Molecular mechanisms of drug resistance and invasion in a human lung carcinoma cell line
Joyce, Helena (2014) Molecular mechanisms of drug resistance and invasion in a human lung carcinoma cell line. PhD thesis, Dublin City University.
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Metastasis and drug resistance present as major problems to patients during cancer chemotherapy. The research outlined in this thesis aims to further our knowledge about the molecular mechanisms involved in these processes and the relationship between drug resistance and cancer invasion and/or metastasis.
One explanation for the link between resistance and metastasis is that resistance facilitates tumour progression and invasion into both surrounding and distal tissues. Investigations were conducted on a clonal sub-population of poorly differentiated human lung squamous carcinoma cells (DLKP). These were pulsed with mitoxantrone and the resulting cell populations extensively characterised. Two sub-lines emerged: SQ-Mitox-BCRP and SQ-Mitox-MDR cell lines. These two cell lines typically exhibited resistance to the selecting agent (ranging approx. 210 to 320-fold). This occurred as an early event during the pulsing process. The two sublines differed in their morphology and pattern of gene expression. In addition, BCRP was significantly increased in one population (SQ-Mitox-BCRP) while P-gp was significantly increased in the other population (SQ-Mitox-MDR).
A crucial step in human lung cancer progression appears to be the acquisition of invasiveness. The population of cells arising from the 4th drug pulse remained noninvasive but had acquired a high level of drug resistance. However, after two additional drug pulses, all cell lines acquired invasiveness. The invasive, drug resistant BCRP and MDR cell line variants were characterised in depth and microarray analysis was used to find functionally significant changes in the transition from the preinvasive to the invasive phenotype. Functional and cellular signaling analyses were performed on the cell lines using pharmacological inhibitors, function-blocking antibodies, and gene silencing by RNA interference.
The DLKP cell line appears to contain at least three morphologically distinct sub-populations of cells with different levels of invasiveness. Microarray analysis generated gene lists that were specific to an invasive phenotype, identifying possible genetic markers for invasion. Proteins (including the cell adhesion molecules, N-cadherin and ALCAM and the axon guidance molecule SLIT2) were also identified as possible and alternative markers capable of distinguishing between the different cell line clones.
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