Alterations in cell cycle and apoptosis in drug resistant cells

摘要: The effects the anthracycline Doxorubicin exerts on variants of human lung carcinoma cell line DLKP was investigated in this thesis, an attempt to understand means by which chemotherapeutic agent its cytotoxic and cytostatic tumours. Sensitive DLKP-SQ resistant DLKP-SQ/A250 10p#7, DLKP-A2B DLKPA5F were exposed equitoxic doses Doxorubicin, resulted approximately 50% kill after 72 hours. subsequent cycle apoptosis induction studied identify any differences between sensitive cells, that may contribute state. Doxorubicin treatment induced a permanent G2/M arrest cells 24 hours, temporary at earlier time 12-16 hours with bypass re-emerge accumulate G l. transient progression into l indicated insufficient checkpoint monitoring DNA damage doxorubicin variants. controller complex cyclin B-cdkl , explain over-ride seen drug cells. did not alter B or cdkl protein levels, complex-forming ability cdkl. be due increase inhibitory phosphorylation In contrast Tyrl5 change kinase activity seems following treatment, unlike displayed little alterations upon treatment. Further investigation mechanism override involved examination regulators weel cdc25 phosphatase. Initial studies these raised some mechanistic possibilities override. Apoptosis occurs each four lines kinetics death dependent concentration exposure tune used. investigated. Analysis procaspase expression revealed caspase-3 is greatly downregulated lines, caspase-8 reduced lesser extent. Levels procaspases decrease during apoptosis, indicating lack caspase activation general, very low doxorubicininduced raising doubts about involvement apoptotic pathway. substrate PARP cleaved although cytoskeletal fodrin all lines. Furthermore inhibitors zYAD-ftnk, YVAD-fmk DEVD-fmk readily cross membranes, failed protect from doxorubicin-induced possibility redundancy caspase-independent Involvement Fasmediated pathway also investigated, do express altered levels CD95 receptor compared When treated Fas signalling pathway, combination inhibitors, they continued die apoptosis. fact permeable both caspases prevent lends further weight possible existence