Date of Award

2010

Document Type

Honors Thesis (Colby Access Only)

Department

Colby College. Chemistry Dept.

Advisor(s)

Julie T. Millard

Second Advisor

Kevin P. Rice

Abstract

Diepoxybutane (DEB) and epichlorohydrin (ECH) are bifunctional alkylating agents that form covalent DNA interstrand cross-links at the N7 positions of deoxyguanosine residues on opposing stands of DNA. The cross-linking activity of many of these agents has been found to correlate positively with their cytotoxicity. Previous research in the Millard Laboratory has compared the cytotoxicity of DEB and ECH between chicken 6C2 erythro-progenitor cells randomly distributed throughout the cell cycle and cells enriched in G2/M phase. The objective of this research project was to expand upon previous studies and determine whether the cytotoxicities of DEB and ECH vary according to the major biological events characterized by cells enriched in G0/G1, S, and G2/M stages. Consistent with previous research, results indicated that both DEB and ECH were more cytotoxic in G2/M phase compared to an unsynchronized control. In contrast to previous research however, DEB was found to be about twice as cytotoxic as ECH in the incubation periods examined. In addition, both cross-linking agents were found to be less potent in 6C2 cells enriched in G0/G1; again, with DEB exhibiting greater cytotoxicity than ECH. Determining whether a compound stimulates apoptosis in particular cell line is essential in fully understanding its potentially carcinogenic effects or possible use as an anti-cancer agent. It has previously been established by the Millard Research Group that in terms of apoptotic potential, DEB >> ECH. To complement the cytotoxicity data acquired in this study, the mechanism of cell death was determined at the lethal dose (LD50) of both cross-linking agents in unsynchronized, G0/G1 enriched, and G2/M enriched 6C2 cells. In general, for both cross-linking agents, apoptotic potential exhibited the following trend: unsynchronized > G2/M enriched > G0/G1 enriched. However, necrosis was found to be the primary form of cell death in all treatment samples. In slight contrast to previous research using unsynchronized cells, little difference in the apoptotic potential of DEB and ECH was observed in either unsynchronized or cell-stage-enriched cultures.

Comments

Full-text download restricted to Colby College campus only.

Keywords

cell cycle, bifunctional alkylating agents, 6C2 erythro-progenitor cells, apoptosis, diepoxybutane, epichlorohydrin

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