Date of Graduation

5-2014

Document Type

Thesis

Degree Name

Master of Science in Food Science (MS)

Degree Level

Graduate

Department

Food Science

Advisor

Navam Hettiarachchy

Committee Member

Kristen Gibson

Second Committee Member

Jackson Lay

Third Committee Member

Mahendran Mahadevan

Keywords

Apoptosis, Bioactives, Biomarkers, Breast Cancer, Mechanism, Pentapeptide

Abstract

Bioactive peptides derived from food sources with anti-proliferative properties against cancer have drawn more attention in recent years. A pentapeptide derived from rice bran has shown anti-proliferative propertiesagainst human breast cancer cells. The objective of this study was to investigate the mechanistic action of the pentapeptide-induced apoptosis in breast cancer cell models (MCF-7 and MDA-MB-231). The growth inhibition activity of the pentapeptide was

evaluated by MTS[3-(4,5-dimethylthiazol-2-yl)-5-(3- arboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium, inner salt] assayand trypan blue assay in a dose- and time-dependent manner.

The apoptotic properties of pentapeptide-induced apoptosis on cancerous breast cells were evaluated by morphological changes, DNA fragmentation, and caspases-3/7, -8,and -9 activities.

The levels of molecular targets (p53, COX-2, TNF-α, Fas, Bax, Bcl-2, and ErbB-2) were evaluated by enzyme-linked immunosorbent assay (ELISA) kits. Pentapeptide showed growth inhibition activities on MCF-7 and MDA-MB-231 cells. Apoptotic features including

morphological changes,DNA fragmentation, and caspases activation were observed in both cells lines after pentapeptide treatment. Decreased levels of COX-2, Bcl-2, and ErbB-2 and increased levels of p53, TNF-α, Fas, and Bax expression were detected after cells exposed to pentapeptide from 72 to 96 hr. The results suggest that the pentapeptide inhibits growth of human breast cancer cells by introducing apoptosis through a caspase-dependent pathway. The pentapeptide amplifies the death signal by down-regulating the expression of ErbB-2 in both cell lines and

COX-2 in ER (Estrogen Receptor)-positive MCF-7 cells. This study provides insight on the molecular mechanism of action of the pentapeptide against breast cancer cells. After further animal and human clinic trial, the pentapeptide has the potentiality to be analternative strategy to current anti-cancer drugs.

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