Soo-Hwang Teo

Gene expression in human oral squamous cell carcinoma is influenced by risk factor exposure.

Oral squamous cell carcinoma (OSCC) is a world health problem and is associated with exposure to different risk factors. In the west, smoking and alcohol consumption are considered to be the main risk factors whilst in India and southeast Asia, betel quid (BQ) chewing is predominant. In this study, we compared the gene expression patterns of oral cancers associated with BQ chewing to those caused by smoking using Affymetrix microarrays. We found that 281 genes were differentially expressed between OSCC and normal oral mucosa regardless of aetiological factors including MMP1, PLAU, MAGE-D4, GNA12, IFITM3 and NMU. Further, we identified 168 genes that were differentially expressed between the BQ and smoking groups including CXCL-9, TMPRSS2, CA12 and RNF24. The expression of these genes was validated using qPCR using independent tissue samples. The results demonstrate that whilst common genes/pathways contribute to the development of oral cancer, there are also other gene expression changes that are specific to certain risk factors. The findings suggest that different carcinogens activate or inhibit specific pathways during cancer development and progression. These unique gene expression profiles should be taken into consideration when developing biomarkers for future use in prognostic or therapeutic applications.

Transcriptional profiling of oral squamous cell carcinoma using formalin-fixed paraffin-embedded samples.

Despite the advances in cancer treatment, the 5-year survival rate for oral cancer has not changed significantly for the past 40 years and still remains among the worst of all anatomic sites. Gene expression microarrays have been used successfully in the identification of genetic alterations in cancer development, however, these have hitherto been limited by the need for specimens with good quality intact RNA. Here, we demonstrated the use of formalin-fixed paraffin-embedded tissues in microarray experiments to identify genes differentially expressed between cancerous and normal oral tissues. Forty-three tissue samples were macrodissected and gene expression analyses were conducted using the Illumina DASL assay. We report RNA yield of 2.4 and 0.8 microg/mm(3) from tumour and normal tissues, respectively and this correlated directly with the tissue volume used for RNA extraction. Using unsupervised hierarchical clustering, distinct gene expression profiles for tumour and normal samples could be generated, and differentially expressed genes could be identified. The majority of these genes were involved in regulation of apoptosis and cell cycle, metastasis and cell adhesion including BCL2A1, BIRC5, MMP1, MMP9 and ITGB4. Representative genes were further validated in independent samples suggesting that these genes may be directly associated with oral cancer development. The ability to conduct microarrays on formalin-fixed paraffin-embedded specimens represents a significant advancement that could open up avenues for finding genes that could be used as prognostication and predictive tools for cancer.

MDM2 SNP309 does not confer an increased risk to oral squamous cell carcinoma but may modulate the age of disease onset

The MDM2 SNP309 has been associated with increased expression of the protein which could suppress p53 function, and has been shown to modulate risk to cancer. We have previously shown that overexpression of MDM2 is a common event in oral cancers. In the present study, we determined the association between the MDM2 SNP309 polymorphism and oral cancer in 207 oral cancer patients and 116 normal subjects. We genotyped the MDM2 SNP309 by PCR-RFLP. Logistic regression was adapted to calculate odds ratios for MDM2 SNP309 polymorphism from univariate and multivariable adjusted models. Our results suggest that MDM2 SNP309 does not confer increased risk to oral cancer (OR=1.55, 95% CI=0.77-3.11). However, the GG/TG genotype was associated with later disease onset in women above 55 years of age. Collectively, our data suggests that MDM2 SNP309 may modulate the risk to oral cancer and is a modifier of the age at oral cancer onset in women above the age of 55 years.

Determination of the global gene expression profile of oral cancers using paraffin-embedded tissues

Introduction: Oral cancer is a common disease in Asia. However, our ability to deliver effective and targeted therapy remains limited by our lack of understanding of the molecular pathogenesis of oral carcinogenesis. One method to understand the nature of genes and gene products whose aberrant expression promote malignant transformation is by using microarrays. However, such studies have been limited by the availability of specimens with intact RNA and adequate clinical data to enable the identi?cation and validation biomarkers either as predictive or therapeutic tools. Objective: We have determined the global gene expression pro?les of oral squamous cell carcinoma (OSCC) of the buccal mucosa using formalin ?xed paraf?n-embedded specimens. Materials and Methods: Gene expression analyses using the DASL Assay were performed on 34 paraf?n embedded tissues, of which 22 samples were OSCC of the buccal mucosa and 12 samples were normal surface epithelium of reactive lesions such as the ?broepithelial polyp from matched site. We used the Illumina Beadstudio Software to compare the expression pro?les of normal and OSCC samples. We selected genes which were differentially expressed by at least two-fold (with the detection p-value <0.01) for further analysis. Results: A total of 47 genes were differentially expressed by at least two-fold between normal and OSCC. Deregulated genes included genes which were involved in cell signaling, adhesion and invasion, such as ITGB4, MMP1, MMP10, MMP7, CXCL9, and ALOX12. We have validated the over-expression of MMP1, ITGB4 and MMP10, and down-regulation of ALOX12 by quantitative real-time PCR. Conclusion: We have successfully conducted global gene expression studies using paraf?n-embedded buccal mucosa specimens. This approach has enabled the identi?cation of genes whose expression can help explain the aggressive nature of oral cancers arising from the buccal mucosa.