Apoptosis induced by cancer chemotherapeutic drugs and its genetic suppression

Apoptosis can be distinguished from necrosis, the classical form of cell death, by several morphological and biochemical criteria. Apoptotic cells, but not necrotic cells, show early condensation of chromatin as well as endonuclease activation resulting in cleavage of the nuclear DNA into oligonucleosomal fragments. Both physiological and low level cytotoxic stimuli have been shown to induce apoptosis, which in some cell models can be suppressed by inhibitors of protein and RNA synthesis. The concept of the cell being actively involved in its own death, combined with the demonstration that factors which alter the rate of cell death, such as the proto-oncogene bcl-2, can directly affect the number of cells within a population, has resulted in the identification of cell death alongside proliferation and differentiation as a means for controlling celi population growth. The purpose of this study was to determine if bcl-2 and the Epstein-Barr virus gene BHRF1, which share 25% primary amino acid sequence homology, could suppress apoptosis in response to a variety of anti-cancer treatments. After demonstrating apoptotic cell death on treatment with chemotherapeutic agents in an IL-3 dependent cell line (FDCP-1) and three different EBV genome-positive Burkitt's lymphoma cell lines, the survival of EBV-BL cell lines expressing either exogenous bcl-2 or BHRF1 was examined. Suppression of apoptosis in response to treatment with chemotherapeutic drugs or y radiation was clearly shown in EBVBL cells expressing bcl-2 or BHRF1 when compared to control transfectants. This study has further confirmed that BHRF1 is functionally homologous to bcl-2, suggesting that BHRF1 may act to prevent apoptosis during EBV infection. Suppression of chemotherapeutic drug induced cell death by either bcl-2 or BHRF1 also represents a novel form of drug resistance and may form an alternative mechanism by which multidrug resistance may arise during chemotherapy. The identification and investigation of other genes which produce suppression of apoptosis is also important in order to determine the extent of involvement of apoptotic suppression in the transformation to the malignant state and in the acquisition of multidrug resistance. A protocol to screen for 'apoptosis-suppressed cells' in the FDCP-1 E -3 dependent cell line was developed to identify new genes involved in the pathway(s) of apoptosis.

Name dc:type.qualificationname

d_ph

Level dc:type.qualificationlevel

d_ph

Grantor dc:publisher.institution

University of Birmingham

Year dc:date.issued

1994

Author dc:creator

• McCarthy, Nicola Jane

• QP Physiology

Repository record dc:identifier.uri

http://etheses.bham.ac.uk//id/eprint/34/2/Decl_IS_McCarthy94PhD.gif

OAI identifier oai:identifier

oai:etheses.bham.ac.uk:34