Gene expression signature predicts lymphatic metastasis in squamous cell carcinoma of the oral cavity

Molecular signatures of metastasis in head and neck cancer

BACKGROUND

Metastases are the primary cause of cancer treatment failure and death, yet metastatic mechanisms remain incompletely understood.

METHODS

We studied the molecular basis of head and neck cancer metastasis by transcriptionally profiling 70 samples from 27 patients-matching normal adjacent tissue, primary tumor, and cervical lymph node metastases.

RESULTS

We identified tumor-associated expression signatures common to both primary tumors and metastases. Use of matching metastases revealed an additional 46 dysregulated genes associated solely with head and neck cancer metastasis. However, despite being metastasis-specific in our sample set, these 46 genes are concordant with genes previously discovered in primary tumors that metastasized.

CONCLUSIONS

Although our data and related studies show that most of the metastatic potential appears to be inherent to the primary tumor, they are also consistent with the notion that a limited number of additional clonal changes are necessary to yield the final metastatic cell(s), albeit in a variable temporal order.

Gene expression signatures that classify the mode of invasion of primary oral squamous cell carcinomas

To identify molecular signatures and establish a new diagnostic model for progressive oral squamous cell carcinoma (OSCC). Total RNAs were isolated from primary OSCCs from both node-positive and -negative patients and used in cDNA microarray analysis. To identify marker genes representing a malignant phenotype, their expression was further examined by quantitative reverse transcription-PCR (QRT-PCR) in 64 OSCC tissues. Using Fisher's linear discriminant analysis (LDA) fitted with a stepwise increment method, we created discriminatory predictor models. The stability of these models was examined using leave-one-out cross validation. Immunohistochemical analysis was performed. Among the 16,600 possible target cDNAs in the array analysis, 83 genes demonstrated significantly differential signals (>2-fold). We further identified 53 marker genes that can be implicated in the Yamamoto-Kohama's (YKs) mode of invasion for OSCCs (P < 0.06). Using LDA fitted with a stepwise increment method, we created four discriminatory predictor models based on 16- to 25-gene signatures which could best distinguish the five established grades of YKs mode of invasion. Leave-one out validation demonstrated that the stability of these models was 92-95%. For validation, we also examined an independent set of 13 primary OSCCs; the predictor models determined the invasion status from 77% to 100% (on average, 85%) fidelity with the pathological observations. TGM3 protein expression was markedly suppressed in highly invasive OSCCs. We reveal novel gene expression alterations during the progression of OSCC, and have constructed prediction models for the evaluation of the invasion status of these cancers.

Ribonucleotide reductase small subunit p53R2 promotes oral cancer invasion via the E-cadherin/beta-catenin pathway

The p53-inducible p53R2 gene has been isolated and shown to play a crucial role in DNA repair and synthesis after DNA damage. Moreover, the expression and activity of p53R2 has been reported to be associated with the anticancer agent resistance of human cancer cells. Previously, we reported that the presence of p53R2 expression was a predictive factor for regional lymph node metastasis in oral squamous cell carcinoma; however, the mechanism of cancer metastasis by p53R2 expression is still unclear. In the present study, we analyzed the correlation of p53R2 expression with cancer invasion in vitro. Three human oral cancer cell lines (SAS, HSC-3 and Ca9-22) were cultured, and the invasive potential of these cancer cells was evaluated using Matrigel invasion assay. To investigate the effect of p53R2 on cancer invasion, the down-regulation of p53R2 was examined by small interfering RNA (siRNA). Moreover, we examined the intracellular localization of cell adhesion molecules (E-cadherin and beta-catenin) in subcellular extractions of cancer cells by immunoblotting. The proteolytic activity of matrix metalloproteinases (MMPs) was assessed by gelatin zymography. Down-regulation of p53R2 significantly enhanced the invasion potential (p<0.01), and enhanced nuclear translocation of beta-catenin with loss of total cellular E-cadherin expression in p53 mutant cancer cells, but not in p53 wild-type cancer cells. These changes in the invasion index by p53R2 siRNA transfection were not accompanied by alterations in MMP activity and expression. These results suggested that the expression of p53R2 could be associated with the invasion of cancer cells, and indicated that p53R2 might promote cancer invasion via the E-cadherin/beta-catenin pathway without the alteration of MMP activity.

Overexpression and altered subcellular localization of autophagy-related 16-like 1 in human oral squamous-cell carcinoma: correlation with lymphovascular invasion and lymph-node metastasis

Autophagy is a dynamic process of subcellular degradation, which has recently sparked great interest because it is involved in various developmental processes and various diseases including cancer. Autophagy-related 16-like 1 is a component of a large protein complex essential for autophagosome formation. We previously applied proteomic methods to characterize differentially expressed proteins in oral squamous cell carcinoma cells and detected significantly high expression levels of autophagy-related 16-like 1 in oral squamous cell carcinoma-derived cell lines compared to human normal oral keratinocytes. In the current study, to further determine the potential involvement of autophagy-related 16-like 1 in oral squamous cell carcinoma, we evaluated the state of autophagy-related 16-like 1 protein expression in human oral premalignant lesions and primary oral squamous cell carcinomas, and correlated the results with clinicopathologic variables. Autophagy-related 16-like 1 immunoreaction was predominant in a variety of subcellular components of oral squamous cell carcinoma tissues, including the cytoplasm and plasma membrane of malignant cells (45% and 39%, respectively) and peritumoral and intratumoral stroma (52%), whereas all of the components in normal tissues had no or faint autophagy-related 16-like 1 expression. In addition, high stromal expression of autophagy-related 16-like 1 was associated significantly with lymphovascular invasion of tumor cells (P = .037) and positive lymph node status (P = .015). Furthermore, cytoplasmic and plasma membranous autophagy-related 16-like 1 were also expressed in abundance in the oral premalignant lesion cells (74% and 32%, respectively). Our finding suggests that dysregulation of autophagy-related 16-like 1 protein expression is a frequent and early event during oral carcinogenesis and could affect the malignant behavior of oral squamous cell carcinoma cells.

Activation of MAP kinase signaling through ERK5 but not ERK1 expression is associated with lymph node metastases in oral squamous cell carcinoma (OSCC)

In an attempt to further elucidate the pathomechanisms in oral squamous cell carcinoma (OSCC), gene expression profiling was performed using a whole-transcriptome chip that contains 35,035 gene-specific 70 mere oligonucleotides (Human OligoSet 4.0; Operon, Cologne, Germany) to a set of 35 primary OSCCs. Altogether, 7390 genes were found differentially expressed between OSCC tumor samples and oral mucosa. To characterize the major biologic processes in this tumor collection, MAPPFinder, a component of GenMAPP version 2.1, was applied to this data set to generate a statistically ranked list of molecular signaling pathways. Among others, cancer-related pathways, such as mitogen-activated protein (MAP) kinase signaling (z score = 4.6, P < .001), transforming growth factor-beta signaling (z score = 3.0, P = .015), and signaling pathways involved in apoptosis (z score = 2.1, P = .037), were found deregulated in the OSCC collection analyzed. Focusing on the MAP kinase signaling pathway, subsequent tissue microarray analyses by immunohistochemistry revealed an increase in protein expression of MAP kinase-related proteins ERK1 in 22.8% (48 of 209) and ERK5 in 27.4% (76 of 277), respectively. An association of high ERK5 but not of high ERK1 expression with advanced tumor stage and the presence of lymph node metastases was found (P = .008 and P = .016, respectively). Our analysis demonstrates the reliability of the combined approach of gene expression profiling, signaling pathway analyses, and tissue microarray analysis to detect novel distinct molecular aberrations in OSCC.

Examination of oral cancer biomarkers by tissue microarray analysis

OBJECTIVE

To validate the DNA microarray results on a subset of genes that could potentially serve as biomarkers of oral squamous cell carcinoma (OSCC) by examining their expression with an alternate quantitative method and by assessing their protein levels.

DESIGN

Based on DNA microarray data from our laboratory and data reported in the literature, we identified 6 potential biomarkers of OSCC to investigate further. We used quantitative real-time polymerase chain reaction to examine expression changes of CDH11, MMP3, SPARC, POSTN, TNC, and TGM3 in OSCC and histologically normal control tissues. We further examined validated markers at the protein level by immunohistochemical analysis of OSCC tissue microarray sections.

RESULTS

Quantitative real-time polymerase chain reaction analysis revealed upregulation of CDH11, SPARC, POSTN, and TNC gene expression and decreased TGM3 expression in OSCC tissue compared with control tissue; MMP3 was not found to be differentially expressed. In tissue microarray immunohistochemical analyses, SPARC (secreted protein, acidic, rich in cysteine), periostin, and tenascin C exhibited increased protein expression in tumor tissue compared with control tissue, and their expression was primarily localized within tumor-associated stroma rather than tumor epithelium. Conversely, transglutaminase 3 protein expression was found only within keratinocytes in control tissue and was significantly downregulated in cancer cells.

CONCLUSIONS

Of 6 potential gene markers of OSCC, initially identified by DNA microarray analyses, differential expression of CDH11, SPARC, POSTN, TNC, and TGM3 were validated by quantitative real-time polymerase chain reaction. Differential expression and localization of proteins encoded by SPARC, POSTN, TNC, and TGM3 were clearly shown by tissue microarray immunohistochemical analysis.

Differential gene expression signature between primary and metastatic head and neck squamous cell carcinoma

Head and neck squamous cell carcinoma (HNSCC) is a world-wide malignancy. This study aimed to identify differential gene expression associated with the progression of disease from primary to metastatic HNSCC. Microdissection retrieved pure epithelial cells from paired primary tumours and cervical lymph node metastasis. cDNA microarray analysis and algorithm grouping identified differential mRNA expression of 301 genes. Quantitative reverse transcription-polymerase chain reaction analysis clarified the up-regulation of CCL19, CR2, EGR2, FUCA1, RGS1, and SELL, as well as the down-regulation of IGFBP6 and KLK8 in nodal metastasis compared to primary tumours. Immunohistochemistry confirmed the up-regulation of SELL and down-regulation of IGFBP6 in nodal metastasis relative to primary tumours. Interestingly, primary tumours exhibiting higher FUCA1 and SELL expression were associated with significantly worse patient survival. In OECM-1 HNSCC cells, inhibition of proliferation, migration, and anchorage-independent growth was noted following knockdown of SELL expression. In SAS HNSCC cells, expression of exogenous SELL resulted in increased invasion, anchorage-independent growth, and xenographic tumourigenesis in nude mice. Knockdown of FUCA1 and treatment with IGFBP6 inhibited the migration of OECM-1 cells. Knockdown of RGS1 inhibited the anchorage-independent growth of SAS cells. Our results provide a useful gene signature profile describing the factors underlying the metastasis of HNSCC to cervical lymph nodes, which may be beneficial for the treatment of HNSCC metastasis.

Endothelial cells enhance tumor cell invasion through a crosstalk mediated by CXC chemokine signaling

Field cancerization involves the lateral spread of premalignant or malignant disease and contributes to the recurrence of head and neck tumors. The overall hypothesis underlying this work is that endothelial cells actively participate in tumor cell invasion by secreting chemokines and creating a chemotactic gradient for tumor cells. Here we demonstrate that conditioned medium from head and neck tumor cells enhance Bcl-2 expression in neovascular endothelial cells. Oral squamous cell carcinoma-3 (OSCC3) and Kaposi's sarcoma (SLK) show enhanced invasiveness when cocultured with pools of human dermal microvascular endothelial cells stably expressing Bcl-2 (HDMEC-Bcl-2), compared to cocultures with empty vector controls (HDMEC-LXSN). Xenografted OSCC3 tumors vascularized with HDMEC-Bcl-2 presented higher local invasion than OSCC3 tumors vascularized with control HDMEC-LXSN. CXCL1 and CXCL8 were upregulated in primary endothelial cells exposed to vascular endothelial growth factor (VEGF), as well as in HDMEC-Bcl-2. Notably, blockade of CXCR2 signaling, but not CXCR1, inhibited OSCC3 and SLK invasion toward endothelial cells. These data demonstrate that CXC chemokines secreted by endothelial cells induce tumor cell invasion and suggest that the process of lateral spread of tumor cells observed in field cancerization is guided by chemotactic signals that originated from endothelial cells.

Transcriptomic dissection of tongue squamous cell carcinoma

Background

The head and neck/oral squamous cell carcinoma (HNOSCC) is a diverse group of cancers, which develop from many different anatomic sites and are associated with different risk factors and genetic characteristics. The oral tongue squamous cell carcinoma (OTSCC) is one of the most common types of HNOSCC. It is significantly more aggressive than other forms of HNOSCC, in terms of local invasion and spread. In this study, we aim to identify specific transcriptomic signatures that associated with OTSCC.

Results

Genome-wide transcriptomic profiles were obtained for 53 primary OTSCCs and 22 matching normal tissues. Genes that exhibit statistically significant differences in expression between OTSCCs and normal were identified. These include up-regulated genes (MMP1, MMP10, MMP3, MMP12, PTHLH, INHBA, LAMC2, IL8, KRT17, COL1A2, IFI6, ISG15, PLAU, GREM1, MMP9, IFI44, CXCL1), and down-regulated genes (KRT4, MAL, CRNN, SCEL, CRISP3, SPINK5, CLCA4, ADH1B, P11, TGM3, RHCG, PPP1R3C, CEACAM7, HPGD, CFD, ABCA8, CLU, CYP3A5). The expressional difference of IL8 and MMP9 were further validated by real-time quantitative RT-PCR and immunohistochemistry. The Gene Ontology analysis suggested a number of altered biological processes in OTSCCs, including enhancements in phosphate transport, collagen catabolism, I-kappaB kinase/NF-kappaB signaling cascade, extracellular matrix organization and biogenesis, chemotaxis, as well as suppressions of superoxide release, hydrogen peroxide metabolism, cellular response to hydrogen peroxide, keratinization, and keratinocyte differentiation in OTSCCs.

Conclusion

In summary, our study provided a transcriptomic signature for OTSCC that may lead to a diagnosis or screen tool and provide the foundation for further functional validation of these specific candidate genes for OTSCC.

Heterogeneity of gene expression profiles in head and neck cancer

BACKGROUND

Results of gene expression profiling studies from different institutes often lack consistency. This could be due to the use of different microarray platforms and protocols, or to intratumoral heterogeneity in mRNA expression. The aim of our study was to quantify intratumoral heterogeneity in head and neck cancer.

METHODS

Forty-four fresh frozen biopsies were taken from 22 patients, 2 per tumor. RNA was extracted, tested for quality, amplified, labeled, and hybridized to a 35k oligoarray.

RESULTS

Unsupervised clustering analyses using all genes, the most variable genes, or random gene sets showed that 80% to 90% of biopsy pairs clustered together. A within-pair-between-pair scatter ratio analysis showed that the similarity between matching pairs was significantly greater than that between random pairs (p <.00001).

CONCLUSIONS

Two biopsies from the same tumor show far greater similarity in gene expression than biopsies from different tumors, supporting the use of 1 biopsy for expression profiling.

Lymphatic metastasis in breast cancer: importance and new insights into cellular and molecular mechanisms

Lymph node metastasis is the main prognosis factor in a number of malignancies, including breast carcinomas. The means by which lymph node metastases arise is not fully understood, and many questions remain about their importance in the further spread of breast cancer. Nevertheless, a number of key cellular and molecular mechanisms of lymphatic metastasis have been identified. These include induction of intra- or peri-tumoral lymphangiogenesis or co-option of existing lymphatic vessels to allow tumour cells to enter the lymphatics, although it remains to be established whether this is primarily an active or passive process. Gene expression microarrays and functional studies in vitro and in vivo, together with detailed clinical observations have identified a number of molecules that can play a role in the genesis of lymph node metastases. These include the well-recognised lymphangiogenic cytokines VEGF-C and VEGF-D as well as chemokine-receptor interactions, integrins and downstream signalling pathways. This paper briefly reviews current clinical and experimental evidence for the underlying mechanisms and significance of lymphatic metastasis in breast cancer and highlights questions that still need to be addressed.

Gene expression profiling to predict outcome after chemoradiation in head and neck cancer

PURPOSE

The goal of the present study was to improve prediction of outcome after chemoradiation in advanced head and neck cancer using gene expression analysis.

MATERIALS AND METHODS

We collected 92 biopsies from untreated head and neck cancer patients subsequently given cisplatin-based chemoradiation (RADPLAT) for advanced squamous cell carcinomas (HNSCC). After RNA extraction and labeling, we performed dye swap experiments using 35k oligo-microarrays. Supervised analyses were performed to create classifiers to predict locoregional control and disease recurrence. Published gene sets with prognostic value in other studies were also tested.

RESULTS

Using supervised classification on the whole series, gene sets separating good and poor outcome could be found for all end points. However, when splitting tumors into training and validation groups, no robust classifiers could be found. Using Gene Set Enrichment analysis, several gene sets were found to be enriched in locoregional recurrences, although with high false-discovery rates. Previously published signatures for radiosensitivity, hypoxia, proliferation, "wound," stem cells, and chromosomal instability were not significantly correlated with outcome. However, a recently published signature for HNSCC defining a "high-risk" group was shown to be predictive for locoregional control in our dataset.

CONCLUSION

Gene sets can be found with predictive potential for locoregional control after combined radiation and chemotherapy in HNSCC. How treatment-specific these gene sets are needs further study.

High expression of DNA repair pathways is associated with metastasis in melanoma patients

We have identified a gene-profile signature for human primary malignant melanoma associated with metastasis to distant sites and poor prognosis. We analyse the differential gene expression by looking at whole biological pathways rather than individual genes. Among the most significant pathways associated with progression to metastasis, we found the DNA replication (P=10(-14)) and the DNA repair pathways (P=10(-16)). We concentrated our analysis on DNA repair and found that 48 genes of this category, among a list of 234 genes, are associated with metastatic progression. These genes belong essentially to the pathways allowing recovery of stalled replication forks due to spontaneous blockage or induced DNA lesions. Because almost all these differentially expressed repair genes were overexpressed in primary tumors with bad prognosis, we speculate that primary melanoma cells that will metastasize try to replicate in a fast and error-free mode. In contrast to the progression from melanocytes to primary melanoma, genetic stability appears to be necessary for a melanoma cell to give rise to distant metastasis. This overexpression of repair genes explains nicely the extraordinary resistance of metastatic melanoma to chemo- and radio-therapy. Our results may open a new avenue for the discovery of drugs active on human metastatic melanoma.

Metastasis: the seed and soil theory gains identity

The metastatic spread of tumor cells to distant sites represents the major cause of cancer-related deaths. Cancer metastasis involves a series of complex interactions between tumor cells and microenvironment that influence its biological effectiveness and facilitate tumor cell arrest to distant organs. More than a century since Paget developed the theory of seed and soil, the enigma of tissue specificity observed in metastatic colonization of tumor cells begins to unfold itself. The advent of new technologies has led to the discovery of novel molecules and pathways that confer metastasis-associated properties to the cancer cells, mediating organ specificity and unique genetic signatures have been developed using microarray studies. Future clinical studies and new antimetastatic compounds aiming to improve survival of patients with metastasis will most probably be based on these signatures. This review summarizes the plethora of old and new molecules that are strongly correlated with organ-specific metastases and which provide now an identity to the theory of seed and soil.

Metastasis of squamous cell carcinoma of the oral tongue

Squamous cell carcinoma of the oral tongue (SCCOT) is one of the most prevalent tumors of the head and neck region. Despite advances in treatment, the survival of patients with SCCOT has not significantly improved over the past several decades. Most frequently, treatment failure takes the form of local and regional recurrences, but as disease control in these areas improves, SCCOT treatment failures are occurring more often as distant metastasis. The presence of cervical lymph node metastasis is the most reliable adverse prognostic factor in patients with SCCOT, and extracapsular spread (ECS) of cervical lymph nodes metastasis is a particularly reliable predictor of regional and distant recurrence and death from disease. Decisions regarding the elective and therapeutic management of cervical lymph node metastases are made mainly on clinical grounds as we cannot always predict cervical lymph node metastasis from the size and extent of invasion of the primary tumors. Therefore, the treatment of these metastases in the management of SCCOT remains controversial. The promise of basing treatment decisions on biomarkers has yet to be fully realized because of our poor understanding of the mechanisms of regional and distant metastases of SCCOT. Here we summarize the current status of investigations of SCCOT metastases and the potential of these studies to have a positive impact on the clinical management of SCCOT in the future.

Tumor-specific genetic expression profile of metastatic oral squamous cell carcinoma

BACKGROUND

Metastasis is the most important predictor of survival in patients with oral squamous cell carcinoma (OSCC). We tested the hypothesis that there is a genetic expression profile associated with OSCC metastasis.

METHODS

We obtained samples from 6 OSCC node-positive primary tumors and their matched metastatic lymph nodes, and 5 OSCC node-negative primary tumors. Using laser capture microdissection, we isolated OSCC cells from metastatic lymph nodes and compared them with those from matched primary tumors and unmatched node-negative primary tumors using Affymetrix Human Genome Focus arrays.

RESULTS

Comparison of tumor cells from the lymph nodes with those from the unmatched, node-negative primary tumors revealed differential expression of 160 genes. Hierarchical clustering and principal component analysis using this 160-gene set showed that the node-negative samples were distinguishable from both, node-positive primary tumors and tumors in the lymph nodes. Many of the expression changes found in the metastatic cells from the lymph nodes were also found in the node-positive primary tumors. Immunohistochemical analysis for transglutaminase-3 and keratin 16 confirmed the differential genetic expression for these genes.

CONCLUSION

These preliminary results suggest that there may be a metastatic gene expression profile present in node-positive primary OSCC.

Classification of heterogeneous microarray data by maximum entropy kernel

Background

There is a large amount of microarray data accumulating in public databases, providing various data waiting to be analyzed jointly. Powerful kernel-based methods are commonly used in microarray analyses with support vector machines (SVMs) to approach a wide range of classification problems. However, the standard vectorial data kernel family (linear, RBF, etc.) that takes vectorial data as input, often fails in prediction if the data come from different platforms or laboratories, due to the low gene overlaps or consistencies between the different datasets.

Results

We introduce a new type of kernel called maximum entropy (ME) kernel, which has no pre-defined function but is generated by kernel entropy maximization with sample distance matrices as constraints, into the field of SVM classification of microarray data. We assessed the performance of the ME kernel with three different data: heterogeneous kidney carcinoma, noise-introduced leukemia, and heterogeneous oral cavity carcinoma metastasis data. The results clearly show that the ME kernel is very robust for heterogeneous data containing missing values and high-noise, and gives higher prediction accuracies than the standard kernels, namely, linear, polynomial and RBF.

Conclusion

The results demonstrate its utility in effectively analyzing promiscuous microarray data of rare specimens, e.g., minor diseases or species, that present difficulty in compiling homogeneous data in a single laboratory.

Molecular biology of oral cavity squamous cell carcinoma

Significant advances have been made in understanding the mechanisms that contribute to carcinogenesis in OCSCC. This progress has led to the development of therapeutic strategies that target dysregulated processes in the tumor microenvironment (Fig. 11) [72]. The introduction of angiogenesis inhibitors, growth factor receptor tyrosine kinase inhibitors, and cell cycle regulators into clinical trials for the management of OCSCC has resulted from the great strides made in the understanding of tumor biology. It is important for those caring for patients who have OCSCC to have a firm background in tumor biology, because many future therapies will be based on this complex panorama of cellular physiology.

Overexpression of galectin-1 at the tumor invasion front is associated with poor prognosis in early-stage oral squamous cell carcinoma

Metastasis is a final and eventually fatal step in the progression of oral squamous cell carcinoma (OSCC) and typically accompanies a large primary tumor. Metastasis may also present from a small primary tumor and progress rapidly; therefore, early diagnosis is important for patients with small primary tumors. Galectin-1 is one significantly upregulated tumor-associated protein in many neoplasms. To determine the clinical significance of galectin-1, we analyzed its expression in clinical samples by immunohistochemistry and reverse transcription-quantitative polymerase chain reaction assay. Galectin-1 protein was significantly overexpressed in the tumor-associated stroma as well as the invasion front during early oral carcinogenesis (P<0.05). During the metastatic stage, the only significant immunoreactivity was at the tumor invasion front (P<0.05). Although galectin-1 mRNA was not significantly upregulated in the whole cancerous tissue, it was upregulated in stromal parts during early-stage OSCC and in epithelial parts at the metastatic stage. Survival analysis and a Cox's proportional hazards model showed that synchronous upregulation of galectin-1 protein and mRNA was correlated with worse disease-free survival in early-stage OSCC (P=0.024 and P=0.047, respectively). Our findings suggest that galectin-1 upregulation at the tumor invasion front might be a predictor of early metastasis in oral carcinogenesis.

Metastasis: recent discoveries and novel treatment strategies

Most cancer deaths are due to the development of metastases, hence the most important improvements in morbidity and mortality will result from prevention (or elimination) of such disseminated disease. Some would argue that treatments directed against metastasis are too late because cells have already escaped from the primary tumour. Such an assertion runs contrary to the significant but (for many common adult cancers) fairly modest improvements in survival following the use of adjuvant radiation and chemotherapy designed to eliminate disseminated cells after surgical removal of the primary tumour. Nonetheless, the debate raises important issues concerning the accurate early identification of clonogenic, metastatic cells, the discovery of novel, tractable targets for therapy, and the monitoring of minimal residual disease. We focus on recent findings regarding intrinsic and extrinsic molecular mechanisms controlling metastasis that determine how, when, and where cancers metastasise, and their implications for patient management in the 21st century.

A 10-gene classifier for distinguishing head and neck squamous cell carcinoma and lung squamous cell carcinoma

PURPOSE

The risk of developing metastatic squamous cell carcinoma for patients with head and neck squamous cell carcinoma (HNSCC) is very high. Because these patients are often heavy tobacco users, they are also at risk for developing a second primary cancer, with squamous cell carcinoma of the lung (LSCC) being the most common. The distinction between a lung metastasis and a primary LSCC is currently based on certain clinical and histologic criteria, although the accuracy of this approach remains in question.

EXPERIMENTAL DESIGN

Gene expression patterns derived from 28 patients with HNSCC or LSCC from a single center were analyzed using penalized discriminant analysis. Validation was done on previously published data for 134 total subjects from four independent Affymetrix data sets.

RESULTS

We identified a panel of 10 genes (CXCL13, COL6A2, SFTPB, KRT14, TSPYL5, TMP3, KLK10, MMP1, GAS1, and MYH2) that accurately distinguished these two tumor types. This 10-gene classifier was validated on 122 subjects derived from four independent data sets and an average accuracy of 96% was shown. Gene expression values were validated by quantitative reverse transcription-PCR derived on 12 independent samples (seven HNSCC and five LSCC). The 10-gene classifier was also used to determine the site of origin of 12 lung lesions from patients with prior HNSCC.

CONCLUSIONS

The results suggest that penalized discriminant analysis using these 10 genes will be highly accurate in determining the origin of squamous cell carcinomas in the lungs of patients with previous head and neck malignancies.

Global expression-based classification of lymph node metastasis and extracapsular spread of oral tongue squamous cell carcinoma

Regional lymph node metastasis is a critical event in oral tongue squamous cell carcinoma (OTSCC) progression. The identification of biomarkers associated with the metastatic process would provide critical prognostic information to facilitate clinical decision making for improved management of OTSCC patients. Global expressional profiles were obtained for 25 primary OTSCCs, where 11 cases showed lymph node metastasis (pN+) histologically and 14 cases were nonmetastatic (pN-). Seven of pN+ cases also exhibited extracapsular spread (ECS) of metastatic nodes. Multiple expression indices were used to generate signature gene sets for pN+/- and ECS+/- cases. Selected genes from signature gene sets were validated using quantitative reverse transcription-polymerase chain reaction (qRT-PCR). The classification powers of these genes were then evaluated using a logistic model, receiver operating characteristic curve analysis, and leave-one-out cross-validation. qRT-PCR validation data showed that differences at RNA levels are either statistically significant (P < .05) or suggestive (P < .1) for six of eight genes tested (BMP2, CTTN, EEF1A1, GTSE1, MMP9, and EGFR) for pN+/- cases, and for five of eight genes tested (BMP2, CTTN, EEF1A1, MMP9, and EGFR) for ECS+/- cases. Logistic models with specific combinations of genes (CTTN+MMP9+EGFR for pN and CTTN+EEF1A1+MMP9 for ECS) achieved perfect specificity and sensitivity. Leave-one-out cross-validation showed overall accuracy rates of 85% for both pN and ECS prediction models. Our results demonstrated that the pN and the ECS of OTSCCs can be predicted by gene expression analyses of primary tumors.

Identification of a gene signature for rapid screening of oral squamous cell carcinoma

PURPOSE

Oral cancer is a major health problem worldwide and in the U.S. The 5-year survival rate for oral cancer has not improved significantly over the past 20 years and remains at approximately 50%. Patients diagnosed at an early stage of the disease typically have an 80% chance for cure and functional outcome, however, most patients are identified when the cancer is advanced. Thus, a convenient and an accurate way to detect oral cancer early will decrease patient morbidity and mortality. The ability to noninvasively monitor oral cancer onset, progression, and treatment outcomes requires two prerequisites: identification of specific biomarkers for oral cancers as well as noninvasive access to and monitoring of these biomarkers that could be conducted at the point of care (i.e., practitioner's or dentist's office) by minimally trained personnel.

EXPERIMENTAL DESIGN

Here, we show that DNA microarray gene expression profiling of matched tumor and normal specimens can identify distinct anatomic site expression patterns and a highly significant gene signature distinguishing normal from oral squamous cell carcinoma (OSCC) tissue.

RESULTS

Using a supervised learning algorithm, we generated a 25-gene signature for OSCC that can classify normal and OSCC specimens. This 25-gene molecular predictor was 96% accurate on cross-validation, averaging 87% accuracy using three independent validation test sets and failing to predict non-oral tumors.

CONCLUSION

Identification and validation of this tissue-specific 25-gene molecular predictor in this report is our first step towards developing a new, noninvasive, microfluidic-based diagnostic technology for mass screening, diagnosis, and treatment of pre-OSCC and OSCC.

Pathway and gene-set activation measurement from mRNA expression data: the tissue distribution of human pathways

BACKGROUND

Interpretation of lists of genes or proteins with altered expression is a critical and time-consuming part of microarray and proteomics research, but relatively little attention has been paid to methods for extracting biological meaning from these output lists. One powerful approach is to examine the expression of predefined biological pathways and gene sets, such as metabolic and signaling pathways and macromolecular complexes. Although many methods for measuring pathway expression have been proposed, a systematic analysis of the performance of multiple methods over multiple independent data sets has not previously been reported.

RESULTS

Five different measures of pathway expression were compared in an analysis of nine publicly available mRNA expression data sets. The relative sensitivity of the metrics varied greatly across data sets, and the biological pathways identified for each data set are also dependent on the choice of pathway activation metric. In addition, we show that removing incoherent pathways prior to analysis improves specificity. Finally, we create and analyze a public map of pathway expression in human tissues by gene-set analysis of a large compendium of human expression data.

CONCLUSION

We show that both the detection sensitivity and identity of pathways significantly perturbed in a microarray experiment are highly dependent on the analysis methods used and how incoherent pathways are treated. Analysts should thus consider using multiple approaches to test the robustness of their biological interpretations. We also provide a comprehensive picture of the tissue distribution of human gene pathways and a useful public archive of human pathway expression data.

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.

The extracellular matrix in oral squamous cell carcinoma: friend or foe?

Oral squamous cell carcinoma is a disfiguring, highly invasive and metastatic cancer. Despite advances in detection and therapy, many patients will continue to face a poor prognosis. It is well established that the predominate factor determining overall survival in patients with oral squamous cell carcinoma is lymph node involvement. Tumor growth and progression to invasive cancer requires tumor cell interactions with the extracellular matrix. An understanding of how the extracellular matrix influences tumor development and invasion is fundamental in the development of new prognostic indicators and treatment strategies for oral squamous cell carcinoma. In this review, we summarize how changes in the extracellular matrix contribute to oral cancer development.

Molecular biology of squamous cell carcinoma of the head and neck

Squamous cell carcinoma of the head and neck (HNSCC) is a heterogeneous but largely preventable disease with complex molecular abnormalities. It arises from a premalignant progenitor followed by outgrowth of clonal populations associated with cumulative genetic alterations and phenotypic progression to invasive malignancy. These genetic alterations result in inactivation of multiple tumour suppressor genes and activation of proto-oncogenes, including p16(ink4A), p53, cyclin D1, p14(ARF), FHIT, RASSF1A, epidermal growth factor receptor (EGFR), and Rb. Intramucosal migration and clonal expansion of transformed cells with formation of abnormal genetic fields appear to be responsible for local recurrences and development of second primary tumours.

Genomic analysis defines a cancer-specific gene expression signature for human squamous cell carcinoma and distinguishes malignant hyperproliferation from benign hyperplasia

Using high-density oligonucleotide arrays, we measured expression of >12,000 genes in surgical excisions of invasive human squamous cell carcinomas (SCCs) versus site-matched control skin. This analysis defined >1,900 genes with altered expression in SCCs that were statistically different from controls. As SCCs are composed of epithelial cells, which are both hyperplastic and invasive, we sought to define gene sets associated with these biologic processes by comparing gene expression to psoriasis vulgaris, which is a condition of benign keratinocyte hyperplasia without invasiveness or pre-malignant potential. Through this analysis, we found genes that were commonly upregulated in both conditions and unique genes with increased expression in SCCs. Differential gene regulation in these two conditions was confirmed by real-time reverse transcription-PCR and immunohistochemistry. We found that benign hyperplasia is associated with upregulation of genes including DEFB4 (defensin B4), SERPINB3 (serine proteinase inhibitor, member 3), STAT1 (signal transducer and activator of transcription 1), K16 (keratin 16), CEACAMs (carcinoembryonic antigen-related cell adhesion molecules), and WNT 5A (wingless-type MMTV integration site family, member 5A). WNT receptor frizzled homolog 6 (FZD6) and prostaglandin-metabolizing enzyme hydroxyprostaglandin dehydrogenase were increased in SCC alone. Growth factor pleiotrophin (PTN) was expressed at higher levels in non-tumor-bearing skin adjacent to excised SCC. SCC was further characterized by upregulation of matrix metalloproteinases 1, 10, and 13, cathepsin L2, cystatin E/M as well as STAT3 and microseminoprotein, beta (MSMB), and downregulation of inducible nitric oxide synthase, granzyme B, CD8, and CD83. The current study defines a unique gene expression signature for cutaneous SCC in humans and suggests potential roles for WNT, FZD, and PTN in the pathogenesis of SCC.

Disease mechanism and biomarkers of oral squamous cell carcinoma

PURPOSE OF REVIEW

This review focuses on oral cancer disease mechanisms and discusses ongoing research to identify molecular signatures or biomarkers for oral cancer. Other areas covered include the analysis, validation, and predictive value of these markers.

RECENT FINDINGS

During the past years, progress has been made in the oral cancer genetic markers field, which includes alterations of the p53 tumor suppressor protein, the inactivation of cyclin dependant kinase inhibitors (e.g. p16) and the overexpression of the epidermal growth factor receptor. Many of these markers are thought to have potential clinical interest, yet few of them are being used in a clinical setting for oral cancer management. The particular modifications that characterize each step of oral cancer progression can now be profiled by several high throughput discovery techniques. Genomic and proteomic studies of oral cancer tissues, plasma, and saliva of oral cancer patients, have allowed the identification of several promising cancer signatures.

SUMMARY

Important progress has been made in the molecular understanding of oral cancer and its application for diagnosis, prognosis and treatment. The increased efforts in translational research will result in earlier diagnosis of oral cancer, better knowledge of prognostic factors, and the development of targeted treatment regimens based on patients' clinical and biological characteristics at presentation.

Chemokine receptors in head and neck cancer: association with metastatic spread and regulation during chemotherapy

Head and neck carcinomas are histologically and clinically heterogeneous. While squamous cell carcinomas (SCC) are characterized by lymphogenous spread, adenoid cystic carcinomas (ACC) disseminate preferentially hematogenously. To study cellular and molecular mechanisms of organ-specific metastasis, we used SCC and ACC cell lines and tumor tissues, obtained from patients with primary or metastatic disease. Comprehensive analysis at the mRNA and protein level of human chemokine receptors showed that SCC and ACC cells exhibited distinct and nonrandom expression profiles for these receptors. SCC predominantly expressed receptors for chemokines homeostatically expressed in lymph nodes, including CC chemokine receptor (CCR) 7 and CXC chemokine receptor (CXCR)5. No difference in expression of chemokine receptors was seen in primary SCC and corresponding lymph node metastases. In contrast to SCC, ACC cells primarily expressed CXCR4. In chemotaxis assays, ACC cells were responsive to CXCL12, the ligand for CXCR4. Exposure of ACC cells to cisplatin resulted in upregulation of CXCR4 on the cell surface, which was repressed by the transcriptional inhibitor, alpha-amanitin. Treatment of ACC cells with CXCL12 resulted in the activation of Akt and ERK1/2 pathways. Furthermore, CXCL12 suppressed the rate of apoptosis induced by cisplatin in ACC cells, suggesting that signaling via CXCR4 may be part of a tumor cell survival program. Discrimination of the chemokine receptor profile in SCC and ACC in vitro and in tissues provided insights into their distinct biologic and clinical characteristics as well as indications that chemokine receptors might serve as future therapeutic targets in these malignancies.

Molecular predictors of clinical outcome in patients with head and neck squamous cell carcinoma

Head and neck squamous cell carcinoma (HNSCC) involves the upper aerodigestive tract and can destroy the structure and function of organs involved in voice, speech, taste, smell and hearing, as well as vital structures necessary for survival. HNSCC has long been a treatment challenge because of the high rate of recurrences and of advanced disease at the time of diagnosis. Molecular identification of tissue biomarkers in diagnostic biopsy specimens may not only identify patients at risk for developing HNSCC but may also select patients that may benefit from more aggressive treatment modalities. Several biomarkers studied to date such as the proteins p53, cyclin D1, p16, Cox-2 enzyme, epidermal growth factor and vascular endothelial growth factor receptors, matrix metalloproteinases and the Fhit marker for genomic instability could be manipulated for the therapeutic benefit of these patients. This review presents the most updated information on molecular biomarkers with the greatest prognostic potential in HNSCC and discusses some factors that contribute to the controversy concerning their prognostic importance.

Growth factor-sensitive molecular targets identified in primary and metastatic head and neck squamous cell carcinoma using microarray analysis

Polypeptide growth factors play key roles in the processes of cell migration and invasion. In this study, we have used cDNA microarrays to identify target genes whose expression is differentially modulated by the growth factors TGFbeta and EGF. HN4 and HN12 cell lines, established from primary tumor and a lymph node metastasis arising in one patient with head and neck squamous cell carcinoma, were treated with 2nM EGF or 50pM TGFbeta for 24h and extracted RNA was used to prepare labeled cDNAs which were hybridized to NCI UniGem 2.0 cDNA microarrays containing 9128 features. Results revealed constitutive overexpression of 41 genes and underexpression of 109 genes in metastatic HN12 compared to HN4 under conditions of serum withdrawal. Furthermore, TGFbeta treatment resulted in relative upregulation of 53 genes and downregulation of 91 genes in HN12 compared with HN4, whereas cells treated with EGF showed relative upregulation of 67 genes and downregulation of 113 genes. Partial overlap was found between TGFbeta and EGF-modulated gene sets. Results were verified for a subset of each category using quantitative PCR, western blotting and zymography. The data indicate that TGFbeta and EGF differentially affect gene expression in primary and metastatic HNSCC cells, and likely contribute to the invasive properties of metastatic cells through regulation of both common and specific mediators for each growth factor.

Genetic expression profiles and biologic pathway alterations in head and neck squamous cell carcinoma

Head and neck squamous cell carcinoma (HNSCC) is associated with considerable mortality and morbidity and is a major public health concern worldwide. To date, > 20 studies incorporating DNA microarray analyses have examined genomewide genetic expression changes associated with the development of HNSCC. The authors identified published reports of genetic expression profiles of HNSCC by Medline database search. They performed a review of the reports to identify genes that have been found repeatedly to exhibit substantially altered expression in HNSCC. Genes with altered expression were subsequently examined in the context of defined biologic systems with the use of GenMapp 2.0 pathway analysis software. Genes most commonly found to exhibit altered expression were those encoding for cytoskeletal and extracellular matrix proteins, inflammatory mediators, proteins involved in epidermal differentiation, and cell adhesion molecules. Results of GenMapp 2.0 analysis suggested global down-regulation of genes that encode for ribosomal proteins and enzymes in the cholesterol biosynthesis pathway; and up-regulation of genes that encode for matrix metalloproteinases and genes that bear on the inflammatory response. The review indicated that there are several genes and pathways that exhibit substantially altered expression in cancerous versus noncancerous states across studies. Further investigation into the genomic, proteomic, and functional consequences of these gene expression alterations may provide insight into the pathophysiology of HNSCC.