Oral squamous cell carcinoma (OSCC) is the sixth most common cancer worldwide. It is a result of numerous aetiological factors such as genetic predisposition, smoking, excessive alcohol consumption and viruses such as the human papilloma virus. Due to late diagnosis it has a high mortality and morbidity rates which has remained unchanged over the last 5 decades. Currently no screening is available for high risk patients for better monitoring. Diagnosing OSCC relies on histopathology of biopsy tissue, reviewed for dysplasia and advancing lesions. Although the technique has been used for decades for successful diagnosis it fails to identify the molecular signature of OSCC which appears much before the visual signs. It also falls short in predicting the malignant transformation of pre-malignant oral lesions. Identifying the molecular and genetic changes leading to OSCC lesion will aid in more specific (quantitative) and early diagnosis of the disease reducing the financial burden of treating late-stage OSCC patients on the healthcare system. This study focuses on developing new adjuncts which can be used alongside histopathology for early diagnosis. There is a need to monitor high risk patients through non-invasive methods causing less patient discomfort. We therefore explored the potentials of exosomes which are extracellular vesicles secreted by normal and tumour cells. They can be isolated from body fluids such as blood and saliva. In cancer biology exosomes offer both diagnostic and therapeutic advantage. Their involvement in cell-cell communication indicates their influence in tumour development, progression, metastasis and therapeutic efficacy. Exosomes released by cancerous cells carry numerous biomarkers, which are passed on to healthy cells via microenvironment, causing stromal and angiogenic activation along with immune escape. In this study exosomes were successfully isolated from body fluids (blood, saliva and plasma) and cell line supernatant through ultracentrifugation and characterised by visual and particle size quantification techniques including Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM), Zetasizer and Nanosight Tracking Analysis (NTA). Exosomal specific membrane proteins were identified through Western blotting. 5 We report the presence of a potential protein biomarker located exclusively on the outer membrane of cancer exosomes. Since body fluids consist of a heterogeneous population of exosomes derived from multiple cell types, such surface biomarker can potentially be used to isolate OSCC exosomes. Characterisation of exosomal mRNA cargo was done using Agilent Bioanalyzer (for RNA quantity and quality assurance) and reverse transcription-quantitative PCR (RT-qPCR; for gene specific quantitation). Functional significance of exosomes was studied by transfecting normal oral keratinocyte cells with self and cancer-derived exosomes. Through gene-expression microarray and subsequent RT-qPCR verification, we report a panel of differentially expressed genes involved in essential cellular functions being modulated by exosome transfection. A previously developed molecular diagnostic system by our research group called quantitative malignancy index diagnostic system (qMIDS) based on FOXM1 oncogene and its downstream targets was validated on archival formalin fixed paraffin embedded OSCC patient biopsy samples. We report that qMIDS index successfully correlates with the disease stages including dysplasia, tumour and lymph node metastasis. Furthermore, through meta-analysis of 8 OSCC microarray studies we identified a panel of six genes including PLAU, FN1, CDCA5, CRNN, CLEC3B and DUOX1 (q6) which are able to identify two clinically distinct sub-groups of OSCC patient population. Through RT-qPCR the expression of q6 biomarkers was established in 100 OSCC biopsy samples. This information can be of immense importance in developing personalized treatment strategies based on the molecular makeup of the presenting tumour.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:766170 |
| Date | January 2018 |
| Creators | Qadir, Fatima |
| Publisher | Queen Mary, University of London |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://qmro.qmul.ac.uk/xmlui/handle/123456789/39763 |
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