Date of Award

2010

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Environmental Science

First Advisor

Goktepe, Ipek

Abstract

Phytolacca americana is an herbaceous plant native to North and South America and East Asia. Pokeweed antiviral protein (PAP) has been extracted from this plant and antiviral activity toward Chenopodium quinoa and other viruses has been cited. Conjugated to various monoclonal antibodies, PAP has been shown to inhibit HIV-1 replication and to arrest the proliferation of B-lineage Acute Lymphoblastic Leukemia blasts. Since studies involving the activities of P. americana extracts on various cancer cell lines are limited, the major objectives of this study were to: 1) evaluate the antiproliferative activity of three extracts from P. americana against human breast (MCF7) and colon cancer (HCT-116) cells in vitro and 2) investigate the changes at the protein and gene levels after exposing the HCT-116 cells to P. americana extracts in vitro. Antiproliferative activities of crude ethanol (PRE), methanol, and water extracts of P. americana against HCT-116 and MCF-7 cells were determined using the MTT assay. PRE was fractionated and the fractions were tested for their antiproliferative activities. For comparison, the antiproliferative activity of PAP was also tested. Changes in levels of caspase 2, 3, 6, 8, and 9 activities were determined in HCT-116 cells exposed to PRE and its most active fraction (PREW). The Human Cancer Pathway Finder Realtime PCR Profiler was used to determine changes in activities of 84 genes in HCT116 cells exposed to PRE and PREW. PRE had a greater antiproliferative effect (P≤0.05) on HCT-116 cells than the methanol and water extracts. None of the extracts showed a significant antiproliferative activity against MCF-7 cells (P≥0.05). The water fraction of PRE (PREW) showed the greatest antiproliferative activity compared to the ethyl acetate and butanol fractions (P≤0.05). The effect of PAP on the proliferation of HCT-116 cells fluctuated depending on the concentration. Caspases 6 and 9 showed increases in activity (P≤0.05) in HCT-116 cells exposed to PRE. Caspases 3, 8, and 9 had increases in activity in HCT-116 cells exposed to PREW. For the Cancer Pathway Finder, PRE at 3200 µg/ml had the most desirable gene changes in the treatment of colon cancer.

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