Sox2 regulates the self-renewal of multiple types of stem cells. Recent studies suggest it also plays oncogenic roles in the formation of squamous carcinoma in several organs, including the esophagus where Sox2 is predominantly expressed in the basal progenitor cells of the stratified epithelium. Here, we use mouse genetic models to reveal a novel mechanism by which Sox2 cooperates with microenvironmental signals to malignantly transform epithelial progenitor cells. Conditional overexpression of Sox2 in basal cells expands the progenitor population in both the esophagus and forestomach. Significantly, carcinoma only develops in the forestomach where pathological progression correlates with inflammation and nuclear localization of Stat3 in progenitor cells. Importantly, co-overexpression of Sox2 and activated Stat3 (Stat3C) also transforms esophageal basal cells but not the differentiated suprabasal cells. These findings indicate basal stem/progenitor cells are the cells-of-origin of squamous carcinoma and that cooperation between Sox2 and microenvironment-activated Stat3 is required for Sox2-driven tumorigenesis.
Imaging strategies that detect early-stage esophageal squamous cell carcinoma (ESCC) could improve clinical outcomes, combined with endoscopic approaches. Periostin is an integrin-binding protein that is important in the tumor microenvironment. We created a fluorescent-labeled antibody that recognizes periostin and binds specifically to ESCC xenograft tumors in mice. In L2-cre;p120ctnLoxP/LoxP mice, which develop squamous cell cancers that resemble human ESCC, we visualized the probe in preneoplastic and neoplastic esophageal lesions using near-infrared fluorescent imaging with upper gastrointestinal endoscopy. Periostin might be a biomarker of the esophageal tumor microenvironment that can be used to detect preneoplastic lesions.
mouse model; neoplasm; extracellular matrix; POSTN
Insulin-like growth factor binding protein 3 (IGFBP3), a hypoxia-inducible gene, regulates a variety of cellular processes including cell proliferation, senescence, apoptosis and epithelial-mesenchymal transition (EMT). IGFBP3 has been linked to the pathogenesis of cancers. Most previous studies focus upon proapoptotic tumor suppressor activities of IGFBP3. Nevertheless, IGFBP3 is overexpressed in certain cancers including esophageal squamous cell carcinoma (ESCC), one of the most aggressive forms of squamous cell carcinomas (SCCs). The tumor-promoting activities of IGFBP3 remain poorly understood in part due to a lack of understanding as to how the tumor microenvironment may influence IGFBP3 expression and how IGFBP3 may in turn influence heterogeneous intratumoral cell populations. Here, we show that IGFBP3 overexpression is associated with poor postsurgical prognosis in ESCC patients. In xenograft transplantation models with genetically engineered ESCC cells, IGFBP3 contributes to tumor progression with a concurrent induction of a subset of tumor cells showing high expression of CD44 (CD44H), a major cell surface receptor for hyaluronic acid, implicated in invasion, metastasis and drug resistance. Our gain-of-function and loss-of-function experiments reveal that IGFBP3 mediates the induction of intratumoral CD44H cells. IGFBP3 cooperates with hypoxia to mediate the induction of CD44H cells by suppressing reactive oxygen species (ROS) in an insulin-like growth factor-independent fashion. Thus, our study sheds light on the growth stimulatory functions of IGFPB3 in cancer, gaining a novel mechanistic insight into the functional interplay between the tumor microenvironment and IGFBP3.
CD44; esophageal; squamous cell carcinoma; hypoxia; IGFBP3 and reactive oxygen species
Cells exposed to ER-stress undergo the Unfolded Protein Response (UPR) to avoid apoptosis, but may also activate autophagy. However, the signal for selection of one of these two protective responses is unknown. To clarify the key switch between autophagy and apoptosis, we examined the correlation of UPR-related signals with autophagy and/or apoptosis inductions in HepG2 cells exposed to three ER-stress inducers (NaF, tunicamycin, and thapsigargin) with time, including the effect of small interfering RNA on the cell responses. Thapsigargin-induced ER-stress caused only apoptosis after ∼2 hr with Ire1 phosphorylation, and Grp78, ATF4, and CHOP expressions. On the other hand, NaF- and tunicamycin-induced ER-stress caused only autophagy in the early stage by ∼8 hr with ATF4 expression and without CHOP expression. ATF4-siRNA completely inhibited the autophagy induced by NaF or tunicamycin with suppressed ATF4 protein and mRNA expressions, and also inhibited apoptosis by thapsigargin with suppression of both ATF4 and CHOP. CHOP-siRNA had no effect on autophagy activation by NaF and tunicamycin. On the other hand, CHOP-siRNA activated autophagy in thapsigargin-induced ER-stress with significant ATF4 expression, and suppressed apoptosis with CHOP suppression. These results showed that ATF4 is the key signal for autophagy induced by ER-stress, and that autophagy is switched to apoptosis by subsequent CHOP upregulation, suggesting that the changeover switch between autophagy and apoptosis is located between ATF4 to CHOP in the PERK pathway.
ER-stress; Autophagy; ATF4; CHOP; PERK pathway
The following four possible pathways for itching sensation have been suggested by recent reports. 1) Histaminergic TRPV1-positive pathway: Although histamine-positive nerve fibers cannot strictly be classified as “itch specific” due to their excitation also by pure algogens (making them itch-selective), the existence of a subpopulation of nociceptors responsible for itching is strongly suggested. Moreover, the TRPV1-expressing neurons have been suggested to be the main sensors and mediators of itching. 2) Histaminergic TRPV1-negative pathway: The scratching behavior caused by itching was not different between capsaicin-pre-treated and vehicle-treated (control) mast cell-rich NC mice. This result suggests the existence of a capsaicin-insensitive (TRPV1-negative) histaminergic pathway. 3) Non-histaminergic PAR-2 pathway: Protease-activated receptor 2 (PAR-2) has been shown to play a role in the itching of atopic dermatitis (AD). The itch evoked by cowhage (a non-histaminergic pruritogen that activates PAR-2) is very similar in characteristics to the itch evoked by conditions such as AD. 4) Non-histaminergic serotonin (5-HT) pathway: 5-HT alone applied to the human skin evokes an itching sensation and has been suggested to be involved in the itching associated with pruritic diseases, such as polycythemia vera and cholestasis.
itch; TRPV1; histamine; PAR-2; serotonin
It has been demonstrated that N-ethyl-lidocaine (QX-314) can target the transient receptor protein vanilloid 1 (TRPV1) nociceptors when coadministered with capsaicin, resulting in a selective block of the nociceptors. Capsaicin is problematic in therapeutic use because it induces firing of nociceptors. The present study aimed to search for substitutes for capsaicin. We also examined the transportability of QX-314 into nociceptive neurons, through the pores of transient receptor potential ankyrin 1 (TRPA1), transient receptor potential melastatin-8 (TRPM8), and TRPV1.
To investigate the effect on TRPA1, injections of a vehicle, allyl isothiocyanate (AITC), QX-314, or AITC/QX-314 were made into the hind paws of rats. The effects of menthol and capsaicin on the opening of TRPM8 and TRPV1 were also examined and compared with the potency of QX-314. To examine inhibition of the antinociceptive effect by capsaicin/ QX-314, capsazepine (50 μg/mL; 10 μL) was injected 30 minutes prior to capsaicin/QX-314 (10 μL) injection. Thermal sensitivity was investigated by the Hargreaves method. 5(6)-carboxyfluorescein (FAM)-conjugated QX-314 was used as a tracer to examine how many and which kind of dorsal root ganglia accumulate this molecule. QX-314-FAM, capsaicin/QX-314-FAM, AITC/QX-314-FAM, and menthol/QX-314-FAM were injected into the paw. Two weeks after injections, dorsal root ganglia were removed and sectioned with a cryostat.
The capsaicin/QX-314 group induced longer withdrawal-response latency at 60 to 300 minutes after injection than the control. Both menthol only and menthol/QX-314 injections showed analgesia 10 to 60 minutes after injection. No significant difference was seen between the capsazepine/capsaicin/QX-314 group and the vehicle group. The fluorescence in small- and medium-sized neurons was conspicuous in only the dorsal root ganglia injected with capsaicin/ QX-314-FAM.
These results indicate that TRPA1 and TRPM8 are ineffective in the transport of QX-314 compared with TRPV1.
anesthetics; capsaicin; AITC; menthol; capsazepine; behavioral tests
Cancer stem cells (CSCs) within squamous cell carcinomas (SCCs) are hypothesized to contribute to chemotherapy and radiation resistance and represent potentially useful pharmacologic targets. Hallmarks of the stem cell phenotype that may contribute to therapy resistance of CSCs include quiescence, evasion of apoptosis, resistance to DNA damage, and expression of drug transporter pumps. A variety of CSC populations within SCCs of the head and neck and esophagus have been defined tentatively, based on diverse surface markers and functional assays. Stem-like self-renewal and differentiation capacities of these SCC subpopulations are supported by sphere formation and clonogenicity assays in vitro as well as limiting dilution studies in xenograft models. Early evidence supports a role for SCC CSCs in intrinsic therapy resistance, while detailed mechanisms by which these subpopulations evade treatment remain to be defined. Development of novel SCC therapies will be aided by pursuing such mechanisms as well as refining current definitions for CSCs and clarifying their relevance to hierarchical versus dynamic models of stemness.
cancer stem cells; drug resistance; squamous cell carcinoma
This protocol describes the isolation and characterization of mouse and human esophageal epithelial cells and the application of 3D organotypic culture (OTC), a form of tissue engineering. This model system permits the interrogation of mechanisms underlying epithelial-stromal interactions. We provide guidelines for isolating and cultivating several sources of epithelial cells and fibroblasts, as well as genetic manipulation of these cell types, as a prelude to their integration into OTC. The protocol includes a number of important applications, including histology, immunohistochemistry/immunofluorescence, genetic modification of epithelial cells and fibroblasts with retroviral and lentiviral vectors for overexpression of genes or RNA interference strategies, confocal imaging, laser capture microdissection, RNA microarrays of individual cellular compartments and protein-based assays. The OTC (3D) culture protocol takes 15 d to perform.
In photodynamic diagnosis, 5-aminolevulinic acid (5-ALA) is widely used for the fluorescence-guided resection of malignant brain tumors, where 5-ALA is converted to protoporphyrin IX, which exhibits strong fluorescence. Little is known, however, about the detailed molecular mechanisms underlying 5-ALA–induced fluorescence. To resolve this issue, we analyzed transcriptome profiles for the genes encoding enzymes, transporters, and a transcription factor involved in the porphyrin-biosynthesis pathway. By quantitative real-time (qRT)-PCR, we measured the mRNA levels of those genes in a total of 20 tumor samples that had been surgically resected from brain tumor patients at the Department of Neurosurgery of Osaka Medical College from 2008 to 2009. We selected 10 tumor samples with no 5-ALA–induced fluorescence, among which 2 were glioblastomas and 8 were metastatic brain tumors. Another 10 tumor samples were selected with strong fluorescence, among which 7 were glioblastomas and 3 were metastatic brain tumors. The qRT-PCR analysis study of these latter 10 samples revealed predominantly high levels of the mRNA of the coproporphyrinogen oxidase (CPOX) gene. The high mRNA level of CPOX expression was significantly well correlated with the phenotype of strong 5-ALA–induced fluorescence (P = .0003). These findings were further confirmed by immunohistochemical studies with a CPOX-specific antibody. It is concluded that induction of CPOX gene expression is one of the key molecular mechanisms underlying the 5-ALA–induced fluorescence of malignant brain tumors. The induction mechanism for the CPOX gene in brain tumors remains to be elucidated.
coproporphyrinogen oxidase; malignant glioma; metastatic brain tumor; photodynamic diagnosis
Zinc finger E-box binding (ZEB) proteins ZEB1 and ZEB2 are transcription factors essential in transforming growth factor (TGF)-β-mediated senescence, epithelial to mesenchymal transition (EMT) and cancer stem cell function. ZEBs are negatively regulated by members of the miR-200 microRNA family, but precisely how tumor cells expressing ZEBs emerge during invasive growth remains unknown. Here we report that NOTCH3-mediated signaling prevents expansion of a unique subset of ZEB-expressing cells. ZEB expression was associated with the lack of cellular capability of undergoing NOTCH3-mediated squamous differentiation in human esophageal cells. Genetic inhibition of the Notch-mediated transcriptional activity by dominant-negative Mastermind-like1 (DNMAML1) prevented squamous differentiation and induction of Notch target genes including NOTCH3. Moreover, DNMAML1 enriched EMT competent cells exhibited robust upregulation of ZEBs, downregulation of the miR-200 family, and enhanced anchorage independent growth and tumor formation in nude mice. RNA interference (RNAi) experiments suggested the involvement of ZEBs in anchorage independent colony formation, invasion and TGF-β-mediated EMT. Invasive growth and impaired squamous differentiation was recapitulated upon Notch inhibition by DNMAML1 in organotypic 3D culture, a form of human tissue engineering. Together, our findings indicate that NOTCH3 is a key factor limiting the expansion of ZEB-expressing cells, providing novel mechanistic insights into the role of Notch signaling in the cell fate regulation and disease progression of squamous esophageal cancers.
Notch; EMT; squamous cell differentiation; ZEB1; miR-200
Squamous cell cancers account for more than half of all human cancers, and esophageal cancer is the sixth leading cause of cancer death worldwide. The majority of esophageal squamous cell carcinomas have identifiable p53 mutations, yet the same p53 mutations are found at comparable frequencies in pre-cancerous dysplasia, indicating that transformation requires additional somatic changes yet to be defined. Here we show that the zinc finger transcription factor KLF5 transactivates NOTCH1 in the context of p53 mutation or loss. KLF5 loss limited NOTCH1 activity and was sufficient on its own to transform primary human keratinocytes harboring mutant p53, leading to formation of invasive tumors. Restoration of NOTCH1 blocked transformation of KLF5-deficient and p53 mutant keratinocytes. While human dysplastic epithelia accumulated KLF5, KLF5 expression was lost concurrently with NOTCH1 in squamous cell cancers. Taken together, these results define KLF5 loss as a critical event in squamous cell transformation and invasion. Our findings suggest that KLF5 may be a useful diagnostic and therapeutic target in esophageal squamous carcinomas and possibly more generally in other cancers associated with p53 loss-of-function.
KLF5; p53; NOTCH1; squamous cell cancer; esophageal cancer
Esophageal squamous cell carcinoma (ESCC) is one of the most aggressive forms of squamous cell carcinomas. Common genetic lesions in ESCC include p53 mutations and EGFR overexpression, both of which have been implicated in negative regulation of Notch signaling. In addition, cyclin D1 is overexpressed in ESCC and can be activated via EGFR, Notch and Wnt signaling. To elucidate how these genetic lesions may interact during the development and progression of ESCC, we tested a panel of genetically engineered human esophageal cells (keratinocytes) in organotypic 3D culture (OTC), a form of human tissue engineering. Notch signaling was suppressed in culture and mice by dominant negative Mastermind-like1 (DNMAML1), a genetic pan-Notch inhibitor. DNMAML1 mice were subjected to 4-Nitroquinoline 1-oxide-induced oral-esophageal carcinogenesis. Highly invasive characteristics of primary human ESCC were recapitulated in OTC as well as DNMAML1 mice. In OTC, cyclin D1 overexpression induced squamous hyperplasia. Concurrent EGFR overexpression and mutant p53 resulted in transformation and invasive growth. Interestingly, cell proliferation appeared to be regulated differentially between those committed to squamous-cell differentiation and those invading into the stroma. Invasive cells exhibited Notch-independent activation of cyclin D1 and Wnt signaling. Within the oral-esophageal squamous epithelia, Notch signaling regulated squamous-cell differentiation to maintain epithelial integrity, and thus may act as a tumor suppressor by preventing the development of a tumor-promoting inflammatory microenvironment.
Esophageal squamous cell carcinoma; organotypic 3D culture; EGFR; P53; cyclin D1; Wnt; Notch; squamous-cell differentiation; invasion; 4-Nitroquinoline 1-oxide
The authors present a novel method of the recapping hemilaminoplasty in a retrospective study of patients with spinal surgical disorders. This report describes the surgical technique and the results of hemilaminoplasty using an ultrasonic bone curette. The aim of this study was to examine the safety and effectiveness of the hemilaminoplasty technique with ultrasonic bone curette.
Between April 2003 and July 2011, 33 patients with various spinal diseases (17 spinal tumors, 5 dural arteriovenous fistulas, 3 syringomyelia, 2 sacral perineural cysts, and 2 arachnoid cysts) were treated microsurgically by using an ultrasonic bone curette with scalpel blade and lightweight handpiece. The ultrasonic bone curette was used for division of lamina. After resection of the lesion, the excised lamina was replaced exactly in situ to its original anatomic position with a titanium plate and screw. Additional fusion technique was not required and the device was easy to handle. All patients were observed both neurologically and radiologically by dynamic plain radiographs and computed tomography (CT) scan.
The operation was performed successfully and there were no instrument-related complications such as dural laceration, nerve root injury, and vessels injury. The mean number of resected and restored lamina was 1.7. CT confirmed primary bone fusion in all patients by 12 months after surgery.
The ultrasonic bone curette is a useful instrument for recapping hemilaminoplasty in various spinal surgeries. This method allows anatomical reconstruction of the excised bone to preserve the posterior surrounding tissues.
Recapping hemilaminoplasty; spinal surgery; ultrasonic bone curette
The procedure of catheter ablation for the treatment of drug resistant atrial fibrillation (AF) has evolved but still relies on lesion sets intended to isolate areas of focal firing, mainly the myocardial sleeves of the pulmonary veins (PVs), from the rest of the atria. However the success rates for this procedure have varied inversely with the type of AF. At best success rates have been 20 to 30% below that of other catheter ablation procedures for Wolff-Parkinson-White syndrome, atrioventricular junctional re-entrant tachycardia and atrial flutter. Basic and clinical evidence has emerged suggesting a critical role of the ganglionated plexi (GP) at the PV-atrial junctions in the initiation and maintenance of the focal form of AF. At present the highest success rates have been obtained with the combination of PV isolation and GP ablation both as catheter ablation or minimally invasive surgical procedures. Various lines of evidence from earlier and more recent reports provide that both neurally based and myocardially based forms of AF can separately dominate or coexist within the context of atrial remodeling. Future studies are focusing on non-pharmacological, non-ablative approaches for the prevention and treatment of AF in order to avoid the substantive complications of both these regimens.
Human squamous cell cancers are the most common epithelially derived malignancies. One example is esophageal squamous cell carcinoma (ESCC), which is associated with a high mortality rate (1) that is related to a propensity for invasion and metastasis (2). Here we report that periostin, a highly expressed cell adhesion molecule, is a key component of a novel tumor invasive signature obtained from an organotypic culture model of engineered ESCC. This tumor invasive signature classifies with human ESCC microarrays, underscoring its utility in human cancer. Genetic modulation of periostin promotes tumor cell migration and invasion as revealed in gain of and loss of function experiments. Inhibition of EGFR signaling and restoration of wild-type p53 function were each found to attenuate periostin, suggesting interdependence of two common genetic alterations with periostin function. Collectively, our studies reveal periostin as an important mediator of ESCC tumor invasion and they indicate that organotypic (3D) culture can offer an important tool to discover novel biologic effectors in cancer.
tumor microenvironment; periostin; EGFR; p53
Background & Aims
The Notch receptor family regulates cell fate through cell-cell communication. CSL (CBF-1/RBP-jκ, Su(H), Lag-1) drives canonical Notch-mediated gene transcription during cell lineage specification, differentiation and proliferation in the hematopoietic system, the intestine, the pancreas and the skin. However, the functional roles of Notch in esophageal squamous epithelial biology remain unknown.
Normal esophageal keratinocytes were stimulated with calcium chloride to induce terminal differentiation. The squamous epithelia were reconstituted in organotypic three-dimensional culture, a form of human tissue engineering. Notch was inhibited in culture with a γ-secretase inhibitor or dominant negative mastermind-like1 (DNMAML1). The roles of Notch receptors were evaluated by in vitro gain-of-function and loss-of-function experiments. Additionally, DNMAML1 was targeted to the mouse esophagus by cytokeratin K14 promoter-driven Cre (K14Cre) recombination of Lox-STOP-Lox-DNMAML1. Notch-regulated gene expression was determined by reporter transfection, chromatin immunoprecipitation (ChIP) assays, quantitative reverse-transcription polymerase chain reactions (RT-PCR), Western blotting, immunofluorescence and immunohistochemistry.
NOTCH1 (N1) was activated at the onset of squamous differentiation in the esophagus. Intracellular domain of N1 (ICN1) directly activated NOTCH3 (N3) transcription, inducing HES5 and early differentiation markers such as involucrin (IVL) and cytokeratin CK13 in a CSL-dependent fashion. N3 enhanced ICN1 activity and was required for squamous differentiation. Loss of Notch signaling in K14Cre;DNMAML1 mice perturbed esophageal squamous differentiation and resulted in N3 loss and basal cell hyperplasia.
Notch signaling is important for esophageal epithelial homeostasis. In particular, the crosstalk of N3 with N1 during differentiation provides novel, mechanistic insights into Notch signaling and squamous epithelial biology.
NOTCH1; NOTCH3; esophageal epithelium; squamous differentiation
Cyclin D1 elicits transcriptional effects through inactivation of the retinoblastoma protein and direct association with transcriptional regulators. The current work reveals a molecular relationship between cyclin D1/CDK4 kinase and protein arginine methyltransferase 5 (PRMT5), an enzyme associated with histone methylation and transcriptional repression. Primary tumors of a mouse lymphoma model exhibit increased PRMT5 methyltransferase activity and histone arginine methylation. Analyses demonstrate that MEP50, a PRMT5 co-regulatory factor, is a CDK4 substrate, and phosphorylation increases PRMT5/MEP50 activity. Increased PRMT5 activity mediates key events associated with cyclin D1-dependent neoplastic growth including CUL4 repression, CDT1 overexpression, and DNA re-replication. Importantly, human cancers harboring mutations in Fbx4, the cyclin D1 E3 ligase, exhibit nuclear cyclin D1 accumulation and increased PRMT5 activity.
Cyclin D1; CDK4; CUL4; CDT1; PRMT5; MEP50; Arginine Methylation
Insulin-like growth factor-binding protein (IGFBP)-3 is overexpressed frequently in esophageal squamous cell carcinoma. Yet, the role of IGFBP3 in esophageal tumor biology remains to be elucidated. We find that IGFBP3 facilitates transforming growth factor (TGF)-β1-mediated epithelial-to-mesenchymal transition (EMT) in transformed human esophageal epithelial cells, EPC2–hTERT–EGFR–p53R175H. In organotypic 3D culture, a form of human tissue engineering, laser-capture microdissection revealed concurrent upregulation of TGF-β target genes, IGFBP3 and EMT-related genes in the cells invading into the stromal compartment. IGFBP3 enhanced TGF-β1-mediated EMT as well as transcription factors essential in EMT by allowing persistent SMAD2 and SMAD3 phosphorylation. TGF-β1-mediated EMT and cell invasion were enhanced by ectopically expressed IGFBP3 and suppressed by RNA interference directed against IGFBP3. The IGFBP3 knockdown effect was rescued by IGFBP3I56G/L80G/L81G, a mutant IGFBP3 lacking an insulin-like growth factor (IGF)-binding capacity. Thus, IGFBP3 can regulate TGF-β1-mediated EMT and cell invasion in an IGF or insulin-like growth factor 1 receptor-independent manner. IGFBP3I56G/L80G/L81G also promoted EMT in vivo in a Ras-transformed human esophageal cell line T-TeRas upon xenograft transplantation in nude mice. In aggregate, IGFBP3 may have a novel IGF-binding independent biological function in regulation of TGF-β1-mediated EMT and cell invasion.
Transforming growth factor (TGF)-β is a potent inducer of epithelial to mesenchymal transition (EMT). However, it remains elusive as to which molecular mechanisms determine the cellular capacity to undergo EMT in response to TGF-β. We have found that both epidermal growth factor receptor (EGFR) overexpression and mutant p53 tumor suppressor genes contribute to enrichment of an EMT-competent cellular subpopulation amongst telomerase-immortalized human esophageal epithelial cells during malignant transformation. EGFR overexpression triggers oncogene-induced senescence, accompanied by induction of cyclin dependent kinase inhibitors p15INK4B, p16INK4A and p21. Interestingly, a subpopulation of cells emerges by negating senescence without loss of EGFR overexpression. Such cell populations express increased levels of zinc finger E-box binding (ZEB) transcription factors ZEB1 and ZEB2, and undergo EMT upon TGF-β stimulation. Enrichment of EMT-competent cells was more evident in the presence of p53 mutation, which diminished EGFR-induced senescence. RNA interference directed against ZEB resulted in induction of p15INK4B and p16INK4A, reactivating the EGFR-dependent senescence program. Importantly, TGF-β-mediated EMT did not take place when cellular senescence programs were activated by either ZEB knockdown or activation of wild-type p53 function. Thus, senescence checkpoint functions activated by EGFR and p53 may be evaded through the induction of ZEB, thereby allowing expansion of an EMT-competent unique cellular subpopulation, providing novel mechanistic insights into the role of ZEB in esophageal carcinogenesis.
EGFR; EMT; senescence; ZEB1; ZEB2
Hypoxia-inducible factors (HIFs), in particular HIF-1α, have been implicated in tumor biology. However, HIF target genes in the esophageal tumor microenvironment remain elusive. Gene expression profiling was performed upon hypoxia-exposed non-transformed immortalized human esophageal epithelial cells, EPC2-hTERT, and comparing with a gene signature of esophageal squamous cell carcinoma (ESCC). In addition to known HIF-1α target genes such as carbonic anhydrase 9, insulin-like growth factor binding protein-3 (IGFBP3) and cyclooxygenase (COX)-2, prostaglandin E synthase (PTGES) was identified as a novel target gene among the commonly upregulated genes in ESCC as well as the cells exposed to hypoxia. The PTGES induction was augmented upon stabilization of HIF-1α by hypoxia or cobalt chloride under normoxic conditions and suppressed by dominant-negative HIF-1α. Whereas PTGES messenger RNA (mRNA) was negatively regulated by normoxia, PTGES protein remained stable upon reoxygenation. Prostaglandin E2 (PGE2) biosynthesis was documented in transformed human esophageal cells by ectopic expression of PTGES as well as RNA interference directed against PTGES. Moreover, hypoxia stimulated PGE2 production in a HIF-1α-dependent manner. In ESCC, PTGES was overexpressed frequently at the mRNA and protein levels. Finally, COX-2 and PTGES were colocalized in primary tumors along with HIF-1α and IGFBP3. Activation of the COX-2–PTGES axis in primary tumors was further corroborated by concomitant upregulation of interleukin-1β and downregulation of hydroxylprostaglandin dehydrogenase. Thus, PTGES is a novel HIF-1α target gene, involved in prostaglandin E biosynthesis in the esophageal tumor hypoxic microenvironment, and this has implications in diverse tumors types, especially of squamous origin.
IGF and EGF regulate various physiological and pathological processes. IGF binding protein (IGFBP)-3 regulates cell proliferation in IGF-dependent and -independent fashions. Recently, we identified IGFBP-3 as a novel EGF receptor (EGFR) downstream target molecule in primary and immortalized human esophageal epithelial cells, suggesting an interplay between the EGF and IGF signaling pathways. However, the regulatory mechanisms for IGFBP-3 expression and its functional role in esophageal cell proliferation remain to be elucidated. Herein, we report that IGFBP-3 mRNA and protein were induced upon growth factor deprivation in primary and immortalized human esophageal cells through mechanisms requiring p53-independent de novo mRNA transcription and protein synthesis. This occurred in the face of the activated phosphatidylinositol 3-OH-kinase (PI3K)/mammalian target of rapamycin (mTOR) pathway. Secreted IGFBP-3 neutralized IGFs and prevented IGF-I receptor (IGF-IR) activation. In contrast, EGF suppressed IGFBP-3 mRNA and protein expression through activation of MAPK in an EGFR-tyrosine kinase-dependent manner to restore the cellular response to IGF-I. When stably overexpressed, wild-type IGFBP-3 but not I56G/L80G/L81G (GGG) mutant IGFBP-3, which has a reduced affinity to IGFs, prevented IGF-I from activating IGF-IR and Akt as well as stimulating cell proliferation. However, unlike other cell types where IGFBP-3 exerts antiproliferative effects, neither wild-type nor GGG mutant IGFBP-3 alone affected cell proliferation or EGFR activity. These results indicate that IGF signaling is subject to negative regulation through IGFBP-3 and positive regulation by EGF, the latter of which suppresses IGFBP-3. This provides a platform for understanding the novel cross talk between EGF- and IGF-mediated pathways.
insulin-like growth factor binding protein-3; epidermal growth factor receptor; mammalian target of rapamycin; esophageal epithelial cells
In epithelial cells, E-cadherin plays a key role in cell-cell adhesion, and loss of E-cadherin is a hallmark of tumor progression fostering cancer cell invasion and metastasis. To examine E-cadherin loss in squamous cell cancers, we used primary human esophageal epithelial cells (keratinocytes) as a platform and retrovirally transduced wild-type and dominant-negative forms of E-cadherin into these cells. We found decreased cell adhesion in the cells expressing dominant-negative E-cadherin, thereby resulting in enhanced migration and invasion. To analyze which molecular pathway(s) may modulate these changes, we conducted microarray analysis and found up-regulation of transforming growth factor β receptor II (TβRII) in the wild-type E-cadherin-overexpressing cells, which was confirmed by real-time PCR and Western blot analyses. To investigate the in vivo relevance of this finding, we analyzed tissue microarrays of paired esophageal squamous cell carcinomas and adjacent normal esophagus, and we could show a coordinated loss of E-cadherin and TβRII in ~80% of tumors. To determine if there may be an E-cadherin-dependent regulation of TβRII, we show the physical interaction of E-cadherin with TβRII and that this is mediated through the extracellular domains of E-cadherin and TβRII, respectively. In addition, TβRI is recruited to this complex. When placed in the context of three-dimensional cell culture, which reflects the physiologic microenvironment, TβRII-mediated cell signaling is dependent upon intact E-cadherin function. Our results, which suggest that E-cadherin regulates TβRII function, have important implications for epithelial carcinogenesis characterized through the frequent occurrence of E-cadherin and TβRII loss.
Insulin-like growth factor binding protein (IGFBP)-3 exerts either proapoptotic or growth stimulatory effects depending upon the cellular context. IGFBP-3 is overexpressed frequently in esophageal cancer. Yet, the role of IGFBP-3 in esophageal tumor biology remains elusive. To delineate the functional consequences of IGFBP-3 overexpression, we stably transduced Ha-RasV12-transformed human esophageal cells with either wild-type or mutant IGFBP-3, the latter incapable of binding Insulin-like growth factor (IGFs) as a result of substitution of amino-terminal Ile56, Leu80, and Leu81 residues with Glycine residues. Wild-type, but not mutant, IGFBP-3 prevented IGF-I from activating the IGF-1 receptor and AKT, and suppressed anchorage-independent cell growth. When xenografted in nude mice, in vivo bioluminescence imaging demonstrated that wild-type, but not mutant IGFBP-3, abrogated tumor formation by the Ras-transformed cells with concurrent induction of apoptosis, implying a prosurvival effect of IGF in cancer cell adaptation to the microenvironment. Moreover, there was more aggressive tumor growth by mutant IGFBP-3 overexpressing cells than control cell tumors, without detectable caspase-3 cleavage in tumor tissues, indicating an IGF-independent growth stimulatory effect of mutant IGFBP-3. In aggregate, these data suggest that IGFBP-3 contributes to esophageal tumor development and progression through IGF-dependent and independent mechanisms.
IGFBP-3; IGF; Ras; esophageal cancer; in vivo bioluminescence
The cyclin D1 oncogene is frequently amplified/overexpressed in oral squamous cell carcinomas. Mice with overexpression of cyclin D1 targeted to the stratified squamous epithelia of the tongue, esophagus and forestomach develop a phenotype of epithelial dysplasia at these sites. In this study, we examined the effect cyclin D1 overexpression on susceptibility of mice to carcinogen-induced tumorigenesis, using 4-nitroquinoline-1-oxide (4NQO), an established potent oral carcinogen in mice. Cyclin D1 overexpressing mice and non-transgenic littermates were administered 4NQO (20 ppm or 50 ppm in the drinking water) for 8 weeks and monitored for an additional 16 weeks. Histopathological analyses of the tongue revealed significantly higher severity of dysplasia in the cyclin D1 overexpression mice, compared with non-transgenic controls and with untreated controls. Moreover, only the cyclin D1 overexpression mice developed neoplastic lesions in the oro-esophageal epithelia. Examination of the dysplastic and neoplastic lesions reveled abnormal proliferation. Our findings suggest that cyclin D1 overexpression enhances susceptibility to carcinogen-induced oral tumorigenesis. These results underscore the importance of cyclin D1 in the process of oral neoplastic development. Further, they emphasize the value of this transgenic model to study the pathogenesis of oral precancer and cancer and establish it as a model system to test candidate agents for chemoprevention of upper aero-digestive cancer.
Mouth neoplasms/genetics; Cyclin D1/genetics; Disease Models; Animal Mice; Transgenic
Accumulating evidence indicates that ATP-binding cassette (ABC) transporter ABCG2 plays a key role in regulating the cellular accumulation of porphyrin derivatives in cancer cells and thereby affects the efficacy of photodynamic therapy and photodynamic diagnosis. The activity of porphyrin efflux can be affected by genetic polymorphisms in the ABCG2 gene. On the other hand, Nrf2, an NF-E2-related transcription factor, has been shown to be involved in oxidative stress-mediated induction of the ABCG2 gene. Since patients have demonstrated individual differences in their response to photodynamic therapy, transcriptional activation and/or genetic polymorphisms of the ABCG2 gene in cancer cells may affect patients' responses to photodynamic therapy. Protein kinase inhibitors, including imatinib mesylate and gefitinib, are suggested to potentially enhance the efficacy of photodynamic therapy by blocking ABCG2-mediated porphyrin efflux from cancer cells. This review article provides an overview on the role of human ABC transporter ABCG2 in photodynamic therapy and photodynamic diagnosis.