Dysregulated stemness-related genes in gynecological malignancies

Oct4-Mediated Inhibition of Lsd1 Activity Promotes the Active and Primed State of Pluripotency Enhancers

An aberrant increase in pluripotency gene (PpG) expression due to enhancer reactivation could induce stemness and enhance the tumorigenicity of cancer stem cells. Silencing of PpG enhancers (PpGe) during embryonic stem cell differentiation involves Lsd1-mediated H3K4me1 demethylation and DNA methylation. Here, we observed retention of H3K4me1 and DNA hypomethylation at PpGe associated with a partial repression of PpGs in F9 embryonal carcinoma cells (ECCs) post-differentiation. H3K4me1 demethylation in F9 ECCs could not be rescued by Lsd1 overexpression. Given our observation that H3K4me1 demethylation is accompanied by strong Oct4 repression in P19 ECCs, we tested if Oct4 interaction with Lsd1 affects its catalytic activity. Our data show a dose-dependent inhibition of Lsd1 activity by Oct4 and retention of H3K4me1 at PpGe in Oct4-overexpressing P19 ECCs. These data suggest that Lsd1-Oct4 interaction in cancer stem cells could establish a "primed" enhancer state that is susceptible to reactivation, leading to aberrant PpG expression.

Molecular iodine inhibits the expression of stemness markers on cancer stem-like cells of established cell lines derived from cervical cancer

BACKGROUND

Cancer stem cells (CSC) are characterized by deregulated self-renewal, tumorigenicity, metastatic potential, aberrant stemness signaling pathways, resistance to conventional therapy, and the ability to give rise to a progeny of proliferating cells that constitute the bulk of tumors. Targeting CSC will provide novel treatments for cancer. Different investigations have focused on developing complementary approaches that involve natural compounds that decrease chemo-resistance and reduce the side effects of conventional therapies. Since, it has been reported that molecular iodine (I₂) exhibits antineoplastic effects and decreases tumor progression in some cancer models, we evaluated the potential effect of I₂ on cell cultures enriched in cervical cancer stem-like cells.

METHODS

HeLa and SiHa cervical cancer cells were treated with 200uM I₂ for 24 h. After time, cells were cultured in CSC-conditioned medium (cervospheres) and viability assays were performed. Following, tumorigenic capabilities in cervospheres treated with I₂ were evaluated in NOD/SCID mice. HeLa monolayer cells untreated and their respective cervosphere cells treated or untreated with 200 μM of I₂ for 24 h were xenotransplanted subcutaneously at different amounts and mice were monitored for at least 2 months.

RESULTS

In the present study, monolayer and CSC-enriched cultures (cervospheres) from cervical cancer-derived cell lines, HeLa and SiHa, showed that 200uM I₂ supplementation inhibits proliferation of both and decreased their tumorigenic capacity, in vivo. This antineoplastic effect of I₂ was accompanied by diminished expression of stemness markers including CD49f, CK17, OCT-4, NANOG, SOX2, and KLF4, as well as increased expression and activation of PPARγ receptors.

CONCLUSIONS

All this data led us to suggest a clinical potential use of I₂ for targeting CSC and improve current treatments against cervical cancer.

MAL gene overexpression as a marker of high-grade serous ovarian carcinoma stem-like cells that predicts chemoresistance and poor prognosis

BACKGROUND

The existence of cancer stem cells (CSCs) within a tumor bulk has been demonstrated for many solid tumors including epithelial ovarian carcinoma (EOC). CSCs have been associated to tumor invasion, metastasis and development of chemoresistant recurrences. In this context, we aim to characterize EOC CSCs from the molecular point of view in order to identify potential biomarkers associated with chemoresistance.

METHODS

We isolated a population of cells with stem-like characteristics (OVA-BS4 spheroids) from a primary human EOC cell line under selective conditions. OVA-BS4 spheroids were characterized for drug response by cytotoxicity assays and their molecular profile was investigated by microarray and RT-qPCR. Finally, we performed a gene expression study in a cohort of 74 high-grade serous EOC (HGSOC) patients by RT-qPCR.

RESULTS

Spheroids exhibited properties of self-renewal and a pronounced expression of well-known stem cell genes. Moreover, they demonstrated greater resistance towards several anticancer drugs compared to parent cell line, consistent with their higher ABCG2 gene expression. From microarray studies MAL (T-cell differentiation protein) emerged as the most up-regulated gene in spheroids, compared to parent cell line. In HGSOC patients, MAL was significantly overexpressed in platinum-resistant compared to platinum-sensitive patients and resulted as an independent prognostic marker of survival.

CONCLUSIONS

This investigation provides an important contribution to the identification of molecular markers of ovarian CSCs and chemoresistance. Successful translation of molecular findings would lead to a better comprehension of the mechanisms triggering chemoresistant recurrences, to the individuation of novel therapeutic targets and to the personalization of treatment regimens.

Significance of stem cell marker Nanog gene in the diagnosis and prognosis of lung cancer

The aim of the present study was to analyze the stem cell marker, Nanog gene, for the diagnosis and prognosis of lung cancer cases, and to study its application in the diagnosis of lung cancer. In total, 100 patients diagnosed with lung cancer between April, 2013 and May, 2015 were included in the present study. The patients were randomly divided into group A (lung cancer) and group B (squamous cell lung carcinoma). RT-PCR was used to detect the cancer and adjacent tissues, and Nanog gene expression was detected in groups A and B in cells. The results showed that, analysis of Nanog gene expression in the two groups of patients varied to different degrees. There was no significant difference between the two groups with regard to age, gender, disease stage and lymph node metastasis. Nanog gene expression in patients with carcinoma were significantly higher than that in the adjacent tissues (p<0.05). By contrast, differentiated and well-differentiated carcinoma tissue showed a significantly higher Nanog gene expression than poorly differentiated and undifferentiated carcinoma (p<0.05). The expression of Nanog in normal cells was significantly higher than that in normal lung tissues and benign lesions in lung cancer stem cells. Nanog was highly expressed in CD44⁺ cells, and Nanog expression in lung cancer stem cells was significantly higher (p<0.05). In conclusion, for groups A (lung cancer) and B (squamous cell lung carcinoma) the Nanog gene expression was significantly higher. The data of the present study show that the patients with stage III and IV lung cancer had a higher Nanog gene expression. In addition, there was a higher expression of Nanog in lung cancer patients. By contrast, a lower degree of cell differentiation was associated with strong Nanog gene expression in lung cancer.

An integrated analysis of the SOX2 microRNA response program in human pluripotent and nullipotent stem cell lines

Background

SOX2 is a core component of the transcriptional network responsible for maintaining embryonal carcinoma cells (ECCs) in a pluripotent, undifferentiated state of self-renewal. As such, SOX2 is an oncogenic transcription factor and crucial cancer stem cell (CSC) biomarker in embryonal carcinoma and, as more recently found, in the stem-like cancer cell component of many other malignancies. SOX2 is furthermore a crucial factor in the maintenance of adult stem cell phenotypes and has additional roles in cell fate determination. The SOX2-linked microRNA (miRNA) transcriptome and regulome has not yet been fully defined in human pluripotent cells or CSCs. To improve our understanding of the SOX2-linked miRNA regulatory network as a contribution to the phenotype of these cell types, we used high-throughput differential miRNA and gene expression analysis combined with existing genome-wide SOX2 chromatin immunoprecipitation (ChIP) data to map the SOX2 miRNA transcriptome in two human embryonal carcinoma cell (hECC) lines.

Results

Whole-microRNAome and genome analysis of SOX2-silenced hECCs revealed many miRNAs regulated by SOX2, including several with highly characterised functions in both cancer and embryonic stem cell (ESC) biology. We subsequently performed genome-wide differential expression analysis and applied a Monte Carlo simulation algorithm and target prediction to identify a SOX2-linked miRNA regulome, which was strongly enriched with epithelial-to-mesenchymal transition (EMT) markers. Additionally, several deregulated miRNAs important to EMT processes had SOX2 binding sites in their promoter regions.

Conclusion

In ESC-like CSCs, SOX2 regulates a large miRNA network that regulates and interlinks the expression of crucial genes involved in EMT.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2164-15-711) contains supplementary material, which is available to authorized users.

Sox2 gene amplification significantly impacts overall survival in serous epithelial ovarian cancer

Epithelial ovarian cancer (EOC) is the deadliest gynecologic cancer. Recently, the existence of ovarian cancer stem cells has been reported. Sox2, Nanog and Oct4 are key markers of "stemness". The objective of this study was to determine whether Sox2, Nanog, and Oct4 are associated with EOC and poor outcome. The expression of these markers was assessed by immunofluorescence staining and real-time RT-PCR in human EOC cell lines MDAH-2774 and SKOV-3, while the cancer genome atlas (TCGA) dataset was analyzed for associations with survival. Sox2, Nanog and Oct4 (POU5F1) were all detected by immunofluorescence staining and these results were confirmed by real-time RT-PCR. The TCGA dataset revealed a 26%, 9%, and 6% amplification of Sox2, Nanog and POU5F1, respectively. Additionally, K-M survival analyses showed a significant median overall survival difference (41 versus 48.3 months, P = .01) for Sox2 amplification, but not for Nanog (44.1 versus 36.2 months, P > .05) and POU5F1 (43.5 versus 45.0 months, P > .05). Our results suggest that Sox2 gene amplification significantly influences overall survival.

The hormonal composition of follicular fluid and its implications for ovarian cancer pathogenesis

Ovulation has long been associated with an increased risk in ovarian cancer, yet the underlying molecular mechanisms remain obscure. Two aspects of ovulation have been linked to ovarian cancer pathogenesis. The first is the impact of repetitive tissue injury and repair that occurs with each ovulatory event. The second is the release of follicular fluid that accompanies the follicular rupture and its effect on the ovarian and fallopian tube epithelial cells. Hormones are an important component of follicular fluid, which transiently bathes the ovarian surface and fallopian tube epithelium during ovulation. Much work has been done exploring the role of hormones in fertility, but some, such as estrogen, have also been implicated in the pathogenesis of ovarian and other cancers. Understanding the role of hormones within follicular fluid, as well as how they are altered in disorders which increase ovarian cancer risk, will enhance our ability to assess risk and develop preventative strategies. This review provides an in depth discussion of the logistics of using and studying follicular fluid in ovarian cancer research, and discusses the fluctuations in follicular fluid hormone levels during normal physiological processes versus conditions that increase ovarian cancer risk.

Androgen receptor increases CD133 expression and progenitor-like population that associate with cisplatin resistance in endometrial cancer cell line

Endometrial cancer (EMC) is a sex steroid hormone-related female malignancy. Androgen and androgen receptor (androgen/AR) signals have been implicated in EMC progression. Cancer stem/progenitor cells (CSPCs) are suspected to link to chemoresistance in patients with EMC. In this study, we examined the androgen/AR roles in cisplatin resistance and CSPC population. We found AR expression increased naive EMC side population, CSPC population, cell migration, and epithelial-mesenchymal transition. Meanwhile, it decreased cisplatin cytotoxic effect on EMC cells. Collaterally, endogenous AR expressions in EMC cells were upregulated in the cisplatin-resisting state. Moreover, AR expression could further enhance CD133 expression, CSPC-related markers, and drug-resistance gene messenger RNA expression in EMC cells. Finally, the AR-associated gene expression might go through indirect regulation. This is the first report revealing AR function on EMC cells' CSPC and cisplatin resistance.

Claudin 1 expression characterizes human uterine cervical reserve cells

Stem cells participate in cervical carcinogenesis but their function and exact features are still not clear. One type of stem-like cells are endocervical reserve cells (RCs), and their association with other normal/altered cervical cells is not exactly known. Epithelial cells are attached to each other by tight junctions. Their dominant components are the claudin proteins, which show changed expression in cancer; however, no data are available on their pattern. Expressions of various claudins (1, 2, 3, 4, 7), occludin, cytokeratins 5/6 and 7, and p63 were analyzed in 60 paraffin-embedded cervical samples. Immunohistochemical reactions were evaluated semiquantitatively and statistically. Claudin 1 was as high in RCs as in cervical intraepithelial neoplasia (CIN) and higher than in suprabasal squamous epithelial cells, contrary to the negative glandular and squamous basal cells. Claudin 2 was positive in all cell types except parabasal cells, whereas claudins 4 and 7 were weakly positive and claudin 3 was negative in all cell types. Occludin was positive in RCs, basal/parabasal cells, and CIN, whereas glandular cells were negative. This is a first report that describes the intermediate claudin pattern of RCs, demonstrating that it differs from that of cervical glandular and squamous basal cells, but showing an expression similar to the strong claudin 1 expression detected in cervical neoplastic cells.

Pluripotency transcription factors and cancer stem cells: small genes make a big difference

Cancer stem cells (CSCs) are thought to drive uncontrolled tumor growth, and the existence of CSCs has recently been proven by direct experimental evidence, including tracing cell lineages within a growing tumor. However, CSCs must be analyzed in additional cancer types. Cancer stem cell-like cells (CSCLCs) are a good alternative system for the study of CSCs, which hold great promise for clinical applications. OCT4, NANOG, and SOX2 are three basic transcription factors that are expressed in both CSCLCs and embryonic stem cells (ESCs). These transcription factors play critical roles in maintaining the pluripotence and self-renewal characteristics of CSCLCs and ESCs. In this review, we discuss the aberrant expression, isoforms, and pseudogenes of OCT4, NANOG, and SOX2 in the CSCLC niche, which contribute to the major differences between CSCLCs and ESCs. We also highlight an anticancer therapy that involves killing specific cancer cells directly by repressing the expression of OCT4, NANOG, or SOX2. Importantly, OCT4, NANOG, and SOX2 provide great promise for clinical applications because reducing their expression or blocking the pathways in which they function may inhibit tumor growth and turn-off the cancer “switch.” In the future, a clear understanding of transcription factor regulation will be essential for elucidating the roles of OCT4, NANOG, and SOX2 in tumorigenesis, as well as exploring their use for diagnostic and therapeutic purposes.

Breaking through an epigenetic wall: re-activation of Oct4 by KRAB-containing designer zinc finger transcription factors

The gene Oct4 encodes a transcription factor critical for the maintenance of pluripotency and self-renewal in embryonic stem cells. In addition, improper re-activation of Oct4 contributes to oncogenic processes. Herein, we describe a novel designer zinc finger protein (ZFP) capable of upregulating the endogenous Oct4 promoter in a panel of breast and ovarian cell lines carrying a silenced gene. In some ovarian tumor lines, the ZFP triggered a strong reactivation of Oct4, with levels of expression comparable with exogenous Oct4 cDNA delivery. Surprisingly, the reactivation of Oct4 required a KRAB domain for effective upregulation of the endogenous gene. While KRAB-containing ZFPs are traditionally described as transcriptional repressors, our results suggest that these proteins could, in certain genomic contexts, function as potent activators and, thus, outline an emerging novel function of KRAB-ZFPs. In addition, we document a novel ZFP that could be used for the epigenetic reprograming of cancer cells.