Restoration of auditory evoked responses by human ES-cell-derived otic progenitors.

Deafness is a condition with a high prevalence worldwide, produced primarily by the loss of the sensory hair cells and their associated spiral ganglion neurons (SGNs). Of all the forms of deafness, auditory neuropathy is of particular concern. This condition, defined primarily by damage to the SGNs with relative preservation of the hair cells, is responsible for a substantial proportion of patients with hearing impairment. Although the loss of hair cells can be circumvented partially by a cochlear implant, no routine treatment is available for sensory neuron loss, as poor innervation limits the prospective performance of an implant. Using stem cells to recover the damaged sensory circuitry is a potential therapeutic strategy. Here we present a protocol to induce differentiation from human embryonic stem cells (hESCs) using signals involved in the initial specification of the otic placode. We obtained two types of otic progenitors able to differentiate in vitro into hair-cell-like cells and auditory neurons that display expected electrophysiological properties. Moreover, when transplanted into an auditory neuropathy model, otic neuroprogenitors engraft, differentiate and significantly improve auditory-evoked response thresholds. These results should stimulate further research into the development of a cell-based therapy for deafness.

Fibroblast gene expression profile reflects the stage of tumour progression in oral squamous cell carcinoma.

Oral cancer is a highly aggressive malignancy with poor prognosis. This study examined the behaviour of fibroblast strains from normal oral mucosa, dysplastic epithelial tissue, and genetically stable (minimal copy number alterations-CNA; minimal loss of heterozygosity-LOH; wild-type p53; wild-type p16INK4A) and unstable (extensive CNA and LOH; inactivation of p53 and p16INK4A) oral squamous cell carcinoma (OSCC). Fibroblasts from genetically unstable OSCC relative to the other fibroblast subtypes grew more slowly and stimulated the invasion of a non-tumourigenic keratinocyte cell line into fibroblast-rich collagen gels. To understand these findings, genome-wide transcriptional profiles were generated using the GeneChip(®) cDNA whole transcript microarray platform. Principal component analysis showed that the fibroblasts could be distinguished according to the stage of tumour development. Tumour progression was associated with down-regulation of cell cycle- and cytokinesis-related genes and up-regulation of genes encoding transmembrane proteins including cell adhesion molecules. Gene expression was validated in independent fibroblast strains using qRT-PCR. Gene connectivity and interactome-transcriptome associations were determined using a systems biology approach to interrogate the gene expression data. Clusters of gene signatures were identified that characterized genetically unstable and stable OSCCs relative to each other and to fibroblasts from normal oral mucosa. The expression of highly connected genes associated with unstable OSCCs, including those that encode α-SMA and the integrin α6, correlated with poor patient prognosis in an independent dataset of head and neck cancer. The results of this study demonstrate that fibroblasts from unstable OSCCs represent a phenotypically distinguishable subset that plays a major role in oral cancer biology.

A molecular study of desmosomes identifies a desmoglein isoform switch in head and neck squamous cell carcinoma.

Desmosomes, the intercellular junctions that confer strong adhesion between epithelial cells, are frequently altered in malignancy. However, a comprehensive analysis of these structures has not been carried out in oral neoplasia. Oral squamous cell carcinomas (SCCs) and pre-malignant dysplasia can be sub-classified according to their in vitro replicative lifespan, where the immortal dysplasia (ID) and carcinoma (IC) subsets have p16(ink4a) and p53 dysfunction, telomerase deregulation and genetic instability and the mortal subset (MD and MC) do not. We found that the desmosomal proteins exhibit a distinct expression pattern in oral mucosa when compared with epidermis in vivo. Microarray data from a large panel of lines revealed that the transcript levels of DSG3, DSC2/3, DP, PG and PKP1 were reduced in ID and IC. Interestingly, DSG2 was up-regulated in MC. Reduction of DSG3 and up-regulation of DSG2 were found in two independent microarray datasets. Significantly, we demonstrated that reduction of DSG3 and up-regulation of DSG2 was reversible in vitro by using RNAi-mediated knockdown of DSG2 in IC cells. The remaining desmosomal proteins were largely disrupted or internalized and associated with retraction of keratin intermediate filaments in oral SCC lines. These findings suggest dysfunction and loss of desmosomal components are common events in the immortal class of oral SCC and that these events may precede overt malignancy.

Epigenetic downregulation of human disabled homolog 2 switches TGF-beta from a tumor suppressor to a tumor promoter.

The cytokine TGF-beta acts as a tumor suppressor in normal epithelial cells and during the early stages of tumorigenesis. During malignant progression, cancer cells can switch their response to TGF-beta and use this cytokine as a potent oncogenic factor; however, the mechanistic basis for this is poorly understood. Here we demonstrate that downregulation of disabled homolog 2 (DAB2) gene expression via promoter methylation frequently occurs in human squamous cell carcinomas (SCCs) and acts as an independent predictor of metastasis and poor prognosis. Retrospective microarray analysis in an independent data set indicated that low levels of DAB2 and high levels of TGFB2 expression correlate with poor prognosis. Immunohistochemistry, reexpression, genetic knockout, and RNAi silencing studies demonstrated that downregulation of DAB2 expression modulated the TGF-beta/Smad pathway. Simultaneously, DAB2 downregulation abrogated TGF-beta tumor suppressor function, while enabling TGF-beta tumor-promoting activities. Downregulation of DAB2 blocked TGF-beta-mediated inhibition of cell proliferation and migration and enabled TGF-beta to promote cell motility, anchorage-independent growth, and tumor growth in vivo. Our data indicate that DAB2 acts as a tumor suppressor by dictating tumor cell TGF-beta responses, identify a biomarker for SCC progression, and suggest a means to stratify patients with advanced SCC who may benefit clinically from anti-TGF-beta therapies.

Spectral clustering of microarray data elucidates the roles of microenvironment remodeling and immune responses in survival of head and neck squamous cell carcinoma.

PURPOSE: To identify functionally related prognostic gene sets for head and neck squamous cell carcinoma (HNSCC) by unsupervised statistical analysis of microarray data. PATIENTS AND METHODS: Microarray analysis was performed on 14 normal oral epithelium and 71 HNSCCs from patients with outcome data. Spectral clustering (SC) analysis of the data set identified multiple vectors representing distinct aspects of gene expression heterogeneity between samples. Gene ontology (GO) analysis of vector gene lists identified gene sets significantly enriched within defined biologic pathways. The prognostic significance of these was established by Cox survival analysis. RESULTS: The most influential SC vectors were V2 and V3. V2 separated normal from tumor samples. GO analysis of V2 gene lists identified pathways with heterogeneous expression between HNSCCs, notably focal adhesion (FA)/extracellular matrix remodeling and cytokine-cytokine receptor (CR) interactions. Similar analysis of V3 gene lists identified further heterogeneity in CR pathways. V2CR genes represent an innate immune response, whereas high expression of V3CR genes represented an adaptive immune response that was not dependent on human papillomavirus status. Survival analysis demonstrated that the FA gene set was prognostic of poor outcome, whereas classification for adaptive immune response by the CR gene set was prognostic of good outcome. A combined FA&CR model dramatically exceeded the performance of current clinical classifiers (P < .001 in our cohort and, importantly, P = .007 in an independent cohort of 60 HNSCCs). CONCLUSION: The application of SC and GO algorithms to HNSCC microarray data identified gene sets highly significant for predicting patient outcome. Further large-scale studies will establish the usefulness of these gene sets in the clinical management of HNSCC.

FOXM1 upregulation is an early event in human squamous cell carcinoma and it is enhanced by nicotine during malignant transformation.

BACKGROUND: Cancer associated with smoking and drinking remains a serious health problem worldwide. The survival of patients is very poor due to the lack of effective early biomarkers. FOXM1 overexpression is linked to the majority of human cancers but its mechanism remains unclear in head and neck squamous cell carcinoma (HNSCC). METHODOLOGY/PRINCIPAL FINDINGS: FOXM1 mRNA and protein expressions were investigated in four independent cohorts (total 75 patients) consisting of normal, premalignant and HNSCC tissues and cells using quantitative PCR (qPCR), expression microarray, immunohistochemistry and immunocytochemistry. Effect of putative oral carcinogens on FOXM1 transcriptional activity was dose-dependently assayed and confirmed using a FOXM1-specific luciferase reporter system, qPCR, immunoblotting and short-hairpin RNA interference. Genome-wide single nucleotide polymorphism (SNP) array was used to 'trace' the genomic instability signature pattern in 8 clonal lines of FOXM1-induced malignant human oral keratinocytes. Furthermore, acute FOXM1 upregulation in primary oral keratinocytes directly induced genomic instability. We have shown for the first time that overexpression of FOXM1 precedes HNSCC malignancy. Screening putative carcinogens in human oral keratinocytes surprisingly showed that nicotine, which is not perceived to be a human carcinogen, directly induced FOXM1 mRNA, protein stabilisation and transcriptional activity at concentrations relevant to tobacco chewers. Importantly, nicotine also augmented FOXM1-induced transformation of human oral keratinocytes. A centrosomal protein CEP55 and a DNA helicase/putative stem cell marker HELLS, both located within a consensus loci (10q23), were found to be novel targets of FOXM1 and their expression correlated tightly with HNSCC progression. CONCLUSIONS/SIGNIFICANCE: This study cautions the potential co-carcinogenic effect of nicotine in tobacco replacement therapies. We hypothesise that aberrant upregulation of FOXM1 may be inducing genomic instability through a program of malignant transformation involving the activation of CEP55 and HELLS which may facilitate aberrant mitosis and epigenetic modifications. Our finding that FOXM1 is upregulated early during oral cancer progression renders FOXM1 an attractive diagnostic biomarker for early cancer detection and its candidate mechanistic targets, CEP55 and HELLS, as indicators of malignant conversion and progression.

Telomere dysfunction in human keratinocytes elicits senescence and a novel transcription profile.

The uncapping of telomeres has been shown to precipitate senescence in normal human fibroblasts and apoptosis in lymphocytes and p53-competent cancer cell lines. However, the effects of telomere uncapping on normal epithelial cells have not previously been examined. We have used the well characterised telomere repeat binding factor 2 (TRF2) dominant-negative mutant, TRF2(DeltaBDeltaM), to deplete Normal Human Epidermal Keratinocytes (NHEK) telomeres of TRF2. We observed only a two fold increase in both phosphorylation of p53 at serine 15 and 53BP1 DNA damage foci and no detectable increase in p21(WAF). Despite the weak DNA damage response, the keratinocytes growth arrest, demonstrate reduced colony formation and senescence. The small, abortive senescent colonies did not incorporate Brd-U within 48 h and expressed senescence-associated beta galactosidase (SA-beta-gal). Transcriptional profiling of TRF2-depleted keratinocytes showed a reproducible up-regulation of several genes. These included histones, genes associated with DNA damage and keratinocyte terminal differentiation. Several of the same genes were also shown to be up-regulated when keratinocytes undergo natural telomere-mediated senescence and down-regulated by ectopic telomerase expression. This study has thus revealed highly sensitive and specific candidate indicators of telomere dysfunction that may find use in identifying telomere-mediated keratinocyte senescence in ageing, cancer and other diseases.

Divergent routes to oral cancer.

Most head and neck squamous cell carcinoma (HNSCC) patients present with late-stage cancers, which are difficult to treat. Therefore, early diagnosis of high-risk premalignant lesions and incipient cancers is important. HNSCC is currently perceived as a single progression mechanism, resulting in immortal invasive cancers. However, we have found that approximately 40% of primary oral SCCs are mortal in culture, and these have a better prognosis. About 60% of oral premalignancies (dysplasias) are also mortal. The mortal and immortal tumors are generated in vivo as judged by p53 mutations and loss of p16(INK4A) expression being found only in the original tumors from which the immortal cultures were derived. To investigate the relationships of dysplasias to SCCs, we did microarray analysis of primary cultures of 4 normal oral mucosa biopsies, 19 dysplasias, and 16 SCCs. Spectral clustering using the singular value decomposition and other bioinformatic techniques showed that development of mortal and immortal SCCs involves distinct transcriptional changes. Both SCC classes share most of the transcriptional changes found in their respective dysplasias but have additional changes. Moreover, high-risk dysplasias that subsequently progress to SCCs more closely resemble SCCs than nonprogressing dysplasias. This indicates for the first time that there are divergent mortal and immortal pathways for oral SCC development via intermediate dysplasias. We believe that this new information may lead to new ways of classifying HNSCC in relation to prognosis.