Musashi1 modulates mammary progenitor cell expansion through proliferin-mediated activation of the Wnt and Notch pathways

Unraveling the Bivalent and Rapid Interactions Between a Multivalent RNA Recognition Motif and RNA: A Kinetic Approach

The kinetics of the interaction between Musashi-1 (MSI1) and RNA have been characterized using surface plasmon resonance biosensor analysis. Truncated variants of human MSI1 encompassing the two homologous RNA recognition motifs (RRM1 and RRM2) in tandem (aa 1-200), and the two RRMs in isolation (aa 1-103 and aa 104-200, respectively) were produced. The proteins were injected over sensor surfaces with immobilized RNA, varying in sequence and length, and with one or two RRM binding motifs. The interactions of the individual RRMs with all RNA variants were well described by a 1:1 interaction model. The interaction between the MSI1 variant encompassing both RRM motifs was bivalent and rapid for all RNA variants. Due to difficulties in fitting this complex data using standard procedures, we devised a new method to quantify the interactions. It revealed that two RRMs in tandem resulted in a significantly longer residence time than a single RRM. It also showed that RNA with double UAG binding motifs and potential hairpin structures forms less stable bivalent complexes with MSI1 than the single UAG motif containing linear RNA. Substituting the UAG binding motif with a CAG sequence resulted in a reduction of the affinity of the individual RRMs, but for MSI1, this reduction was strongly enhanced, demonstrating the importance of bivalency for specificity. This study has provided new insights into the interaction between MSI1 and RNA and an understanding of how individual domains contribute to the overall interaction. It provides an explanation for why many RNA-binding proteins contain dual RRMs.

Characterization of E-Cadherin, SSEA-1, MSI-1, and SOX-2 Expression and Their Association with Pale Cells in Adenomyosis

Adenomyosis (AM) is a gynecological disease characterized by the invasion of endometrial glands and stroma within the myometrium. The etiology and pathogenesis of AM remain inadequately understood. Pale cells were identified as a novel cell type characterized by the absence of desmosomal contacts and light-colored cytoplasm. These cells were observed to migrate individually through ultra-micro ruptures in the basal membrane of the endometrial glands, translocating into the stroma and then further into the myometrium. Our study aimed to explore the possible stem cell properties of these pale cells. Forty hysterectomy specimens were analyzed using immunohistochemistry and immunofluorescence to assess negative E-cadherin expression and the positive expression of stem cell markers SSEA-1, MSI-1, and SOX-2. Immunohistochemical analysis revealed the presence of pale cells and occasionally rounded, enlarged E-cadherin-negative cells predominantly in the basal endometrial epithelium. The stem cell marker SSEA-1 was significantly elevated in the basalis epithelium, as well as in the ectopic epithelium. SSEA-1 positive cells were also identified in the stroma and myometrium. Sporadic colocalization of SSEA-1+/E-cadherin- cells was confirmed through immunofluorescence. The positive staining of pale cells for SSEA-1 and MSI-1 was also confirmed at the ultrastructural level by immunoelectron microscopy. These findings indicate that pale cells may possess stem cell characteristics, particularly a positive SSEA-1 profile, warranting further in vitro investigation into their role in the pathogenesis of adenomyosis.

A novel method for culturing enteric neurons generates neurospheres containing functional myenteric neuronal subtypes

BACKGROUND

The enteric nervous system (ENS) is comprised of neurons, glia, and neural progenitor cells that regulate essential gastrointestinal functions. Advances in high-efficiency enteric neuron culture would facilitate discoveries surrounding ENS regulatory processes, pathophysiology, and therapeutics.

NEW METHOD

Development of a simple, robust, one-step method to culture murine enteric neurospheres in a 3D matrix that supports neural growth and differentiation.

RESULTS

Myenteric plexus cells isolated from the entire length of adult murine small intestine formed ≥3000 neurospheres within 7 days. Matrigel-embedded neurospheres exhibited abundant neural stem and progenitor cells expressing Sox2, Sox10 and Msi1 by day 4. By day 5, neural progenitor cell marker Nestin appeared in the periphery of neurospheres prior to differentiation. Neurospheres produced extensive neurons and neurites, confirmed by Tubulin beta III, PGP9.5, HuD/C, and NeuN immunofluorescence, including neural subtypes Calretinin, ChAT, and nNOS following 8 days of differentiation. Individual neurons within and external to neurospheres generated depolarization induced action potentials which were inhibited in the presence of sodium channel blocker, Tetrodotoxin. Differentiated neurospheres also contained a limited number of glia and endothelial cells.

COMPARISON WITH EXISTING METHODS

This novel one-step neurosphere growth and differentiation culture system, in 3D format (in the presence of GDNF, EGF, and FGF2), allows for ∼2-fold increase in neurosphere count in the derivation of enteric neurons with measurable action potentials.

CONCLUSION

Our method describes a novel, robust 3D culture of electrophysiologically active enteric neurons from adult myenteric neural stem and progenitor cells.

Dysregulated Stem Cell Markers Musashi-1 and Musashi-2 are Associated with Therapy Resistance in Inflammatory Breast Cancer

BACKGROUND AND AIM

While preliminary evidence points to pro-tumorigenic roles for the Musashi (MSI) RNA-binding proteins Musashi-1 (MSI1) and Musashi-2 (MSI2) in some breast cancer subtypes, no data exist for inflammatory breast cancer (IBC).

METHODS

MSI gene expression was quantified in IBC SUM149PT cells. We then used small interfering RNA-based MSI1 and MSI2 double knockdown (DKD) to understand gene expression and functional changes upon MSI depletion. We characterized cancer stem cell characteristics, cell apoptosis and cell cycle progression via flow cytometry, mammospheres via spheroid assays, migration and proliferation via digital holographic microscopy, and cell viability using BrdU assays. Chemoresistance was determined for paclitaxel and cisplatin with MTT assays and radioresistance was assessed with clonogenic analyses. In parallel, we supported our in vitro data by analyzing publicly available patient IBC gene expression datasets.

RESULTS

MSI1 and MSI2 are upregulated in breast cancer generally and IBC specifically. MSI2 is more commonly expressed compared to MSI1. MSI DKD attenuated proliferation, cell cycle progression, migration, and cell viability while increasing apoptosis. Stem cell characteristics CD44(+)/CD24(-), TERT and Oct4 were associated with MSI expression in vivo and were decreased in vitro after MSI DKD as was ALDH expression and mammosphere formation. In vivo, chemoresistant tumors were characterized by MSI upregulation upon chemotherapy application. In vitro, MSI DKD was able to alleviate chemo- and radioresistance.

CONCLUSIONS

The Musashi RNA binding proteins are dysregulated in IBC and associated with tumor proliferation, cancer stem cell phenotype, chemo- and radioresistance. MSI downregulation alleviates therapy resistance and attenuates tumor proliferation in vitro.

The Musashi RNA-binding proteins in female cancers: insights on molecular mechanisms and therapeutic relevance

RNA-binding proteins have increasingly been identified as important regulators of gene expression given their ability to bind distinct RNA sequences and regulate their fate. Mounting evidence suggests that RNA-binding proteins are involved in the onset and progression of multiple malignancies, prompting increasing interest in their potential for therapeutic intervention.The Musashi RNA binding proteins Musashi-1 and Musashi-2 were initially identified as developmental factors of the nervous system but have more recently been found to be ubiquitously expressed in physiological tissues and may be involved in pathological cell behavior. Both proteins are increasingly investigated in cancers given dysregulation in multiple tumor entities, including in female malignancies. Recent data suggest that the Musashi proteins serve as cancer stem cell markers as they contribute to cancer cell proliferation and therapy resistance, prompting efforts to identify mechanisms to target them. However, as the picture remains incomplete, continuous efforts to elucidate their role in different signaling pathways remain ongoing.In this review, we focus on the roles of Musashi proteins in tumors of the female - breast, endometrial, ovarian and cervical cancer - as we aim to summarize current knowledge and discuss future perspectives.

Expression of receptor-type tumour endothelial marker 8 in carcinoma cells showing luminal progenitor-like phenotypes in canine mammary gland carcinomas

This study aimed to investigate the expression of receptor-type tumour endothelial marker 8 (TEM8RT) in canine mammary gland carcinomas (CMGCs) using immunohistochemistry and to evaluate the association between carcinoma cell TEM8RT expression and tumour histological features, histological grades and the differentiation status of neoplastic epithelial cells. TEM8RT expression was more frequently detected in simple carcinomas (tubular and tubulopapillary) than in solid carcinomas, and it was significantly correlated with histological grade Ⅰ tumours and a low mitotic index. Additionally, TEM8RT⁺ carcinoma cells were more frequently found in CMGCs showing luminal progenitor-like phenotypes, such as Notch1⁺, CK19⁺/CK5⁺/CD49f⁺ and CK19⁺/CK5^-/CD49f⁺. Double-labelling immunofluorescence detection techniques confirmed that most TEM8RT⁺ carcinoma cells expressed CD49f, Notch1 and CK19. However, TEM8RT immunoreactivity was not found in carcinoma cells expressing GATA3, which upregulates mature luminal cell differentiation. Furthermore, TEM8RT⁺ carcinoma cells were detected in a few CMGCs showing basal/stem cell-like phenotypes such as CK19^-/CK5⁺/CD49f⁺ and CK19^-/CK5⁺/CD49f^-. These findings indicate that TEM8RT is expressed in luminal progenitor-like carcinoma cells in CMGCs. Since TEM8 enhances self-renewal in human mammary stem/progenitor cells, it also may be involved in maintenance of luminal progenitor-like carcinoma cells, resulting in prevention of their transition to basal/stem cell-like carcinoma cells and development of less malignant CMGCs. Therefore, TEM8RT may be useful for indicating prognostic outcomes and identifying the possible ontogeny of carcinoma cells in mammary gland tumours.

Knockdown of the stem cell marker Musashi-1 inhibits endometrial cancer growth and sensitizes cells to radiation

Background

Endometrial carcinoma is the most common gynecological cancer in Europe. Musashi-1 is known to be a key regulator of endometrial cancer stem cells and a negative prognostic marker. In the present study, we aimed to understand growth and gene expression patterns in endometrial carcinoma after Musashi-1 knockdown in vitro and in vivo. Changes in therapeutic resistance were also assessed.

Methods

First, we performed analyses to understand Musashi-1 expression patterns using The Cancer Genome Atlas database. We then proceeded to assess effects of small interfering RNA-based Musashi-1 targeting in two endometrial carcinoma cell lines, Ishikawa and KLE. After quantifying baseline changes in cell metabolism, we used MTT tests to assess chemotherapy effects and colony formation assays to understand changes in radioresistance. For mechanistic study, we used quantitative polymerase chain reaction (qPCR) and western blotting of key Musashi-1 target genes and compared results to primary tissue database studies. Finally, xenograft experiments in a mouse model helped understand in vivo effects of Musashi-1 knockdown.

Results

Musashi-1 is aberrantly expressed in primary tumor tissues. In vitro, silencing of Musashi-1 resulted in a strong decline in cell proliferation and radioresistance, while chemoresistance remained unchanged. Loss of Musashi-1 led to downregulation of telomerase, DNA-dependent protein kinase, the Notch pathway and overexpression of cyclin-dependent kinase inhibitor p21, the latter of which we identified as a key mediator of Msi-1 knockdown-related anti-proliferative signaling. In vivo, the anti-proliferative effect was confirmed, with Msi-1 knockdown tumors being about 40% reduced in size.

Conclusions

Musashi-1 knockdown resulted in a strong decrease in endometrial cancer proliferation and a loss of radioresistance, suggesting therapeutic potential.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-022-02891-3.

Differences in stem cell marker and osteopontin expression in primary and recurrent glioblastoma

Background

Despite of a multimodal approach, recurrences can hardly be prevented in glioblastoma. This may be in part due to so called glioma stem cells. However, there is no established marker to identify these stem cells.

Methods

Paired samples from glioma patients were analyzed by immunohistochemistry for expression of the following stem cell markers: CD133, Musashi, Nanog, Nestin, octamer-binding transcription factor 4 (Oct4), and sex determining region Y-box 2 (Sox2). In addition, the expression of osteopontin (OPN) was investigated. The relative number of positively stained cells was determined. By means of Kaplan–Meier analysis, a possible association with overall survival by marker expression was investigated.

Results

Sixty tissue samples from 30 patients (17 male, 13 female) were available for analysis. For Nestin, Musashi and OPN a significant increase was seen. There was also an increase (not significant) for CD133 and Oct4. Patients with mutated Isocitrate Dehydrogenase-1/2 (IDH-1/2) status had a reduced expression for CD133 and Nestin in their recurrent tumors. Significant correlations were seen for CD133 and Nanog between OPN in the primary and recurrent tumor and between CD133 and Nestin in recurrent tumors. By confocal imaging we could demonstrate a co-expression of CD133 and Nestin within recurrent glioma cells. Patients with high CD133 expression had a worse prognosis (22.6 vs 41.1 months, p = 0.013). A similar trend was seen for elevated Nestin levels (24.9 vs 41.1 months, p = 0.08).

Conclusions

Most of the evaluated markers showed an increased expression in their recurrent tumor. CD133 and Nestin were associated with survival and are candidate markers for further clinical investigation.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12935-022-02510-4.

Research progress on RNA‑binding proteins in breast cancer (Review)

Breast cancer is the most common malignancy among women, and the abnormal regulation of gene expression serves an important role in its occurrence and development. However, the molecular mechanisms underlying gene expression are highly complex and heterogeneous, and RNA-binding proteins (RBPs) are among the key regulatory factors. RBPs bind targets in an environment-dependent or environment-independent manner to influence mRNA stability and the translation of genes involved in the formation, progression, metastasis and treatment of breast cancer. Due to the growing interest in these regulators, the present review summarizes the most influential studies concerning RBPs associated with breast cancer to elucidate the role of RBPs in breast cancer and to assess how they interact with other key pathways to provide new molecular targets for the diagnosis and treatment of breast cancer.

Characterization of Two Novel EF-Hand Proteins Identifies a Clade of Putative Ca2+-Binding Protein Specific to the Ambulacraria

In recent years, transcriptomic databases have become one of the main sources for protein discovery. In our studies of nervous system and digestive tract regeneration in echinoderms, we have identified several transcripts that have attracted our attention. One of these molecules corresponds to a previously unidentified transcript (Orpin) from the sea cucumber Holothuria glaberrima that appeared to be upregulated during intestinal regeneration. We have now identified a second highly similar sequence and analyzed the predicted proteins using bioinformatics tools. Both sequences have EF-hand motifs characteristic of calcium-binding proteins (CaBPs) and N-terminal signal peptides. Sequence comparison analyses such as multiple sequence alignments and phylogenetic analyses only showed significant similarity to sequences from other echinoderms or from hemichordates. Semi-quantitative RT-PCR analyses revealed that transcripts from these sequences are expressed in various tissues including muscle, haemal system, gonads, and mesentery. However, contrary to previous reports, there was no significant differential expression in regenerating tissues. Nonetheless, the identification of unique features in the predicted proteins and their presence in the holothurian draft genome suggest that these might comprise a novel subfamily of EF-hand containing proteins specific to the Ambulacraria clade.

MYC Hyperactivates Wnt Signaling in APC/CTNNB1-Mutated Colorectal Cancer Cells through miR-92a-Dependent Repression of DKK3

Activation of Wnt signaling is among the earliest events in colon cancer development. It is achieved either via activating mutations in the CTNNB1 gene encoding β-catenin, the key transcription factor in the Wnt pathway, or most commonly by inactivating mutations affecting APC, a major β-catenin binding partner and negative regulator. However, our analysis of recent Pan Cancer Atlas data revealed that CTNNB1 mutations significantly co-occur with those affecting Wnt receptor complex components (e.g., Frizzled and LRP6), underscoring the importance of additional regulatory events even in the presence of common APC/CTNNB1 mutations. In our effort to identify non-mutational hyperactivating events, we determined that KRAS-transformed murine colonocytes overexpressing direct β-catenin target MYC show significant upregulation of the Wnt signaling pathway and reduced expression of Dickkopf 3 (DKK3), a reported ligand for Wnt co-receptors. We demonstrate that MYC suppresses DKK3 transcription through one of miR-17-92 cluster miRNAs, miR-92a. We further examined the role of DKK3 by overexpression and knockdown and discovered that DKK3 suppresses Wnt signaling in Apc-null murine colonic organoids and human colon cancer cells despite the presence of downstream activating mutations in the Wnt pathway. Conversely, MYC overexpression in the same cell lines resulted in hyperactive Wnt signaling, acquisition of epithelial-to-mesenchymal transition markers, and enhanced migration/invasion in vitro and metastasis in a syngeneic orthotopic mouse colon cancer model. IMPLICATIONS: Our results suggest that the MYC→miR-92a-|DKK3 axis hyperactivates Wnt signaling, forming a feed-forward oncogenic loop.

Asymmetric cell division of mammary stem cells

Somatic stem cells are distinguished by their capacity to regenerate themselves and also to produce daughter cells that will differentiate. Self-renewal is achieved through the process of asymmetric cell division which helps to sustain tissue morphogenesis as well as maintain homeostasis. Asymmetric cell division results in the development of two daughter cells with different fates after a single mitosis. Only one daughter cell maintains "stemness" while the other differentiates and achieves a non-stem cell fate. Stem cells also have the capacity to undergo symmetric division of cells that results in the development of two daughter cells which are identical. Symmetric division results in the expansion of the stem cell population. Imbalances and deregulations in these processes can result in diseases such as cancer. Adult mammary stem cells (MaSCs) are a group of cells that play a critical role in the expansion of the mammary gland during puberty and any subsequent pregnancies. Furthermore, given the relatively long lifespans and their capability to undergo self-renewal, adult stem cells have been suggested as ideal candidates for transformation events that lead to the development of cancer. With the possibility that MaSCs can act as the source cells for distinct breast cancer types; understanding their regulation is an important field of research. In this review, we discuss asymmetric cell division in breast/mammary stem cells and implications on further research. We focus on the background history of asymmetric cell division, asymmetric cell division monitoring techniques, identified molecular mechanisms of asymmetric stem cell division, and the role asymmetric cell division may play in breast cancer.

Musashi-1-A Stemness RBP for Cancer Therapy?

The RNA-binding protein Musashi-1 (MSI1) promotes stemness during development and cancer. By controlling target mRNA turnover and translation, MSI1 is implicated in the regulation of cancer hallmarks such as cell cycle or Notch signaling. Thereby, the protein enhanced cancer growth and therapy resistance to standard regimes. Due to its specific expression pattern and diverse functions, MSI1 represents an interesting target for cancer therapy in the future. In this review we summarize previous findings on MSI1's implications in developmental processes of other organisms. We revisit MSI1's expression in a set of solid cancers, describe mechanistic details and implications in MSI1 associated cancer hallmark pathways and highlight current research in drug development identifying the first MSI1-directed inhibitors with anti-tumor activity.

Expression of Musashi-1 Increases in Bone Healing

Musashi-1 (MSI1) is an RNA-binding protein that regulates progenitor cells in adult and developing organisms to maintain self-renewal capacities. The role of musashi-1 in the bone healing environment and its relation with other osteogenic factors is unknown. In the current study, we analyze the expression of MSI1 in an experimental model of rat femoral bone fractures. We also analyze the relation between MSI1 expression and the expression of two osteogenic markers: periostin (POSTN) and runt-related transcription factor 2 (RUNX2). We use histological, immunohistochemical, and qPCR techniques to evaluate bone healing and the expression of MSI1, POSTN, and RUNX2 over time (4, 7, and 14 days). We compare our findings with non-fractured controls. We find that in bone calluses, the number of cells expressing MSI1 and RUNX2 increase over time and the intensity of POSTN expression decreases over time. Within bone calluses, we find the presence of MSI1 expression in mesenchymal stromal cells, osteoblasts, and osteocytes but not in hypertrophic chondrocytes. After 14 days, the expression of MSI1, POSTN, and RUNX2 was significantly correlated. Thus, we conclude that musashi-1 potentially serves in the osteogenic differentiation of mesenchymal stromal cells and bone healing. Therefore, further studies are needed to determine the possibility of musashi-1′s role as a clinical biomarker of bone healing and therapeutic agent for bone regeneration.

Increased expression of MUSASHI1 in epithelial breast cancer cells is due to down regulation of miR-125b

Background

Musashi1 (MSI1) is an oncogenic protein with a crucial role in the proliferation and characteristics of the epithelial cells in breast cancer. The change in expression of MSI1 has a role in solid tumor progression. There are different factors that regulate MSI1 expression in various cancer tissues including microRNAs which are considered as one of the most important of these factors. The aim of our study is identification of the molecular cause of maximal expression of MSI1 in epithelial breast cancer cell lines.

Results

Among predicted microRNAs, miR-125b, miR-637 and miR-802 were able to significantly reduce the luciferase activity. In addition, the relative expression of these three miRNAs were measured in the cancerous cell lines that results showed a significant reduction in expression of all microRNAs. On the other hand, only the overexpression of miR-125b caused a change in the expression pattern of MSI1 in breast epithelial cancer cell lines. Accordingly, our results demonstrated that the exogenous expression of miR-125b decreased not only the MSI1 protein but also expression of epithelial markers in breast cancer cells.

Conclusions

The results of luciferase reporter assay showed that MSI1 is a direct target for miR-125b in epithelial breast cancer cells. Moreover, higher amount of MSI1 in those cell lines seems due to the reduced amount of miR-125b, which is responsible for epithelial features of those kinds of cancer cells. Therefore, the modulation of miR-125b may be a potential approach to help to combat against epithelial breast tumors.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12860-021-00348-8.

Transcriptome analysis of genes related to gonad differentiation and development in Muscovy ducks

BACKGROUND

Sex-related genes play a crucial role in gonadal differentiation into testes or ovaries. However, the genetic control of gonadal differentiation in Muscovy ducks remains unknown. Therefore, the objective of our study was to screen new candidate genes associated with ovarian and testicular development.

RESULTS

In this study, 24 males before gonadal differentiation (MB), 24 females before gonadal differentiation (FB), 24 males after gonadal differentiation (MA) and 24 females after gonadal differentiation (FA) were selected from Putian Muscovy ducks, forming 4 groups. RNA-Seq revealed 101.76 Gb of clean reads and 2800 differentially expressed genes (DEGs), including 46 in MB vs FB, 609 in MA vs FA, 1027 in FA vs FB, and 1118 in MA vs MB. A total of 146 signalling pathways were enriched by KEGG analysis, among which 20, 108, 108 and 116 signalling pathways were obtained in MB vs FB, MA vs MB, MA vs FA and FA vs FB, respectively. In further GO and KEGG analyses, a total of 21 candidate genes related to gonad differentiation and development in Muscovy ducks were screened. Among these, 9 genes were involved in the differentiation and development of the testes, and 12 genes were involved in the differentiation and development of the ovaries. In addition, RNA-Seq data revealed 2744 novel genes.

CONCLUSIONS

RNA-Seq data revealed 21 genes related to gonadal differentiation and development in Muscovy ducks. We further identified 12 genes, namely, WNT5B, HTRA3, RSPO3, BMP3, HNRNPK, NIPBL, CREB3L4, DKK3, UBE2R2, UBPL3KCMF1, ANXA2, and OSR1, involved in the differentiation and development of ovaries. Moreover, 9 genes, namely, TTN, ATP5A1, DMRT1, DMRT3, AMH, MAP3K1, PIK3R1, AGT and ADAMTSL1, were related to the differentiation and development of testes. Moreover, after gonadal differentiation, DMRT3, AMH, PIK3R1, ADAMTSL1, AGT and TTN were specifically highly expressed in males. WNT5B, ANXA2 and OSR1 were specifically highly expressed in females. These results provide valuable information for studies on the sex control of Muscovy ducks and reveal novel candidate genes for the differentiation and development of testes and ovaries.

Intracellular functions of RNA-binding protein, Musashi1, in stem and cancer cells

RNA-binding protein, musashi1 (MSI1), is a main protein in asymmetric cell division of the sensory organ precursor cells, whereas its expression is reported to be upregulated in cancers. This protein is a critical element in proliferation of stem and cancer stem cells, which acts through Wnt and Notch signaling pathways. Moreover, MSI1 modulates malignancy and chemoresistance of lung cancer cells via activating the Akt signaling. Due to the main role of MSI1 in metastasis and cancer development, MSI1 would be an appropriate candidate for cancer therapy. Downregulation of MSI1 inhibits proliferation of cancer stem cells and reduces the growth of solid tumors in several cancers. On the other hand, MSI1 expression is regulated by microRNAs in such a way that several different tumor suppressor miRNAs negatively regulate oncogenic MSI1 and inhibit migration and tumor metastasis. The aim of this review is summarizing the role of MSI1 in stem cell proliferation and cancer promotion.

RNA-Binding Proteins in Acute Leukemias

Acute leukemias are genetic diseases caused by translocations or mutations, which dysregulate hematopoiesis towards malignant transformation. However, the molecular mode of action is highly versatile and ranges from direct transcriptional to post-transcriptional control, which includes RNA-binding proteins (RBPs) as crucial regulators of cell fate. RBPs coordinate RNA dynamics, including subcellular localization, translational efficiency and metabolism, by binding to their target messenger RNAs (mRNAs), thereby controlling the expression of the encoded proteins. In view of the growing interest in these regulators, this review summarizes recent research regarding the most influential RBPs relevant in acute leukemias in particular. The reported RBPs, either dysregulated or as components of fusion proteins, are described with respect to their functional domains, the pathways they affect, and clinical aspects associated with their dysregulation or altered functions.

Fine-mapping of 150 breast cancer risk regions identifies 191 likely target genes

Genome-wide association studies have identified breast cancer risk variants in over 150 genomic regions, but the mechanisms underlying risk remain largely unknown. These regions were explored by combining association analysis with in silico genomic feature annotations. We defined 205 independent risk-associated signals with the set of credible causal variants in each one. In parallel, we used a Bayesian approach (PAINTOR) that combines genetic association, linkage disequilibrium and enriched genomic features to determine variants with high posterior probabilities of being causal. Potentially causal variants were significantly over-represented in active gene regulatory regions and transcription factor binding sites. We applied our INQUSIT pipeline for prioritizing genes as targets of those potentially causal variants, using gene expression (expression quantitative trait loci), chromatin interaction and functional annotations. Known cancer drivers, transcription factors and genes in the developmental, apoptosis, immune system and DNA integrity checkpoint gene ontology pathways were over-represented among the highest-confidence target genes.

PLF-1 (Proliferin-1) Modulates Smooth Muscle Cell Proliferation and Development of Experimental Intimal Hyperplasia

Background Although apoptosis and cell proliferation have been extensively investigated in atherosclerosis and restenosis postinjury, the communication between these 2 cellular events has not been evaluated. Here, we report an inextricable communicative link between apoptosis and smooth muscle cell proliferation in the promotion of vascular remodeling postinjury. Methods and Results Cathepsin K-mediated caspase-8 maturation is a key initial step for oxidative stress-induced smooth muscle cell apoptosis. Apoptotic cells generate a potential growth-stimulating signal to facilitate cellular mass changes in response to injury. One downstream mediator that cathepsin K regulates is PLF-1 (proliferin-1), which can potently stimulate growth of surviving neighboring smooth muscle cells through activation of PI3K/Akt/p38MAPK (phosphatidylinositol 3-kinase/protein kinase B/p38 mitogen-activated protein kinase)-dependent and -independent mTOR (mammalian target of rapamycin) signaling cascades. We observed that cathepsin K deficiency substantially mitigated neointimal hyperplasia by reduction of Toll-like receptor-2/caspase-8-mediated PLF-1 expression. Interestingly, PLF-1 blocking, with its neutralizing antibody, suppressed neointima formation and remodeling in response to injury in wild-type mice. Contrarily, administration of recombinant mouse PLF-1 accelerated injury-induced vascular actions. Conclusions This is the first study detailing PLF-1 as a communicator between apoptosis and proliferation during injury-related vascular remodeling and neointimal hyperplasia. These data suggested that apoptosis-driven expression of PLF-1 is thus a novel target for treatment of apoptosis-based hyperproliferative disorders.

Genetic and molecular bases of esophageal Cancer among Iranians: an update

Abstract

Background

Esophageal cancer is one of the leading causes of cancer related deaths among the Iranians. There is still a high ratio of mortality and low 5 years survival which are related to the late onset and diagnosis. Majority of patients refer for the treatment in advanced stages of tumor progression.

Main body

It is required to define an efficient local panel of diagnostic and prognostic markers for the Iranians. Indeed such efficient specific panel of markers will pave the way to decrease the mortality rate and increase the 5 years survival among the Iranian patients via the early diagnosis and targeted therapy.

Conclusion

in present review we have reported all of the molecular markers in different signaling pathways and cellular processes which have been assessed among the Iranian esophageal cancer patients until now.

Inhibition of RNA-Binding Protein Musashi-1 Suppresses Malignant Properties and Reverses Paclitaxel Resistance in Ovarian Carcinoma

Background and Aims: Ovarian carcinoma (OC) is one of the most lethal malignant tumors with a high reoccurrence and chemoresistance. The key mechanism relationship with chemoresistance in ovarian carcinoma is still unclear. The existence of cancer stem cells involves in chemoresistance and reoccurrence in OC. The objective of this study was to investigate the expression, suppression of malignant properties and reversal of paclitaxel resistance inhibiting RNA-binding protein Musashi-1 with siRNA in ovarian cancer cells.

Methods: The expression of MSI-1 was analyzed in 39 normal ovarian epithelia tissues, 92 serous cystadenomas, 68 borderline serous cystadenomas, and 97 serous cystadenocarcinomas by immunohistochemistry. pLKO.1-MSI-1-siRNA expression vector was transfected into ovarian carcinoma cell line A2780 and its paclitaxel-resistant cell subline A2780/Taxol. The roles of MSI-1 in proliferation, apoptosis, migration and invasion were explored by cell proliferation analysis, Caspase 3 activity assay, wound healing assay, migration and matrigel invasion assay, respectively. Western Blotting and Real-time quantitative PCR were conducted to detect the expression of MSI-1 and the ERK signaling pathway. Reversal of paclitaxel resistance assay was used to evaluate the role of MSI-1 in paclitaxel resistance of OC cells. Finally, therapeutic effects of MSI-1 inhibition were investigated the xenogratfs of SCID mice in vivo of the paclitacel-resistant.

Results: MSI-1 is overexpressed and associated with an unfavorable prognosis in OC patients. Knockdown of MSI-1 by small interfering RNA (siRNA) inhibits proliferation, promotes apoptosis, and reduces migration and invasion of cancer cells. Moreover, MSI-1 expression inhibition reverses paclitaxel-resistance in OC cells. We further display that MSI-1 effectively protects OC cells from paclitaxel-induced apoptosis by increasing the expression of p-Bcl-2 through ERK signaling pathway activation. In vivo, MSI-1 siRNA clearly showed a strong effect on tumor growth inhibition and paclitaxel-resistance reversal.

Conclusions: These findings suggest that MSI-1 overexpression is associated with the prognosis of OC patients, and knockdown of MSI-1 can suppress malignant properties and reverse paclitaxel-resistance in OC cells. MSI-1 maybe act as a potential prognostic indicator and a therapeutic target in OC.

Musashi1 promotes tumor metastasis and is a prognostic marker for renal carcinoma

BACKGROUND

Musashi1 (MSI1) has been reported to be involved in cancer development and progression. The biologic role of MSI1 in renal cell carcinoma (RCC), however, remains unknown.

METHODS

Expression of MSI1 in normal kidney cells and kidney cancer cells were measured by real-time PCR. In addition, MSI1 expression in 20 paired kidney cancer and non-cancerous tissues were quantified using real-time PCR. Furthermore, the expression of MSI1 in 115 kidney cancer samples was detected to analyze the correlations between MSI1 expression and the clinicopathological features of RCC patients. The biological function of MSI1 on tumor cell invasion and migration were explored through wound healing and transwell migration assays.

RESULTS

MSI1 was significantly upregulated in renal cancer cells and tissues compared with normal kidney cells and tissues. High levels of MSI1 were positively associated with tumor stage (P=0.002) and distant metastasis (P=0.013) of RCC patients. Patients with higher MSI1 expression had a significantly poorer overall and recurrence-free survival time (P=0.019 and P=0.012, respectively) than patients with low MSI1 expression. Multivariate analysis showed that MSI1 overexpression was an independent prognostic indicator (P=0.009 and P=0.015, respectively) for the survival of RCC patients. Ablation of MSI1 inhibited the invasion and metastasis of renal cancer cells.

CONCLUSION

Our results suggest that MSI1 expression is upregulated in RCC, and that MSI1 plays an important role in promoting cell invasion and metastasis of RCC.

Wnt signaling in human and mouse breast cancer: Focusing on Wnt ligands, receptors and antagonists

Wnt proteins, a group of secreted glycoproteins, mainly combine with receptors Frizzled (FZD) and/or low-density-lipoprotein receptor-related proteins 5/6 (LRP5/6), initiating β-catenin-dependent and -independent signaling pathways. These pathways, which can be regulated by some secreted antagonists such as secreted Frizzled-related proteins (SFRP) and dickkopf-related protein (DKK), play a critical role in embryo development and adult homeostasis. Overactivation of Wnt signaling has been implicated in some human diseases including cancer. Wnt transgenic mice provide convincing evidence that Wnt signaling is involved in breast cancer initiation and progression, which is further strengthened by observations on human clinical breast cancer patients and studies on in vitro cultured human breast cancer cells. This review focuses on the roles of Wnt ligands, receptors and antagonists in breast cancer development instead of molecules or signaling transactivating β-catenin independent on Wnt upstream components.

Functional Polymorphism in the MSI1 Gene Promoter Confers a Decreased Risk of Lung Cancer in Chinese by Reducing MSI1 Expression

Background:

Musashi1 (MSI1) is a characteristic stem cell marker that regulates the balance between cell self-renewal and differentiation. Evidence has identified MSI1 as a pivotal oncogenic regulator in diverse malignancies. However, little evidence uncovers the role of genetic variations of MSI1 gene in cancer etiology.

Objective:

The aim of this study was to investigate the association between genetic variants in the MSI1 gene and lung cancer risk.

Methods:

Based on a two-stage retrospective study with a total of 1559 patients with lung cancer and 1667 healthy controls, we evaluated the relevance between three putative functional SNPs in the MSI1 promoter (i.e., -2696T>C[rs7959801], -2297T>C[rs3742038] and -1081C>T[rs34570155]) and lung cancer risk.

Results:

We found that the SNP rs7959801T>C was significantly associated with lung cancer susceptibility. Compared to those with rs7959801TT wild-genotype, individuals with CT/CC variant genotypes exerted consistently beneficial roles in lung cancer risk in the discovery set (adjusted odd ratios [OR] = 0.67; 95% confidence interval [CI] = 0.57-0.80), and in the validation set (OR=0.69; 95%CI=0.54-0.88). Functional assays indicated that the allele transformation from T to C in rs7959801 of MSI1 gene arrestingly decreased its transcription activity in vitro. Furthermore, the expression levels of MSI1 were significantly lower in the patients with CT/CC variants than in those who were with TT genotype.

Conclusion:

Our findings suggested that the rs7959801T>C polymorphism in the MSI1 promoter conferred a decreased risk to lung cancer by reducing the expression of MSI1 and it may be a promising indicator for lung cancer predisposition.

Mammary gland stem cells and their application in breast cancer

The mammary gland is an organ comprising two primary lineages, specifically the inner luminal and the outer myoepithelial cell layers. Mammary gland stem cells (MaSCs) are highly dynamic and self-renewing, and can give rise to these mammary gland lineages. The lineages are responsible for gland generation during puberty as well as expansion during pregnancy. In recent years, researchers have focused on understanding how MaSCs are regulated during mammary gland development and transformation of breast cancer. Here, we summarize the identification of MaSCs, and how they are regulated by the signaling transduction pathways, mammary gland microenvironment, and non-coding RNAs (ncRNAs). Moreover, we debate the evidence for their serving as the origin of breast cancer, and discuss the therapeutic perspectives of targeting breast cancer stem cells (BCSCs). In conclusion, a better understanding of the key regulators of MaSCs is crucial for the clinical treatment of breast cancer.

Anticancer effect of quinacrine on diffuse large B‑cell lymphoma via inhibition of MSI2‑NUMB signaling pathway

Diffuse large B‑cell lymphoma (DLBCL) is the most common subtype of non‑Hodgkin's lymphoma. Despite improvements in the clinical outcomes of DLBCL, ~30% of patients will develop relapse/refractory disease. Therefore, novel therapeutic drugs have been investigated to improve disease outcomes. Previous studies have revealed the anticancer effects of quinacrine (QC) on tumor cells in vitro, although its role in human DLBCL is yet to be identified. The present study sought to examine the cytotoxic effect of QC on DLBCL cells. QC induced G0/G1 cell cycle arrest and apoptosis in the DLBCL cell lines SU‑DHL‑8 and OCI‑LY01, in a dose‑dependent manner, in addition to the downregulation of cyclin‑dependent kinase 4/6 and the upregulation of cleaved poly‑ADP ribose polymerase 1. Upon exposure to QC, RNA‑binding protein Musashi homolog 2 inactivation and activation of protein numb homolog were observed. In addition, QC was able to inhibit the expression of Myc proto‑oncogene protein. The results of the present study indicated that QC may be a potential anti‑DLBCL drug.

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.

Musashi-1 is the candidate of the regulator of hair cell progenitors during inner ear regeneration

BACKGROUND

Hair cell loss in the cochlea is caused by ototoxic drugs, aging, and environmental stresses and could potentially lead to devastating pathophysiological effects. In adult mammals, hair cell loss is irreversible and may result in hearing and balance deficits. In contrast, nonmammalian vertebrates, including birds, can regenerate hair cells through differentiation of supporting cells and restore inner ear function, suggesting that hair cell progenitors are present in the population of supporting cells.

RESULTS

In the present study, we aimed to identify novel genes related to regeneration in the chicken utricle by gene expression profiling of supporting cell and hair cell populations obtained by laser capture microdissection. The volcano plot identified 408 differentially expressed genes (twofold change, p = 0.05, Benjamini-Hochberg multiple testing correction), 175 of which were well annotated. Among these genes, we focused on Musashi-1 (MSI1), a marker of neural stem cells involved in Notch signaling, and the downstream genes in the Notch pathway. Higher expression of these genes in supporting cells compared with that in hair cells was confirmed by quantitative reverse transcription polymerase chain reaction. Immunohistochemistry analysis demonstrated that MSI1 was mainly localized at the basal side of the supporting cell layer in normal chick utricles. During the regeneration period following aminoglycoside antibiotic-induced damage of chicken utricles, the expression levels of MSI1, hairy and enhancer of split-5, and cyclin D1 were increased, and BrdU labeling indicated that cell proliferation was enhanced.

CONCLUSIONS

The findings of this study suggested that MSI1 played an important role in the proliferation of supporting cells in the inner ear during normal and damaged conditions and could be a potential therapeutic target in the treatment of vestibular defects.

The AKT inhibitor triciribine in combination with paclitaxel has order-specific efficacy against Zfp217-induced breast cancer chemoresistance

We previously identified the transcription factor ZNF217 (human) / Zfp217 (mouse) as an oncogene and prognostic indicator of reduced survival, increased metastasis, and reduced response to therapy in breast cancer patients. Here we investigated the role of Zfp217 in chemotherapy resistance. Preclinical animal models of Zfp217 overexpression were treated with a combination therapy of the microtubule inhibitor epothilone B, doxorubicin (Adriamycin), and cyclophosphamide (EAC). Tumors overexpressing Zfp217 increased their tumor burden compared to control tumors after treatment and accumulated a mammary gland progenitor cell population (K8⁺K14⁺). To overcome this chemoresistance after ZNF217 overexpression, we treated tumors ± Zfp217 overexpression with paclitaxel and triciribine, a nucleoside analog and AKT inhibitor that kills cells that overexpress ZNF217. Treatment order critically impacted the efficacy of the therapy. Combination treatment of triciribine followed by paclitaxel (TCN→PAC) inhibited tumor burden and increased survival in tumors that overexpressed Zfp217, whereas single agent or combination treatment in the reverse order (PAC→TCN) did not improve response. Analysis of these tumors and patient-derived tumor xenograft tumors treated with the same therapies suggested that Zfp217 overexpression in tumors contributes both to decreased microvessel density and vessel maturity, while TCN→PAC tumors overexpressing Zfp217 showed improved vessel maturity.

DKK3 attenuates the cytotoxic effect of natural killer cells on CD133+ gastric cancer cells

Cancer stem cell (CSCs) has started a new era in cancer research. CD133 is a widely used marker for identification of CSCs. More and more studies showed that NK cells preferentially target cancer stem-like cells. However, the deeper mechanism of the susceptibility of cancer stem cells to NK cells remains unclear. In this study, we isolated CD133 positive population of a gastric cancer cell line, BGC823 cells, and cultured with NK cells. We found that CD133 could efficiently active NK cells in an NKG2D-dependent manner. DKK3 has been demonstrated as a suppressor in many cancers. Interestingly, we found that DKK3 suppressed CD133-induced activation in NK cells by inhibiting Erk pathway and immunological synapse (IS) formation. NK cells-based CSCs immunotherapy may be a novel approach for cancer therapy.

Musashi RNA-Binding Proteins as Cancer Drivers and Novel Therapeutic Targets

Aberrant gene expression that drives human cancer can arise from epigenetic dysregulation. Although much attention has focused on altered activity of transcription factors and chromatin-modulating proteins, proteins that act posttranscriptionally can potently affect expression of oncogenic signaling proteins. The RNA-binding proteins (RBP) Musashi-1 (MSI1) and Musashi-2 (MSI2) are emerging as regulators of multiple critical biological processes relevant to cancer initiation, progression, and drug resistance. Following identification of Musashi as a regulator of progenitor cell identity in Drosophila, the human Musashi proteins were initially linked to control of maintenance of hematopoietic stem cells, then stem cell compartments for additional cell types. More recently, the Musashi proteins were found to be overexpressed and prognostic of outcome in numerous cancer types, including colorectal, lung, and pancreatic cancers; glioblastoma; and several leukemias. MSI1 and MSI2 bind and regulate the mRNA stability and translation of proteins operating in essential oncogenic signaling pathways, including NUMB/Notch, PTEN/mTOR, TGFβ/SMAD3, MYC, cMET, and others. On the basis of these activities, MSI proteins maintain cancer stem cell populations and regulate cancer invasion, metastasis, and development of more aggressive cancer phenotypes, including drug resistance. Although RBPs are viewed as difficult therapeutic targets, initial efforts to develop MSI-specific inhibitors are promising, and RNA interference-based approaches to inhibiting these proteins have had promising outcomes in preclinical studies. In the interim, understanding the function of these translational regulators may yield insight into the relationship between mRNA expression and protein expression in tumors, guiding tumor-profiling analysis. This review provides a current overview of Musashi as a cancer driver and novel therapeutic target. Clin Cancer Res; 23(9); 2143-53. ©2017 AACR.

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 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.

Molecular mechanisms of asymmetric divisions in mammary stem cells

Stem cells have the remarkable ability to undergo proliferative symmetric divisions and self-renewing asymmetric divisions. Balancing of the two modes of division sustains tissue morphogenesis and homeostasis. Asymmetric divisions of Drosophila neuroblasts (NBs) and sensory organ precursor (SOP) cells served as prototypes to learn what we consider now principles of asymmetric mitoses. They also provide initial evidence supporting the notion that aberrant symmetric divisions of stem cells could correlate with malignancy. However, transferring the molecular knowledge of circuits underlying asymmetry from flies to mammals has proven more challenging than expected. Several experimental approaches have been used to define asymmetry in mammalian systems, based on daughter cell fate, unequal partitioning of determinants and niche contacts, or proliferative potential. In this review, we aim to provide a critical evaluation of the assays used to establish the stem cell mode of division, with a particular focus on the mammary gland system. In this context, we will discuss the genetic alterations that impinge on the modality of stem cell division and their role in breast cancer development.

Upregulated MicroRNA-25 Mediates the Migration of Melanoma Cells by Targeting DKK3 through the WNT/β-Catenin Pathway

Previous research indicates that microRNA-25 (miR-25) regulates carcinogenesis and the progression of various cancers, but the role of miR-25 in melanoma remains unclear. We observed that miR-25 was significantly upregulated in melanoma cell lines and tissue samples. Downregulation of miR-25 markedly suppressed invasion and proliferation of melanoma cells in vitro; however, overexpression of miR-25 markedly increased melanoma cell invasion and proliferation. Moreover, we observed Dickkopf-related protein 3 (DKK3) as a direct target of miR-25 in vitro. Upregulation of DKK3 partially attenuated the oncogenic effect of miR-25 on melanoma cells. Ectopic expression of miR-25 in melanoma cells induced β-catenin accumulation in nuclear and inhibited TCF4 (T cell factor 4) activity, as well as the expression of c-Myc and Cyclin D1. In a nude xenograft model, miR-25 upregulation significantly increased A375 melanoma growth. In summary, miR-25 is upregulated in melanoma and promotes melanoma cell proliferation and invasion, partially by targeting DKK3. These results were indicated that miR-25 may serve as a potential target for the treatment of melanoma in the future.

RNA binding proteins in spermatogenesis: an in depth focus on the Musashi family

Controlled gene regulation during gamete development is vital for maintaining reproductive potential. During the complex process of mammalian spermatogenesis, male germ cells experience extended periods of the inactive transcription despite heavy translational requirements for continued growth and differentiation. Hence, spermatogenesis is highly reliant on mechanisms of posttranscriptional regulation of gene expression, facilitated by RNA binding proteins (RBPs), which remain abundantly expressed throughout this process. One such group of proteins is the Musashi family, previously identified as critical regulators of testis germ cell development and meiosis in Drosophila, and also shown to be vital to sperm development and reproductive potential in the mouse. This review describes the role and function of RBPs within the scope of male germ cell development, focusing on our recent knowledge of the Musashi proteins in spermatogenesis. The functional mechanisms utilized by RBPs within the cell are outlined in depth, and the significance of sub-cellular localization and stage-specific expression in relation to the mode and impact of posttranscriptional regulation is also highlighted. We emphasize the historical role of the Musashi family of RBPs in stem cell function and cell fate determination, as originally characterized in Drosophila and Xenopus, and conclude with our current understanding of the differential roles and functions of the mammalian Musashi proteins, Musashi-1 and Musashi-2, with a primary focus on our findings in spermatogenesis. This review highlights both the essential contribution of RBPs to posttranscriptional regulation and the importance of the Musashi family as master regulators of male gamete development.

Dkk3 prevents familial dilated cardiomyopathy development through Wnt pathway

To date, the role of Dickkopf 3 (Dkk3) on the pathogenesis of familial dilated cardiomyopathy (FDCM), and whether and how Dkk3 interferes with Wnt signaling in heart tissues remains unknown. Here, we demonstrate that strong Dkk3 expression was markedly downregulated in adult hearts from WT mice, and Dkk3 expression was upregulated suddenly in hearts from DCM mouse models. Using Dkk3 transgenic and knockout mice, as well as cTnT(R141W) transgenic mice, which manifests progressive chamber dilation and contractile dysfunction and has pathologic phenotypes similar to human DCM patients, we determined that transgenic expression of Dkk3 increased survival rate, improved cardiac morphology breakage and dysfunction, and ameliorated cardiac pathological changes in the cTnT(R141W) mice. In contrast, Dkk3 knockout reduced the survival rate and aggravated the pathological phenotypes of the cTnT(R141W) mice. The protective effects of Dkk3 appeared clearly at 3 months of age, peaked at 6 months of age, and decreased at 10 months of age in the cTnT(R141W) mice. Furthermore, we determined that Dkk3 upregulated Dvl1 (Dishevelled 1) and key proteins of the canonical Wnt pathway (cytoplasmic and nuclear β-catenin, c-Myc, and Axin2) and downregulated key proteins of the noncanonical Wnt pathway (c-Jun N-terminal kinase (JNK), Ca(2+)/calmodulin-dependent protein kinase II (CAMKII), and histone deacetylase 4 (HDAC4)). In contrast, Dkk3 knockout reversed these changes in the cTnT(R141W) mice. In summary, Dkk3 could prevent FDCM development in mice, especially in the compensatory stage, and probably through activation of the canonical and inhibition of the noncanonical Wnt pathway, which suggested that Dkk3 could serve as a therapeutic target for the treatment of cardiomyopathy and heart failure.

Regulation of Stem Cell Self-Renewal and Oncogenesis by RNA-Binding Proteins

Throughout their life span, multicellular organisms rely on stem cell systems. During development pluripotent embryonic stem cells give rise to all cell types that make up the organism. After birth, tissue stem cells maintain properly functioning tissues and organs under homeostasis as well as promote regeneration after tissue damage or injury. Stem cells are capable of self-renewal, which is the ability to divide indefinitely while retaining the potential of differentiation into multiple cell types. The ability to self-renew, however, is a double-edged sword; the molecular mechanisms of self-renewal can be a target of malignant transformation driving tumor development and progression. Growing lines of evidence have shown that RNA-binding proteins (RBPs) play pivotal roles in the regulation of self-renewal by modulating metabolism of coding and non-coding RNAs both in normal tissues and in cancers. In this review, we discuss our current understanding of tissue stem cell systems and how RBPs regulate stem cell fates as well as how the regulatory functions of RBPs contribute to oncogenesis.

The Msi Family of RNA-Binding Proteins Function Redundantly as Intestinal Oncoproteins

Members of the Msi family of RNA-binding proteins have recently emerged as potent oncoproteins in a range of malignancies. MSI2 is highly expressed in hematopoietic cancers, where it is required for disease maintenance. In contrast to the hematopoietic system, colorectal cancers can express both Msi family members, MSI1 and MSI2. Here, we demonstrate that, in the intestinal epithelium, Msi1 and Msi2 have analogous oncogenic effects. Further, comparison of Msi1/2-induced gene expression programs and transcriptome-wide analyses of Msi1/2-RNA-binding targets reveal significant functional overlap, including induction of the PDK-Akt-mTORC1 axis. Ultimately, we demonstrate that concomitant loss of function of both MSI family members is sufficient to abrogate the growth of human colorectal cancer cells, and Msi gene deletion inhibits tumorigenesis in several mouse models of intestinal cancer. Our findings demonstrate that MSI1 and MSI2 act as functionally redundant oncoproteins required for the ontogeny of intestinal cancers.

Role of Msi1 and PYGO2 in esophageal squamous cell carcinoma depth of invasion

Deregulation of developmental signaling pathways such as Wnt/b-catenin and NOTCH are commonly observed in different cancers. A normal wnt pathway is essential for development and tissue homeostasis to preserve a normal balance between the differentiation and proliferation. PYGO2 is the main transcription factor of wnt pathway, while Msi1 is one of the wnt inhibitors. In this study we assessed the correlation between Msi1 and PYGO2 mRNA expression using Real time polymerase chain reaction in 48 esophageal squamous cell carcinoma (ESCC) patients. Although, there was not any significant correlation between the levels of Msi1 and PYGO2 mRNA expression, we observed a significant correlation between the Msi1 and PYGO2 overexpressed cases and depth of tumor invasion (p = 0.05). In conclusion, despite the role of these markers in tumor depth of invasion there is not any feedback between Msi1 and PYGO2 gene expression in ESCC.

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.

The RNA-binding protein Musashi 1 stabilizes the oncotachykinin 1 mRNA in breast cancer cells to promote cell growth

Substance P and its truncated receptor exert oncogenic effects. The high production of substance P in breast cancer cells (BCCs) is caused by the enhancement of tachykinin (TAC)1 translation by cytosolic factor. In vitro translational studies and mRNA stabilization analyses indicate that BCCs contain the factor needed to increase TAC1 translation and to stabilize the mRNA. Prediction of protein folding, RNA-shift analysis, and proteomic analysis identified a 40 kDa molecule that interacts with the noncoding exon 7. Western blot analysis and RNA supershift identified Musashi 1 (Msi1) as the binding protein. Ectopic expression of TAC1 in nontumorigenic breast cells (BCs) indicates that TAC1 regulates its stability by increasing Msi1. Using a reporter gene system, we showed that Msi1 competes with microRNA (miR)130a and -206 for the 3' UTR of exon 7/TAC1. In the absence of Msi1 and miR130a and -206, reporter gene activity decreased, indicating that Msi1 expression limits TAC1 expression. Tumor growth was significantly decreased when nude BALB/c mice were injected with Msi1-knockdown BCCs. In summary, the RNA-binding protein Msi1 competes with miR130a and -206 for interaction with TAC1 mRNA, to stabilize and increase its translation. Consequently, these interactions increase tumor growth.

Animal Models of Gastrointestinal and Liver Diseases. The difficulty of animal modeling of pancreatic cancer for preclinical evaluation of therapeutics

Pancreatic ductal adenocarcinoma (PDAC) is relatively rare but extremely lethal. Standard cytotoxic therapeutics provide little benefit. To date, newer targeted therapeutics have also not been highly successful. Often novel therapeutics that have appeared to perform well in preclinical models have failed in the clinic. Many factors contribute to these failures, but the one most often attributed is the shortcomings of the preclinical models. A plethora of animal models now exist for PDAC, including cell line xenografts, patient-derived xenografts, a wide variety of genetic mouse models, and syngeneic xenografts. These models have generated a tremendous amount of information useful for the understanding of PDAC. Yet none seems to well predict clinical outcomes of new treatments. This review will discuss how genetic instability and cellular heterogeneity make this disease so difficult to model accurately. We will also discuss the strengths and weaknesses of many of the popular models. Ultimately we will argue that there is no perfect model and that the best approach to understanding clinical performance is the use of multiple preclinical models with an understanding of their salient features.

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.

Dickkopf-3 (DKK-3) obstructs VEGFR-2/Akt/mTOR signaling cascade by interacting of β2-microglobulin (β2M) in ovarian tumorigenesis

In this study, we investigated a possible mechanism of β2-microglobulin (β2M) function in cancer metastases in vitro, using a human ovarian carcinoma cell line. β2M, a modulator acts as a cell growth-promoting and cellular signaling factors, was identified as a dickkopf-3 (DKK-3) interacting protein. We also observed that DKK-3 suppresses endothelial cell angiogenesis of β2M through vascular endothelial growth factor receptor-2 (VEGFR-2) in tumorigenesis. Luciferase activity was remarkably reduced by the transfection of DKK-3 in a dose-dependent manner. In addition, over-expression of β2M activates cell growth by suppressing DKK-3-induced apoptosis. The effect of β2M on cell cycle and apoptosis-regulatory components was also confirmed through the silencing of β2M expression. Furthermore, induction of β2M-mediated VEGFR-2/Akt/mTOR phosphorylation and tumor angiogenesis was significantly suppressed by over-expression of DKK-3. Taken together, our results suggest an underlying mechanism for an increase of β2M-related activity in ovarian tumor cells.

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.