Tocotrienols Modulate Breast Cancer Secretomes and Affect Cancer-Signaling Pathways in MDA-MB-231 Cells: A Label-Free Quantitative Proteomic Analysis

Abstract

Tocotrienols (T3), a family of vitamin E, are reported to possess potent anti-cancer effects but the molecular mechanisms behind these effects still remain unclear. The aim of this study was to investigate how T3 exert anti-cancer effects on MDA-MB-231 human breast cancer cells. The MDA-MB-231 cells were chosen for this study as they are triple-negative and highly metastatic cells, which form aggressive tumors in experimental models. The MDA-MB-231 cells were treated with varying concentrations (0–20 µg mL⁻¹) of gamma (γ) or delta (δ) T3 and the secretome profiles of these cells treated with half maximal inhibitory concentration (IC₅₀) of γT3 (5.8 µg mL⁻¹) or δT3 (4.0 µg mL⁻¹) were determined using label-free quantitative proteomic strategy. A total of 103, 174 and 141 proteins were identified with ProteinLynx Global Server (PLGS) score of more than 200 and above 25% sequence coverage in the untreated control and T3-treated cell culture supernatant respectively. A total of 18 proteins were dysregulated between untreated control and T3 (δT3 or γT3) treated conditions. The results showed that T3 treatment downregulated the exogenous Cathepsin D and Serpine1 proteins but upregulated Profilin-1 protein, which play a key role in breast cancer in the MDA-MB-231 cells. These findings strongly suggest that T3 may induce differential expression of secreted proteins involved in the cytoskeletal regulation of RHO GTPase signaling pathway.

Acknowledgment

The authors thank the Malaysian Genomic Institute (MGI) for providing the proteomics facilities and services and DAVOS Pvt Lmt (Singapore) for providing T3 isoforms (γT3 and δT3).

Disclosure Statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported with research grants from the Fundamental Research Grant Scheme (FRGS, FP016–2013B) from the Ministry of Higher Education, Malaysia, the Postgraduate Research Grant (PPP, PG201–2015B) and Frontier Research Grant UM (FRG, FG018–17AFR) from University Malaya, Malaysia.