SOX2 promotes tumor growth of esophageal squamous cell carcinoma through the AKT/mammalian target of rapamycin complex 1 signaling pathway

SOXs: Master architects of development and versatile emulators of oncogenesis

Transcription factors regulate a variety of events and maintain cellular homeostasis. Several transcription factors involved in embryonic development, has been shown to be closely associated with carcinogenesis when deregulated. Sry-like high mobility group box (SOX) proteins are potential transcription factors which are evolutionarily conserved. They regulate downstream genes to determine cell fate, via various signaling pathways and cellular processes essential for tissue and organ development. Dysregulation of SOXs has been reported to promote or suppress tumorigenesis by modulating cellular reprogramming, growth, proliferation, angiogenesis, metastasis, apoptosis, immune modulation, lineage plasticity, maintenance of the stem cell pool, therapy resistance and cancer relapse. This review provides a crucial understanding of the molecular mechanism by which SOXs play multifaceted roles in embryonic development and carcinogenesis. It also highlights their potential in advancing therapeutic strategies aimed at targeting SOXs and their downstream effectors in various malignancies.

Significant roles of RNA 5-methylcytosine methylation in cancer

Cancer stands as a leading cause of mortality and poses an escalating threat to global health. Epigenetic dysregulation is pivotal in the onset and advancement of cancer. Recent research on RNA 5-methylcytosine (m5C) methylation has underscored its significant role in cancer. RNA m5C methylation is a key component in gene expression regulation and is intricately linked to cancer development, offering valuable insights for cancer diagnosis, treatment, and prognosis. This review provides an in-depth examination of the three types of regulators associated with RNA m5C methylation and their biological functions. It further investigates the expression and impact of RNA m5C methylation and its regulators in cancer, focusing on their mechanisms in cancer progression and clinical relevance. The current research on inhibitors targeting RNA m5C methylation-related regulators remains underdeveloped, necessitating further exploration and discovery.

Dissecting SOX2 expression and function reveals an association with multiple signaling pathways during embryonic development and in cancer progression

SRY (Sex Determining Region) box 2 (SOX2) is an essential transcription factor that plays crucial roles in activating genes involved in pre- and post-embryonic development, adult tissue homeostasis, and lineage specifications. SOX2 maintains the self-renewal property of stem cells and is involved in the generation of induced pluripotency stem cells. SOX2 protein contains a particular high-mobility group domain that enables SOX2 to achieve the capacity to participate in a broad variety of functions. The information about the involvement of SOX2 with gene regulatory elements, signaling networks, and microRNA is gradually emerging, and the higher expression of SOX2 is functionally relevant to various cancer types. SOX2 facilitates the oncogenic phenotype via cellular proliferation and enhancement of invasive tumor properties. Evidence are accumulating in favor of three dimensional (higher order) folding of chromatin and epigenetic control of the SOX2 gene by chromatin modifications, which implies that the expression level of SOX2 can be modulated by epigenetic regulatory mechanisms, specifically, via DNA methylation and histone H3 modification. In view of this, and to focus further insights into the roles SOX2 plays in physiological functions, involvement of SOX2 during development, precisely, the advances of our knowledge in pre- and post-embryonic development, and interactions of SOX2 in this scenario with various signaling pathways in tumor development and cancer progression, its potential as a therapeutic target against many cancers are summarized and discussed in this article.

Expression of CD44highCD24Low cells, SOX2, and STAT3 transcription factors on peripheral blood and tumor tissue of penile squamous cell carcinoma

BACKGROUND

Penile cancer is high in some underdeveloped countries. Signal transducer and activator of transcription 3 (STAT3) and CD44, CD24, and SOX2+ are known to be markers of diagnosis and prognosis in other cancers, but without studies in penile cancer.

METHODS

A cross-sectional study was conducted at the Hospital de Cancer de Pernambuco from March 2015 to December 2017. We performed SOX2, STAT3, CD24, and CD44 analyses in blood and tumor tissue by flow cytometry.

RESULTS

High levels of CD44highCD24low, CD44highCD24lowpSTAT3+ and CD44hig hCD24low in the blood of patients compared to the controls (p < 0.05). Low of SOX2+ T cells in blood of patients compared to controls. High CD44highCD24low levels in patients with perineural invasion (PNI), tumor size > 3 cm, and pT2 stage (p < 0.05). High T cell levels in the blood and tumor tissue of patients with tumor ≤3 cm (p < 0.05). Increased SOX2+ T cells in blood of patients with PNI (-) and pT1 stage (p < 0.05). CD44highCD24lowpSTAT3+ (r = 0.669; p = 0.024) and SOX2+T cells (r = 0.404, p = 0.029) correlation were observed between blood and tumor tissue in penile cancer patients.

CONCLUSION

CD44, CD24, and SOX2 molecules were markers of advanced disease associated with the worst prognosis in CaPe. However, pSTAT3 and T cells were associated with a more favorable prognosis in this study.

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The modification and recognition of 5-methylcytosine (m5C) are involved in the initiation and progression of various tumor types. However, the precise role and potential mechanism of Y-box-binding protein 1 (YBX1) in esophageal squamous cell carcinoma (ESCC) remains unclear. Here, it is found that YBX1 is frequently upregulated in ESCC compared with matched nontumor tissues. Gain- and loss-of-function assays show that YBX1 promoted the proliferation and metastasis of ESCC cells both in vitro and in vivo. Functional studies revealed that NOP2/Sun RNA methyltransferase family member 2 (NSUN2) is a critical RNA methyltransferase that facilitates YBX1-mediated ESCC progression. Mechanistically, integrated analysis based on RNA immunoprecipitation sequencing (RIP-seq) and m5C methylated RNA immunoprecipitation and sequencing (MeRIP-seq) assays identified spermine oxidase (SMOX) as a target gene containing an m5C site in its coding sequence (CDS) region, which coincided well with the binding site of YBX1. Overexpression of SMOX-WT but not SMOX-Mut partially restored the proliferation and invasion ability of ESCC cells curbed by YBX1 knockdown. Moreover, YBX1 activated the mTORC1 signaling pathway by stabilizing SMOX mRNA. The study reveals that YBX1 promotes ESCC development by stabilizing SMOX mRNA in an m5C-dependent manner, thus providing a valuable therapeutic target for ESCC.

GSK3β-driven SOX2 overexpression is a targetable vulnerability in esophageal squamous cell carcinoma

Esophageal squamous cell carcinoma (ESCC) is one of the deadliest forms of human malignancy that currently lacks approved targeted therapeutics. Accumulating evidence suggests that SOX2 overexpression is a key driving factor for ESCC and various squamous cell carcinoma. Here, through screening a small-molecule kinase inhibitor library, we identified GSK3β as a kinase that is critically required for robust SOX2 expression in ESCC cells. GSK3β did not promote SOX2 transcriptionally but was required for SOX2 protein stability. We demonstrated that GSK3β interacts with and phosphorylates SOX2 at residue S251, which blocks SOX2 from ubiquitination and proteasome-dependent degradation instigated by ubiquitin E3 ligase CUL4ADET1-COP1. Pharmacological inhibition or knockdown of GSK3β by RNA interference selectively impaired SOX2-positive ESCC cell proliferation, cancer stemness, and tumor growth in mouse xenograft model, suggesting that GSK3β promotes ESCC tumorigenesis primarily by driving SOX2 overexpression. GSK3β was found to be frequently overexpressed in clinical esophageal tumors, and there was a positive correlation between GSK3β and SOX2 protein levels. Notably, we found that SOX2 enhanced GSK3β expression transcriptionally, suggesting the existence of a vicious cycle that drives a coordinated GSK3β and SOX2 overexpression in ESCC cells. Finally, we demonstrated in tumor xenograft model that GSK3β inhibitor AR-A014418 was effective in suppressing SOX2-positive ESCC tumor progression and inhibited tumor progression cooperatively with chemotherapeutic agent carboplatin. In conclusion, we uncovered a novel role for GSK3β in driving SOX2 overexpression and tumorigenesis and provided evidence that targeting GSK3β may hold promise for the treatment of recalcitrant ESCCs.

Control of SOX2 protein stability and tumorigenic activity by E3 ligase CHIP in esophageal cancer cells

SOX2 is highly expressed and controls tumor initiation and cancer stem cell function in various squamous cell carcinomas including esophageal squamous cancer. However, the molecular mechanism leading to SOX2 overexpression in cancer is incompletely understood. Here, we identified CHIP, a chaperone-associated ubiquitin E3 ligase, as a novel negative regulator of SOX2 protein stability and tumorigenic activity in esophageal squamous carcinoma cells. We showed that CHIP interacted with SOX2 primarily via chaperone HSP70, together they catalyzed SOX2 ubiquitination and degradation via proteasome. In contrast, HSP90 promoted SOX2 stability and inhibition of HSP90 activity induced SOX2 ubiquitination and degradation. Notably, unlike the case in normal esophageal tissues where CHIP was detected in both the cytoplasm and nucleus, CHIP in clinical esophageal tumor specimens was predominantly localized in the cytoplasm. Consistent with this observation, we observed increased expression of exportin-1/CRM-1 in clinical esophageal tumor specimens. We further demonstrated that CHIP catalyzed SOX2 ubiquitination and degradation primarily in the nuclear compartment. Taken together, our study has identified CHIP as a key suppressor of SOX2 protein stability and tumorigenic activity and revealed CHIP nuclear exclusion as a potential mechanism for aberrant SOX2 overexpression in esophageal cancer. Our study also suggests HSP90 inhibitors as potential therapeutic agents for SOX2-positive cancers.

The roles of the SOX2 protein in the development of esophagus and esophageal squamous cell carcinoma, and pharmacological target for therapy

SOX2 is a transcription factor belonging to the SOX gene family, whose activity has been associated with the maintenance of the stemness and self-renewal of embryonic stem cells (ESCs), as well as the induction of differentiated cells into induced pluripotent stem cells (iPSCs). Moreover, accumulating studies have shown that SOX2 is amplified in various cancers, notably in esophageal squamous cell carcinoma (ESCC). In addition, SOX2 expression is linked to multiple malignant processes, including proliferation, migration, invasion, and drug resistance. Taken together, targeting SOX2 might shed light on novel approaches for cancer therapy. In this review, we aim to summarize the current knowledge regarding SOX2 in the development of esophagus and ESCC. We also highlight several therapeutic strategies for targeting SOX2 in different cancer types, which can provide new tools to treat cancers possessing abnormal levels of SOX2 protein.

SOX2-associated signaling pathways regulate biological phenotypes of cancers

SOX2 is a transcription factor involved in multiple stages of embryonic development. In related reports, SOX2 was found to be abnormally expressed in tumor tissues and correlated with clinical features such as TNM staging, tumor grade, and prognosis in patients with various cancer types. In most cancer types, SOX2 is a tumor-promoting factor that regulates tumor progression and metastasis primarily by maintaining the stemness of cancer cells. In addition, SOX2 also regulates the proliferation, apoptosis, invasion, migration, ferroptosis and drug resistance of cancer cells. However, SOX2 acts as a tumor suppressor in some cases in certain cancer types, such as gastric and lung cancer. These key regulatory functions of SOX2 involve complex regulatory networks, including protein-protein and protein-nucleic acid interactions through signaling pathways and noncoding RNA interactions, modulating SOX2 expression may be a potential therapeutic strategy for clinical cancer patients. Therefore, we sorted out the phenotypes related to SOX2 in cancer, hoping to provide a basis for further clinical translation.

Roles of oncogenes in esophageal squamous cell carcinoma and their therapeutic potentials

Esophageal squamous cell carcinoma (ESCC) is the most common type of esophageal cancer (EC) in Asia. It is a malignant digestive tract tumor with abundant gene mutations. Due to the lack of specific diagnostic markers and early cancer screening markers, most patients are diagnosed at an advanced stage. Genetic and epigenetic changes are closely related to the occurrence and development of ESCC. Here, We review the activation of proto-oncogenes into oncogenes through gene mutation and gene amplification in ESCC from a genetic and epigenetic genome perspective, We also discuss the specific regulatory mechanisms through which these oncogenes mainly affect the biological function and occurrence and development of ESCC through specific regulatory mechanisms. In addition, we summarize the clinical application value of these oncogenes is summarized, and it provides a feasible direction for clinical use as potential therapeutic and diagnostic markers.

Potent molecular-targeted therapies for advanced esophageal squamous cell carcinoma

Esophageal cancer (EC) remains a public health concern with a high mortality and disease burden worldwide. Esophageal squamous cell carcinoma (ESCC) is a predominant histological subtype of EC that has unique etiology, molecular profiles, and clinicopathological features. Although systemic chemotherapy, including cytotoxic agents and immune checkpoint inhibitors, is the main therapeutic option for recurrent or metastatic ESCC patients, the clinical benefits are limited with poor prognosis. Personalized molecular-targeted therapies have been hampered due to the lack of robust treatment efficacy in clinical trials. Therefore, there is an urgent need to develop effective therapeutic strategies. In this review, we summarize the molecular profiles of ESCC based on the findings of pivotal comprehensive molecular analyses, highlighting potent therapeutic targets for establishing future precision medicine for ESCC patients, with the most recent results of clinical trials.

SOX2 inhibits LLGL2 polarity protein in esophageal squamous cell carcinoma via miRNA-142-3p

ABBREVIATIONS

CCK-8, Cell Counting Kit 8; Chip, Chromatin Immunoprecipitation; EC, Esophageal cancer; EMT, epithelial-to-mesenchymal transition; ESCC, Esophageal squamous cell carcinomas; LLGL2, lethal (2) giant larvae protein homolog 2; LLGL2ov, LLGL2 overexpression; MET, mesenchymal-epithelial transition; miRNAs, MicroRNAs; PRM-MS, Parallel reaction monitoring-Mass spectrometry; SD, Standard deviation; SOX, sex determining region Y (SRY)-like box; SOX2-Kd, SOX2-knockdwon; TUNEL, TdT-mediated dUTP Nick-End Labeling.

Downregulation of TUSC3 promotes EMT and hepatocellular carcinoma progression through LIPC/AKT axis

Background

Hepatocellular carcinoma (HCC) is one of the most common and malignant tumors in the digestive tract. Tumor Suppressor Candidate 3 (TUSC3) is one subunit of the endoplasmic reticulum Oligosaccharyl transferase (OST) complex, which plays an important role in N-glycosylation during the protein folding process. However, the role of TUSC3 in the initiation and progression of HCC has not been mentioned yet. In the present study, we aim to investigate the effects of TUSC3 on the initiation and progression of HCC.

Methods

Immunohistochemical assay and qRT-PCR were used to detect the expression of TUSC3 and lipase C hepatic type (LIPC) in HCC tissue and cells. Loss-of-function and gain-of-function were applied to detect the function of TUSC3 and LIPC in vivo and in vitro. Immunofluorescence assay and co-immunoprecipitation were used to detect the relationship between TUSC3 and LPC. Western blot was applied to detect the expression of epithelial–mesenchymal transition (EMT) markers and the Akt signaling pathway.

Results

TUSC3 was aberrantly decreased in hepatocellular carcinoma tissues compared to the matched adjacent normal tissues, which resulted in bigger size of tumor (P = 0.001, Table 2), worse differentiation (P = 0.006, Table 2) and an advanced BCLC stage. Down-regulation of TUSC3 led to the enhanced proliferation and migration of hepatocellular carcinoma cells in vivo and vitro, whereas the opposite effect could be observed in the TUSC3-overexpression group. The analysis of TUSC3 microarray showed that LIPC, a glycoprotein primarily synthesized and secreted by hepatocytes, was a downstream target of TUSC3, and it negatively modulated the development of HCC. The morphological changes in HCC cells indicated that TUSC3 regulated the epithelial-mesenchymal transition (EMT). Mechanistically, TUSC3 inhibited EMT progression through the LIPC/AKT axis.

Conclusion

Down-regulation of TUSC3 promotes EMT progression by activating AKT signaling via targeting LIPC in HCC, which is probably the possible mechanism driving TUSC3-deficient hepatocellular carcinoma cells toward a malignant phenotype.

Exploiting the Molecular Basis of Oesophageal Cancer for Targeted Therapies and Biomarkers for Drug Response: Guiding Clinical Decision-Making

Worldwide, oesophageal cancer is the sixth leading cause of deaths related to cancer and represents a major health concern. Sub-Saharan Africa is one of the regions of the world with the highest incidence and mortality rates for oesophageal cancer and most of the cases of oesophageal cancer in this region are oesophageal squamous cell carcinoma (OSCC). The development and progression of OSCC is characterized by genomic changes which can be utilized as diagnostic or prognostic markers. These include changes in the expression of various genes involved in signaling pathways that regulate pathways that regulate processes that are related to the hallmarks of cancer, changes in the tumor mutational burden, changes in alternate splicing and changes in the expression of non-coding RNAs such as miRNA. These genomic changes give rise to characteristic profiles of altered proteins, transcriptomes, spliceosomes and genomes which can be used in clinical applications to monitor specific disease related parameters. Some of these profiles are characteristic of more aggressive forms of cancer or are indicative of treatment resistance or tumors that will be difficult to treat or require more specialized specific treatments. In Sub-Saharan region of Africa there is a high incidence of viral infections such as HPV and HIV, which are both risk factors for OSCC. The genomic changes that occur due to these infections can serve as diagnostic markers for OSCC related to viral infection. Clinically this is an important distinction as it influences treatment as well as disease progression and treatment monitoring practices. This underlines the importance of the characterization of the molecular landscape of OSCC in order to provide the best treatment, care, diagnosis and screening options for the management of OSCC.

Identifying a confused cell identity for esophageal squamous cell carcinoma

The cell identity of malignant cells and how they acquire it are fundamental for our understanding of cancer. Here, we report that esophageal squamous cell carcinoma (ESCC) cells display molecular features equally similar but distinct to all three types of normal esophageal epithelial cells, which we term as confused cell identity (CCI). CCI is an independent prognostic marker associated with poor prognosis in ESCC. Further, we identify tropomyosin 4 (TPM4) as a critical CCI gene that promotes the aggressiveness of ESCC in vitro and in vivo. And TPM4 creates CCI through activating the Jak/STAT-SOX2 pathway. Thus, our study suggests an unrecognized feature of ESCC cells, which might be of value for clinic prognosis and potential interference.

PI3K/Akt/mTOR Signaling Pathway: Role in Esophageal Squamous Cell Carcinoma, Regulatory Mechanisms and Opportunities for Targeted Therapy

Esophageal squamous cell carcinoma (ESCC), is the most common type of esophageal cancer worldwide, mainly occurring in the Asian esophageal cancer belt, including northern China, Iran, and parts of Africa. Phosphatidlinositol 3-kinase (PI3K)/protein kinase B (Akt)/mammalian target of rapamycin (mTOR) signaling pathway is one of the most important cellular signaling pathways, which plays a crucial role in the regulation of cell growth, differentiation, migration, metabolism and proliferation. In addition, mutations in some molecules of PI3K/Akt/mTOR pathway are closely associated with survival and prognosis in ESCC patients. A large number of studies have found that there are many molecules in ESCC that can regulate the PI3K/Akt/mTOR pathway. Overexpression of these molecules often causes aberrant activation of PI3K/Akt/mTOR pathway. Currently, several effective PI3K/Akt/mTOR pathway inhibitors have been developed, which can play anticancer roles either alone or in combination with other inhibitors. This review mainly introduces the general situation of ESCC, the composition and function of PI3K/Akt/mTOR pathway, and regulatory factors that interact with PI3K/Akt/mTOR signaling pathway. Meanwhile, mutations and inhibitors of PI3K/Akt/mTOR pathway in ESCC are also elucidated.

Toward Targeted Therapies in Oesophageal Cancers: An Overview

Oesophageal cancer is one of the leading causes of cancer-related death worldwide. Oesophageal cancer occurs as squamous cell carcinoma (ESCC) or adenocarcinoma (EAC). Prognosis for patients with either ESCC or EAC is poor, with less than 20% of patients surviving more than 5 years after diagnosis. A major progress has been made in the development of biomarker-driven targeted therapies against breast and lung cancers, as well as melanoma. However, precision oncology for patients with oesophageal cancer is still virtually non-existent. In this review, we outline the recent advances in oesophageal cancer profiling and clinical trials based on targeted therapies in this disease.

TUSC3 inhibits cell proliferation and invasion in cervical squamous cell carcinoma via suppression of the AKT signalling pathway

The decreased expression of tumour suppressor candidate 3 (TUSC3) is associated with proliferation in several types of cancer, leading to an unfavourable prognosis. The present study aimed to assess the cellular and molecular function of TUSC3 in patients with cervical squamous cell carcinoma (CSCC). Levels of mRNA expressions of TUSC3 were analysed in CSCC tissues and six cell lines using qRT-PCR. Immunohistochemistry(IHC) was used to evaluate the protein expression level of TUSC3 in four paired specimens, 220 paraffin-embedded CSCC specimens and 60 cases of normal cervical tissues(NCTs), respectively. Short hairpin RNA interference was employed for TUSC3 knockdown. Cell proliferation, migration and invasion were evaluated using growth curve, MTT assay, wound healing, transwell assay and xenograft tumour model, respectively. The results demonstrated that TUSC3 mRNA and protein expression levels were downregulated in CSCC samples. Multivariate and univariate analyses indicated that TUSC3 was an independent prognostic factor for patients with CSCC. Decreased TUSC3 expression levels were significantly associated with proliferation and an aggressive phenotype of cervical cancer cells both in vitro and in vivo. Moreover, the knockdown of TUSC3 promoted migration and invasion of cancer cells, while the increased expression of TUSC3 exhibited the opposite effects. The downregulation of TUSC3 facilitated proliferation and invasion of CSCC cells through the activation of the AKT signalling pathway. Our data demonstrated that the downregulation of TUSC3 promoted CSCC cell metastasis via the AKT signalling pathway. Therefore, TUSC3 may serve as a novel prognostic marker and potential target for CSCC.

Luteolin attenuates cancer cell stemness in PTX-resistant oesophageal cancer cells through mediating SOX2 protein stability

Cancer drug resistance is a formidable obstacle that enhances cancer stem-like cell properties, tumour metastasis and relapse. Luteolin (Lut) is a natural flavonoid with strong antitumor effects. However, the underlying mechanism(s) by which Lut protects against paclitaxel-resistant (PTX-resistant) cancer cell remains unknown. Herein, we found that Lut significantly attenuated the stem-like properties of PTX-resistant cancer cells by downregulating the expression of SOX2 protein. Additionally, further study showed that Lut could inhibit the PI3K/AKT pathway to decrease the phosphorylation level of AKT(S473) and UBR5 expression, which is an ubiquitin E3 ligase that promotes SOX2 degradation. In addition, Lut also inhibited PTX-resistant cancer cell migration and invasion by blocking epithelial-mesenchymal transition (EMT). Importantly, Lut inhibited the tumorigenic ability of oesophageal PTX-resistant cancer cells and showed no obvious toxicity in vivo. Thus, Lut has potential as a promising agent for drug-resistant oesophageal cancer therapy.

SOX2 enhances cell survival and induces resistance to apoptosis under serum starvation conditions through the AKT/GSK-3β signaling pathway in esophageal squamous cell carcinoma

The human SOX2 gene was recently identified as a novel major oncogene, recurrently amplified and overexpressed in esophageal squamous cell carcinoma (ESCC). However, the role and molecular mechanism of SOX2 in the carcinogenesis of ESCC remain to be elucidated. The present study investigated the effect of SOX2 on ESCC cell survival and resistance to apoptosis under serum starvation conditions. An adenoviral vector-mediated expression system and RNA interference were used to study the effect of SOX2. The present results revealed that SOX2 promoted ESCC cell survival and enhanced resistance to apoptosis under serum starvation conditions, but not in culture conditions with serum. Mechanistically, SOX2 increased the expression levels of phosphorylated AKT and glycogen synthase kinase-3β (GSK-3β), a downstream factor of AKT, under serum starvation conditions, leading to the promotion of ESCC cell survival. Additionally, SOX2 activated AKT through the PTEN/PI3K/phosphoinositide-dependent protein kinase 1 and mammalian target of rapamycin complex 2 signaling pathways. Therefore, SOX2 may facilitate the survival of ESCC cells under poor nutrient conditions by activating the AKT/GSK-3β signaling pathway.

SOX2 and squamous cancers

SOX2 is a pleiotropic nuclear transcription factor with major roles in stem cell biology and in development. Over the last 10 years SOX2 has also been implicated as a lineage-specific oncogene, notably in squamous carcinomas but also neurological tumours, particularly glioblastoma. Squamous carcinomas (SQCs) comprise a common group of malignancies for which there are no targeted therapeutic interventions. In this article we review the molecular epidemiological and laboratory evidence linking SOX2 with squamous carcinogenesis, explore in detail the multifaceted impact of SOX2 in SQC, describe areas of uncertainty and highlight areas for potential future research.

Sox2 induces tumorigenesis and angiogenesis of early-stage esophageal squamous cell carcinoma through secretion of Suprabasin

Early stage of esophageal squamous cell carcinoma (ESCC) is known to be accompanied by angiogenesis and morphological changes of microvessels. Transcription factor Sox2 is amplified in various cancers including ESCC, but the role of Sox2 in the carcinogenesis and angiogenesis has not been determined. Hence, we aimed to investigate the role of Sox2 in the early stage of ESCC. We found that the expression of Sox2 was significantly higher in early-stage ESCC tissues than that in their adjacent normal tissues. We then established Sox2-inducible normal human esophageal squamous cell line (HetSox2) to investigate the role of Sox2 in esophageal carcinogenesis and angiogenesis in vitro. Sox2 overexpression led to increased cell proliferation and spheroid formation. The culture supernatant of Sox2-overexpressing HetSox2 induced migration and sprouting of endothelial cell line HUVEC (human umbilical vein endothelial cell). As for the mechanism, we found that the expression of secreted protein Suprabasin was directly induced by Sox2. Suprabasin enhanced proliferation of normal human esophageal squamous cells when added to the culture. Moreover, Suprabasin enhanced migration and sprouting of HUVEC cells, which were observed with the culture supernatant of Sox2-overexpressing HetSox2. This angiogenic effect of Suprabasin was abolished by inhibiting AKT phosphorylation, which suggested its dependence on AKT signaling. Finally, we showed that Suprabasin expression and the density of microvessels were significantly higher in ESCC tissues with high Sox2 expression. Our study suggested that increased Sox2 expression in esophageal squamous cells induced Suprabasin expression, and as a result initiated the carcinogenesis via increased cell proliferation and angiogenesis.

SOX2-Upregulated microRNA-30e Promotes the Progression of Esophageal Cancer via Regulation of the USP4/SMAD4/CK2 Axis

Esophageal cancer (EC) is a highly aggressive disease, and its progression involves a complex gene regulation network. Transcription factor SOX2 is amplified in various cancers including EC. A pathway involving SOX2 regulation of microRNAs (miRNAs) and their target genes has been previously revealed. This study aims to delineate the ability of SOX2 to influence the EC progression, with the involvement of miR-30e/USP4/SMAD4/CK2 axis. SOX2 expression was first examined in the clinical tissue samples from 30 EC patients. Effects of SOX2 on proliferation, migration, and invasion alongside tumorigenicity of transfected cells were examined by means of gain- and loss-of-function experiments. EC tissues and cells exhibited high expression of SOX2, miR-30e, and CK2 and poor expression of USP4 and SMAD4. Mechanistically, SOX2 was positively correlated with miR-30e and upregulated the expression of miR-30e. miR-30e specifically targeted USP4, which induced deubiquitination of SMAD4 and promoted its expression. Meanwhile, SMAD4 was enriched in the CK2 promoter region and thus inhibited its expression. SOX2 stimulated EC cell proliferative, invasive, and migratory capacities in vitro and tumor growth in vivo by regulating the miR-30e/USP4/SMAD4/CK2 axis. Collectively, our work reveals a novel SOX2-mediated regulatory network in EC that may be a viable target for EC treatment.

RCC2 Promotes Esophageal Cancer Growth by Regulating Activity and Expression of the Sox2 Transcription Factor

Regulator of chromosome condensation 2 (RCC2) is a protein located in the centrosome, which ensures that cell division proceeds properly. Previous reports show that RCC2 is overexpressed in some cancers and could play a key role in tumor development, but the mechanisms concerning how this occurs are not understood. Furthermore, no evidence exists regarding its role in esophageal cancer. We studied the relevance of RCC2 in esophageal cancer growth and its regulation on Sox2, an important transcription factor promoting esophageal cancer. RCC2 was overexpressed in esophageal tumors compared with normal tissue, and this overexpression was associated with tumorigenicity by increasing cell proliferation, anchorage-independent growth, and migration. These oncogenic effects were accompanied by overexpression of Sox2. RCC2 upregulated and stabilized Sox2 expression and its target genes by inhibiting ubiquitination-mediated proteasome degradation. Likewise, RCC2 increased the transcriptional activity and promoter binding of Sox2. In vivo studies indicated that RCC2 and Sox2 were overexpressed in esophageal tumors compared with normal tissue, and this upregulation occurs in the esophageal basal cell layer for both proteins. In conditional knockout mice, RCC2 deletion decreased the tumor nodule formation and progression in the esophagus compared with wild-type mice. Proliferating cell nuclear antigen expression, a cell proliferation marker, was also downregulated in RCC2 knockout mice. Overall, our data show for the first time that RCC2 is an important protein for the stabilization and transcriptional activation of Sox2 and further promotion of malignancy in esophageal cancer. IMPLICATIONS: This study shows that RCC2 controls Sox2 expression and transcriptional activity to mediate esophageal cancer formation.

Functional characterization of SOX2 as an anticancer target

SOX2 is a well-characterized pluripotent factor that is essential for stem cell self-renewal, reprogramming, and homeostasis. The cellular levels of SOX2 are precisely regulated by a complicated network at the levels of transcription, post-transcription, and post-translation. In many types of human cancer, SOX2 is dysregulated due to gene amplification and protein overexpression. SOX2 overexpression is associated with poor survival of cancer patients. Mechanistically, SOX2 promotes proliferation, survival, invasion/metastasis, cancer stemness, and drug resistance. SOX2 is, therefore, an attractive anticancer target. However, little progress has been made in the efforts to discover SOX2 inhibitors, largely due to undruggable nature of SOX2 as a transcription factor. In this review, we first briefly introduced SOX2 as a transcription factor, its domain structure, normal physiological functions, and its involvement in human cancers. We next discussed its role in embryonic development and stem cell-renewal. We then mainly focused on three aspects of SOX2: (a) the regulatory mechanisms of SOX2, including how SOX2 level is regulated, and how SOX2 cross-talks with multiple signaling pathways to control growth and survival; (b) the role of SOX2 in tumorigenesis and drug resistance; and (c) current drug discovery efforts on targeting SOX2, and the future perspectives to discover specific SOX2 inhibitors for effective cancer therapy.

Melanoma stem cell maintenance and chemo-resistance are mediated by CD133 signal to PI3K-dependent pathways

Melanoma stem cells (MSCs) are characterized by their unique cell surface proteins and aberrant signaling pathways. These stemness properties are either in a causal or consequential relationship to melanoma progression, treatment resistance and recurrence. The functional analysis of CD133⁺ and CD133^- cells in vitro and in vivo revealed that melanoma progression and treatment resistance are the consequences of CD133 signal to PI3K pathway. CD133 signal to PI3K pathway drives two downstream pathways, the PI3K/Akt/MDM2 and the PI3K/Akt/MKP-1 pathways. Activation of PI3K/Akt/MDM2 pathway results in the destabilization of p53 protein, while the activation of PI3K/Akt/MKP-1 pathway results in the inhibition of mitogen-activated protein kinases (MAPKs) JNK and p38. Activation of both pathways leads to the inhibition of fotemustine-induced apoptosis. Thus, the disruption of CD133 signal to PI3K pathway is essential to overcome Melanoma resistance to fotemustine. The pre-clinical verification of in vitro data using xenograft mouse model of MSCs confirmed the clinical relevance of CD133 signal as a therapeutic target for melanoma treatment. In conclusion, our study provides an insight into the mechanisms regulating MSCs growth and chemo-resistance and suggested a clinically relevant approach for melanoma treatment.

Heterogeneous genomic aberrations in esophageal squamous cell carcinoma: a review

Esophageal cancer (EC) causes hundreds of thousands of deaths a year worldwide, especially the major subtype esophageal squamous cell carcinoma (ESCC). With the advent of next-generation sequencing and the availability of commercial microarrays, abnormities in genetic levels have been revealed in various independent researches. High frequencies of structure variations (SVs), single nucleotide variations (SNVs) and copy-number alterations (CNAs) in ESCCs are uncovered, and ESCC shows high levels of inter- and intratumor heterogeneity, implying diverse evolutionary trajectories. This review tries to explain the pathogenesis of ESCC on the scope of most often mutated genes based on prior studies, hopes to offer some hints for diagnosis and therapy in clinic.

SOX2 protein biochemistry in stemness, reprogramming, and cancer: the PI3K/AKT/SOX2 axis and beyond

Research of the past view years expanded our understanding of the various physiological functions the cell-fate determining transcription factor SOX2 exerts in ontogenesis, reprogramming, and cancer. However, while scientific reports featuring novel and exciting aspects of SOX2-driven biology are published in near weekly routine, investigations in the underlying protein-biochemical processes that transiently tailor SOX2 activity to situational demand are underrepresented and have not yet been comprehensively summarized. Largely unrecognizable to modern array or sequencing-based technology, various protein secondary modifications and concomitant function modulations have been reported for SOX2. The chemical modifications imposed onto SOX2 are inherently heterogeneous, comprising singular or clustered events of phosphorylation, methylation, acetylation, ubiquitination, SUMOylation, PARPylation, and O-glycosylation that reciprocally affect each other and critically impact SOX2 functionality, often in a tissue and species-specific manner. One recurring regulatory principle though is the canonical PI3K/AKT signaling axis to which SOX2 relates in various entangled, albeit not exclusive ways. Here we provide a comprehensive review of the current knowledge on SOX2 protein modifications, their proposed relationship to the PI3K/AKT pathway, and regulatory influence on SOX2 with regards to stemness, reprogramming, and cancer.

The expression and prognostic value of SOX2, β-catenin and survivin in esophageal squamous cell carcinoma

Aim: We mainly explored the effect of SOX2, β-catenin and survivin on prognosis in esophageal squamous cell carcinoma. Materials & methods: Immunohistochemistry was used to examine the expression of SOX2, β-catenin and survivin. χ² test was used to analyze the relationship between proteins and clinicopathological parameters. Survival analysis was used to investigate the effect of three proteins on prognosis. Results: SOX2 was related to lymph node metastasis (p = 0.004) and vascular invasion (p = 0.041). β-catenin was associated with depth of invasion (p = 0.014), lymph node metastasis (p = 0.032) and postoperative chemoradiotherapy (p < 0.001). Survivin was related to gender (p = 0.022) and nerve invasion (p = 0.014). There was a positive correlation between SOX2 and β-catenin. Patients with SOX2 and β-catenin overexpression had poor prognosis. Survivin-positive patients who received postoperative chemoradiotherapy had a short time. Conclusion: SOX2, β-catenin and survivin can be used as prognostic markers of esophageal squamous cell carcinoma.

SOX2 Expression Is an Independent Predictor of Oral Cancer Progression

Potentially malignant oral lesions, mainly leukoplakia, are common. Malignant transformation varies widely, even in the absence of histological features such as dysplasia. Hence, there is a need for novel biomarker-based systems to more accurately predict the risk of cancer progression. The pluripotency transcription factor SOX2 is frequently overexpressed in cancers, including oral squamous cell carcinoma (OSCC), thereby providing a link between malignancy and stemness. This study investigates the clinical relevance of SOX2 protein expression in early stages of oral carcinogenesis as a cancer risk biomarker, and also its impact on prognosis and disease outcome at late stages of OSCC progression. SOX2 expression was evaluated by immunohistochemistry in 55 patients with oral epithelial dysplasia, and in 125 patients with OSCC, and correlated with clinicopathological data and outcomes. Nuclear SOX2 expression was detected in four (7%) cases of oral epithelial dysplasia, using a cut-off of 10% stained nuclei, and in 16 (29%) cases when any positive nuclei was evaluated. Univariate analysis showed that SOX2 expression and histopathological grading were significantly associated with oral cancer risk; and both were found to be significant independent predictors in the multivariate analysis. Nuclear SOX2 expression was also found in 49 (39%) OSCC cases, was more frequent in early tumor stages and N0 cases, and was associated with a better survival. In conclusion, SOX2 expression emerges as an independent predictor of oral cancer risk in patients with oral leukoplakia. These findings underscore the relevant role of SOX2 in early oral tumorigenesis rather than in tumor progression.

SOX2 antagonizes WWC1 to drive YAP1 activation in esophageal squamous cell carcinoma

Whether SOX2 and ACTL6A/TP63 interact with the Hippo-YAP1 pathway in esophageal squamous cell carcinoma (ESCC) remains unclear. Here, we reveal that SOX2, ACTL6A, and TP63 are co-amplified and upregulated in ESCC samples. Multiple SOX2 binding peaks in the locus of WWC1, a Hippo-YAP1 regulator, and an inverse correlation between the expression of SOX2 and WWC1 are identified, suggesting direct repression of WWC1 by SOX2. Expression scores of SOX2 are higher in tumors than normal tissues and positively correlated with nuclear YAP1 staining in primary ESCC. Moreover, SOX2 gain-of-function significantly promotes nuclear YAP1 expression in ESCC cells while silencing of SOX2 expression inhibits YAP1 activation. SOX2 overexpression leads to a significant enhancement of cell migration and invasion as well as chemoresistance to cisplatin, whereas knockdown of SOX2 or ectopic expression of WWC1 suppresses the SOX2-induced migration ability and invasive potential. Disruption of this SOX2-WWC1-YAP1 axis could be a therapeutic strategy for SOX2-dependent tumors.

Downregulation of SOX2 may be targeted by miR-590-5p and inhibits epithelial-to-mesenchymal transition in non-small-cell lung cancer

Non-small-cell lung cancer (NSCLC) is the leading type of cancer worldwide and sex determining region Y-box 2 (SOX2) has been implicated as an oncogene in various types of cancer. In the present study, SOX2 was positively associated with NSCLC stage and lymph node metastasis. Wound healing and Transwell assays demonstrated that knockdown of SOX2 inhibited A549 and H1299 cell migration. Furthermore, it was identified that knockdown of SOX2 inhibited epithelial-to-mesenchymal transition of NSCLC cells, which was demonstrated by increased expression of epithelial-cadherin and decreased expression of vimentin, zinc finger protein SNAI1 and zinc finger protein SNAI2. It was then demonstrated that SOX2 may be targeted by microRNA (miR)-590-5p, which indicated a potential therapeutic strategy for NSCLC focusing on the miR-590-5p/SOX2 axis.

The role of SOX family members in solid tumours and metastasis

Cancer is a heavy burden for humans across the world with high morbidity and mortality. Transcription factors including sex determining region Y (SRY)-related high-mobility group (HMG) box (SOX) proteins are thought to be involved in the regulation of specific biological processes. The deregulation of gene expression programs can lead to cancer development. Here, we review the role of the SOX family in breast cancer, prostate cancer, renal cell carcinoma, thyroid cancer, brain tumours, gastrointestinal and lung tumours as well as the entailing therapeutic implications. The SOX family consists of more than 20 members that mediate DNA binding by the HMG domain and have regulatory functions in development, cell-fate decision, and differentiation. SOX2, SOX4, SOX5, SOX8, SOX9, and SOX18 are up-regulated in different cancer types and have been found to be associated with poor prognosis, while the up-regulation of SOX11 and SOX30 appears to be favourable for the outcome in other cancer types. SOX2, SOX4, SOX5 and other SOX members are involved in tumorigenesis, e.g. SOX2 is markedly up-regulated in chemotherapy resistant cells. The SoxF family (SOX7, SOX17, SOX18) plays an important role in angio- and lymphangiogenesis, with SOX18 seemingly being an attractive target for anti-angiogenic therapy and the treatment of metastatic disease in cancer. In summary, SOX transcription factors play an important role in cancer progression, including tumorigenesis, changes in the tumour microenvironment, and metastasis. Certain SOX proteins are potential molecular markers for cancer prognosis and putative potential therapeutic targets, but further investigations are required to understand their physiological functions.

AKT drives SOX2 overexpression and cancer cell stemness in esophageal cancer by protecting SOX2 from UBR5-mediated degradation

As a transcription factor critical for embryonic and adult stem cell self-renewal and function, SOX2 gene amplification has been recognized as a driving factor for various cancers including esophageal cancer. SOX2 overexpression occurs more broadly in cancer than gene amplification, but the mechanism is poorly understood. Here we showed that in esophageal cancer cell lines the levels of SOX2 proteins are not directly correlated to the copy numbers of SOX2 genes and are strongly influenced by proteostasis. We showed that AKT is a major determinant for SOX2 overexpression and does so by protecting SOX2 from ubiquitin-dependent protein degradation. We identified UBR5 as a major ubiquitin E3 ligase that induces SOX2 degradation through ubiquitinating SOX2 at lysine 115. Phosphorylation of SOX2 at threonine 116 by AKT inhibits the interaction of UBR5 with SOX2 and thus stabilizes SOX2. We provided evidence that AKT inhibitor can effectively downregulate SOX2 and suppress esopheageal cancer cell proliferation and stemness. Taken together, our study provides new insight into the mechanism of SOX2 overexpression in cancer and evidence for targeting AKT as a potential therapeutic strategy for SOX2-positive cancers.

Sox2 promotes tumor aggressiveness and epithelial‑mesenchymal transition in tongue squamous cell carcinoma

Tongue squamous cell carcinoma (TSCC) is highly malignant and poorly differentiated, resulting in a high frequency of local recurrence and distant metastases. Sox2 (Sry-box2), an important factor in embryonic development and cell differentiation, has been shown to associate with malignant phenotypes and epithelial-mesenchymal transition (EMT) progression in numerous types of human tumors. However, the clinical relevance and molecular mechanisms of Sox2 in TSCC remain unclear. In the present study, the expression levels of Sox2 were assessed in 61 pairs of TSCC samples and corresponding adjacent non-cancerous tissues using immunohistochemical methods. Associations between Sox2 expression and clinicopathological features were evaluated. Furthermore, Sox2 was overexpressed and inhibited using full-length Sox2 cDNA and short hairpin RNA (shRNA) transfection in UM2 and Cal27 cell lines, respectively. The malignant phenotypes were assessed by plate clone formation assays, wound-healing assays and Transwell assays. EMT markers (E-cadherin, vimentin, Twist, Slug and Snail) and β-catenin were detected by reverse transcription-polymerase chain reaction and western blot analysis following the alterations of Sox2 expression. The results indicated that Sox2 expression was markedly upregulated in TSCC samples and was significantly associated with tumor growth (pT stage), cell differentiation, lymphatic metastasis (pN stage) and clinical stage (pTNM stage). Cal27-shRNA-Sox2 cells not only exhibited a decreased capacity for cell proliferation, but also suppressed cell migration and invasion, and an attenuated colony formation capacity. By contrast, UM2-Sox2 cells exhibited accelerated cell malignant phenotypes and EMT progression. Moreover, when the expression of Sox2 was decreased by shRNA transduction, β-catenin expression was attenuated. An opposing phenomenon was observed in UM2-Sox2 cells. In conclusion, this study suggests that Sox2 expression serves a role in TSCC malignant phenotypes and EMT progression, and that β-catenin may act as a modulated factor in this progression.

Natural Borneol Enhances Paclitaxel-Induced Apoptosis of ESCC Cells by Inactivation of the PI3K/AKT

Paclitaxel (PTX) has been used in a variety of malignancies for inhibiting tumor development and improving survival. However, its clinical application is limited due to poor solubility, drug resistance, and gastrointestinal reactions. Natural borneol (NB), as a promoter, could help to improve drug absorption. Therefore, the aims of the present study were to investigate the ability of NB to synergize with PTX to induce human esophageal squamous cell carcinoma (ESCC) cells apoptosis and the underlying mechanism of synergistic effects. In this study, our findings showed that NB could effectively synergize with PTX to inhibit the survival of ESCC cells by inducing apoptosis. The molecular mechanism by western blotting elucidated that combination treatment with PTX and NB significantly activated apoptotic pathway by triggering upregulation of cleaved caspase-3 expression and downregulation of survivin and P-AKT expression. These results demonstrated that NB could strongly potentiate PTX-induced apoptosis in ESCC cells through suppressing PI3K/AKT pathway. Thus, the combination therapy with NB and PTX might be a promising treatment strategy for human esophageal cancer.

PRACTICAL APPLICATION

Esophageal cancer is one of the most common cancers in the world. It has brought about a major public health problem. Many natural agents have been employed in the synergized treatments of esophageal cancer. This study provides a comprehensive way to investigate the ability of borneol to synergize with paclitaxel to induce human esophageal squamous cell carcinoma cells apoptosis and the underlying mechanism of synergistic effects. The research showed that the combination treatment with some natural agents might be a promising treatment strategy for human esophageal cancer.

Expression and functional regulation of stemness gene Lgr5 in esophageal squamous cell carcinoma

Cancer stem cells (CSCs) are defined as a rare subpopulation of undifferentiated cells with biological characteristics that include the capacity for self-renewal, differentiation into various lineages, and tumor initiation. To explore the mechanism of CSCs in esophageal squamous cell carcinoma (ESCC), we focused on Leucine-rich repeat containing G protein-coupled receptor 5 (Lgr5), a target gene of the Wnt signaling pathway, which has been identified as a marker of intestinal stem cells and shown to be overexpressed in several human malignancies. Lgr5 expression was significantly correlated with lymph node metastasis, increased depth of invasion, increased tumor size, advanced differentiation, higher AJCC stage and poorer survival. Silencing of Lgr5 expression in the ESCC cell line KYSE450 by small interfering RNA (siRNA) strongly inhibited cell proliferation, migration and invasion ability, the expression of CSCs-related genes and Wnt/β-catenin signaling. In addition, Lgr5 was highly expressed in ESCC spheroid body cells, which were identified by high expression of CSCs-related genes, and high tumorigenicity in vivo. Taken together, these results demonstrate that Lgr5 activation of Wnt/β-catenin signaling is a potential mechanism to promote the progression of ESCC and ESCC stem cell renewal, and Lgr5 may be used as a molecular target for the development of treatments for ESCC.

Genomic and Epigenomic Aberrations in Esophageal Squamous Cell Carcinoma and Implications for Patients

Esophageal squamous cell carcinoma (ESCC) is a common malignancy without effective therapy. The exomes of more than 600 ESCCs have been sequenced in the past 4 years, and numerous key aberrations have been identified. Recently, researchers reported both inter- and intratumor heterogeneity. Although these are interesting observations, their clinical implications are unclear due to the limited number of samples profiled. Epigenomic alterations, such as changes in DNA methylation, histone acetylation, and RNA editing, also have been observed in ESCCs. However, it is not clear what proportion of ESCC cells carry these epigenomic aberrations or how they contribute to tumor development. We review the genomic and epigenomic characteristics of ESCCs, with a focus on emerging themes. We discuss their clinical implications and future research directions.

SOX2-silenced squamous cell carcinoma: a highly malignant form of esophageal cancer with SOX2 promoter hypermethylation

This study originally aimed to investigate whether the overexpression of SOX2 is associated with the poor prognosis of patients with squamous cell carcinoma of the esophagus. However, we unexpectedly found that esophageal squamous cell carcinomas completely lacking SOX2 expression showed distinct pathologic features and highly aggressive clinical courses. The study cohort consisted of 113 consecutive patients with esophageal squamous cell carcinoma who underwent surgical resection without neoadjuvant therapy. Immunostaining on tissue microarrays and whole sections revealed that 8/113 (7%) cases were entirely negative for this transcriptional factor. SOX2-negative cancers were histologically less differentiated (P=0.002) and showed higher pT and pStages (P=0.003 and 0.007, respectively) than SOX2-positive cases. A remarkable finding was widespread lymphatic infiltration distant from the primary invasive focus, which was observed in 4 SOX2-negative cancers (50%), but none of the SOX2-positive cases. All separate dysplastic lesions observed in SOX2-negative cases were also SOX2-negative. The negative expression of SOX2 appeared to be an independent poor prognostic factor (OR=7.05, 95% CI=1.27-39.0). No mutations were identified in the coding or non-coding regions of SOX2. Fluorescent in situ hybridization did not show any copy-number variations in this gene. Since the SOX2 promoter contains an extensive CpG island, SOX2-negative cases underwent methylation-specific PCR, which disclosed promoter hypermethylation in all cases. In conclusion, SOX2-silenced squamous cell carcinomas of the esophagus appear to be a minor, but distinct form of malignancy characterized by extensive lymphatic invasion, a poor prognosis, and potential association with multiple SOX2-negative neoplastic lesions. The hypermethylation of the promoter region is seemingly a critical epigenetic event leading to SOX2 silencing.

SOX2 functions as a molecular rheostat to control the growth, tumorigenicity and drug responses of pancreatic ductal adenocarcinoma cells

Pancreatic ductal adenocarcinoma (PDAC) is a highly deadly malignancy. Expression of the stem cell transcription factor SOX2 increases during progression of PDAC. Knockdown of SOX2 in PDAC cell lines decreases growth in vitro; whereas, stable overexpression of SOX2 in one PDAC cell line reportedly increases growth in vitro. Here, we reexamined the role of SOX2 in PDAC cells, because inducible SOX2 overexpression in other tumor cell types inhibits growth. In this study, four PDAC cell lines were engineered for inducible overexpression of SOX2 or inducible knockdown of SOX2. Remarkably, inducible overexpression of SOX2 in PDAC cells inhibits growth in vitro and reduces tumorigenicity. Additionally, inducible knockdown of SOX2 in PDAC cells reduces growth in vitro and in vivo. Thus, growth and tumorigenicity of PDAC cells is highly dependent on the expression of optimal levels of SOX2 – a hallmark of molecular rheostats. We also determined that SOX2 alters the responses of PDAC cells to drugs used in PDAC clinical trials. Increasing SOX2 reduces growth inhibition mediated by MEK and AKT inhibitors; whereas knockdown of SOX2 further reduces growth when PDAC cells are treated with these inhibitors. Thus, targeting SOX2, or its mode of action, could improve the treatment of PDAC.

Esophageal Cancer: Genomic and Molecular Characterization, Stem Cell Compartment and Clonal Evolution

Esophageal cancer (EC) is the eighth most common cancer and is the sixth leading cause of death worldwide. The incidence of histologic subtypes of EC, esophageal adenocarcinoma (EAC) and esophageal squamous carcinoma (ESCC), display considerable geographic variation. EAC arises from metaplastic Barrett's esophagus (BE) in the context of chronic inflammation secondary to exposure to acid and bile. The main risk factors for developing ESCC are cigarette smoking and alcohol consumption. The main somatic genetic abnormalities showed a different genetic landscape in EAC compared to ESCC. EAC is a heterogeneous cancer dominated by copy number alterations, a high mutational burden, co-amplification of receptor tyrosine kinase, frequent TP53 mutations. The cellular origins of BE and EAC are still not understood: animal models supported a cellular origin either from stem cells located in the basal layer of esophageal epithelium or from progenitors present in the cardia region. Many studies support the existence of cancer stem cells (CSCs) able to initiate and maintain EAC or ESCC. The exact identification of these CSCs, as well as their role in the pathogenesis of EAC and ESCC remain still to be demonstrated. The reviewed studies suggest that current molecular and cellular characterization of EAC and ESCC should serve as background for development of new treatment strategies.

Targeting super-enhancer-associated oncogenes in oesophageal squamous cell carcinoma

OBJECTIVES

Oesophageal squamous cell carcinoma (OSCC) is an aggressive malignancy and the major histological subtype of oesophageal cancer. Although recent large-scale genomic analysis has improved the description of the genetic abnormalities of OSCC, few targetable genomic lesions have been identified, and no molecular therapy is available. This study aims to identify druggable candidates in this tumour.

DESIGN

High-throughput small-molecule inhibitor screening was performed to identify potent anti-OSCC compounds. Whole-transcriptome sequencing (RNA-Seq) and chromatin immunoprecipitation sequencing (ChIP-Seq) were conducted to decipher the mechanisms of action of CDK7 inhibition in OSCC. A variety of in vitro and in vivo cellular assays were performed to determine the effects of candidate genes on OSCC malignant phenotypes.

RESULTS

The unbiased high-throughput small-molecule inhibitor screening led us to discover a highly potent anti-OSCC compound, THZ1, a specific CDK7 inhibitor. RNA-Seq revealed that low-dose THZ1 treatment caused selective inhibition of a number of oncogenic transcripts. Notably, further characterisation of the genomic features of these THZ1-sensitive transcripts demonstrated that they were frequently associated with super-enhancer (SE). Moreover, SE analysis alone uncovered many OSCC lineage-specific master regulators. Finally, integrative analysis of both THZ1-sensitive and SE-associated transcripts identified a number of novel OSCC oncogenes, including PAK4, RUNX1, DNAJB1, SREBF2 and YAP1, with PAK4 being a potential druggable kinase.

CONCLUSIONS

Our integrative approaches led to a catalogue of SE-associated master regulators and oncogenic transcripts, which may significantly promote both the understanding of OSCC biology and the development of more innovative therapies.

SOX2 function and Hedgehog signaling pathway are co-conspirators in promoting androgen independent prostate cancer

Developmentally inclined hedgehog (HH) signaling pathway and pluripotency inducing transcription factor SOX2 have been known to work syngerstically during cellular reprogramming events to facilitate efficient differentiation. Hence, it is not surprising that both the factors are actively involved in arbitrating malignant growth, including prostate cancer progression. Here, we have described in details the potential mechanisms by which SOX2 effects neoplastic characteristics in prostate cancer and investigated the consequences of simultaneous down-regulation of SOX2 and HH pathway in androgen-independent human prostate cancer cells. Expression of SOX2 has been determined by qRT-PCR, western blot, immunohistochemistry and immunocytochemistry analyses; its functional role determined by gene knockdown using RNAi and over-expression via chemical activation in HaCaT, DU145 and PC-3 cells. Changes in level of cell proliferation, migration and apoptosis profiles were measured by MTT, FACS, chromatin condensation and scratch assays respectively. SOX2 was expressed in all the three cell lines and its inhibition reduced cell proliferation and induced apoptosis. Most importantly, when both SOX2 and HH pathway were targeted simultaneously, cell proliferation was greatly reduced, apoptotic cell population increased drastically and migration potential was reduced. Moreover, gene expression of EMT markers such as E-cadherin and apoptosis related Bcl-2 and Bax was also investigated wherein decrease in E-cadherin and Bcl-2 levels and increase in Bax expression further substantiating our claim. These findings could provide the basis for a novel therapeutic strategy targeting both the effector i.e. SOX2 and perpetuator i.e. HH pathway of aggressive tumorigenic properties in androgen independent prostate cancer.

SOX2 and PI3K Cooperate to Induce and Stabilize a Squamous-Committed Stem Cell Injury State during Lung Squamous Cell Carcinoma Pathogenesis

Although cancers are considered stem cell diseases, mechanisms involving stem cell alterations are poorly understood. Squamous cell carcinoma (SQCC) is the second most common lung cancer, and its pathogenesis appears to hinge on changes in the stem cell behavior of basal cells in the bronchial airways. Basal cells are normally quiescent and differentiate into mucociliary epithelia. Smoking triggers a hyperproliferative response resulting in progressive premalignant epithelial changes ranging from squamous metaplasia to dysplasia. These changes can regress naturally, even with chronic smoking. However, for unknown reasons, dysplasias have higher progression rates than earlier stages. We used primary human tracheobronchial basal cells to investigate how copy number gains in SOX2 and PIK3CA at 3q26-28, which co-occur in dysplasia and are observed in 94% of SQCCs, may promote progression. We find that SOX2 cooperates with PI3K signaling, which is activated by smoking, to initiate the squamous injury response in basal cells. This response involves SOX9 repression, and, accordingly, SOX2 and PI3K signaling levels are high during dysplasia, while SOX9 is not expressed. By contrast, during regeneration of mucociliary epithelia, PI3K signaling is low and basal cells transiently enter a SOX2LoSOX9Hi state, with SOX9 promoting proliferation and preventing squamous differentiation. Transient reduction in SOX2 is necessary for ciliogenesis, although SOX2 expression later rises and drives mucinous differentiation, as SOX9 levels decline. Frequent coamplification of SOX2 and PIK3CA in dysplasia may, thus, promote progression by locking basal cells in a SOX2HiSOX9Lo state with active PI3K signaling, which sustains the squamous injury response while precluding normal mucociliary differentiation. Surprisingly, we find that, although later in invasive carcinoma SOX9 is generally expressed at low levels, its expression is higher in a subset of SQCCs with less squamous identity and worse clinical outcome. We propose that early pathogenesis of most SQCCs involves stabilization of the squamous injury state in stem cells through copy number gains at 3q, with the pro-proliferative activity of SOX9 possibly being exploited in a subset of SQCCs in later stages.

Personalized and targeted therapy of esophageal squamous cell carcinoma: an update

Esophageal squamous cell carcinoma (ESCC) is a deadly disease that requires extensive research. In this review, we update recent progress in the research area of targeted therapy for ESCC. SOX2 and its associated proteins (e.g., ΔNP63α), which regulate lineage survival of ESCC cells, are proposed as therapeutic targets. It is believed that targeting the lineage-survival mechanism may be more effective than targeting other mechanisms. With the advent of a new era of personalized targeted therapy, there is a need to move from the tumor-centric model into an organismic model.

Carvedilol-responsive microRNAs, miR-199a-3p and -214 protect cardiomyocytes from simulated ischemia-reperfusion injury

The nonselective β-adrenergic receptor antagonist (β-blocker) carvedilol has been shown to protect against myocardial injury, but the detailed underlying mechanisms are unclear. We recently reported that carvedilol stimulates the processing of microRNA (miR)-199a-3p and miR-214 in the heart via β-arrestin1-biased β1-adrenergic receptor (β1AR) cardioprotective signaling. Here, we investigate whether these β-arrestin1/β1AR-responsive miRs mediate the beneficial effects of carvedilol against simulated ischemia/reperfusion (sI/R). Using cultured cardiomyocyte cell lines and primary cardiomyocytes, we demonstrate that carvedilol upregulates miR-199a-3p and miR-214 in both ventricular and atrial cardiomyocytes subjected to sI/R. Overexpression of the two miRs in cardiomyocytes mimics the effects of carvedilol to activate p-AKT survival signaling and the expression of a downstream pluripotency marker Sox2 in response to sI/R. Moreover, carvedilol-mediated p-AKT activation is abolished by knockdown of either miR-199a-3p or miR-214. Along with previous studies to directly link the cardioprotective actions of carvedilol to upregulation of p-AKT/stem cell markers, our findings suggest that the protective roles of carvedilol during ischemic injury are in part attributed to activation of these two protective miRs. Loss of function of miR-199a-3p and miR-214 also increases cardiomyocyte apoptosis after sI/R. Mechanistically, we demonstrate that miR-199a-3p and miR-214 repress the predictive or known apoptotic target genes ddit4 and ing4, respectively, in cardiomyocytes. These findings suggest pivotal roles for miR-199a-3p and miR-214 as regulators of cardiomyocyte survival and contributors to the functional benefits of carvedilol therapy.

Stress-triggered atavistic reprogramming (STAR) addiction: driving force behind head and neck cancer?

Recent results of the Cancer Genome Atlas on head and neck squamous cell carcinoma (HNSCC) revealed that HNSCC lacked predominant gain-of-function mutations in oncogenes, whereas an essential role for epigenetics in oncogenesis has become apparent. In parallel, it has gained general acceptance that cancer is considered as complex adaptive system, which evolves responding environmental selective pressures. This somatic evolution appears to proceed concurrently with the acquisition of an atavistic pluripotent state (i.e., "stemness"), which is inducible by intrinsic epigenetic reprogramming program as demonstrated by induced pluripotent stem (iPS) cells. This Nobel prize-winning discovery has markedly accelerated and expanded cancer stem cell research from the point of epigenetic reprogramming. Taken together, we hypothesize that stress-triggered atavistic reprogramming (STAR) may be the major driving force of HNSCC evolution. In this perspective, we discuss the possible mechanisms of STAR in HNSCC, focusing on recent topics of epigenetic reprogramming in developmental and cancer cell biology.

The role of pluripotency factors to drive stemness in gastrointestinal cancer

A better molecular understanding of gastrointestinal cancers arising either from the stomach, the pancreas, the intestine, or the liver has led to the identification of a variety of potential new molecular therapeutic targets. However, in most cases surgery remains the only curative option. The intratumoral cellular heterogeneity of cancer stem cells, bulk tumor cells, and stromal cells further limits straightforward targeting approaches. Accumulating evidence reveals an intimate link between embryonic development, stem cells, and cancer formation. In line, a growing number of oncofetal proteins are found to play common roles within these processes. Cancer stem cells share features with true stem cells by having the capacity to self-renew in a de-differentiated state, to generate heterogeneous types of differentiated progeny, and to give rise to the bulk tumor. Further, various studies identified genes in cancer stem cells, which were previously shown to regulate the pluripotency circuitry, particularly the so-called "Yamanaka-Factors" (OCT4, KLF4, SOX2, and c-MYC). However, the true stemness potential of cancer stem cells and the role and expression pattern of such pluripotency genes in various tumor cell types remain to be explored. Here, we summarize recent findings and discuss the potential mechanisms involved, and link them to clinical significance with a particular focus on gastrointestinal cancers.