- Title
- Investigating the mechanisms of tobacco cigarette smoke induced lung cancer
- Creator
- Harrison, Celeste Louise
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2017
- Description
- Research Doctorate - Doctor of Philosophy (PhD)
- Description
- Background: Lung cancer is the most common type of cancer, and leading cause of cancer related deaths worldwide, but its development is currently poorly understood. A combination of environmental factors, such as cigarette smoking, and genetic susceptibility is thought to result in uncontrolled cellular growth and tumourigenesis. Current treatments are poorly effective. Clinically relevant animal models are urgently needed to increase our understanding of lung cancer pathogenesis, as well as to test novel therapeutic compounds. Hypothesis and Aims: We hypothesised that our published technique for cigarette smoke (CS) exposure, which induces the development of chronic obstructive pulmonary disease (COPD) in a short time frame (8 weeks) would provide a good platform to develop new mouse models of lung cancer. Thus, the aim of this project was to develop a clinically relevant mouse model of lung cancer that is induced by a nicotine derived carcinogen, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) challenge and/or CS exposure in a genetically susceptible yet wild type mouse strain that recapitulates typical drivers of tumorigenesis. Methods: A/J mice were challenged with low and high doses of NNK (50-100mg/kg, up to three times) via intraperitoneal (i.p.) injection, and chronically exposed to CS for up to 20 weeks. Air rest (non-CS exposure) periods were included after smoking cessation for up to 16 weeks duration. The development of lung tumours was assessed by histological analysis of haematoxylin and eosin (H&E) stained lung section. COPD disease features were determined by assessment of inflammation in bronchoalveolar lavage, emphysema by mean linear intercept technique, and lung function analysis. Factors associated with inflammation, cancer, and epithelial-mesenchymal transition (EMT) were examined by qPCR for messenger RNA (mRNA) and microRNA (miRNA) expression profiling; and immunohistochemistry, immunoblot, and enzyme linked immunosorbent assay (ELISA) for protein analysis. Results: Low dose NNK challenge (50-70mg/kg, single i.p. injection) induced bronchoalveolar adenomas in 33.33% of A/J mice after 14 weeks, which increased to 66.66% after 22 weeks, and 85.71% after 36 weeks. Tumour incidence or multiplicity was not increased by CS exposure for 8, 12, or 20 weeks, with air rest periods of 6, 10 and 16 weeks respectively. High dose NNK challenge (100mg/kg, 3 i.p. injections) also induced bronchoalveolar adenomas in 83.3% of A/J mice after just 8 weeks, where CS exposure of the same period without inclusion of an air rest period significantly suppressed tumour development. With the inclusion of an 8 week air rest period after 8 weeks of CS exposure, tumour incidence was 100% in both groups challenged with high dose NNK, and CS exposure increased tumour multiplicity, although not statistically. Increasing the air rest period after smoking cessation and lowering the dose of NNK challenge did not alter this outcome. Importantly, 8 weeks of CS exposure induced COPD disease features including altered lung function, increased emphysema-like alveolar enlargement, and increased inflammation in BALF. Furthermore, gene expression profiling of whole lung tissue revealed increases in key inflammatory markers, such as serum amyloid 3 (Saa3) in response to CS exposure at all time-points examined. Important cancer- and EMT-associated factors, including the Kirsten rat sarcoma viral oncogene homolog gene (Kras), mmu-miR-135b, and transforming growth factor beta 1 (TGFβ) signalling factors were also shown to be selectively altered in response to CS exposure and NNK challenges. Conclusions: Although CS exposure of any time-frame did not statistically increase tumour incidence or multiplicity, we were able to profile molecular changes in response to CS exposure or NNK challenge in the current models which demonstrated varying levels of tumour development. However, further optimisation of the current models is required to establish a clinically appropriate model in which CS exposure significantly increases lung tumour development, and in which progression from adenoma to adenocarcinoma is demonstrated. We anticipate that refining these model(s) will allow for further investigations into lung cancer pathology, and may be used to identify novel targets and therapies, to eventually improve patient outcome.
- Subject
- lung cancer; cigarette smoke; tobacco; adenocarcinoma
- Identifier
- http://hdl.handle.net/1959.13/1343065
- Identifier
- uon:29089
- Rights
- Copyright 2017 Celeste Louise Harrison
- Language
- eng
- Full Text
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| View Details Download | ATTACHMENT01 | Thesis | 22 MB | Adobe Acrobat PDF | View Details Download | ||
| View Details Download | ATTACHMENT02 | Abstract | 719 KB | Adobe Acrobat PDF | View Details Download |