This study completed the analysis of mutational frequencies and clinicopathological patterns of six EGFR pathway-related genes (EGFR, HER2, HER4, KRAS, BRAF and MET) in 212 resected lung adenocarcinomas (AD) from 98 male and 114 female Chinese patients without prior chemotherapy or tyrosine kinase inhibitor (TKI) therapy. Genomic DNA and cDNA sequencing, quantitative PCR and fluorescence in-situ hybridization (FISH) were employed to investigate mutation and amplification status of the relevant genes. Overall, more than 75% of tumours were detected to harbour mutations or amplification in one of these six genes. The commonest mutation was found to involve EGFR, comprising 60.38% of cases, followed by KRAS (9.43%), HER2 (2.36%), MET (2.36%), BRAF (1.42%) and HER4 (0.47%). Four somatic mutations in MET exon 14 splicing region were found, leading to alternative splicing and a transcript lacking exon 14. Two of the MET mutant tumours and one MET wild-type tumour showed MET amplification of more than 3.5 fold increase in copy number. Mutations of EGFR were significantly more frequent in female (p = 0.0196), non-smokers (p < 0.001) and well differentiated tumours (p = 0.0209). KRAS mutations showed significant association with male (p = 0.0099) and smoking history (p = 0.0011). A novel HER2 D769Y mutation was found and HER2 mutations were associated with smokers (p = 0.0013) and poorly differentiated tumours (p = 0.0147). BRAF, MET mutations and MET amplification were not associated with clinicopathological factors. Mutations were mutually exclusive except for two cases with KRAS and HER4/BRAF. MET amplification was co-existent with MET mutations in two cases. MET amplification was found to negatively correlate with disease-free and cancer-specific survivals. The results suggested that MET amplification may contribute to disease progression and could be a therapeutic target in primary lung AD in Hong Kong Chinese patients. / published_or_final_version / Pathology / Master / Master of Medical Sciences

published_or_final_version / Pathology / Master / Master of Philosophy

published_or_final_version / Medical Sciences / Master / Master of Medical Sciences

published_or_final_version / Medicine / Master / Master of Philosophy

abstract / Biochemistry / Doctoral / Doctor of Philosophy

published_or_final_version / Public Health / Master / Master of Public Health

The dynamics of cell signalling are critical to cell fate decisions. Human Epidermal growth factor Receptors (HERs)-mediated Ras/Raf/MEK/ERK and PI3K/Akt signalling cascades relay extracellular signals from the plasma membrane to targets in the nucleus and cytoplasm and play pivotal roles in cell fate determination including proliferation, differentiation and cell survival. Both pathways, once activated, are further regulated by complex feedback loops which may exert either positive or negative effects on cascade components and can result in signalling oscillation. In this study, heregulin (HRG) - and epidermal growth factor (EGF)- stimulated oscillation of both p-ERK1/2 and p-Akt expression in breast cancer cell lines was demonstrated. The oscillation was cell line dependent and was observed in MCF-7 and MCF-7/HER2-18 cells but not in BT474 cells. The oscillation was augmented by cycloheximide implicating transcriptional involvement. Gene expression analysis identified 29 genes as possible candidates involved in the transcriptional feedback regulation. Apart from the feedback regulation, feedforward regulation was also observed. To expedite the analyses In-cell Western and Reverse Phase Protein Array (RPPA) assays were developed. A scheme of transcriptional feedback loops regulating the oscillation in the ERK1/2 pathway is proposed, including negative feedback loops to ERK1/2 from DUSPs, early positive and late negative feedback loops to MEK1/2 and positive feedback loops to HER-3 from AREG, HB-EGF, CYR61 and CTGF. Two HER-2-targeted inhibitory monoclonal antibodies were investigated – trastuzumab and pertuzumab. Trastuzumab not only inhibited the growth of HER-2 over-expressing MCF-7/HER2- 18 cells and BT474 cells but also that of EGF-driven MCF-7 cells which expressed low/moderate HER-2 levels. Pertuzumab blocked the growth of both MCF-7 and MCF-7/HER2-18 driven by either EGF or HRG. When used in combination with trastuzumab, pertuzumab had much more potent activity in inhibiting cell growth and signalling than either single drug. Trastuzumab and pertuzumab had opposing effects on immediate p-ERK1/2 signalling and trastuzumab’s effects on signalling could be mimicked by the PI3K inhibitor LY294002. PTPN13, a non-receptor type tyrosine protein phosphatase, is a proposed tumour suppressor in breast cancer. This was investigated as a candidate regulator of the signalling oscillation and although not observed as a transcriptional modulator of the oscillation, its high expression level was observed to be associated with cell growth inhibition in MCF-7/HER2-18 cells by trastuzumab. Moreover, immunohistochemical analysis of 121 clinical tumours which had received trastuzumab treatment revealed the correlation between the expression level of PTPN13 and the mutation status of PIK3CA. In conclusion, the observed oscillation may contribute to the elucidation of the complex regulation of signalling pathways, which is vital to the different cell fate decision made through the same core pathway. The synergy between trastuzumab and pertuzumab supports the clinical use of the combination treatment and suggested PI3K/Akt pathway as the major pathway in controlling tumour growth.

published_or_final_version / abstract / Medicine / Master / Master of Philosophy

published_or_final_version / Pathology / Doctoral / Doctor of Philosophy

published_or_final_version / Pathology / Master / Master of Medical Sciences