Chung-Ji Liu

Direct regulation of TWIST by HIF-1alpha promotes metastasis.

Stabilization of the hypoxia-inducible factor-1α (HIF-1α) transcription complex, caused by intratumoural hypoxia, promotes tumour progression and metastasis, leading to treatment failure and mortality in different types of human cancers. The transcription factor TWIST is a master regulator of gastrulation and mesoderm-specification and was implicated recently as an essential mediator of cancer metastasis. Notably, HIF-1α- and TWIST-null mice show similarities in their phenotypes. Here, we have shown that hypoxia or overexpression of HIF-1α promotes epithelial–mesenchymal transition (EMT) and metastastic phenotypes. We also found that HIF-1 regulates the expression of TWIST by binding directly to the hypoxia-response element (HRE) in the TWIST proximal promoter. However, siRNA-mediated repression of TWIST in HIF-1α-overexpressing or hypoxic cells reversed EMT and metastastic phenotypes. Co-expression of HIF-1α, TWIST and Snail in primary tumours of patients with head and neck cancers correlated with metastasis and the worst prognosis. These results provide evidence of a key signalling pathway involving HIF-1α and TWIST that promotes metastasis in response to intratumoural hypoxia.

Overexpression of NBS1 induces epithelial-mesenchymal transition and co-expression of NBS1 and Snail predicts metastasis of head and neck cancer.

Major causes of head and neck squamous cell carcinoma (HNSCC)-related deaths are cervical node and distant metastasis. We previously demonstrated that overexpression of the DNA double-strand break repair protein Nijmegen breakage syndrome 1 (NBS1) is a prognostic marker of advanced HNSCCs. Epithelial-mesenchymal transition (EMT) was demonstrated to be the major mechanism responsible for mediating invasiveness and metastasis of late-stage cancers. We therefore investigated the role of NBS1 overexpression in mediating EMT and metastasis. NBS1 overexpression was associated with metastasis of HNSCC patients using tissue microarray–immunohistochemistry approach. Induction of EMT was observed in an NBS1-overexpressing HNSCC cell line (FADUNBS), whereas short-interference RNA (siRNA)-mediated repression of endogenous NBS1 reversed the shift of EMT markers. Increased migration/invasiveness of FADUNBS was shown by in vitro and in vivo assays. NBS1 overexpression upregulated the expression of an EMT regulator Snail and its downstream target matrix metalloproteinase-2. EMT phenotypes and increased migration/invasiveness of FADUNBS cells were reversed by siRNA-mediated repression of Snail expression or a phosphatidylinositol 3-kinase-specific inhibitor. In HNSCC samples, co-expression of NBS1/Snail in primary tumors correlated with metastasis and the worst prognosis. These results indicate that NBS1 overexpression induces EMT through the upregulation of Snail expression, and co-expression of NBS1/Snail predicts metastasis in HNSCCs.

Exploiting salivary miR-31 as a clinical biomarker of oral squamous cell carcinoma

Oral carcinoma is an important malignancy throughout the world. MicroRNAs (miRNAs) are endogenously expressed, non‐coding RNAs that regulate post‐transcriptional levels of targeted mRNAs. MiRNA‐31(miR‐31) is significantly upregulated in oral carcinoma tissues and plays oncogenic roles in oral carcinogenesis.

miR-24 up-regulation in oral carcinoma: Positive association from clinical and in vitro analysis

MicroRNAs (miRNAs) play important roles in neoplastic process. miR-24 is localized on chromosome 9q22 and 19p13, regions frequently altered in oral squamous cell carcinoma (OSCC). This study showed that miR-24 was up-regulated in OSCC tissues relative to control samples. In addition, the plasma levels of miR-24 in OSCC patients were significantly higher than in control individuals. miR-24 expression was also higher in OSCC cell lines relative to normal oral keratinocytes. Experiments blocking miR-24 and using exogenous miR-24 expression indicated that miR-24 contributes to the growth of OSCC cells and that miR-24 may target p57. This study suggests that miR-24 is involved in the regulation of OSCC growth and that the miR-24s level in plasma may be validatable as a tumor marker for OSCC patients.

The Epithelial-Mesenchymal Transition Mediator S100A4 Maintains Cancer-Initiating Cells in Head and Neck Cancers

Cancer-initiating cells (CIC) comprise a rare subpopulation of cells in tumors that are proposed to be responsible for tumor growth. Starting from CICs identified in head and neck squamous cell carcinomas (HNSCC), termed head and neck cancer-initiating cells (HN-CIC), we determined as a candidate stemness-maintaining molecule for HN-CICs the proinflammatory mediator S100A4, which is also known to be an inducer of epithelial-mesenchymal transition. S100A4 knockdown in HN-CICs reduced their self-renewal capability and their stemness and tumorigenic properties, both in vitro and in vivo. Conversely, S100A4 overexpression in HNSCC cells enhanced their stem cell properties. Mechanistic investigations indicated that attenuation of endogenous S100A4 levels in HNSCC cells caused downregulation of Notch2 and PI3K (phosphoinositide 3-kinase)/pAKT along with upregulation of PTEN, consistent with biological findings. Immunohistochemical analysis of HNSCC clinical specimens showed that S100A4 expression was positively correlated with clinical grading, stemness markers, and poorer patient survival. Together, our findings reveal a crucial role for S100A4 signaling pathways in maintaining the stemness properties and tumorigenicity of HN-CICs. Furthermore, our findings suggest that targeting S100A4 signaling may offer a new targeted strategy for HNSCC treatment by eliminating HN-CICs.

miR-181 as a putative biomarker for lymph-node metastasis of oral squamous cell carcinoma.

BACKGROUND Oral squamous cell carcinoma (OSCC) is an important malignant disease around the world. Aberrant expression of MicroRNAs (miRNAs) has been implicated in carcinogenesis of various cancers. In previous studies, up-regulation of miR-181 was observed when OSCC progressed from leukoplakia, dysplasia to invasive carcinoma. However, the function of miR-181 in oral tumorigenesis remains unclear. MATERIALS AND METHODS The expression levels of miR-181 in the tissue and plasma of OSCC patients were measured by quantitative RT-PCR. The correlation between miR-181 level and multiple clinical variables were then checked by Mann-Whitney test and Wilcoxon matched pairs test. To study the functional meaning of up-regulated miR-181, migration assay and invasion assay by transwells and colony forming assay were applied to analyze the tumorigenic phenotypes of OSCC cells with ectopical expression of miR-181. RESULTS Among different clinical variables, over-expression of miR-181 was correlated with lymph-node metastasis, vascular invasion, and a poor survival. Functional assays revealed ectopically over-expressed miR-181 would enhance cell migration and invasion, but not the ability of anchorage-independent growth of OSCC cells. In addition, the up-regulation of miR-181 could be detected both in tumor tissues and plasma. CONCLUSION miR-181 may enhance lymph-node metastasis through regulating migration, which could potentially be exploited as a putative biomarker for patients with OSCC.

Array-comparative genomic hybridization to detect genomewide changes in microdissected primary and metastatic oral squamous cell carcinomas

Oral squamous cell carcinoma (OSCC) is a common worldwide malignancy. However, it is unclear what, if any, genomic alterations occur as the disease progresses to invasive and metastatic OSCC. This study used genomewide array‐CGH in microdissected specimens to map genetic alterations found in primary OSCC and neck lymph node metastases. We used array‐based comparative genomic hybridization (array‐CGH) to screen genomewide alterations in eight pairs of microdissected tissue samples from primary and metastatic OSCC. In addition, 25 primary and metastatic OSCC tissue pairs were examined with immunohistochemistry for protein expression of the most frequently altered genes. The highest frequencies of gains were detected in LMYC, REL, TERC, PIK3CA, MYB, MDR1, HRAS, GARP, CCND2, FES, HER2, SIS, and SRY. The highest frequencies of losses were detected in p44S10, TIF1, LPL, MTAP, BMI1, EGR2, and MAP2K5. Genomic alterations in TGFβ2, cellular retinoid‐binding protein 1 gene (CRBP1), PIK3CA, HTR1B, HRAS, ERBB3, and STK6 differed significantly between primary OSCC and their metastatic counterparts. Genomic alterations in PRKCZ, ABL1, and FGF4 were significantly different in patients who died compared with those who survived. Immunohistochemistry confirmed high PIK3CA immunoreactivity in primary and metastatic OSCC. Higher FGF4 immunoreactivity in primary OSCC is associated with a worse prognosis. Loss of CRBP1 immunoreactivity is evident in primary and metastatic OSCC. Our study suggests that precise genomic profiling can be useful in determining gene number changes in OSCC. As our understanding of these changes grow, this profiling may become a practical tool for clinical evaluation.

Genetic and epigenetic alterations of the blood group ABO gene in oral squamous cell carcinoma

Loss of histo‐blood group A and B antigen expression is a frequent event in oral carcinomas and is associated with decreased activity of glycosyltransferases encoded by the ABO gene. We examined 30 oral squamous cell carcinomas for expression of A and B antigens and glycosyltransferases. We also examined DNA from these tumors for loss of heterozygosity (LOH) at markers surrounding the ABO locus at chromosome 9q34, for loss of specific ABO alleles, and for hypermethylation of the ABO promoters. Loss of A or B antigen expression was found in 21 of 25 tumors (84%) and was a consistent feature of tumors lacking expression of A/B glycosyltransferases. LOH at 9q34 was found in 7 of 27 cases (26%), and one case showed microsatellite instability. Among 20 AO/BO cases, 3 showed loss of the A/B allele and 3 showed loss of the O allele. Analysis of the proximal ABO promoter by methylation‐specific PCR and melting curve analysis showed hypermethylation in 10 of 30 tumors (33.3%), which was associated with loss of A/B antigen expression. ABO promoter hypermethylation was also found in hyperplastic or dysplastic tissues adjacent to the tumors, suggesting that it is an early event in tumorigenesis. Collectively, we have identified molecular events that may account for loss of A/B antigen expression in 67% of oral squamous cell carcinomas.

miR-134 induces oncogenicity and metastasis in head and neck carcinoma through targeting WWOX gene.

Head and neck squamous cell carcinoma (HNSCC) is a prevalent disease worldwide, and the survival of HNSCC has not improved significantly over the last few decades. MicroRNAs (miRNAs) have an important regulatory role during carcinogenesis. Our study investigated the pathogenic implications of miR‐134 in head and neck carcinogenesis. The clinicopathologic implications of miR‐134 in HNSCC were investigated using expression assays and the functional role of miR‐134 in HNSCC pathogenesis was determined using ectopic expression, knockdown and reporter assay experiments. Xenographic tumorigenesis and orthotopic nodal metastasis were assayed in mouse models. In situ hybridization and immunohistochemistry were used to detect the expression of miR‐134 and the WWOX gene in human HNSCC. The results indicated that miR‐134 was upregulated in HNSCC tissues relative to control mucosa. High expression of miR‐134 was associated with nodal metastasis and mortality of patients. Decreased plasma miR‐134 levels after tumor ablation indicated a better prognosis for patients. Multivariate analysis showed that high miR‐134 expression in HNSCC was an independent predictor of poor survival. Ectopic miR‐134 expression significantly enhanced in vitro oncogenic phenotypes and the orthotopic growth and metastasis of HNSCC cells. miR‐134 targeted WW domain‐containing oxidoreductase (WWOX) gene and cell invasion enhanced by miR‐134 expression was abrogated by ectopic WWOX expression in HNSCC cells. miR‐134 expression was reversely associated with the WWOX expression in HNSCC tissues. Evidences from our study substantiated that miR‐134 expression contributes to head and neck carcinogenesis by targeting the WWOX.

Association of Expression Aberrances and Genetic Polymorphisms of Lysyl Oxidase with Areca-Associated Oral Tumorigenesis

Purpose: Areca nut use is the major cause of oral squamous cell carcinoma (OSCC) in Southern Asians. Areca nut contains a high level of free copper ions. Lysyl oxidase (LOX) is a copper-activated enzyme critical for extracellular matrix organization. Contradictory evidence has been put forward to suggest that LOX may be either an oncogenic or a suppressive element. This study investigated the oncogenic significance of LOX in areca-associated OSCC. Experimental Design: The expression assays and polymorphism analysis were done to know the clinicopathologic implications of LOX status in OSCC. Knockdown and overexpression experiments were conducted to know the phenotypic effects of LOX on OSCC cells. Results: Up-regulation of LOX mRNA and LOX protein expression in OSCCs relative to adjacent oral mucosa was found. Precancerous lesions had the highest LOX mRNA expression. Areca nut extract up-regulated LOX expression in oral epithelial cells. Knockdown of LOX induced cellular migration and invasion, but it reduced the anchorage-independent growth and xenographic tumorigenesis of OSCC cells. The reduction of migration and invasion by LOX overexpression was partially rescued by blockage of LOX activity. The Arg158Gln polymorphism was associated with earlier clinical stage of OSCC. Wild-type LOX overexpression induced anchorage-independent growth in OSCC cells, but this was not for LOXArg158Gln overexpression. Conclusion: LOX exerts oncogenic roles in areca-associated OSCC. This potential could be affected by the existence of LOX propeptide domain or genetic polymorphism.