Expression of putative stem cell genes Musashi-1 and beta1-integrin in human colorectal adenomas and adenocarcinomas

Functional Role of RBP in Osteosarcoma: Regulatory Mechanism and Clinical Therapy

Malignant bone neoplasms can be represented by osteosarcoma (OS), which accounts for 36% of all sarcomas. To reduce tumor malignancy, extensive efforts have been devoted to find an ideal target from numerous candidates, among which RNA-binding proteins (RBPs) have shown their unparalleled competitiveness. With the special structure of RNA-binding domains, RBPs have the potential to establish relationships with RNAs or small molecules and are considered regulators of different sections of RNA processes, including splicing, transport, translation, and degradation of RNAs. RBPs have considerable significant roles in various cancers, and experiments revealed that there was a strong association of RBPs with tumorigenesis and tumor cell progression. Regarding OS, RBPs are a new orientation, but achievements in hand are noteworthy. Higher or lower expression of RBPs was first found in tumor cells compared to normal tissue. By binding to different molecules, RBPs are capable of influencing tumor cell phenotypes through different signaling pathways or other axes, and researches on medical treatment have been largely inspired. Exploring the prognostic and therapeutic values of RBPs in OS is a hotspot where diverse avenues on regulating RBPs have achieved dramatical effects. In this review, we briefly summarize the contribution of RBPs and their binding molecules to OS oncogenicity and generally introduce distinctive RBPs as samples. Moreover, we focus on the attempts to differentiate RBP's opposite functions in predicting prognosis and collect possible strategies for treatment. Our review provides forwards insight into improving the understanding of OS and suggests RBPs as potential biomarkers for therapies.

Rationally designed inhibitors of the Musashi protein-RNA interaction by hotspot mimicry

RNA-binding proteins (RBPs) are key post-transcriptional regulators of gene expression, and thus underlie many important biological processes. Here, we developed a strategy that entails extracting a "hotspot pharmacophore" from the structure of a protein-RNA complex, to create a template for designing small-molecule inhibitors and for exploring the selectivity of the resulting inhibitors. We demonstrate this approach by designing inhibitors of Musashi proteins MSI1 and MSI2, key regulators of mRNA stability and translation that are upregulated in many cancers. We report this novel series of MSI1/MSI2 inhibitors is specific and active in biochemical, biophysical, and cellular assays. This study extends the paradigm of "hotspots" from protein-protein complexes to protein-RNA complexes, supports the "druggability" of RNA-binding protein surfaces, and represents one of the first rationally-designed inhibitors of non-enzymatic RNA-binding proteins. Owing to its simplicity and generality, we anticipate that this approach may also be used to develop inhibitors of many other RNA-binding proteins; we also consider the prospects of identifying potential off-target interactions by searching for other RBPs that recognize their cognate RNAs using similar interaction geometries. Beyond inhibitors, we also expect that compounds designed using this approach can serve as warheads for new PROTACs that selectively degrade RNA-binding proteins.

Cytokine-mediated crosstalk between cancer stem cells and their inflammatory niche from the colorectal precancerous adenoma stage to the cancerous stage: Mechanisms and clinical implications

The majority of colorectal cancers (CRCs) are thought to arise from precancerous adenomas. Upon exposure to diverse microenvironmental factors, precancerous stem cells (pCSCs) undergo complex genetic/molecular changes and gradually progress to form cancer stem cells (CSCs). Accumulative evidence suggests that the pCSC/CSC niche is an inflammatory dominated milieu that contains different cytokines that function as the key communicators between pCSCs/CSCs and their niche and have a decisive role in promoting CRC development, progression, and metastasis. In view of the importance and increasing data about cytokines in modulating pCSCs/CSC stemness properties and their significance in CRC, this review summarizes current new insights of cytokines, such as interleukin (IL)-4, IL-6, IL-8, IL-17A, IL-22, IL-23, IL-33 and interferon (IFN)-γ, involving in the modulation of pCSC/CSC properties and features in precancerous and cancerous lesions and discusses the possible mechanisms of adenoma progression to CRCs and their therapeutic potential.

The presentation and regulation of the IL-8 network in the epithelial cancer stem-like cell niche in patients with colorectal cancer

BACKGROUND

Accumulative evidence suggests that the biological behavior of cancer stem-like cells (CSCs) is regulated by their surrounding niche, in which cytokines function as one of the main mediators for the interaction between CSCs and their microenvironment in the colorectal cancer (CRC).

METHODS

We characterized the presentation of CSCs and the interleukin (IL)- 8 network in the adenoma/CRC epithelium using quantitative real-time PCR (q-PCR), immunohistochemistry (IHC) and double immunofluorescence. In addition, the capacity of IL-1β to stimulate epithelial IL-8 production in colon cancer Caco-2 cells was examined in vitro and the IL-8 product was measured by enzyme-linked immunosorbent assay (ELISA).

RESULTS

IHC observation showed increased expression of both CSCs and IL-8 in the adenoma and CRC epithelium, and q-PCR results revealed that increased expression of IL-1β transcript was strongly correlated with increased IL-8 transcript levels in both adenoma and CRC tissues. Double immunofluorescence images demonstrated the coexpression of the IL-8 receptors IL-8RA and IL-8RB with LGR5 labeled CSCs in CRC tissue sections. Consistently, in vitro experiments showed that coculture of Caco-2 cells with IL-1β at concentrations of 1, 5, 10 and 20 ng/ml resulted in a dose-dependent release of IL-8, which could be specifically inhibited by cotreatment with the IL-1β receptor antagonist.

CONCLUSIONS

These results demonstrate activation of the IL-8 network in the niche of CSCs from the precancerous adenoma stage to the CRC stage, which is potentially stimulated by IL-1β in CRC cells.

Is There Such a Thing as a Genuine Cancer Stem Cell Marker? Perspectives from the Gut, the Brain and the Dental Pulp

The conversion of healthy stem cells into cancer stem cells (CSCs) is believed to underlie tumor relapse after surgical removal and fuel tumor growth and invasiveness. CSCs often arise from the malignant transformation of resident multipotent stem cells, which are present in most human tissues. Some organs, such as the gut and the brain, can give rise to very aggressive types of cancers, contrary to the dental pulp, which is a tissue with a very remarkable resistance to oncogenesis. In this review, we focus on the similarities and differences between gut, brain and dental pulp stem cells and their related CSCs, placing a particular emphasis on both their shared and distinctive cell markers, including the expression of pluripotency core factors. We discuss some of their similarities and differences with regard to oncogenic signaling, telomerase activity and their intrinsic propensity to degenerate to CSCs. We also explore the characteristics of the events and mutations leading to malignant transformation in each case. Importantly, healthy dental pulp stem cells (DPSCs) share a great deal of features with many of the so far reported CSC phenotypes found in malignant neoplasms. However, there exist literally no reports about the contribution of DPSCs to malignant tumors. This raises the question about the particularities of the dental pulp and what specific barriers to malignancy might be present in the case of this tissue. These notable differences warrant further research to decipher the singular properties of DPSCs that make them resistant to transformation, and to unravel new therapeutic targets to treat deadly tumors.

Integrin Beta 1 Promotes Glioma Cell Proliferation by Negatively Regulating the Notch Pathway

In this study, genes associated with the Notch signaling pathway in gliomas were analyzed using bioinformatics and in vitro experiments. The dataset GSE22772 was downloaded from the Gene-Cloud of Biotechnology Information database. Differentially expressed genes (DEGs) between short hairpin RNA (shRNA) intervening glioma cells and control cells were screened using the unpaired t test. Functional enrichment analysis was performed, and coexpression network was analyzed to identify the most important genes associated with the Notch signaling pathway. Integrin beta 1 (ITGB1) mRNA and protein levels in clinical glioma tumor samples and tumor adjacent normal tissue samples were analyzed using quantitative real-time PCR and immunohistochemistry, respectively. The relationship between ITGB1 expression and the prognosis of patients with gliomas was analyzed using the Kaplan-Meier curve. ITGB1 interference expression cell line U87 and ITGB1 overexpressing cell line were established using sh-ITGB1 and oe-ITGB1 plasmids, respectively. MTT and colony formation assays were used to detect changes in the proliferation of glioma cells. Moreover, western blotting was used to detect the expression of Notch and Hey1. A total of 7,962 DEGs were screened between shRNA intervening glioma cells and control cells, which were mainly associated with spliceosome, proteoglycans in cancer, focal adhesion, and the Notch signaling pathway. ITGB1 showed the highest expression in the coexpression network. The mRNA and protein expression of ITGB1 in glioma tumor samples was significantly higher than that in tumor adjacent normal tissue samples (p < 0.05). Overall survival time of patients in the ITGB1 low-expression group was significantly longer than that in the ITGB1 high-expression group, indicating that ITGB1 expression negatively correlated with the prognosis. Fluorescence microscopy, qRT-PCR, and western blotting confirmed the transfection efficiency of ITGB1 overexpression and interference expression in U251 and U87 cells. The MTT and colony formation assays indicated that U87 cell proliferation was significantly inhibited after intervention with ITGB1 (p < 0.05), and overexpression of ITGB1 significantly promoted U251 cell proliferation (p < 0.05). In addition, the expression of Notch and Hey1 proteins was significantly decreased after ITGB1 intervention (p < 0.05), and their expression was significantly upregulated after ITGB1 overexpression (p < 0.05). ITGB1 expression in glioma tissues was significantly higher than that in adjacent normal tissues and was negatively correlated with the survival time of patients. Therefore, ITGB1 can significantly promote proliferation of glioma cells via feedback regulation of the Notch signaling pathway.

Identification and Validation of an Aspergillus nidulans Secondary Metabolite Derivative as an Inhibitor of the Musashi-RNA Interaction

RNA-binding protein Musashi-1 (MSI1) is a key regulator of several stem cell populations. MSI1 is involved in tumor proliferation and maintenance, and it regulates target mRNAs at the translational level. The known mRNA targets of MSI1 include Numb, APC, and P21^WAF-1, key regulators of Notch/Wnt signaling and cell cycle progression, respectively. In this study, we aim to identify small molecule inhibitors of MSI1-mRNA interactions, which could block the growth of cancer cells with high levels of MSI1. Using a fluorescence polarization (FP) assay, we screened small molecules from several chemical libraries for those that disrupt the binding of MSI1 to its consensus RNA. One cluster of hit compounds is the derivatives of secondary metabolites from Aspergillus nidulans. One of the top hits, Aza-9, from this cluster was further validated by surface plasmon resonance and nuclear magnetic resonance spectroscopy, which demonstrated that Aza-9 binds directly to MSI1, and the binding is at the RNA binding pocket. We also show that Aza-9 binds to Musashi-2 (MSI2) as well. To test whether Aza-9 has anti-cancer potential, we used liposomes to facilitate Aza-9 cellular uptake. Aza-9-liposome inhibits proliferation, induces apoptosis and autophagy, and down-regulates Notch and Wnt signaling in colon cancer cell lines. In conclusion, we identified a series of potential lead compounds for inhibiting MSI1/2 function, while establishing a framework for identifying small molecule inhibitors of RNA binding proteins using FP-based screening methodology.

MBNL1 regulates resistance of HeLa cells to cisplatin via Nrf2

Chemotherapy is an important method in the treatment of cervical cancer, but some patients will face drug resistance, which often indicates a poor prognosis. Moreover, there is no complete solution at present. Therefore, it is urgent to study the drug resistance mechanism of cervical cancer. Based on sequencing data mining, we predicted that MBNL1 might be involved in the occurrence and poor prognosis of cervical cancer, and verifed that MBNL1 could regulate the resistance of HeLa cells to cisplatin via Nrf2. In addition, we demonstrated that MBNL1 up regulated the degradation of Nrf2 protein by increasing the mRNA stability of Cul3. These results can provide theoretical basis for clinical development of new diagnosis and treatment targets for cisplatin resistance.

MicroRNA-331 inhibits development of gastric cancer through targeting musashi1

BACKGROUND

The molecular mechanisms involved in microRNAs (miRNAs) have been extensively investigated in gastric cancer (GC). However, how miR-331 regulates GC pathogenesis remains unknown.

AIM

To illuminate the effect of miR-331 on cell metastasis and tumor growth in GC.

METHODS

The qRT-PCR, CCK8, Transwell, cell adhesion, Western blot, luciferase reporter and xenograft tumor formation assays were applied to explore the regulatory mechanism of miR-331 in GC.

RESULTS

Downregulation of miR-331 associated with poor prognosis was detected in GC. Functionally, miR-331 suppressed cell proliferation, metastasis and tumor growth in GC. Further, miR-331 was verified to directly target musashi1 (MSI1). In addition, miR-331 inversely regulated MSI1 expression in GC tissues. Furthermore, upregulation of MSI1 weakened the inhibitory effect of miR-331 in GC.

CONCLUSION

miR-331 inhibited development of GC through targeting MSI1, which may be used as an indicator for the prediction and prognosis of GC.

Post-transcriptional Regulation of Colorectal Cancer: A Focus on RNA-Binding Proteins

Colorectal cancer (CRC) is a major health problem with an estimated 1. 8 million new cases worldwide. To date, most CRC studies have focused on DNA-related aberrations, leaving post-transcriptional processes under-studied. However, post-transcriptional alterations have been shown to play a significant part in the maintenance of cancer features. RNA binding proteins (RBPs) are uprising as critical regulators of every cancer hallmark, yet little is known regarding the underlying mechanisms and key downstream oncogenic targets. Currently, more than a thousand RBPs have been discovered in humans and only a few have been implicated in the carcinogenic process and even much less in CRC. Identification of cancer-related RBPs is of great interest to better understand CRC biology and potentially unveil new targets for cancer therapy and prognostic biomarkers. In this work, we reviewed all RBPs which have a role in CRC, including their control by microRNAs, xenograft studies and their clinical implications.

Natural product derivative Gossypolone inhibits Musashi family of RNA-binding proteins

BACKGROUND

The Musashi (MSI) family of RNA-binding proteins is best known for the role in post-transcriptional regulation of target mRNAs. Elevated MSI1 levels in a variety of human cancer are associated with up-regulation of Notch/Wnt signaling. MSI1 binds to and negatively regulates translation of Numb and APC (adenomatous polyposis coli), negative regulators of Notch and Wnt signaling respectively.

METHODS

Previously, we have shown that the natural product (-)-gossypol as the first known small molecule inhibitor of MSI1 that down-regulates Notch/Wnt signaling and inhibits tumor xenograft growth in vivo. Using a fluorescence polarization (FP) competition assay, we identified gossypolone (Gn) with a > 20-fold increase in Ki value compared to (-)-gossypol. We validated Gn binding to MSI1 using surface plasmon resonance, nuclear magnetic resonance, and cellular thermal shift assay, and tested the effects of Gn on colon cancer cells and colon cancer DLD-1 xenografts in nude mice.

RESULTS

In colon cancer cells, Gn reduced Notch/Wnt signaling and induced apoptosis. Compared to (-)-gossypol, the same concentration of Gn is less active in all the cell assays tested. To increase Gn bioavailability, we used PEGylated liposomes in our in vivo studies. Gn-lip via tail vein injection inhibited the growth of human colon cancer DLD-1 xenografts in nude mice, as compared to the untreated control (P < 0.01, n = 10).

CONCLUSION

Our data suggest that PEGylation improved the bioavailability of Gn as well as achieved tumor-targeted delivery and controlled release of Gn, which enhanced its overall biocompatibility and drug efficacy in vivo. This provides proof of concept for the development of Gn-lip as a molecular therapy for colon cancer with MSI1/MSI2 overexpression.

Temporal and spatial changes of cells positive for stem-like markers in different compartments and stages of human colorectal adenoma-carcinoma sequence

Considerable evidence supports the idea that stem-like cells may play an essential role during the development of colorectal cancer (CRC). To accomplish this aim, we use immunohistochemistry (IHC) and double IHC with different potential stem-like markers, anti-musashi (Msi), anti-CD133, anti- LGR5 and anti-ALDH1 to examine the presentation of stem-like cells in different compartments including adenoma/CRC epithelium, transitional crypts and tumor stroma in colorectal adenoma and CRC. The results showed that cells positive for stem-like markers were remarkably increased in number and frequently observed in the adenoma/CRC epithelium, transitional crypts and tumor stroma. Notably, the population of cells positive for stem-liker markers was expanded from the base to the middle part of the transitional crypt in both adenoma and CRC tissues, reflecting that stem-like cells are likely involved in the process of colorectal tumorigenesis. Counting results showed that the grading scores of cells positive for LGR5 and ALDH1 in the adenoma/CRC epithelium were significantly increased relative with the control epithelium, and associated with the degree of dysplasia in the adenoma and node involvement in the CRC (all P < 0.05). In addition, the density of cells positive for stem-like markers in the adenomatous/cancerous stroma was also increased and paralleled an increase in the density of proliferative stromal cells labeled by PCNA, which were primarily identified as vimentin positive fibroblasts. Our results have revealed a changed temporal and spatial presentation of stem-like markers in different stages of human colorectal adenoma-carcinoma sequence, which might be a hallmark of the adenoma-carcinoma transition.

Increased Musashi-2 and Decreased NUMB Protein Levels Observed in Human Colorectal Cancer are reverted to Normal Levels by ATRA-Induced Cell Differentiation

Background:

Musashi stem cell (SC) proteins (MSI-1 & MSI-2) are known to become over expressed during colorectal tumorigenesis in humans and mice. MSI-1 overexpression induces tumorigenesis through Notch activation via inactivation of NUMB. Previous studies also show that MSI-2 overexpression in mice induces intestinal tumorigenesis but the mechanism is independent of NUMB. However, whether the MSI-2/NUMB pathway contributes to colorectal cancer (CRC) development in humans is still undetermined.

Methods:

We evaluated expression of MSI-2 and NUMB proteins in matched normal and CRC patient samples, as well as in human CRC cell lines. We also determined whether induction of cellular differentiation by all-trans retinoic acid (ATRA) influences MSI-2 and NUMB expression.

Results:

Analysis of matched patient tissue samples and CRC cell lines showed that MSI-2 protein expression is significantly increased and NUMB expression is decreased in CRCs compared to the normal colonic tissue. Immunostaining of normal and adenomatous colonic epithelium revealed that MSI-1+ andMSI-2+ SCs reside in the SC niche and they become overpopulated during colon tumorigenesis. Moreover, promoting cellular differentiation by ATRA reduces MSI-2 protein levels, while increasing NUMB protein levels in human CRC cell lines.

Conclusions:

MSI-2/NUMB protein expression is altered during colon tumorigenesis, and indicates that MSI-2/NUMB signaling in human colonic stem cells is closely linked to normal colonic epithelial homeostasis.

Implications:

The ability to normalize MSI-2/NUMB signaling by inducing differentiation of cancer SCs suggests a novel therapeutic approach for CRC treatment.

Roles of microRNAs and RNA-Binding Proteins in the Regulation of Colorectal Cancer Stem Cells

Colorectal cancer stem cells (CSCs) are responsible for the initiation, progression and metastasis of human colorectal cancers, and have been characterized by the expression of cell surface markers, such as CD44, CD133, CD166 and LGR5. MicroRNAs (miRNAs) are differentially expressed between CSCs and non-tumorigenic cancer cells, and play important roles in the maintenance and regulation of stem cell properties of CSCs. RNA binding proteins (RBPs) are emerging epigenetic regulators of various RNA processing events, such as splicing, localization, stabilization and translation, and can regulate various types of stem cells. In this review, we summarize current evidences on the roles of miRNA and RBPs in the regulation of colorectal CSCs. Understanding the epigenetic regulation of human colorectal CSCs will help to develop biomarkers for colorectal cancers and to identify targets for CSC-targeting therapies.

Knockdown of MSI1 inhibited the cell proliferation of human osteosarcoma cells by targeting p21 and p27

Osteosarcoma is the most common type of primary bone cancer in children and adolescents, but its mechanism remains unclear. Musashi RNA-binding protein 1 (MSI1) is highly expressed in certain cancer types and functions as a putative progenitor/stem cell marker. In the present study, it was demonstrated that MSI1 expression in osteosarcoma tissue was higher compared with in the paraneoplastic tissue samples. Knockdown of MSI1 using shRNA in MG-63 and HOS cells inhibited cell proliferation in vitro and tumor formation in vivo, suggesting that MSI1 serves an essential role in osteosarcomagenesis. Further investigations demonstrated that the knockdown of MSI1 leads to the cell cycle arrest at G₀/G₁ phase, and the upregulation of p21 and p27 protein expression in osteosarcoma cells. Additionally, luciferase assays demonstrated that MSI1 can bind to the 3′ untranslated regions of p21 and p27 mRNA. In conclusion, the results of the present study suggest that the knockdown of MSI11 can suppress cell proliferation of osteosarcoma by targeting p21 and p27 and subsequently inhibiting cell cycle progression.

Overexpression of Musashi-1 protein is associated with progression and poor prognosis of gastric cancer

Musashi-1, an evolutionally conserved RNA-binding protein, has been implicated in the promotion of pathological stem cell proliferation, including tumorigenesis. The objective of the present study was to evaluate the expression of Musashi-1 protein and its implications in the progression and prognosis of gastric cancer. The expression level of Musashi-1 protein in gastric cancer was determined by western blotting and immunohistochemistry, and compared with the clinicopathological parameters. The present study revealed that the expression level of Musashi-1 protein in gastric cancer was significantly upregulated and correlated with the tumor size, tumor-node-metastasis (TNM) stage, Lauren classification, depth of invasion, vessel invasion, lymph node metastasis and distant metastasis. The mean survival time for patients with low expression levels of Musashi-1 was significantly longer compared with patients with high expression levels of Musashi-1. For each TNM stage, the mean survival time for patients with a low Musashi-1 expression levels was also significantly longer compared with patients with a high Musashi-1 expression level. Notably, TNM stage II patients with a low Musashi-1 expression level demonstrated a longer mean survival time compared with TNM stage I patients with high Musashi-1 expression level (56.8 vs. 42.3 months; P=0.001), and TNM stage III patients with low Musashi-1 expression level exhibited a longer mean survival time compared with TNM stage II patients with a high Musashi-1 expression level (44.0 vs. 33.8 months; P=0.034). Multivariate Cox's regression test demonstrated that Musashi-1 protein expression level was an independent prognostic indicator for the survival rate of the patients with gastric cancer. The results of the present study highlighted an important role for Musashi-1 protein in the progression of gastric cancer. The detection of the Musashi-1 protein expression level alone or in combination with TNM staging may aid the prediction of the prognosis of patients with gastric cancer.

Msi1 promotes tumor progression by epithelial-to-mesenchymal transition in cervical cancer

Musashi1 (Msi1) is an RNA-binding protein that has been reported to be a pivotal regulator in tumorigenesis and progression in several cancers. However, its function and mechanism in cervical cancer is still unknown. In this study, Msi1 expression was found elevated in cervical cancers by immunohistochemistry and correlated with poor outcomes. Then, endogenous Msi1 was silenced in cervical cancer cell lines by short hairpin RNA, and its function and mechanism were determined. The results showed that the silencing of Msi1 in SiHa and HeLa cells inhibited the cells' migratory and invasive abilities in vitro and tumor progression in vivo. Epithelial-to-mesenchymal transition (EMT) markers were down-regulated, and Wnt activity was inhibited by the silencing of Msi1. In clinical tissues, positive correlations between Msi1 and EMT markers were found. In conclusion, Msi1, a diagnostic marker and potential therapeutic target, promoted the EMT progression through activation of the Wnt signaling pathway in cervical cancers, thereby contributing to poor prognosis.

Expression profiles of cancer stem cell markers: CD133, CD44, Musashi-1 and EpCAM in the cardiac mucosa-Barrett's esophagus-early esophageal adenocarcinoma-advanced esophageal adenocarcinoma sequence

INTRODUCTION

Barrett's esophagus (BE), which develops as a result of gastroesophageal reflux disease, is a preneoplastic condition for esophageal adenocarcinoma (EAC). A new hypothesis suggests that cancer is a disease of stem cells, however, their expression and pathways in BE - EAC sequence are not fully elucidated yet.

AIMS

We used a panel of putative cancer stem cells markers to identify stem cells in consecutive steps of BE-related cancer progression.

METHODS

Immunohistochemistry was performed on formalin-fixed, paraffin-embedded blocks from 58 patients with normal cardiac mucosa (n=5), BE (n=14), early EAC (pT1) from mucosal resection (n=17) and advanced EAC (pT1-T4) from postoperative specimens (n=22). Expression of the CD133, CD44, Musashi-1 and EpCAM was analyzed using respective monoclonal antibodies.

RESULTS

All markers showed a heterogeneous expression pattern, mainly at the base of the crypts of Barrett's epithelium and EAC, with positive stromal cells in metaplastic and dysplastic lesions. Immuno-expression of EpCAM, CD44 and CD133 in cardiac mucosa was significantly lower (mean immunoreactivity score (IRS)=1.2; 0.0; 0.4; respectively) compared to their expression in Barrett's metaplasia (mean IRS=4.3; 0.14; 0.7; respectively), in early adenocarcinoma (mean IRS=4.4; 0.29; 1.3; respectively) and in advanced adenocarcinoma (mean IRS=6.6; 0.7; 2.7; respectively) (p<0.05). On the contrary, Musashi-1 expression was higher in BE and early ADC compared to GM and advanced ADC (NS).

CONCLUSION

Our results suggest that the stem cells could be present in premalignant lesions. EpCAM, CD44 and CD133 expression could be candidate markers for BE progression, whereas Musashi-1 may be a marker of the small intestinal features of Barrett's mucosa.

Expression of stem cell markers in oral cavity and oropharynx squamous cell carcinoma

OBJECTIVES

The aim of this study was to analyze the expression of CD24, CD44, CD133, ALDH1, CD29 (integrin-β1), and Ki-67 in squamous cell carcinoma of the oral cavity and oropharynx.

STUDY DESIGN

Fifty-two tumors and 21 metastatic lymph nodes were evaluated by using immunohistochemistry.

RESULTS

Seven of 52 cases (13.5%) showed positive cytoplasmic staining of aldehyde dehydrogenase 1; integrin-β1 was expressed in 45 of 50 cases (90%); 30 of 52 cases (57.7%) had positive membranous staining of CD44; CD24 was expressed in 44 of 50 cases (88%); and three of 52 cases (5.8%) stained positively for membranous CD133. Median proliferation rate, measured by Ki-67, was 37.1% for tumors. Five-year cancer-specific survival rates for the CD44-negative and CD44-positive groups were 74% and 38%, respectively, although this difference did not reach statistical significance (P = .052).

CONCLUSIONS

Our study demonstrated the expression of putative stem cell markers in squamous cell carcinoma of the oral cavity and oropharynx, with participation of CD44-positive cells in association with poor survival outcome.

Wnt signaling in cancer stem cells and colon cancer metastasis

Overactivation of Wnt signaling is a hallmark of colorectal cancer (CRC). The Wnt pathway is a key regulator of both the early and the later, more invasive, stages of CRC development. In the normal intestine and colon, Wnt signaling controls the homeostasis of intestinal stem cells (ISCs) that fuel, via proliferation, upward movement of progeny cells from the crypt bottom toward the villus and differentiation into all cell types that constitute the intestine. Studies in recent years suggested that cancer stem cells (CSCs), similar to ISCs of the crypts, consist of a small subpopulation of the tumor and are responsible for the initiation and progression of the disease. Although various ISC signature genes were also identified as CRC markers and some of these genes were even demonstrated to have a direct functional role in CRC development, the origin of CSCs and their contribution to cancer progression is still debated. Here, we describe studies supporting a relationship between Wnt-regulated CSCs and the progression of CRC.

Gene expression profiling combined with functional analysis identify integrin beta1 (ITGB1) as a potential prognosis biomarker in triple negative breast cancer

Triple negative breast cancer (TNBC) accounts for approximately 15-20% of all types of breast cancer, and treatment is still limited. This type of breast cancer shows a high risk of recurrence, visceral metastasis, a worse prognosis, and shorter distant metastasis-free survival. Several studies have been reported that genetics factors are associated with breast cancer disease progression and patients' survival. In this study, we combined Taiwanese microarray data from the GEO database and The Cancer Genome Atlas (TCGA) database to study the role of Integrin Beta1 (ITGB1) in TNBC. Two triple negative breast cancer cell lines (MDA-MB-231; MDA-MB-468) were used to validate the functions of ITGB1. We found that a higher ITGB1 gene expression level was associated to lower survival. Silencing of ITGB1 inhibited TNBC cell migration, invasion and store-operated calcium influx. Our study provided a potential candidate biomarker for breast cancer cells migration, invasion and TNBC patients' survival.

A Mouse Model of Targeted Musashi1 Expression in Whole Intestinal Epithelium Suggests Regulatory Roles in Cell Cycle and Stemness

The intestinal epithelium is very peculiar for its continuous cell renewal, fuelled by multipotent stem cells localized within the crypts of Lieberkühn. Several lines of evidence have established the evolutionary conserved RNA-binding protein Musashi1 as a marker of adult stem cells, including those of the intestinal epithelium, and revealed its roles in stem cell self-renewal and cell fate determination. Previous studies from our laboratories have shown that Musashi1 controls stem cell-like features in medulloblastoma, glioblastoma, and breast cancer cells, and has pro-proliferative and pro-tumorigenic properties in intestinal epithelial progenitor cells in vitro. To undertake a detailed study of Musashi1's function in the intestinal epithelium in vivo, we have generated a mouse model, referred to as v-Msi, overexpressing Musashi1 specifically in the entire intestinal epithelium. Compared with wild type litters, v-Msi1 mice exhibited increased intestinal crypt size accompanied by enhanced proliferation. Comparative transcriptomics by RNA-seq revealed Musashi1's association with gut stem cell signature, cell cycle, DNA replication, and drug metabolism. Finally, we identified and validated three novel mRNA targets that are stabilized by Musashi1, Ccnd1 (Cyclin D1), Cdk6, and Sox4. In conclusion, the targeted expression of Musashi1 in the intestinal epithelium in vivo increases the cell proliferation rate and strongly suggests its action on stem cells activity. This is due to the modulation of a complex network of gene functions and pathways including drug metabolism, cell cycle, and DNA synthesis and repair.

Msi1 promotes tumor growth and cell proliferation by targeting cell cycle checkpoint proteins p21, p27 and p53 in cervical carcinomas

Musashi RNA-binding protein1 (Msi1), a member of the RNA-binding protein family, has been reported to be a diagnostic marker and potential therapeutic target in some cancers, its function in cervical cancer remains unknown. In this study, we found Msi1 was highly expressed in cervical cancer tissues, and over-expressing Msi1 in cervical cancer cells enhanced tumor formation and cell proliferation and accelerated cells into the S phase. Whereas, down-regulating Msi1 by shRNA in cervical cancer cells inhibited tumor formation and cell proliferation and slowed cell into the S phase, suggesting that Msi1 might act as cell cycle regulator. Immunohistochemistry assay showed the negative correlation between Msi1 and p21, p27 and p53, suggesting that Msi1 might regulate these cycle regulators in cervical cancer. Moreover, the expression of the p21, p27 and p53 proteins were down-regulated in Msi1 overexpressing cervical cancer cells and up-regulated in shMsi1 cervical cancer cells. Luciferase assays and RNA-protein binding assays confirmed that Msi1 could bind to the mRNA 3′UTRs of p21, p27 and p53 and suppress the translation of these proteins. Our findings provide new evidence that Msi1 might promote cell proliferation by accelerating the cell cycle by directly targeting p21, p27 and p53.

Functional polymorphisms of ITGB1 are associated with clinical outcome of Chinese patients with resected colorectal cancer

PURPOSE

Integrin β1 (ITGB1) has been recognized to play a major role in tumor growth, invasion and metastasis. However, effects of single-nucleotide polymorphisms (SNPs) in ITGB1 gene on the prognosis of patients with colorectal cancer (CRC) have not been reported.

METHODS

A total of 372 patients with resected colorectal adenocarcinoma were enrolled in our study. Three functional SNPs (rs2230395, rs1187075 and rs1187076) in ITGB1 were selected and genotyped using the Sequenom iPLEX genotyping system.

RESULTS

We identified two SNPs (rs2230395 and rs1187075) in ITGB1 gene to be significantly associated with CRC overall survival (OS). Compared with the homozygous wild-type (AA) and heterozygous variant (AC), rs2230395 homozygous variant (CC) conferred a 1.55-fold (95 % CI 1.00-2.41, P = 0.049) increased risk of death. Similar result was obtained for homozygous variant (AA) in rs1187075 with a 1.62-fold (95 % CI 1.08-2.42, P = 0.020). In stratified analysis, this association in rs2230395 remained to be significant in patients receiving chemotherapy, but not in those without chemotherapy. We further evaluated the effects of chemotherapy on CRC survival in subgroups stratified by rs2230395 and rs1187075 genotypes. We found that chemotherapy resulted in a significantly better OS in patients with the homozygous wild-type (WW) or heterozygous variant (WV) genotype in both rs2230395 and rs1187075 when compared with patients with homozygous variant (VV) genotype.

CONCLUSIONS

Our data suggest that ITGB1 SNPs might be a prognostic biomarker for CRC patients, especially in those receiving chemotherapy. Our findings warrant validation in larger independent populations.

Natural product (-)-gossypol inhibits colon cancer cell growth by targeting RNA-binding protein Musashi-1

Musashi-1 (MSI1) is an RNA-binding protein that acts as a translation activator or repressor of target mRNAs. The best-characterized MSI1 target is Numb mRNA, whose encoded protein negatively regulates Notch signaling. Additional MSI1 targets include the mRNAs for the tumor suppressor protein APC that regulates Wnt signaling and the cyclin-dependent kinase inhibitor P21(WAF-1). We hypothesized that increased expression of NUMB, P21 and APC, through inhibition of MSI1 RNA-binding activity might be an effective way to simultaneously downregulate Wnt and Notch signaling, thus blocking the growth of a broad range of cancer cells. We used a fluorescence polarization assay to screen for small molecules that disrupt the binding of MSI1 to its consensus RNA binding site. One of the top hits was (-)-gossypol (Ki = 476 ± 273 nM), a natural product from cottonseed, known to have potent anti-tumor activity and which has recently completed Phase IIb clinical trials for prostate cancer. Surface plasmon resonance and nuclear magnetic resonance studies demonstrate a direct interaction of (-)-gossypol with the RNA binding pocket of MSI1. We further showed that (-)-gossypol reduces Notch/Wnt signaling in several colon cancer cell lines having high levels of MSI1, with reduced SURVIVIN expression and increased apoptosis/autophagy. Finally, we showed that orally administered (-)-gossypol inhibits colon cancer growth in a mouse xenograft model. Our study identifies (-)-gossypol as a potential small molecule inhibitor of MSI1-RNA interaction, and suggests that inhibition of MSI1's RNA binding activity may be an effective anti-cancer strategy.

Transformation of the intestinal epithelium by the MSI2 RNA-binding protein

The MSI2 RNA binding protein is a potent oncogene playing key roles in hematopoietic stem cell homeostasis and malignant hematopoiesis. Here we demonstrate that MSI2 is expressed in the intestinal stem cell compartment, that its expression is elevated in colorectal adenocarcinomas, and that MSI2 loss of function abrogates colorectal cancer cell growth. MSI2 gain of function in the intestinal epithelium in a drug inducible mouse model is sufficient to phenocopy many of the morphological and molecular consequences of acute loss of the APC tumor suppressor in the intestinal epithelium in a Wnt-independent manner. Transcriptome-wide RNA-binding analysis indicates that MSI2 acts as a pleiotropic inhibitor of known intestinal tumor suppressors including Lrig1, Bmpr1a, Cdkn1a, and Pten. Finally, we demonstrate that inhibition of the PDK-AKT-mTORC1 axis rescues oncogenic consequences of MSI2 induction. Taken together, our findings identify MSI2 as a central component in an unappreciated oncogenic pathway promoting intestinal transformation.

Cancer stem cell marker Musashi-1 rs2522137 genotype is associated with an increased risk of lung cancer

Gene single nucleotide polymorphisms (SNPs) have been extensively studied in association with development and prognosis of various malignancies. However, the potential role of genetic polymorphisms of cancer stem cell (CSC) marker genes with respect to cancer risk has not been examined. We conducted a case-control study involving a total of 1000 subjects (500 lung cancer patients and 500 age-matched cancer-free controls) from northeastern China. Lung cancer risk was analyzed in a logistic regression model in association with genotypes of four lung CSC marker genes (CD133, ALDH1, Musashi-1, and EpCAM). Using univariate analysis, the Musashi-1 rs2522137 GG genotype was found to be associated with a higher incidence of lung cancer compared with the TT genotype. No significant associations were observed for gene variants of CD133, ALDH1, or EpCAM. In multivariate analysis, Musashi-1 rs2522137 was still significantly associated with lung cancer when environmental and lifestyle factors were incorporated in the model, including lower BMI; family history of cancer; prior diagnosis of chronic obstructive pulmonary disease, pneumonia, or pulmonary tuberculosis; occupational exposure to pesticide; occupational exposure to gasoline or diesel fuel; heavier smoking; and exposure to heavy cooking emissions. The value of the area under the receiver-operating characteristic (ROC) curve (AUC) was 0.7686. To our knowledge, this is the first report to show an association between a Musashi-1 genotype and lung cancer risk. Further, the prediction model in this study may be useful in determining individuals with high risk of lung cancer.

NOTCH3 signaling regulates MUSASHI-1 expression in metastatic colorectal cancer cells

MUSASHI-1 (MSI-1) is a well-established stem cell marker in both normal and malignant colon cells and it acts by positively regulating the NOTCH pathway through inactivation of NUMB, a NOTCH signaling repressor. To date, the mechanisms of regulation of MSI-1 levels remain largely unknown. Here, we investigated the regulation of MSI-1 by NOTCH signaling in colorectal cancer cell lines and in primary cultures of colorectal cancer metastases. Stimulation by the NOTCH ligand DLL4 was associated with an increase of MSI-1 mRNA and protein levels, and this phenomenon was prevented by the addition of an antibody neutralizing NOTCH2/3 but not NOTCH1. Moreover, forced expression of activated NOTCH3 increased MSI-1 levels, whereas silencing of NOTCH3 by short hairpin RNA reduced MSI-1 levels in both colorectal cancer cells and CRC tumor xenografts. Consistent with these findings, enforced NOTCH3 expression or stimulation by DLL4 increased levels of activated NOTCH1 in colorectal cell lines. Finally, treatment of colorectal cancer cells with anti-NOTCH2/3 antibody increased NUMB protein while significantly reducing formation of tumor cell spheroids. This novel feed-forward circuit involving DLL4, NOTCH3, MSI-1, NUMB, and NOTCH1 may be relevant for regulation of NOTCH signaling in physiologic processes as well as in tumor development. With regard to therapeutic implications, NOTCH3-specific drugs could represent a valuable strategy to limit NOTCH signaling in the context of colorectal cancers overexpressing this receptor.

Musashi1 as a potential therapeutic target and diagnostic marker for lung cancer

Lung cancer remains one of the leading causes of cancer-related deaths worldwide with a 5-year survival rate of less than 20%. One approach to improving survival is the identification of biomarkers to detect early stage disease. In this study, we investigated the potential of the stem cell and progenitor cell marker, Musashi1 (Msi1), as a diagnostic marker and potential therapeutic target for lung cancer. Functional studies in A549 bronchioalveolar carcinoma and NCI-H520 squamous cell carcinoma cells revealed that Msi1 was enriched in spheroid cultures of tumor cells and in the CD133+ cell population. Downregulation of Msi1 by lentivirus-mediated expression of an Msi1 shRNA reduced spheroid colony proliferation. Growth inhibition was associated with reduced nuclear localization of β-catenin and inhibition of the processing of intracellular Notch. In primary lung cancer, Msi1 protein expression was elevated in 86% of 202 tissue microarray specimens, and Msi1 mRNA was increased in 80% of 118 bronchoscopic biopsies, including metastatic disease, but was rarely detected in adjacent normal lung tissue and in non-malignant diseased tissue. Msi1 was expressed in a diffuse pattern in most tumor subtypes, except in squamous cell carcinomas, where it appeared in a focal pattern in 50% of specimens. Thus, Msi1 is a sensitive and specific diagnostic marker for all lung cancer subtypes.

Cancer stem cells in colorectal cancer from pathogenesis to therapy: Controversies and perspectives

Colorectal cancer remains one of the most common and lethal malignancies worldwide despite the use of various therapeutic strategies. A better understanding of the mechanisms responsible for tumor initiation and progression is essential for the development of novel, more powerful therapies. The traditional, so-called “stochastic model” of tumor development, which assumes that each cancer cell is tumorigenic, has been deeply challenged during the past decade by the identification of cancer stem cells (CSCs), a biologically distinct subset of cells within the bulk of tumor mass. This discovery led to the development of the hierarchical model of tumorigenesis which assumes that only CSCs have the ability to initiate tumor growth, both at primary and metastatic sites. This model implies that the elimination of all CSCs is fundamental to eradicate tumors and that failure to do so might be responsible for the occurrence of relapses and/or metastases frequently observed in the clinical management of colorectal cancer patients. Identification and isolation of CSCs is essential for a better understanding of their role in the tumorigenetic process and for the development of CSC-specific therapies. Several methods have been used for this purpose and many efforts have been focused on the identification of specific CSC-surface markers. This review provides an overview of the proposed roles of CSC in human colorectal tumorigenesis focusing on the most important molecules identified as CSC-specific markers in colorectal cancer and on the potential strategies for the development of CSC-targeted therapy.

Expression and significance of Musashi-1 in gastric cancer and precancerous lesions

AIM: To investigate expression of stem cell marker Musashi-1 (Msi-1) in relationship to tumorigenesis and progression of intestinal-type gastric cancer (GC).

METHODS: Endoscopic biopsy specimens and surgical specimens were obtained, including 54 cases of intestinal-type GC, 41 high-grade intraepithelial neoplasia, 57 low-grade intraepithelial neoplasia, 31 intestinal metaplasia, and 36 normal gastric mucosa. Specimens were fixed in 10% paraformaldehyde, conventionally dehydrated, embedded in paraffin, and sliced in 4-μm-thick serial sections. Two-step immunohistochemical staining was used to detect Msi-1 and proliferating cell nuclear antigen (PCNA) expression. Correlation analysis was conducted between Msi-1 and PCNA expression. The relationship between Msi-1 expression and clinicopathological parameters of GC was analyzed statistically.

RESULTS: There were significant differences in Msi-1 and PCNA expression in different pathological tissues (χ² = 15.37, P < 0.01; χ² = 115.36, P < 0.01). Msi-1 and PCNA-positive cells were restricted to the isthmus of normal gastric glands. Expression levels of Msi-1 and PCNA in intestinal metaplasia were significantly higher than in normal mucosa (U = 392.0, P < 0.05; U = 40.50, P < 0.01), whereas there was no significant difference compared to low or high-grade intraepithelial neoplasia. Msi-1 and PCNA expression in intestinal-type GC was higher than in high-grade intraepithelial neoplasia (U = 798.0, P < 0.05; U = 688.0, P < 0.01). There was a significantly positive correlation between Msi-1 and PCNA expression (r_s = 0.20, P < 0.01). Msi-1 expression in GC tissues was correlated with their lymph node metastasis and tumor node metastasis stage (χ² = 12.62, P < 0.01; χ² = 11.24, P < 0.05), but not with depth of invasion and the presence of distant metastasis.

CONCLUSION: Msi-1-positive cells may play a key role in the early events of gastric carcinogenesis and may be involved in invasion and metastasis of GC.

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

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

Drug-resistant colon cancer cells produce high carcinoembryonic antigen and might not be cancer-initiating cells

Purpose

We evaluated the higher levels of carcinoembryonic antigen (CEA) secreted by the LoVo human colon carcinoma cells in a medium containing anticancer drugs. Drug-resistant LoVo cells were analyzed by subcutaneously xenotransplanting them into mice. The aim of this study was to evaluate whether the drug-resistant cells isolated in this study were cancer-initiating cells, known also as cancer stem cells (CSCs).

Methods

The production of CEA was investigated in LoVo cells that were cultured with 0–10 mM of anticancer drugs, and we evaluated the increase in CEA production by the LoVo cells that were stimulated by anticancer drug treatment. The expression of several CSC markers in LoVo cells treated with anticancer drugs was also evaluated. Following anticancer drug treatment, LoVo cells were injected subcutaneously into the flanks of severe combined immunodeficiency mice in order to evaluate the CSC fraction.

Results

Production of CEA by LoVo cells was stimulated by the addition of anticancer drugs. Drug-resistant LoVo cells expressed lower levels of CSC markers, and LoVo cells treated with any of the anticancer drugs tested did not generate tumors within 8 weeks from when the cells were injected subcutaneously into severe combined immunodeficiency mice. These results suggest that the drug-resistant LoVo cells have a smaller population of CSCs than the untreated LoVo cells.

Conclusion

Production of CEA by LoVo cells can be stimulated by the addition of anticancer drugs. The drug-resistant subpopulation of LoVo colon cancer cells could stimulate the production of CEA, but these cells did not act as CSCs in in vivo tumor generation experiments.

The RNA-Binding Protein Musashi1: A Major Player in Intestinal Epithelium Renewal and Colon Cancer Development

Aberrant gene expression is the cause and the consequence of tumorigenesis. A major component of gene expression is translation regulation; a process whose main players are RNA-binding-proteins (RBPs). More than 800 RBPs have been identified in the human genome and several of them have been shown to control gene networks associated with relevant cancer processes. A more systematic characterization of RBPs starts to reveal that similar to transcription factors, they can function as tumor suppressors or oncogenes. A relevant example is Musashi1 (Msi1), which is emerging as a critical regulator of tumorigenesis in multiple cancer types, including colon cancer. Msi1 is a stem marker in several tissues and is critical in maintaining the balance between self-renewal and differentiation. However, a boost in Msi1 expression can most likely lead cells towards an oncogenic pathway. In this article, we discuss the parallels between Msi1 function in normal renewal of intestinal epithelium and in colon cancer.

Colorectal cancer stem cells

Colorectal cancer (CRC) is one of the most commonly diagnosed and lethal cancers worldwide. It is a multistep process that requires the accumulation of genetic/epigenetic aberrations. There are several issues concerning colorectal carcinogenesis that remain unanswered, such as the cell of origin and the type of cells that propagate the tumor after its initiation. There are two models of carcinogenesis: the stochastic and the cancer stem cell (CSC) model. According to the stochastic model, any kind of cell is capable of initiating and promoting cancer development, whereas the CSC model suggests that tumors are hierarchically organized and only CSCs possess cancer-promoting potential. Moreover, various molecular pathways, such as Wingless/Int (Wnt) and Notch, as well as the complex crosstalk network between microenvironment and CSCs, are involved in CRC. Identification of CSCs remains controversial due to the lack of widely accepted specific molecular markers. CSCs are responsible for tumor relapse, because conventional drugs fail to eliminate the CSC reservoir. Therefore, the design of CSC-targeted interventions is a rational target, which will enhance responsiveness to traditional therapeutic strategies and reduce local recurrence and metastasis. This review discusses the implications of the newly introduced CSC model in CRC, the markers used up to now for CSC identification, and its potential implications in the design of novel therapeutic approaches.

Aberrant expression of CD133 and musashi-1 in preneoplastic and neoplastic human oral squamous epithelium and their correlation with clinicopathological factors

BACKGROUND

The present study focuses on the expression pattern of the stem cell markers CD133 and Musashi-1 in precancerous and cancerous tissues of oral epithelium. The study also aims to investigate the correlation of CD133 and Musashi-1 expression with clinicopathological factors.

METHODS

Immunohistochemical analysis was done to investigate the expression pattern of CD133 and Musashi-1, whereas, the coexpression of CD133 and Musashi-1 was studied using immunofluorescence analysis.

RESULTS

A gradual increase in the expression of CD133 and Musashi-1 was observed from normal to dysplasia to carcinoma. In addition, the expression of CD133 and Musashi-1 shows significant difference between the stages and histological types of oral carcinoma. Interestingly, coexpression of CD133 and Musashi-1 was observed in oral carcinoma and CAL27 cells.

CONCLUSIONS

A gradual increase in the expression of CD133 and Musashi-1 from normal to dysplasia to carcinoma suggests the possible involvement of these 2 proteins in oral carcinogenesis. The overexpression of CD133 and Musashi-1 in advanced stages and also in poorly differentiated tumors reveals their relationship with invasion and differentiation status of oral carcinoma cells. Moreover, the significant positive correlation between CD133 and Musashi-1 expression suggests that they might have a functional relationship in oral carcinoma cells, which needs further investigation.

LGR5 is a negative regulator of tumourigenicity, antagonizes Wnt signalling and regulates cell adhesion in colorectal cancer cell lines

Background

LGR5 (Leucine-rich repeat-containing G-protein coupled receptor 5) is the most established marker for intestinal stem cells. Mouse models show that LGR5+ cells are the cells of origin of intestinal cancer, and LGR5 expression is elevated in human colorectal cancers, however very little is known about LGR5 function or its contribution to the stem cell phenotype and to colorectal cancer.

Principal Findings

We have modulated the expression of LGR5 by RNAi (inhibitory RNAs) or overexpression in colorectal cancer cell lines. Paradoxically, ablation of LGR5 induces increased invasion and anchorage-independent growth, and enhances tumourigenicity in xenografts experiments. Conversely, overexpression of LGR5 augments cell adhesion, reduces clonogenicity and attenuates tumourigenicity. Expression profiling revealed enhanced wnt signalling and upregulation of EMT genes upon knockdown of LGR5, with opposite changes in LGR5 overexpressing cells. These findings suggest that LGR5 is important in restricting stem cells to their niche, and that loss of LGR5 concomitant with activated wnt signalling may contribute to the invasive phenotype of colorectal carcinomas.

Selecting Potential Targetable Biomarkers for Imaging Purposes in Colorectal Cancer Using TArget Selection Criteria (TASC): A Novel Target Identification Tool

Peritoneal carcinomatosis (PC) of colorectal origin is associated with a poor prognosis. However, cytoreductive surgery combined with hyperthermic intraperitoneal chemotherapy is available for a selected group of PC patients, which significantly increases overall survival rates up to 30%. As a consequence, there is substantial room for improvement. Tumor targeting is expected to improve the treatment efficacy of colorectal cancer (CRC) further through 1) more sensitive preoperative tumor detection, thus reducing overtreatment; 2) better intraoperative detection and surgical elimination of residual disease using tumor-specific intraoperative imaging; and 3) tumor-specific targeted therapeutics. This review focuses, in particular, on the development of tumor-targeted imaging agents. A large number of biomarkers are known to be upregulated in CRC. However, to date, no validated criteria have been described for the selection of the most promising biomarkers for tumor targeting. Such a scoring system might improve the selection of the correct biomarker for imaging purposes. In this review, we present the TArget Selection Criteria (TASC) scoring system for selection of potential biomarkers for tumor-targeted imaging. By applying TASC to biomarkers for CRC, we identified seven biomarkers (carcinoembryonic antigen, CXC chemokine receptor 4, epidermal growth factor receptor, epithelial cell adhesion molecule, matrix metalloproteinases, mucin 1, and vascular endothelial growth factor A) that seem most suitable for tumor-targeted imaging applications in colorectal cancer. Further cross-validation studies in CRC and other tumor types are necessary to establish its definitive value.

Musashi-1 expression in atherosclerotic arteries and its relevance to the origin of arterial smooth muscle cells: histopathological findings and speculations

The origin of smooth muscle cells in developing atherosclerotic lesions is a controversial topic with accumulating evidence indicating that at least some arterial smooth muscle cells might originate from bone marrow-derived smooth muscle cell precursors circulating in the blood. The stem cell markers currently used for the identification of stem cells in the arterial intima can be expressed by a number of different cell types residing in the arterial wall, such as mast cells, endothelial cells and dendritic cells, which can make interpretation of the data obtained somewhat ambiguous. In the present study we examined whether the putative intestinal stem cell marker Musashi-1 is expressed in the arterial wall. Using a multiplexed tandem polymerase chain reaction method (MT-PCR) and immunohistochemistry, Musashi-1 expression was revealed in human coronary arterial wall tissue segments, and this finding was followed by the demonstration of significantly higher expression levels of Musashi-1 in atherosclerotic plaques compared with those in undiseased intimal sites. Double immunohistochemistry demonstrated that in the arterial wall Musashi-1 positive cells either did not display any specific markers of cells that are known to reside in the arterial intima or Musashi-1 was co-expressed by smooth muscle α-actin positive cells. Some Musashi-1 positive cells were found along the luminal surface of arteries as well as within microvessels formed in atherosclerotic plaques by neovascularization, which supports the possibility that Musashi-1 positive cells might intrude into the arterial wall from the blood and might even represent circulating smooth muscle cell precursors.

The overexpression of the putative gut stem cell marker Musashi-1 induces tumorigenesis through Wnt and Notch activation

The RNA-binding protein Musashi-1 (Msi1) has been proposed as a marker of intestinal epithelial stem cells. These cells are responsible for the continuous renewal of the intestinal epithelium. Although the function of Msi1 has been studied in several organs from different species and in mammalian cell lines, its function and molecular regulation in mouse intestinal epithelium progenitor cells are still undefined. We describe here that, in these cells, the expression of Msi1 is regulated by the canonical Wnt pathway, through a mechanism involving a functional Tcf/Lef binding site on its promoter. An in vitro study in intestinal epithelium primary cultures showed that Msi1 overexpression promotes progenitor proliferation and activates Wnt and Notch pathways. Moreover, Msi1-overexpressing cells exhibit tumorigenic properties in xenograft experiments. These data point to a positive feedback loop between Msi1 and Wnt in intestinal epithelial progenitors. They also suggest that Msi1 has oncogenic properties in these cells, probably through induction of both the Wnt and Notch pathways.

Expression of the putative stem cell marker Musashi-1 in Barrett's esophagus and esophageal adenocarcinoma

The cancer stem cell theory states that cancers contain tumor-forming cells that have the ability to self-renew as well as give rise to cells that differentiate. Cancer stem cells have been identified in several solid tumors, but stem cells in normal human esophagus or in Barrett's esophagus or adenocarcinoma have not been reported. Musashi-1 is expressed by the crypt base columnar cells identified as intestinal stem cells. In other diseases of the gastrointestinal tract, local inflammation of the tunica mucosa may be an initiating factor of alteration of focal tissue 'niches,' where dormant stem cells locate. The present study investigated whether Musashi-1 is expressed in the esophagus and its relation to immune inflammation of the mucosa in Barrett's esophagus and esophageal adenocarcinoma. A total of 41 esophageal tissue specimens from 41 patients were studied. Of these, 15 were esophageal adenocarcinoma, 17 were Barrett's esophagus (10 intestinal metaplasia and 7 dysplasia), and 9 were normal squamous esophagus tissue specimens from patients without esophageal pathology. Immunohistochemistry was performed using antibodies to Musashi-1 and to a set of cell type-specific markers. A multiplexed tandem polymerase chain reaction method was used to measure the relative mRNA expression levels of Musashi-1 and the specific dendritic cell marker dendritic cell-specific intercellular molecule-3 (ICAM-3)-grabbing nonintegrin. Immunohistochemistry demonstrated the presence of small numbers of Musashi-1+ cells scattered in the connective tissue stroma and within the epithelium in cardiac-type glands in biopsies from patients without Barrett's esophagus. Musashi-1 expression was present in Barrett's intestinal metaplasia and in dysplastic Barrett's in which the majority of epithelial cells in individual glands expressed this antigen. Expression of Musashi-1 was highest in esophageal adenocarcinoma, where it was most intense in glands that displayed features of early stages of adenocarcinoma formation. In contrast, Musashi-1 staining level was weaker in glands that displayed features of advanced adenocarcinoma. Double immunostaining with proliferating cell nuclear antigen showed low proliferation in the vast majority of Musashi-1+ cells. Musashi-1 mRNA expression levels were significantly higher in esophageal adenocarcinoma than in normal esophagus or Barrett's esophagus tissues. Dendritic cell-specific intercellular molecule-3 (ICAM-3)-grabbing nonintegrin (DC-SIGN) mRNA expression levels were significantly increased in both Barrett's tissues and adenocarcinoma tissues. Expression of the putative stem cell marker Musashi-1 is absent in normal squamous epithelium, weak in esophageal cardiac-type glands and Barrett's esophagus, and markedly increased in adenocarcinoma, especially in glands displaying features of early cancer development. Musashi-1 expressing cells may be significant in the etiology of Barrett's esophagus and adenocarcinoma, and perhaps even a cell of origin for this disease. We speculate that immune inflammation occurring in Barrett's esophagus alters the mucosal microenvironment in a manner which is favorable to the activation of dormant stem cells.

Role of RNA-Binding Proteins in Colorectal Carcinogenesis

RNA-binding proteins (RBPs) play key roles in the posttranscriptional regulation of gene expression. RBPs control various posttranscriptional events, including splicing, polyadenylation, mRNA stability, transport, and translation. It is becoming apparent that RBPs play a significant role in pathophysiologic conditions such as inflammation and cancer. More importantly, we and others have begun dissecting the role of mRNA stability and translation in regulating gene expression, dysregulation of which has serious consequences for the fate of the cell. In this article, we discuss this emerging area of posttranscriptional gene regulation and the role of RBPs in the aberrant expression of proteins in tumorigenesis.