Expression of a candidate marker for progenitor cells, Musashi-1, in the proliferative regions of human antrum and its decreased expression in intestinal metaplasia

Case report: A rare case of very well-differentiated gastric adenocarcinoma of gastric type with a lymphovascular invasion

Background

Very well-differentiated gastric adenocarcinoma (VWDA) is a rare variant of gastric cancer, for which the diagnostic criteria and clinical behavior are not fully established. We reported a case of an intramucosal VWDA of gastric type with a lymphovascular invasion (LVI).

Case presentation

A 67-year-old female was diagnosed as intramucosal gastric adenocarcinoma after a biopsy at the local hospital 3 weeks ago and then visited our hospital for further treatment. The endoscopic examination in our hospital showed a rough, slightly faded, 30-mm, flat, and elevated lesion on the lesser curvature of the middle gastric body. Histopathologically, the lesion consisted of superficial foveolar-type papillary adenocarcinoma and deep pyloric gland-type tubular adenocarcinoma. The immunostaining results showed that the foveolar-type papillary adenocarcinoma was positive for MUC5AC and had a high index of Ki-67, but the pyloric gland-type tubular adenocarcinoma was positive for MUC6 and had a low index of Ki-67. Both components were negative for MSH2 and MSH6, which suggested the high microsatellite instability phenotype. Moreover, a LVI was detected in the lesion. The pathological diagnosis was VWDA of gastric type.

Conclusion

The case has unique histological and immunophenotypic characteristics, which not only indicates the importance of architectural features in the diagnosis of VWDA but also further proves that the aggressive behavior of VWDA is correlated with tumor histological type and immunophenotype.

Expression of NR5A2, NUP153, HNF4A, USP15 and FNDC3B is consistent with their use as novel biomarkers for bovine mammary stem/progenitor cells

Mammary stem cells (MaSC) are essential for growth and maintenance of mammary epithelium. Previous studies have utilized morphological characteristics or retention of bromodeoxyuridine (BrdU) label to identify MaSC and progenitor cells, these approaches may not be feasible or may not identify all resident stem cells. Alternatively, these special cells may be identified by assessing protein and mRNA expression of appropriate markers. The focus of this study was to assess the staining patterns and in situ quantification of novel candidate markers for bovine MaSC/progenitor cells. The candidate markers for MaSC/progenitor cells for immunohistochemical analysis were: NR5A2, NUP153, HNF4A, USP15 and FNDC3B and for in situ transcripts quantification were HNF4A and NUP153. We also evaluated protein expression pattern of presumptive MaSC markers known from the literature namely, ALDH1, MSI1 and Notch3. We found that NR5A2, NUP153, HNF4A and USP15-labeled cells represented 2.5-6% of epithelial cells prepubertally and were distributed in a fashion consistent with the location and abundance of MaSC/progenitor cells. A transient increase (10-37%) in expression of these markers was observed at peak lactation. FNDC3B was localized mainly in the nucleus prepubertally and in the cytoplasm of myoepithelial cells and nuclei of a limited number of alveolar cells during lactation. Abundant expression (~ 48%) and luminal localization of ALDH1 precludes its use as a bovine MaSC marker but may include transamplifying progenitor cells. MSI1 staining was consistent with MaSC localization. Onset of lumen formation in mammary ducts of prepubertal gland was associated with Notch 3 expression in the apical surface of luminal cells. RNAscope analysis of HNF4A and NUP153 transcripts in calf mammary gland showed very low copy numbers in a few epithelial cells, supporting the idea that these markers are expressed by fewer cells of epithelial origin. This study suggests that NR5A2, NUP153, HNF4A, USP15 and FNDC3B are likely markers for bovine MaSC/progenitor cells. Quantification of RNA transcripts of HNF4A and NUP153 in bovine MEC as potential MaSC markers are novel. Further studies to correlate protein expression of these markers with their transcripts level using single cell analysis in larger samples in lactating cow at different physiological stages are warranted.

Musashi expression in intestinal stem cells attenuates radiation-induced decline in intestinal permeability and survival in Drosophila

Exposure to genotoxic stress by environmental agents or treatments, such as radiation therapy, can diminish healthspan and accelerate aging. We have developed a Drosophila melanogaster model to study the molecular effects of radiation-induced damage and repair. Utilizing a quantitative intestinal permeability assay, we performed an unbiased GWAS screen (using 156 strains from the Drosophila Genetic Reference Panel) to search for natural genetic variants that regulate radiation-induced gut permeability in adult D. melanogaster. From this screen, we identified an RNA binding protein, Musashi (msi), as one of the possible genes associated with changes in intestinal permeability upon radiation. The overexpression of msi promoted intestinal stem cell proliferation, which increased survival after irradiation and rescued radiation-induced intestinal permeability. In summary, we have established D. melanogaster as an expedient model system to study the effects of radiation-induced damage to the intestine in adults and have identified msi as a potential therapeutic target.

Density of Musashi‑1‑positive stem cells in the stomach of patients with irritable bowel syndrome

Irritable bowel syndrome (IBS) affects ~12% of the global population. Although the etiology of IBS is not completely understood, several factors are known to serve a pivotal role in its pathophysiology, including genetic factors, diet, the intestinal microbiota, gastrointestinal endocrine cells and low‑grade inflammation. Musashi‑1 is expressed by stem cells and their early progeny, and is used as a stem cell marker. The low density of intestinal endocrine cells in patients with IBS is thought to be caused by decreased numbers of intestinal stem cells and their differentiation into enteroendocrine cells. The present study employed Musashi‑1 as a marker to detect stem cells in the stomach of 54 patients with IBS and 51 healthy subjects. The patients and controls underwent standard gastroscopy, and biopsy samples were taken from the corpus and antrum. Immunohistochemical staining of gastrin, somatostatin and Mushasi‑1 was carried out and semi‑quantified by computerized image analysis. The density (number of positive cells/mm2 epithelium) of gastrin‑positive cells in the controls and patients with IBS were 337.9±560 and 531.0±908 (median ± range; P<0.0001), respectively. For somatostatin‑positive cells, the density reached 364.4±526.0 in the healthy controls and 150.7±514.0 in patients with IBS (P<0.0001). The density of Musashi‑1‑positive cells was defined as the number of cells per gastric or pyloric gland neck. In the corpus, Musashi‑1‑positive cells density reached 3.0±7.0 in the corpus of the healthy controls and 3.8±7.7 in the patients with IBS. Moreover, the corresponding values in the antrum were 6.0±6.0 and 6.0±6.0, respectively. The Musashi‑1‑positive cell density did not differ significantly between the controls and patients with IBS in the corpus or antrum (P=0.4 and 0.3, respectively). These findings indicated that changes in the stomach endocrine cells observed in patients with IBS may not be explained by an abnormality in stem cells like those found in the small and large intestines of these patients.

Signaling pathways involved in chronic myeloid leukemia pathogenesis: The importance of targeting Musashi2-Numb signaling to eradicate leukemia stem cells

OBJECTIVES

Chronic myeloid leukemia (CML) is a myeloid clonal proliferation disease defining by the presence of the Philadelphia chromosome that shows the movement of BCR-ABL1. In this study, the critical role of the Musashi2-Numb axis in determining cell fate and relationship of the axis to important signaling pathways such as Hedgehog and Notch that are essential for self-renewal pathways in CML stem cells will be reviewed meticulously.

MATERIALS AND METHODS

In this review, a PubMed search using the keywords of Leukemia, signaling pathways, Musashi2-Numb was performed, and then we summarized different research works .

RESULTS

Although tyrosine kinase inhibitors such as Imatinib significantly kill and remove the cell with BCR-ABL1 translocation, they are unable to target BCR-ABL1 leukemia stem cells. The main problem is stem cells resistance to Imatinib therapy. Therefore, the identification and control of downstream molecules/ signaling route of the BCR-ABL1 that are involved in the survival and self-renewal of leukemia stem cells can be an effective treatment strategy to eliminate leukemia stem cells, which supposed to be cured by Musashi2-Numb signaling pathway.

CONCLUSION

The control of molecules /pathways downstream of the BCR-ABL1 and targeting Musashi2-Numb can be an effective therapeutic strategy for treatment of chronic leukemia stem cells. While Musashi2 is a poor prognostic marker in leukemia, in treatment and strategy, it has significant diagnostic value.

Knockdown of MSI1 inhibits the proliferation of human oral squamous cell carcinoma by inactivating STAT3 signaling

Musashi RNA-binding protein 1 (MSI1) is highly expressed in several types of cancer; however, its role in oral squamous cell carcinoma (OSCC) remains unknown. The purpose of this study was to investigate the probable mechanism underlying the involvement of MSI1 in OSCC. The results demonstrated that MSI1 was upregulated in OSCC tissues, but not in adjacent healthy tissues. MSI1 silencing resulted in decreased cell proliferative, invasive and migrative capacity. In addition, MSI1 silencing led to cell cycle arrest at the S phase, downregulation of c-Myc and cyclin D1, and upregulation of p21 and p27 levels. Additional studies demonstrated that MSI1 suppression inhibited the activation of signal transducer and activator of transcription 3 (STAT3) signaling. Accordingly, the findings of the present study suggested that MSI1 silencing can suppress OSCC cell proliferation and progression, in part by inhibiting the activation of the c-Myc/STAT3 pathway.

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.

Expression of Putative Stem Cell Marker, Hepatocyte Nuclear Factor 4 Alpha, in Mammary Gland of Water Buffalo

Buffaloes account for more than 56% of total milk production in India. Cyclic remodeling of mammary glands of human, mice, cow, sheep, and goat is determined by mammary stem cells. It is logical to assume that buffalo mammary gland will have mammary stem/progenitor cells. Thus far, no report exists on identification of buffalo mammary stem cells. Hepatocyte nuclear factor 4 alpha (HNF4A) is a candidate marker for hepatic progenitor cells and has recently been suggested as a marker of bovine mammary stem/progenitor cells. We hypothesized that ( 1 ) HNF4A identifies putative buffalo mammary stem/progenitor cells and ( 2 ) the number of HNF4A-positive cells increases during mastitis. Sixteen buffalo mammary samples were collected from a local slaughterhouse. Hematoxylin and eosin staining were performed on 5-micron thick sections and on the basis of gross examination and histomorphology of the mammary glands, physiological stages of the animals were estimated as non-lactating (n = 4), mastitis (n = 9), and prepubertal (n = 3). In total, 24048 cells were counted (5-10 microscopic fields/animal; n = 16 animals) of which, 40% cells were mammary epithelial cells (MEC) and 60% cells were the stromal cells. The percentage of MEC in non-lactating animals was higher compared to mastitic animals (47.3% vs. 37.3%), which was likely due to loss of MEC in mastitis. HNF4A staining was observed in nuclei of MEC of ducts, alveoli, and stromal cells. Basal location and low frequency of HNF4A-positive MEC (ranges from 0.4-4.5%) were consistent with stem cell characteristics. Preliminary study showed coexpression of HNF4A with MSI1 (a mammary stem cell marker in sheep), suggesting HNF4A was likely to be a putative mammary stem/progenitor cell marker in buffalo. HNF4A-positive MEC (basal and luminal; light and dark stained) tended to be higher in non-lactating than the mastitic animals (8.73 ± 1.71% vs. 4.29 ± 1.19%; P = 0.07). The first hypothesis that HNF4A identify putative mammary stem/progenitor cells was confirmed but the second hypothesis that the number of mammary stem/progenitor cells decreases during mastitis was unsupported. This is the first report outlining the expression of HNF4A and identification of putative mammary stem/progenitor cells in buffalo mammary gland.

Peritoneal milky spots serve as a hypoxic niche and favor gastric cancer stem/progenitor cell peritoneal dissemination through hypoxia-inducible factor 1α

Peritoneal dissemination is the most common cause of death in gastric cancer patients. The hypoxic microenvironment plays a major role in controlling the tumor stem cell phenotype and is associated with patients' prognosis through hypoxia-inducible factor-1α (HIF-1α), a key transcriptional factor that responds to hypoxic stimuli. During the peritoneal dissemination process, gastric cancer stem/progenitor cells (GCSPCs) are thought to enter into and maintained in peritoneal milky spots (PMSs), which have hypoxic microenvironments. However, the mechanism through which the hypoxic environment of PMSs regulated GCSPC maintenance is still poorly understood. Here, we investigated whether hypoxic PMSs were an ideal cancer stem cell niche suitable for GCSPC engraftment. We also evaluated the mechanisms through which the HIF-1α-mediated hypoxic microenvironment regulated GCSPC fate. We observed a positive correlation between HIF-1α expression and gastric cancer peritoneal dissemination (GCPD) in gastric cancer patients. Furthermore, the GCSPC population expanded in primary gastric cancer cells under hypoxic condition in vitro, and hypoxic GCSPCs showed enhanced self-renewal ability, but reduced differentiation capacity, mediated by HIF-1α. In an animal model, GCSPCs preferentially resided in the hypoxic zone of PMSs; moreover, when the hypoxic microenvironment in PMSs was destroyed, GCPD was significantly alleviated. In conclusion, our results demonstrated that PMSs served as a hypoxic niche and favored GCSPCs peritoneal dissemination through HIF-1α both in vitro and in vivo. These results provided new insights into the GCPD process and may lead to advancements in the clinical treatment of gastric cancer.

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.

Genome-wide analysis of the oxyntic proliferative isthmus zone reveals ASPM as a possible gastric stem/progenitor cell marker over-expressed in cancer

The oxyntic proliferative isthmus zone contains the main stem/progenitor cells that provide for physiological renewal of the distinct mature cell lineages in the oxyntic epithelium of the stomach. These cells are also proposed to be the potential cells-of-origin of gastric cancer, although little is known about their molecular characteristics and specific biological markers are lacking. In this study, we developed a method for serial section-navigated laser microdissection to isolate cells from the proliferative isthmus zone of rat gastric oxyntic mucosa for genome-wide microarray gene expression analysis. Enrichment analysis showed a distinct gene expression profile for the isthmus zone, with genes regulating intracellular processes such as the cell cycle and ribosomal activity. The profile was also related to stem cell transcriptional networks and stomach neoplasia. Genes expressed uniquely in the isthmus zone were associated with E2F transcription factor 1 (E2F1), which participates in the self-renewal of stem cells and in gastric carcinogenesis. One of the unique genes was Aspm [Asp (abnormal spindle) homologue, microcephaly-associated (Drosophila)]. Here we show ASPM in single scattered epithelial cells located in the proliferative isthmus zone of rat, mouse and human oxyntic mucosa, which do not seem to be actively dividing. The ASPM-expressing cells are mainly mature cell marker-deficient, except for a limited overlap with cells with neuroendocrine and tuft cell features. Further, both ASPM and E2F1 were expressed in human gastric cancer cell lines and increased and correlated in human gastric adenocarcinomas compared to non-tumour mucosa, as shown by expression profile analyses and immunohistochemistry. The association between ASPM and the transcription factor E2F1 in gastric tissue is relevant, due to their common involvement in crucial cell fate-regulatory mechanisms. Our results thus introduce ASPM as a novel possible oxyntic stem/progenitor cell marker that may be involved in both normal gastric physiology and gastric carcinogenesis.

Sonic hedgehog-glioma associated oncogene homolog 1 signaling enhances drug resistance in CD44(+)/Musashi-1(+) gastric cancer stem cells

Drug resistance in gastric cancer largely results from the gastric cancer stem cells (GCSCs), which could be targeted to improve the efficacy of chemotherapy. In this study, we identified a subpopulation of GCSCs enriched in holoclones that expressed CD44(+)/Musashi-1(+) stem cell biomarkers, capable of self-renewal and proliferation. Enriched CD44(+)/Musashi-1(+) GCSCs demonstrated elevated expression of sonic hedgehog (SHH) and glioma-associated oncogene homolog 1 (GLI1), the well-known signaling pathway molecules involved in the drug resistance. Further, CD44(+)/Musashi-1(+) cells exhibited high drug efflux bump activity and were resistant to doxorubicin (Dox)-induced apoptosis, and unregulated the ATP-binding cassette sub-family G member 2 (ABCG2) expression,. The above effects on apoptosis were reversed in the presence of GLI inhibitors, GANT61 and GDC-0449, or by the knockdown of GLI1/SHH. Upon knockdown of GLI1, expression of ABCG2 was downregulated the antitumor effects were significantly improved as observed in the gastric cancer xenograft. Collectively, our study revealed that co-expression of CD44(+)/Musashi-1(+) could be used to identify GCSCs, which also accounts for the drug resistance in gastric cancer. SHH-GLI and its downstream effector ABCG2 could be better targeted to possibly improve the efficacy of chemotherapy in drug-resistant gastric cancers.

The Musashi family RNA-binding proteins in stem cells

The Musashi family is an evolutionarily conserved group of RNA-binding proteins. In mammal, two members of the group, Msi1 and Msi2, have been identified to date. Msi1 is considered to play roles in maintaining the stem cell status (stemness) of neural stem/progenitor cells in adults and in the development of central nervous system through translational regulation of its target mRNAs, which encode regulators of signal transduction and the cell cycle. Recently, strong expression of Msi1 in various somatic stem/progenitor cells of adult tissues, such as eye, gut, stomach, breast, and hair follicle, has been reported. The protein is also expressed in various cancer cells, and ectopically emerging cells have been found in neural tissues of patients with diseases involving neural disorder, including epilepsy. Many novel target mRNAs and regulatory pathways of Msi1 have been reported in recent years. Here, we present a review of the functions and action mechanisms of Msi1 protein and discuss possible directions for further study.

Downregulation of Msi1 suppresses the growth of human colon cancer by targeting p21cip1

Musashi1 (Msi1), a member of the RNA-binding protein (RBP) family, is highly expressed in neural progenitor or stem cells for the maintenance of stemness as well as in various cancers. Emerging studies have demonstrated that it regulates cell processes by translational activation or suppresses specifically bound mRNA. In the present study, we initially reported remarkably increased expression of Msi1 in colon cancer tissues compared with adjacent non-tumor tissues. Knockdown of Msi1 significantly suppressed the proliferation, colony formation, tumorsphere formation and the progression of implanted colon cancers, and induced cell cycle attest at G0/G1 phase, along with the upregulated expression of p21(cip1). Reporter assays using a chimeric mRNA that combined luciferase and the 3'-UTR of p21(cip1) revealed that Msi1 decreased the reporter activity through the specific motif. Thus, the current results suggested that downregulation of Msi1 could inhibit the growth of colon cancers and Msi1 may be a promising therapeutic target molecule for human colon cancers.

Multiple tumor suppressor microRNAs regulate telomerase and TCF7, an important transcriptional regulator of the Wnt pathway

The human TERT (hTERT) gene encodes the telomerase catalytic subunit which plays a role in telomerase regulation. Telomerase is activated in more than 90% of all human malignancies and understanding how telomerase is regulated is necessary for implementation of successful anti-cancer therapies. microRNAs (miRNAs) are important regulators of gene expression in eukaryotic cells but evidence of their role in telomerase regulation has not been documented. To determine whether hTERT activity is regulated by multiple miRNAs, eight miRNAs which have putative binding sites in the hTERT 3'UTR together with miR-138-5p were evaluated in luciferase assays with a reporter containing the hTERT 3'UTR. Six miRNAs (let-7g*, miR-133a, miR-138-5p, miR-342-5p, miR-491-5p, and miR-541-3p) specifically inhibited the expression of the reporter luciferase-driven constructs and let-7g*, miR-133a, miR-138-5p, and miR-491-5p also downregulated endogenous telomerase activity in cells. Moreover, all six miRNAs significantly inhibited cell proliferation. miRNAs (miR-133a, miR-138-5p, 342-5p, 491-5p, 541-3p) also have predicted binding sites within the 3'UTR of three genes involved in Wnt signaling (TCF7, MSI1, and PAX5). These miRNAs inhibited the expression of the luciferase reporter constructs containing 3'UTRs of these genes and downregulated protein expression of the TCF7 transcription factor, which mediates the canonical Wnt pathway. Together, these results suggest the existence of a miRNA regulatory network involving the hTERT and Wnt pathway.

Musashi-1 expression and clinicopathological significance in young gastric cancer patients: a matched case-control study

Musashi-1 (Msi-1) is proposed to be a marker of progenitor cells in the human gastric mucosa. We examined Msi-1 expression and localization in surgical specimens of gastric cancer in young patients using immunohistochemistry and tested associations of Msi-1 expression with clinicopathological features. Patients (n=611) with gastric cancer who underwent radical gastrectomy were included in the present study. To minimize confounding effects, we matched 26 gastric cancer patients 30 years of age or younger (age ≤30) with 26 patients 60 years of age or older (age ≥60). The groups were matched by gender, tumor histological type and tumor stage. Gastric cancer in the younger patients was significantly associated with female gender and with diffuse histological type, compared with 585 gastric cancer patients older than 31 years. Msi-1 expression was more frequently upregulated in gastric cancer in young patients than in patients older than 60 years. Msi-1 expression was significantly associated with diffuse histological type, depth of tumor invasion, lymph node metastasis and tumor stage in the 26 young patients with gastric cancer. Univariate Kaplan-Meier survival analysis identified Msi-1 expression as a significantly negative factor in the survival of young gastric cancer patients. However, Msi-1 expression was not significantly associated with survival in the 26 matched older patients. According to mucin phenotype, the gastric foveolar type predominated in Msi-1-positive gastric cancers. Our principal findings included a significantly higher level of Msi-1 expression in younger gastric cancer patients compared to older ones, and a probable association of tumor Msi-1 expression in young gastric cancer patients with more aggressive tumor type.

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.

The effects of hedgehog on RNA binding protein Msi1 during the osteogenic differentiation of human cord blood-derived mesenchymal stem cells

Human umbilical cord blood (UCB)-derived mesenchymal stem cells (MSCs) are useful tools for regenerative medicine due to their capacity for self-renewal and multi-lineage differentiation. The appropriate clinical application of MSCs for regenerative medicine requires an integrated understanding of multiple signaling pathways that regulate cell proliferation, stemness and differentiation. However, the potential molecular mechanisms mediating these functions are not completely understood. The effects of hedgehog (Hh) signaling on the osteogenic differentiation of MSCs are still controversial, and the underlying mechanisms are unclear. In the present study, we evaluated the direct effects of Hh signaling on the osteogenic differentiation of hUCB-MSCs and investigated potential downstream regulatory mechanisms responsible for Hh signaling. We observed that Hh signaling acts as a negative regulator of osteogenic differentiation through the suppression of RNA-binding Msi1, which in turn suppresses the expression of Wnt1 and the miR-148 family, especially miR-148b. Moreover, Hh and Msi1 are considered to be potential stemness markers of hUCB-MSCs due to their differentiation-dependent expression profiles. This study provides new insights into mechanisms regulating MSC differentiation and may have implications for a variety of therapeutic applications in the clinic.

Development of intestinal organoids as tissue surrogates: cell composition and the epigenetic control of differentiation

Intestinal organoids are multicellular crypt-like structures that can be derived from adult intestinal stem cells (ISCs), embryonic stem cells (ESCs) or induced pluripotent stem cells (IPSCs). Here we show that intestinal organoids generated from mouse ESCs were enriched in ISCs and early progenitors. Treatment of these organoids with a γ-secretase inhibitor increased Math1 and decreased Hes1 expression, indicating Notch signaling regulates ISC differentiation in these organoids. Lgr5 and Tert positive ISCs constituted approximately 10% and 20% of the organoids. As found in native tissue, Lgr5 and Tert expressing cells resolved into two discreet populations, which were stable over time. Intestinal organoids derived from cancer-prone Apc(Min/+) mice showed similar numbers of ISCs, but had reduced Math1 expression, indicating a suppressed secretory cell differentiation potential (as found in intestinal tissue). Apc(Min/+) organoids were used to screen epigenetically active compounds for those that increased Math1 expression and organoid differentiation (including HDAC inhibitors, Sirtuin (SIRT) modulators and methyltransferase inhibitors). Broad-spectrum HDAC inhibitors increased both Math1 and Muc2 expression, indicating an ability to promote the suppressed secretory cell differentiation pathway. Other epigenetic compounds had a diverse impact on cell differentiation, with a strong negative correlation between those that activated the secretory marker Muc2 and those that activated the absorptive cell marker Fabp2. These data show that ESC-derived intestinal organoids can be derived in large numbers, contain distinct ISC types and can be used to screen for agents that promote cell differentiation through different lineage pathways.

Gastric cancer stem cells: a novel therapeutic target

Gastric cancer remains one of the leading causes of global cancer mortality. Multipotent gastric stem cells have been identified in both mouse and human stomachs, and they play an essential role in the self-renewal and homeostasis of gastric mucosa. There are several environmental and genetic factors known to promote gastric cancer. In recent years, numerous in vitro and in vivo studies suggest that gastric cancer may originate from normal stem cells or bone marrow-derived mesenchymal cells, and that gastric tumors contain cancer stem cells. Cancer stem cells are believed to share a common microenvironment with normal niche, which play an important role in gastric cancer and tumor growth. This mini-review presents a brief overview of the recent developments in gastric cancer stem cell research. The knowledge gained by studying cancer stem cells in gastric mucosa will support the development of novel therapeutic strategies for gastric cancer.

The effects of Hedgehog on the RNA-binding protein Msi1 in the proliferation and apoptosis of mesenchymal stem cells

Human umbilical cord blood (UCB)-derived mesenchymal stem cells (MSCs) are essential tools for regenerative medicine due to their capacity for self-renewal and multi-lineage differentiation. As MSCs are found in very small numbers in various tissues, in vitro cell expansion is an essential step that is needed before these cells can be used in clinical applications. Therefore, it is important to identify and characterize factors that are involved in MSC proliferation and apoptosis. In the present study, we focused on Hedgehog (Hh) signaling because several studies have proposed that Hh signaling plays a critical role in controlling the proliferation of stem and progenitor cells. However, the molecular mechanisms underlying the effects on the proliferation and apoptosis of MSCs remain unclear. In this study, we evaluated the direct effects of Hh signaling on the proliferation and apoptosis of hUCB-MSCs as well as investigated potential downstream regulatory mechanisms that may be responsible for Hh signaling. We observed that the Hedgehog agonist purmorphamine enhanced cell proliferation and suppressed apoptosis through the RNA-binding protein Msi1 by regulating the expression of an oncoprotein (i.e., c-Myc), a cell cycle regulatory molecule (i.e., p21(CIP1,WAF1)) and two microRNAs (i.e., miRNA-148a and miRNA-148b). This study provides novel insights into the molecular mechanisms regulating the self-renewal capability of MSCs with relevance to clinical applications.

Characterization of side population cells isolated from the gastric cancer cell line SGC-7901

Side population (SP) cells are a subset of stem cells that have been isolated from several different gastrointestinal cancer cell lines. Using flow cytometry and the DNA-binding dye Hoechst 33342, we isolated SP cells from SGC-7901 human gastric tumor cell lines and found that they comprise 2.3±0.78% of the tumor cells. Using the Cell Counting Kit-8 (CCK-8) assay, we demonstrated that SP cells have a stronger proliferative activity than non-SP cells. Additionally, we observed tumor mass formation following the cultivation of SP cells in serum-free medium, indicating the capability of these cells for self-renewal. SP cells were observed to undergo non-symmetrical division, which is characteristic of stem cells. A drug resistance assay revealed that SP cells have a high survival rate when exposed to the chemotherapy drug 5-fluorouracil; the results of western blot analysis suggest that this stems from the abundant expression of the chemoresistance-associated proteins ABCG2 and Bcl-2. We also used fluorescence quantitative PCR to reveal that SP cells have relatively high expression levels of the stem cell-related genes Musashi-1 and CD44. In vivo experiments in mice revealed that the subcutaneous injection of 2×10³ SP cells resulted in the formation of tumors, while the injection of 2×10⁴ non-SP cells did not. Cumulatively, our results suggest that gastric tumorigenesis associated with SGC-7901 may partly be driven by the activity of SP cells, which exhibit certain biological characteristics of stem cells. Our results also show that the SP cell sorting method is an effective means for isolating and identifying gastric cancer stem cells during early screening.

Helicobacter pylori infection induced gastric cancer; advance in gastric stem cell research and the remaining challenges

Helicobacter pylori infection is the major cause of gastric cancer, which remains an important health care challenge. Recent investigation in gastric stem cell or progenitor cell biology has uncovered valuable information in understanding the gastric gland renewal and maintenance of homeostasis, they also provide clues for further defining the mechanisms by which gastric cancer may originate and progress. Lgr5, Villin-promoter, TFF2-mRNA and Mist have recently been identified as gastric stem/progenitor cell markers; their identification enriched our understanding on the gastric stem cell pathobiology during chronic inflammation and metaplasia. In addition, advance in gastric cancer stem cell markers such as CD44, CD90, CD133, Musashi-1 reveal novel information on tumor cell behavior and disease progression implicated for therapeutics. However, two critical questions remain to be of considerable challenges for future exploration; one is how H. pylori or chronic inflammation affects gastric stem cell or their progenitors, which give rise to mucus-, acid-, pepsinogen-, and hormone-secreting cell lineages. Another one is how bacterial infection or inflammation induces oncogenic transformation and propagates into tumors. Focus on the interactions of H. pylori with gastric stem/progenitor cells and their microenvironment will be instrumental to decipher the initiation and origin of gastric cancer. Future studies in these areas will be critical to uncover molecular mechanisms of chronic inflammation-mediated oncogenic transformation and provide options for cancer prevention and intervention. We review recent progress and discuss future research directions in these important research fields.

Drosophila Rbp6 is an orthologue of vertebrate Msi-1 and Msi-2, but does not function redundantly with dMsi to regulate germline stem cell behaviour

The vertebrate RNA-binding proteins, Musashi-1 (Msi-1) and Musashi-2 (Msi-2) are expressed in multiple stem cell populations. A role for Musashi proteins in preventing stem cell differentiation has been suggested from genetic analysis of the Drosophila family member, dMsi, and both vertebrate Msi proteins function co-operatively to regulate neural stem cell behaviour. Here we have identified a second Drosophila Msi family member, Rbp6, which shares more amino acid identity with vertebrate Msi-1 and Msi-2 than dMsi. We generated an antibody that detects most Rbp6 splice isoforms and show that Rbp6 is expressed in multiple tissues throughout development. However, Rbp6 deletion mutants generated in this study are viable and fertile, and show only minor defects. We used Drosophila spermatogonial germline stem cells (GSC’s) as a model to test whether Drosophila Msi proteins function redundantly to regulate stem cell behaviour. However, like vertebrate Msi-1 and Msi-2, Rbp6 and Msi do not appear to be co-expressed in spermatogenic GSC’s and do not function co-operatively in the regulation of GSC maintenance. Thus while two Msi family members are present in Drosophila, the function of the family members have diverged.

Sequential expression of putative stem cell markers in gastric carcinogenesis

BACKGROUND

Gastric carcinogenesis has been well documented in the step-wise histopathological model, known as Correa pathway. Several biomarkers including CD44, Musashi-1 and CD133 have been reported as putative stem cell (PSC) markers.

METHODS

We investigated expression of PSC markers CD44, Musashi-1 and CD133 in relation to gastric carcinogenesis and prognosis and chemoresponse. Immunohistochemistry staining was performed in gastric cancer (GC) clinical specimens representing different steps of the Correa pathway. Gastric cancer samples taken before and after neoadjuvant chemotherapy with docetaxel, cisplatin and capecitabine (DCX) were also evaluated for PSC marker expression.

RESULTS

We showed that the expression of three PSC markers was significantly elevated in GC relative to normal gastric mucosa (P<0.001 for each marker). Precancerous lesions, including intestinal metaplasia and dysplasia, demonstrated increased expression of CD44 and Musashi-1. CD133 was predominantly expressed along the border between intramucosal carcinoma and connective tissue at later stages. High CD44 and CD133 expression showed prognostic value for worse patient survival (P=0.014 and P=0.019, respectively). A small number of tumours with high expression of CD44 and CD133 showed pathological response to DCX-based neoadjuvant chemotherapy.

CONCLUSION

CD44 and Musashi-1 are frequently expressed in both premalignant gastric lesions and invasive GC, whereas CD133 expression is restricted mainly to neoplastic tissues.

Identification of a novel intronic enhancer responsible for the transcriptional regulation of musashi1 in neural stem/progenitor cells

Background

The specific genetic regulation of neural primordial cell determination is of great interest in stem cell biology. The Musashi1 (Msi1) protein, which belongs to an evolutionarily conserved family of RNA-binding proteins, is a marker for neural stem/progenitor cells (NS/PCs) in the embryonic and post-natal central nervous system (CNS). Msi1 regulates the translation of its downstream targets, including m-Numb and p21 mRNAs. In vitro experiments using knockout mice have shown that Msi1 and its isoform Musashi2 (Msi2) keep NS/PCs in an undifferentiated and proliferative state. Msi1 is expressed not only in NS/PCs, but also in other somatic stem cells and in tumours. Based on previous findings, Msi1 is likely to be a key regulator for maintaining the characteristics of self-renewing stem cells. However, the mechanisms regulating Msi1 expression are not yet clear.

Results

To identify the DNA region affecting Msi1 transcription, we inserted the fusion gene ffLuc, comprised of the fluorescent Venus protein and firefly Luciferase, at the translation initiation site of the mouse Msi1 gene locus contained in a 184-kb bacterial artificial chromosome (BAC). Fluorescence and Luciferase activity, reflecting the Msi1 transcriptional activity, were observed in a stable BAC-carrying embryonic stem cell line when it was induced toward neural lineage differentiation by retinoic acid treatment. When neuronal differentiation was induced in embryoid body (EB)-derived neurosphere cells, reporter signals were detected in Msi1-positive NSCs and GFAP-positive astrocytes, but not in MAP2-positive neurons. By introducing deletions into the BAC reporter gene and conducting further reporter experiments using a minimized enhancer region, we identified a region, "D5E2," that is responsible for Msi1 transcription in NS/PCs.

Conclusions

A regulatory element for Msi1 transcription in NS/PCs is located in the sixth intron of the Msi1 gene. The 595-bp D5E2 intronic enhancer can transactivate Msi1 gene expression with cell-type specificity markedly similar to the endogenous Msi1 expression patterns.

Cell origin and premalignant lesions of gastric signet-ring cell carcinoma: a histopathologic study

AIM: To investigate the cell origin and premalignant lesions of gastric signet-ring cell carcinoma (SRCC).

METHODS: A total of 42 cases of early gastric SRCC were included in this study. The histological morphology of gastric SRCC was observed. Differentiation markers MUC5AC and MUC6 were labeled by immunohistochemical double-staining of gastric SRCC tissue. The expression of Ki-67 and gastrointestinal stem/progenitor cell marker musashi-1 in SRCC was detected by immunohistochemistry. Additionally, the immunophenotype of gastric glands adjacent to carcinoma was also detected.

RESULTS: Early gastric SRCC was characterized by a two-layered structure consisting of superficial layer and basal layer. The superficial layer contained typical large signet-ring cells that possessed abundant cytoplasm, whereas the basal layer was composed of small-sized primitive cancer cells with a high nucleus/cytoplasm ratio. Cells in the basal layer shared common morphologic features and a similar anatomic location with those in the proliferative zone of gastric glands. These cells were negative for both MUC5AC and MUC6, or merely exhibited a weak MUC5AC expression. Compared with the superficial layer, the percentages of Ki-67- and musashi-1-positive cells were significantly higher in the basal layer (t = 31.0 and 22.8, respectively, both P < 0.01). Cells in the basal layer could differentiate into typical signet-ring cells, which resembles the differentiation process of proliferitive zone cells into gastric pit cells. Dysplasia of the proliferative zone of gastric glands adjacent to SRCC was noted, and dysplastic cells in the proliferative zone were phenotypically consistent with cancer cells in the basal layer.

CONCLUSION: Gastric SRCC may originate from MUC5AC-/lowMUC6- pre-pit cells in the proliferative zone of gastric glands. Dysplasia of the proliferative zone may represent the premalignant lesions of gastric SRCC.

The RNA binding protein Musashi1 regulates apoptosis, gene expression and stress granule formation in urothelial carcinoma cells

The RNA-binding protein Musashi1 (MSI1) is a marker of progenitor cells in the nervous system functioning as a translational repressor. We detected MSI1 mRNA in several bladder carcinoma cell lines, but not in cultured normal uroepithelial cells, whereas the paralogous MSI2 gene was broadly expressed. Knockdown of MSI1 expression by siRNA induced apoptosis and a severe decline in cell numbers in 5637 bladder carcinoma cells. Microarray analysis of gene expression changes after MSI1 knockdown significantly up-regulated 735 genes, but down-regulated only 31. Up-regulated mRNAs contained a highly significantly greater number and density of Musashi binding sites. Therefore, a much larger set of mRNAs may be regulated by Musashi1, which may affect not only their translation, but also their turnover. The study confirmed p21^CIP1 and Numb proteins as targets of Musashi1, suggesting additionally p27^KIP1 in cell-cycle regulation and Jagged-1 in Notch signalling. A significant number of up-regulated genes encoded components of stress granules (SGs), an organelle involved in translational regulation and mRNA turnover, and impacting on apoptosis. Accordingly, heat shock induced SG formation was augmented by Musashi1 down-regulation. Our data show that ectopic MSI1 expression may contribute to tumorigenesis in selected bladder cancers through multiple mechanisms and reveal a previously unrecognized function of Musashi1 in the regulation of SG formation.

Gastric carcinogenesis and the cancer stem cell hypothesis

Normal stem cells (NSCs) are reported to exist in most tissues, including the brain, bone marrow, and probably the gastrointestinal tract. In the latter case, they are thought to possess both the self-renewal capacity and asymmetrical division capacity to generate progenitor cells which differentiate into epithelial cells. NSCs in the normal gastric mucosa are thought to be present in the proliferative zone of the neck/isthmus region, and to undergo a complex bipolar migration from the neck/isthmus region either upward or downward, becoming differentiated normal epithelial cells. NSCs in human gastric mucosa are difficult to identify due to the current lack of a useful marker. A precise definition of cancer stem cells (CSCs) is still under discussion. CSCs are generally defined as malignant cells with NSC capacity. However, many studies of CSCs have demonstrated their rapid growth and high metastatic potential, while NSCs are thought to be slow-growing and self-renewing, and to lack functional capacities such as cell migration and attachment. Recent evidence suggests the existence of CSCs in a wide variety of solid tumors. In this review, we will discuss the existence and cell biology of gastric NSCs and CSCs. We will also discuss whether gastric CSCs originate as organ-specific stem cells or as bone marrow-derived cells (BMDCs). Under certain conditions, the local microenvironment may promote the development of gastric cancer. Thus, Helicobacter pylori infection and the accompanying chronic inflammatory processes will supply critical initiators inducing cell growth and the tissue repair response, leading to carcinogenesis. This mechanism will be discussed in light of stem cell research. Progress in stem cell research in the gastric field is still limited to experimental animal models. However, recent studies should enhance our understanding of human cancer biology, and provide novel tools for the treatment of incurable gastric cancer.

Proteomic Helicobacter pylori biomarkers discriminating between duodenal ulcer and gastric cancer

Protein patterns of 129 Helicobacter pylori strains isolated from Korean and Colombian patients suffering from duodenal ulcer or gastric cancer were analyzed by the high-throughput methodology SELDI-TOF-MS. Eighteen statistically significant candidate biomarkers discriminating between the two clinical outcomes were selected by using the Mann-Whitney test. Three biomarker proteins were purified and identified as a neutrophil-activating protein NapA (HU HPAG1_0821), a RNA-binding protein (HPAG1_0813), and a DNA-binding histone-like protein HU, respectively (jhp0228). These novel biomarkers can be used for development of diagnostic assays predicting the evolution to gastric cancer in H. pylori-infected patients.

Abnormal growth factor/cytokine network in gastric cancer

Gastric cancer cells express a broad spectrum of the growth factor/cytokine receptor systems that organize the complex interaction between cancer cells and stromal cells in tumor microenvironment, which confers cell growth, apoptosis, morphogenesis, angiogenesis, progression and metastasis. However, these abnormal growth factor/cytokine networks differ in the two histological types of gastric cancer. Importantly, activation of nuclear factor-kB pathway by Helicobacter pylori infection may act as a key player for induction of growth factor/cytokine networks in gastritis and pathogenesis of gastric cancer. Better understanding of these events will no doubt provide new approaches for biomarkers of diagnosis and effective therapeutic targeting of gastric cancer.

Helicobacter pylori infection induces candidate stem cell marker Musashi-1 in the human gastric epithelium

Musashi-1 (Msi-1), a mammalian neural RNA-binding protein, has been found to play important roles in the maintenance of stem cell states and differentiation in neural stem cells and mouse intestinal cells. We explored Msi-1 expression and its potential implications in the human stomach. Reverse transcription-PCR revealed that Msi-1 levels were significantly higher in the corpus than in antrum in Helicobacter pylori (Hp)-infected patients (n = 49) (P < 0.00001) in paired biopsy samples, whereas they were low and comparable at these two sites in Hp-negative patients (n = 31). Msi-1 levels were significantly higher in the Hp-infected corpus (n = 107) than in the Hp-negative corpus (n = 69) (P < 0.00000001). Immunohistochemistry and in situ hybridization demonstrated that Msi-1 was expressed at the base and neck/isthmus region of the fundic glands and partly co-expressed in Ki-67-positive cells in the corpus and antrum. Msi-1 levels correlated with Hp density (P < 0.05). Based on these results, we conclude that Hp infection strongly induces Msi-1 in the corpus. Given its expression in dividing cells, Msi-1 may modulate the state of gastric progenitor cells.

Expression of stem cell markers in human astrocytomas of different WHO grades

According to new hypotheses astrocytomas/gliomas either arise from or attract neural stem cells. Biological markers, particularly antigenic markers, have played a significant role for the characterization of these tumour stem cells (TSCc). Because these studies have been performed with single experimental samples mostly from gliomas, we investigated the expression of the stem cell markers CD133/Prominin, Nestin, Sox-2, Musashi-1, CXCR4, Flt-4/VEGFR-3 and CD105/Endoglin in 72 astrocytomas of different WHO-grades and compared it to normal adult human brain. Expression of their mRNA was quantified by quantitative RT-PCR, of their protein by counting immunopositive cells. In contrast to normal brain, tumour samples showed a high variability for the expression of all markers. However, their mean expression was significantly increased in astrocytomas, but this depended on the WHO grade only for CD133, Nestin, Sox-2 and Musashi-1. Confocal microscopy revealed that these markers mostly could be co-stained with glial fibrillary acidic protein, a marker for astoglial cells, but less frequently with the proliferation marker Ki-67/MIB-1. These markers sometimes, but not necessarily could be co-stained with each other in complex patterns. Our results show that most astrocytomas contain considerable portions of cells expressing stem cell markers. It appears that some of these cells originate from tumour genesis (supporting the stem cell hypothesis) while others are attracted by the tumours. Further functional markers are required to differentiate these TSC-types.

Drosophila spermatogenesis: insights into testicular cancer

Geneticists have a long history of studying reproduction in the fruitfly, Drosophila melanogaster, and in recent years it has become apparent that many of the genes that regulate invertebrate reproduction have been conserved through vertebrate evolution. As with other higher eukaryotes, spermatogenesis in Drosophila is characterized by a regenerative germline stem cell population that divides asymmetrically to produce mitotic spermatogonia which will eventually differentiate into spermatocytes. Germline tumours consisting of undifferentiated germ cells have been associated with both loss-of-function mutations and ectopic gene expression. While the genesis of these tumours may not be identical to human germ cell tumours many of the genes that regulate stem cell proliferation and aberrant over-proliferation in the Drosophila testis provide candidate molecules that may underlie the genetic programmes that contribute to human testicular oncogenesis.

Enhanced therapeutic efficacy of oncolytic herpes vector G207 against human non-small cell lung cancer--expression of an RNA-binding protein, Musashi1, as a marker for the tailored gene therapy

BACKGROUND

Oncolytic herpes vectors like G207 have shown considerable promise in the treatment of solid tumors, but their potency must be enhanced for the full achievement of therapeutic efficacy. Deletion of the innate gamma34.5 gene made these vectors extremely safe, but their efficacy was also severely attenuated. Use of tumor-specific promoters is one method to direct toxicity and enhance efficacy against tumors. Recently, Musashi1 has been shown expressed in some tumor tissues.

METHODS

Eleven human cancer cell lines including five non-small cell lung cancers (NSCLCs) were investigated. Musashi1 mRNA expression was examined by RT-PCR analysis. Western blotting was also performed. Transcriptional activity of P/musashi1 in NSCLCs was assayed by GFP reporter plasmids. Then we constructed a defective amplicon vector containing musashi1 promoter/ICP34.5 with G207 as helper virus (dvM345). In vitro cytotoxicity against NSCLCs and growth characteristics of helper virus were examined. A Lu-99 subcutaneous tumor model was used in an animal study. The tumor volume treated with G207 alone or dvM345 was measured.

RESULTS

Musashi1 mRNA was detected in four cell lines. Two in five NSCLCs were positive, and P/musashi1 was proved functional within them. Against these cell lines, dvM345 showed enhanced cytotoxicity, and helper viral growth was augmented. A subcutaneous tumor study confirmed the enhanced therapeutic efficacy of G207 by dvM345 without compromising safety.

CONCLUSIONS

These results suggest that Musashi1 might be involved in the development of several carcinomas including NSCLC. In the context of oncolytic herpes vector strategy, the P/musashi1-ICP34.5 method could be used for the treatment of cancers expressing Musashi1.

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The RNA-binding protein Musashi is required intrinsically to maintain stem cell identity

A key goal of regenerative medicine is an understanding of the genetic factors that define the properties of stem cells. However, stem cell research in mammalian tissue has been hampered by a paucity of stem cell-specific markers. Although increasing evidence suggests that members of the Musashi (Msi) family of RNA-binding proteins play important functions in progenitor cells, it remains unclear whether there is a stem cell-autonomous requirement for Msi because of an inability to distinguish stem cells from early-lineage cells in mammalian tissues. Here, using the Drosophila testis as a model system for the study of stem cell regulation, we show specific evidence for a cell-autonomous requirement for Msi family proteins in regulating stem cell differentiation, leading to the identification of an RNA-binding protein required for spermatogonial stem cell maintenance. We found that loss of Msi function disrupts the balance between germ-line stem cell renewal and differentiation, resulting in the premature differentiation of germ-line stem cells. Moreover, we found that, although Msi is expressed in both somatic and germ cells, Msi function is required intrinsically in stem cells for maintenance of stem cell identity. We also discovered a requirement for Msi function in male meiosis, revealing that Msi has distinct roles at different stages of germ cell differentiation. We describe the complementary expression patterns of the murine Msi paralogues Msi1 and Msi2 during spermatogenesis, which support the idea of distinct, evolutionarily conserved roles of Msi.

Expression of RNA-binding protein Musashi in hair follicle development and hair cycle progression

Epithelial stem cells reside in the hair follicle (HF) bulge region and possess the ability to differentiate into a variety of cutaneous epithelial cells. The evolutionarily conserved Musashi family of RNA-binding proteins is associated with maintenance and/or asymmetric cell division of neural progenitor cells, and a mammalian Musashi protein is expressed in various epithelial stem/progenitor cells, including gut, stomach, and mammary gland. Thus, we hypothesized that Musashi might be expressed in stem cells and early progenitor cells of HF epithelium. Reverse transcriptase-polymerase chain reaction and immunoblotting identified Musashi-1 (Msi-1) and Musashi-2 (Msi-2) mRNA and protein in cultured mouse keratinocytes, but only Msi-1 was identified in human keratinocytes. In mice, immunohistochemical studies showed that Msi-1 and Msi-2 were expressed in the epidermis and HFs from E14.5 until adulthood. In the early anagen phase, Msi-1 and Msi-2 were expressed in the bulge and secondary germ cells and subsequently in inner root sheath (IRS) cells, especially the middle IRS cells, during the late anagen phase. In human skin, Msi-1 was detected in fetal HF cells but not in adult HFs. These observations suggest that Musashi functions not only in the asymmetric division of early progenitor cells but also in the differentiation of IRS cells during HF development and hair cycle progression.