Rap1 stabilizes beta-catenin and enhances beta-catenin-dependent transcription and invasion in squamous cell carcinoma of the head and neck

Aberrant expression of VASP serves as a potential prognostic biomarker and therapeutic target for oral squamous cell carcinoma

OBJECTIVE

To address the molecular markers linked to the development and progression of oral squamous cell carcinoma (OSCC), we sought to analyze the expression of vasodilator-stimulated phosphoproteins (VASP) in OSCC samples.

STUDY DESIGN

This study used 51 OSCC patients and The Cancer Genome Atlas-Head and Neck Squamous Cell Carcinoma (TCGA-HNSC) dataset to analyze VASP expression. The association between VASP mRNA expression and HNSCC clinicopathological features, tumor infiltration, functional roles, and gene co-expression of VASP also were evaluated.

RESULTS

Our study observed increased VASP mRNA expression in OSCC tumor tissues compared to normal tissues, supported by TCGA-HNSC dataset analysis. Elevated VASP levels correlated with advanced tumor stage, higher grade, nodal metastasis, and poor survival, indicating its potential as a prognostic marker. Protein analysis and immunohistochemistry confirmed these findings, and in silico analysis revealed VASP involvement in key cancer-related processes and its correlation with IL8, RAP1A expression, and tumor infiltration levels.

CONCLUSIONS

In conclusion, VASP emerges as a promising diagnostic and prognostic marker for OSCC within HNSCC, emphasizing the importance of exploring its regulatory mechanisms and therapeutic applications. The revealed pathways present avenues for targeted treatment in OSCC. Despite limitations, this study provides valuable insights with potential implications for improving patient outcomes.

Tideglusib enhances odontogenic differentiation in human dental pulp stem cells in vitro

AIM

Tideglusib is a small molecule agonist of the canonical Wnt pathway. The present study investigated the influence of Tideglusib on human dental pulp stem cell (hDPSC) proliferation, apoptosis, migration and odonto/osteogenic differentiation.

METHODOLOGY

hDPSCs were treated with 50, 100 nM or 200 nM Tideglusib. β-catenin accumulation was detected by immunofluorescence staining. Colony-forming unit ability was assessed by staining with Coomassie blue. Cell cycle progression and cell apoptosis were investigated using flow cytometry. Cell migration was examined using an in vitro wound-healing assay. Osteogenic differentiation was examined using alkaline phosphatase (ALP) staining, alizarin red S staining and osteogenic-related gene expression. The gene expression profile was examined using a high-throughput RNA sequencing technique. All experiments were repeated using cells derived from at least four different donors (n = 4). The Mann-Whitney U-test was used to identify significant differences between two independent group comparisons. For three or more group comparisons, statistical differences were assessed using the Kruskal-Wallis test followed by pairwise comparison. The significance level was set at 5% (p < .05).

RESULTS

Tideglusib activated the Wnt signalling pathway in hDPSCs as demonstrated by an increase in cytoplasmic β-catenin accumulation and nuclear translocation. Tideglusib did not affect hDPSC proliferation, cell cycle progression, cell apoptosis or cell migration. In contrast, 50 and 100 nM Tideglusib significantly enhanced mineralization and osteogenic marker gene expression (RUNX2, ALP, BMP2 and DSPP; p < .05).

CONCLUSIONS

Tideglusib enhanced the odonto/osteogenic differentiation of hDPSCs. Therefore, incorporating this bioactive molecule in a pulp-capping material could be a promising strategy to promote dentine repair.

Signaling pathways and their potential therapeutic utility in esophageal squamous cell carcinoma

Esophageal cancer is a complex gastrointestinal malignancy with an extremely poor outcome. Approximately 80% of cases of this malignancy in Asian countries including India are of squamous cell origin, termed Esophageal Squamous Cell Carcinoma (ESCC).The five-year survival rate in ESCC patients is less than 20%. Neo-adjuvant chemo-radiotherapy (NACRT) followed by surgical resection remains the major therapeutic strategy for patients with operable ESCC. However, resistance to NACRT and local recurrence after initial treatment are the leading cause of dismal outcomes in these patients. Therefore, an alternative strategy to promote response to the therapy and reduce the post-operative disease recurrence is highly needed. At the molecular level, wide variations have been observed in tumor characteristics among different populations, nevertheless, several common molecular features have been identified which orchestrate disease progression and clinical outcome in the malignancy. Therefore, determination of candidate molecular pathways for targeted therapy remains the mainstream idea of focus in ESCC research. In this review, we have discussed the key signaling pathways associated with ESCC, i.e., Notch, Wnt, and Nrf2 pathways, and their crosstalk during disease progression. We further discuss the recent developments of novel agents to target these pathways in the context of targeted cancer therapy. In-depth research of the signaling pathways, gene signatures, and a combinatorial approach may help in discovering targeted therapy for ESCC.

Ras Family of Small GTPases in CRC: New Perspectives for Overcoming Drug Resistance

Colorectal cancer remains among the cancers with the highest incidence, prevalence, and mortality worldwide. Although the development of targeted therapies against the EGFR and VEGFR membrane receptors has considerably improved survival in these patients, the appearance of resistance means that their success is still limited. Overactivation of several members of the Ras-GTPase family is one of the main actors in both tumour progression and the lack of response to cytotoxic and targeted therapies. This fact has led many resources to be devoted over the last decades to the development of targeted therapies against these proteins. However, they have not been as successful as expected in their move to the clinic so far. In this review, we will analyse the role of these Ras-GTPases in the emergence and development of colorectal cancer and their relationship with resistance to targeted therapies, as well as the status and new advances in the design of targeted therapies against these proteins and their possible clinical implications.

SmgGDS: An Emerging Master Regulator of Prenylation and Trafficking by Small GTPases in the Ras and Rho Families

Newly synthesized small GTPases in the Ras and Rho families are prenylated by cytosolic prenyltransferases and then escorted by chaperones to membranes, the nucleus, and other sites where the GTPases participate in a variety of signaling cascades. Understanding how prenylation and trafficking are regulated will help define new therapeutic strategies for cancer and other disorders involving abnormal signaling by these small GTPases. A growing body of evidence indicates that splice variants of SmgGDS (gene name RAP1GDS1) are major regulators of the prenylation, post-prenylation processing, and trafficking of Ras and Rho family members. SmgGDS-607 binds pre-prenylated small GTPases, while SmgGDS-558 binds prenylated small GTPases. This review discusses the history of SmgGDS research and explains our current understanding of how SmgGDS splice variants regulate the prenylation and trafficking of small GTPases. We discuss recent evidence that mutant forms of RabL3 and Rab22a control the release of small GTPases from SmgGDS, and review the inhibitory actions of DiRas1, which competitively blocks the binding of other small GTPases to SmgGDS. We conclude with a discussion of current strategies for therapeutic targeting of SmgGDS in cancer involving splice-switching oligonucleotides and peptide inhibitors.

The Role of Ras-Associated Protein 1 (Rap1) in Cancer: Bad Actor or Good Player?

Metastasis is known as the most life-threatening event in cancer patients. In principle, the immune system can prevent tumor development. However, dysfunctional T cells may fail to eliminate the tumor cells effectively and provide additional survival advantages for tumor proliferation and metastasis. Constitutive activation of Ras-associated protein1 (Rap1) has not only led to T cell anergy, but also inhibited autophagy and supported cancer progression through various oncogenic events. Inhibition of Rap1 activity with its negative regulator, Rap1GAP, impairs tumor progression. However, active Rap1 reduces tumor invasion in some cancers, indicating that the pleiotropic effects of Rap1 signaling in cancers could be cancer-specific. All in all, targeting Rap1 signaling and its regulators could potentially control carcinogenesis, metastasis, chemoresistance and immune evasion. Rap1GAP could be a promising therapeutic target in combating cancer.

The Mystery of Rap1 Suppression of Oncogenic Ras

Decades ago, Rap1, a small GTPase very similar to Ras, was observed to suppress oncogenic Ras phenotype, reverting its transformation. The proposed reason, persisting since, has been competition between Ras and Rap1 for a common target. Yet, none was found. There was also Rap1's puzzling suppression of Raf-1 versus activation of BRAF. Reemerging interest in Rap1 envisages capturing its Ras suppression action by inhibitors. Here, we review the literature and resolve the enigma. In vivo oncogenic Ras exists in isoform-distinct nanoclusters. The presence of Rap1 within the nanoclusters reduces the number of the clustered oncogenic Ras molecules, thus suppressing Raf-1 activation and mitogen-activated protein kinase (MAPK) signaling. Nanoclustering suggests that Rap1 suppression is Ras isoform dependent. Altogether, a potent Rap1-like inhibitor appears unlikely.

The Significance of the Dysregulation of Canonical Wnt Signaling in Head and Neck Squamous Cell Carcinomas

The knowledge about the molecular alterations which are found in head and neck squamous cell carcinomas (HNSCC) has much increased in recent years. However, we are still awaiting the translation of this knowledge to new diagnostic and therapeutic options. Among the many molecular changes that are detected in head and neck cancer, the abnormalities in several signaling pathways, which regulate cell proliferation, cell death and stemness, seem to be especially promising with regard to the development of targeted therapies. Canonical Wnt signaling is a pathway engaged in the formation of head and neck tissues, however it is not active in adult somatic mucosal cells. The aim of this review paper is to bring together significant data related to the current knowledge on the mechanisms and functional significance of the dysregulation of the Wnt/β-catenin pathway in head and neck tumors. Research evidence related to the role of Wnt signaling activation in the stimulation of cell proliferation, migration and inhibition of apoptosis in HNSCC is presented. Moreover, its role in promoting stemness traits in head and neck cancer stem-like cells is described. Evidence corroborating the hypothesis that the Wnt signaling pathway is a very promising target of novel therapeutic interventions in HNSCC is also discussed.

4E-BP1Thr46 Phosphorylation Association with Poor Prognosis in Quantitative Phosphoproteomics of Portal Vein Tumor Thrombus Revealed that 4E-BP1Thr46 Phosphorylation is Associated with Poor Prognosis in HCC

Purpose

Early formation of portal vein tumor thrombosis (PVTT) is a key characteristic of hepatocellular carcinoma (HCC) metastasis, but to date, the aetiology of PVTT in HCC metastasis is largely unknown. We aim to find highly sensitive and specific biomarkers for the prediction of HCC prognosis.

Patients and methods

We used isobaric tags for relative and absolute quantitation (iTRAQ) based quantitative phosphoproteomics approach to investigate the molecular signatures of the HCC with PVTT in primary HCC tissues, surrounding non-cancerous tissues and PVTT tissues. The different proteome profiles in three groups were investigated and might reveal different underlying molecular mechanisms.

Results

In total, we identified 1745 phosphoproteins with 2724 phosphopeptides and 4594 phosphorylation sites in three groups. Among these phosphoproteins, 80 phosphoproteins were dysregulated in PVTT/Pan group, 51 phosphoproteins were dysregulated in HCC/Pan group, and 10 phosphoproteins were dysregulated in PVTT/HCC group. Furthermore, the phosphorylation of 4E-BP1 was elevated in HCC tissues and PVTT tissues in comparison with surrounding non-cancerous tissues,  and the elevated fold change of phosphorylation level was higher than that in expression level of 4E-BP1. The further IHC analysis in acohort of 20 HCC tissues showed that the phosphorylation of 4E-BP1 on Thr46 might be closely related to HCC prognosis.

Conclusion

The high phosphorylation level of 4E-BP1^Thr46 might serve as a biomarker for the diagnosis of early recurrence and metastasis of HCC.

Characterization of TCF4-mediated oncogenic role in cutaneous squamous cell carcinoma

The aberrant highly expressed T-cell factor 4 (TCF4) has been determined to be closely connected with carcinogenesis of cutaneous squamous cell carcinoma (cSCC) in previous studies. However, the underlying regulatory network and the potential therapeutic targets of TCF4 in SCC are still not fully understood. In this study, the highly expressed TCF4 was observed in human cSCC cancer compared to the paired adjacent tissues. A431 cell lines with TCF4 RNA silencing were found to be the repressive cell proliferation and invasion as well as the enhanced apoptosis. Furthermore, RNA-Seq was conducted and observed that 147 genes were up-regulated (including 113 coding genes and 34 lncRNA) while 172 genes were down-regulated (including 64 coding genes and 108 lncRNA) in TCF4 silencing compared to blank RNAi and untreated control A431 cells. 18 pathways including steroid, porphyrin, arachidonic acid, and retinol metabolism, as well as the functions associated with angiogenesis, inflammatory response, and cell adhesion were involved in the differentially expressed genes of A431 cells with TCF4 silencing. Finally, ChIP-qPCR of TCF4 and β-catenin were performed and we found that the enrichments of β-catenin were lost on the promoters on top ten down-regulated genes in A431 cells with TCF4 silencing compared to the untreated A431. Additionally, in untreated A431 cells, some genes such as ALDH8A1, DRICH1, and UGT1A5 were observed with high enrichment of TCF4, but without β-catenin, which indicated a Wnt/β-catenin independent way of TCF4 for gene transcriptional regulation. In conclusion, we declared that TCF4 played an important role in tumorigenesis of skin cancer via the aberrant activation of variety of signaling pathways, and could be considered as a potential therapeutic target for cSCC treatment.

SHARPIN Promotes Melanoma Progression via Rap1 Signaling Pathway

SHARPIN, as a tumor-associated gene, is involved in the metastatic process of many kinds of tumors. Herein, we studied the function of Shank-associated RH domain interacting protein (SHARPIN) in melanoma metastasis and the relevant molecular mechanisms. We found that SHARPIN expression was increased in melanoma tissues and activated the process of proliferation, migration, and invasion in vitro and in vivo, resulting in a poor prognosis of the disease. Functional analysis demonstrated that SHARPIN promoted melanoma migration and invasion by regulating Ras-associated protein-1(Rap1) and its downstream pathways, including p38 and JNK/c-Jun. Rap1 activator (8-pCPT-2'-O-Me-cAMP) and inhibitor (ESI-09 and farnesylthiosalicylic acid-amide) treatments could partially rescue invasion and migration of tumor cells. Additionally, SHARPIN expression in cell lines and public datasets also indicated that molecules other than BRAF and N-RAS may contribute to SHARPIN activation. In conclusion, our broad-in-depth work suggests that SHARPIN promotes melanoma development via p38 and JNK/c-Jun pathways through upregulation of Rap1 expression.

Role of miR-337-3p and its target Rap1A in modulating proliferation, invasion, migration and apoptosis of cervical cancer cells

OBJECTIVE

To investigate the role of miR-337-3p targeting Rap1A in modulating proliferation, invasion, migration and apoptosis of cervical cancer cells.

METHODS

The expression levels of miR-337-3p and Rap1A in cervical cancer tissues and normal tissues were evaluated through quantitative Real-time PCR (qRT-PCR) and Western blotting; and correlations of miR-337-3p with clinicopathological characteristics and prognosis of patients were also analyzed. Besides, human cervical cancer cell line HeLa cells were randomly divided into five groups (Mock, NC, miR-337-3p mimic, Rap1A, and miR-337-3p mimic + Rap1A groups). CCK-8 assay was utilized to measure cell proliferation, flow cytometry to evaluate cell apoptosis, and wound-healing and Transwell assays to detect cell migration and invasion.

RESULTS

Cervical cancer tissues presented a significant decrease in miR-337-3p and a remarkable increase in Rap1A protein. Besides, the expression levels of miR-337-3p and Rap1A were closely related to the major clinicopathological characteristics of cervical cancer; and patients with high-miR-337-3p-expression had the higher 5-year survival rate (all p< 0.05). When compared to Mock group, cells in miR-337-3p mimic group were suppressed in proliferation, migration, and invasion, but significantly promoted in apoptosis; meanwhile, cells in the Rap1A group showed changes in a completely opposite trend (all p< 0.05). Moreover, Rap1A can reverse the effect of miR-337-3p mimic on cell proliferation, invasion, migration and apoptosis (all p< 0.05).

CONCLUSION

MiR-337-3p was discovered to be decreased in cervical cancer, and miR-337-3p up-regulation may inhibit the proliferation, migration and invasion and promote the apoptosis of cervical cancer cells via down-regulating Rap1A.

Expression of the guanine nucleotide exchange factor, RAPGEF5, during mouse and human embryogenesis

Rap GTPases mediate fundamental cellular processes, including cell adhesion, migration and intracellular signal transduction. The subcellular activity of these GTPases is regulated by dedicated activators (guanine nucleotide exchange factors, GEFs) and deactivators (GTPase-activating proteins, GAPs). RAPGEF5 is a potent activator of Rap proteins and mutations in RAPGEF5 have been linked to both neurological disorders and congenital heart disease. In the frog model, Xenopus tropicalis, Rapgef5 is a critical regulator of the canonical Wnt signalling pathway and is required for normal gastrulation and correct establishment of the left-right body axis. However, requirements for RAPGEF5 in other developmental contexts, and in mammalian embryogenesis in particular, remain undefined. Here, we describe RAPGEF5 mRNA expression patterns during mouse (E9.5 - E16.5) and human (Carnegie stage 21) development, as an initial step towards better understanding its developmental functions.

The Mechanism of Rap1 Regulates N-cadherin to Control Neuronal Migration

Rap1 and N-cadherin regulate glia-independent translocation of cortical neurons. It remains unclear how Rap1 regulates N-cadherin-mediated neuronal migration. Here, we overexpressed Rap1gap in mouse brains (embryonic day 16) to inactivate Rap1, and observed that neurons did not migrate to the outer layer. We confirmed that Rap1 was involved in the regulation of late neurons in vivo. Rap1gap overexpression and Rap1 suppression in CHO cells decreased the expression of cytoskeletal proteins such as tubulin. Changes in the expression of cell morphology regulators, such as N-cadherin and β-catenin, were also observed. Inhibition of N-cadherin in mouse brains prevented neuronal migration to the outer layer. The morphology of CHO cells was changed after overexpression of Rap1gap. We propose that Rap1 regulates the expression of N-cadherin during embryonic development, which affects β-catenin expression. Beta-catenin in turn regulates cytoskeletal protein expression, ultimately affecting neuronal morphology and migration.

ANXA2Tyr23 and FLNASer2152 phosphorylation associate with poor prognosis in hepatic carcinoma revealed by quantitative phosphoproteomics analysis

Hepatoma is one of the most common malignant tumors, and most patients have very poor prognosis. Early prediction and intervention of the hepatoma recurrence/metastasis are the most effective way to improve the patients' clinical outcomes. Here, we used isobaric tags for relative and absolute quantitation (iTRAQ) based quantitative phospho-proteomics approach to identify biomarkers associated with hepatoma recurrence/metastasis in hepatoma cell lines with increasing metastasis ability. In total, 75 phosphorylated peptides corresponding to 60 phosphoproteins were significantly dysregulated and the participated biological processes of these phosphoproteins were tightly associated with tumor metastasis. Further signaling pathway analysis revealed that key signaling pathways which play crucial roles in cancer metastasis have been significantly over activated in the highly metastatic cells. Furthermore, the phosphorylation of FLNA^Ser2152 and ANXA2^Tyr23 were validated to be significantly up regulated in the high-metastatic cells comparing with the low-metastatic cells. By further investigation the clinical significance of the phosphorylation of FLNA^Ser2152 and ANXA2^Tyr23 in large-scale clinical samples, revealed that the over phosphorylation of FLNA^Ser2152 and ANXA2^Tyr23 were associated with poor prognosis and might be potential prognostic biomarkers for the primary hepatoma. When FLNA^Ser2152 combined with ANXA2^Tyr23, it had a better prognostic value for both OS and TTR.

Wnt signaling dynamics in head and neck squamous cell cancer tumor-stroma interactions

Wnt pathway activation maintains the cancer stem cell (CSC) phenotype and promotes tumor progression, making it an attractive target for anti-cancer therapy. Wnt signaling at the tumor and tumor microenvironment (TME) front have not been investigated in depth in head and neck squamous cell carcinoma (HNSCC). In a cohort of 48 HNSCCs, increased Wnt signaling, including Wnt genes (AXIN2, LGR6, WISP1) and stem cell factors (RET, SOX5, KIT), were associated with a more advanced clinical stage. Key Wnt pathway proteins were most abundant at the cancer epithelial-stromal boundary. To investigate these observations, we generated three pairs of cancer-cancer associated fibroblast (CAF) cell lines derived from the same HNSCC patients. 3D co-culture of cancer spheres and CAFs mimicked these in vivo interactions, and using these we observed increased expression of Wnt genes (eg, WNT3A, WNT7A, WNT16) in both compartments. Of these Wnt ligands, we found Wnt3a, and less consistently Wnt16, activated Wnt signaling in both cancer cells and CAFs. Wnt activation increased CSC characteristics like sphere formation and invasiveness, which was further regulated by the presence of CAFs. Time lapse microscopy also revealed preferential Wnt activation of cancer cells. Wnt inhibitors, OMP-18R5 and OMP-54F28, significantly reduced growth of HNSCC patient-derived xenografts and suppressed Wnt activation at the tumor epithelial-stromal boundary. Taken together, our findings suggest that Wnt signaling is initiated in cancer cells which then activate CAFs, and in turn perpetuate a paracrine signaling loop. This suggests that targeting Wnt signaling in the TME is essential.

Ras and Rap1: A tale of two GTPases

Ras oncoproteins play pivotal roles in both the development and maintenance of many tumor types. Unfortunately, these proteins are difficult to directly target using traditional pharmacological strategies, in part due to their lack of obvious binding pockets or allosteric sites. This obstacle has driven a considerable amount of research into pursuing alternative ways to effectively inhibit Ras, examples of which include inducing mislocalization to prevent Ras maturation and inactivating downstream proteins in Ras-driven signaling pathways. Ras proteins are archetypes of a superfamily of small GTPases that play specific roles in the regulation of many cellular processes, including vesicle trafficking, nuclear transport, cytoskeletal rearrangement, and cell cycle progression. Several other superfamily members have also been linked to the control of normal and cancer cell growth and survival. For example, Rap1 has high sequence similarity to Ras, has overlapping binding partners, and has been demonstrated to both oppose and mimic Ras-driven cancer phenotypes. Rap1 plays an important role in cell adhesion and integrin function in a variety of cell types. Mechanistically, Ras and Rap1 cooperate to initiate and sustain ERK signaling, which is activated in many malignancies and is the target of successful therapeutics. Here we review the role activated Rap1 in ERK signaling and other downstream pathways to promote invasion and cell migration and metastasis in various cancer types.

RAPGEF5 Regulates Nuclear Translocation of β-Catenin

Canonical Wnt signaling coordinates many critical aspects of embryonic development, while dysregulated Wnt signaling contributes to common diseases, including congenital malformations and cancer. The nuclear localization of β-catenin is the defining step in pathway activation. However, despite intensive investigation, the mechanisms regulating β-catenin nuclear transport remain undefined. In a patient with congenital heart disease and heterotaxy, a disorder of left-right patterning, we previously identified the guanine nucleotide exchange factor, RAPGEF5. Here, we demonstrate that RAPGEF5 regulates left-right patterning via Wnt signaling. In particular, RAPGEF5 regulates the nuclear translocation of β-catenin independently of both β-catenin cytoplasmic stabilization and the importin β1/Ran-mediated transport system. We propose a model whereby RAPGEF5 activates the nuclear GTPases, Rap1a/b, to facilitate the nuclear transport of β-catenin, defining a parallel nuclear transport pathway to Ran. Our results suggest new targets for modulating Wnt signaling in disease states.

Wnt3a expression is associated with poor prognosis of esophageal squamous cell carcinoma

The Wnt signaling pathway is widely implicated in various types of cancer. Canonical Wnt signaling, including Wnt3a, may be a key component of cancer progression or chemoresistance. Consequently, it was hypothesized that Wnt3a expression may be a prognostic factor of esophageal squamous cell carcinoma (ESCC) due to its roles in chemoresistance and tumor progression. The aim of the present study was to investigate the association between Wnt3a expression and prognosis in patients with ESCC. Wnt3a expression was evaluated in resected specimens from 139 patients with thoracic ESCC who were subjected to curative surgery without neoadjuvant therapy in Tokai University Hospital between 2007 and 2009. Samples were assessed using immnohistochemistry. Patients with ESCC were divided into two groups according to the expression of Wnt3a in tumor tissue. The influence of Wnt3a expression on clinicopathological findings and prognosis of ESCC were subsequently investigated. Immnohistologically, 68 cases were Wnt3a-positive in the cytoplasm of cancer cells, whereas 71 cases were negative. Multivariate analysis by Cox proportional hazard model showed the association between pN (HR=3.539, P=0.001), venous invasion (HR=2.798, P=0.012), Wnt3a expression (HR=1.691, P=0.046) and overall survival (OS). OS rate and disease-free survival rate were poorer in Wnt3a-positive group compared with those in the Wnt3a-negative group as indicated by the log-rank test (P=0.012 and P=0.023, respectively). In pathological stages I and II, there was no significant difference in the OS rate between Wnt3a-positive and Wnt3a-negative groups; however, the OS rate of the Wnt3a-positive group was significantly worse than that of Wnt3a-negative group in pathological stage III (log rank test; P=0.017). Wnt3a-positive patients with recurrence had a significantly poorer prognosis compared with Wnt3a-negative patients (log-rank test; P=0.023). The present findings suggested that Wnt3a may be a prognostic factor of ESCC.

RAP1B, a DVL2 binding protein, activates Wnt/beta-catenin signaling in esophageal squamous cell carcinoma

RAP1B is a small GTPase, which regulates multiple cellular processes. Up-regulation of RAP1B has been observed in several cancer types. Although previous study has shown that miR-518 inhibited the proliferation and invasion of esophageal squamous cell carcinoma (ESCC) cells possibly by targeting RAP1B, the expression pattern and the functions of RAP1B in ESCC are not fully understood. Here, we have fund that the expression of RAP1B was up-regulated in ESCC clinical samples. Gain-of-function and loss-of-function assays demonstrated that RAP1B promoted the growth, migration and metastasis of the ESCC cells. Moreover, the mechanism study showed that RAP1B interacted with DVL2, an important upstream regulator for beta-catenin/TCF signaling, and activated beta-catenin/TCF signaling. Taken together, our study demonstrated the oncogenic roles of RAP1B in ESCC, and suggested that RAP1B might be a therapeutic target.

Roles of Rap1 signaling in tumor cell migration and invasion

Ras-associated protein-1 (Rap1), a small GTPase in the Ras-related protein family, is an important regulator of basic cellular functions (e.g., formation and control of cell adhesions and junctions), cellular migration, and polarization. Through its interaction with other proteins, Rap1 plays many roles during cell invasion and metastasis in different cancers. The basic function of Rap1 is straightforward; it acts as a switch during cellular signaling transduction and regulated by its binding to either guanosine triphosphate (GTP) or guanosine diphosphate (GDP). However, its remarkably diverse function is rendered by its interplay with a large number of distinct Rap guanine nucleotide exchange factors and Rap GTPase activating proteins. This review summarizes the mechanisms by which Rap1 signaling can regulate cell invasion and metastasis, focusing on its roles in integrin and cadherin regulation, Rho GTPase control, and matrix metalloproteinase expression.

Integrative genomic and functional analysis of human oral squamous cell carcinoma cell lines reveals synergistic effects of FAT1 and CASP8 inactivation

Oral squamous cell carcinoma (OSCC) is genetically highly heterogeneous, which contributes to the challenges of treatment. To create an in vitro model that accurately reflects this heterogeneity, we generated a panel of HPV-negative OSCC cell lines. By whole exome sequencing of the lines and matched patient blood samples, we demonstrate that the mutational spectrum of the lines is representative of primary OSCC in The Cancer Genome Atlas. We show that loss of function mutations in FAT1 (an atypical cadherin) and CASP8 (Caspase 8) frequently occur in the same tumour. OSCC cells with inactivating FAT1 mutations exhibited reduced intercellular adhesion. Knockdown of FAT1 and CASP8 individually or in combination in OSCC cells led to increased cell migration and clonal growth, resistance to Staurosporine-induced apoptosis and, in some cases, increased terminal differentiation. The OSCC lines thus represent a valuable resource for elucidating the impact of different mutations on tumour behaviour.

CDH11 inhibits proliferation and invasion in head and neck cancer

BACKGROUND

In this study, we use a bioinformatics-based strategy to nominate a tumor suppressor gene cadherin-11 (CDH11) and investigate its role in growth and invasion in head and neck squamous cell carcinoma (HNSCC).

METHODS

Using the Oncomine^™ database to compare HNSCC and normal specimens, CDH11 was nominated as having a role in HNSCC. CDH11 expression in HNSCC was evaluated by immunohistochemistry on a tissue microarray (TMA) and immunoblotting and immunofluorescence of cell lines. The functional impact of CDH11 on proliferation and invasion was evaluated after siRNA-mediated knockdown.

RESULTS

In silico analysis suggested that CDH11 is overexpressed in HNSCC compared to normal specimens. HNSCC TMA exhibited a small but significant increase in intensity and proportion of CDH11. By immunoblot analysis, CDH11 was higher in 4/7 HNSCC cell lines compared to normal keratinocytes; CDH11 was highly upregulated in UM-SCC-47 and UM-SCC-74A and detectable in UM-SCC-14A and UM-SCC-29 cell lines. Downregulation of CDH11 in both UM-SCC-29 and UM-SCC-47 using two different siRNAs enhanced proliferation and invasion.

CONCLUSION

CDH11 inhibits cell proliferation and invasion of HNSCC. This suggests that CDH11 functions as a tumor suppressor gene in head and neck cancer. Our findings emphasize the importance of verifying in silico findings with functional studies.

RAP1 GTPase overexpression is associated with cervical intraepithelial neoplasia

RAP1 (RAS proximate 1), a small GTP-binding protein of the RAS superfamily, is a putative oncogene that is highly expressed in several malignant cell lines and types of cancers, including some types of squamous cell carcinoma. However, the participation of RAP1 in cervical carcinogenesis is unknown. We conducted a cross-sectional study of paraffin-embedded cervical biopsies to determine the association of RAP1 with cervical intraepithelial neoplasia (CIN). Standard and quantitative immunohistochemistry assessment of RAP1 expression in fixed tissue was performed on 183 paraffin-embedded cervical biopsies that were classified as normal or non-dysplastic mucosa (NDM) (n = 33); CIN grade 1 (n = 84) and CIN grade 2/3 (n = 66). A gradual increase in RAP1 expression in NDM < CIN 1 < CIN 2/3 (p<0.001) specimens was observed and was in agreement with the histopathologic diagnosis. A progressive increase in the RAP1 expression levels increased the risk of CIN 1 [odds ratio (OR) = 3.50; 95% confidence interval (CI) 1.30-10.64] 3.5 fold and the risk of CIN 2/3 (OR = 19.86, 95% CI 6.40-70.79) nearly 20 fold when compared to NDM. In addition, stereotype ordinal regression analysis showed that this progressive increase in RAP1 expression more strongly impacted CIN 2/3 than CIN 1. Our findings suggest that RAP1 may be a useful biomarker for the diagnosis of CIN.

Discovery of potent, orally bioavailable, small-molecule inhibitors of WNT signaling from a cell-based pathway screen

WNT signaling is frequently deregulated in malignancy, particularly in colon cancer, and plays a key role in the generation and maintenance of cancer stem cells. We report the discovery and optimization of a 3,4,5-trisubstituted pyridine 9 using a high-throughput cell-based reporter assay of WNT pathway activity. We demonstrate a twisted conformation about the pyridine-piperidine bond of 9 by small-molecule X-ray crystallography. Medicinal chemistry optimization to maintain this twisted conformation, cognisant of physicochemical properties likely to maintain good cell permeability, led to 74 (CCT251545), a potent small-molecule inhibitor of WNT signaling with good oral pharmacokinetics. We demonstrate inhibition of WNT pathway activity in a solid human tumor xenograft model with evidence for tumor growth inhibition following oral dosing. This work provides a successful example of hypothesis-driven medicinal chemistry optimization from a singleton hit against a cell-based pathway assay without knowledge of the biochemical target.

Characterization of squamous cell carcinoma in an organotypic culture via subsurface non-linear optical molecular imaging

Tristetraprolin (TTP) is an RNA-binding protein which downregulates multiple cytokines that mediate progression of head and neck squamous cell carcinoma (HNSCC). We previously showed that HNSCC cells with shRNA-mediated knockdown of TTP are more invasive than controls. In this study, we use control and TTP-deficient cells to present a novel subsurface non-linear optical molecular imaging method using a three-dimensional (3D) organotypic construct, and compare the live cell imaging data to histology of fixed tissue specimens. This manuscript describes how to prepare and image the novel organotypic system that closely mimics HNSCC in a clinical setting. The oral cancer equivalent (OCE) system allows HNSCC cells to stratify and invade beyond the basement membrane into underlying connective tissue prepared from decellularized human dermal tissue. The OCE model was inspired by tissue engineering strategies to prepare autologous transplants from human keratinocytes. Advantages of this method over previously used in vitro cancer models include the simulation of the basement membrane and complex connective tissue in the construct, in addition to the ability to track the 3D movement of live invading cells and quantify matrix destruction over time. The OCE model and novel live cell imaging strategy may be applied to study other types of 3D tissue constructs.

Epithelial stem cell mutations that promote squamous cell carcinoma metastasis

Squamous cell carcinomas (SCCs) originate in stratified epithelia, with a small subset becoming metastatic. Epithelial stem cells are targets for driver mutations that give rise to SCCs, but it is unknown whether they contribute to oncogenic multipotency and metastasis. We developed a mouse model of SCC by targeting two frequent genetic mutations in human SCCs, oncogene Kras(G12D) activation and Smad4 deletion, to mouse keratin 15-expressing (K15+) stem cells. We show that transgenic mice developed multilineage tumors, including metastatic SCCs. Among cancer stem cell-enriched (CSC-enriched) populations, those with increased side population (SP) cells correlated with epithelial-mesenchymal transition (EMT) and lung metastasis. We show that microRNA-9 (miR-9) contributed to SP expansion and metastasis, and miR-9 inhibition reduced the number of SP cells and metastasis. Increased miR-9 was detected in metastatic human primary SCCs and SCC metastases, and miR-9-transduced human SCC cells exhibited increased invasion. We identified α-catenin as a predominant miR-9 target. Increased miR-9 in human SCC metastases correlated with α-catenin loss but not E-cadherin loss. Our results demonstrate that stem cells with Kras(G12D) activation and Smad4 depletion can produce tumors that are multipotent and susceptible to EMT and metastasis. Additionally, tumor initiation and metastatic properties of CSCs can be uncoupled, with miR-9 regulating the expansion of metastatic CSCs.

The molecular features of tongue epithelium treated with the carcinogen 4-nitroquinoline-1-oxide and alcohol as a model for HNSCC

Head and neck squamous cell carcinoma (HNSCC) is the sixth most common type of cancer affecting humans worldwide. To determine the potential mechanisms by which chronic tobacco and alcohol abuse lead to HNSCC of the oral cavity, we have used both the 4-nitroquinoline-1-oxide (4-NQO) murine oral carcinogenesis and the Meadows-Cook alcohol models. In this study, we treated mice with 4-NQO in drinking water for 10 weeks and then administered 20% (w:v) ethanol (EtOH) for another 10 weeks. We observed increased levels and/or activation of signaling proteins [p38 mitogen-activated protein kinase (MAPK), β-catenin and Erk 1/2] that are typically altered during HNSCC initiation in humans. We found that EtOH administration alone increased the expression of p38 MAPK but not Erk 1/2 MAPK. Total β-catenin levels in the tongues increased by 2- to 3-fold after 4-NQO treatment, with or without EtOH. However, EtOH combined with 4-NQO reduced phosphorylated β-catenin levels, whereas 4-NQO treatment alone did not. These data implicate EtOH as a regulator of β-catenin signaling in this HNSCC model. We also utilized K14-CreER(TAM); ROSA26 mice to mark permanently stem/progenitor cells in the tongue epithelia. We found that 4-NQO alone and 4-NQO plus EtOH treatment resulted in massive, horizontal expansion of stem/progenitor cell populations arising from single stem cells in the basal layer of the epithelia. This expansion is consistent with carcinogen-associated, symmetric division of stem/progenitor cells. Our data suggest that specific therapeutic targets for prevention of HNSCC of the oral cavity associated with both alcohol and tobacco use are p38 MAPK and β-catenin.

The Histone Methyltransferase EZH2 Mediates Tumor Progression on the Chick Chorioallantoic Membrane Assay, a Novel Model of Head and Neck Squamous Cell Carcinoma

Current in vivo models for head and neck squamous cell carcinoma (HNSCC) have limitations in simulating some essential tumorigenic phenotypes, such as invasion. Most mouse models of human HNSCC are inadequate because tumor cells are injected directly into the connective tissue, thereby bypassing the basement membrane of the surface epithelium, the first barrier to invasion. In this manuscript, we establish the chick chorioallantoic membrane (CAM) assay as an in vivomodel of human HNSCC tumor progression. Using the CAM model of HNSCC, we investigated the role of enhancer of zeste homolog 2 (EZH2), a histone methyltransferase, in multiple aspects of HNSCC tumor progression. We found that knockdown of EZH2 reduced tumor size, angiogenesis, invasion, and metastasis of tumors produced by grafting human HNSCC cells onto the CAM. In addition, we demonstrate that EZH2 expression mediates a mesenchymal phenotype in HNSCC cell lines and mouse tumors. These findings demonstrate the advantages of the newly proposed CAM model of human HNSCC and highlight the emerging role of EZH2 in HSNCC tumor progression.

An adenosine-mediated signaling pathway suppresses prenylation of the GTPase Rap1B and promotes cell scattering

During metastasis, cancer cells acquire the ability to dissociate from each other and migrate, which is recapitulated in vitro as cell scattering. The small guanosine triphosphatase (GTPase) Rap1 opposes cell scattering by promoting cell-cell adhesion, a function that requires its prenylation, or posttranslational modification with a carboxyl-terminal isoprenoid moiety, to enable its localization at cell membranes. Thus, signaling cascades that regulate the prenylation of Rap1 offer a mechanism to control the membrane localization of Rap1. We identified a signaling cascade initiated by adenosine A2B receptors that suppressed the prenylation of Rap1B through phosphorylation of Rap1B, which decreased its interaction with the chaperone protein SmgGDS (small GTPase guanosine diphosphate dissociation stimulator). These events promoted the cytosolic and nuclear accumulation of nonprenylated Rap1B and diminished cell-cell adhesion, resulting in cell scattering. We found that nonprenylated Rap1 was more abundant in mammary tumors than in normal mammary tissue in rats and that activation of adenosine receptors delayed Rap1B prenylation in breast, lung, and pancreatic cancer cell lines. Our findings support a model in which high concentrations of extracellular adenosine, such as those that arise in the tumor microenvironment, can chronically activate A2B receptors to suppress Rap1B prenylation and signaling at the cell membrane, resulting in reduced cell-cell contact and promoting cell scattering. Inhibiting A2B receptors may be an effective method to prevent metastasis.

N-glycosylation induces the CTHRC1 protein and drives oral cancer cell migration

Oral squamous cell carcinoma (OSCC) is one of the most pernicious malignancies, but the mechanisms underlying its development and progression are poorly understood. One of the key pathways implicated in OSCC is the canonical Wnt/β-catenin signaling pathway. Previously, we reported that canonical Wnt signaling functions in a positive feedback loop with the DPAGT1 gene, a principal regulator of the metabolic pathway of protein N-glycosylation, to hyperglycosylate E-cadherin and reduce intercellular adhesion. Here, we show that in OSCC, DPAGT1 and canonical Wnt signaling converge to up-regulate CTHRC1 (collagen triple helix repeat containing 1), an N-glycoprotein implicated in tumor invasion and metastasis. We found that in human OSCC specimens, amplification of the levels of CTHRC1 was associated with its hyperglycosylation. Partial inhibition of DPAGT1 expression in OSCC CAL27 cells reduced CTHRC1 abundance by increasing protein turnover, indicating that N-glycosylation stabilizes CTHRC1. Additionally, canonical Wnt signaling promoted β-catenin/T-cell factor transcriptional activity at the CTHRC1 promoter to further elevate CTHRC1 levels. We demonstrate that DPAGT1 promotes cell migration and drives the localization of CTHRC1 to cells at the leading edge of a wound front coincident with drastic changes in cell morphology. We propose that in OSCC, dysregulation of canonical Wnt signaling and DPAGT1-dependent N-glycosylation induces CTHRC1, thereby driving OSCC cell migration and tumor spread.

The importance of oncogenic transcription factors for oral cancer pathogenesis and treatment

Oral squamous cell carcinoma is a major cause of morbidity and mortality worldwide. Current experimental evidence shows that most important risk factors for oral cancer include tobacco use and excessive alcohol consumption and less well-defined risks include viral infection and a diet deficient in antioxidants. The positive correlation between various risk/etiologic factors of oral cancer and the activation of various transcription factors (TFs) has been reported in the literature. Although initially, TFs were considered to be very difficult targets for use in clinical treatment, recent technological advances have provided the ability to control these factors of cancer progression. This review focuses on the role of oncogenic transcription factors in oral cancer, their modes of activation through various biological pathways, the promises and pitfalls in viewing them as potent oncotargets, the way they can be controlled based on the current understanding, and the future research to be done in this area.

β-Arrestin2 regulates lysophosphatidic acid-induced human breast tumor cell migration and invasion via Rap1 and IQGAP1

β-Arrestins play critical roles in chemotaxis and cytoskeletal reorganization downstream of several receptor types, including G protein-coupled receptors (GPCRs), which are targets for greater than 50% of all pharmaceuticals. Among them, receptors for lysophosphatidic acid (LPA), namely LPA(1) are overexpressed in breast cancer and promote metastatic spread. We have recently reported that β-arrestin2 regulates LPA(1)-mediated breast cancer cell migration and invasion, although the underlying molecular mechanisms are not clearly understood. We show here that LPA induces activity of the small G protein, Rap1 in breast cancer cells in a β-arrestin2-dependent manner, but fails to activate Rap1 in non-malignant mammary epithelial cells. We found that Rap1A mRNA levels are higher in human breast tumors compared to healthy patient samples and Rap1A is robustly expressed in human ductal carcinoma in situ and invasive tumors, in contrast to the normal mammary ducts. Rap1A protein expression is also higher in aggressive breast cancer cells (MDA-MB-231 and Hs578t) relative to the weakly invasive MCF-7 cells or non-malignant MCF10A mammary cells. Depletion of Rap1A expression significantly impaired LPA-stimulated migration of breast cancer cells and invasiveness in three-dimensional Matrigel cultures. Furthermore, we found that β-arrestin2 associates with the actin binding protein IQGAP1 in breast cancer cells, and is necessary for the recruitment of IQGAP1 to the leading edge of migratory cells. Depletion of IQGAP1 blocked LPA-stimulated breast cancer cell invasion. Finally, we have identified that LPA enhances the binding of endogenous Rap1A to β-arrestin2, and also stimulates Rap1A and IQGAP1 to associate with LPA(1). Thus our data establish novel roles for Rap1A and IQGAP1 as critical regulators of LPA-induced breast cancer cell migration and invasion.

Overexpression of Rap-1A indicates a poor prognosis for oral cavity squamous cell carcinoma and promotes tumor cell invasion via Aurora-A modulation

The functions of Rap-1A in oral carcinogenesis are largely unexplored. In this study, we examined the expression of Rap-1A at different malignant stages of oral cavity squamous cell carcinoma (OCSCC). Semiquantitative RT-PCR, quantitative RT-PCR, and Western blotting were used to evaluate Rap-1A mRNA and protein expressions, respectively, in paired OCSCC patient specimens. To determine the possible correlation between Rap-1A expression and various clinical characteristics, 256 samples from patients with OCSCC were evaluated by immunohistochemical staining. Strong Rap-1A expression was a significant prognostic marker and predictor of aggressive OCSCC. The overall and disease-specific 5-year survival rates were significantly correlated with strong expression of Rap-1A (P < 0.001). Functionally, overexpressed Rap-1A could promote oral cancer cell migration and invasion by Transwell chambers and wound healing assay. Conversely, the suppression of Rap-1A expression using Rap-1A-mediated siRNA was sufficient to decrease cell motility. Furthermore, our data also illustrated that Aurora-A could not only induce mRNA and protein expressions of Rap-1A for enhancing cancer cell motility but also co-localize and form a complex with Rap-1A in the oral cancer cell line. Finally, immunohistochemical staining, indirect immunofluorescence, and Western blotting analysis of human aggressive OCSCC specimens revealed a significantly positive correlation between Rap-1A and Aurora-A expression. Taken together, our results suggest that the Aurora-A/Rap-1A pathway is associated with survival, tumor progression, and metastasis of OCSCC patients.

Prognostic and predictive markers in medullary thyroid carcinoma

Unlike papillary thyroid carcinoma, medullary thyroid carcinoma is insensitive to adjuvant treatment with radioactive iodine. The clinical management of patients with advanced or metastatic disease remains challenging since no effective systemic adjuvant therapy is available. We aimed to identify markers of aggressive disease and novel drugable protein targets that would provide systemic adjuvant treatment for patients with advanced medullary thyroid carcinoma. We therefore examined morphologic features of aggressive behavior and the expression of 41 proteins involved in apoptosis, cell cycle, angiogenesis, inflammation, cell adhesion, tumor-specific markers, and WNT, SHH, and AKT pathways using tissue microarray from 23 patients with medullary thyroid carcinoma. Protein expression was determined using computerized image analysis software. Statistical analysis was carried out to correlate clinical data with the average score for each marker. Angioinvasion proved to be the most reliable predictor of disease recurrence and death. The rate of angioinvasion was 43 %. All angioinvasive medullary thyroid carcinomas had locoregional and/or distant metastasis; 60 % of angioinvasive medullary thyroid carcinomas developed distant metastasis. We identified expression of several potentially important protein targets such as COX-1/2, Bcl-2a, Gst-π, Gli-1, Gli-2, Gli-3, and Bmi-1 that may be therapeutically targeted in medullary thyroid carcinoma. More importantly, the immunohistochemical profile of SSTRs in medullary thyroid carcinoma may also have clinical relevance for the administration of peptide receptor radionuclide treatment. Successful outcome of clinical trials directed against these novel targets would provide much needed systemic adjuvant treatment for patients with advanced medullary thyroid carcinoma, and our data suggest the possibility of stratifying patients who are likely to require adjuvant therapy before their burden of disease precludes successful therapeutic effect.

A novel approach to biomarker discovery in head and neck cancer using an autoantibody signature

Despite the dismal prognosis for patients with squamous cell carcinoma of the head and neck (SCCHN), there have been no novel treatments in over 40 years. Identification of novel tumor antigens in SCCHN will facilitate the identification of potential novel treatment targets. Tumor antigens are proteins selectively expressed by tumor cells and recognized by the host immune system. Phage-displayed tumor antigens were enriched by biopanning with normal and then SCCHN-specific serum. Ninety-six phage clones were sequenced for identification, and 21 clones were validated using Luminex. One of these proteins, L23, a novel tumor antigen in SCCHN, was validated as an oncogene. L23 is upregulated in SCCHN compared with normal keratinocytes. Knockdown of L23 inhibited proliferation, invasion and cell survival. Overexpression of L23 had the reverse effect. Overexpression of L23 in non malignant cells led to transformation. Injection of SCCHN cells with knockdown of L23 in mice, induced tumors that were significantly smaller than control tumors. In conclusion, the immunomic screen yielded a panel of antigens specific to SCCHN; one of these proteins, L23, is a novel oncogene in SCCHN.

Biomarkers of epithelial-mesenchymal transition in squamous cell carcinoma

An understanding of the process by which tumor cells destroy the basement membrane of the surface epithelium, invade, and metastasize is essential to the development of novel treatment of head and neck squamous cell carcinoma (HNSCC). In recent years, there has been increased interest in the role of epithelial-mesenchymal transition (EMT) in invasion. EMT is a process that describes the development of motile, mesenchymal-like cells from non-motile parent epithelial cells. There are 3 known types of EMT that mediate development, wound healing, and carcinogenesis. This review summarizes studies of known EMT biomarkers in the context of HNSCC progression. The biomarkers discussed come from a wide range of proteins, including cell-surface proteins (E-cadherin, N-cadherin, and Integrins), cytoskeletal proteins (α-Smooth Muscle Actin, Vimentin, and β-catenin), extracellular matrix proteins (Collagens, Fibronectin, and Laminin), and transcription factors (SNAIL1, SNAIL2, TWIST, and LEF-1). Overall, the findings of these studies suggest that EMT mediates HNSCC progression. The mechanistic role of the EMT markers that have been associated with HNSCC should be more clearly defined if new anti-HNSCC therapies to block EMT progression are to be developed.

Rap1 and its regulatory proteins: the tumor suppressor, oncogene, tumor suppressor gene axis in head and neck cancer

Squamous cell carcinoma of the head and neck (SCCHN) is the sixth most common cancer, globally. Previously, we showed that Rap1GAP is a tumor suppressor gene that inhibits tumor growth, but promotes invasion in SCCHN. In this work, we discuss the role of Rap1 and Rap1GAP in SCCHN progression in the context of a microRNA-oncogene-tumor suppressor gene axis, and investigate the role of Rap1GAP in EZH2-mediated invasion. Loss of expression of microRNA-101 in SCCHN leads to upregulation of EZH2, a histone methyltransferase. Overexpression of EZH2 silences Rap1GAP via methylation, thereby promoting activation of its target, Rap1. This microRNA-controlled activation of Rap1, via EZH2-mediated silencing of Rap1GAP, is a novel mechanism of Rap1 regulation. In two independent SCCHN cell lines, downregulation of EZH2 inhibits proliferation and invasion. In both cell lines, stable knockdown of EZH2 (shEZH2) recovers Rap1GAP expression and inhibits proliferation. However, siRNA-mediated knockdown of Rap1GAP in these cells rescues proliferation but not invasion. Thus, EZH2 promotes proliferation and invasion via Rap1GAP-dependent and -independent mechanisms, respectively. Although the studies presented here are in the context of SCCHN, our results may have broader implications, given that Rap1GAP acts as a tumor suppressor in pancreatic cancer, thyroid cancer, and melanoma.

Inhibitory effects of lupeal acetate of Cortex periplocae on N-nitrosomethylbenzylamine-induced rat esophageal tumorigenesis

Lupeal acetate of Cortex periplocae (CPLA), a triterpene compound extracted from a traditional Chinese herb, has been identified as an inhibitor of cancer cell growth. The objective of the present study was to evaluate the potential mechanisms through which CPLA inhibits N-nitrosomethylbenzylamine (NMBA)-induced rat esophageal tumorigenesis. We treated F344 rats subcutaneously with the esophageal carcinogen NMBA (0.5 mg/kg body weight) and intramuscularly with CPLA (20 mg/kg), 3 times a week for 5 weeks. Rats were then sacrificed at weeks 9, 15 or 25, esophageal tissues were collected and tumor data were recorded. To investigate the mechanisms by which CPLA modulates tumorigenesis in esophagus, we evaluated the protein expression of glycogen synthase kinase-3β (GSK-3β) and β-catenin and the gene expression of c-myc. CPLA significantly (P<0.05) reduced the incidence of esophageal tumors observed at 25 weeks from 93.3% in NMBA-treated controls to 33.3% in the NMBA- and CPLA-treated rats. CPLA reduced β-catenin and c-myc expression, but increased GSK-3β expression, in preneoplastic lesions of the esophagus. These results suggest a novel tumor-suppressive role of CPLA through the activation of GSK-3β expression and the inhibition of β-catenin and c-myc expression. Therefore, CPLA is a potential therapeutic candidate for esophageal squamous cell carcinoma.

Implication of stem cells in the biology and therapy of head and neck cancer

The progress which has been made in the therapy of patients with head and neck cancer in recent years mainly concern the HPV associated HNSCC and the quality of life. The overall survival of patients carrying non HPV associated HNSCC during the last thirty years has not experienced any significant improvement and must be referred to as static [1], [2]. The problem of the illness remains unchanged in the frequent and poorly controllable relapse situation. The locoregionally originating tumours or lymph node metastases show a considerably poorer response towards current therapies. Likewise for a number of patients a formation of distant metastases seems to develop during the course of the illness. Those distant metastases are also therapeutically rather difficult to control. Therefore the mortality of the non HPV induced head and neck cancer remains unchanged.

The term “stem cell” describes the entity cell, which acts as a reservoir for new cells in order to replace defective or necrotic cells. A fundamental characteristic of stem cells is the constant ability to multiply into different type of cells, which subsequently do not proliferate.

With the insight of new knowledge within the regenerative medicine and the ability of stem cells of self regenerating proliferation and their multipotency in the differentiation, the origin of cancer attains a new distinction. If you look on the tumour as a malignant wound it becomes obvious, that the regeneration or the composition of additional tissue depends on the presence and differentiation of stem cells. The wound healing, which is a regeneration of tissue depends not only on stationary stem cells. In fact stem cells are attracted for “homing” in the defective areas by despatch of various messengers, which then form and replace the vascular tree or other tissue [3], [4].

Next to those stem cells, which functionally help to form tumour tissue, a small entity of “real cancer stem cells” in solid tumours is expected. Those occur in tumours and they have typical stem cell characteristics like self-regeneration and the potential of differentiation and are potentially responsible for tumour growth. With their ability of self-regeneration they would have the ability to form a complete tumour out of every single cell. That tumour would histologically look like the tumour those cells initially originated from. Of particular interest regarding those currently still elusive cancer stem cells is their resistance towards current therapies like radiotherapy or chemotherapy. Those insights now get a completely new meaning in tumour biology: Does a cancer stem cell exist, which is able to initiate and keep up tumour growth despite all possible therapeutic interventions?

This presentation will outline the current views regarding cancer stem cells in non HPV associated HNSCC and it will highlight problems, which are currently researched on. The objective must be to understand the biology of those cells in a way that make an extended range of therapeutics possible. A therapy, which specifically targets cancer stem cells, could improve the chances of recovery.

Implication of RNA-binding protein La in proliferation, migration and invasion of lymph node-metastasized hypopharyngeal SCC cells

The 5-year survival rate for oral cavity cancer is poorer than for breast, colon or prostate cancer, and has improved only slightly in the last three decades. Hence, new therapeutic strategies are urgently needed. Here we demonstrate by tissue micro array analysis for the first time that RNA-binding protein La is significantly overexpressed in oral squamous cell carcinoma (SCC). Within this study we therefore addressed the question whether siRNA-mediated depletion of the La protein may interfere with known tumor-promoting characteristics of head and neck SCC cells. Our studies demonstrate that the La protein promotes cell proliferation, migration and invasion of lymph node-metastasized hypopharyngeal SCC cells. We also reveal that La is required for the expression of β-catenin as well as matrix metalloproteinase type 2 (MMP-2) within these cells. Taken together these data suggest a so far unknown function of the RNA-binding protein La in promoting tumor progression of head and neck SCC.

Genistein attenuates WNT signaling by up-regulating sFRP2 in a human colon cancer cell line

Colorectal cancer (CRC) is a leading fatal carcinoma worldwide. Our goal was to investigate the effects of genistein on WNT signaling, which is involved in colon epithelial cell growth and apoptosis. Human colon cancer cell line DLD-1 was treated for four days with 75 μmol/L genistein. Decreased nuclear β-catenin and increased phospho- β-catenin accumulation was detected, showing a change in WNT signaling. Reverse transcriptase-polymerase chain reaction analysis showed increased sFRP2 (a WNT pathway antagonist) mRNA expression following the genistein treatment. Methylation selective polymerase chain reaction showed decreased methylation in two CpG islands of the sFRP2 gene following genistein treatment, similar to the effect of 5-aza-cytidine, a demethylation agent. We observed reduced DLD-1 cell viability and increased apoptosis with genistein treatment. Genistein inhibits β-catenin-mediated WNT signaling through increasing sFRP2 gene expression by demethylating its silenced promoter in colon cancer cell line DLD-1.

Tristetraprolin regulates interleukin-6, which is correlated with tumor progression in patients with head and neck squamous cell carcinoma

BACKGROUND

Tumor-derived cytokines play a significant role in the progression of head and neck squamous cell carcinoma (HNSCC). Targeting proteins, such as tristetraprolin (TTP), that regulate multiple inflammatory cytokines may inhibit the progression of HNSCC. However, TTP's role in cancer is poorly understood. The goal of the current study was to determine whether TTP regulates inflammatory cytokines in patients with HNSCC.

METHODS

TTP messenger RNA (mRNA) and protein expression were determined by quantitative real-time-polymerase chain reaction (Q-RT-PCR) and Western blot analysis, respectively. mRNA stability and cytokine secretion were evaluated by quantitative RT-PCR and enzyme-linked immunoadsorbent assay, respectively, after overexpression or knockdown of TTP in HNSCC. HNSCC tissue microarrays were immunostained for interleukin-6 (IL-6) and TTP.

RESULTS

TTP expression in HNSCC cell lines was found to be inversely correlated with the secretion of IL-6, vascular endothelial growth factor (VEGF), and prostaglandin E2 (PGE(2) )(.) Knockdown of TTP increased mRNA stability and the secretion of cytokines. Conversely, overexpression of TTP in HNSCC cells led to decreased secretion of IL-6, VEGF, and PGE(2) . Immunohistochemical staining of tissue microarrays for IL-6 demonstrated that staining intensity is prognostic for poor disease-specific survival (P = .023), tumor recurrence and development of second primary tumors (P = .014), and poor overall survival (P = .019).

CONCLUSIONS

The results of the current study demonstrated that down-regulation of TTP in HNSCC enhances mRNA stability and promotes secretion of IL-6, VEGF, and PGE(2) . Furthermore, high IL-6 secretion in HNSCC tissue is a biomarker for poor prognosis. In as much as enhanced cytokine secretion is associated with poor prognosis, TTP may be a therapeutic target to reduce multiple cytokines concurrently in patients with HNSCC.

Targeting the oncogenic protein beta-catenin to enhance chemotherapy outcome against solid human cancers

Background

Beta-catenin is a multifunctional oncogenic protein that contributes fundamentally to cell development and biology. Elevation in expression and activity of β-catenin has been implicated in many cancers and associated with poor prognosis. Beta-catenin is degraded in the cytoplasm by glycogen synthase kinase 3 beta (GSK-3β) through phosphorylation. Cell growth and proliferation is associated with β-catenin translocation from the cytoplasm into the nucleus.

This laboratory was the first to demonstrate that selenium-containing compounds can enhance the efficacy and cytotoxicity of anticancer drugs in several preclinical xenograft models. These data provided the basis to identify mechanism of selenium action focusing on β-catenin as a target. This study was designed to: (1) determine whether pharmacological doses of methylseleninic acid (MSeA) have inhibitory effects on the level and the oncogenic activity of β-catenin, (2) investigate the kinetics and the mechanism of β-catenin inhibition, and (3) confirm that inhibition of β-catenin would lead to enhanced cytotoxicity of standard chemotherapeutic drugs.

Results

In six human cancer cell lines, the inhibition of total and nuclear expression of β-catenin by MSeA was dose and time dependent. The involvement of GSK-3β in the degradation of β-catenin was cell type dependent (GSK-3β-dependent in HT-29, whereas GSK-3β-independent in HCT-8). However, the pronounced inhibition of β-catenin by MSeA was independent of various drug treatments and was not reversed after combination therapy.

Knockout of β-catenin by ShRNA and its inhibition by MSeA yielded similar enhancement of cytotoxicity of anticancer drugs.

Collectively, the generated data demonstrate that β-catenin is a target of MSeA and its inhibition resulted in enhanced cytotoxicity of chemotherapeutic drugs.

Conclusions

This study demonstrates that β-catenin, a molecule associated with drug resistance, is a target of selenium and its inhibition is associated with increased multiple drugs cytotoxicity in various human cancers. Further, degradation of β-catenin by GSK-3β is not a general mechanism but is cell type dependent.