Document Type

Thesis

Date of Award

5-2024

School/College

College of Science, Engineering, and Technology (COSET)

Degree Name

MS in Biology

Committee Chairperson

Erica Cassimere

Committee Member 1

Mario Hollomon

Committee Member 2

Hector Miranda

Committee Member 3

Tuan Phan

Keywords

Autophagy, Breast cancer, Metastatic, Simvastatin, Trypan blue, Western blot

Abstract

Breast cancer remains one of the leading causes of cancer deaths among women. Due to the limited effectiveness of current anticancer drugs, ongoing research has extended towards alternative drug categories for potential treatments. Recent findings indicate that statins possess the ability to suppress tumors across various cell types. Traditionally, statins are known as a class of cholesterol-lowering agents and function by inhibiting 3-hydroxy-3-methyl-glutaryl-coenzyme A reductase, a key enzyme in the mevalonate pathway. However, statins can also suppress cell proliferation and ultimately lead to cell death, which includes Type I apoptosis-induced cell death or Type II autophagy-induced cell death. Autophagy is a vital physiological cellular process that facilitates the intracellular degradation and removal of misfolded proteins and damaged organelles. Initially, autophagy was considered a pro-survival process, however, other reports have shown that improper balance of autophagic pathways can also exert pro-death pathways. One type of statin, simvastatin, has been shown to induce autophagy in prostate cancer cells. However, its effects on other tumors remain poorly understood. In this study, we hypothesize that simvastatin induces autophagy-mediated cell death in breast cancer cells. We used two metastatic breast cancer cell lines as a model for tumors which typically exert resistance to anticancer treatments. Cells were treated with simvastatin at various concentrations up to 48 hr. Cell morphology was examined microscopically, and induction of autophagy was measured using Western blotting. Following treatment with simvastatin, we observed increased rounding of cells in both MDA-MB-231 and MDA-MB-468 cells. Moreover, increase in protein expression of a classic autophagy marker, LC3-II, was markedly enhanced following a dose response treatment of simvastatin. To determine if the rounded cells were indicative of cell death, we performed a Trypan blue exclusion assay. Cell death was dramatically increased in a dose-dependent manner following simvastatin treatment, particularly at 48 hr. Moreover, we co-treated cells with simvastatin and chloroquine, an agent which blocks autophagy, and observed that cell death was reduced as compared to simvastatin alone, suggesting that autophagy contributed to cell death. These results demonstrate that simvastatin suppresses cell proliferation through induction of autophagy in breast cancer cells. Therefore, simvastatin may serve as an attractive anticancer agent to target advanced breast tumors.

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