Semester

Summer

Date of Graduation

2003

Document Type

Dissertation

Degree Type

PhD

College

Davis College of Agriculture, Natural Resources and Design

Department

Biochemistry

Abstract

Metallothioneins (MT) are a family of low molecular weight (6 kDa) cysteine rich proteins that participate in a variety of functions such as detoxification of heavy metals and homeostasis of essential metals. They can also act as scavengers of free radicals. MT-1 and 2 isoforms are ubiquitously expressed, whereas the expression of the third isoform is limited to the neural tissue. In the PC-3 prostate cancer cell line, MT-3 expression has been shown to inhibit cell growth and increase drug resistance. The goal of the present study was to determine if MT-3 overexpression would influence the growth of human breast cancer cell lines. To determine this, the coding sequence of the MT-3 gene was stably transfected into 2 estrogen receptor positive (MCF-7 and T-47D) and 2 estrogen receptor negative cell lines (Hs578T and MDA-MB-231) having no basal expression of MT-3. Cell growth was determined by counting DAPI-stained nuclei, cadmium resistance by the colony formation assay, MT mRNA expression by RT-PCR, and MT protein by immunoblot. It was demonstrated that MCF-7 and Hs578T cells that overexpress the MT-3 gene are growth inhibited compared to untransfected cells. In contrast, T-47D and MDA-MB-231 cells that overexpress MT-3 were not growth inhibited. Stable transfection of the MT-1E gene had no effect on the growth of any of the 4 cell lines. It was also demonstrated that the overexpression of both MT-3 and MT-1E only increased the resistance of MCF-7 cells to Cd+2. In all instances, stable transfection of the MT-3 or MT-1E gene had no effect on the expression of the other MT isoforms. The study shows that MT-3 can influence the growth of some breast cancer cell lines.

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