MMP13 and ISG15 are potential driver genes in oral squamous cell carcinoma / Vincent Chong Vui King

Oral squamous cell carcinoma (OSCC) is an exceptionally aggressive disease with poor prognosis. A major drawback in diagnosis and treatment of OSCC is the lack of knowledge relating to how genetic instability in oral cancer genomes affects oral tumorigenesis. This current study aimed to determine the copy number alterations (CNAs) in OSCC using array comparative genomic hybridization (array CGH) and to determine the expression of candidate genes. Putative candidate gene was identified and further elucidated to explore its potential role(s) in oral tumorigenesis. Materials and Methods: Genome-wide profiling was performed on 75 OSCCs using array CGH. The copy number alterations (CNAs) associated genes that mapped to the amplified and deleted regions were subjected to pathway and network functional analysis using the Ingenuity Pathway Analysis software. The selected putative amplified genes involved in oncogenic networks were further subjected to gene expression analysis using qPCR. The protein expression of the selected putative amplified genes was determined using immunohistochemistry (IHC) technique in the non-cancer oral mucosa, oral epithelial dysplasia (OED) and OSCC samples. Knockdown of the putative amplified gene was performed using small interfering RNA (siRNA) technology in OSCC cell lines and the roles of the gene in cell proliferation, apoptosis, migration and invasion were evaluated. In this study, the frequent CNAs were observed on multiple genomic regions, including amplifications on chromosome 1p, 3q, 5p, 7p, 8q, 9q, 10p, 11q, and deletions on 3p and 8p. Apart from that, this study also demonstrated the significant association between amplification of chromosome 8q, 11q, 7p and 9p and deletion of 8p with clinico-pathological parameters such as tumour size, lymph node metastasis (LNM) and tumour staging. This study also identified novel candidate genes namely matrix metallopeptidase 13 (MMP13) and interferon stimulated gene 15 (ISG15) that linked between cell death and survival, cellular movement and cellular development oncogenic network. Furthermore, this study also demonstrated over-expression of MMP13 (chromosome 11q22.2) and ISG15 (chromosome 1p36.33) as prognostic markers in OSCC. Silencing of ISG15 in OSCC cell lines decreased the tumour cell proliferation, migration, invasion, induced apoptosis and increased the cisplatin sensitivity in oral tumourigenesis. Conclusion: This current study has identified multiple CNAs including amplifications on chromosome 1p, 3q, 5p, 7p, 8q, 9q, 10p, 11q and deletions on 3p and 8p. This study also showed that amplification of the chromosome 7p, 8q, 9p, 11q and genetic signature (+7p8q9p11q) as well as deletion of chromosome 8p was associated with clinico-pathological parameters and poor survival. Apart from that, through the network analysis, the putative amplified genes namely ISG15 and MMP13 were found to be associated with the top oncogenic network namely cell death and survival, cellular movement, cellular development network signalling. This study also has demonstrated the over-expression of MMP13 and ISG15 were associated with lymph node metastasis, tumour staging and poor prognosis. Through the siRNA knockdown of the ISG15 expression inhibited the tumour cell proliferation, migration, invasion and induced cell death in oral tumorigenesis.