Identification of 14-3-3σ as a Contributor to Drug Resistance in Human Breast Cancer Cells Using Functional Proteomic Analysis

Abstract

Multidrug resistance (MDR) is a major obstacle to successful cancer treatment. To understand the mechanism of MDR, many cancer cell lines have been established, and various mechanisms of resistance, such as ATP-binding cassette (ABC) transporter-mediated drug efflux, have been discovered. Previously, a MDR cell line MCF7/AdVp3000 was selected from breast cancer cell line MCF7 against Adriamycin, and overexpression of ABCG2 was thought to cause MDR in this derivative cell line. However, ectopic overexpression of ABCG2 in MCF7 cells could not explain the extremely high drug resistance level of the selected MCF7/AdVp3000 cells. We hypothesized that MCF7/AdVp3000 cells must have other resistance mechanisms selected by Adriamycin. To test this hypothesis, we compared the global protein profiles between MCF7 and MCF7/AdVp3000 cells. Following two-dimensional gel electrophoresis and matrix-assisted laser desorption/ ionization-time of flight mass spectrometry analysis, 17 protein spots with differential levels between the two cell lines were identified. Although 14-3-3S, keratin 18, keratin 19, ATP synthase B, protein disulfide isomerase, heat shock protein 27, cathepsin D, triose-phosphate isomerase, peroxiredoxin 6, and electron transfer flavoprotein were increased, nm23/H1, peroxiredoxin 2, nucleophosmin 1/B23, and inorganic pyrophosphatase were decreased in MCF7/AdVp3000 cells. The differential levels of these proteins were validated using Western blot. Furthermore, functional validation showed that the elevated 14-3-3S expression contributes considerably to the observed drug resistance in MCF7/AdVp3000 cells. We, thus, conclude that these proteins likely contribute to the resistance selected in the MCF7/AdVp3000 cells, and their altered expression in tumors may cause clinical resistance to chemotherapy. (Cancer Res 2006; 66(6): 3248-55)

Regulation of 14-3-3σ expression in human thyroid carcinoma is epigenetically regulated by aberrant cytosine methylation

“…Similar findings have been reported for colorectal [19] and pancreatic cancers [35] and it has been postulated that 14-3-3σ over expression may be responsible for promoting proliferation and/or preventing apoptotic signal transduction [18]. Elevated 14-3-3σ expression has been reported as contributing to drug resistance in breast cancer cell lines [36], and its increased expression in the anaplastic cancer cell lines in the current study, may be able to explain, at least in part, the widespread resistance to chemo-therapeutic agents noted in this aggressive malignancy [37].…”

Treatment of colon cancer cells using the cytosine deaminase/5-fluorocytosine suicide system induces apoptosis, modulation of the proteome, and Hsp90β phosphorylation

“…14-3-3 proteins control cell cycle, cell growth, survival, and apoptosis (38,39). In addition, 14-3-3j has been identified as a marker of potential clinical interest for breast cancer detection and contributes to drug resistance in human breast cancer cells (40). We also observed that two chaperones, Hsp60 and Hsp90h, which are heat shock proteins (37), are upregulated and subject to posttranslational modification, respectively.…”

Proteomic studies in breast cancer (Review)

“…Breast cancer cell lines with high PIK3CA-GS were confirmed to be resistant to rapamycin (69). (70) demonstrated that cell lines of human cancer which increased expression of 14-3-3σ contributed to drug resistance, suggesting that such a change is associated with clinical resistance to chemotherapy. In treatments stimulating apoptosis, ubiquitin and S100-A6 decreased in the lysates of breast cancer cell lines, and aberrant expression of the two proteins in breast cancer tissue was found (71).…”