating the colorectal cancer more effectively.

CD133-targeted delivery of self-assembled PEGylated carboxymethylcellulose-SN38 nanoparticles to colorectal cancer

Poor aqueous solubility of chemotherapeutics such as SN38 (7-ethyl-10-hydroxycamptothecin) and the associated systemic adverse effects are serious limitations of their clinical use. To improve the drug delivery efficiency of such compounds, they were covalently conjugated to hydrophilic macromolecular carriers that specifically deliver the drug moiety to the tumour cells. In the current study, we developed a PEGylated acetylated carboxymethylcellulose conjugate of SN38 which was covalently attached to an aptamer against a cancer stem cell marker, CD133. Then, the designed nanoplatform was used to specifically deliver SN38 to colorectal cancer cells. The results demonstrated that the synthesized conjugate was self-assembled to nanoparticles with 169 nm in size and poly dispersity index of 0.11. Besides, the targeted self-assembled nanoparticles could significantly enhance the cellular uptake by CD133-expressing HT29 cell line confirmed by fluorescent microscopy and flow cytometry. Moreover, our results revealed that the targeted self-assembled nanoconjugate exhibited significantly lower IC₅₀ in HT29 cells overexpressing CD133 compared to non-targeted self-assembled nanoconjugate. The promising data suggest that the prepared targeted self-assembled drug conjugate nanoparticles possess the potential to offer the desirable physicochemical properties thereby enhancing the solubility and the therapeutic index of poorly soluble cytotoxic agents.

Anti-EGFR antibody sensitizes colorectal cancer stem-like cells to Fluorouracil-induced apoptosis by affecting autophagy

Recent reports suggest that colorectal carcinoma (CRC) may be sustained by a small subpopulation of cells, termed cancer stem cells (CSCs), which have drug resistance properties as a key reason for chemotherapy failure. The epidermal growth factor receptor (EGFR) controls CRC initiation and progression. Monoclonal antibody against EGFR (cetuximab) has been used in treatment of several cancers. However, the effects of cetuximab on CSCs in the CRC chemotherapy remain unclear. Here, we studied the effects of cetuximab on the CSC-like cells in Fluorouracil (5-FU)-treated CRC cells. CSC-like cells were independently isolated from CRC cells using CD133, CD44 or EphB2-high as markers and confirmed by tumor sphere formation assay. We found that 5-FU increased the apoptotic death of CSC-like CRC cells. Co-application of cetuximab augmented the apoptotic death of CSC-like CRC cells by 5-FU, seemingly through inhibition of 5-FU-induced increases in cell autophagy in CSC-like CRC cells. Together, our data suggest that EGFR monoclonal antibody may sensitize CSC-like CRC cells to 5-FU-induced apoptosis by affecting autophagy.

CD133+CD24lo defines a 5-Fluorouracil-resistant colon cancer stem cell-like phenotype

The chemotherapeutic agent 5-Fluorouracil (5-FU) is the most commonly used drug for patients with advanced colon cancer. However, development of resistance to 5-FU is inevitable in almost all patients. The mechanism by which colon cancer develops 5-FU resistance is still unclear. One recently proposed theory is that cancer stem-like cells underlie colon cancer 5-FU resistance, but the phenotypes of 5-FU-resistant colon cancer stem cells are still controversial. We report here that 5-FU treatment selectively enriches a subset of CD133⁺ colon cancer cells in vitro. 5-FU chemotherapy also increases CD133⁺ tumor cells in human colon cancer patients. However, sorted CD133⁺ colon cancer cells exhibit no increased resistance to 5-FU, and CD133 levels exhibit no correlation with colon cancer patient survival or cancer recurrence. Genome-wide analysis of gene expression between sorted CD133⁺ colon cancer cells and 5-FU-selected colon cancer cells identifies 207 differentially expressed genes. CD24 is one of the genes whose expression level is lower in the CD133⁺ and 5-FU-resistant colon cancer cells as compared to CD133⁺ and 5-FU-sensitive colon cancer cells. Consequently, CD133⁺CD24^lo cells exhibit decreased sensitivity to 5-FU. Therefore, we determine that CD133⁺CD24^lo phenotype defines 5-FU-resistant human colon cancer stem cell-like cells.

GSK-3β inhibitor 6-bromo-indirubin-3'-oxime promotes both adhesive activity and drug resistance in colorectal cancer cells

Multi-targets inhibitor 6-bromo-indirubin-3'-oxime (BIO) has diverse biological effects on cancer cells. The key component of the β-catenin destruction complex glycogen synthase kinase 3β (GSK-3β), one of the major target for BIO, polyubiquitination and degradation of the main oncoprotein β-catenin in colorectal cancer (CRC). In the present study, we evaluated the effect of BIO on drug resistance and biological properties of CRC cells. Whole-genome transcriptional profiling revealed that differentially expressed genes were mainly centered on well-characterized signaling pathways including stem cell, cell adhesion and cell growth in BIO-treated CRC cells. BIO treatment downregulated migration and invasion abilities of CRC cells, accompanying with MMP-9 downregulated and E-cadherin upregulated CRC cells. BIO treatment decreased apoptosis induced by 5-Fu/DDP in CRC SW480 cells. In addition, BIO treatment reversed the 5-Fu-induced CD133+ cell downregulation trend in CRC SW620 cells. After incubation with BIO, the expression levels of EpCAM, TERT and DCAMKL-1 proteins were upregulated in CRC cells. BIO treatment downregulated the activity of GSK-3β, upregulated and transported β-catenin to the nucleus in CRC cells. Our findings reveal that BIO treatment upregulated stemness, adhesive and chemoresistance of CRC cells. GSK-3β inhibition and WNT/β-catenin activation by BIO, may partly result in the biological behavior alterations in CRC cells.

Cancer stem cell marker glycosylation: Nature, function and significance

Glycans are essential for the maintenance of normal biological function, with alterations in glycan expression being a hallmark of cancer. Cancer stem cells (CSCs) are a subset of cells within a tumour capable of self-renewal, cellular differentiation and resistances to conventional therapies. As is the case with stem cells, marker proteins present on the cell surface are frequently used to identify and enrich CSCs, with the expression of these markers statistical correlating with the likelihood of cancer recurrence and overall patient survival. As such CSC markers are of high clinical relevance. The majority of markers currently used to identify CSC populations are glycoproteins, and although the diverse biological roles for many of these markers are known, the nature and function of the glycan moiety on these glycoproteins remains to be fully elucidated. This mini-review summarises our current knowledge regarding the types and extent of CSC marker glycosylation, and the various roles that these glycans play in CSC biology, including in mediating cell adhesion, metastasis, evading apoptosis, tear shear resistance, tumour growth, maintaining pluripotency, self-renewal, trafficking, maintaining stability, maintaining enzymatic activity and aiding epithelial mesenchymal transitioning. Given that CSCs markers have multiple diverse biological functions, and are potentially of significant diagnostic and therapeutic benefit the search for new markers that are uniquely expressed on CSCs is vital to selectively target/identify this subset of cancer cells. As such we have also outlined how high-throughput lectin microarrays can be used to successfully profile the glycosylation status of CSC and to identify glyco-markers unique to CSCs.

Targeting Colorectal Cancer Proliferation, Stemness and Metastatic Potential Using Brassicaceae Extracts Enriched in Isothiocyanates: A 3D Cell Model-Based Study

Colorectal cancer (CRC) recurrence is often attributable to circulating tumor cells and/or cancer stem cells (CSCs) that resist to conventional therapies and foster tumor progression. Isothiocyanates (ITCs) derived from Brassicaceae vegetables have demonstrated anticancer effects in CRC, however little is known about their effect in CSCs and tumor initiation properties. Here we examined the effect of ITCs-enriched Brassicaceae extracts derived from watercress and broccoli in cell proliferation, CSC phenotype and metastasis using a previously developed three-dimensional HT29 cell model with CSC-like traits. Both extracts were phytochemically characterized and their antiproliferative effect in HT29 monolayers was explored. Next, we performed cell proliferation assays and flow cytometry analysis in HT29 spheroids treated with watercress and broccoli extracts and respective main ITCs, phenethyl isothiocyanate (PEITC) and sulforaphane (SFN). Soft agar assays and relative quantitative expression analysis of stemness markers and Wnt/β-catenin signaling players were performed to evaluate the effect of these phytochemicals in stemness and metastasis. Our results showed that both Brassicaceae extracts and ITCs exert antiproliferative effects in HT29 spheroids, arresting cell cycle at G₂/M, possibly due to ITC-induced DNA damage. Colony formation and expression of LGR5 and CD133 cancer stemness markers were significantly reduced. Only watercress extract and PEITC decreased ALDH1 activity in a dose-dependent manner, as well as β-catenin expression. Our research provides new insights on CRC therapy using ITC-enriched Brassicaceae extracts, specially watercress extract, to target CSCs and circulating tumor cells by impairing cell proliferation, ALDH1-mediated chemo-resistance, anoikis evasion, self-renewal and metastatic potential.

Novel Palladium(II) Complexes that Influence Prominin-1/CD133 Expression and Stem Cell Factor Release in Tumor Cells

New Pd(II) complexes of 1,7-bis(2-methoxyphenyl)hepta-1,6-diene-3,5-dione were synthesized and structurally characterized. The complexes were tested in vitro on human colon and hepatic carcinoma cell lines, normal hepatic cells and hematopoietic progenitor cells. Biological tests proved that Pd(II) complexes 1 and 2 (containing a curcumin derivative) exhibit a strong in vitro antitumor effect against the cells derived from human colorectal carcinoma and the hepatic metastasis of a colorectal carcinoma. Complex 1 has an outstanding inhibitory effect against BRAF-mutant colon carcinoma and hepatocarcinoma cell growth; 1 and 2 are both more active than the free ligand and have the capacity to trigger early apoptotic processes. By flow cytometric measurements, an important decrease of prominin-1 (CD133) molecule expression on tumor cells membrane was identified in cell populations subjected to 1 and 2. Quantitative immune enzymatic assay proved restrictions in stem cell factor (SCF) release by treated tumor cells. Although less cytotoxic, the free ligand inhibits the surface marker CD133 expression in hepatocarcinoma cells, and in HT-29 colon carcinoma. The new synthesized Pd(II) complexes 1 and 2 exhibit an important potential through their selective cytotoxic activity and by targeting the stem-like tumor cell populations, which leads to the tumor growth arrest and prevention of metastasis.

Salinomycin inhibits metastatic colorectal cancer growth and interferes with Wnt/β-catenin signaling in CD133+ human colorectal cancer cells

Background

The polyether antibiotic Salinomycin (Sal) is regarded as an inhibitor of cancer stem cells. Its effectiveness on human colorectal cancer (CRC) cells in vitro has been demonstrated before. The aim of this study was to establish a murine model to investigate the effectiveness of Sal in vivo. Furthermore, we investigated the impact of Sal on Wnt/β-catenin signaling in human CD133⁺ CRC cells.

Methods

The two murine CRC cell lines MC38 and CT26 were used to analyze the impact of Sal on tumor cell proliferation, viability, migration, cell cycle progression and cell death in vitro. For in vivo studies, CT26 cells were injected into syngeneic BALB/c mice to initiate (i) subcutaneous, (ii) orthotopic, or (iii) metastatic CRC growth. Sal was administered daily, 5-Fluoruracil served as a control. For mechanistic studies, the CD133⁺and CD133^- subpopulations of human CRC cells were separated by flow cytometry and separately exposed to increasing concentrations of Sal. The impact on Wnt/β-catenin signaling was determined by Western blotting and quantitative PCR.

Results

Sal markedly impaired tumor cell viability, proliferation and migration, and induced necrotic cell death in vitro. CRC growth in vivo was likewise inhibited upon Sal treatment. Interference with Wnt signaling and reduced expression of the Wnt target genes Fibronectin and Lgr5 indicates a novel molecular mechanism, mediating anti-tumoral effects of Sal in CRC.

Conclusion

Sal effectively impairs CRC growth in vivo. Furthermore, Sal acts as an inhibitor of Wnt/β-catenin signaling. Thus, Salinomycin represents a promising candidate for clinical CRC treatment.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-016-2879-8) contains supplementary material, which is available to authorized users.

CD44 expression trends of mesenchymal stem-derived cell, cancer cell and fibroblast spheroids on chitosan-coated surfaces

CD44, a cell-surface glycoprotein, plays an important role in cell proliferation, adhesion, migration, and other biological functions, which are related with the physiological and pathologic activities of cells. Especially, CD44 is extensively expressed within adult bone marrow and has been considered as an important marker for some cancer stem cells (CSCs) in various types of tumors. Therefore, it is essential to understand the variations in CD44 expression of stem cells and cancer cells for further clinical applications. In this paper, CD44 expression was assessed on a human colon cancer cell line (SW620), a human mesenchymal stem-like cell line (3A6), and a human foreskin fibroblast line (Hs68). We used chitosan to establish a suspension culture model to develop multicellular spheroids to mimic a three-dimension (3D) in vivo environment. Obviously, CD44 expression on 3A6 and SW620 cells was dynamic and diverse when they were in the aggregated state suspended on chitosan, while Hs68 cells were relatively stable. Furthermore, we discuss how to regulate CD44 expression of 3A6 and SW620 cells by the interactions between cell and cell, cell and chitosan, as well as cell and microenvironment. Finally, the possible mechanism of chitosan to control CD44 expression of cells is proposed, which may lead to the careful use of chitosan for potential clinical applications.

Association between cancer stem cell-like properties and epithelial-to-mesenchymal transition in primary and secondary cancer cells

One of the theories on cancer stem cells (CSCs) states that these cells initiate most tumors and give rise to more-or-less differentiated tumor cells. Genetic signatures of CSCs are thought to predict tumor recurrence and metastases, thus, supporting the notion that CSCs may be metastatic precursors and induce epithelial-to-mesenchymal transition (EMT). In this study, we tried to examine the association between CSCs and EMT (using specific markers) in the mucoepidermoid carcinoma cell line YD15 and its derivative cell line YD15M (lymph node metastasis). Relative protein expression levels were analyzed by western blotting, flow cytometry, and immunofluorescence assays. In addition, cell cycle assay and aldehyde dehydrogenase (ALDH) activity assay were carried out. Under growth conditions, YD15M cells formed irregular spherical colonies consistent with a stem cell phenotype. YD15M cells demonstrated the low expression of E-cadherin and β-catenin but high expression of vimentin than that in YD15 cells. In the metastatic cells (YD15M), the coexpression of vimentin and CD133 was detected. Weak proliferation based on cell cycle analysis and decreased PCNA expression was also observed. In addition, expression levels of ALDHA1, OCT4, and NANOG (CSC-like properties) were significantly increased in YD15M cells. Taken together, these findings should help to elucidate the interplay between EMT and CSC-like properties during metastasis and may provide useful information for the development of a novel classification system and therapeutic strategies against head and neck cancer.

Pancreatic Tumor Progression Associated With CD133 Overexpression: Involvement of Increased TERT Expression and Epidermal Growth Factor Receptor-Dependent Akt Activation

OBJECTIVES

The aim of this study was to investigate the role of CD133 in pancreatic ductal adenocarcinoma malignancy and its involvement in epidermal growth factor receptor (EGFR) signaling.

METHODS

The effects of CD133 overexpression on cell proliferation, migration, invasiveness, and angiogenesis were investigated in the human pancreatic ductal adenocarcinoma cell line AsPC-1 in vitro and severe combined immunodeficiency xenografts in vivo.

RESULTS

AsPC-1 cells overexpressing CD133 (AsPC-1 CD133 cells) had elevated cell proliferation, tumorigenesis, cell cycle progression, adhesion, migration, and angiogenesis. AsPC-1 CD133 cells displayed increased survival during treatment with chemotherapeutic agents. CD133 overexpression resulted in decreased EGF expression, increased telomerase reverse transcriptase expression, and increased Akt phosphorylation. Immunoprecipitation assays and immunofluorescent labeling studies revealed that CD133 physically interacts with EGFR. The EGFR inhibitor gefitinib was shown to have potent anti-CD133 activity, decreasing the CD133-induced migration of AsPC-1 CD133 cells. Knockdown of CD133 was also observed to inhibit AsPC-1 CD133 cell proliferation, migration, and invasion.

CONCLUSION

Our results indicate that CD133-induced cancer stem cell activity may arise from enhanced telomerase reverse transcriptase expression and CD133 ligand-independent EGFR activation to exhibit the cancer stem cell phenotype, promoting cancer stem cell proliferation independent of cytokines, with high metastatic potential and the development of chemoresistance.

Genome-wide copy number changes and CD133 expression characterized distinct subset of colon polyps: differentiation between incidental polyps and cancer-associated polyps

PURPOSE

Colorectal polyps are generally believed to be the precursors of colorectal cancers (CRC); however, the proportion and speed of progression differed widely in different subsets of polyps. Using microarray-based comparative genomic hybridization (aCGH) platform and CD133 immunostaining, we characterized colon polyps according to their association with CRC that developed in the same individual.

PATIENTS AND METHODS

aCGH was performed to unveil genomic changes in 18 cancer-synchronous polyps (CSP), and 9 cancer-preceding polyps (CPP), together with their corresponding cancers and 16 cases of incidental polyps (IP), were examined for comparison. aCGH profiles were analyzed to determine the clonal relationship (CR) between the paired adenoma and carcinoma. CD133 expressions in each subset of polyps were quantified by immunohistochemistry (IHC) staining.

RESULTS

Progressive genomic changes were observed from IP, CSP/CPP to CRC; they encompass an entire chromosomal region in IP and sub-chromosomal region in CSP/CPP and CRC. CR analyses demonstrated that 50 % of CSP and 67 % of CPP were clonally related to the concurrent or later developed carcinomas, respectively. The CD133 expression levels were significantly higher in CSP/CPP than those in IP (P < 0.0001) and even higher in CSP/CPP that were clonally related to their corresponding carcinomas than CSP/CPP that were unrelated (P < 0.05).

CONCLUSIONS

There were more genomic changes in CSP/CPP than IP; more than half of the CSP/CPP were clonally related to the corresponding carcinomas. Genomic changes at sub-chromosomal regions and/or high CD133 expression were associated with CSP/CPP and highlighted their carcinogenic potential.

Intragenic G-quadruplex structure formed in the human CD133 and its biological and translational relevance

Cancer stem cells (CSCs) have been identified in several solid malignancies and are now emerging as a plausible target for drug discovery. Beside the questionable existence of CSCs specific markers, the expression of CD133 was reported to be responsible for conferring CSC aggressiveness. Here, we identified two G-rich sequences localized within the introns 3 and 7 of the CD133 gene able to form G-quadruplex (G4) structures, bound and stabilized by small molecules. We further showed that treatment of patient-derived colon CSCs with G4-interacting agents triggers alternative splicing that dramatically impairs the expression of CD133. Interestingly, this is strongly associated with a loss of CSC properties, including self-renewing, motility, tumor initiation and metastases dissemination. Notably, the effects of G4 stabilization on some of these CSC properties are uncoupled from DNA damage response and are fully recapitulated by the selective interference of the CD133 expression.In conclusion, we provided the first proof of the existence of G4 structures within the CD133 gene that can be pharmacologically targeted to impair CSC aggressiveness. This discloses a class of potential antitumoral agents capable of targeting the CSC subpopulation within the tumoral bulk.

Fibroblast-Derived Exosomes Contribute to Chemoresistance through Priming Cancer Stem Cells in Colorectal Cancer

Chemotherapy resistance observed in patients with colorectal cancer (CRC) may be related to the presence of cancer stem cells (CSCs), but the underlying mechanism(s) remain unclear. Carcinoma-associated fibroblasts (CAFs) are intimately involved in tumor recurrence, and targeting them increases chemo-sensitivity. We investigated whether fibroblasts might increase CSCs thus mediating chemotherapy resistance. CSCs were isolated from either patient-derived xenografts or CRC cell lines based on expression of CD133. First, CSCs were found to be inherently resistant to cell death induced by chemotherapy. In addition, fibroblast-derived conditioned medium (CM) promoted percentage, clonogenicity and tumor growth of CSCs (i.e., CD133+ and TOP-GFP+) upon treatment with 5-fluorouracil (5-Fu) or oxaliplatin (OXA). Further investigations exhibited that exosomes, isolated from CM, similarly took the above effects. Inhibition of exosome secretion decreased the percentage, clonogenicity and tumor growth of CSCs. Altogether, our findings suggest that, besides targeting CSCs, new therapeutic strategies blocking CAFs secretion even before chemotherapy shall be developed to gain better clinical benefits in advanced CRCs.

Metastatic colon cancer cell populations contain more cancer stem-like cells with a higher susceptibility to natural killer cell-mediated lysis compared with primary colon cancer cells

In the present study, the soft agar clonogenicity and the susceptibility of clonogenic cancer cells to natural killer (NK) cells were compared between primary colon cancer cells (KM12C) and metastatic colon cancer cells (KM12L4a and KM12SM) to determine whether the metastatic cancer cells consisted of more cancer stem-like cells and were resistant to NK cell-mediated lysis. The majority of colon cancer cells were positive for putative cancer stem cell markers, including CD44, CD133 and EpCAM, with the exception of KM12C cells, of which only ~55% were positive for CD133. In addition, the expression levels of sex determining region Y-box 2, Nanog and octamer-binding transcription factor 4, which are essential for maintaining self-renewal, were higher in KM12L4a and KM12SM compared with that in KM12C cells. Consistently, an increased clonogenicity of KM12L4a and KM12SM compared with KM12C cells in soft agar was observed. The expression levels of NKG2D ligands, including major histocompatibility complex class I polypeptide-related sequence A/B and UL16 binding protein 2, and of death receptor 5 were significantly higher in KM12L4a and KM12SM than in KM12C cells. Furthermore, the results indicated an increased susceptibility of KM12L4a and KM12SM to NK cell-mediated cytotoxicity in comparison with KM12C cells. These results indicated that metastatic colon cancer cell populations may consist of more cancer stem-like cells, and have greater susceptibility to NK cell-mediated lysis compared with that of primary colon cancers.

CD26-positive/CD326-negative circulating cancer cells as prognostic markers for colorectal cancer recurrence

The present study evaluated the presence and clinical relevance of a cluster of differentiation (CD)26⁺/CD326^- subset of circulating tumor cells (CTCs) in pre- and post-operative blood samples of colorectal cancer patients, who had undergone curative or palliative intervention, in order to find a novel prognostic factor for patient management and follow-up. In total, 80 colorectal cancer patients, along with 25 healthy volunteers were included. The easily transferable methodology of flow cytometry, along with multiparametric antibody staining were used to selectively evaluate CD26⁺/CD326^- CTCs in the peripheral blood samples of colorectal cancer patients. The multiparametric selection allowed any enrichment methods to be avoided thus rendering the whole procedure suitable for clinical routine. The presence of CD26⁺/CD326^- cells was higher in advanced Dukes' stages and was significantly associated with poor survival and high recurrence rates. Relapsing and non-surviving patients showed the highest number of CD26⁺/CD326^- CTCs. High pre-operative levels of CD26⁺/CD326^- CTCs correctly predicted tumor relapse in 44.4% of the cases, while 69% of post-operative CD26⁺/CD326^- CTC-positive patients experienced cancer recurrence, with a test accuracy of 88.8%. By contrast, post-operative CD26⁺/CD326^- CTC-negative patients showed an increase in the three-year progression-free survival rate of 86%, along with a reduced risk of tumor relapse of >90%. In conclusion, CD26⁺/CD326^- CTCs are an independent prognostic factor for tumor recurrence rate in multivariate analysis, suggesting that their evaluation could be an additional factor for colorectal cancer recurrence risk evaluation in patient management.

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

INTRODUCTION

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

MATERIALS AND METHODS

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

RESULTS

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

CONCLUSIONS

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

MicroRNA binding site polymorphisms as biomarkers in cancer management and research

MicroRNAs (miRNAs) are important regulators of eukaryotic gene expression. They have been implicated in a broad range of biological processes, and miRNA-related genetic alterations probably underlie several human diseases. Single nucleotide polymorphisms of transcripts may modulate the posttranscriptional regulation of gene expression by miRNAs and explain interindividual variability in cancer risk and in chemotherapy response. On the basis of recent association studies published in the literature, the present review mainly summarizes the potential role of miRNAs as molecular biomarkers for disease susceptibility, diagnosis, prognosis, and drug-response prediction in tumors. Many clues suggest a role for polymorphisms within the 3' untranslated regions of KRAS rs61764370, SET8 rs16917496, and MDM4 rs4245739 as SNPs in miRNA binding sites highly promising in the biology of human cancer. However, more studies are needed to better characterize the composite spectrum of genetic determinants for future use of markers in risk prediction and clinical management of diseases, heading toward personalized medicine.

CD133 is essential for glioblastoma stem cell maintenance

The role of the cell surface CD133 as a cancer stem cell marker in glioblastoma (GBM) has been widely investigated, since it identifies cells that are able to initiate neurosphere growth and form heterogeneous tumors when transplanted in immune-compromised mice. However, evidences of CD133-negative cells exhibiting similar properties have also been reported. Moreover, the functional role of CD133 in cancer stem/progenitor cells remains poorly understood. We studied the biological effects of CD133 downregulation in GBM patient-derived neurospheres. Our results indicate that there is not a hierarchical relation between CD133-positive and CD133-negative cells composing the neurospheres. Indeed, CD133 appears in an interconvertible state, changing its subcellular localization between the cytoplasm and the plasmamembrane of neurosphere cells. Silencing of CD133 in human GBM neurospheres using lentivirus-mediated short hairpin RNA impairs the self-renewal and tumorigenic capacity of neurosphere cells. These results imply that CD133 could be used as a therapeutic target in GBMs.

Study on the Biological Characteristics of CD133 (+) Cells Interfered by RNA Interference in Gastric Cancer

Background. To detect the changes of biological characteristics in gastric cancer cells interfered by CD133-specific small interfering RNA (siRNA). Methods. First to select the siRNA which has the strongest interference effect among 3 siRNAs (i.e., siRNA1, siRNA2, and siRNA3) in KATO-III cells by RT-PCR and Western blotting assays. Then, CD133⁺ cells were sorted out from KATO-III cells using an immunomagnetic bead sorting method and transfected with the selected siRNA. Furthermore, the proliferating characteristics, the antichemotherapeutic assessment, Transwell invasion assay, monoclonal sphere formation assay, and subcutaneous transplanted tumor formation assay in nude mice were investigated. Results. siRNA3 showed the strongest interference effect in KATO-III cells. As compared to the uninterfered control group, the CD133⁺ cells treated by siRNA3 showed significant decreases in the abilities of proliferation, invasion, clone sphere formation, and resistance to antitumour drugs as well as the weight and size of the transplanted tumor, which was nearly similar to that of CD133⁻ cells. Additionally, the protein expression level of the EMT factor E-cadherin increased while those of EMT-related Snail and N-cadherin decreased in CD133⁺ cells interfered by siRNA3. Conclusion. Inhibition of CD133 gene expression reduces the abilities of gastric cancer cells in proliferation, invasion, clonal sphere formation, and chemoresistance as well as tumor formation in nude mice.

The culture of cancer cell lines as tumorspheres does not systematically result in cancer stem cell enrichment

Cancer stem cells (CSC) have raised great excitement during the last decade and are promising targets for an efficient treatment of tumors without relapses and metastases. Among the various methods that enable to enrich cancer cell lines in CSC, tumorspheres culture has been predominantly used. In this report, we attempted to generate tumorspheres from several murine and human cancer cell lines: B16-F10, HT-29, MCF-7 and MDA-MB-231 cells. Tumorspheres were obtained with variable efficiencies from all cell lines except from MDA-MB-231 cells. Then, we studied several CSC characteristics in both tumorspheres and adherent cultures of the B16-F10, HT-29 and MCF-7 cells. Unexpectedly, tumorspheres-forming cells were less clonogenic and, in the case of B16-F10, less proliferative than attached cells. In addition, we did not observe any enrichment in the population expressing CSC surface markers in tumorspheres from B16-F10 (CD133, CD44 and CD24 markers) or MCF-7 (CD44 and CD24 markers) cells. On the contrary, tumorspheres culture of HT-29 cells appeared to enrich in cells expressing colon CSC markers, i.e. CD133 and CD44 proteins. For the B16-F10 cell line, when 1 000 cells were injected in syngenic C57BL/6 mice, tumorspheres-forming cells displayed a significantly lower tumorigenic potential than adherent cells. Finally, tumorspheres culture of B16-F10 cells induced a down-regulation of vimentin which could explain, at least partially, the lower tumorigenicity of tumorspheres-forming cells. All these results, along with the literature, indicate that tumorspheres culture of cancer cell lines can induce an enrichment in CSC but in a cell line-dependent manner. In conclusion, extensive characterization of CSC properties in tumorspheres derived from any cancer cell line or cancer tissue must be performed in order to ensure that the generated tumorspheres are actually enriched in CSC.

Chemotherapy activates cancer-associated fibroblasts to maintain colorectal cancer-initiating cells by IL-17A

Chemotherapy stimulates cancer-associated fibroblasts to secrete interleukin-17A to provide maintenance cues to support the growth of colorectal cancer-initiating cells.

Many solid cancers display cellular hierarchies with self-renewing, tumorigenic stemlike cells, or cancer-initiating cells (CICs) at the apex. Whereas CICs often exhibit relative resistance to conventional cancer therapies, they also receive critical maintenance cues from supportive stromal elements that also respond to cytotoxic therapies. To interrogate the interplay between chemotherapy and CICs, we investigated cellular heterogeneity in human colorectal cancers. Colorectal CICs were resistant to conventional chemotherapy in cell-autonomous assays, but CIC chemoresistance was also increased by cancer-associated fibroblasts (CAFs). Comparative analysis of matched colorectal cancer specimens from patients before and after cytotoxic treatment revealed a significant increase in CAFs. Chemotherapy-treated human CAFs promoted CIC self-renewal and in vivo tumor growth associated with increased secretion of specific cytokines and chemokines, including interleukin-17A (IL-17A). Exogenous IL-17A increased CIC self-renewal and invasion, and targeting IL-17A signaling impaired CIC growth. Notably, IL-17A was overexpressed by colorectal CAFs in response to chemotherapy with expression validated directly in patient-derived specimens without culture. These data suggest that chemotherapy induces remodeling of the tumor microenvironment to support the tumor cellular hierarchy through secreted factors. Incorporating simultaneous disruption of CIC mechanisms and interplay with the tumor microenvironment could optimize therapeutic targeting of cancer.

The role of colorectal cancer stem cells in metastatic disease and therapeutic response

Colorectal cancer is the third-leading cause of cancer related mortality in the United States. The intricate molecular mechanisms involved in the regenerative process of the normal intestine and the identity of putative somatic intestinal stem cells have become clear. In parallel with this, experiment evidence has emerged supporting the century old hypothesis that solid tumor initiation, progression, chemoresistance and recurrence is the result of a small population of cancer cells with self-renewal and pluripotency capabilities. These "cancer stem cells" (CSCs) present a unique opportunity to better understand the biology of solid tumors in general, as well as targets for future therapeutics. In this review, we will summarize the current understanding of intestinal stem cell biology and translate it to colorectal CSCs to provide a basis for understanding chemoresistance, cancer recurrence and metastasis. A more complete understanding of the biology of colorectal CSCs will translate into the development of better chemotherapeutic and biological agents for the treatment of colorectal cancer.

In vitro and in vivo properties of CD133 expressing cells from human lung cancer cell lines

Background

Tumor development is recently hypothesized to depend on a rare cell population with stem cell properties, such cells are called cancer stem cells (CSCs) or tumor-initiating cells (TICs). From various cancer tissues or cancer cell lines, CD133 expressing cells were found to define a unique CSC/TIC phenotype. To study whether that also could be the case in lung cancer, we examined different lung cancer cell lines for CD133 expression.

Results

Among the 4 cell lines studied, only the cell line LC-42 expressed CD133. Therefore, LC-42 was further characterized and studied with special emphasis on identifying the presence of CD133⁺ CSCs/TICs. FACS sorted CD133^high and CD133^dim subpopulations from LC-42 showed no differences in soft agar colony-forming capacity and spheres-forming capacity in serum-free cultures. LC-42 cells contained Side Population (SP), and only SP cells were able to form spheres. Furthermore, Nanog expression was significantly higher in SP than in non-SP. However, no difference was observed of CD133 expression in SP and non-SP. When CD133^high and CD133^dim cells were serially xeno-transplanted in NOD/SCID mice, both formed tumours similar to their parental LC-42 cells. There were no expression differences for NANOG, OCT4 and SOX2 examined immunohistochemically in the xenografts from both cell fractions.

Conclusion

Our data do not show a difference in tumorigenic potential of CD133^high and CD133^dim cells with respect to any of the parameters analyzed in vitro and in vivo, suggesting that CD133 expression is not restricted to cancer-initiating cells in the human lung cancer cell line LC-42.

Response to stress in early tumor colonization modulates switching of CD133-positive and CD133-negative subpopulations in a human metastatic colon cancer cell line, SW620

According to the cancer stem cell (CSC) model, higher CD133 expression in tumor tissue is associated with metastasis and poor prognosis in colon cancer. As such, the CD133-positive (CD133⁺) subpopulation of cancer cells is believed to play a central role in tumor development and metastatic progression. Although CD133⁺ cells are believed to display more CSC-like behavior and be solely responsible for tumor colonization, recent research indicates that CD133⁻ cells from metastatic colon tumors not only also possess colonization capacity but also promote the growth of larger tumors in a mouse model than CD133⁺ cells, suggesting that an alternative mechanism of metastasis exists. This study investigated this possibility by examining the cell viability, tumorigenicity, and proliferation and growth capacity of the CD133⁺ and CD133⁻ subpopulations of the SW620 cell line, a human metastatic colon cancer cell line, in both an in vitro cell model and an in vivo mouse model. While both SW620 ^CD133− and SW620^CD133+ cells were found to engage in bidirectional cell-type switching in reaction to exposure to environmental stressors, including hypoxia, a cell adhesion-free environment, and extracellular matrix stimulation, both in vitro and in vivo, CD133⁻ cells were found to have a growth advantage during early colonization due to their greater resistance to proliferation inhibition. Based on these findings, a hypothetical model in which colon cancer cells engage in cell-type switching in reaction to exposure to environmental stressors is proposed. Such switching may provide a survival advantage during early colonization, as well as that explain previous conflicting observations.

Krüppel-like factor 4 acts as an oncogene in colon cancer stem cell-enriched spheroid cells

Cancer stem cells (CSCs), a rare population in any type of cancers, including colon cancer, are tumorigenic. It has been thought that CSCs are responsible for cancer recurrence, metastasis, and drug resistance. Isolating CSCs in colon cancers is challenging, and thus the molecular mechanism regulating the self-renewing and differentiation of CSCs remains unknown. We cultured DLD-1 cells, one of types of cells derived from colon cancers, in serum-free medium to obtain spheroid cells. These cells possessed the characteristics of CSCs, with the expression of CD133, CD166, Lgr5, and ALDH1, higher capacities of chemo-resistance, migration, invasion, and tumorigenicity in vitro and in vivo than the adherent DLD-1 cells. Krüppel-like factor 4 (KLF4) is essential factor for maintaining self-renewal of adult and embryonic stem cells. It has been used to induce pluripotent stem cells (iPS) from somatic cells. Since KLF4 is expressed in colon cancer cells, we investigated its role in spheroid cells isolated from DLD-1 cells and found that KLF4 was overexpressed only in spheroid cells and reducing the expression of KLF4 by short-hairpin RNA significantly decreased the capacities of these cells to resist the chemicals, migrate, invade, and generate tumors in vitro and in vivo. The spheroid cells with reduced KLF4 expression also had decreased expression of CSCs markers and mesenchymal markers. Taken together, culturing DLD-1 cells in serum-free medium enriches CSCs and the expression of KLF4 is essential for the characteristics of CSCs in DLD-1; thus KLF4 can be a potential therapeutic target for treating colon cancer.

CD133 affects the invasive ability of HCT116 cells by regulating TIMP-2

CD133 is widely expressed in colorectal cancer (CRC) tissues and cell lines. This protein has been used as a marker of CRC cancer stem cells, although the function and mechanism of CD133 in CRC invasion and metastasis remain unclear. In our study, we examined the role of CD133 in CRC invasion in vitro and investigated the mechanism involved in CD133-related invasion. CD133(high) and CD133(low) HCT116 cells were isolated, and the proliferation and invasive ability of these two subpopulations were tested. CD133(high) HCT116 cells exhibited greater proliferation and invasion compared with CD133(low) HCT116 cells. CD133 knockdown (using CD133 small-interfering [si]RNA) inhibited the invasive activity of CD133si-HCT116 cells. For the first time, we found that the expression of tissue inhibitor of matrix metalloproteinases-2 (TIMP-2) was down-regulated in CD133si-HCT116 cells. In addition, for the TIMP-2si-HCT116 cells (transfected with TIMP-2 siRNA), in vitro invasion was significantly decreased, whereas the expression of CD133 remained unchanged. Finally, the metalloproteinase 2 and MEK/ERK signaling pathways were examined, and no significant change was observed after the knockdown of CD133 or TIMP-2 in HCT116 cells. In conclusion, we demonstrated that CD133 plays an important role in HCT116 cell invasion, and for the first time, we found that CD133 knockdown significantly down-regulated TIMP-2 expression, which suggests that CD133 affects the invasive ability of HCT116 cells by regulating TIMP-2.