Linkage between Twist1 and Bmi1: molecular mechanism of cancer metastasis/stemness and clinical implications

Polycomb Repressor Complex 1 (PRC1) in ovarian cancer: a scoping literature review

High grade serous carcinoma (HGSC) is the most common and the deadliest histologic subtype of epithelial ovarian cancer. HGSC is a therapeutic challenge, as it recurs in 80% of patients diagnosed, often as chemoresistant disease. The mechanism of this chemoresistance is not fully elucidated, but it is partly attributed to the ability of HGSC to maintain a stem-like phenotype that enables development of resistance to current therapies. Polycomb Repressor Complexes 1 and 2 (PRC1/2) have been implicated in the maintenance of the stem cell compartment through silencing tumor suppressor genes and regulating stem cells. These complexes are comprised of multiple polycomb group (PcG) proteins that play a role in normal development, and when deregulated contribute to the development of cancer [2]. Proteins included in PRC1 include B lymphoma mouse Moloney leukemia virus insertion region (BMI1), RING1, and chromobox (CBX) proteins. We aimed to review each of the protein components of PRC1 and their mechanistic relationships to promoting chemoresistant recurrences and propagation of ovarian cancer. Where possible, we reviewed therapeutic investigations of these proteins. We utilized a scoping literature review through Covidence to identify 42 articles meeting criteria for inclusion. The authors identified four relevant articles and the Yale MeSH Analysis Grid Generator was used to establish additional keywords and heading terms. A medical librarian used these terms and articles to draft an initial search strategy within each of the following databases: MEDLINE, Embase, Cochrane Library, and Web of Science Core Collection, yielding 439 articles based on title and abstract. Abstracts were independently reviewed by the authors, identifying 77 articles for full text review, of which 35 were ultimately excluded, leaving 42 articles for full review. Our review identified the currently known mechanisms of the subunits of PRC1 that contribute to HGSC development, recurrence, and chemoresistance. By compiling a comprehensive review of available scientific knowledge, we support and direct further investigation into PRC1 that can affect meaningful advances in the treatment of HGSC.

Regulation of gene transcription of B lymphoma Mo-MLV insertion region 1 homolog (Review)

B lymphoma Mo-MLV insertion region 1 homolog (Bmi-1) is a core protein component of the polycomb repressive complex 1 that inhibits cell senescence and maintains the self-renewal ability of stem cells via downregulation of p16Ink4a and p19Arf expression. Bmi-1 serves an important role in hematopoietic stem cell maintenance and neurodevelopment during embryonic development, and it has been shown to enhance tumorigenesis by promoting cancer stem cell self-renewal and epithelial to mesenchymal transition. Emerging evidence suggests that Bmi-1 overexpression is closely related to the development and progression of various types of cancer, and that downregulation of Bmi-1 expression can inhibit the proliferation, invasion and metastasis of cancer cells. It is therefore important to elucidate the mechanisms underlying the regulation of Bmi-1 expression both under normal growth conditions and in malignant tissues. In the present review, the current body of knowledge pertaining to the transcriptional and post-transcriptional regulation of the BMI-1 gene is discussed, and the potential mechanisms by which Bmi-1 is dysregulated in various types of cancer are highlighted. Bmi-1 expression is primarily controlled via transcriptional regulation, and is regulated by the transcription https://www.ushuaia.pl/hyphen/?ln=en factors of the Myc family, including Myb, Twist1, SALL4 and E2F-1. Post-transcriptionally, regulation of Bmi-1 expression is inhibited by several microRNAs and certain small-molecule drugs. Thus, regulatory transcriptional factors are potential therapeutic targets to reduce Bmi-1 expression in cancer cells. Thus, the present review provides an up-to-date review on the regulation of BMI-1 gene expression at the transcriptional and post-transcriptional level.

Linkage between EMT and stemness state through molecular association between TWIST1 and NY-ESO1 in esophageal squamous cell carcinoma

Aberrant expression of cancer testis antigens (CTAs) is reported in tumors, especially those with stemness properties. A number of CTAs can induce epithelial mesenchymal transition (EMT) process and promote cancer stem cells (CSCs) characteristics. We aimed in this study to analyze the correlation between NY-ESO1 and TWIST1 in esophageal squamous cell carcinoma (ESCC), as well as their impact on EMT process. Gene expression profiling of NY-ESO1 and TWIST1 was performed in 43 esophageal tumors compared to their margin normal tissues of using qRT-PCR, and their correlation with clinicopathological variables of the patients was evaluated. In silico analysis of the NY-ESO1, epithelial and mesenchymal cell markers and also their promoter sequences was executed. ESCC cell lines KYSE-30 and YM-1 were transduced to ectopically express TWIST1 using a retroviral system, followed by qRT-PCR mRNA expression analysis to reveal the probable correlation among TWIST1, NY-ESO1 and EMT markers gene expression. Scratch assay was performed to estimate migration of TWIST1-induced cells. Overexpression of TWIST1 and NY-ESO1 mRNA was observed in 42% and 39.5% (P ˂ 0.05) of tumors, respectively. Expression of the genes was significantly correlated with each other (p = 0.005). TWIST1 and NY-ESO1 overexpression was significantly associated with stage of progression and size of tumors, respectively. A direct association between TWIST1 and NY-ESO1 mRNA expression was confirmed by induced ectopic expression of TWIST1 in ESCC cell lines KYSE-30 and YM-1. TWIST1-induced cells led to increase migration in ESCC cell line. Furthermore, significant up-regulation of EMT markers was observed following ectopic expression of TWIST1 in these cells. Based on our findings, it may be proposed that a vital association is exist between the EMT and the acquisition of cancer stemness state in tumor cells through the TWIST1/NY-ESO1 axis and it can be a critical hallmark in ESCC tumorigenesis.

Signalling mechanism(s) of epithelial-mesenchymal transition and cancer stem cells in tumour therapeutic resistance

Epithelial-mesenchymal transition (EMT) leads to tumour progression, including tumour metastasis, disease recurrence and therapy resistance. Cancer stem cells (CSCs) are a small group of cells that have the ability to undergo self-renewal and heterogeneous differentiation, which play a key role in the occurrence and development of cancer. EMT can promote tumour cells to develop stem cell characteristics, which makes tumours more difficult to treat. Therefore, exploring the role of EMT and CSCs in the metastasis of cancer is of great significance to guide tumour treatment and prognosis. In this review, we discuss EMT and CSCs in cancer progression and therapeutic resistance, with a special focus on the common characteristics and relationships between these processes, to explore the crucial relationships in the development of improved anti-tumour therapies.

AREAS COVERED

In this brief review article, the author has searched PubMed and Wikipedia for original research and reviewed articles to gather current information on the association of CSCs and EMT with therapeutic resistance characteristics, cancer growth and metastasis, which are believed to be regulated by the TGF-β, Wnt, Hedgehog (Hh), β-catenin, STAT3, Notch, and Nanog signalling pathways and other factors (miRNAs, microenvironment and additional cytokines).

Cancer stem cells and epithelial-mesenchymal transition in urothelial carcinoma: Possible pathways and potential therapeutic approaches

There is growing evidence of the presence of cancer stem cells in urothelial carcinoma. Cancer stem cells have the ability to self-renew and to differentiate into all cell types of the original heterogeneous tumor. A panel of diverse cancer stem cell markers might be suitable for simulation studies of urothelial cancer stem cells and for the development of optimized treatment protocols. The present review focuses on the advances in recognizing the markers of urothelial cancer stem cells and possible therapeutic targets. The commonly reported markers and pathways that were evaluated include CD44, CD133, ALDH1, SOX2 & SOX4, BMI1, EZH1, PD-L1, MAGE-A3, COX2/PGE2/STAT3, AR, and autophagy. Studies on the epithelial-mesenchymal transition-related pathways (Shh, Wnt/β-catenin, Notch, PI3K/Akt, TGF-β, miRNA) are also reviewed. Most of these markers were recognized through the expression patterns of cancer stem cell-rich side populations. Their regulative role in the development and differentiation of urothelial cancer stem cells was confirmed in vitro by functional analyses (e.g. cell migration, colony formation, sphere formation), and in vivo in xenograft experiments. Although a small number of these pathways are targeted by currently available drugs or drugs that are the currently being tested in clinical trials, a clear treatment approach has not been developed for most pathways. A greater understanding of the mechanisms that control the proliferation and differentiation of cancer stem cells is expected to lead to improvements in targeted therapy.

Revisiting epithelial-mesenchymal transition in cancer metastasis: the connection between epithelial plasticity and stemness

Epithelial‐mesenchymal transition (EMT) is an important process in embryonic development, fibrosis, and cancer metastasis. During cancer progression, the activation of EMT permits cancer cells to acquire migratory, invasive, and stem‐like properties. A growing body of evidence supports the critical link between EMT and cancer stemness. However, contradictory results have indicated that the inhibition of EMT also promotes cancer stemness, and that mesenchymal‐epithelial transition, the reverse process of EMT, is associated with the tumor‐initiating ability required for metastatic colonization. The concept of ‘intermediate‐state EMT’ provides a possible explanation for this conflicting evidence. In addition, recent studies have indicated that the appearance of ‘hybrid’ epithelial‐mesenchymal cells is favorable for the establishment of metastasis. In summary, dynamic changes or plasticity between the epithelial and the mesenchymal states rather than a fixed phenotype is more likely to occur in tumors in the clinical setting. Further studies aimed at validating and consolidating the concept of intermediate‐state EMT and hybrid tumors are needed for the establishment of a comprehensive profile of cancer metastasis.

Negative regulation of Bmi-1 by AMPK and implication in cancer progression

Bmi-1 is a transcriptional regulator that promotes tumor cell self-renewal and epithelial to mesenchymal transition and its upregulation is associated with tumor progression, AMPK is an intracellular fuel-sensing enzyme and plays important roles in tumor cell growth and progression. Thus, the present study aims to examine the regulation of Bmi-1 by AMPK. First, our data revealed that, as compared to adjacent normal tissue, Bmi-1 was highly expressed in gastric cancer, whereas phosphorylation of AMPK (p-AMPK) was reduced. Similar findings were observed in lung adenocarcinomas and appeared that the expression of Bmi-1 was correlated with pathological grades of the cancer, where opposite changes were found in p-AMPK. Second, Metformin, a pharmacological AMPK activator and anti-diabetic drug, or ectopic expression of LKB1, diminished expression of Bmi-1 in cancer cells, an event that was reversed by silencing LKB1. Third, knockdown of LITAF, previously identified as a downstream target of AMPK, upregulated Bmi-1, associated with increased cell viability, colony formation, and migration of cancer cells in vitro. Fourth, metformin increased the abundance of miR-15a, miR-128, miR-192, and miR-194, which was prevented by knockdown of LITAF. Accordingly, transfection of these individual miRNAs downregulated Bmi-1. Altogether, our data for the first time suggest a regulatory axis in cancer cells: AMPK upregulates LITAF, which in turn increases miRNAs, leading to attenuation of Bmi-1 expression.

LGR5 Is a Gastric Cancer Stem Cell Marker Associated with Stemness and the EMT Signature Genes NANOG, NANOGP8, PRRX1, TWIST1, and BMI1

Background

Accumulating evidence supports the hypothesis that cancer stem cells (CSCs) are essential for cancer initiation, metastasis and drug resistance. However, the functional association of gastric CSC markers with stemness and epithelial-mesenchymal transition (EMT) signature genes is unclear.

Methods

qPCR was performed to measure the expression profiles of stemness and EMT signature genes and their association with putative CSC markers in gastric cancer tissues, cancer cell lines and sphere cells. Western blot analysis was used to confirm the results of the transcript analysis. Cell proliferation, cell migration, drug resistance and sphere cell growth assays were conducted to measure the expansion and invasion abilities of the cells. Tumor xenograft experiments were performed in NOD/SCID mice to test cell stemness in vivo. Flow cytometry and immunofluorescence staining were used to analyze cell subpopulations.

Results

The expression of LGR5 was strikingly up-regulated in sphere cells but not in cancer tissues or parental adherent cells. The up-regulation of LGR5 was also positively associated with stemness regulators (NANOG, OCT4, SOX2, and AICDA) and EMT inducers (PRRX1, TWIST1, and BMI1). In addition, sphere cells exhibited up-regulated vimentin and down-regulated E-cadherin expression. Using gene-specific primers, we found that the NANOG expression primarily originates from the retrogene NANOGP8. Western blot analysis showed that the expression of both LGR5 and NANOG is significantly higher in sphere cells. LGR5 over-expression significantly enhanced sphere cell growth, cell proliferation, cell migration and drug resistance in MGC803 cells. Tumor xenografts in nude mice showed that sphere cells are at least 10 times more efficient at tumor initiation than adherent cells. Flow cytometry analysis showed that ~20% of sphere cells are LGR5+/CD54+, but only ~3% of adherent cells are Lgr5+/CD54+. Immunofluorescence staining supports the above results.

Conclusion

The LGR5-expressing fraction of CD54+ cells represents gastric cancer CSCs, in which LGR5 is closely associated with stemness and EMT core genes, and NANOG expression is mainly contributed by the retrogene NANOGP8. Sphere cells are the best starting materials for the characterization of CSCs.

Differential BMI1, TWIST1, SNAI2 mRNA expression pattern correlation with malignancy type in a spectrum of common cutaneous malignancies: basal cell carcinoma, squamous cell carcinoma, and melanoma

PURPOSE

Melanoma, squamous cell carcinoma (SCC), and basal cell carcinoma (BCC) can be used as a unique model to identify molecular mechanisms to distinguish rarely metastatic (BCC), often metastatic (SCC) and most metastatic (melanoma) cancer. It is known that epithelial-mesenchymal transition and stemness transcription factors (TWIST1, SNAI2/SLUG, and BMI1) play an important role in metastasis and their dysregulation has been demonstrated in metastatic cancers. We hypothesized that this spectrum of cutaneous cancers (BCC, SCC, and melanoma) would be a unique cancer model system to elucidate steps toward cancer invasion and metastasis.

METHODS

We evaluated the mRNA expression level of BMI1, TWIST1, and SNAI2/SLUG and studied clinicopathological features in 170 skin cancers along with normal tissue samples.

RESULTS

We demonstrate downregulation of BMI1 mRNA expression in BCC samples compared with controls (p = 0.0001), SCC (p = 0.001), and melanoma (p = 0.0001) samples. Downregulation of TWIST1 mRNA expression is seen in only BCC samples compared with controls (p = 0.031). High SNAI2 mRNA expression is represented in melanoma samples compared with controls (p = 0.022) and SCC samples (p = 0.031). High mRNA expression of TWIST1 is seen in patients with positive history of cancers. Extremely low mRNA expression of BMI1 is detected in patients with positive history of cancers other than skin cancer.

CONCLUSIONS

These findings provide support for the hypothesis that the spectrum of cutaneous cancers could be better understood as a series of gene dosage-dependent entities with distinct molecular events. Oncogene-induced senescence, mechanism of which is still unclear, could be one explanation for these results.

Cancer stem cells and chemoresistance: The smartest survives the raid

Chemoresistant metastatic relapse of minimal residual disease plays a significant role for poor prognosis of cancer. Growing evidence supports a critical role of cancer stem cell (CSC) behind the mechanisms for this deadly disease. This review briefly introduces the basics of the conventional chemotherapies, updates the CSC theories, highlights the molecular and cellular mechanisms by which CSC smartly designs and utilizes multiple lines of self-defense to avoid being killed by chemotherapy, and concisely summarizes recent progress in studies on CSC-targeted therapies in the end, with the hope to help guide future research toward developing more effective therapeutic strategies to eradicate tumor cells in the patients.

Links between cancer stem cells and epithelial-mesenchymal transition

The epithelial-mesenchymal transition (EMT) has been reported to be an important program that is often activated during the process of cancer invasion and metastasis. Cancer stem cells (CSCs) that can initiate and maintain cancer are also involved in invasion and metastasis of cancer. Recently, insights into the molecular mechanisms and functional features of mesenchymal cells have been greatly colored by findings that some of them have been endowed with the self-renewal trait associated with normal tissue stem cells and CSCs. Among cancer cells experiencing EMT, only some of the most competent CSCs will succeed in planting in another organ. In this paper, we review the molecular mechanism behind the link of EMT and CSCs in cancer progression.

The role of microRNAs in the pathogenesis of endometrial cancer: a systematic review

INTRODUCTION

Epigenetics seem to play a primary role in the current research on the pathogenesis of different types of endometrial cancer. Data so far indicate that microRNAs regulate different pathways that could lead to carcinogenesis when not functioning properly. The aim of this review is to summarize current knowledge on microRNAs that have been associated with endometrial cancer development.

MATERIAL AND METHODS

From July 2014 to August 2014, we conducted a comprehensive research utilizing major online search engines (Pubmed, Crossref, Google Scholar). The main keywords used in our search were endometrial cancer/carcinoma; microRNA; epigenetics; novel biomarkers; pathogenesis.

RESULTS

Overall, we identified 155 studies, although only 77 were eligible for this review. Different miRNAs were identified to contribute either promoting the carcinogenesis in the endometrium or inhibiting different steps of endometrial cancer development. Tumour growth, cell proliferation, apoptosis and invasion metastasis have been identified as the main processes where miRNAs seem to be implicated.

CONCLUSIONS

microRNAs are effective regulators of gene expression that has a significant role in the pathogenesis of endometrial cancer. Research concerning possible therapeutic implications has been promising, although there is still a significant distance to be covered between research observations and clinical results. Extensive preclinical and translational research is still required to improve the efficacy and minimize unwanted effects of miRNAs-based therapy.

Double-negative feedback loop between ZEB2 and miR-145 regulates epithelial-mesenchymal transition and stem cell properties in prostate cancer cells

The invasion and metastasis of tumors are triggered by an epithelial to mesenchymal transition (EMT), which is regulated by microRNAs (miRNAs). EMT also promotes malignant tumor progression and the maintenance of the stem cell property, which endows cancer cells with the capabilities of self-renewal and immortalized proliferation. The transcriptional repressor zinc-finger E-box binding homeobox 2 (ZEB2), as an EMT activator, might be an important promoter of metastasis in some tumors. Here, we report that ZEB2 directly represses the transcription of miR-145, which is a strong repressor of EMT. In turn, ZEB2 is also a direct target of miR-145. Further, our findings show that the downregulation of ZEB2 not only represses invasion, migration, EMT, and the stemness of prostate cancer (PCa) cells, but also suppresses the capability of PC-3 cells to invade bone in vivo. Importantly, the expression level of ZEB2 as revealed by immunohistochemical analysis is positively correlated to bone metastasis, the serum free PSA level, the total PSA level, and the Gleason score in PCa patients and is negatively correlated with miR-145 expression in primary PCa specimens. Thus, our findings demonstrate a double-negative feedback loop between ZEB2 and miR-145 and indicate that the ZEB2/miR-145 double-negative feedback loop plays a significant role in the control of EMT and stem cell properties during the bone metastasis of PCa cells. These results suggest that the double-negative feedback loop between ZEB2 and miR-145 contributes to PCa progression and metastasis and might have therapeutic relevance for the bone metastasis of PCa.

p53, SKP2, and DKK3 as MYCN Target Genes and Their Potential Therapeutic Significance

Neuroblastoma is the most common extra-cranial solid tumor of childhood. Despite significant advances, it currently still remains one of the most difficult childhood cancers to cure, with less than 40% of patients with high-risk disease being long-term survivors. MYCN is a proto-oncogene implicated to be directly involved in neuroblastoma development. Amplification of MYCN is associated with rapid tumor progression and poor prognosis. Novel therapeutic strategies which can improve the survival rates whilst reducing the toxicity in these patients are therefore required. Here we discuss genes regulated by MYCN in neuroblastoma, with particular reference to p53, SKP2, and DKK3 and strategies that may be employed to target them.

The inhibition of KCa3.1 channels activity reduces cell motility in glioblastoma derived cancer stem cells

In the present study we evaluated the expression of the intermediate conductance calcium-activated potassium (KCa3.1) channel in human glioblastoma stem-like cells (CSCs) and investigated its role in cell motility. While the KCa3.1 channel is not expressed in neuronal- and glial-derived tissues of healthy individuals, both the KCa3.1 mRNA and protein are present in the glioblastoma tumor population, and are significantly enhanced in CSCs derived from both established cell line U87MG and a primary cell line, FCN9. Consistent with these data, voltage-independent and TRAM-34 sensitive potassium currents imputable to the KCa3.1 channel were recorded in the murine GL261 cell line and several primary human glioblastoma cells lines. Moreover, a significantly higher KCa3.1 current was recorded in U87MG-CD133 positive cells as compared to the U87MG-CD133 negative subpopulation. Further, we found that the tumor cell motility is strongly associated with KCa3.1 channel expression. Blockade of the KCa3.1 channel with the specific inhibitor TRAM-34 has in fact a greater impact on the motility of CSCs (reduction of 75%), which express a high level of KCa3.1 channel, than on the FCN9 parental population (reduction of 32%), where the KCa3.1 channel is expressed at lower level. Similar results were also observed with the CSCs derived from U87MG. Because invasion of surrounding tissues is one of the main causes of treatment failure in glioblastoma, these findings can be relevant for future development of novel cancer therapeutic drugs.