Identification of novel genes associated with endocrine resistance in breast cancer

The overall aims of this project were to identify rnRNAs overexpressed or underexpressed as MCF7 human breast cancer cells progress to growth pathways independent of oestrogen and resistant to the antioestrogen, fulvestrant. Growth of oestrogen maintained and long-term oestrogen deprived MCF7,cells with or without la-8M l7p-oestradiol for 7 days enabled the comparison of expression profiles to identify a number of oestrogen regulated genes, in addition to a number of genes differentially expressed in long-term oestrogen deprived cells compared to cells which had been deprived of oestrogen for just? days. Comparison of expression profiles for oestrogen maintained and oestrogen deprived cells following long-term exposure to fulvestrant revealed large alterations in a number of gene expression levels, particularly in the oestrogen maintained cells. Adrenomedullin may have a role in tumour survival and angiogenesis and consistent upregulation of adrenomedulin mRNA was observed during progression to oestrogen insensitivity in duplicate microarray experiments. Real-time RTPCR was able to confirm the increase in mRNA levels in long-term oestrogen deprived cells. Immunofluorescent staining using a monoclonal antibody specific for adrenomedullin showed an increase in the amount of protein in long-term oestrogen deprived cells. Following short and long-term treatment with tamoxifen and fulvestrant the abundance of adrenomedullin rnRNA was increased in oestrogen maintained cells but not in the long-term oestrogen deprived cells. Real time RT-PCR analysis of the GAiA family of transcription factors revealed a reciprocal relationship between GATA3 and GATA6 in ER positive cells and ER negative cells where GATA6 showed highest expression in the ER negative cells and GATA3 was highly expressed in the ER positive cells. Changes were observed in levels of all six of the GATA factors following long-term oestrogen deprivation indicating a functional role for these transcription factors in progression to endocrine resistance. Many potential targets have been identified by the use of microarrays but further validation of cell lines and tumour samples is required to examine the importance of these as possible markers of endocrine resistance in breast tumours.EThOS - Electronic Theses Online ServiceGBUnited Kingdo